Patent Application
20210018679
This application claims the benefit of priority of German Application Serial No. 10 2019 211 002.9, filed Jul. 24, 2019 and German Application Serial No. 10 2019 210 745.1, filed Jul. 19, 2019, each of which are hereby incorporated by reference in their entireties.
The disclosure relates to an optical system, a carrier substrate, and a method for manufacturing an optical system.
Optical elements—such as lasers, modulators, photodiodes, and other elements—are increasingly miniaturized. Compact optical systems can thus be implemented on suitable substrates, for example as a photonic integrated circuit (PIC). Such systems can be used to implement splitters, couplers, phase shifters, ring resonators, arrayed waveguide gratings, optical amplifiers, switches, and other functional units. Light is transmitted by waveguides, which can be embedded into optical components made of flat substrates or deposited thereon.
It can be advantageous when producing respective optical systems to provide an optical component with a recess or cavity into which then another optical component is inserted. A respective optical system and a respective manufacturing method are known from patent document DE 10 2016 203 453 A1.
When manufacturing optical systems of this type, there always is the problem of optically coupling waveguides of various components to be solved, that is, to align these so precisely to each other that light from one waveguide can be transmitted into another waveguide with sufficient efficiency for any intended applications.
Edge-emitting optical components are frequently used when manufacturing such systems, i.e. such components in which light propagating in the waveguide can exit from an end face of the component or light can be coupled into a waveguide through an end face. The respective end faces are arranged and aligned relative to each other in a suitable position and orientation for optical coupling of such components, which is also called butt coupling.
The precision requirements such alignment must meet are the higher the smaller the dimensions of the waveguides to be coupled. For example, a single-mode waveguide, which allows propagation of just one light mode, can have a cross section from a few hundred nanometers to a few micrometers, which predetermines respective narrow tolerances for optical coupling.
Various methods have been proposed for precise alignment of edge-emitting optical components in a butt coupling configuration.
In so-called active methods, a light signal which can be transmitted and measured when optical coupling is achieved can be maximized by positioning the components. But such methods are complex, accordingly costly, and can only be used in specific situations. They are also an obstacle to further miniaturization.
Passive methods do without measuring a light signal transmitted by the coupling and the required complex manufacturing assemblies. But these methods typically require compliance with extremely stringent manufacturing tolerances of the optical components (for example when aligning these relative to each other using reference contact surfaces), which again is complex and costly.
Furthermore, heterogeneous integration methods have been proposed for manufacturing PICs, wherein semiconductor materials are bonded on complementary metal oxide semiconductor wafers and the semiconductors are then finish-processed, which allows good precision due to the lithographic structuring of components. Such methods are practicable in few applications only due to process-related restrictions and low yield.
Accordingly, it is the problem of the disclosure to propose an optical system with improvements regarding the alignment of components, which improvements prevent or reduce the disadvantages mentioned. Furthermore, the problem is to propose a carrier substrate and a method for manufacturing an optical system.
This problem is solved, according to the disclosure, by an optical system according to claim 1, by a carrier substrate according to claim 11, and by a method according to claim 12. Advantageous embodiments and further developments of the disclosure result from the features of the dependent claims.
The proposed optical system includes a first optical component, comprising a first waveguide and a carrier substrate, wherein the first optical component is arranged on the carrier substrate.
The first optical component comprises a first markup set having a defined position and/or orientation with respect to the first waveguide, the carrier substrate comprises a second markup set, and it can be detected based on a relative position and/or orientation of the first and second markup sets if a desired orientation of the first waveguide relative to the carrier substrate is achieved in a reference plane extending parallel to a surface of the carrier substrate.
The first optical component and the carrier substrate each have a front side and a rear side located opposite the front side. Other side surfaces, which are oriented perpendicular to the front or rear side, respectively, are called end faces herein. Directions that are parallel to the front side—that is, also to the reference plane—are called lateral directions, directions perpendicular thereto are called normal directions.
Such an optical system has the advantage that, by detecting the orientation of the first optical component and the carrier substrate based on the relative position and/or orientation of the first and second markup sets—preferably while manufacturing the optical system—allows alignment of the first optical component and the carrier substrate to each other at high precision in a comparatively simple and cost-effective manner (namely by correcting a relative position and/or orientation of the first and second optical components and the carrier substrate). The system can also be prepared for arranging a second optical component with a second waveguide on the carrier substrate, wherein the first and second waveguides can be optically coupled. Particularly, the known advantages of passive alignment while easing manufacturing tolerances are achieved.
