Method and apparatus for continuous vapor deposition of silicon on a substrate

Abstract

A method for continuously vapor-depositing silicon on a substrate, comprising the following steps: a) introducing at least one substrate into a reaction chamber (2); b) introducing a process gas and at least one gaseous silicon precursor compound into the reaction chamber (2); c) forming a gaseous mixture of at least one silicon-based intermediate product coexisting with the gaseous silicon precursor compound and the process gas in the reaction chamber (2); d) forming a silicon layer by vapor-depositing silicon on the substrate using the silicon precursor compound and / or the silicon-based intermediate product; e) removing excess of the gaseous mixture from the reaction chamber (2); and The method further comprises step (f), in which at least one component of the excess gaseous mixture is returned to the reaction chamber (2), the component being selected from the silicon precursor compound, the silicon-based intermediate product and / or the process gas, wherein the silicon precursor compound is introduced into the reaction chamber (2) in such a manner that the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the process gas is 0.2:0.8 to 0.5:0.5, preferably 0.3:0.7 to 0.5:0.5, and particularly preferably 0.5:0.5.

Description

Technical Field

[0001] By chemically vapor-depositing silicon on a substrate, silicon layers with a layer thickness of 1 to 200 μm can be produced, which are used in solar cells and microelectronics. Unlike conventional production methods, which involve sawing of silicon blocks produced by the Czochralski method or zone melting, sawing losses are avoided in chemical vapor deposition. In addition, compared to conventionally produced silicon wafers with a layer thickness in the range of 200 to 300 μm, a large amount of silicon and thus a considerable cost saving can be achieved due to the smaller layer thickness. Background Art

[0002] In chemical vapor deposition, a substrate is introduced into a reaction chamber and heated to 700° C. to 1400° C. Thereafter, a silicon precursor compound is introduced into the reaction chamber, which thermally decomposes in the reaction chamber, thereby causing solid silicon to be deposited on the substrate. Possible byproducts of this chemical reaction as well as excess silicon precursor compound are drawn out of the reaction chamber. By means of this chemical vapor deposition, in addition to polycrystalline silicon layers, monocrystalline silicon layers are also produced by vapor epitaxy on crystalline substrates.

[0003] The silicon precursor compounds are mainly silane and chlorosilane. The use of silane is disadvantageous due to its spontaneous combustion when in contact with oxygen in the air and its tendency to undergo gas phase nucleation. In the case of chlorosilane, the silicon deposition reaction on the substrate is carried out in the presence of hydrogen as a process gas and is carried out according to a simplified reaction formula:

[0004] S H (4-n) Cl n +(n-2)H 2 →Si+nHCl

[0005] It has been shown here that silicon tetrachloride (n=4) is thermally stable up to 1600° C. The deposition of silicon on the substrate occurs only by adding hydrogen. However, in addition, in the reaction chamber or after passing through the reaction chamber, according to the following reaction formula, 2 Concentration, temperature and pressure, during cooling, other low-chlorosilanes are formed, for example trichlorosilane (n=3) and dichlorosilane (n=2):

[0006]

[0007] These intermediate products also decompose thermally and lead to silicon deposition at temperatures significantly lower than 700° C. Silicon deposits thus occur not only on the substrate surface but also in the gas supply and gas removal lines of the reaction chamber. This so-called parasitic deposition leads to a reduction in the cross section of these fluid lines and therefore has to be removed regularly in order to obtain a full cross section.

[0008] DE 10 2005 045 582 describes, for example, a method for continuously vapour-depositing silicon on a substrate, in which, while silicon is being deposited on the substrate, parasitic deposits in the device are removed and / or their formation is prevented by periodically changing the composition of the supplied gas. For this purpose, an etching gas, hydrogen chloride, is supplied to the reaction chamber at periodic intervals in order to remove the parasitic deposits. A disadvantage of this method is that the productivity of the silicon-coated substrate is significantly reduced in the presence of an etching gas, since in the presence of hydrogen chloride all solid silicon, that is to say not only the parasitic deposits, is converted into gaseous trichlorosilane. This leads on the one hand to a reduction in the thickness of the silicon layer and on the other hand to an increase in production costs by using a different gas. Summary of the invention

[0009] It is therefore an object of the present invention to provide a method and a device for vapor deposition of silicon on a substrate, by which the formation of parasitic deposits is prevented or at least reduced and the productivity can be increased compared to the methods known from the prior art.

