Patent Application
20240419066
The present application claims the priority of German patent application 102023205568.6, which was filed on 14 Jun. 2023. The entire disclosure of that earlier application is hereby incorporated by reference in the present application.
The techniques disclosed herein relate to a method for incorporating temperature-regulating hollow structures into a substrate, in particular into a substrate for an optical element, in particular for a mirror for an EUV projection exposure apparatus, comprising the following steps:
Moreover, the disclosed techniques relate to a method for producing an optical element, in particular for producing a mirror for an EUV projection exposure apparatus.
Furthermore, the disclosed techniques relate to a substrate for producing an optical element, in particular for producing a mirror for an EUV projection exposure apparatus, wherein the substrate has temperature-regulating hollow structures, and also an optical element, in particular a mirror for an EUV projection exposure apparatus comprising a substrate.
The disclosed techniques further relate to a processing system for incorporating temperature-regulating hollow structures into a substrate, in particular into a substrate for a mirror for an EUV projection exposure apparatus, comprising
In addition, the disclosed techniques relate to an apparatus pertaining to semiconductor technology and to a structured electronic component.
The following description of the disclosed techniques is given on the basis of an optical element in the form of a mirror and the use thereof in an EUV projection exposure apparatus, wherein heat is dissipated from the mirror by a temperature-regulating fluid in the form of a cooling fluid being caused to flow through the temperature-regulating hollow structures present in said mirror.
In principle, however, the following explanations apply generally to optical elements which can be assigned a substrate composed of a substrate material into which temperature-regulating hollow structures are incorporated, through which a temperature-regulating fluid can be caused to flow for temperature compensation during operation of the optical element.
In particular, optical elements are used in apparatuses pertaining to semiconductor technology in which an object is irradiated with a working radiation with the aid of one or more optical elements. Besides an EUV projection exposure apparatus, such apparatuses for semiconductor technology include, in particular, mask inspection apparatuses and wafer inspection apparatuses.
On the one hand, temperature regulation can be cooling or heating of the optical element or of at least one region of the optical element. That is to say that, with the aid of the temperature-regulating fluid, the optical element as a whole or at least in a volume region is brought to a temperature which it was not at previously.
On the other hand, however, temperature regulation can also have the effect that a specific temperature or a specific temperature range of the optical element or of at least one region of the optical element is or stays maintained.
These considerations furthermore generally apply to components comprising a corresponding substrate which carries or can carry one or more functional units and into which temperature-regulating hollow structures are incorporated, through which a temperature-regulating fluid can be caused to flow for temperature regulation during operation of the component. Such a component can provide a sensor device, for example; in this case, the substrate carries sensor units as functional units.
Microlithographic projection exposure apparatuses are used in chipmaking for the production of microstructured and nanostructured circuits in order to transfer structures on a mask to a photoresist that has previously been applied to a wafer. For this purpose, the mask is illuminated with light and imaged onto the light-sensitive layer in a reduced size. In EUV projection exposure apparatuses, the light has a wavelength of between approximately 5 nm and approximately 30 nm; the apparatuses commercially available at the present time use light having a wavelength of 13.5 nm.
However, there are no optical materials which have a sufficiently high transmissivity for such short wavelengths. Therefore, in EUV projection exposure apparatuses, the lens elements that have been customary at longer wavelengths are replaced by mirrors and the mask, too, thus contains a pattern of reflective structures.
The provision of mirrors for EUV projection exposure apparatuses is technologically demanding. The substrate consists of a substrate material, which is generally glass, e.g. titanium-doped quartz glass such as ULE®, or a glass ceramic. Suitable glass ceramics are offered under the trade names Clearceram® or Zerodur® and have the property of having a very low coefficient of thermal expansion at the operating temperature of the mirror.
A coating which reflects the EUV light and consists of a multiplicity of thin double layers having alternating refractive indices is applied to the substrate.
Even with such complexly constructed coatings, however, the reflectivity of the mirrors for the EUV light is rarely more than 70%, and even this is only for light which impinges on the reflective coating with normal incidence or with angles of incidence of a few degrees. The portion of the EUV light which is not reflected by the coating is absorbed in the substrate, where it leads to considerable heating since the EUV light sources used are very powerful. Even if glass ceramics having low coefficients of thermal expansion are used, the heating may lead to unacceptable changes in shape of the mirrors.
It has therefore been proposed to provide the substrates with temperature-regulating hollow structures, which in this case are cooling hollow structures, wherein in particular temperature-regulating channels in the form of cooling channels are provided, through which water or some other temperature-regulating fluid, i.e. here a cooling fluid, flows during operation and dissipates heat in this way. Such temperature-regulating channels may have small cross-sectional diameters of the order of magnitude of only approximately 1 mm2 and ideally run closely below the reflective coating.
An overview of the hitherto known methods for producing temperature-regulating channels is contained in the application DE 10 2021 214 310.5, the disclosure of which is hereby incorporated in its entirety. In one advantageous method, by way of example, an ablation light beam is progressively focused on ablation locations at which temperature-regulating channels are intended to arise and the substrate material is ablated by the ablation light beam.
In one variant of this method, ablated substrate material is rinsed away by a rinsing fluid. In that case, a temperature-regulating channel is incorporated into the substrate material proceeding from the surface of the substrate, such that a temperature-regulating channel section that lengthens in the course of the process progressively forms until the desired temperature-regulating channel has been fully incorporated. In general, the externally accessible temperature-regulating channel section is used as a connecting path for the rinsing fluid toward and away from the processing locations.
When flowing through such a temperature-regulating hollow structure, the temperature-regulating fluid or cooling fluid may induce so-called FIVs (“flow induced vibrations”), i.e. vibrations of the mirror during operation, the influence of which ought to be minimized.
It has been found that the effectiveness of the temperature regulation of the substrate and the heat transfer between the substrate and a temperature-regulating fluid flowing through a temperature-regulating hollow structure is determined by many factors, which are in turn influenced by the course, the formation and the surface properties of the temperature-regulating hollow structures. A rapid reaction to changed parameters or else to new insights is desirable when producing the temperature-regulating hollow structures.
Therefore, an object of the disclosed techniques is to specify the abovementioned methods, a substrate, an optical element, a processing system and an apparatus pertaining to semiconductor technology of the type mentioned in the introduction which take account of these concepts and in particular provide possibilities for flexibly counteracting the FIVs in a substrate. Temperature-regulating hollow structures are intended to be introduced into the substrate with high precision and quality and with good process speed and process effectiveness.
In the case of a method of the type mentioned in the introduction, this object is achieved by virtue of the fact that:
Such a set-up of a scanning trajectory makes possible high flexibility in the programming of a control device used to predefine a corresponding scanning trajectory. In particular, relatively long sections of the scanning trajectory can stay predefined by predefined scanning patterns and just their sequence and position within the substrate can be reconfigured and the control commands to that end can be recalculated.
In different scanning positions, different scanning patterns or else identical scanning patterns can be scanned, individual or all scanning patterns of which can then also be implemented repeatedly.
Details concerning the advantages and effects and also concerning applications of the features explained below will become apparent from the description of the exemplary embodiments.
A finer resolution of the scanning trajectory and the adaptation thereof to desired formations of the temperature-regulating hollow structure are possible in any case if a scanning pattern defines a number of one or a plurality of hatch lines along which the ablation focus is guided in a scanning direction from a beginning to an end of a respective hatch line, wherein given a number of a plurality of hatch lines a hatch jump path comprised by the scanning trajectory is in each case defined between the end of a first hatch line and the beginning of a second hatch line, wherein:
It can be advantageous if a pattern jump path in each case runs between the end of a hatch line of a scanning pattern in a first scanning position and the beginning of a hatch line of a scanning pattern in a second scanning position and:
If step (G5) is carried out, this is preferably effected in such a way that
In this case, if each end of each hatch line of the intermediate scanning pattern is the beginning of a pattern jump path, advantageously after each scanned hatch line scanning in a different scanning position can take place.
The scanning of a scanning pattern results in a slice being ablated in an ablation direction ad, with the advantageous alternatives that:
Here it is preferred that:
If step (G3)(a) is carried out, preferably the hatch lines of the sector with a larger hatch distance hd are scanned with a processing light beam having a greater pulse energy EP than the pulse energy EP of the processing light beam when scanning a sector with a smaller hatch distance hd.
In this case, it can be advantageous if the hatch lines with larger hatch distances hd, in two successive scanning positions, are scanned in a manner offset relative to one another in a direction transversely with respect to the scanning direction of the hatch lines.
Advantageously, the pulse energy EP of the processing light beam can be set in such a way that the ablation focus is attained in a defocus plane at a distance D above the focus, in which defocus plane the processing light beam has a larger beam diameter than the focus of the processing light beam.
Preferably, the peak pulse power PS of the processing light beam is then less than the pulse power PL of the self-focusing threshold of the processing light beam.
It can be advantageous if the processing light beam is a processing beam operated in a burst mode.
If step (G4) is carried out, a groove scanning pattern can advantageously be scanned twice in the same scanning position and the groove scanning pattern during the second scan can be scanned in a manner rotated, in particular rotated by 90°, relative to the groove scanning pattern of the first scan, such that the hatch lines of the two groove scanning patterns cross one another in the relevant scanning position.
If step (G6) is carried out, it is advantageous if in the case of the contour scanning pattern a groove scanning pattern is scanned in the core region and contour scanning patterns are scanned in a plurality of scanning positions in such a way that lateral webs composed of substrate material are formed.
If step (G6) is carried out, it is advantageous if:
Preferably, the contour hatch lines and the hatch lines in the core region are then spiral hatch lines, such that the contour scanning pattern defines a spiral scanning pattern, in particular a spiral scanning pattern with a continuous spiral hatch line.
Great flexibility in the ablation of ellipses, in particular, can be achieved if the spiral hatch line of the spiral scanning pattern:
If step (G6) is carried out, it is expedient in terms of control engineering and associated with a time gain if a circular hatch line or a spiral hatch line is scanned by polylines and/or microvectors.
Step (G7) is primarily advantageous if in this case the single-hatch scanning patterns are scanned in a helix scanning process in a sequence in which the respective hatch lines in different scanning positions each extend in the radial direction between a longitudinal central axis and an outer screw line of a geometric reference helix screw with a screw flight, such that a screw volume is ablated in the longitudinal direction.
In this case, it is expedient if:
Preferably, one or more pitches (h) of each reference helix screw for a helix scanning process are chosen in such a way that a string full volume is ablated.
If step (G7) is carried out, it is alternatively or supplementarily advantageous if a contour helix scanning process is carried out in such a way that:
Step (G8) is preferably carried out in such a way that partial cross-section scanning patterns are scanned in a partial pattern scanning process in which these are arranged in the scanning positions in such a way that each ablated slice lies on the outside against a screw line of a geometric reference helix screw.
In this case, identical or different partial cross-section scanning patterns can be scanned in each scanning position, wherein the partial cross-section scanning patterns in two successive scanning positions are rotated by a rotation angle γ in the circumferential direction.
A change in the cross-section of the temperature-regulating hollow structure in the longitudinal direction can advantageously be achieved if, in two adjacent scanning positions, scanning patterns that are scanned are such that the slice in the second scanning position has at least regionally a larger radial extent than the slice in the first scanning position, wherein the deepest marginal line of the temperature-regulating hollow structure remains in the same xy-plane of the coordinate system.
In order to be able to flexibly follow the course of the temperature-regulating hollow structures to be produced, it is expedient if slices are ablated which are tilted by a pitch angle α relative to the yz-plane of the coordinate system which is anchored in a rotationally fixed manner with the substrate, wherein there are at least two slices which are ablated with different pitch angles α.
In this case, the pitch angle α of a slice is preferably selected depending on the angle formed between the longitudinal direction of the temperature-regulating hollow structure to be produced and the yz-plane of the coordinate system which is anchored in a rotationally fixed manner with the substrate.