Using a carrier substrate with a markup set also has the advantage that it can be designed and manufactured separately from the optical components and thus provides considerable flexibility.
A markup set as defined in the present application includes one or more markings, a marking being an element the position and/or orientation of which can be detected by means of a suitable measuring device. This detection can particularly be performed optically, for example by means of a camera or another optical scanning or detection system (such as a laser scanning system with a raster scanner and a point, line, or area detector) as a measuring device. Detection can alternatively be performed in a different way, for example using electrical or magnetic or contact-based measuring. When detecting the position and/or orientation of a markup set, all markings, multiple markings, or just one marking can be detected completely or partially. Detection can include processing of data measured using the measuring device by means of a processing unit.
A markup set can thus be usable as positioning aid when aligning two components. Accordingly, a markup set or marking of a markup set can be an element which does not fulfill an optical, electronic, mechanical and/or other function other than being used as positioning aid. Alternatively, a markup set can fulfill other functions.
A marking can for example be a coating, an embedded part, or a part of a component, sections of which were modified with respect to specific properties, such as optical properties, relative to the environment. Alternatively, a marking can be a part usable and/or intended for other purposes, such as a structural part of a component, e.g. an edge, corner, surface, or a waveguide.
The optical system can include a second optical component arranged on the carrier substrate, comprising a second waveguide which can be optically coupled to the first waveguide.
The optical system can thus advantageously be extended, for example, by the optical, electronic, and/or electro-optical functionality of the second optical component.
The second optical component can include a third markup set with a defined position and/or orientation with respect to the second waveguide. It can be detected based on a relative position and/or orientation of at least two of the markup sets if the first and second optical components are oriented in a reference plane extending parallel to a surface of the carrier substrate in such a manner that optical coupling of the first and second waveguides is made possible.
Since the optical coupling is made possible, as described, by respective aligning of the optical components in lateral directions, optical coupling is initially prepared. Establishing optical coupling includes allowing optical coupling by aligning in lateral directions and in a normal direction.
The markup sets of the respective optical system can be configured such that they allow aligning the optical components to each other, which again includes aligning the waveguides to each other for establishing or improving or preparing optical coupling of the waveguides. Aligning the optical components to each other can include aligning of markup sets to each other by adjusting a relative position and/or orientation of the optical components and/or the carrier substrate in such a manner that a specified relative position and/or orientation of the markup sets is achieved. The specified relative position and/or orientation of the markup sets results from the defined position and/or orientation of the markup sets of the optical components with respect to the respective waveguide in such a manner that, by establishing the specified relative position and/or orientation, optical coupling of the waveguides is achieved, improved, or prepared. For aspects of aligning the optical components, all markings, multiple markings, or just one marking of the markup set may have to be completely or partially taken into account within a given markup set.
This means that passive coupling with the advantages mentioned is available for the waveguides of the two optical components.
The optical components and/or the carrier substrate can be flat or two-dimensionally extended elements, which may for example be implemented as chips or wafers or formed therefrom. At least one of the optical components and/or the carrier substrate may comprise a semiconductor chip (such as a silicon chip), a photonic integrated circuit (PIC), a silicon-on-insulator chip, a ceramic chip, and/or a glass chip and/or a polymer. Furthermore, the carrier substrate may contain materials such as silicon or other semiconductor materials, ceramics, glass, or polymers, or may consist thereof. At least one of the waveguides may contain a polymer, a glass, an oxide (such as SiO2), a nitride (such as Si3N4 in SiO2), and/or silicon (e.g. as Si or SiO2). The manifold embodiments and uses of such components, materials, and compositions as well as the methods for their manufacture and processing are thus transferred to the proposed method, including the advantages known to a person skilled in the art.
The optical components can be edge-emitting; the first and second waveguides can thus be arranged inside the respective optical component such that light can propagate in the waveguides parallel to the front end of the respective optical component—and/or emerge there—and can enter or exit the waveguide through a portion of an end face.
The end faces can be prepared by dry etching (using a lithographic varnish for targeted defined edge creation of the end faces) or mechanical polishing, or by breaking (optionally after previous heating) along defined crystal surfaces. This makes it possible to achieve advantageous properties for coupling light into and out of the waveguides through the end faces.
At least one of the optical components may have another or multiple other waveguides in addition to the first/second waveguide. The carrier substrate may also comprise at least one waveguide. If the carrier substrate has a waveguide, the method may comprise establishing an optical coupling between the waveguide of the carrier substrate and the first and/or second waveguide.