[0010] This object is achieved according to the invention by a method having the features of claim 1 and a device having the features of claim 12 .

[0011] Advantageous developments of the concept according to the invention are the subject matter of the dependent claims.

[0012] The invention relates to a method for the continuous vapor deposition of silicon on a substrate according to the preamble of claim 1. The invention further relates to an apparatus for the continuous vapor deposition of silicon on a substrate according to the preamble of claim 12.

[0013] The method for continuously vapor-depositing silicon on a substrate according to the present invention comprises the following steps:

[0014] In method step (a), at least one substrate is introduced into a reaction chamber. In method step (b), a process gas and at least one gaseous silicon precursor compound are introduced into the reaction chamber. Then, in method step (c), a gaseous mixture of at least one silicon-based intermediate product and the process gas coexisting with the gaseous silicon precursor compound is formed in the reaction chamber. In the subsequent method step (d), a silicon layer is formed by vapor deposition of silicon on the substrate from the gaseous silicon precursor compound and / or the silicon-based intermediate product. In method step (e), excess gaseous mixture is removed from the reaction chamber.

[0015] It is important in the method according to the invention that in method step (f) at least one component of the gaseous mixture in excess is returned to the reaction chamber, said component being selected from the group consisting of silicon precursor compound, silicon-based intermediate product and / or process gas, wherein the gaseous silicon precursor compound is fed into the reaction chamber in such a way that the molar ratio of silicon-based intermediate product to silicon precursor compound in the process gas is from 0.2:0.8 to 0.5:0.5, preferably from 0.3:0.7 to 0.5:0.5, particularly preferably 0.5:0.5. Thus, the silicon precursor compound is present in the gas supply stream in excess or in the same amount as the silicon-based intermediate product.

[0016] It is within the scope of the invention that the substrate consists of polycrystalline silicon or monocrystalline silicon, ceramic, glass and / or other composites or layer systems. However, the invention is not limited thereto, since, for example, it is also conceivable to use a polymer-containing substrate or other semiconductor materials, such as silicon carbide or other composite semiconductors.

[0017] Since, when producing silicon layers on a substrate by chemical vapor deposition of chlorosilanes, less than 100%, typically between 15% and 30%, of the silicon precursor compounds used are always converted into solid silicon, the return of at least one component of the excess gaseous mixture can not only significantly reduce environmentally polluting waste but also reduce process costs due to the lower consumption of silicon precursor compounds.

[0018] Furthermore, the present invention is also based on the recognition that the deposition of silicon is not only temperature-dependent, but also on the molar composition of the gaseous mixture, which consists of at least one silicon-based intermediate product, a silicon precursor compound and a process gas. Studies by the applicant have shown that the deposition of silicon can be suppressed or completely prevented by appropriately selecting the molar ratio of the silicon-based intermediate product to the silicon precursor compound. This finding is based on the fact that the chemical vapor deposition of silicon from the silicon precursor compound and / or from the silicon-based intermediate product tends to proceed as an equilibrium reaction, which proceeds temperature-dependently and concentration-dependently. In particular, when the molar ratio of the silicon-based intermediate product to the silicon precursor compound is from 0.2:0.8 to 0.5:0.5, most of the parasitic deposition can be prevented. When the molar ratio of the silicon-based intermediate product to the silicon precursor compound is from 0.3:0.7 to 0.5:0.5, the parasitic deposition can even be completely prevented. This molar ratio can be controlled by controlled feeding of silicon precursor compounds and by returning excess at least one component of the gaseous mixture selected from silicon precursor compounds, silicon-based intermediate products and / or process gases to the gas supply to the reaction chamber.

[0019] As is well known, during chemical vapor deposition, the deposition rate of solid silicon on a substrate also depends on the composition of the gas flow introduced into the reaction chamber. Therefore, in order to optimize the deposition rate of silicon, in method step (b), preferably not only one silicon precursor compound but a plurality of silicon precursor compounds can be introduced into the deposition chamber. If a plurality of silicon precursor compounds are introduced into the gas supply of the reaction chamber, the molar ratios given relate to one of the silicon precursor compounds. It is within the scope of the present invention that a plurality of chlorosilanes, in particular silicon tetrachloride and trichlorosilane, are introduced into method step (b) as silicon precursor compounds. In this case, the molar ratios preferably relate to the ratio of high chlorosilanes to silicon-based intermediates.

