Patent Application
20160237555
Various methods are used when processing surfaces, for instance when coats of thin layers are applied or the surface is removed. Methods of physical or chemical vapor deposition are of particular importance with regard to coating. Sputtering, in which particles are removed from a target material via particle bombardment and then deposited on the surface to be coated, is frequently used for coating surfaces in the semiconductor, solar-cell and optical industries. Ion-beam etching or plasma etching methods, as examples, are used for surface removal.
The above-mentioned methods of surface processing customarily take place in a vacuum or in specific gas atmospheres. It is problematic under these conditions when the technology requires frequently changing processing methods or methods that only involve a low level of continuity of processing quality. Normally, the substrates to be processed in cases of this type are moved through a gate from one processing machine into a subsequent processing machine in which the subsequent processing step is then carried out. Movement processes of this type through a gate always involve handling problems, in particular when there are very large and heavy substrates, or problems based on the vacuum conditions.
In particular, when surfaces are coated with thin layers, the quality and uniformity of these layers forming the coating are important. More than 1000 layers are applied in part in coatings in modern applications. The coating technology has to therefore be carried out with the highest possible quality and repeatability. The structuring of these coating layers, in particular the measurement and rework of layers required within the framework of quality assurance, is to also be realized in a reliable way.
Ion-supported technology is also used both for the application and for the rework of the layers. It is therefore frequently possible to carry out technologies that require analog vacuum conditions (pressure, temperature, possibly certain gas components) in a common vacuum chamber. So-called wafer carousels (for instance U.S. Pat. No. 6,949,177 B2) are known from the semiconductor industry in which similar wafers are transported in a rotatory manner from one processing station to the next. Systems of that type are very effective when the processing of a multitude of similar, relatively small substrates is involved. They are hardly suitable, however, when large substrates have to be processed. The suitability of these devices is also questionable for individual production or production in small series.
A method and a device for carrying out the method for processing surfaces of workpieces, preferably of large substrates, are presented. The intent is to arrange the processing devices on the casing of a drum-type carrier in a vacuum chamber. The workpiece is transported over the drum and optionally made to rotate. The drum-type carriers is rotated in such a way that the intended processing device is turned towards the workpiece and can process it. The surface section to be processed can be selected via translation and rotation.
The problem of proposing a design that is suitable for processing large substrates, in particular, using ion-beam and plasma technologies therefore arises.
The problem is solved as per the invention with the device according to claim 1. A method using the device as per the invention is described in claim 13. Advantageous embodiments are presented in the dependent sub-claims.
At least the following steps are carried out in the method as per the invention for processing surfaces of workpieces, in particular substrates with several processing layers in a vacuum chamber with a carrier drum (preferably a cylindrical body) that has a number of processing devices:
The processing system has a large vacuum chamber, preferably with an air lock in front of it. The workpiece preferably involves a large substrate. Workpieces that weigh more than 10 kg during the processing, preferably more than 100 kg, are regarded as large substrates. The workpiece is preferably attached to a holding element that makes the workpiece accessible to an uptake by a machine during the processing. When movement of the workpiece is discussed below, this refers to the movement of the workpiece via this holding element as a preference. The design of holding elements of this type is known in the prior art. The work piece is fed into the vacuum chamber (preferably through an air lock). In the vacuum chamber, it is preferably transported, hanging on a suspension element, in horizontal and vertical directions. The suspension element is preferably moved via a linear motor. Preferred supported movement is also possible, however, in which the carrier drum is arranged above the workpiece or on the side of the workpiece. The suspension element is preferably fastened in a movable and drivable way on a horizontal carrier that sets the direction of the main axis. The workpiece can preferably also be rotated around a vertical axis during the horizontal movement. The rotation of the workpiece is preferably realized via a motor that is likewise integrated into the suspension element on the transport device. This motor (including an optional transmission and auxiliary devices) is preferably arranged in a gas-tight enclosure. This gas-tight enclosure preferably has one (optionally two) supply units running in parallel with the main axis of motion. As a special preference, the supply unit or supply units are realized in the form of rigid, hollow rods (tubes) that lead through and out of a vacuum feedthrough (preferably a bellows-type membrane seal) in the wall of the vacuum chamber. The supply units can be moved along their longitudinal axis in the vacuum feedthrough. They can follow the movement of the suspension element on the transport device along the main axis of movement in this way or, as the case may be, this movement can also be initiated and controlled via the rigid supply units. A suitable linear drive unit is provided for this on the outside of the vacuum chamber. Transfers of energy, data and process utilities can advantageously be made through the inner hollow area of the supply unit. In a further preferred embodiment, a motor for bringing about the rotation of the workpiece is not provided in the suspension element, but instead merely a gearbox that transfers rotary movement provided through the interior of the of the supply unit via a shaft or a hydraulic connection.