In addition to the waveguides, at least one of the optical components and/or the carrier substrate may include other elements, such as optical and/or electronic elements. For example, at least one of the optical components and/or the carrier substrate can be configured as an electro-optical circuit.
The second optical component may further comprise a recess through which the second optical component at least partially passes from a front side in the direction of a rear side located opposite the front side, wherein the first optical component is arranged in the recess.
Arranging an optical component in a recess of another optical component results in advantages with respect to thermal properties of the optical system, high-frequency applications, as well as scaling and manufacturing costs. This is also pointed out in patent document DE 10 2016 203 453 A1 mentioned above.
The recess may be produced in one piece, either mechanically or by means of a laser process, etched out, or by etching surrounding indentations (trenches) and subsequent removal of the remaining core. The recess may either completely or partially pass through the second optical component, wherein the latter case provides particularly good optical and mechanical accessibility of the interior of the recess.
The first and/or second optical component may of course have one or more other recesses. Accordingly, the system may include at least a third optical component, which again comprises at least one third waveguide which is optically coupled to the first and/or second waveguides and/or at least one fourth markup set having a defined position and/or orientation relative to the third waveguide and being arranged on the carrier substrate in the one other recess/one of the other recesses The fourth and first and/or second markup sets can then be suitable for detecting a relative position and/or orientation of the first and second waveguides to each other in the reference plane.
The second markup set can comprise: a first portion, adapted to bring the first waveguide into a defined position and orientation relative to the carrier substrate, and thus as well to the first waveguide, by aligning the first markup set and the first portion of the second markup set to each other, and a second portion, adapted to bring the second waveguide into a defined position and orientation relative to the carrier substrate by aligning the first markup set and the first portion of the second markup set to each other
The carrier substrate can be at least partially transparent and/or translucent for a specific wavelength range, particularly for visible light, ultraviolet light, and/or infrared light. Detecting the relative position and/or orientation of the second and first and/or third markup sets can advantageously performed using a camera unit which is placed near the rear side of the carrier substrate facing away from the optical components and can capture images of the optical components and their markup sets or portions of markup sets, respectively, through the carrier substrate. The camera unit can be configured for simultaneous capturing of images in multiple directions; for example, the camera unit can be provided with a beam splitter, whereby images can be taken and/or overlapped in two opposite directions at the same time. The camera unit configured in this manner can be inserted between the first component and the carrier substrate or between the second component and the carrier substrate (including any elements arranged thereon, such as the first optical components). The carrier substrate and the first/second optical components can then be simultaneously detected and aligned using the respective markup sets.
By detecting the relative position and/or orientation of two waveguides, positioning can be achieved at a maximum deviation from a desired relative position in lateral directions of, for example, less than 5 μm, less than 2 μm, less than 1 μm, less than 500 nm, or less than 200 nm, and/or a maximum angular deviation from a desired orientation in lateral directions of, for example, less than 10 mrad, less than 5 mrad, less than 2 mrad, or less than 1 mrad.
The first waveguide may have a first distance from the front side of the first optical component, the front side of the first optical component may be facing the carrier substrate, and the first distance may be selected such that a desired relative position and/or orientation of the first waveguide and the carrier substrate to each other is set in the normal direction.
This ensures a precise and repeatable orientation of the first waveguide relative to the carrier substrate in the normal direction.
In this situation, the second waveguide may have a second distance from the front side of the second optical component, the front side of the second optical component may be facing the carrier substrate, and the first and second distances may be selected such that a relative position and/or orientation of the first and second optical components to each other and in a normal direction perpendicular to a surface of the carrier substrate in such a manner that optical coupling of the first and second waveguides is made possible.
This results in an orientation of the first and second waveguides in the normal direction that contributes to optical coupling. This means that the advantages of passively aligning the waveguides can also be leveraged for orientation in the normal direction.
For example, a maximum deviation from a desired relative position in the normal direction can be achieved that is less than 2 μm, less than 1 μm, less than 500 nm, less than 200 nm, or less than 100 nm.
The first and/or second distances can be set by layers arranged on the front side of the first and/or second optical components. This ensures highly precise and repeatable alignment of the first and second waveguides to each other in the normal direction. Such layers can be deposited onto the front side of the first and/or second optical components using various methods, for example by epitaxy (also followed by metalizations or passivations, such as by means of oxide or nitride), plasma enhanced chemical vapor deposition (PECVD), or other layer deposition processes.
A desired efficiency of optical coupling can be achieved by combining suitable lateral and normal deviation tolerances, such that attenuation of the intensity of a light signal coupled into one of the other waveguides compared to the intensity of a light signal coupled out of another waveguide is for example less than 3 dB, less than 2 dB, or less than 1 dB.