[0020] Due to the formation of a gaseous mixture in the reaction chamber from at least one silicon-based intermediate product, a silicon precursor compound and a process gas in method step (c) and due to the subsequent silicon deposition in method step (d), the composition of the excess gaseous mixture drawn off can only be estimated imprecisely. Therefore, in a first advantageous embodiment of the method, in method step (f), the molar ratio of silicon-based intermediate product to silicon precursor compound in the excess gaseous mixture is determined by a measuring unit.

[0021] Here, it is within the scope of the present invention that the measuring unit is configured to be used directly for determining the molar ratio or to be configured to determine an equivalent value, in particular to determine the concentration and / or amount and / or volume or mass flow of one and / or more silicon-based intermediate products, from which the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous mixture can be derived. However, optionally, the measuring unit is also used to directly determine the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous mixture. In addition, the measuring unit can be used to determine the relevant molar ratio online or to determine the concentration of one and / or more silicon-based intermediate products. Optionally, the measuring unit can also be used only temporarily, for example at the beginning of chemical vapor deposition and / or after a determined time interval, to determine the relative molar ratio or to determine the concentration of one and / or more silicon-based intermediate products. However, the present invention is not limited to this.

[0022] In another advantageous embodiment of the method, the molar ratio of the silicon-based intermediate product to the silicon precursor compound determined by the measuring unit is sent to a control unit, and the control unit controls the introduction of the silicon precursor compound so that the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the process gas is 0.2:0.8 to 0.5:0.5, preferably 0.3:0.7 to 0.5:0.5, and particularly preferably 0.5:0.5.

[0023] The molar ratio determined by the measuring unit can be transmitted automatically, in particular via a data line or wirelessly, or manually by a user who reads the result of the measuring unit and transmits this information to the control unit. The subsequent control of the introduction of the silicon precursor compound by the control unit can also be carried out automatically or manually by the user. It is within the scope of the invention that the control unit is configured as a flow regulator. However, the invention is not limited to this. However, automatic regulation has significant advantages in terms of process reliability and reduced workload.

[0024] In order to be able to perform chemical vapor deposition of solid silicon on a substrate as a continuous process, not only the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the supply gas flow of the reaction chamber plays an important role, but also the total amount of the silicon precursor compound and the silicon-based intermediate product is important. The reduction of the total amount below a certain value will lead to a reduction in the deposition rate of solid silicon. The reason is that silicon deposition is carried out as an equilibrium reaction. It is therefore advantageous to keep the total amount constant when passing into the reaction chamber in order to provide optimal conditions for the deposition of solid silicon. This is advantageously achieved in that the input flow of the process gas is preferably kept constant, and the silicon-based intermediate product and the silicon precursor compound are metered in such a way that on the one hand the required molar ratio of the two compounds relative to each other is set, and on the other hand the required total amount of the two compounds is achieved. If, for example, the amount of the silicon-based intermediate product is detected to be too high by a measuring unit, the intermediate product can also be drawn out of the device so as not to exceed the maximum total amount in the reaction chamber.

[0025] Furthermore, an advantageous embodiment of the method according to the invention provides that in step (f), impurities are removed from the excess gaseous compound. In order to enable the return of one or more components of the excess gaseous mixture in step (f) of the method, in a preferred embodiment, the method can be provided with a recovery unit in step (f), which at least partially separates the excess gaseous mixture. Such a recovery unit thus makes it possible not only to return the desired components of the excess gaseous mixture, but also to separate undesired by-products of silicon deposition.

[0026] In a further advantageous embodiment of the method, in step (f), the silicon-based intermediate product and / or the silicon precursor compound and / or the process gas are returned to the reaction chamber.

[0027] In a further advantageous embodiment of the method, the silicon precursor compound is a chlorosilane, preferably silicon tetrachloride and / or trichlorosilane.

[0028] As already explained above, the deposition rate of silicon is preferably optimized in that, in method step (b), not only one silicon precursor compound but a plurality of silicon precursor compounds are introduced into the deposition chamber. If a plurality of silicon precursor compounds are introduced into the reaction chamber, the silicon precursor compounds are preferably silicon tetrachloride and trichlorosilane.