In the case of a method for producing an optical element, the object mentioned above is achieved by virtue of the fact that temperature-regulating hollow structures are incorporated into the substrate in accordance with the method explained above and further processing comprises one or more steps of chemical and/or physical processing of at least one surface of the substrate and also producing or applying a coating on the substrate, which coating is configured at least to reflect at least 50% of EUV light impinging with normal or almost normal incidence.
The object mentioned above is achieved by a substrate of the type mentioned in the introduction which comprises temperature-regulating hollow structures incorporated in accordance with the method.
The abovementioned FIVs, in particular, can be counteracted if, in the case of the substrate, at least one temperature-regulating hollow structure defines an internal lateral surface which is formed at least regionally by a periodic structure with a radial shaping and/or is formed at least regionally by a roughness structure having a mean roughness Ra in accordance with DIN EN ISO 25178, version as at June 2023, of between 10.0 μm and 5.0 μm, which in particular is between 10.0 μm and 6.5 μm, between 10.0 μm and 8.0 μm, between 8.5 μm and 5.0 μm, between 7.0 μm and 5.0 μm or between 8.5 μm and 6.5 μm, or having a mean roughness Ra of 5.0 μm and less, which in particular is between 5.0 μm and 0.1 μm, preferably between 4.5 μm and 0.125 μm, between 4.0 μm and 0.15 μm, between 3.5 μm and 0.175 μm or between 3.0 μm and 0.2 μm.
Advantageously, the periodic structure is formed in such a way that, upon a projection of successive cross-sections of a section of the temperature-regulating hollow structure into an image plane, said periodic structure defines a contour line of the internal lateral surface which has a periodic course of recurring structural elements at least in a section in the circumferential direction. Alternatively or supplementarily, the roughness structure is formed in such a way that it extends out along the full circumference in the circumferential direction at least in a section in the longitudinal direction of the temperature-regulating hollow structure.
Different kinds of structural elements which occur periodically in the circumferential direction can be formed in this case. These structural elements can also be superimposed.
It is advantageous if the periodic structure is formed in the form of a rib structure with ribs as structural elements, which extends in the longitudinal direction of the temperature-regulating hollow structure and has a radial shaping.
In this case, the ribs of the rib structure preferably in the circumferential direction are at a distance of the order of magnitude of 0.5 to 1.5 times the distance between two adjacent hatch lines (66), in particular between 10 μm and 30 μm, with preference between 15 μm and 25 μm and preferably approximately 20 μm, and radially have a shaping with a ratio of 1:100 to 1:7 relative to the average diameter at a cross-section of the temperature-regulating hollow structure. In the case of a temperature-regulating channel having an exemplary diameter of 2 mm, the radial shaping thus lies in a cross-section of between 20 μm and approximately 285 μm.
An even more advantageous flow behavior of a temperature-regulating fluid can be achieved if the periodic structure, in particular in the form of the rib structure, is formed in a first region of the internal lateral surface of the temperature-regulating hollow structure and the internal lateral surface of the temperature-regulating hollow structure, in a second region, is formed by a structure which is different than the periodic structure and which has a more uniform area with smaller shaping in the radial direction than the periodic structure.
It is particularly advantageous if the first region and the second region are arranged on opposite sides of the temperature-regulating hollow structure.
FIVs can likewise be reduced if the temperature-regulating hollow structure, in particular periodically, repeatedly widens and narrows in the longitudinal direction.
In this case, the cross-sections of the temperature-regulating hollow structure in the repeatedly widening section can be asymmetrical with respect to the longitudinal central axis of the temperature-regulating hollow structure.
What has proved to be particularly advantageous is a flow surface with periodically occurring elevations and depressions which is formed in such a way that the internal lateral surface of the temperature-regulating hollow structure, in longitudinal sections through the longitudinal central axis, follows a wavy line at least on one side, wherein there is in particular at least one longitudinal section through the longitudinal central axis in which the internal lateral surface of the temperature-regulating hollow structure follows a wavy line on one side and a straight line on the other side.
What can be advantageous in respect of the heat transfer and optionally the heat dissipation is if the temperature-regulating hollow structure has recesses which are spaced apart from one another in the longitudinal direction and which have at least one height h at which vortex flows of a temperature-regulating fluid flowing through the temperature-regulating hollow structures occur, in which the temperature-regulating fluid circulates at least at times.
Alternatively or supplementarily, flow structures which reduce the frictional resistance vis-à-vis a flowing liquid temperature-regulating fluid can be formed on the internal lateral surface of the temperature-regulating hollow structure.
Particularly advantageously, the flow structures are riblet structures with ribs formed in the longitudinal direction.
The riblet structures can preferably correspond to the surface of a scale structure composed of a multiplicity of individual scales with ribs.
In the case of an optical element of the type mentioned in the introduction, the object specified above is achieved if the substrate is a substrate having some or all of the features described above.
The substrate can be used particularly effectively if the optical element is a mirror for an EUV projection exposure apparatus, and the substrate has a carrier surface bearing a coating configured at least to reflect at least 50% of EUV light impinging with normal or almost normal incidence.
In the case of the processing system mentioned in the introduction, the object specified above is achieved by virtue of the fact that the processing system is configured in such a way that it controls the focusing device in the manner such that the method specified above for incorporating temperature-regulating hollow structures into a substrate is carried out.
In particular, for this purpose, the control device is programmed in such a way that the method steps are carried out.
In the case of an apparatus pertaining to semiconductor technology, the object is achieved by such an optical element.
This is particularly advantageous in the case of an EUV projection exposure apparatus.
Exemplary embodiments of the disclosed techniques are explained in greater detail below with reference to the drawings. In these drawings:
intermediate scanning positions with scanning patterns;
In
The optical element 8 and thus the mirror 10 comprises a substrate 12 composed of a substrate material 12a, which is therefore a mirror substrate in the case of the present exemplary embodiment of the mirror 10. Such a mirror substrate is in practice a glass ceramic, in particular.
The substrate 12 is monolithic in the case of the present exemplary embodiment, which is also the preferred embodiment. In modifications not shown separately, however, the substrate 12 can also be joined together from partial segments. In principle, additive manufacturing methods are suitable in this case. By way of example, 3D printing methods are also appropriate just like laser welding methods or techniques for the thermal bonding of workpieces.
In the case of the mirror 10, the substrate 12 has a precisely processed surface 14, the curvature of which determines the optical properties of the mirror 10. The surface 14 of the substrate 12 serves as a carrier surface and will also be referred to thus hereinafter. The carrier surface 14 bears a coating 16 ensuring the optical properties of the optical element 8. In the case of the mirror 10 shown here, the coating 16 is configured in such a way that it predominantly reflects incident EUV light 18. As is illustrated in the enlarged detail A, in the case of the present exemplary embodiment, this coating 16 is embodied in multilayer fashion and is constructed in particular from a plurality of double layers 20 which were applied to the carrier surface 14. The coating 16 has a reflection coefficient of at least 50%, preferably of more than 72%, for normal-incidence EUV light 18. The reflectance achieved during operation depends on the angle of incidence of the EUV light 18.
Besides the double layers 20, the coating 16 can comprise further layers, too, which do not contribute to reflection, but optionally to stabilization and/or to protection of the coating 16 or of the optical element 8 or the mirror 10. By way of example, protection against components of a hydrogen plasma can be established by such structures. Such further layers can be provided between the double layers 20 within the coating 16, between the double layers 20 and the carrier surface 14 and/or on the side of the double layers 20 that is remote from the carrier surface 14.
In the case of an optical element 8, the coating 16 can also be formed by the outer surface of the substrate 12 being modified by processing and/or treatment. In this case, the coating 16 is therefore not a separately applied coating, but rather defines a layer of the substrate 12 as such; the underlying surface as a transition to the substrate material 12a is then the carrier surface 14.
In the case of the mirror 10 explained here and the application of EUV light 18, the unreflected portion enters the substrate 12 and is absorbed there, specifically predominantly in the vicinity of the carrier surface 14. Owing to this absorption, the substrate 12 heats up primarily in the vicinity of the regions of the carrier surface 14 which are exposed to the EUV light 18. Since the coefficient of thermal expansion of the substrate material 12a is not equal to zero and in addition is itself temperature-dependent, the heating up can give rise to changes in shape of the substrate 12 which affect the optical properties of the mirror 10. In relation to optical elements 8, put generally, temperature changes in the substrate 12 can affect the optical properties of the optical element 8.
On account of the extremely tight specifications in EUV projection exposure apparatuses, however, changes in the optical properties of the mirrors therein are unacceptable or acceptable at most to a negligible extent. However, also on a general level again the optical properties are intended to remain stable in the case of optical elements 8 and the functionality is intended to be maintained in the case of components.
In order to minimize temperature fluctuations in the substrate material 12a and associated changes in shape of the substrate 12, a plurality of temperature-regulating hollow structures 22 are incorporated into the substrate 12.
During the operation of the EUV projection exposure apparatus, a temperature-regulating fluid in the form of a cooling fluid 24 is caused to flow through these temperature-regulating hollow structures 22, cooling water being used in practice; however, other cooling liquids and cooling media are also possible.
The cooling fluid 24 absorbs the quantity of heat input by the EUV light 18 and dissipates it from the substrate 12. For this purpose, the temperature-regulating hollow structures 22 are connected to a cooling unit 26 and a pump unit 28 of a cooling system, designated in its entirety by 30. The pump unit 28 sucks up the cooling fluid 24 from the temperature-regulating hollow structures 22 and guides it via a return line 32 to the cooling unit 26. There the cooling fluid 24 is cooled down to its target temperature before it flows through the temperature-regulating hollow structures 22 once again. This circuit is illustrated by corresponding arrows in
The temperature-regulating hollow structures 22 typically run in the vicinity of the carrier surface 14 and at least regionally parallel thereto.
In the case of the exemplary embodiments described here, the temperature-regulating hollow structures 22 are formed as temperature-regulating channels 34, of which three temperature-regulating channels 34.1, 34.2 and 34.3 are illustrated. The temperature-regulating channels 34 each extend between two openings 36, which are designated only for the temperature-regulating channel 34.1 in
In the case of modifications not shown separately, the temperature-regulating hollow structures 22 can also be more extensive chambers in which the cooling fluid 24 is exchanged only slowly and in which no longitudinal axis is defined, as is characteristic of a channel.
Moreover, the arrangement of the temperature-regulating channels 34 illustrated in the figures is merely by way of example and can be different in real systems; the number of temperature-regulating channels 34 can also be larger or smaller. By way of example, the openings 36 can also be arranged at the lateral flanks of the substrate 12 or provision can be made of at least one temperature-regulating channel 34 which runs meanderingly or spirally through the substrate 12 or a part thereof.
In a further modification, it is also possible for one or more temperature-regulating channels 34 to extend proceed from a distribution section or a distribution chamber in the substrate 12; such temperature-regulating channels 34, with their openings 36, at one end or at both ends, then join such a distribution section or distribution chamber, from which the temperature-regulating channels 34 are then supplied with the temperature-regulating fluid. The distribution section or the distribution chamber and optionally that end of a temperature-regulating channel 34 which is remote therefrom are then correspondingly connected to the cooling system 30.
During the production of an optical element 8 by way of applying the method described here for producing temperature-regulating hollow structures 22, various stages of the substrate 12 are defined.
A first stage of the substrate 12 defines a kind of raw substrate 12′, which is still largely unprocessed and untreated and in which a carrier surface 14 has not yet been formed structurally. In the case of the substrate 12 explained above, which is a mirror substrate, such a raw substrate is for example a glass parallelepiped composed of glass ceramic.
A second stage of the substrate 12 defines a carrier substrate 12″, in which the carrier surface 14 is produced and formed. This may necessitate a plurality of chemical and/or physical work steps which may comprise processes such as grinding, turning, polishing and/or etching.
