Method for controlling the surface temperature of a shield plate arranged in the process chamber of a CVD reactor

Abstract

The invention relates to a method and a device for depositing a layer on a substrate (1) in a process chamber (2) of a CVD reactor (3), wherein: a first reactive gas (19, 20) is fed, together with a first carrier gas (18), into a first gas distribution chamber (5) fluidically connected to the process chamber (2); a second reactive gas (19, 20) is fed, together with a second carrier gas (18), into a second gas distribution chamber (6) fluidically connected to the process chamber (2); a partial amount of the gas flowing out of the second gas distribution chamber (5) flows through a heat transport zone arranged between a gas exit surface of the gas inlet element and a shield plate (8) delimiting the process chamber (2) in the upward direction; the second reactive gas (19, 20) and the second carrier gas (18) have different thermal conduction properties; by varying the mass flow rate ratio between the second reactive gas (19, 20) and the second carrier gas (18), a predefined temperature of the shield plate (8) is set.

Description

Description Method for controlling the surface temperature of a screen plate arranged in the process chamber of a CVD reactor field of technology

[0001] The invention relates to a method for depositing a layer on a substrate in a process chamber of a CVD reactor, wherein a first reactive gas together with a first carrier gas is fed into a first gas distribution chamber flow-connected to the process chamber, wherein a second reactive gas together with a second carrier gas is fed into a second gas distribution chamber flow-connected to the process chamber, wherein a subset of the gas flowing from the second gas distribution chamber flows through a heat transport zone arranged between a gas outlet surface of the gas inlet device and a screen plate bounding the process chamber upwards, wherein the second reactive gas and the second carrier gas have different thermal conductivity properties. State of the art

[0002] DE 102011056589 Al and DE 102021114868 Al each disclose a process chamber of a CVD reactor, which is bounded below by a heated susceptor and above by a cooled gas inlet housing wall of a gas inlet device. A thermally decoupled shielding plate is arranged between the heated susceptor and the cooled gas inlet housing wall at a distance from the cooled gas inlet housing wall. The shielding plate is heated by conduction or radiation from the susceptor. The temperature of the shielding plate influences the layer growth on one or more substrates arranged below the shielding plate on the susceptor. 31378PCT drg / drag Ai Ltd 2024-03 To change the temperature of the shielding plate, it is necessary to move the shielding plate vertically within the process chamber. In practice, controlling the temperature by moving the shielding plate vertically proves to be too imprecise due to the inaccuracy of the motors used for this movement.

[0003] EP 2311076 Bl discloses a method for rapid thermal processing in which gases with different thermal conductivities are fed into a process chamber to change the heat conduction or convection between a heated substrate arranged in the process chamber and a cooled gas inlet housing wall.

[0004] US Patent 10,526,705 B2 discloses a process chamber of a CVD reactor, bounded at the bottom by a heated susceptor. A gap is arranged between the heating device used to heat the susceptor and the susceptor itself, into which a purge gas is introduced. The heat transfer from the heating device to the susceptor is modified by selecting a purge gas that is either conduction-dominant or radiation-dominant. This is achieved by introducing a gas with high or low thermal conductivity, respectively.

[0005] US Patent 5,270,266 A discloses a method in which a gas is introduced into a gap between a susceptor and a substrate supported on the susceptor to influence the heat transfer from the heated susceptor to the substrate. By varying the pressure at which the gas is introduced into the gap, a desired heat transfer rate is set, thus controlling the temperature of the substrate. Further prior art includes DE 19813523 A1 and DE 10007059 A1, which respectively 31378PCT drg / drag Ai Ltd 2024-03 disclose a CVD reactor with a gas inlet designed as a showerhead. Summary of the invention

[0006] The invention is based on the objective of providing a method by which the temperature of a shield plate arranged within a heat transport zone between the gas inlet element and the susceptor can be adjusted, in particular without requiring a vertical displacement of the shield plate within the heat transport zone, and a device for carrying out the method.

[0007] The problem is solved by the method or device specified in the claims. The dependent claims not only represent advantageous developments of the technical teachings specified in the dependent claims, but are also independent solutions to the problem.