[0029] Compared to other commercially available silanes (e.g. disilane or trisilane), chlorosilanes are significantly more economical and less hazardous to handle, since, in contrast to other substances, they are not pyrophoric in the presence of atmospheric oxygen. Furthermore, the use of chlorosilanes also makes it possible to achieve significantly higher deposition rates than the silanes in order to achieve high layer qualities, thereby significantly increasing the productivity of substrates coated with silicon.

[0030] It is generally known that when using trichlorosilane as a precursor compound, high deposition rates of silicon on substrates in the range of 1 μm / min to 15 μm / min can be achieved, with silicon deposition already occurring at temperatures starting at 700° C. However, a disadvantage here is that at this temperature or above, a significant increase in parasitic deposition occurs in the gas lines of the reaction chamber. In contrast, pure silicon tetrachloride is stable up to about 1600° C. However, due to the lower silicon-chlorine ratio, the deposition rate is significantly lower.

[0031] Studies by the applicant have shown that the use of silicon tetrachloride in the presence of trichlorosilane leads to optimized deposition rates while simultaneously avoiding parasitic deposition.

[0032] Since silicon tetrachloride is thermally stable up to temperatures of 1600° C. and silicon deposition only takes place at lower temperatures in the presence of hydrogen, a further advantageous embodiment provides that the process gas is hydrogen.

[0033] According to another advantageous variant of the process according to the invention, the silicon-based intermediate product is a chlorosilane, preferably trichlorosilane.

[0034] As already explained above, in method step (b), a plurality of silicon precursor compounds are advantageously introduced, wherein the silicon precursor compound is preferably silicon tetrachloride or trichlorosilane. It should be noted that in this case, trichlorosilane is introduced into the reaction chamber as a silicon precursor compound on the one hand, and can also be returned to the reaction chamber as an intermediate product in method step (f) on the other hand.

[0035] In order to achieve optimal deposition of silicon on the substrate and at the same time minimize the process costs, an advantageous embodiment of the method provides that in step (c), the total amount of the silicon precursor compound and the silicon-based intermediate product is present in the process gas in a molar ratio of 1 to 10 mol%, preferably 2 to 7 mol%, particularly preferably 3 to 6 mol%.

[0036] A further advantageous embodiment of the method provides that the formation of the silicon layer is carried out by chemical vapor deposition of silicon from silicon precursor compounds and / or silicon-based intermediate products on the substrate at a pressure of 0.8 bar to 1.2 bar prevailing in the reaction chamber.

[0037] It is therefore within the scope of the invention to carry out the method according to the invention at approximately atmospheric pressure. This avoids the time-consuming conversion of the reaction chamber to a vacuum state, thereby significantly increasing the productivity of the substrate coating with silicon.

[0038] Since the deposition rate of silicon on the substrate is strongly dependent on the temperature, in another advantageous embodiment of the method according to the invention, the substrate is heated in the reaction chamber at least to a temperature of 700° C. to 1400° C., preferably 1000° C. to 1300° C., particularly preferably 1100° C. to 1200° C. Heating the substrate to a certain temperature thus makes it possible to adjust the deposition rate of silicon on the substrate.

[0039] It is within the scope of the invention to heat not only the substrate but also the reaction chamber and / or the gas line arranged on the reaction chamber. Here, the substrate and / or the reaction chamber and / or the gas line can be heated to different temperatures respectively. This makes it possible to achieve an optimal gas supply to the reaction chamber and gas return.

[0040] Another aspect of the present invention relates to an apparatus for continuously vapor depositing silicon on a substrate, in particular an apparatus for performing a method according to any one of claims 1 to 11, the apparatus comprising: a reaction chamber, the reaction chamber comprising at least one inlet for the substrate and at least one outlet for the substrate; a conveying device for conveying the substrate from the inlet to the outlet through the reaction chamber; at least two gas inlets, the at least two gas inlets being used to supply gas into the reaction chamber; at least one gas outlet, the gas outlet being used to lead the gas out of the reaction chamber; at least two fluid supply pipes, preferably gas supply pipes, the fluid supply pipes being connected to the two gas inlets of the reaction chamber.

[0041] The gas inlet is used to supply process gases, silicon-based intermediate products and / or silicon precursor compounds to the reaction chamber.