The carrier drum is preferably arranged below the suspended workpiece. The carrier drum is preferably designed in the form of a cylindrical, hollow body with a casing and two top faces. The workpiece is moved along the main axis over the active processing device in the operating position and is thereby processed. In a preferred embodiment, the speed along the main axis is varied to create processing profiles. In a further preferred embodiment, the distance at which the workpiece is moved past the carrier drum varies in dependence upon the processing device in the operating position. If uniform processing is required, the workpiece to be processed is optionally put into rotation in an advantageous manner. The rotary speed can be varied or kept constant as required.
The processing devices are either arranged on or in the casing here, or they are arranged on or in a top face of the carrier drum. The carrier drum has a central axis around which it is rotated in order to put the desired processing device into the operating position. If the processing devices are arranged in the casing, the central axis of the carrier drum is aligned in such a way that it is in a plane that is perpendicular to the axis of rotation of the workpiece. If the processing devices are arranged in a top face of the carrier drum, the central axis of the carrier drum will preferably run in parallel with the axis of rotation of the workpiece. In addition to the preferred embodiments, any position of the carrier drum with respect to the workpiece is possible in principle with an arrangement of the carrier drum below or above the workpiece.
Similar or different processing devices can be arranged as processing devices on the carrier drum. Different ion-beam sources, plasma sources and magnetrons can be arranged, as examples, on the drum. Both processing devices for applying material, for instance magnetrons, and processing devices for removing material, for instance with ion-beam etching or plasma etching, can be jointly arranged on a carrier drum in a preferred embodiment. Processing devices in this context are also understood to mean measurement or monitoring apparatus that is suitable for investigating the surface condition of the workpiece and, for instance, for determining the requirements or success of the processing. Optical measurement devices such as microscopes, spectroscopes, interferometers or laser measurement devices, as examples, are devices of that type. The carrier drum will preferably have at least two or, as a further preference, three, four, five or six processing devices. Eight processing devices are also preferred, however. The maximum number of processing devices is only established by the spatial and technical boundary conditions. As a very special preference, all of the processing devices are magnetrons.
The carrier drum is rotatably supported on at least one side, preferably on both sides; the support preferably has a hollow shaft on at least one side through which flexible supply lines can be routed to supply electrical power, provide a data connection, supply gas and, if necessary, provide a high-frequency feed for the processing devices. In a preferred embodiment, one or more of the processing devices also have their own control possibilities available both with regard to the operating process and with regard to the spatial orientation. This preferably applies to ion-beam sources and measurement devices that can be provided, for example, with their own gimbal-mounted suspension element or a suspension element operating in a similar fashion. The carrier drum is rotated via a drive unit in such a way that the intended processing devices is turned towards the surface to be processed. The processing device is therefore in the operating position.
In a preferred embodiment, the vacuum chamber has one or more further processing, measurement or inspection devices via which the workpiece can be positioned and optionally rotated. These processing, measurement or inspection devices involve, for instance, ion-beam sources, electrical or optical microscopes, electron-beam sources, cameras etc. These devices are not arranged on the carrier drum.
The method as per the invention will be explained below with an example of the preferred use of magnetrons as the processing devices and a substrate as the workpiece.