A distance between a first end face of the first optical component where an end of the first waveguide to be coupled to the second waveguide terminates, and a second end face of the second optical component where an end of the second waveguide to be optically coupled to the first waveguide terminates, may for example be less than 2 μm, less than 1 μm, less than 500 nm, less than 200 nm, less than 100 nm, but also more than 2 μm The first and second end faces may also contact each other.
At least a portion of one of the markup sets can be used as a reference surface when setting the first and second distances.
For example, such a part of a marker set can be implemented as a metal layer of defined thickness on the front side of the corresponding optical component and/or of the carrier substrate, which defines a stop and thus a reference surface during arrangement of the optical components on the carrier substrate. Thus, a robust alignment can be implemented in the normal direction.
It may be provided that at least one part of at least one of the markers sets is implemented by means of a part of one of the waveguides or contains said and/or is produced, directly or indirectly, in the same layer orientation and/or by means of the same mask. This enables an especially uncomplicated manufacture of the optical components and/or of the optical system without additional steps in order to produce the markers.
At least one part of at least one of the marker sets can be applied to one of the optical components or the carrier substrate or may be embedded therein by means of a lithographic process. In this manner, precise production and especially good visibility of the marker sets and/or parts thereof can be achieved.
It may be provided that at least one part of at least one of the marker sets and at least one part of at least one of the waveguides are produced in a common work step and/or by means of a common mask through a lithographic process. This has the advantage that the position and/or the orientation of the marker sets and/or the corresponding parts thereof is defined as relates to the corresponding waveguide with great precision and reproducibility.
At least one of the markers sets may have at least one linear and/or cruciform and/or cruciform and/or elliptical and/or polygonal element and/or several parallel lines and/or a vernier structure.
Linear elements and/or combinations thereof (which thus comprises cruciform and polygonal elements—and/or edges thereof—or vernier structures) are advantageous. Sets of several parallel linear elements can be considered especially advantageous. Linear elements of a marker set may extend parallel to the corresponding waveguides at a fixed distance/fixed distances away and thus enable an especially good alignment of the waveguides with respect to one another.
The aforementioned advantages take effect in the frequently encountered situation in which a waveguide in the vicinity of the end surface of an optical component—and particularly at the entry and/or exit point of the waveguide on the end surface—is not parallel to the end surface but instead meets it at an angle of more or less than 90°. Thus, undesired back-reflections of light, for example in laser cavities, can be avoided. In this situation, the precise position of the entry and/or exit point depends on how much material has been removed during polishing or refraction of the end surface (see above). If a linear element of a marker set extends parallel to the waveguide, the linear element will be shortened the same as the waveguide, and the point of intersection between the linear element and the end surface will change in the same manner as the entry and/or exit point of the waveguide.
In addition, a necessary offset of the optical components, which can be defined, for example, by the refractive indices of the associated waveguides and the distance between the corresponding end surfaces, can be set by means of the positions and/or orientations of the linear elements.
It may be provided that end surfaces, facing one another, of the first end of the second element have a distance, for example, of less than 100 μm, less than 10 μm, less than 1 μm, or less than 100 nm at the end of the method—i.e. particularly after the alignment of the components with respect to one another and the arrangement of both components on the carrier substrate.
It may be provided that the first and the second marker set and/or the second and third marker set supplement one another and/or engage one another and/or are complementary to one another in order to facilitate an alignment. This may occur, for example, in the case of simple linear elements or, for example, in the case of vernier structures, which are known to enable an especially precise determination of the position deviation. For example, parts of the first and/or second and/or marker set may each result in the read-off and main scale of a vernier structure.
It may be provided that at least one of the marker sets comprises several markers at a distance which is as large as possible (i.e. as large as possible according to the scale of the dimension of the corresponding optical component and/or of the carrier substrate and the arrangement of other elements thereupon). A greater distance between elements enables more precise determination of deviations in the position and/orientation of optical components and/or of the carrier substrate from the desired position.
It may be provided that at least a part of at least one of the marker sets extends from an end surface of the corresponding optical component and/or of the carrier substrate to another edge and/or that at least one of the marker sets comprises elements in the vicinity of several end surfaces. On the one hand, the accuracy of the determination of position/orientation deviations is also hereby improved; on the other hand, the course of a waveguide in the vicinity of several end surfaces can be considered, particularly when optical couplings are to be achieved on several end surfaces.