A third stage of the substrate 12 then defines an element substrate 12′″, in which the carrier surface 14 is provided at least with the coating 16 determining the optical properties. If the resulting optical element is a mirror, the element substrate 12+″ is thus terminologically a mirror substrate. Accordingly, the substrate 12 in
The production of the temperature-regulating hollow structures 22 in the substrate 12 described below can take place, in principle, in any stage of the substrate 12. In general, this takes place in the stage of the raw substrate 12′, but can also be carried out for example in the stage of the carrier substrate 12″ or even in the stage of the element substrate 12′″.
In the present case, the production of the temperature-regulating hollow structures 22 is explained in particular on the basis of the example of the carrier substrate 12″ in order to illustrate the function envisaged in the present exemplary embodiment for the mirror 10 obtained later.
The substrate 12 is illustrated both as raw substrate 12′ and as carrier substrate 12″. In this case, the carrier substrate 12″ is shown with the aid of solid contour lines. That part of the substrate material 12a of the raw substrate 12′ which is removed in later processing steps is delimited by dashed contour lines, such that the solid and dashed contour lines taken as a whole illustrate the raw substrate 12′. Hereinafter, reference is made just generally to the substrate 12.
In general, the ablation of substrate material 12a is begun at the location of one of the openings 36. This is illustrated on the basis of the example of the temperature-regulating channel 34.1, of which a section of a temperature-regulating hollow structure 22 that has already been incorporated into the substrate 12, and here specifically a temperature-regulating channel section 42, is present, which extends into the substrate 12 proceeding from that opening 36 which forms the outlet to the pump unit 28 in the case of the configuration shown in
The processing system 40 comprises a light source 44, which generates a processing light beam, which is a laser beam 46 in all the exemplary embodiments explained here. However, all explanations in respect thereof are analogously applicable, mutatis mutandis, to other suitable processing light beams. The light source 44 is thus preferably a powerful laser that generates ultrashort pulses. These can be pulses in the femto-, pico- or nanoseconds range. In this case, the processing system 40 realizes a laser ablation system such as is implemented in the present exemplary embodiments.
The substrate 12 intrinsically defines a reference coordinate system which is anchored in a rotationally fixed manner with the substrate 12, such that the coordinate system concomitantly moves with the substrate 12 in space, and defines the positive z-direction thereof upward, the positive x-direction thereof toward the right, and the positive y-direction thereof forward. The direction indications downward, toward the left and backward indicate the respectively opposite direction. A vertical in relation to the substrate 12 thus extends in the z-direction, and a horizontal in relation to the substrate 12 lies in an xy-plane.
The coordinate system is expediently assigned to the substrate 12 after it has been positioned in an initial position in the processing system 40. Taking this reference coordinate system into account, the processing system 40 is thus arranged above the substrate 12. That side of the temperature-regulating hollow structure 22 which is reached first by the laser beam 46 thus defines the top side of said structure and the direction upward. In the present case, the positive z-direction points in the direction from the rear side 38 of the substrate 12 to the carrier surface 14, which still needs to be formed in the case of the raw substrate 12′.
The laser beam 46 or the focus 48 thereof can be directed at various ablation locations 56 in the substrate 12 with the aid of a focusing device 50, which is shown schematically by a scanning device 52 comprising a mirror 52a and a focusing lens element 54. The focus 48 in each case represents a processing light pulse with this focus 48. Moreover, it is assumed schematically that the focus area AF of the focus 48 corresponds to the irradiated area. When mention is made hereinafter of the beam diameter of the laser beam 46, this is taken to mean the diameter of the focus 48 or of the focus area AF.
The relative arrangement between the substrate 12 and the processing system 40 can alternatively or supplementarily be changed with the aid of a movement system (not illustrated), which is likewise assigned to the focusing device 50, in such a way that the laser beam 46 can be directed at any location of the substrate 12 after passing through the focusing lens element 54. In the case of small substrates 12, movement processes can be dispensed with, provided that the scanning device 52 covers a sufficiently large region.
The scanning device 52, the focusing lens element 54 and a movement system—optionally present—of the focusing device 50 are controlled by a control device 58 in such a way that the laser beam 46 is progressively focused on all ablation locations 56 of the substrate 12 at which temperature-regulating channels 34 are intended to arise.
At the respective focus 48, the intensity of the laser beam 46 is high enough that the substrate material 12a of the substrate 12 is ablated. Put generally, the laser beam 46 defines an ablation focus 48A, at which the laser beam 46 inputs energy with an energy density H, i.e. its fluence, into the substrate material 12a, which is high enough that the substrate material 12a is modified or ablated. In the case of the configuration described here, this ablation focus 48A is the focus 48.
In this case, the region in which the laser beam 46 ablates material outlines a respective ablation location 56, which by its nature moves concomitantly with the focus 48 of the laser beam 46. The foci 48 and thus the ablation location 56 determine where a temperature-regulating channel 34 arises in the substrate 12.
As can be discerned with reference to
The longitudinal direction 60 of a temperature-regulating hollow structure 22 is not a rigid direction, but rather is defined in each case at a midpoint of a considered cross-section of the temperature-regulating hollow structure 22 taking account of the preceding and the succeeding course of the temperature-regulating hollow structure 22, which is indicated by a dotted line. The longitudinal direction 60 is shown by way of example at three points in
The slices 62 are tilted by a pitch angle α relative to the yz-plane. If, as is shown here by way of example, a temperature-regulating channel 34 with a circular cross-section can be produced, the contour of a slice 62 thus describes an ellipse. The pitch angle α is preferably 45°, but other pitch angles are also possible. In addition, the pitch angles α can differ from slice to slice.
In this way, it is possible that, via successive ablation of slices 62, the substrate material 12a can be ablated with a uniform cross-section in a vertical and/or horizontal direction.
The ablation processing system 40 additionally comprises a rinsing device (not shown separately) used to apply a rinsing fluid to the ablation locations 56 while the substrate material 12a is being ablated. The ablated material is transported away from the ablation location 56 by the rinsing fluid. For this purpose, a rinsing line is inserted into the already formed temperature-regulating channel section 42, the delivery end of which is tracked to the ablation locations 56. In general, during the ablation of the substrate material 12a, the already formed temperature-regulating channel section 42 always has the rinsing fluid flowing through it and is thus filled.
As explained in the introduction, the substrate material 12a is modified or ablated at the ablation locations 56. A substrate material which is modified rather than directly ablated by the processing light beam 46 has, relative to the substrate material 12a, an increased susceptibility to a chemically active treatment medium. If such a modified substrate material arises, the method described here is supported in that during or after the performance of the scanning process, a chemically active treatment medium is guided to the modified substrate material and chemically removes the modified substrate material. In particular, the chemically active treatment medium is an etchant, such that the modified substrate material 12a is etched away. However, chemical active treatment media having an oxidative or reductive action can also be used.
The ablation processing system 40 comprises corresponding devices for this purpose, although these are not shown separately for the sake of clarity.
Hereinafter the disclosed techniques are also explained further always on the basis of the example of the production of temperature-regulating hollow structure 22 in the form of temperature-regulating channels 34 with a circular cross-section. However, the cross-section of the temperature-regulating hollow structures 22 only depends on the outer contour of the slices 62. Adjacent slices 62 can also have different outer contours, which leads to cross-sections which change in the longitudinal direction 60.
In order then to remove substrate material 12a as such a slice 62, the focus 48 of the laser beam 46 is moved through the substrate 12 following the predefinition of scanning patterns 64, which will firstly be explained generally with reference to
Scanning patterns 64 are illustrated in two ways in the figures. Firstly, perspective views are shown which each correspond to the orientation of the slices 62 in the substrate 12, the elliptical contour of the slices 62 also being shown in each case. Secondly, there are projection views which correspond to a projection of the scanning pattern 64 into a yz-plane of the substrate 12 with a view in the negative x-direction and in which the scanning patterns 64 correspondingly describe a circular contour.
All of the scanning patterns 64 described below are described as scanning patterns as such which are scanned as such. However, all of the scanning patterns 64 described below can also describe only a part of a then superordinate scanning pattern and can correspondingly be scanned as part of the then superordinate scanning pattern.
A scanning pattern 64 defines a pattern scanning path by way of a number of so-called hatch lines 66 along which the focus 48 of the laser beam 46 is guided in a scanning direction from a beginning 66a to an end 66b of the respective hatch line 66. Each hatch line 66 is shown in the respective scanning direction as an arrow pointing from its beginning 66a to its end 66b.
Furthermore, each scanning pattern 64 defines for its part a starting point 64a and a pattern end point 64b for the scanning process for this scanning pattern 64. In this case, the starting point 64a coincides with the beginning 66a of that hatch line 66 of the scanning pattern 64 which is scanned first. The end point 64b of the scanning pattern 64 matches the end 66b of that hatch line 66 of the scanning pattern 64 which is scanned last.
Moreover, a scanning pattern 64 defines hatch jump paths 68 to be bridged between the end 66b of a first hatch line 66 and the beginning 66a of a second hatch line 66, which then define a jump end and respectively a jump beginning of the relevant hatch lines 66. In
In modifications, however, the focus 48 of the laser beam 46 can also be positioned on jump paths and be guided along jump paths.
The hatch lines 66 of a scanning pattern 64 need not be scanned in the adjacent sequence demonstrated by the scanning pattern 64 as implemented in the present exemplary embodiment. That is to say that within a scanning pattern 64 there can also be jumping such that a plurality of hatch lines 66 are situated between the first hatch line 66 with the jump end 66b and the second hatch line 66 with the associated jump beginning 66a.
The hatch lines 66 of a scanning pattern 64 preferably run parallel and the scanning pattern 64 then defines a hatch distance hd.
The hatch lines 66 of the scanning pattern 64 define a scanning area 72, which describes the area extent of the scan. In the present exemplary embodiments, the scanning area 72 is planar and the hatch lines 66 are rectilinear. In modifications that are not shown, the hatch lines 66 can also be curved or have at least curved sections. Depending on the formation and position of the hatch lines 66, a curved scanning area 72 can also arise for a scanning pattern 64. The result in this case is not disk-shaped slices 62, but rather ablation volumes with a correspondingly modified geometry, which however are likewise ablated layer by layer as slices 62. By way of example, the scanning area 72 can be curved in such a way that it follows the lateral surface of a circular cylinder. Resulting slices 62 then have a correspondingly curved geometry.
The scanning positions 74 are spaced apart from one another in the longitudinal direction 60 of the temperature-regulating hollow structure 22 to be produced. The longitudinal direction 60 of the temperature-regulating hollow structure 22 to be produced thus predefines the advance direction of the focusing device 50 relative to the scanning positions 74. The scanning positions 74 are tilted by the pitch angle α relative to the yz-plane, such that the slices 62 are carved with this pitch angle α.
Along a temperature-regulating hollow structure 22 to be produced there are a number of scanning positions 74(n) where n=1 to i, wherein two scanning positions 74(n) and 74(n+1) are adjacent to one another. The number i depends on the length of the temperature-regulating hollow structure 22 and the distance between respective adjacent scanning positions 74(n) and 74(n+1).
The distance between two scanning positions 74(n) and 74(n+1) in each case defines a slice distance sd. The slice distance sd is generally in a range of between 0.5 μm and 1.5 μm. In practice, the slice distance sd is often 0.77 μm. The slice distance sd is generally chosen such that the slices 62 overlap in the longitudinal direction 60, wherein the thickness of a slice 62 depends on the beam diameter. A slice 62 is defined in principle by the volume carved out of solid material and is thus of a theoretical nature if a slice 62 overlaps the region of a preceding slice 62 in which substrate material 12a is already no longer present.
In the present case, the direction in the z-axis of the substrate 12 in which a slice 62 is ablated by the scanning of the scanning pattern 64 in the substrate 12 is referred to as the ablation direction ad.