Magnetrons or simple cathode sputtering sources are frequently used to generate the particles that remove particles from a target material. The magnetron or cathode sputtering source has a cathode that is attached to the material to be bombarded. This is preferably done with the aid of a so-called target. Whereas only an electric field is created at the cathode in the case of simple cathode sputtering sources, an additional magnetic field is brought about behind the cathode plate in the case of the magnetron. A plasma is created in the gas-filled space in front of the cathode when an electric field is created. The ions of the plasma that are created are accelerated in the electric field and remove particles from a target material (target) that are deposited on the surface to be coated. DC voltages, pulsed DC voltages or low-frequency or high-frequency alternating fields are possibilities as electrical fields. Noble gases such as argon or krypton are preferably used as gases. Other gases can also be added to the gas, though, that react with the surface to be coated with the particles that are being deposited and thereby form compound layers (reactive sputtering). As an example, a layer of TiO2 can be created on the surface to be coated via the use of titanium as the target material and the addition of O2 to the gas.
When a magnetron is used, it is slowly exhausted because of the continued removal of the target material or, as the case may be, the characteristics of the sputtering process change because the geometry of the magnetron has changed in this way. Consequently, a replacement of the magnetron or at least the replacement of the target material would be necessary during processing.
There are a number of approaches for handling this problem in the prior art. U.S. Pat. Nos. 4,356,073 and 5,213,672 describe approaches of this type. Rotating target material is used in the process. This ensures that the target material is evenly removed over the entire rotation body and that local overheating does not come about. This approach does in fact ensure an increase in the useful life of the target, but it can only delay final exhaustion.
EP 0 543 844 B1 presents a design in which the entire magnetron rotates. The substrate to be coated is moved past the cathode of the magnetron and coated in the process. The design of a rotating magnetron was perfected in DE 10 2009 053 756.2, for example, where periodically occurring, design-related fluctuations based on slight irregularities in the cylindrical form of the magnetron are to be balanced out with a variation of the target voltage. The rotating magnetrons obviously also do not have a sufficient useful target life and process stability.
The method as per the invention provides, within the framework of the preferred embodiment here, for the use of a plurality of magnetrons that are arranged on the rotatable cylindrical carrier drum; at least one magnetron is started up and put into an operating position for this, as the active magnetron, relative to an object to be coated. The object to be processed (the substrate) is preferably moved with respect to the magnetron in such a way that the entire area that is supposed to get a coating gets one. If a plurality of coatings are required, a corresponding plurality of coating processes will be advantageously carried out. The coating processes can be carried out with one and the same magnetron in the process, or the active magnetron is replaced after the conclusion of a coating process. The magnetrons can be advantageously exchanged in that way before their coating characteristics change or the target material is exhausted. Since the carrier drum is housed in a vacuum together with the substrate to be coated, ventilation or air-lock processes are not necessary when the active magnetron is changed. So the coating process, even of large substrates, can be concluded before it is necessary to replace the target. In addition to a significant acceleration of the coating process, this also leads to an increase in quality because the coating conditions in the vacuum do not change.
Since the carrier drum is exclusively equipped with magnetrons in this example, it will be called a magnetron drum below. A first preferred embodiment provides for a magnetron drum that has a horizontally supported cylindrical body. The magnetrons are preferably rod-shaped and in parallel with the axis of rotation of the cylindrical body and arranged on or in its casing. The rod-shaped magnetrons are at least as long as the maximum width to be coated of the substrate to be coated. The magnetrons preferably have rod-shaped target material here that can preferably be manipulated separately from the magnetron, in particular exchanged, as a component that has the approximate overall length of the magnetron. The magnetrons can be identical with regard to both the design and the target material, or they can be different, for instance having different target materials, to be able to create coating layers made of different materials. Further magnetron designs, preferably rotating linear magnetrons, preferably with tube cathodes, are also possible. The magnetron drum is rotatably supported on at least one side, preferably on both sides; the support preferably has a hollow shaft on at least one side through which flexible supply lines can be arranged to supply electrical power, supply gas and, if necessary, provide a high-frequency feed for the magnetrons. The magnetron drum is rotated via a drive unit in such a way that the intended magnetron is turned towards the surface to be coated. The magnetron is therefore in the operating position.