[0042] What is important here is that the device according to the present invention has at least one control unit, and a circulation pipe is arranged between the gas outlet and the gas inlet of the reaction chamber, the circulation pipe is connected to the fluid supply pipe and to the gas outlet of the reaction chamber, the device has at least one measuring unit, the measuring unit is used to determine the molar ratio of the silicon-based intermediate product to the silicon precursor compound and / or a value equivalent to the molar ratio, and the control unit and the measuring unit are configured to operate in coordination so that the flow rate of the supply pipe can be controlled or adjusted based on a signal sent by the measuring unit to the control unit.

[0043] As already mentioned above, it is within the scope of the present invention that the measuring unit is configured to determine the concentration and / or amount and / or volume flow or mass flow of one or more silicon-based intermediate products, from which the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous compound can be derived. However, the measuring unit can also be used to directly determine the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous compound. In addition, the measuring unit is configured to determine the relevant molar ratio or the concentration of one and / or more silicon-based intermediate products online. Optionally, the measuring unit can also determine the relevant molar ratio or the concentration of one and / or more silicon-based intermediate products only temporarily, for example at the beginning of chemical vapor deposition and / or after a certain time interval. However, the present invention is not limited to this. However, this automatic regulation has obvious advantages in terms of process reliability and reduced workload.

[0044] This device allows the substrate to be continuously conveyed into the reaction chamber, in which case the substrate is conveyed by the conveying device from the inlet to the outlet of the reaction chamber. The gas inlet of the device according to the invention is used for the introduction of process gases, silicon precursor compounds, and for the return of components in the excess gaseous precursor compound after the gaseous precursor compound is discharged from the reaction chamber.

[0045] According to a preferred embodiment of the present invention, the measuring unit is arranged on the circulation pipe.

[0046] It is within the scope of the invention that the measuring unit is integrated in the circulation line or arranged on the circulation line. If the measuring unit is integrated in the circulation line, the determination of the molar ratio of the silicon-based intermediate product to the silicon precursor compound is carried out online. This measurement can be carried out continuously or at time intervals predefined by the user. If the measuring unit is arranged on the circulation line, the measurement of the molar ratio of the silicon-based intermediate product to the silicon precursor compound is carried out by automatically supplying the sample or after extracting the sample by the user, who manually supplies the excess gaseous mixture sample to the measuring unit. However, the invention is not limited to this.

[0047] Another preferred embodiment of the device according to the invention provides that the measuring unit is configured as a spectrometer or as a mass flow meter, for example as a Coriolis mass flow meter, or as a volume flow meter.

[0048] If a silicon precursor compound which is liquid at room temperature and / or a silicon-based intermediate product which is liquid at room temperature is used, in an advantageous embodiment of the device at least one of the fluid supply lines has an evaporator which converts the silicon precursor compound and / or the silicon-based intermediate product into a gaseous state.

[0049] Another preferred embodiment of the device according to the invention provides that the circulation line has a recovery unit for separating the excess gaseous mixture discharged from the reaction chamber and recovering silicon precursor compounds and / or silicon-based intermediate products and / or process gases.

[0050] In another advantageous embodiment of the device according to the invention, the recovery unit is configured as a distillative separation device and / or a dry absorber or dry adsorber, by means of which the hydrogen chloride and / or silicon precursor compounds formed during the chemical vapor deposition of solid silicon can be separated when returning the excess gaseous mixture.

[0051] It is advantageous to return the excess gaseous components separately, since this allows for separate regulation and / or utilization. In order to return the silicon precursor compound and / or the silicon-based intermediate product and / or the process gas separately after separation by, for example, a distillation-type separation device, the circulation line preferably has a plurality of branch lines between the recovery unit and the fluid supply line, the branch lines being used to return the process gas, the silicon-based intermediate product and / or the silicon precursor compound separately, each branch line having a separate measuring unit for determining the mass flow and / or volume flow of the process gas, the silicon-based intermediate product and / or the silicon precursor compound.