[0008] The primary and fundamental proposal is to adjust one or more specific temperatures of the shielding plate, or its surface, by varying the mass flow ratio of two gases fed into a heat transfer zone between a cooled gas outlet of a gas inlet of a CVD reactor and a shielding plate that forms the upper boundary of a process chamber of the CVD reactor. Predefined surface temperature profiles of the shielding plate can also be established. The shielding plate can be located in a heat transfer zone between a heated susceptor that forms the lower boundary of the process chamber and the cooled gas outlet of the gas inlet. The shielding plate can be heated by thermal radiation or conduction through the heated susceptor. 31378PCT drg / drag Ai Ltd 2024-03

[0009] The shielding plate can be thermally decoupled from the cooled gas outlet surface. For this purpose, the shielding plate can be spaced away from the cooled gas outlet surface by a gap, as described in DE 102011056589. This gap preferably extends over the entire gas outlet surface of the gas inlet element. A subset of gas flowing from one of at least two gas distribution chambers of the gas inlet element can flow through this gap before the gases enter the process chamber through gas passage channels arranged in the shielding plate. The invention is based on the understanding that the heat transfer properties of the gap, and thus the temperature of the shielding plate, can be primarily influenced by the composition of the gas flowing through the gap. By varying the mass flow ratio of the gases flowing through the gap, the heat transfer properties of the gap can be controlled.

[0010] In one embodiment of the invention, the gas inlet element can be designed like a shower head and have at least two vertically arranged gas distribution chambers. A first reactive gas, together with a first carrier gas, can be fed into the process chamber via gas lines extending across the gas outlet surface into a first gas distribution chamber located at the top. The gas lines can be tubes connecting the first gas distribution chamber to the gas outlet surface. These gas lines can be extended or have projections that reach into the recesses of the gas passage channels in the shielding plate. This reduces the amount of gas flowing from the first gas distribution chamber into the gap. The first reactive gas can, in particular, contain a metal-organic compound of an element from group III, for example, TMGa. Hydrogen (H₂) can preferably be used as the first carrier gas. 31378PCT drg / drag Ai Ltd 2024-03

[0011] In a second gas distribution chamber located at the bottom, adjacent to the first gas distribution chamber, a second reactive gas can be introduced along with a second carrier gas. The second reactive gas can be, in particular, a hydride of group V, for example, ammonia (NH3), which is introduced into the process chamber together with H2. The second reactive gas and the second carrier gas can preferably have different thermal conductivities. The gas mixture of the second reactive gas and the second carrier gas can flow through the gap between the gas outlet surface and the shielding plate. If the ratio of the second carrier gas to the second reactive gas is changed by altering the respective mass flows, the thermal conductivity of the gas mixture also changes, and thus so do the heat transfer properties of the gas flowing through it.According to the invention, the temperature of the shielding plate is primarily controlled by varying the mass flow ratio, without affecting a coating process carried out in the process chamber. Therefore, the mass flow of the reactive gases and also the total mass flow of the carrier gases are kept constant. Thus, if the mass flow of the second carrier gas is varied, the mass flow of the first carrier gas is also changed accordingly.

[0012] Preferably, the first and second carrier gases can contain the same starting material, for example, H2. If NH3 is used as the second reactive gas, this means that, due to the higher thermal conductivity of H2 compared to NH3, increasing the mass flow rate of the second carrier gas increases the thermal conductivity of the gas mixture consisting of the second carrier gas H2 and the second reactive gas NH3, thus altering the heat transfer properties of the crack. Since the total mass flow rate of the carrier gas fed into the process chamber is the sum of the mass flows of the first carrier gas... 31378PCT drg / drag Ai Ltd 2024-03 and second carrier gas, preferably kept constant, if the mass flow of the second carrier gas is increased, the mass flow of the first carrier gas fed into the first gas distribution chamber is reduced accordingly. The mass flow ratio between the second reactive gas and the second carrier gas can preferably be changed by varying the mass flow of the second carrier gas. The control of the absolute surface temperature of the shielding plate can thus preferably be achieved by varying the second carrier gas. The mass flow of the first carrier gas can be adjusted according to the change in the mass flow of the second carrier gas. The magnitude of the absolute change in the mass flow of the second carrier gas can correspond to the magnitude of the absolute change in the mass flow of the first carrier gas.