Generally—and not just in relation to the exemplary embodiment shown here with the scanning pattern 64.1—between a first scanning position 74(n) and a second scanning position 74(m) there are pattern jump paths 76 from a scanning pattern 64 of this first scanning position 74(n) to a scanning pattern 64 of this second scanning position 74(m).
In this case, a pattern jump path 76 proceeds from a jump end 66b of a hatch line 66 of the scanning pattern 64 of the first scanning position 74(n) to a jump beginning 66a of a hatch line 66 of the scanning pattern 64 of the second scanning position 74(m).
In the case of the exemplary embodiment shown here in
Optionally, m=n+2, n+3, . . . n+i can also apply, and these cases involve jumping over correspondingly multiple scanning positions 74. This will be discussed again further below.
If m>n, this means that the jump takes place in the direction of a succeeding scanning position 74 in the scanning process. As will become clear further below, it can also be the case that, depending on the magnitude of n, m=n−1, n−2, . . . , 1. If m<n, this consequently means that the direction of the pattern jump path 76 points in the direction of a preceding scanning position 74 in the scanning process. This will be taken up again further below.
Moreover, in the case of the exemplary embodiment shown here in
The time period required for adjusting the focusing device 50 and optionally the relative position between substrate 12 and processing system 40 for a jump between two scanning positions 74 is referred to in the present case as the pattern jump time pt, the designated abbreviation being derived here from this English term “pattern jump time”. Different pattern jump paths 76 can also lead to different pattern jump times st.
Put generally, for the purpose of incorporating a temperature-regulating hollow structure 22 into the substrate 12, a scanning process is carried out in which the laser beam 46 is guided with the aid of the focusing device 50 in such a way that the ablation focus 48A is moved along a scanning trajectory 78 through the substrate 12. This is referred to in the present case as scanning of the scanning trajectory 78. This involves a relative movement, i.e. the laser beam 46 or the substrate 12a or both is/are moved and controlled.
Once again put generally, this scanning trajectory 78 comprises a plurality of scanning patterns 64 which are scanned in each case in the scanning positions 74. The scanning patterns 64 here each per se define a pattern scanning path by way of associated hatch lines 66 and hatch jump paths 68. The scanning trajectory 78 additionally comprises the pattern jump paths 76 between a scanning pattern 64 of a first scanning position 74(n) and a scanning pattern 64 of a second scanning position 74(m).
In the following figures, the hatch jump paths are not always shown in the illustration of scanning patterns 64.
The application of a meandering scanning pattern in comparison with the application of a complementary line-to-line scanning pattern leads to a time saving of approximately 250 sec for example during the formation of a temperature-regulating channel 34 with a constant diameter of 2 mm over a length of 10 mm.
The application of a meandering scanning pattern 64.2 can take place in the manner as shown in
A further time gain is possible if the scanning positions 74 are also scanned with the aim of a meandering process. This involves scanning the scanning patterns 64 in two scanning positions 74(n) and 74(n+1) in such a way that the ablation direction ad is in opposite directions in these two scanning positions 74(n) and 74(n+1). On the basis of the example of the meandering scanning patterns 64.2,
In this way, the slices 62 are ablated with alternating ablation directions ad alternately from the top downward and from the bottom upward.
A corresponding meandering process is also possible with line-to-line scanning patterns 64.1.
By way of example, during the formation of a temperature-regulating channel 34 with a constant diameter of 2 mm over a length of 10 mm, in relation to the change in the pattern jump paths 76 a time gain of 3 sec is achieved in comparison with the process according to
The temperature-regulating hollow structures 22 each define an internal lateral surface 80, the structural formation of which depends on the completed scanning trajectory 78, inter alia.
The identical orientation results in the formation of a structured internal lateral surface 80 of the temperature-regulating hollow structure, which is stepped in the circumferential direction, which is illustrated schematically on the basis of a stepped structure 82 in
In this case,
As is evident from both
Such stepped structures 82 can promote the effects resulting from FIVs (“flow induced vibrations”) explained in the introduction, which is why it is desirable to obtain the internal lateral surface 80 of a temperature-regulating hollow structure 22 in a more regular form by comparison.
This can be achieved by implementing a rotation process in which the scanning patterns 64 are scanned in two successive scanning positions 74(n) and 74(n+1) in a manner rotated relative to one another by a rotation angle β in the circumferential direction. Such a rotation process is illustrated by
With application of the rotation process, the internal lateral surface 80 of the temperature-regulating hollow structure 22 is formed by a periodic structure 90, which is demonstrated by
This periodic structure 90 of the internal lateral surface 80 of the temperature-regulating hollow structures 22 is formed in such a way that, upon such a projection of successive cross-sections 84 of a section 86 of a temperature-regulating hollow structure 22 into an image plane 88, said periodic structure defines a contour line 92 of the internal lateral surface 80 which has a periodic course of recurring structural elements 94 with a radial shaping in the circumferential direction. In this case, there can be different kinds of structural elements 94, which however each occur periodically in the circumferential direction and optionally can also be superimposed.
Radial shaping should be understood as the extent in the direction of the longitudinal axis of the temperature-regulating hollow structure.
In the longitudinal direction 60, the periodic structure 90 defines a helicity or a helical structure if the rotation of successive scanning patterns 64 is accompanied by the succession of spaced-apart scanning positions 74, which leads to an advance in the scanning direction, i.e. in the longitudinal direction 60.
It is desirable to minimize the process time required for incorporating the temperature-regulating hollow structures 22 into the substrate 12. This can be achieved by various approaches.
Firstly, the rotation process described above additionally has an effect on the intensity distribution of the laser beam 46 and can lead to an increase in the ablation efficiency.
If the slice distance sd is then chosen to be too large, it can happen that no material is ablated in the regions 96. This can result in undesired incoupling effects or defect formation in the scanning process.
By comparison, the rotation process leads to a more homogeneous intensity distribution between the scanning positions 74 in the direction of the longitudinal axis 60 since the regions 96 with lower intensity occur in a manner offset with respect to one another from scanning position 74 to scanning position 74. The risk of defects is reduced as a result.
5.2.1 Increase in the Pulse Energy Ep in Conjunction with Increase in the Energy Density H
In the case of the methods explained hitherto, in a scanning pattern 64 all the hatch lines 66 have the same hatch distance hd and the energy is input at the ablation location 56 with the same energy density H relative to the focus area AF, i.e. with the same pulse energy Ep/focus area AF, wherein the pulse energy Ep in joules [J] is the average power of the light source 44 of the laser beam in watts [W] divided by the repetition rate of the pulses per second [s−1]. The pulse power P results from the quotient of pulse energy EP and pulse duration tP as P=EP/tP.
In the case of the scanning patterns 64 used here, the hatch distance hd between all the hatch lines 66 is the same.
The sector scanning pattern 64.3 shown here takes up by way of example the meandering concept and has three successive sectors 98.1, 98.2 and 98.3, wherein the sectors 98.1 and 98.3 are assigned the same hatch distance hd and the sector 98.2 located therebetween is assigned a hatch distance hd greater by a factor of 3. This can also be understood in such a way that proceeding from a scanning pattern 64 with only identical hatch distances hd in the sector 98.2 only every third hatch line 66 is present and is scanned.
Such a sector scanning pattern 64.3 can be scanned without changing the parameters of the laser beam 46.
The sector scanning pattern 64.3 can be scanned effectively, however, if, during the scanning process, the sector 98.2 is then scanned with a pulse energy EP of the laser beam 46 which is greater than the pulse energy EP of the laser beam 46 during the scanning of the sectors 98.1, 98.3 with a smaller hatch distance hd. As a result, in the sector 98.2 the energy density His increased at the focus 48. This is clarified by the thicker hatch lines 66 in the case of the sector scanning pattern 64.3.
In this way, in the central region of the temperature-regulating hollow structure 22, during the scanning of the sector 98.2 more energy per light pulse is radiated into the volume of the substrate 12 at the focus 48 and the substrate material 12a there is damaged to a greater extent than during the scanning of the sectors 98.1 and 98.3. This substrate material 12a damaged to a greater extent is ablated with subsequently overlapping slices 62 and no damage to the substrate 12 occurs.
During the scanning process, the sector scanning pattern 64.3 can be scanned without change in successive scanning positions 74, which is demonstrated once again by
In addition, optionally the pulse distance pd and/or the slice distance sd can also be increased if the beam diameter is correspondingly enlarged.
Preferably, the parameters for the sector 98.2 are adapted in such a way that the hatch distance hd, the pulse energy EP and also—taking account of the beam diameter—the pulse distance pd and the slice distance sd are increased by the same factor, relative to the parameters of the preceding sector 98.1. However, it is also possible to depart from this.
Since the energy density H at the focus 48 decreases again, however, if the beam diameter becomes larger in conjunction with constant pulse energy EP, it is necessary to coordinate beam diameter and pulse energy EP in such a way as to establish the desired increase in the energy density H.
5.2.2 Increase in the Pulse Energy Ep in Conjunction with Constant Energy Density H
Another approach consists in increasing the pulse energy EP but ensuring that the energy density H of the laser beam 46 remains constant at the ablation location 56.
The ablation focus 48A of the laser beam 46 is enlarged in this case. The pulse energy EP is set in such a way that the intensity of the laser beam 46 that is required for ablation of the substrate material 12a is attained in a defocus plane 100 in which the laser beam 46 has a larger beam diameter than the focus 48. This is illustrated by
The ablation focus 48A is now defined in the defocus plane 100, however.
Clearly, if the pulse energy EP is doubled, the irradiated area must likewise be doubled, which is the case for the defocus plane 100 shown, in which the radius r has increased by the factor √{square root over (2)} relative to the radius at the focus 48. If the pulse energy EP is increased in the sense of being multiplied by a factor x, the defocus plane 100 is defined where the laser beam 46 has a radius r greater by the factor √{square root over (x)} than at the focus 48.
During the scanning process, this defocus plane 100 is then guided along the scanning trajectory 78. In order to coordinate the scanning process with the increased pulse energy EP, it is necessary to adapt the process parameters of pulse distance pd and hatch distance hd for the scanning pattern(s) 64 used and also the slice distance sd between the scanning positions 74. Here as well it is necessary to increase the values in each case by the factor √{square root over (x)}. The scanning process is thus adapted in all three spatial directions.
This means as a result that more volume is ablated from the substrate material 12a in the same time.
As a result of the displacement of the ablation focus 48A, the focus 48 at the beam waist is situated below the ablation location 56, which is supplementarily designated in the defocus plane 100 in
The laser parameters are then coordinated to the effect that, on the one hand, the substrate material 12a above the temperature-regulating hollow structure 22 is not modified and, on the other hand, it is possible to compensate for fluctuations in the scanning process as a result of the defocus distance D between the defocus plane 100 and the focus 48.
The threshold values for the rear-side ablation and modifications of the substrate material 12a in the existing volume depend on the properties of the substrate material 12a and the pulse duration tP and can be defined for a specific pulse duration tP with the aid of the energy density H, i.e. the fluence,
wherein here the peak fluence is described, with the pulse energy EP and the beam radius w at the corresponding axial position, in the present case in the z-direction.
If the threshold energy density/fluence HA for the ablation is then reached in an axial direction, on the one hand a part of the radially outer beam profile of the laser beam passes without obstruction and on the other hand, in the case where particles are transported away with the assistance of fluid, a certain portion of the pulse energy after the ablation, as a result of partial adaptation of the refractive index through the fluid, passes into the non-modified substrate material 12a below the temperature-regulating hollow structure 22 and is still focused.
With regard to the operating parameters of the laser beam 46, it has additionally been recognized that in the case of any change in the pulse energy EP, it may be of significant importance for the peak pulse power PS of the laser beam 46 to be below the pulse power PL of the self-focusing threshold of the laser beam 46.