A preferred embodiment provides for the capability of also starting up magnetrons that are not in the operating position so that a break-in process up to stable operation can be carried out. Studies have shown that the break-in process of the magnetrons is dependent upon the pressure conditions and also upon the geometric conditions, in particular the distance of the area to be coated to the magnetron. To bring the magnetrons up to an operating state corresponding to the operating state in the operating position, the invention envisages that the distance to the enclosure (wall) of the magnetron drum of the magnetrons that are not in the operating position will correspond to the distance that the magnetron will have in the operating position to the surface of the substrate to be coated. The deviation of the distance of the magnetron that is not in the operating position to the distance that the magnetron in the operating position has to the surface of the substrate to be coated is preferably less than 25%, with a special preference for less than 15% and a very special preference for less than 5%. Since the same geometric conditions exist both for magnetrons that are in the operating position and for those in positions that are not operating positions, a break-in process is possible that stabilizes the magnetrons in the operating state, which is favorable for a coating operation. In an especially preferred embodiment, the vacuum conditions for the magnetrons outside of the operating position are likewise matched to those in the operating position. The enclosure of the magnetron has one or more gas exhaust systems for this that extract the gas given off by the magnetrons outside of the operating position and the vacuum conditions are matched in that way to those in the vacuum chamber in which the substrate is coated. The gas exhaust systems are arranged in such a way that the gas flow corresponds to the gas flow that acts upon the magnetron in the operating position. In particular, the pressure difference between the vacuum chamber and the enclosure of the magnetron is less than 10%, less than 5% as a special preference and less than 2.5% as a very special preference.
In a preferred embodiment, each magnetron has its own fixed or detachable supply lines. In a further preferred embodiment, there are one or more automatic connections to supply lines via which both the magnetron that moved into the operating position and also magnetrons in other positions can be connected in a detachable way.
As a preference, the rotary direction of the magnetron drum is always chosen in such a way that a twisting of supply lines is minimized during the positioning of the magnetron.
The horizontally supported magnetron drum is preferably used in a system for coating large-sized substrates. The system has a large vacuum chamber for this with an air lock in front of it. The substrate to be processed is fed into the vacuum chamber through the air lock. The feed-in preferably takes place on the side, directly under the suspension element, so that only a slight push is necessary to connect the workpiece to the suspension element. In the vacuum chamber, it is preferably transported, hanging on the suspension element, in horizontal and optionally vertical directions. The suspension element is fastened in a movable and drivable way to a horizontal carrier. The substrate can preferably also be rotated around a vertical axis during the horizontal movement. The magnetron drum is preferably arranged below the hanging substrate. The component is moved along the main axis over the active magnetron in the operating position and thereby receives a coating layer. In a preferred embodiment, the speed along the main axis is varied to create defined coating profiles. If uniform coating layers are required, the substrate to be processed is optionally made to rotate in an advantageous way. The rotary speed can be varied or kept constant as required.
Once a layer has been completely applied, the direction of motion along the main axis is reversed and the substrate is coated once again if necessary. The magnetron that was previously in the operating position can be used for this or, if the target material has to be changed or if a different coating material is required, a different magnetron can be put into the operating position via rotation of the magnetron drum. The selected magnetron can already be started up beforehand or can be first started up in the operating position. A further coating layer can now be provided via movement along the main axis and optionally via rotation of the substrate. This is continued until the desired layer structure of the coating is achieved or until a functional magnetron with the required layer material is no longer available. The substrate is output out of the vacuum chamber through an air lock when the coating process is complete.
In a preferred embodiment, the carrier drum is arranged in an enclosure. The drum has an opening for the intended processing device through which it can process the surface of the workpiece. It has been show, in particular when magnetrons are used, that the existence of the workpiece in front of the magnetron can lead to different plasma characteristics. An effort is made, however, to always have a stable plasma available for processing. The enclosure is therefore preferably arranged at a distance to the plasma sources that corresponds to that of the workpiece in the processing position. There is only an adjustment of the distance of the enclosure in the area of the opening for the intended processing device, so the processing devices can be brought into the processing position without making contact with the enclosure, but the workpiece can also be moved without making contact with the enclosure. The enclosure preferably has its own gas exhaust system. This gas exhaust system ensures that gas-pressure conditions or gas compositions that have to later be achieved in the operating position prevail in the enclosure and in front of the respective magnetrons. Since the magnetrons are also in operation when they are not in the processing position, in order to be in a stable operating state, the gas that is used (usually argon) is to be extracted in a defined manner. This is also preferably realized by the gas exhaust system. The enclosure also preferably has the gas-supply devices. A “cross flow” known to persons skilled in the art can advantageously be realized over each magnetron in that way. The gas extraction and supply can take place through the hollow axle of the carrier drum, for instance. Other preferred embodiments provide for the carrier drum to have openings in one or both of their cylindrical faces that are congruent in the processing positions with suction openings of the gas exhaust system and that are covered up by the bearings of the carrier drum during the rotation process. An analogous approach can be taken with regard to the gas supply.