[0052] It is within the scope of the invention to discharge the process gas and / or silicon-based intermediate product and / or silicon precursor compound from the device after separation. For this purpose, for example, the gas scrubber and / or the distillative separation device can have a gas outlet, which is connected to a gas discharge line. However, the invention is not limited to this, since such a gas outlet with a gas discharge line can also be arranged on the circulation line in the area of ​​the measuring cell. However, it is advantageous to return at least components of the silicon-based intermediate product in order to reduce process costs. For this reason, it is also advantageous to return the process gas, in particular the hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Other characteristics of the present invention are apparent from the following description of embodiments with reference to the accompanying drawings, in which:

[0054] Figure 1 A schematic diagram showing a first embodiment of an apparatus for continuously vapor-depositing silicon on a substrate according to the present invention;

[0055] Figure 2 A schematic diagram showing a second embodiment of an apparatus for continuously vapor-depositing silicon on a substrate according to the present invention; and

[0056] Figure 3 A schematic diagram showing a third embodiment of the apparatus for continuously vapor-depositing silicon on a substrate according to the present invention is shown. DETAILED DESCRIPTION

[0057] Figure 1 A first embodiment of a device 1 for continuously vapour-depositing silicon on a substrate according to the invention is shown. The device 1 comprises a reaction chamber 2, a measuring unit 3, a control unit 4, a circulation pipe 5, a gas scrubber 6 and a recovery unit 7.

[0058] The reaction chamber 2 comprises an inlet 8, through which the substrate to be coated can be introduced into the reaction chamber 2. In addition, an outlet 9 is provided on the side of the reaction chamber 2 opposite to the inlet 8, through which the substrate coated with silicon can be introduced out of the reaction chamber 2. The substrate is introduced into the reaction chamber 2 and introduced out of the reaction chamber 2 again by a conveying device 10. Figure 1 As shown by the arrow in the figure, the conveying device 10 has a direction of conveying the substrate from the inlet 8 to the outlet 9. The conveying device 10 can be configured as a conveyor belt. Optionally, the conveying device 10 can also have a plurality of conveying rollers, or can also be configured as a slide rail conveying device.

[0059] like Figure 1 As shown, two substrates can be placed vertically and fed into the reaction chamber 2 by the conveying device 10. Here, the two substrates are arranged parallel to each other so that the sides of the substrates to be coated face each other. In addition, in this embodiment, the reaction chamber 2 has a temperature of 1100°C.

[0060] In order to introduce the gaseous silicon precursor compound and the process gas, two gas inlets 11, 12 are provided on the reaction chamber 2 in the region of the inlet 8, through which the gaseous silicon precursor compound and the process gas can be introduced into the reaction chamber separately from each other. In the present embodiment, high-purity hydrogen is used as the process gas. By introducing the gaseous silicon precursor compound and the process gas separately, the formation of parasitic deposits in the gas inlets 11, 12 can be prevented.

[0061] In addition, the gas inlets 11 and 12 are connected to fluid supply pipes 13 and 14, respectively, through which silicon precursor compounds and process gases can be supplied to the gas inlets 11 and 12. In the current embodiment, silicon tetrachloride is used as the silicon precursor compound. Since silicon tetrachloride has a boiling point of 57.6°C and is therefore liquid at room temperature, an evaporator 15 is provided on the fluid supply pipe 13. Before silicon tetrachloride is passed into the reaction chamber 2, the liquid silicon tetrachloride is converted into a gaseous state by the evaporator 15.

[0062] In order to be able to draw out an excess gas mixture consisting of excess silicon precursor compounds, silicon-based intermediate products and process gases from the reaction chamber 2 after the substrate is coated with silicon, the reaction chamber 2 has a gas outlet 16 in the region of the outlet 9. The gas outlet 16 is connected to a circulation line 5, which is used to return at least one component of the excess gaseous mixture, which component is selected from the group consisting of silicon precursor compounds, silicon-based intermediate products and / or process gases, to the reaction chamber 2. In addition, the circulation line 5 is connected to a fluid supply line 13.

[0063] In the current embodiment, a gas scrubber 6, a recovery unit 7 and a measuring unit 3 are arranged on the circulation pipe 5, and the gas scrubber 6, the recovery unit 7 and the measuring unit 3 are interconnected through a continuous circulation pipe 5 and are connected from one side of the gas outlet 16 to one side of the fluid supply pipe 13.

[0064] The gas scrubber 6 is used to increase the concentration of the excess gaseous mixture drawn from the reaction chamber by bringing the drawn gaseous excess gas into contact with a scrubbing liquid in the gas scrubber 6, whereby the excess usable components can be absorbed into the scrubbing liquid. The components passed through can be solid, liquid or gaseous substances. Chlorosilane can be used as the scrubbing liquid, for example.