The self-focusing threshold describes the state in which a diffraction-governed defocusing of the laser beam 46 and the focusing are in equilibrium as a result of the nonlinear optical Kerr effect. For a laser with—as considered here—a transverse Gaussian intensity profile, this limit for the peak power PL is dependent only on the wavelength □0 of the laser used in a vacuum, the linear refractive index no and the nonlinear refractive index n2 and results as
In the case of laser beams 46 with other intensity factors, prefactors with values other than 3.79 determine the self-focusing threshold.
The peak pulse power PS results from the pulse energy P, i.e. the quotient of pulse energy EP and pulse duration tP, and a profile-dependent factor B as
In the case of a laser beam 46 with a Gaussian profile, B is approximately 0.94.
If the peak pulse power PS exceeds the self-focusing threshold, i.e. if PS>PL, the laser beam 46 contracts to below the diffraction limit as a result of the optical Kerr effect, which leads to an extreme intensity boost. This gives rise to a dense plasma which defocuses the laser beam 46. As a result of the optical Kerr effect, however, the beam is focused again after a short propagation distance. By virtue of these two competitive effects, an equilibrium between focusing and defocusing arises below the channel, which ultimately results in a filament 108. Depending on the parameters of the laser pulse and the material properties of the substrate material 12a, such a filament 108 can extend over a plurality of millimeters to centimeters and cause micro-explosions, whereby the enclosed substrate material 12a at the margin of the filament 108 is additionally densified and considerable strain fields are thus produced.
The temperature-regulating hollow structures 22 can therefore be produced in a manner particularly free of strain distinctly below the self-focusing limit if PS<<PL, i.e. if the peak pulse power PS is considerably less than the pulse power PL of the self-focusing threshold.
During the scanning process, in the course of the scanning of the scanning trajectory 78, besides the ablation particles, which are then removed by the rinsing fluid, gas bubbles also arise in the fluid and cause the following laser pulses to be scattered.
Assuming that approximately 50% of the pulse energy EP—with the temporal and spatial pulse shape being maintained-after ablation can effectively incouple into the substrate material 12a below the temperature-regulating hollow structure 22, the maximum energy density/fluence H of the laser beam at the focus 48 must not be greater than the threshold fluence—designated by HV in the present case—for damage in the volume of the substrate material 12a.
By way of example, if the pulse duration tP is reduced in conjunction with constant pulse energy EP, then the laser beam 46 is focused to a greater extent below the ablation location 56 in the substrate material 12a as a result of the Kerr effect and in conjunction with a corresponding pulse duration tP exceeds the threshold fluence HV even below the critical power PL. The threshold fluence HV can likewise be exceeded as a result of an increase in the pulse energy EP.
The material-dependent and laser pulse-dependent difference between HA, i.e. the threshold fluence for the ablation of the substrate material 12a, and HV, i.e. the threshold fluence for volume damage to the substrate material 12a, is of significant importance for avoiding damage in the substrate material 12a present below the temperature-regulating hollow structure 22 to be formed.
At any rate in the optimum case the distance between the ablation location 56 and the focus 48 should not be greater than the Rayleigh length ZR, since otherwise the resulting influence H can exceed the value of Hv as a result of the Kerr effect.
Changing the slice distance sd enables tuning in respect of the magnitude of the portion of the pulse energy EP which is guided to the ablation of the substrate material 12a, and in respect of ensuring that the transverse portion of the beam profile which can penetrate into the underlying substrate material 12a is not too large.
The use of highly absorbent liquids as rinsing fluid makes it possible to increase the absorption in the temperature-regulating hollow structure 22.
In the case of a pulsed laser beam 46 in the form of a laser, pulse rates in the kHz range and optionally in the low MHz range can typically be attained.
A laser with a pulse rate of 400 kHz emits a single pulse with specific pulse energy EP at the interval of 2.5 μs. With lasers which operate in a so-called burst mode, however, this pulse energy EP can also be introduced in each case by individual pulses in a fast pulse train with a temporal distance in the double-digit ns range. Such a fast pulse sequence is referred to as a burst.
If a burst impinges on a material, here the substrate material 12a, the first burst pulse interacts with the material like a single pulse. However, the following burst pulses encounter different boundary conditions; for example, the second pulse in the burst impinges on a cloud of ablation products, with which it then interacts. This can also give rise to material redepositions, such that as a result less material is ablated with a 2-pulse burst than with a single pulse with the pulse energy EP, even though double the energy was introduced. By contrast, a third burst pulse impinges on highly excited substrate material 12a and ablates a very large amount of material.
This is illustrated by
If the ablation direction ad downward is chosen during the formation of the temperature-regulating hollow structures 22, the ablation products propagate with the direction of the laser beam 46. Therefore, in contrast to
The number of pulses in a burst need not then be odd, although typically the odd pulses provide for material ablation and the even pulses provide for material deposition.
Depending on the desired processing depth in the substrate 12 and the available laser energy, the ideal number of pulses in the burst can vary between 2 and 8 or be even greater. As things stand, however, the maximum number dictated by systems engineering is eight burst pulses.
The pulse energy of the individual pulses in a burst can preferably be set with the aid of the control device 52. Various approaches can be pursued here.
Firstly, the pulse energies EP of all the burst pulses can be identical.
However, it is also possible to go through ascending pulse ramps, such as
Alternating variants and combinations of the abovementioned energy ramps are also conceivable, for example pulse no. 1 with EP0, pulse no. 2 with 2EP0, pulse no. 3 with EP0, . . . or for example pulse no. 1 with EP0, pulse no. ½ it ½EP0, pulse no. 3 with 2EP0, pulse no. 4 with ⅓EP0, . . . .
During the ablation of the substrate material 12a by via the laser beam 46, high pressures and temperatures above the melting point of the substrate material 12a occur at the focus 48 at the ablation locations 56. Individual superficial material layers tear off at the ablation front, which is accompanied by a shock wave propagating in all spatial directions.
These shock waves can be used to induce breaking and/or cracking of substrate material 12a in the immediate vicinity of the focus 48 and the shock wave arising there as a result of the thermodynamic stress that arises, such that a quasi-mechanical ablation of the substrate material 12a takes place in addition to the light-induced ablation.
This substrate material 12a ablated quasi-mechanically in this way was not irradiated, which leads to a saving of energy and time.
In a modification, the groove scanning pattern 64.4 is scanned twice in the same scanning position 74, wherein the groove scanning pattern 64.4 during the second scan is scanned in a manner rotated relative to the groove scanning pattern 64.4 of the first scan, such that the hatch lines 66 of the two groove scanning patterns 64.4 cross one another in the relevant scanning position 74. Preferably, the rotation angle is 90°.
As can be understood, a column structure with a multiplicity of individual columns arranged in a column matrix can arise in this way.
As a result of the process dynamics explained, cracks arise in the ribs 106 or columns under the influence of the shock waves, which subsequently leads to substrate material 12a chipping off, which is then rinsed away by the rinsing fluid.
It has been found in practice that damage can occur in that substrate material 12a which bounds the temperature-regulating hollow structure 22 as encasing material. Damage occurs here on the side of the temperature-regulating hollow structure 14 which is remote from the light source 44 of the laser beam 46, taking account of the reference coordinate system in the lower encasing material of the temperature-regulating hollow structure 22.
Particularly in an arc region as illustrated at 22b in
Such filaments 108 constitute just one example of damage in the substrate material 12a. Such damage can adversely influence the long-term stability of the figure of the carrier substrate 12″ and it is desirable to minimize corresponding damage.
It has been found that formation of such filaments 108 occurs to a significant extent if slices 62 are ablated with an ablation direction ad from the top downward.
As things stand, this may be based on the fact that the ablation along a first hatch line 66.1 shades the ablation locations 56 of the succeeding hatch line 66.2 of a scanning pattern 64, which is shown schematically in
At the present time, it is assumed that in the center of the slice 62 these shaded regions are presumably concomitantly detached during the processing of the then following hatch line 66.3, which may be due, inter alia, to the shock waves explained above. Therefore, undesired effects do not occur in these regions of the slices 62.
However, if the focus 48 is situated at the lower margin of the slice 62 and thus at the lower encasing surface of the temperature-regulating hollow structure 22, no such ablation takes place there. In the case of the then following slice 62 in the next scanning position 74, which slice begins at the bottom in the meandering process, the effective slice distance ad is doubled, whereby a very large amount of energy of the laser beam 46 is radiated into the substrate material 12a present there as solid material. This in turn leads to the damage, for reasons explained above.
Such filaments 108 or comparable damage into the lower encasing material of a temperature-regulating hollow structure 22 can be avoided if the ablation direction ad is chosen to be from the bottom upward for each slice 62 during the scanning of the scanning patterns 64 in the scanning positions 74.
As illustrated by
In this respect, a congruent process with a uniform ablation direction ad in the scanning positions 74 belonging to the process is carried out here, as was explained above with regard to
Formation of filaments 108 or comparable damage in the encasing material of the temperature-regulating hollow structures 22 can also be reduced or avoided by a scanning position 74(n) being followed by a scanning position 74(n+1) that defines an intermediate scanning position 112. In such an intermediate scanning position 112, an intermediate slice 114 is ablated as slice by virtue of an intermediate scanning pattern 116 being scanned there as scanning pattern. In the case of an intermediate scanning pattern 116, all functionally corresponding structural components bear the same reference signs as in the case of the scanning patterns 64 and the explanations for the scanning patterns 64 in this respect analogously apply, mutatis mutandis, to the intermediate scanning patterns 116.
Six scanning positions 74(n), 74(n+1), 74(n+2), 74(n+3), 74(n+4) and 74(n+5) are shown, every second scanning position 74(n+1), 74(n+3) and 74(n+5) of which respectively defines an intermediate scanning position 112.
An intermediate scanning pattern 116 in an intermediate scanning position 112 is defined in relation to that scanning pattern 64 which is scanned in the preceding scanning position 74. In this case, the hatch lines 66 of the intermediate scanning pattern 116 in the intermediate scanning position 112 cover a smaller area than the hatch lines 66 of the scanning pattern 64 which was scanned previously in a preceding scanning position 74 which is not an intermediate scanning position 112.
This is shown in the projection view, in which an intermediate scanning pattern 116 has at least in one direction y or z a smaller extent than a scanning pattern 64 in a preceding scanning position 74 which is not an intermediate scanning position 112. To put it another way, in the case of the exemplary embodiments shown here, the intermediate scanning patterns 116 are oriented in such a way that said direction is the z-direction.
As a result, an intermediate slice 114 ablated in an intermediate scanning position 112 has only a partial extent in comparison with a slice 62 ablated in a scanning position 74 with a scanning pattern 64.
In the exemplary embodiment shown here, the intermediate scanning positions 112 are tilted relative to the yz-plane by the same pitch angle α as the scanning positions 74 with scanning patterns 64. In modifications which are not shown, however, the intermediate scanning positions 112 can also be pitched at angles α′ which differ from the pitch angle α. Moreover, pitch angles α or α′ of different intermediate scanning positions 112 can be different.
An intermediate scanning position 112 can be located centrally between two adjacent scanning positions 74 in the longitudinal direction 60, as is shown by way of example in FIG. 23B. However, an intermediate scanning position 112 can also be offset in the direction of the preceding scanning position 74 or in the direction of the succeeding scanning position 74.
If scanning positions 74 are provided as intermediate scanning positions 112, the scanning trajectory 78 thus also comprises the trajectory sections in the form of the intermediate scanning patterns 116, which are respectively scanned in the intermediate scanning positions 112, with their hatch lines 66 and hatch jump paths 68.
In different intermediate scanning positions 112, it is also possible to apply differently designed intermediate scanning patterns 116 with different hatch lines 66.