It should also be generally considered that each marker set must contain at least one discernible point, which is different from the other points, for each independent degree of freedom (displacement, angle tilt) to be considered during alignment of the optical elements with respect to one another. With linear or otherwise extended, i.e. not pointy, elements, this can be provided by several defined points of such elements (for example end points).
At least one part of at least one of the marker sets may be an edge of one of the optical components or of the carrier substrate or may contain them/it.
Thus, a clear position can be defined with reference to an exit point of said waveguide, namely as the point of intersection between the edge and the linear element, particularly in conjunction with a further part of the same marker set—implemented as a linear element positioned parallel to one of the waveguides.
A corresponding edge of at least one of the optical elements can be marked and thus rendered especially easily visible also by a part of a marker set, which is designed as an extended surface element (i.e., for example, as a polygon, for example as a rectangle).
It may be provided that the carrier substrate and/or at least one of the optical components has an adhesive layer, configured for the temporary and/or permanent attachment of the first and/or second optical component to the carrier substrate. Thus, a robust and flexible attachment option is provided. The adhesive used may consider the requirements of the process for producing or of the proper use of the optical system in many different ways, for example with respect to temperature resistance, thermal conductivity, other thermal or electrical properties, conformity to effective mechanical forces, etc. The adhesive layer can also enable an at least temporary sealing of spaces between the optical components and/or the carrier substrate.
It may be provided that the adhesive layer is structured and/or noncontinuous and/or that the alignment of the first and the second waveguide with respect to one another in the normal direction comprises at least partial deformation of the adhesive layer.
A structured and/or noncontinuous adhesive layer comprises several discrete adhesive elements, which can be achieved, for example, by means of lithographic processing of a continuous adhesive layer. Such an adhesive layer especially provides a great amount of flexibility and can be adapted to the method and/or usage requirements in an advantageous manner with respect to the structure size/density/surface configuration of the adhesive.
To this end, the adhesive elements may be shaped in different ways, for example as points, rectangles, polygons, rings, or linear elements. The adhesive elements may be superposed over further elements of the surface of the optical components and/or of the carrier substrate—for example of a structured metal layer serving as a part of a marker set—or arranged in the intermediate spaces thereof.
An alignment of the first and second waveguide with respect to one another in the normal direction with at least partial deformation of the adhesive layer can be implemented, for example, such that structured metal layers on the front sides of the optical components and of the carrier substrate serve as reference surfaces for alignment in the normal direction, and the adhesive elements of the structured adhesive layer are arranged in the intermediate spaces of the structured metal layer. If the adhesive elements are thicker than the structured metal layer, they are deformed when the optical component(s) are pressed together with the carrier substrate, whereby a stable adhesion is achieved and combined with the advantages of the structured metal layer with respect to the alignment in the normal direction.
The structuring of the adhesive layer in discrete, size-defined adhesive elements of selectable shape enables an adaptation and/or optimization of parameters of the manufacturing process, particularly with respect to the bonding surface/layout of the optical component(s) and/or the required bonding force (press-on force during attachment) and/or the required degree of deformation of the adhesive layer for the alignment of the optical component(s). A maximized degree of deformation (i.e. “flattening”) of the thin adhesive layer can therefore also be achieved more reliably, which enables a more robust processing window and/or an increased reproducibility of the manufacturing process.
The proposed carrier substrate has a marker set and is configured to be applied with an optical component, having a waveguide and a marker set with a defined position and/orientation with respect to the waveguide such that, by means of a relative position and/or orientation of at least two of the marker sets, it can be determined whether a desired alignment of the waveguide has been established with respect to the carrier substrate in the reference plane.
The thusly obtained carrier substrate is advantageously to be used during production of the proposed optical system.
The proposed method for producing an optical system comprises:
The method has the advantage that the detection of the relative position and/or orientation of the first optical component and of the carrier substrate with respect one another—preferably during the production of the optical system—enables an alignment of the first optical component and of the carrier substrate with respect one another with great accuracy in a manner that is comparatively simple to implement and is economical (namely by means of possible correcting of a relative position and/or orientation of the first and optical component and of the carrier substrate).
Thus, the system can also be prepared for the arranging of a second optical component with a second waveguide on the carrier substrate, wherein the first and the second waveguides can then be optically coupled together. In particular, the known advantages of passive alignment are achieved with simultaneous easing of the production tolerances.