Adjustment devices (match boxes) are usually used to match the output between the HF generator and the magnetron when high-frequency alternating voltages are utilized. They are preferably located in the carrier drum. This advantageously shortens the length of the required transmission lines to the coupling point or the several coupling points of each magnetron. The match boxes for this are preferably arranged in their own vacuum-tight containers. The containers of the match boxes can be filled with air or advantageously with a protective gas (for instance dry nitrogen).
In a simple, preferred embodiment, the processing devices, for instance the magnetrons or more specifically their target material, are replaced during the standstill periods of the device. The vacuum chamber preferably has a maintenance door for that. A further preferred embodiment provides for the possibility, however, of replacing the magnetron whose target material is exhausted in situ. To this end, the magnetron drum is rotated into a position in which the magnetron to be maintained is rotated out of the operating position into a replacement position. The replacement position of the magnetron drum is preferably opposite the operating position. It is possible in this position to dock an air-lock device on the magnetron drum that permits the replacement of the target material. A first embodiment provides for the exhausted target material to be pulled out at the face of the magnetron drum, put into intermediate storage in the air lock and then removed. The new target material is likewise brought in through the air lock, put into the magnetron from the face side and anchored there. The fact that the cross-section of the air-lock opening to be covered is small because the air-lock opening is only somewhat larger than the cross-section of the rod-shaped target material is advantageous with regard to this solution. The target material is preferably done in an automated fashion or with a manipulator that handles the target material in the vacuum.
A further preferred embodiment provides for an air-lock opening that removes the target material perpendicularly to the casing of the magnetron drum. The fact that the system width is not increased by an air-lock device connected beside it is advantageous in connection with this. The target material is also preferably done here in an automated fashion or with a manipulator that handles the target material in the vacuum.
Another preferred embodiment provides for the entire rod-shaped magnetron to be replaced instead of the target material. This embodiment is especially advantageous in connection with the use of supply lines that are connected via automatic connectors to the magnetron in the operating position. A further preferred embodiment provides for the supply lines to be integrated into the faces of the magnetron drum and to be brought there to the magnetrons. A detachable connection to the magnetrons preferably exists in the faces of the magnetron drum.
An advantageous method of operation provides for a magnetron with exhausted target material to be in the replacement position because of the position of the magnetron drum during the operation of the magnetron in the operation position. The target material, or the magnetron with exhausted target material, can then be replaced without interruption of the coating operation. Further required maintenance work on magnetrons of that type is likewise possible.
An especially preferred embodiment provides for the existence of not just one air lock, but instead multiple air locks. These air locks preferably correspond to the positions taken by the magnetrons that are not in the operating position during the coating. Multiple magnetrons can be simultaneously provided with new target material or maintained in that way.
A further preferred embodiment provides for a magnetron drum that has a vertically supported cylindrical body. The magnetrons are arranged in a standing fashion in the form of small, round sputter magnetrons in the magnetron drum. “Round” means here that the magnetrons have a cup-shaped design and are essentially circular in the horizontal cross-section. The coating material leaves at the top from the top face of the magnetron cylinder. The magnetron or magnetrons that are in operation are released by apertures so that the coating material can be output. The other magnetrons are covered by screens. A rotatably mounted screen exists that only releases the one magnetron that is in operation. Unreleased magnetrons can already advantageously be in operation, however, in order to bring about a stabile operating point until they are used. The magnetron drum is rotated around its vertical axis to bring the magnetron that is to be called up for the coating process into the required position. Further rotation can optionally take place during the processing.
The workpiece is preferably, just as in the case of the use of a horizontal magnetron drum, moved past the magnetron along a main axis with optional rotation. The corresponding parameters for translatory and rotary movement of the workpiece were calculated in advance. The fact that layer-thickness profiles can be created on the workpiece that do not have to be rotationally symmetric is advantageous with regard to the vertical magnetron drum. Profiles of that type are advantageous, as an example, in the creation of free-form surfaces or spherical sections with the desired layer-thickness gradients.
