Apparatus and process for producing thin layers

Abstract

In an apparatus for producing thin layers on substrates for solar cell production, wherein the thin layers are applied by an APCVD process at temperatures of more than 250 C., the substrates are conveyed on a horizontal conveyor path and coated by means of an APCVD coating in continuous operation. The conveyor path has conveyor rollers, which consist of a temperature-resistant, non-metallic material, preferably of ceramic. A heating device and/or a purge gas feeding device is/are arranged on that side of the conveyor path which is remote from the coating apparatus.

Claims

1. An apparatus for producing thin layers on substrates, in particular for solar cell production, comprising: an APCVD coating apparatus for applying the thin layers by means of an APCVD process, said APCVD coating apparatus comprising an injector; a horizontal conveyor path having conveyor rollers, which consist of a temperature-resistant, non-metallic material, for conveying the substrates in continuous operation, where the substrates are laid on the conveyor rollers with conveying contact, and a heating device and a purge gas feeding device, which are arranged on that side of the conveyor path which is remote from the APCVD coating apparatus and on that side of the conveyor rollers which is remote from the APCVD coating apparatus; wherein the purge gas feeding device is designed to expose the substrates to purge gas from below and the heating device is designed to expose the substrates to heat from below at least in a region below the injector; wherein the purge gas feeding device is designed to direct the purge gas as a temperature-control medium for heating or for cooling the substrates onto the substrates, wherein the purge gas feeding device comprises purge nozzles which are led through the heating device; wherein, in the direction of passage, a preheating device for the substrates is provided upstream of the APCVD coating apparatus, adjacent the injector to expose the substrates to heat from above in a region outside and upstream adjacent the injector, and a reheating device for the substrates is provided downstream of the APCVD coating apparatus adjacent the injector to expose the substrate to heat from above in a region outside and downstream adjacent the injector; and wherein a waste air system is provided on the respective APCVD coating apparatus, wherein the waste air system includes an inlet positioned in between the respective APCVD coating apparatus and the reheating device, or an inlet positioned in between the preheating device and the respective APCVD coating apparatus, or both.

2. The apparatus according to claim 1, wherein the conveyor rollers consist of a ceramic material or are coated therewith.

3. The apparatus according to claim 2, wherein the conveyor rollers consist of or are coated with aluminum oxide.

4. The apparatus according to claim 1, wherein the APCVD coating apparatus is arranged above the conveyor path and the heating device and the purge gas feeding device are arranged in the region of the APCVD coating apparatus underneath the conveyor path.

5. The apparatus according to claim 1, wherein at least two APCVD coating apparatuses are provided at a predefined distance apart along the conveyor path.

6. The apparatus according to claim 5, wherein a heated region of the conveyor path is provided between any two APCVD coating apparatuses and is provided with a heating device arranged above the conveyor path.

7. The apparatus according to claim 1, wherein the APCVD coating apparatus is designed for deposition temperatures of above 250 C. to about 1000 C.

8. The apparatus according to claim 1, wherein a heating system with a hot stream of gas, preferably air, N.sub.2 or a gas mixture is provided as the heating device.

9. The apparatus according to claim 8, wherein the heating system is provided outside the APCVD coating apparatus.

10. The apparatus according to claim 8, wherein the hot stream of gas comprises air, N.sub.2 or a gas mixture.

11. The apparatus according to claim 1, wherein the conveyor path can be lowered downwards relative to the rest of the apparatus.

12. The apparatus according to claim 1, wherein the reheating device is provided on the same side of the conveyor path as the APCVD coating apparatus.

Description

(1) Exemplary embodiments of the invention are shown schematically in the drawings and are explained in more detail hereinbelow. In the drawings:

(2) FIG. 1 shows a coating apparatus according to the invention comprising a single APCVD coating apparatus and a conveyor path having conveyor rollers,

(3) FIG. 2 shows a modified apparatus similar to that shown in FIG. 1 comprising two APCVD coating apparatuses,

(4) FIG. 3 shows an APCVD coating apparatus in an enlarged sectional view from the side with a gas feed and an enlarged illustration of the conveyor path, and

(5) FIG. 4 shows an illustration of the apparatus shown in FIG. 1 with the conveyor path lowered.