[0065] The purified excess gaseous mixture can enter the recovery unit 7 through the circulation pipeline 5. In the current embodiment, the recovery unit 7 is configured as a distillation separation device. The recovery unit is used to separate the silicon precursor compound and / or the silicon-based intermediate product from the process gas. In addition, the recovery unit 7 also enables the separation of undesirable by-products of chemical vapor deposition from the circulation pipeline 5.

[0066] In order to determine the molar ratio of the silicon precursor compound and the silicon-based intermediate product, a measuring unit 3 is provided on the circulation pipe 5. In the current embodiment, the measuring unit is configured as an infrared spectrometer, which measures the concentration of the silicon-based intermediate product and the silicon precursor compound in the gas flow of the circulation pipe 5 and thereby determines the molar ratio of the silicon-based intermediate product and the silicon precursor compound. However, optionally, the measuring unit 3 may also be configured as a Coriolis mass flowmeter. However, the present invention is not limited thereto.

[0067] In order to regulate the supply of silicon precursor compounds in the reaction chamber 2, a control unit 4 is arranged on the fluid supply conduit 13, which control unit can be configured as a gas flow regulator, for example. The control unit 4 is also used to control the molar ratio of the silicon-based intermediate product to the silicon precursor compound when passing into the reaction chamber 2. For this purpose, the control unit 4 is connected to the measuring unit 3.

[0068] The molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous mixture in the circulation conduit 5 determined by the measuring unit 3 is transmitted to the control unit 4. In order to obtain the desired molar ratio of the silicon-based intermediate product to the silicon precursor compound in the process gas in the reaction chamber 2 of 0.2:0.8 to 0.5:0.5, preferably 0.3:0.7 to 0.5:0.5, particularly preferably 0.5:0.5, the control unit 4 controls the amount of silicon precursor compound supplied to the reaction chamber via the fluid supply conduit 13 and the gas inlet 12, depending on the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous mixture in the circulation conduit 5 determined by the measuring unit 4. In the present embodiment, the control unit 4 and the measuring unit 3 are electrically connected to each other, whereby the measured values ​​of the measuring unit 3 are automatically transmitted to the control unit 4. However, it is also within the scope of the invention that the user of the device 1 reads the determined molar ratio and transmits it manually to the control unit 4.

[0069] Figure 2 A second embodiment of an apparatus 1 for continuously vapour-depositing silicon on a substrate according to the present invention is shown. The apparatus 1 has substantially the same Figure 1 The design scheme described in the previous section has the same structure, so further details will not be discussed first.

[0070] In order to adjust the silicon precursor compound and process gas supplied to the reaction chamber 2, a control unit 4 is arranged on the fluid supply pipes 13 and 14. The control unit 4 is used to control the molar ratio of the silicon-based intermediate product to the silicon precursor compound when entering the reaction chamber 2, and is used to adjust the total amount of the silicon-based intermediate product and the silicon precursor compound in the process gas to a molar ratio of 1 to 10 mol%, preferably 2 to 7 mol%, and particularly preferably 3 to 6 mol% in step (c). In this embodiment, the control unit 4 is also connected to the measuring unit 3.

[0071] It is also within the scope of the invention to discharge excess process gas and / or silicon-based intermediate products and / or silicon precursor compounds from the device. In the present exemplary embodiment, for this purpose, the gas scrubber has a gas outlet 17 with a discharge line 18, through which excess process gas is discharged. However, the invention is not limited to this. Furthermore, the distillation separation device can also have a gas outlet with a discharge line.

[0072] Figure 3A third embodiment of an apparatus 1 for continuously vapour-depositing silicon on a substrate according to the present invention is shown. The apparatus 1 has substantially the same Figure 1 The design scheme described in the previous section has the same structure, so further details will not be discussed first.