[0013] Furthermore, the first carrier gas and / or the second carrier gas can be a gas mixture consisting of two or more different gases. For example, the first and / or the second carrier gas can be a gas mixture of H₂ and N₂.

[0014] The shielding plate can also be arranged in a height-adjustable manner within the process chamber. Its temperature can also be influenced by vertically shifting the shielding plate.

[0015] The invention relates in particular to a method for controlling a process chamber ceiling temperature in a process chamber of a CVD reactor, wherein different gas mixtures are fed into two separate gas distribution chambers of a gas inlet device, wherein each gas mixture consists of a carrier gas and a reactive gas, wherein at least one of the two gas mixtures is located in a heat- 31378PCT drg / drag Ai Ltd 2024-03metransportzone between a cooled gas outlet surface and a ceiling plate, which is in particular a shielding plate, wherein the temperature of the ceiling plate is controlled by changing the mass flows of the carrier gases fed into the gas distribution chambers, wherein it is particularly provided that for this purpose the first carrier gas flow fed into a first of the gas distribution chambers is reduced by a first partial flow and the second carrier flow fed into a second of the gas distribution chambers is increased by a second partial flow, wherein it is particularly provided that the two partial flows are essentially equal. Brief description of the drawings

[0016] An embodiment of the invention is explained below with reference to the accompanying drawing. It shows: Fig. 1 schematically shows a CVD reactor 3 with a gas inlet device 4, wherein a gap 12 is present between a gas outlet surface 7 of the gas inlet device 4 and a shielding plate 8. Description of the embodiments

[0017] Figure 1 schematically shows a CVD reactor 3 for depositing layers, for example III-V layers, onto substrates 1. A susceptor 14 is arranged in a reactor housing of the CVD reactor 3 and can be heated to a process temperature by a heating device 13. The heating device 13 can be, for example, an infrared heater, an RF heater, or a resistance heater. The broad side of the susceptor 14 facing away from the heating device 13 serves as a support for the substrates 1. The substrates 1 are coated in a process chamber 2 of the CVD reactor 3. The process chamber 2 is bounded below by the susceptor 14 and above by the gas inlet 4. 31378PCT drg / drag Ai Ltd 2024-03

[0018] The gas inlet assembly 4 comprises two vertically arranged gas distribution chambers 5, 6, each connected to a gas mixing system via supply lines 28, 29. A first gas distribution volume 5, into which a first reactive gas supplied by a gas source 20 can be fed together with a first carrier gas supplied by a carrier gas source 18, is connected to the process chamber 2 via first gas inlet channels 10. A second gas distribution volume 6 is also connected to the process chamber 2 via second gas inlet channels 11. Both gas inlet channels 10, 11 extend through a coolant chamber 9, through which a coolant can flow. The cooling device thus configured cools a gas outlet plate 30 of the gas inlet assembly 4, which forms a gas outlet surface 7 on its side facing the process chamber 2.The gas inlet channels 10, 11 are evenly distributed over the entire cross-sectional area of ​​the gas inlet device 4.

[0019] A shielding plate 8 extends across the entire gas outlet area 7 between the susceptor 14 and the gas outlet area 7. The shielding plate 8 is spaced apart from the cooled gas outlet area 7, creating a gap 12 between the shielding plate 8 and the cooled gas outlet area 7. The shielding plate 8 has first and second passage channels 15, 16, which are evenly distributed across the entire surface of the shielding plate 8. Extensions 10' of the first gas inlet channels 10 project beyond the gas outlet area 7, so that, in the position of the shielding plate 8 shown in Figure 1, the extensions 10' of the first gas inlet channels 10 project into a recess 32 of the first passage channels 15. This results in gases flowing through the first gas inlet channels 10 being introduced directly into the process chamber 2. A front face 10" of the extensions 10' is arranged spaced apart from the bottom 33 of the depression 32.The front face 10" of the extensions 10' can. 31378PCT drg / drag Ai Ltd 2024-03 but also rest on the bottom 33 of the recess 32. Preferably, the distance between the end face 10" of the extensions 10' is greater than the gap 12 arranged between the shielding plate 8 and the cooled gas outlet surface 7.