(6) FIG. 1 shows an apparatus 11 according to the invention, with which thin layers can be deposited on substrates. In particular, the apparatus 11 can be used for solar cell production. It has an injector 13 as the coating apparatus, as is known for example from DE 10 2011 077 833.

(7) To the left, upstream of the injector 13, provision is made of a preheating chamber 20 with a corresponding heating device 21, whereas a reheating system 23 with a heating device 24 is provided downstream of the injector 13. A conveyor path 27 runs in the bottom region of the apparatus 11 underneath the injector 13 and also the preheating chamber 20 and the reheating system 23. Said conveyor path has individual conveyor rollers 28, with which substrates 30, in particular for solar cell production, can be conveyed gently in the manner described in the introduction. In this case, the substrates 30 merely lie on the conveyor rollers 28 and are conveyed by the latter rotating. This is quite clearly an operation which is as gentle as possible, and therefore even very thin or sensitive substrates 30 can be conveyed and coated. The conveyor rollers 28 are advantageously driven, but this can easily be implemented by a person skilled in the art and is therefore not shown in more detail here. The conveyor rollers 28 rotate in this case on roller axles 29; this is likewise readily conceivable and therefore it does not have to be explained further here. The rollers 28 and the roller axles 29 consist of a ceramic material described above, to be precise of a solid material, in particular aluminium oxide. Alternatively, rollers 28 coated with a ceramic are also conceivable.

(8) Furthermore, a waste air system 15 is provided on the injector 13, and is also provided on the reheating system 23. This is explained in more detail hereinbelow.

(9) A heating device 14 is arranged underneath the injector 13. Whereas the heating devices 21 and 24 act or radiate downwards, in order to heat the substrates 30 conveyed past therebelow, the heating device 14 of the injector 13 is arranged underneath the substrates 30 or the conveyor path 27 and acts upwards. This does not interfere with the coating operation and makes it possible for the substrates to be heated from below during the coating operation which proceeds on the top side thereof.

(10) The modification of an apparatus 111 shown in FIG. 2 shows that two injectors 113a and 113b are provided, with in each case heating devices 114a and 114b thereunder and underneath a conveyor path 127. Similarly, provision is made of a preheating chamber 120 with a corresponding heating device 121 and of a reheating system 123 with a heating device 124. An intermediate heating system 125 with a corresponding heating device 126 is provided between the two injectors 113a and 113b in order to keep the substrates 130 to be coated at temperature on the conveyor path 127. The intermediate heating system 125 can in this case be formed like the preheating chamber 120 or the reheating system 123. This also applies to the heating device 126 thereof, which is in turn arranged above the conveyor path 127 and heats the substrates 130 therebelow.

(11) A waste air system 115 is provided on both injectors 113a and 113b. It also extends down to the conveyor path 127, but this is explained in more detail hereinbelow. In this apparatus 111, too, the conveyor path 127 has conveyor rollers 128. These advantageously have exactly the same design as in FIG. 1.

(12) An enlarged illustration of an injector 13 as the APCVD coating apparatus as shown in FIG. 3 firstly shows, again on an enlarged scale, the conveyor rollers 28 with the roller axles 29, which form the conveyor path 27. The substrates 30 lie on the conveyor path 27 or the conveyor rollers 28 with the substrate top sides 31 thereof facing upwards. In a manner which is not shown, the roller axles 29 can in this case be mounted in lateral roller bearings on a frame or the apparatus 11, as is known per se. Furthermore, these roller axles 29 can run through the conveyor rollers 28 and protrude at both ends. Advantageously, they can also be used in the manner of short axles or be fastened generally in the roller bearings, such that the conveyor rollers 28 are placed thereon only loosely and can rotate thereon together with a drive.