During arranging of the first and second optical component on the carrier substrate, initially the first optical component, for example, can be arranged on the carrier substrate such that its front side is facing the front side of the carrier substrate. In this case, the first optical component can be aligned with respect to the carrier substrate with the assistance of a suitable measuring device, which enables the determining of a relative position and/or orientation at least of parts of the first and second marker set. At the same time or subsequently, the first optical component can be temporarily or permanently attached to the carrier substrate, for example by means of an adhesive applied to the carrier substrate and/or to the first optical component.
The second optical component can thus be guided to the back side of the first optical component such that the front side of the first optical component is likewise facing the front side of the carrier substrate, but that there is still a distance between first and second component, which enables a determining of a relative position and/or orientation at least of parts of the second and third marker set by means of the measuring device. This can occur, for example, in optical ways, for example by recording images using at least one camera. A position and/or orientation of the second optical component and/or of the first optical component, including the carrier substrate, can thus be corrected according to the determined relative position and/or orientation such that thereby an alignment of the first and second waveguide with respect to one another is enabled, particularly in the lateral directions.
After the correcting is complete, the determining of the relative position and/or orientation of the optical components can be repeated—optionally multiple times, i.e. iteratively—until a desired tolerance of the relative position and/or orientation of the first and second waveguide is achieved or values are within the tolerance, in order to check and/or correct the position and/or orientation of the first and/or second component. The second optical component can be arranged on the carrier substrate while retaining the alignment and likewise be temporarily or permanently attached, for example by means of an adhesive applied to the carrier substrate and/or to the second optical component. In this case, the first optical component can be arranged in the recess of the second optical component.
Alternatively, initially the second optical component can be arranged on the carrier substrate, and moreover can be moved similarly as above, during arrangement of the first and second optical component on the carrier substrate—provided the recess passes completely through the second optical component—wherein, however, the steps which relate to the first or second optical component, respectively, are correspondingly reversed or modified.
The described checking and/or correcting of the relative position and/or orientation of the first and second waveguide can also be used to reject workpieces in which a desired tolerance was not achieved or can also be used to improve the method iteratively, for example by adapting correction factors.
It may be provided that the first waveguide has a distance from the front side of the first optical component, that the second waveguide has a second distance from a front side of the second optical component, that the first and second optical components are facing the carrier substrate during arrangement of the first and second optical component on the carrier substrate, and that the alignment of the first and second optical component with respect to one another comprises the following:
setting of the first and second distance in order to align the first and second waveguide with respect to one another in a normal direction perpendicular to the reference plane.
The setting of the first and second distance may further comprise an application of layers to the front side of the first and/or second optical component, wherein, for example, the previously mentioned layer deposition processes can be used, e.g. epitaxy or PECVD.
The method may comprise a removal of the carrier substrate from the at least one optical component after alignment of the at least one optical component with respect to the carrier substrate.
Thus, the flexibility is increased for further processing steps.
The optical system can optionally be further developed in different ways which are customary for the processing of corresponding systems. This may comprise, for example, a filling of the remaining gaps between the optical components with suitable filling materials and/or thinning of surfaces and/or applying electrical contacting.
The method can be implemented with the assistance of typical systems and devices for producing electronic, optical, or electro-optical components and systems, for example by means of a flip chip bonder.
It should be mentioned that the aforementioned steps and sub-steps of the method do not have to be executed in a particular sequence, rather the sequence can be established depending on specific modalities.
Exemplary embodiments of the disclosure are explained in the following by means of
Repeating and similar features of various examples and embodiments are indicated in the following with the same reference numerals.
The optical system 400 shown in cross-section in
The first optical component 100 has a first waveguide 101, which is formed between a first substrate layer 102 and a second substrate layer 103, wherein the substrate layers, 102 and 103, are implemented in a III/V material system and/or semiconductor material system. The first substrate layer 102 is arranged on a front side 104 of the first optical component 100, and the second substrate layer 103 is arranged on a back side 105 of the first optical component 100, said back side being opposite the front side 104. The first waveguide 101 exits into end surfaces 109 of the first optical component 100, which is perpendicular to the front side 104.
The first optical component 100 is attached to a glass wafer which serves as the carrier substrate 300 and which is transparent for ultraviolet, visible, and infrared wavelengths (for example, a wavelength range of from 200 nm to 1200 nm or also only for subranges, for example of 400 to 800 nm) by means of an adhesive layer 301. The carrier substrate 300 has a front side 304 facing the first optical component 100 and a back side 305 opposite the front side 304.
The first optical component 100 has a first marker set 110 with a defined position and orientation with respect to the first waveguide 101, and the carrier substrate 300 has a second marker set 310. As explained further below, it can be determined whether a desired alignment of the first waveguide 101 with respect to the carrier substrate 300 is produced in a reference plane parallel to a surface of the carrier substrate 300 by means of a relative position and/or orientation of the first and second marker set, 110 and 310.