In principle, an intermediate scanning pattern 116 is intended to be formed in such a way that the deepest point of the temperature-regulating hollow structure 22 is covered in a section of the temperature-regulating hollow structure 22 which also extends in a horizontal direction. If the temperature-regulating hollow structure 22 is intended to have for example a rectangular cross-section there, rather than a curved cross-section, this is then at least the lower base surface of the temperature-regulating hollow structure 22.
In the case of the examples shown here, however, the intermediate scanning pattern 116 covers a lower segment of the cut surface of the temperature-regulating hollow structure 22 in the intermediate scanning position 112, i.e. specifically here a segment of an ellipse. As a result, the risk of damage can be reduced again.
It is also possible for two and more intermediate scanning positions 112 to be adjacent, i.e. to be present one behind another in a plurality of adjacent scanning positions 74(n), 74(n+1).
This is shown by
In the case of the exemplary embodiments explained hitherto, each scanning pattern 64 of a scanning position 74(n), that is to say in other words also each intermediate scanning pattern 116 in an intermediate scanning position 112, is completely scanned between its starting point 64a and its end point 64b and only then is there a jump to the next scanning position 74(n+1). This means that between two adjacent scanning positions 74 or between one scanning position 74 and the following scanning intermediate position 112 or between two scanning intermediate positions 112 or between one scanning intermediate position 112 and the following scanning position 74, a jump is effected only a single time.
As is evident in
As was explained above, a pattern jump path 76 always proceeds from a jump end 66b of a hatch line 66 of the scanning pattern 64 of the first scanning position 74(n) to a jump beginning 66a of a hatch line 66 of the scanning pattern 64 of the second scanning position 74(m).
In the case of the pattern jump paths 76 from the intermediate scanning pattern 116 to the scanning pattern 64, the first scanning position 74(n) is thus the intermediate scanning position 112 and the second scanning position 74(m) is the preceding scanning position 74(n−1) with the scanning pattern 64 and it thus holds true that m=n−1, i.e. m<n.
In this case, each end 66b of each hatch line 66 of the intermediate scanning pattern 116 is the beginning of a pattern jump path 76.
In the case of the present exemplary embodiment, from the bottom upward, the hatch lines 66 of a scanning pattern 64 of a scanning position 74(n) are scanned in alternation with the hatch lines 66 of the intermediate scanning pattern 116 in the adjacent intermediate scanning position 112.
The meandering concept is followed here, which has the consequence that the hatch lines 66 of the scanning pattern 64 in the alternation section point in one direction, here the positive y-direction, whereas the hatch lines 66 of the intermediate scanning pattern 116 point in the opposite direction, here the negative y-direction.
This scanning pattern 64 is moreover a representative example of a variant of a sector scanning pattern 64.3 having sectors 98 in which the sequence of the scanning directions of the hatch lines 66 is different. Here these are sectors 98.1 and 98.2. In this case, there can also be two sectors 98 in which the hatch lines 66 are each scanned parallel to one another, but with opposite scanning directions in the sectors. Two meandering sequences can be present, too, which however start with different scanning directions. In addition, in the case of sector scanning patterns 64.3, overlaps of regions with different scanning directions and of regions with different hatch distances hd can occur.
Furthermore, this scanning pattern 64 is an example of the variant mentioned in the introduction where a scanning pattern 64 can also describe just a part of a then superordinate scanning pattern. In the present case, the sector 98.1 corresponds to a line-to-line scanning pattern 64.1 and the sector 98.2 corresponds to a meandering scanning pattern 64.2, which together form the then superordinate sector scanning pattern 64.3.
Such a sector scanning pattern 98 can be used in particular even without a change in the pulse energy EP.
This alternation concept can also be implemented in extended fashion if two and more intermediate scanning positions 112 are adjacent, as is shown in
There, scanning patterns 64 are scanned in the scanning positions 74(n) and 74(n+4) and intermediate scanning patterns 116 are scanned in the scanning positions 74(n+1), 74(n+2) and 74(n+3). The scanning trajectory 78 comprises a jump sequence from the bottom upward from the scanning position 74(n) to the scanning position 74(n+1) to the scanning position 74(n+2) to the scanning position 74(n+3) and back again to the scanning position 74(n). If the alternation region 118 of the scanning pattern 64 has been scanned through, the intermediate scanning patterns 116 have also been scanned and the remaining part of the scanning pattern 64 is scanned and then there is again a jump downward to the full scanning pattern 64 in the scanning position 74(n+4).
In this case, therefore, the abovementioned jump takes place from a scanning position 74(n) to a scanning position 74(m) where m=n+2, n+3, . . . n+i, wherein here consequently m=n+4.
Here, too, each end 66b of each hatch line 66 of the intermediate scanning patterns 116 in the individual intermediate scanning positions 112 is the beginning of a respective pattern jump path 76.
The total ablation volume which is ablated by the scanning of the scanning pattern 64 and of the plurality of intermediate scanning patterns 116 linked therewith results from the volumes of the individual slices 62 which are defined by the ablation volume in each of the scanning positions 74. The slices 62 here are just no longer produced by a scanning process continuously over the entire scanning pattern 64/116, but rather arise progressively from alternation to alternation between the scanning positions 74.
In the circumferential direction these structural elements 94 are at a distance of the order of magnitude of 0.5 to 1.5 times the distance between two adjacent hatch lines 66 and can be at a distance from one another of in particular between 10 μm and 30 μm, with preference between 15 μm and 25 μm and preferably approximately 20 μm. The radial shaping can be present with a ratio of 1:100 to 1:7 relative to the average diameter at a cross-section of the temperature-regulating hollow structure 22.
In an opposite region, here the lower region, in which the intermediate scanning patterns 116 were also scanned, the internal lateral surface 80 is formed by a structure 119 which is different therefrom and which has a significantly more uniform area with less shaping in the radial direction than the rib structure 90a. In particular, there are no ribs shaped in this way in the structure 119.
Such a surface structure or an at least similar surface structure having a rib structure 90a and a structure 91 which is different therefrom can also arise upon the application of intermediate scanning planes 112 in accordance with
In the case of all the scanning patterns 64 described above, the respective ablation location 56 at the beginning 66a and at the end 66b of a hatch line 66 during scanning of the scanning pattern 64 is situated in the substrate 12 where the internal lateral surface 80 of the temperature-regulating hollow structure 22 arises or remains.
As a result of acceleration and retardation effects in the setting of the movable components of the focusing device 50, in particular the mirror 52 of the scanning device 52, local increases there in the incidence of the laser beam 46 can occur. At the beginnings 66a and ends 66b of the hatch lines 66, an accumulation of pulses of the laser beam 46 then takes place, as a result of which more energy is input there. This introduces local additional heating and heat accumulation effects into the substrate material 12a, which can in turn lead to undesired damage to the substrate material 12.
This risk is reduced by scanning patterns being designed as contour scanning patterns 120 which define a contour region 122 and a core region 124, wherein the contour region 122 at least sectionally radially surrounds the core region 124.
In this case, hatch lines 66 are scanned as core region 124 of the contour scanning pattern 120, wherein in the contour region 122 one or more hatch lines 66 are scanned in the form of contour hatch lines 126 which supplement the hatch lines 66 in the core region 124 and have a course along the contour of the contour scanning pattern 120. As a result, such a contour hatch line 126 in the contour region 122 thus runs at least sectionally along the contour of the temperature-regulating hollow structure 22 to be produced.
The hatch lines 66 in the core region 124 can again correspond to a scanning pattern 64 in the variants described above.
This is illustrated by
In the case of the exemplary embodiment in accordance with
In the case of the exemplary embodiment in accordance with
In both figures, the hatch jump path 68 between the last circular hatch line 128 of the contour region 122 in the scanning process and respectively the spiral hatch line 130 and the first hatch line 66 of the core region 124 is in each case provided with a reference sign.
During the scanning process, a contour scanning pattern 120 is scanned from radially on the outside to radially on the inside in such a way that first the contour region 122 and then the core region 124 are scanned.
If a contour scanning pattern 120 is scanned, the ablation direction ad for the slice 62 ablated in this way is defined by the scanning pattern 64 in the core region 124.
In this way, firstly as it were a circumferential groove is incorporated into the substrate material 12a, as a result of which in the substrate material 12a there is no longer a thermally conductive material connection between the ablation locations 56 at the hatch lines 66 of the scanning pattern 64 in the core region 124 and the encasing internal surface 80 of the temperature-regulating hollow structure 22.
The heat that arises during scanning of the core region 124 of the contour scanning pattern 120 then propagates in the longitudinal direction 60 into the substrate material 12a. However, since this substrate material 12a is ablated in a following scanning position 74, this has no adverse effects on the temperature-regulating hollow structure 22.
This concept of a contour scanning pattern 120 can also be implemented in the case of intermediate scanning patterns 116, wherein the contour region 122 can be provided for example only along the lateral surface 80 of the temperature-regulating hollow structure 22 and meandering contour hatch lines 126 are then preferably provided. This is shown by
By way of the contour scanning patterns 120, a periodic structure 90 can likewise be formed on the internal lateral surface 80 of the temperature-regulating hollow structure 22, as is illustrated by
What can additionally be achieved in particular by the use of contour scanning patterns 120 is that the internal lateral surface 8 of the temperature-regulating hollow structure 22 is formed at least regionally by a roughness structure 131 having a mean roughness Ra in accordance with DIN EN ISO 25178, version as at June 2023, of between 10.0 μm and 5.0 μm, which in particular is between 10.0 μm and 6.5 μm, between 10.0 μm and 8.0 μm, between 8.5 μm and 5.0 μm, between 7.0 μm and 5.0 μm or between 8.5 μm and 6.5 μm, or having a mean roughness Ra of 5.0 μm and less, which in particular is between 5.0 μm and 0.1 μm, preferably between 4.5 μm and 0.125 μm, between 4.0 μm and 0.15 μm, between 3.5 μm and 0.175 μm or between 3.0 μm and 0.2 μm.
Such a roughness structure 131 is distinguished by the fact that it defines, in the sense of the mean roughness Ra, a continuously smooth surface region of the internal lateral surface 80. In particular, no structures with radial shapings of orders of magnitude which exceed the mean roughness Ra there are present there.
An internal lateral surface 80 of the temperature-regulating hollow structure 22 can result in which the roughness structure 131 extends out along the full circumference in the circumferential direction at least in a section in the longitudinal direction 60 of the temperature-regulating hollow structure 22.
This is illustrated by a solid circular line in
In order that such a roughness structure 131 arises, for example the parameters of the processing beam 46 can be adapted, in particular with regard to the diameter at the ablation focus 48 if the contour hatch line 130 is scanned. Alternatively or supplementarily, for example, a contour scanning pattern 120 can also be scanned two or more times in one and the same scanning position 74, wherein two successive contour scanning patterns 120 are rotated relative to one another, such that their ablation foci 48A overlap at the internal lateral surface 80.
As was explained above regarding the use of shock waves and the groove scanning pattern 64.4, in the case of relatively large hatch distances hd between the hatch lines 66 material structures of the substrate material 12a may remain at the ablation location 56. As an alternative to rotating the same scanning pattern 64.4 to and fro in successive scanning positions 74, a 3D structure scanning principle can be implemented, in which scanning patterns are displaced relative to one another in scanning positions. This is shown by
In this case,
The scanning pattern 120 is scanned once in the scanning position 74(n). The scanning pattern 120 is scanned twice in each case in the following two scanning positions 74(n+1) and 74(n+2). In
In the second scanning position 74(n+1), for the first scan the groove scanning pattern 64.4 in the core region 124 is displaced relative to the contour region 122 in such a way that the hatch lines 66 are offset in the z-direction relative to the reference scanning pattern 64.4 in the scanning position 74(n), wherein the foci 48 are arranged so as still to overlap in the z-direction on two adjacent hatch lines 66 of the scan in the scanning position 74 and of the first scan in the scanning position 74(n+1). For the second scan in the scanning position 74(n+1), the groove scanning pattern 64.4 is displaced upward even further in the scanning position until the foci 48 are situated beside the foci 48 of the first scan in the scanning position 74(n+1). During the second scan, only the scanning pattern 64.4 can be scanned without a contour hatch line 126. Therefore, the reference signs 120 for the pattern of the first scan and 64.4 for the pattern of the second scan are assigned in scanning position (74(n+1).