[0020] The second gas inlet channels 11, on the other hand, open into the gas outlet surface 7, so that the gases are not fed directly into the second passage channels 16, but at least a subset of these gases first flows through the gap 12 and only then is fed into the process chamber 2 via the second passage channels 16.

[0021] The gas mixing system 29 connected to the gas inlet device 4 comprises several different gas sources, 19, 20, 21. A first reactive gas supplied by a first precursor gas source 20, together with a first carrier gas supplied by a carrier gas source 18, shown here by way of example as H₂, can be fed into the first gas distribution chamber 5 via the supply line 28. The first reactive gas is preferably a gas containing a metal-organic compound of an element of group III. The mass flows of the first reactive gas and the first carrier gas are each controlled by means of mass flow controllers 26, 25.

[0022] A second precursor gas, here for example NH3, supplied by a second precursor gas source 19, is fed into the second gas distribution chamber 6 together with a second carrier gas supplied by the carrier gas source 18. In the embodiment shown in Figure 1, the first and second carrier gases are both H2 and are supplied by the same carrier gas source 18. The mass flows of the carrier gases into the respective gas distribution chambers 5, 6 are regulated by a mass flow controller 25, 24, respectively. 31378PCT drg / drag Ai Ltd 2024-03gelt. However, the first and second carrier gases can also be different carrier gases or carrier gas mixtures supplied from different carrier gas sources.

[0023] The gases fed into process chamber 2, as well as decomposition products and reaction products of the gases, are directed from process chamber 2 via a gas outlet 17 into a gas disposal system not shown.

[0024] Additionally, a further optional gas source 21 connected to the second gas distribution chamber 6 is shown. This can, for example, provide another carrier gas or another reactive gas. Further gas sources can also be connected to the first gas distribution chamber 6.

[0025] The gas mixtures consisting of the first reactive gas and first carrier gas or second reactive gas and second carrier gas are each fed into the respective gas distribution chamber 5, 6 via the supply lines 27, 28 in a mass flow controlled manner.

[0026] Furthermore, a control device 31 is provided which, using measured values ​​supplied by a temperature measuring device not shown, controls the mass flow controllers 22, 23, 24, 25, 26 in such a way that predetermined absolute temperatures of the screen plate are set.

[0027] The foregoing statements serve to explain the inventions covered by the application as a whole, which each independently further develop the prior art at least through the following combinations of features, whereby two, several or all of these combinations of features may also be combined, namely: 31378PCT drg / drag Ai Ltd 2024-03

[0028] A method characterized in that a predetermined temperature of the shielding plate 8 is set by varying the mass flow ratio between the second reactive gas and the second carrier gas.

[0029] A method characterized in that the mass flow of the first and the second reactive gas is kept constant, wherein if the mass flow of the second carrier gas changes, the mass flow of the first carrier gas is also changed.

[0030] A method characterized in that the total mass flow of the first and second carrier gas fed into the two gas distribution chambers 5, 6 is kept constant.

[0031] A process characterized in that the first and second carrier gas 18 contain the same starting material, in particular hydrogen.

[0032] A process characterized in that the first precursor gas contains a metal-organic compound of the III main group and the second precursor gas contains a hydride of the V main group.

[0033] A device characterized in that the mass flow ratio between the first carrier gas and the second carrier gas is varied from 1:2 to 3:0.

[0034] A device characterized in that the control unit 31 is programmed to carry out the method according to one of the preceding claims. 31378PCT drg / drag Ai Ltd 2024-03

[0035] A device characterized in that extensions 10' of the gas inlet channels 10, which are flow-connected to one of the gas distribution chambers 5, project into recesses 32 of the passage channels 15 at a distance from a bottom 33 of the recess 32.