The second optical component 200 shown in cross-section in
The SiO2 layer 202 is arranged on a front side 204 of the second optical component 200, and the silicon layer 203 is arranged on a back side 205 of the second optical component 200, said back side being opposite the front side 204. The second waveguide 201 exits into end surfaces 209 of the second optical component 200, which is perpendicular to the front side 204.
Those end surfaces 209, at which the second waveguide 201 is intended to be optically coupled to the first waveguide 101, are prepared through mechanical polishing or through lithographically defined dry etching or through targeted local dry etching. Alternatively, the end surfaces 209 can be prepared, for example, through refraction along defined crystal surfaces.
Layers 101 and 202 on the front side are prepared through depositing processes such that precisely defined layer thicknesses result.
The second optical component 200 has a recess 206, which partially extends through the second optical component 200 from the front side 204 in the direction of the back side 205. Alternatively, it can also pass completely through the second optical component 200. The recess 206 can also be omitted. In this case, the optical components, 100 and 200, are arranged next to one another instead of within one another.
The second optical component 200 has a third marker set 210 with a defined position and/or orientation with respect to the second waveguide 210.
The optical components, 100 and 200, as well as the carrier substrate 300 may also be formed in different ways and/or from different materials as previously described by example. For example, at least one of optical components 100 and 200 may have a semiconductor chip (e.g. a silicon chip), a photonic integrated circuit (PIC), a silicon-on-insulator chip, a ceramic chip, and/or a glass chip. Furthermore, the carrier substrate 300 may contain materials such as silicon or other semiconductor materials, ceramics, glass, or polymer or consist thereof. At least one of the waveguides, 101 and 201, may contain a polymer, a glass, an oxide (e.g. SiO2), a nitride (e.g. Si3N4 in SiO2), and/or silicon (e.g. as Si on Si02).
The further exemplary embodiment of an optical system 400 shown in a top view in
The first optical component 100 has a first marker set 110 with a defined position and orientation with respect to the first waveguide 101. The carrier substrate 300 has a second marker set 310. The second optical component 200 has a third marker set 210 with a defined position and orientation with respect to the second waveguide 201. By means of a relative position and orientation of pairs (110/310, 210/310, 110/210) of the marker sets, it can be determined whether the first and second optical component, 100 and 200, are aligned with respect to one another in the reference plane such that an optical coupling is enabled between the first and second waveguide, 101 and 201.
To this end, the third marker set 210 has a first part, which is formed from linear elements extending parallel to the second waveguide 201 and at fixed distances, and a second part, which is formed from linear, square, and cruciform elements, which are complementary to a first part of the second marker set 310. Complementary in this case means that elements of the corresponding parts of both marker sets, 210 and 310, supplement one another and/or have boundary lines parallel to one another due to super-position into contiguous shapes, when a desired relative alignment is present.
In a corresponding manner, the first marker set 110 also has a first part, which is formed from linear elements extending parallel to the first waveguide 101 and at fixed distances, and a second part, which is formed from linear, square, and cruciform elements, which are complementary to a second part of the second marker set 310.
The marker sets 110, 210, 310 may also, of course, be structured differently, for example at least one of them may have at least one round and/or elliptical and/or polygonal, e.g. rectangular, element and/or a vernier structure. The edges, which are formed by the optical components, 100 and 200, at the end surfaces, 109 and 209, in the region of the markers sets, 110 and 210, can be considered part of the markers sets, because they have defined points of intersection with the linear elements of the vernier structures.
The marker sets, 110, 210, and 310, are implemented as structured metal layers, which are applied to the front sides, 104, 204, and 304. The markers sets 110, 210, 310 may also be implemented in a different manner; for example, markers sets 110 and 210 can be produced with the respective waveguides, 101 and 201, each in a common work step, and by means of a common mask, due to a lithographic process, i.e. can be embedded in the optical components, 100 and 200, in the same plane as the waveguides, 101 and 201. Furthermore, the waveguides, 101 and 201, themselves can serve as marker sets or parts of markers sets, provided they are readily visible.
The adhesive layer 301 is implemented as a structured adhesive layer. Alternatively, it can be implemented also as a continuous layer.
Exemplary steps of the method for producing the optical system 400 are described in the following by means of
Subsequently, an adhesive layer 301 is applied (
The flip chip bonder 600 comprises: a lower component carrier or chuck 601, an upper component carrier or bonding arm 602, a turning carrier or flip arm 603, and a camera system 604.