This scheme is repeated in the then following scanning position 74(n+2). In the further scanning position 74(n+3), again a single contour scanning pattern 120 is scanned with an offset relative to the reference scanning pattern 64.4, etc.
As a result, lateral webs 132 composed of substrate material 12a arise or remain in this way, which webs run in the y-direction and have a rhombic cross-sectional contour.
The principle explained here by way of example can be modified by adjusting the framework parameters. By way of example, it is possible to change the slice distance sd and the displacement distance of the scanning patterns 64 in a common scanning position 74(n), which may lead for example to a different pitch angle of the cross-sectional rhombus of the webs formed here. Other cross-sectional geometries are possible; optionally, for this purpose, more than two or different scanning patterns are also scanned in the scanning positions in which a plurality of scanning patterns are scanned.
As was explained in the introduction, it may be expedient, if appropriate, for the temperature-regulating hollow structures 22 also to be formed with cross-sections that are different than circular cross-sections and are not constant in the longitudinal direction 60. This can be achieved during the scanning process by virtue of the fact that in two successive scanning positions 74 different scanning patterns 64, 116, 120 are scanned, the scanning area 72 of which differ in size and/or geometry.
This can help for example—in the context of cooling the optical element 8—to increase the cooling capacity, which increases as the cross-sectional area of the flowing cooling fluid increases.
A first approach involves changing the scanning area 72 symmetrically with respect to the longitudinal central axis 134 of the temperature-regulating hollow structure 22 in the longitudinal direction 60. This approach can be carried out without difficulties in the case of a vertical section.
In
In the course of a progressive enlargement of the cross-section symmetrically with respect to the longitudinal central axis in such sections 136, the ablated slice 62 in a scanning position 74(n+1) is always larger than the slice 62 in the preceding scanning position 74(n). If intermediate slices 114 are ablated, these have in relation to the longitudinal central axis 138 at least regionally a larger radial extent than the preceding slice 62 or intermediate slice 114.
If the scanning area 72 and thus the slice 62 at the deepest marginal line 138 of the temperature-regulating hollow structure 22 is at a deeper level than in the preceding scanning position 74, i.e. if the deepest marginal line 138 will have a course inclined downward relative to the xy-plane from the scanning position 74(n) to the scanning position 74(n+1), there is a change however in the relations with the substrate material 12a present there below the temperature-regulating hollow structure 22. This also applies in the circumferential direction perpendicular to the marginal line 138, i.e. in
Therefore, in such sections 136 of the temperature-regulating hollow structure 22, a scanning concept illustrated in
If the cross-section is intended to be reduced in size, this can be done by a change in the scanning area 72 which is symmetrical about the longitudinal central axis 134.
In this way, in the direction of the later carrier surface 14, a flow surface 140 with a harmonic structure is formed thus by periodically occurring elevations and depressions. In this case, the internal lateral surface 80 of the temperature-regulating hollow structure 22, in longitudinal sections, follows a wavy line 142 at least on one side. If the narrowed portions and widened portions were produced in accordance with
In the case of the variant used here according to
A harmonic structure should be understood here to mean a structure with fluidically soft transitions in which macroscopically there are no or only slightly shaped steps or edges which promote turbulences and vortices of a flowing fluid.
Vias such structures, along the temperature-regulating channel 22 it is possible to increase the area of contact with the substrate material 12a in the direction of the carrier surface 14, thereby enabling a greater heat transfer between a temperature-regulating fluid flowing through and the substrate material 12a there.
The cross-sectional areas of the temperature-regulating channel 22 there are still circle areas and thus symmetrical with respect to the longitudinal central axis 134.
In a modification that is not shown separately, harmonic structures can also be formed on the underside of the temperature-regulating hollow structure 22.
The recesses 144 have a length l in the x-direction, a width w (this designation w in the German text being derived from the English word) in the y-direction and a height h in the z-direction and are arranged at a distance a from the nearest recess 144, provided that there is one. These parameters l, w, h and a can have different values for different recesses.
The geometry and dimension of the recesses determined by the parameters l, w, z and a as well as by their cross-section and longitudinal section are geared to producing an upper flow zone 144a and a lower vortex zone 144b for the temperature-regulating fluid, which is designated here by 146. The upper flow zone 144a of a recess 144 is configured such that there is flow through it in the longitudinal direction 60 largely without turbulences or vortices, which is shown by flow lines of the temperature-regulating fluid 146 there in
Starting from a certain depth in the recess 144, however, the flow is disrupted at the boundary wall 146 of the recess that lies in the longitudinal direction 60, and a vortex flow 148 forms downward, the temperature-regulating fluid 146 circulating as it were in this vortex flow at least at times; this, too, is illustrated by flow lines. After one or more circulation cycles, a portion of this circulating temperature-regulating fluid passes again into the flowing-past part of the temperature-regulating fluid 146 and is then recirculated.
As a result, however, this reduces a heat transfer between the temperature-regulating fluid 146 and the substrate material 12a at the recesses 144. For cooling of the substrate 12 with a cooling fluid, via a temperature-regulating hollow structure 22 for the purposes of this exemplary embodiment that at the top side heat of the substrate material 12a is effectively absorbed by the cooling fluid, but this heat is not input into the substrate material 12 on the underside 12a to the extent that would be the case without the recesses 144. As a result, the heat overall can be dissipated from the substrate 12 particularly effectively by the cooling fluid flowing away.
Such recesses 144 on the underside of the temperature-regulating hollow structure 22 can also be provided without harmonic structures 140 being formed on the top side. Moreover, the harmonic structures 140 and recesses 144 can be provided in a manner offset in the longitudinal direction 160.
In this case, the flow behavior of the temperature-regulating fluid 146 in particular in the vortex zones 144b of the recesses 144 is not only determined by the dimensions 1, w, h and a of the recesses 144 but also depends, inter alia, on the viscosity and the volumetric flow rate of the temperature-regulating fluid 146.
Such vortex flows 148 additionally have the advantageous property of producing only comparatively small FIVs (“flow induced vibrations”) at the internal lateral surface 80 of the temperature-regulating hollow structure 22.
In order to counteract the FIVs to an even greater degree, the scanning patterns 64, 116, 120 which are scanned in the scanning positions 74(n) can be designed in such a way that periodic structures 90 as flow structures 150 which reduce the frictional resistance vis-à-vis a flowing liquid temperature-regulating fluid 146 are formed on the internal lateral surface 80 of the temperature-regulating hollow structure 22.
In practice, good flow behaviors were able to be achieved here in particular with riblet structures 152 with ribs 154 formed in the longitudinal direction 60, which is indicated merely highly schematically in
On the internal lateral surface 80 of the temperature-regulating hollow structure 22, there may also be individual sections in the longitudinal direction 60 whose flow structures 150, optionally specifically ribs 154, are offset in the circumferential direction. Further modifications involve forming, in the circumferential direction of the temperature-regulating hollow structure 22, regions of the internal lateral surface 80 that are also only spaced apart from one another with flow structures 150.
The riblet structures 152 can also correspond to the surface 158 of a kind of scale structure 160 constructed from a multiplicity of individual scales 162 with such ribs 154. Such a surface 158 is derived from the scale surface of a shark. This is illustrated by
In modifications not shown separately here, structures, in particular flow structures 150, can also be produced on the internal lateral surface 80 of the temperature-regulating hollow structure 22 by a correspondingly prestructured film or a correspondingly prestructured inlay being drawn into the temperature-regulating hollow structure 22.
Alternatively, firstly a film or an inlay that are smooth in regard to the desired structures can also be drawn into the temperature-regulating hollow structure 22 and only then processed in such a way that the desired structure, in particular a flow structure 150, is produced. By way of example, hoses, preferably corrugated hoses, with plastic inliners composed of polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymer (THV) or the like can be used for this purpose. Preferably, such hoses can be provided at diverters of the temperature-regulating hollow structure 22, where a majority of the FIVs arise as a result of a flowing temperature-regulating fluid.
The structuring of the internal lateral surface of temperature-regulating hollow structures is also considered in the German patent application 10 2024 116 622.3, the entire disclosure of which is hereby incorporated by reference in the present application.
The projection exposure apparatus 200 comprises an illumination system 202 with a radiation source 204 and an illumination optical unit 206 for illuminating an object field 208 in an object plane 210, in which a reflective reticle 212 is arranged. In the exemplary embodiment illustrated, the radiation source 204 is an EUV radiation source which emits EUV radiation as working radiation 214, in particular in a wavelength range of between 5 nm and 30 nm. The radiation source 204 can be a plasma source, for example an LPP (laser produced plasma) source or a GDPP (gas discharge produced plasma) source. Alternatively, a synchrotron-based radiation source or a free electron laser (FEL) can be used as the radiation source 204.
Moreover, the projection exposure apparatus 200 comprises a projection optical unit 216 for imaging the object field 208 into an image field 218 situated in an image plane 220 of the projection optical unit 216. As an example of an object 222, a wafer bearing a light-sensitive layer (referred to as a resist) is arranged in the image plane 220. Components for synchronously moving the reticle 212 and the wafer 222 are merely indicated in
The projection exposure apparatus 200 comprises a plurality of optical elements 8 in the form of mirrors Mn, which are consecutively numbered in accordance with their arrangement in the beam path of the projection exposure apparatus 200. In the present case, a total of 10 mirrors M1 to M10 are present in the beam path.
The mirrors M3 and M4 are embodied as facet mirrors containing a multiplicity of individual mirrors. Each of the other mirrors Mn is a mirror 10 with a monolithic mirror substrate 12 and a coating 16 borne thereby, as shown by way of example in
The mirrors M1 to M4 in the illumination system 206 serve to illuminate a section of the reticle 212 with the desired illumination angle distribution. The mirrors M5 to M10 of the projection optical unit 216 image this section onto the wafer 222 in a reduced size. As a result, the structures contained in the reticle 212 are imaged onto the light-sensitive layer borne by the wafer 222.
With the aid of the optical elements 8, which in the present exemplary embodiment are formed as mirrors 10 for the EUV projection exposure apparatus 200 and the coating of which is configured at least to reflect at least 50% of EUV light impinging with normal or almost normal incidence, the object 222 is irradiated with the working radiation 214.
The apparatus 6 pertaining to semiconductor technology is part of a production process which can be used to produce a structured electronic component 224, which is shown in
The structured electronic component 224 is in particular a computer chip 228, during the production of which a projection exposure apparatus, here the projection exposure apparatus 200, is used, as was discussed in the introduction.
The scanning patterns 64, 116, 120 explained hitherto comprise a plurality of hatch lines 66.
In the following exemplary embodiments, this hatch line 66 is rectilinear; in modifications that are not shown separately, however, the hatch line 66 of a single-hatch scanning pattern 164 can also be curved and have an arcuate course.
The pattern scanning path of a single-hatch scanning pattern 164 is likewise defined by this hatch line 66, which correspondingly also predefines the scanning position 74. A slice 62 is then defined by that ablation volume which is ablated along this hatch line 66; a corresponding slice 62 produced by scanning of a single-hatch pattern 164 is referred to hereinafter as hatch slice 166.