(13) The injector 13 has a gas inlet 16 into which the process gases for the APCVD coating are introduced. This is known per se to a person skilled in the art, see in particular also DE 10 2011 077 833 as mentioned above. The gas inlet 16 extends as far as a gas outlet 17 on the bottom side of the injector 13 or just above the substrate top side 31. There, the process gases then flow sideways away to different gas extractions 18a relatively close to the gas outlet 17 and to a gas extraction 18b at a somewhat greater distance to the outside. The gas extractions 18a and 18b are in this case connected to the aforementioned waste air system 15.

(14) To the left and to the right of the injector 13, the preheating chamber 20 with the heating device 21 and, respectively, the reheating system 23 with the heating device 24 are again shown. The heating devices 21 and 24 in this case heat the substrate top sides 31 just before and just after the coating operation.

(15) A purge gas feeding device 34 with individual purge nozzles 35 is provided underneath the conveyor path 27 underneath the injector 13. Purge gas is introduced into the apparatus 11 through said device, and said purge gas keeps the regions underneath the substrates 30 in the region underneath the injector 13 to some extent free of gas from the gas outlet 17 of the APCVD coating apparatus. Instances of contamination or deposits on the bottom sides of the substrates 30 can thus be avoided.

(16) The above-described heating device 14 of the injector 13 is also arranged in the region of the purge gas feed 34 or the purge nozzles 35. The purge nozzles 35 are led through the heating device 14. In this case, the purge nozzles 35 are formed either as a multiplicity of individual nozzles or as elongate nozzles, in particular slot nozzles or annular nozzles.

(17) After exiting the purge nozzles 35, the purge gas can pass through the gaps between the conveyor rollers 28 directly to the bottom side of the substrates and through gaps between successive substrates 30 into the region above the conveyor path 27. In addition to its designated purging purpose, the purge gas can, if required, perform a temperature-control function, i.e. a heating or cooling function, for the substrates 30. To this end, the purge gas is directed onto the substrates 30 at an appropriate, desired temperature. For this temperature-control application, the purge gas can, if required, be heated up by the heating device 14, in particular upon passage through the purge nozzles 35. Alternatively, the purge gas can be directed onto the substrates 30 without being preheated or after preceding active cooling, in order to cool said substrates on the bottom side, preferably during, shortly before and/or shortly after the coating process proceeding on the top side. For active purge gas cooling, it is possible to use any one of the gas cooling apparatuses known per se for this purpose, and for this reason this does not require more detailed explanations here. As an alternative or in addition to exposing the substrates to heated purge gas on the bottom side, the substrates 30 can also be heated on the bottom side directly by the heating device 14, e.g. by radiant heating through the roller gaps and/or by way of the conveyor rollers 28 themselves.

(18) The heating device 14 and the purge gas feeding device 34 are limited in terms of their extent in the conveying direction substantially to the corresponding extent of the injector 13 arranged opposite above the conveyor path 28. This proves to be sufficient for satisfactory substrate heating, with the optional addition of the heating devices 21, 24 arranged on the top side. Compared to a conventional system with a circulating conveyor belt, the advantage of a considerably higher heating efficiency is obtained in the present case by the roller path. A belt which cools down again upon circulation does not need to be heated, and the conveyor rollers 28 remain in place. In addition, those conveyor rollers 28 which are arranged in the coating region can serve as continuous heat transfer elements and/or can facilitate direct heating of the substrates from below because they are arranged at a distance apart.

(19) With respect to the manner of functioning of the coating, reference is made in turn to DE 10 2011 077 833 as mentioned above.

(20) FIG. 4, finally, once again shows the apparatus 11 shown in FIG. 1. For maintenance purposes, in particular on the conveyor path 27, the latter has been moved downwards or lowered, i.e. also the conveyor rollers 28 together with a bearing (not shown) and the heating device 14 which is fastened thereto and otherwise lies underneath the injector 13. It can readily be seen that the conveyor path 27 or the conveyor rollers 28 can now be maintained or repaired or cleaned very effectively. The conveyor path 27 can be lowered by electric motor, hydraulically or by purely mechanical means. As can be seen clearly from FIG. 4, the heating device 14 can also be lowered without any problems. It is then simply raised again together with the conveyor path 27 after the maintenance work has been carried out.