The chuck 601 is configured for retaining and/or three-dimensionally moving a structural element on a side facing the bonding arm 602. The bonding arm 602 is configured for retaining and/or three-dimensionally moving a structural element on a side facing the chuck 601. The flip arm 603 is configured to accommodate a structural element and/or to turn it 180° and/or to transfer it to the chuck 601 or to the bonding arm 602. The camera system 604 may be arranged between the chuck 601 and the bonding arm 602 and is configured to simultaneously depict a part of a structural element retained by the chuck 601 and a part of a structural element retained by the bonding arm 602 (depiction directions are indicated by arrows), which can also be achieved, for example, by means of two lenses in conjunction with two sensors or one sensor and one optical splitter.
In the method step shown in
At the same time, a part of the first marker set 110 and a part of the second marker set 310 are depicted by means of the camera unit 604, which enables a detecting of a relative position and orientation of the first optical component 100 and of the carrier substrate 300, or more precisely of a deviation from a desired relative position and orientation. Due to the movement of the chuck 601 and/or the bonding arm 602, the first optical component 100 and the carrier substrate 300 are then aligned with respect to one another (indicated by dashed lines).
As shown in
At this point, the mounting of the first optical component 100 on the carrier substrate 300 can be further evaluated in a control step. By means of the optically transparent carrier substrate 300, the relative positions and/or orientations of the first optical component 100, the second optical component 200, and the carrier substrate 300 can be detected, after removal of the bonding arm 602, through the detecting of parts of the marker sets 110, 210, 310 by means of the camera unit 604.
The carrier substrate 300 with the first optical component 100 thereupon is turned by means of the flip arm 603 and transferred to the bonding arm 602. The second optical component 200 is then placed on the chuck 601, wherein the front side 204 of said component is facing the front side 304 of the carrier substrate 300 and the back side 105 of the first optical component 100 arranged thereupon.
The thusly produced situation is shown in
As shown in
By means of the optically transparent carrier substrate 300, the relative positions and orientations of the first optical component 100, the second optical component 200, and the carrier substrate 300 can be detected, after removal of the bonding arm 602, through the detecting of parts of the marker sets 110, 210, 310 by means of the camera unit 604. The result of the alignment can hereby be checked; if the accuracy of the alignment is outside of a specified tolerance, the preceding method steps may optionally be repeated, or the workpiece can be rejected.
It should be mentioned that individual or all method steps can also, of course, be executed in a different manner or in a different sequence. For example, initially the second optical component 200 can be arranged and aligned on the carrier substrate 300, and subsequently the first optical component 100 can be placed in the recess 206 of the second optical component 200, provided the recess 206 passes completely through the second optical component 200.
Because the waveguides, 101 and 201, are thus precisely aligned both laterally and also normally with respect to one another, an optical coupling of the waveguides, 101 and 201, is established.
As shown in
In addition, as shown in
Subsequently, gaps remaining between the optical components, 100 and 200, can be filled with a potting compound 405. The carrier substrate 300 and/or the sub-carrier 403 can be removed, for example, by means of laser debonding or grinding. The (cured) potting compound 405, the silicon layer 203, and the sacrificial structure 402 can be thinned by grinding down to a common back side 406.
As shown in
Of course, the number, type, and sequence of the steps of the method can be adapted, as is directly clear to one skilled in the art (particularly with respect to the optical system to be produced and/or the properties of the optical components used).
100 First optical component
101 First waveguide
102 First substrate layer
103 Second substrate layer
104 Front side
105 Rear side
109 End face
110 First markup set
200 Second optical component
201 Second waveguide
202 SiO2 layer
203 Silicon layer
204 Front side
205 Rear side
206 Recess
209 End face
210 Second markup set
220 Mask
221 Trenches
222 Core
300 Carrier substrate
301 Adhesive layer
302 Adhesive structures
304 Front side
305 Rear side
310 Second markup set
311 Metal layer
320 Polymer layer
321 Carrier substrate waveguide
400 Optical system
402 Sacrificial structure
403 Auxiliary carrier
404 Optical filler material
405 Casting compound
406 Rear side
407 Front side
408 Thin film multilayer wiring
409 Bumps
410 Recess
500 Carrier
600 Flip chip bonder
601 Chuck
602 Bond arm
603 Flip arm
604 Camera system
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 210 745.1 | Jul 2019 | DE | national |
| 10 2019 211 002.9 | Jul 2019 | DE | national |