During a scanning process with single-hatch scanning patterns 164, there are therefore no hatch jump paths 68. However, the end 66b and the beginning 66a of the hatch line 66 are simultaneously the jump end and jump beginning, respectively, and also the pattern end point 64b and pattern starting point 64a, respectively, of the single-hatch scanning pattern 164. Therefore, as already explained, a pattern jump path 76 proceeds from the jump end 66b of the hatch line 66 of the single-hatch scanning pattern 164 of a first scanning position 74(n) to a jump beginning 66a of a hatch line 66 of the single-hatch scanning pattern 64 of a second scanning position 74(m). The positions 66a, 64a and 66b, 64b shown in
Single-hatch scanning patterns 164 can then be scanned in particular in a sequence in which the respective hatch lines 66 in different scanning positions 74(n) each extend in the radial direction between the longitudinal central axis 168 and the outer screw line 170 of a geometric, i.e. not really present, reference helix screw 172 with a screw flight 174, as elucidated by
Via such a helix scanning process, a screw volume 176 can be ablated in the longitudinal direction 60 of the temperature-regulating hollow structure 22 to be produced.
The longitudinal central axis 168 of the reference helix screw 172 need not be a straight axis, but rather is defined analogously to the longitudinal direction 60 of a temperature-regulating hollow structure 22 in each case at a midpoint taking into account the preceding course and the following course of the reference helix screw 172. The geometric helix screw 172 can thus also have a curved course, whereby flight sections can also overlap in the geometric consideration. The ablated screw volume 176 is then correspondingly curved.
A longitudinal section 178 of a geometric helix screw 172 can be described by a screw radius Sr and the pitch h. The pitch h is the distance measured in the longitudinal direction between each two adjacent sections 174a and 174b of the screw flight 174 of the helix screw 172, wherein in this way it is also possible to define a partial helix screw with such a short flight course in which there are no flight sections that are directly adjacent in the longitudinal direction. Both the screw radius Sr and the pitch h of the helix screw 172 can change along the longitudinal central axis 168 and need not remain constant.
In this way, it is possible, for example, to produce the temperature-regulating hollow structures 22 shown in
The illustrations in
During the helix scanning process, preferably the pitch h of the reference helix screw 172 and here, therefore, of the single-flight helix screw 180 is then chosen to be so small that a string full volume 182 is ablated which largely corresponds to the corresponding volume of the produced temperature-regulating hollow structure 22 in this section. This is illustrated by
As shown in
In this case, the screw radii Sr and pitches h can be identical for each helix scanning process or can be defined individually for each helix scanning process along the longitudinal central axis 168, i.e. for each scanning position 74.
Put generally, a number n of helix scanning processes are carried out with a rotation angle γ between two successive helix scanning processes.
The above examples elucidate this process for n=2, 3, 4 where g=360/n. However, the rotation angle can also be different than 360/n and given n>2 can also be different between two respectively successive scanning passes.
The pitches h of the respective reference helix screws 172 for each helix scanning process are each coordinated here in such a way that after the corresponding number n of helix scanning processes has been carried out, the desired string full volume 182 has been ablated. In this case, the pitches h can be different for different helix scanning processes and can be variable within a respective helix scanning process.
As explained above, the temperature-regulating hollow structures 22 define an internal lateral surface 80, the structural formation of which depends on the completed scanning trajectory 78, inter alia.
The internal lateral surface 80 can then be processed and formed with the aid of a contour helix scanning process that likewise uses single-hatch scanning patterns 164. A contour scanning process is generally carried out in addition to the above-explained scanning process(es) by which material has already been ablated in order to form the temperature-regulating hollow structure 22.
In this case, the hatch lines 66 are thus correspondingly curved. In one modification, the hatch lines 66 of the single-hatch scanning patterns 164 used can also be rectilinear and be scanned in such a way that each hatch line 66 lies approximately tangentially against the screw line 170.
The resulting hatch slice 166 is then in each case the ablation volume along a section of a helix coil 192, as shown in
In
The lengths of the hatch lines 66 of the individual single-hatch scanning patterns 164 can be different. Optionally, during the contour helix scanning process, it is also possible for just a single single-hatch scanning pattern 164 to be scanned, the hatch line 66 of which then corresponds to the screw line 170 over the entire extent thereof. The hatch slice 166 is then the full volume of the helix coil 192.
As a result, in this way a volume corresponding to a helical strip 194 is ablated, as shown in
By way of example, a partial cross-section scanning pattern 196 corresponds to the scanning pattern 64 in the intermediate scanning position 112, as was explained above with reference to
The partial cross-section scanning patterns 196 are scanned in a partial pattern scanning process in which these are arranged in the scanning positions 74 in such a way that each ablated slice 62 lies on the outside against a screw line 170. Identical or different partial cross-section scanning patterns 196 are scanned in each scanning position 74, wherein the partial cross-section scanning patterns 196 in two successive scanning positions 74(n) and 74(n+1) are rotated by a rotation angle γ in the circumferential direction.
In the exemplary embodiment presently shown, the partial cross-section scanning patterns 196 cover a semicircle and half of the cross-section of the temperature-regulating hollow structure 22, where the rotation angle γ=45°. However, the partial cross-section scanning patterns 196 can also cover other area regions of the cross-section of the temperature-regulating hollow structure 22 and be scanned with rotation angles γ adapted thereto. Partial cross-section scanning patterns 196 scanned in different scanning positions 74 may also be of different sizes and possibly not extend as far as the longitudinal central axis 168, whereby scanning need not be effected across the longitudinal central axis 168 in every scanning position 74.
As a result of the rotation of the partial cross-section scanning patterns 196 in different scanning positions 74 by the rotation angle γ, a uniform material ablation is achieved in all regions of the temperature-regulating hollow structure 22.
For more intensive processing of the internal lateral surface 80, specific sections of the temperature-regulating hollow structure 22 can be scanned a number of times in this way, wherein the sequence of the partial cross-section scanning patterns 196 in this section relative to the scanning positions 74 is repeated or begins in a different scanning position 74. In the latter case, the partial cross-section scanning patterns 196 are alternately interspersed, as it were, relative to the scanning processes already carried out.
This concept can also be utilized in the application of the intermediate scanning position 112 via a plurality of intermediate slices 114 being produced.
As has already been explained with regard to
Such changes in the pitch angle α are visible particularly if the intention is to form temperature-regulating hollow structures 22 with sections whose longitudinal direction 60 is at a similar angle with respect to the yz-plane.
In the case of the slice 62.1 and the preceding slices in the section 22c. 1, the pitch angle α1=−45 in the case of angles of the longitudinal direction 60 of the temperature-regulating hollow structure 22 with respect to the yz-plane of between 90°, which corresponds to a horizontal course, and approximately 45°, which corresponds to an inclination upward toward the left. The negative pitch angle α1=−45° is illustrated in the coordinate system shown.
In the second arc region 22b.2, in particular, the longitudinal direction 60 of the temperature-regulating hollow structure runs at an angle of −45° with respect to the yz-plane. If the scanning pattern 64 were scanned there with the same pitch angle α=−45, a very large scanning pattern 64 would have to be scanned in order to ablate the cross-section of the temperature-regulating hollow structure 22 in the longitudinal direction 60 there. In this case, problems may arise in particular when rinsing such large regions in order to rinse away the ablated substrate material. What is more, severe arcs over approximately 180° may also give rise to shading that precludes a scanning process.
This is avoided if the pitch angle α is chosen depending on the angle of the longitudinal direction 60 of the temperature-regulating hollow structure 22 with respect to the yz-plane.
In the case of the slice 62.2 and the preceding slices, the pitch angle α2=90° in the case of angles of the longitudinal direction 60 of the temperature-regulating hollow structure 22 with respect to the yz-plane of between 45° and 0°, which corresponds to a vertical course.
In the case of the slice 62.3 and the preceding slices, the pitch angle is then a3=+45°, i.e. positive as in
In order to calculate the scanning process, the temperature-regulating hollow structure 22 to be produced can be subdivided into individual sections, for example, for which an appropriate pitch angle α is calculated. If there is a change in the pitch angle α in the process, small regions are scanned in an overlapping manner in order to attain a uniform transition between the individual sections. The number of individual sections is arbitrary and can also be very high. Optionally, the pitch angle α can be varied so that the angle of the slice 62 with respect to the longitudinal direction 60 of the temperature-regulating hollow structure 22 remains the same at every position.
In the case of the contour scanning patterns 120 explained with reference to
A large number of acceleration and retardation effects occur in the implementation, as a result of which the scanning of corresponding circular hatch lines 128 or spiral hatch lines 130 is time-consuming. Moreover, some focusing devices 50 established on the market are not designed for scans of short lines required and technical problems may occur.
In order to avoid this, a circular hatch line 128 or spiral hatch line 130 can be represented by polylines which can be scanned by a focusing device without the retardations and accelerations that are necessary otherwise. Polylines are in turn produced in terms of control engineering by a sequence of so-called microvectors, which can be implemented as an extremely small vector unit within a single clock cycle of commercially established RTC boards or modules used and corresponding fast hardware.
Two successive polylines can in turn be linked again by microvectors. If finely resolved interpolation point grids are supplementarily used as well, a particularly high accuracy and dimensional fidelity can be attained in particular for rounded freeform shapes. Finely resolved interpolation point grids are, in particular, interpolation point grids whose line length is in the range of less than 100 μm or in which the transition angle between two individual lines is less than 5°.
Figuratively speaking, the laser beam 46 is guided on a kind of vectorially established arc trajectory at a deflection point, in which case the laser is no longer deactivated between the individual trajectories, but rather is activated and moves at full speed through the individual interpolation points. Depending on the speed and the angle between the individual vectors, although this results in a higher inaccuracy than the operating mode with deflection trajectories, the resulting error owing to the very small angles is negligibly small and has no adverse effects on the quality of the temperature-regulating hollow structure 22. What can be achieved, rather, by way of a corresponding adaptation of the angle and speed parameters is that the transitions between the individual vectors are completely smoothed, whereby overall a continuous circular trajectory without sharp edges or bends is obtained.
It is known in the prior art to use RTC boards or modules in a so-called skywriting mode 3, which is able to independently recognize and directly implement suitable polylines on the basis of the desired target trajectory, i.e. here for example on the basis of a desired circular hatch line 128 or spiral hatch line 130.
In the case of the spiral scanning pattern 200 shown in
In the case of the spiral scanning pattern 200 shown in
By way of example, the spiral hatch line 130 can be defined in its xy-plane by r=√{square root over (cos(α)r(x)2+sin(α)r(y)2)}. This xy-plane serves to describe the spiral hatch line 130 and is not the xy-plane of the coordinate system which is anchored with the substrate 12.
In this case, in each revolution n, the radius r of the spiral trajectory is calculated numerically depending on the applicable angle for every point of the spiral trajectory. This firstly involves defining what two radii r(x) in the x-direction and r(y) in the y-direction the spiral is intended to have.
In order to deliberately ablate radially outer regions on the internal lateral surface 80 or radially inner regions on the longitudinal axis 60 of a temperature-regulating hollow structure 22, the complex spiral 206 can also be defined in its xy-plane by the function
This results in spiral trajectories with spiral lines positioned more closely at the outer edge, which then transition to a constant spacing.
Other suitable functions are sigmoid functions which guide spirals in which the outer and the central spiral lines run next to one another more closely than the middle spiral lines arranged therebetween.
Examples of such functions are
In this context, the course of the spiral hatch line 130 can be influenced directly by way of the value range of the function used. By way of example, a spiral that forms only the contour region 122 of the contour scanning pattern 120 can be represented in this way.
In principle, spirals with a flexible course are calculable in this way, which can be scanned as spiral hatch lines 130.
All of the methods, steps, sequences, concepts and principles above can be combined with one another, which is also reflected in the combinations of features specified in the claims. By way of example, one, a plurality or all of the scanning patterns explained can be used in the production of temperature-regulating hollow structures 22. In this case, different parameters described with respect to the processing light beam 46 can also be implemented supplementarily.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102023205568.6 | Jun 2023 | DE | national |