[0036] All disclosed features are essential to the invention (individually, but also in combination with one another). The disclosure of this application hereby incorporates in full the disclosure content of the associated / attached priority documents (copy of the earlier application), also for the purpose of including features of these documents in the claims of the present application. The dependent claims, even without the features of a referenced claim, characterize independent inventive developments of the prior art, in particular for the purpose of filing divisional applications based on these claims. The invention specified in each claim may additionally include one or more of the features described above, in particular those identified by reference numerals and / or listed in the reference numeral list.The invention also relates to design forms in which individual features mentioned in the preceding description are not realized, in particular insofar as they are recognizably unnecessary for the respective purpose or can be replaced by other technically equivalent means. 31378PCT drg / drag Ai Ltd 2024-03 List of reference marks 1 Substrate 25 Mass flow controller 2 Process chamber 26 Mass flow controller 3 CVD reactor 27 Supply line 4 Gas inlet device 28 Supply line 5 first gas distribution chamber 29 supply line 6 Second gas distribution chamber 30 Gas outlet plate 7 Gas outlet surface 31 Control device 8 Shielding plate 32 Recess 9 Coolant chamber 33 Base 10 Gas intake channel 10' extension 10" front 11 Gas intake channel 12 columns 13 Heating system 14 Susceptor 15 Passage channel 16 Passage channel 17 Gas outlet 18 Carrier gas source 19 Gas source, reactive gas 20 Gas source, reactive gas 21 Gas source 22 Mass flow controllers 23 Mass flow controllers 24 Mass flow controllers 31378PCT drg / drag Ai Ltd 2024-03

Claims

Claims 1. Method for depositing a layer on a substrate (1) in a process chamber (2) of a CVD reactor (3), wherein a first reactive gas is fed into a first gas distribution chamber (5) which is connected to the process chamber (2) in a flow direction, wherein a second reactive gas is fed into a second gas distribution chamber (6) which is connected to the process chamber (2) in a flow direction, together with a second carrier gas, wherein a subset of the gas flowing from the second gas distribution chamber (6) flows through a heat transport zone arranged between a gas outlet surface (7) of the gas inlet device (4) and a screen plate (8) that bounds the process chamber (2) upwards, where the second reactive gas and the second carrier gas have different thermal conductivity properties, characterized in that a predetermined temperature of the screen plate (8) is set by varying the mass flow ratio between the second reactive gas and the second carrier gas.

2. Method according to claim 1, characterized in that the mass flow of the first and the second reactive gas is kept constant, wherein if the mass flow of the second carrier gas changes, the mass flow of the first carrier gas is also changed.

3. Method according to one of the preceding claims, characterized in that the total mass flow of the first and second carrier gas fed into the two gas distribution chambers (5, 6) is kept constant. 31378PCT drg / drag Ai Ltd 2024-034. Method according to claim 2, characterized in that the first and second carrier gas contain the same starting material, in particular hydrogen.

5. Method according to one of the preceding claims, characterized in that the first precursor gas contains a metal-organic compound of the III main group and the second precursor gas contains a hydride of the V main group.

6. Method according to one of the preceding claims, characterized in that the mass flow ratio between the first carrier gas and the second carrier gas is varied from 1:2 to 3:

0.

7. Device for depositing a layer on a substrate (1), comprising a process chamber (2) of a CVD reactor (3), which is bounded downwards by a susceptor (14) and upwards by a screen plate (8) with passage channels (15, 16), in particular height-adjustable. with a heating device (13) for heating the susceptor (14), with a gas inlet device (4) comprising at least two gas distribution chambers (5, 6) into which gases provided by a gas mixing system (29) can be fed, wherein the gas distribution chambers (5, 6) are each connected to the process chamber (2) via gas inlet channels (10, 11), with a cooling element (9) for cooling the gas inlet device (4), and with a control device (31) for controlling the heating device (13), the cooling element (9), mass flow controllers (22, 23, 24, 25, 26) and valves for feeding the gases into the process chamber (2) and for 31378PCT drg / drag Ai Ltd 2024-03Relocation of the screen plate (8), characterized in that the control device (31) is programmed to carry out the method according to one of the preceding claims.

8. Device according to claim 7, characterized in that extensions (10') of the gas inlet channels (10) flow-connected to one of the gas distribution chambers (5) project into recesses (32) of the passage channels (15) at a distance from a bottom (33) of the recess (32).

9. Method or device characterized by one or more of the characterizing features of one of the preceding claims. 31378PCT drg / drag Ai Ltd 2024-03

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