The magnetron axle is preferably hollow so that the lines to the magnetrons are also connected through the axle here.
The exhaustion and the replacement of the target material required because of that are also a limiting parameter with regard to the shorter, round magnetrons used here. A preferred embodiment therefore provides for the capability of exchanging the magnetrons from the top face of the magnetron drum that is turned away from the screen. The lines for electrical power, gas and high frequency are connected to the magnetrons in a detachable way for that. If necessary, the lines are detached and an air-lock construction is moved to the magnetron. The magnetron is then removed in its entirety from the magnetron drum, and a replacement magnetron is inserted. After that, the lines are attached again.
The entire system (vacuum system) and the coating process are preferably controlled via a data-processing unit. To this end, sensors exist in the system that also determine, in addition to the position and state of the workpiece, the information regarding the position, operation and wear of the target material and magnetrons, as well as the state of the vacuum in the system etc. These sensors transmit the collected data in a wireless or wired fashion to the data-processing unit, which then evaluates this data and includes the data in the control decisions of the vacuum system. The exchange of the target material and the magnetrons is also controlled, if necessary, by the data-processing unit (or by a further data-processing unit intended to be used for that). In particular, the coating process is calculated in advance (modeled) in the data-processing unit of the vacuum system or in a different data-processing unit, in order to determine the characteristic data such as the required layer thicknesses, the number of layers, the coating times, the distances between the workpiece and the magnetron in the operating position, the feed rate and, if applicable, the rotation speed etc. This data is then, if the calculations have not already taken place there, transmitted to the data-processing unit of the vacuum chamber.
The example in
The air lock (11) has an opening width of 2000 mm×2000 mm with a height of 800 mm. The workpiece (3a) is moved into the vacuum chamber on the rollers of the transport device (5) in the air lock (11) that is open in the direction of the vacuum (33), lifted by the lifting device (115) and automatically coupled to the suspension element. After that, the workpiece (3c) is moved along the main axis of the transport device (2) via a linear drive unit and made to rotate. The magnetrons (41) of the magnetron drum (4) were already started up before the actual processing of the workpiece starts. The magnetron drum is surrounded by an enclosure (44) that has an operating opening with a movable cover (441) in the direction of the workpiece. The enclosure (44) of the magnetron drum (4) has the same distance to the magnetron (41) that the workpiece (3c) will have above the magnetron (41) in the operating position. The magnetrons (41) can therefore already achieve a stable plasma state and do not have to be started up in the operating position. At the same time, the magnetron (41) that contains the material to be applied as the target material is moved into the operating position for the feed-in of the workpiece. Since the magnetrons (41) have already been started up, the magnetron in the operating position immediately achieves stable operation and the workpiece (3c) rotating at 2.00 min−1 is moved past the magnetron (41) at a defined speed profile and at a distance of 60 mm from the target surface of the magnetron. In so doing, the first coating layer is deposited on the surface (32) of the workpiece (3c) to be processed. Typical speed profiles contain speed changes between 0.1 mm/s and 30 mm/s. Linear-motor drive systems are preferably used to be able to achieve these speed changes. The distance between the workpiece and the target surface can be set from approx. 50 mm to approx. 100 mm. As soon as the workpiece (3c) has completely moved over the magnetron (41), its movement is slowed down and reversed. At the same time, the magnetron drum (4) is rotated around its axis (42) in such a way that the next magnetron (41) that has been started up will now reach the operating position. The next magnetron (41) now applies the subsequent coating layer in an analogous fashion while the rotating workpiece (3c) moves over it.
The enclosure has an octagonal design in
The magnetron drum (4) is designed as an axle with arms that support the magnetrons (41) in
The embodiment according to
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The embodiment according to
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2013 221 680.7 | Oct 2013 | DE | national |
This application is the U.S. national stage of International Application No. PCT/EP2014/072762, filed on Oct. 23, 2014, and claims the priority thereof. The international application claims the priority of German Application No. DE 102013221680.7 filed on Oct. 24, 2013; all applications are incorporated by reference herein in their entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/072762 | 10/23/2014 | WO | 00 |