[0073] The circulation line 5 is divided into three separately distributed sub-lines 51, 52, 53 for process gases after the recovery unit 7. It is within the scope of the invention to provide more than three separately distributed sub-lines downstream of the recovery unit, in particular in order to return other gases, such as hydrogen chloride, separately. The corresponding mass flow or volume flow is determined by means of separate measuring units 31, 32, 33, which are arranged on the sub-lines 51, 52, 53 downstream of the recovery unit 7. From this, the molar ratio of silicon-based intermediate products to silicon precursor compounds can be determined. Figure 3 As shown, the recovered process gas is then supplied to the fluid supply conduit 14 , while the silicon-based intermediate product and the silicon precursor compound are supplied to the fluid supply conduit 13 .

Claims

1. A method for continuously vapour-depositing silicon on a substrate, The following steps are involved: (a) introducing at least one substrate into a reaction chamber (2); (b) introducing a process gas and at least one gaseous silicon precursor compound into the reaction chamber (2); (c) forming a gaseous mixture of at least one silicon-based intermediate product and the process gas in the presence of the gaseous silicon precursor compound in the reaction chamber (2); (d) forming a silicon layer by vapor depositing silicon on the substrate from the gaseous silicon precursor compound and / or the silicon-based intermediate product; (e) removing excess of the gaseous mixture from the reaction chamber (2); It is characterized in that The method further comprises a step (f), in which an excess of at least one component of the gaseous mixture is returned to the reaction chamber (2), the component being selected from the silicon precursor compound, the silicon-based intermediate product and / or the process gas, wherein the gaseous silicon precursor compound is introduced into the reaction chamber (2) in such a manner that in the process gas, the molar ratio of the silicon-based intermediate product to the silicon precursor compound is in the range of 0.2:0.8 to 0.5:0.5, and the silicon precursor compound is present in the gas supply flow in excess or in the same amount as the silicon-based intermediate product.

2. The method according to claim 1, It is characterized in that The gaseous silicon precursor compound is introduced into the reaction chamber (2) in such a manner that the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the process gas is between 0.3:0.7 and 0.5:0.

5.

3. The method according to claim 2, It is characterized in that The gaseous silicon precursor compound is introduced into the reaction chamber (2) in such a manner that the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the process gas is 0.5:0.

5.

4. The method according to claim 1, It is characterized in that In step (f), the molar ratio of the silicon-based intermediate product to the silicon precursor compound in the excess gaseous mixture is determined by a measuring unit.

5. The method according to claim 4, It is characterized in that The molar ratio of the silicon-based intermediate product to the silicon precursor compound determined by the measuring unit is sent to a control unit, and the control unit adjusts the introduction of the silicon precursor compound so that in the process gas, the molar ratio between the silicon-based intermediate product and the silicon precursor compound is 0.2:0.8 to 0.5:0.

5.

6. The method according to claim 5, It is characterized in that The molar ratio of the silicon-based intermediate product to the silicon precursor compound determined by the measuring unit is sent to a control unit, and the control unit adjusts the introduction of the silicon precursor compound so that in the process gas, the molar ratio between the silicon-based intermediate product and the silicon precursor compound is 0.3:0.7 to 0.5:0.

5.

7. The method according to claim 6, It is characterized in that The molar ratio of the silicon-based intermediate product to the silicon precursor compound determined by the measuring unit is sent to a control unit, and the control unit adjusts the introduction of the silicon precursor compound so that the molar ratio between the silicon-based intermediate product and the silicon precursor compound in the process gas is 0.5:0.

5.

8. The method according to claim 1, It is characterized in that In step (f), impurities are removed from the excess of said gaseous mixture and / or are at least partially separated from the excess of said gaseous mixture by means of a recovery unit (7).

9. The method according to claim 8, It is characterized in that In step (f), the silicon-based intermediate product and / or the silicon precursor compound and / or the process gas are returned to the reaction chamber (2) via a circulation pipe (5).

10. The method according to claim 1, It is characterized in that The silicon precursor compound is chlorosilane.

11. The method according to claim 10, It is characterized in that The silicon precursor compound is silicon tetrachloride and / or trichlorosilane.

12. The method according to claim 1, It is characterized in that The process gas is hydrogen.

13. The method according to claim 1, It is characterized in that The silicon-based intermediate product is chlorosilane.

14. The method according to claim 13, It is characterized in that The silicon-based intermediate product is trichlorosilane and / or dichlorosilane.

15. The method according to claim 1, It is characterized in that In step (c), the total amount of the silicon precursor compound and the silicon-based intermediate product is present in the process gas in a molar ratio of 1 to 10 mol%.

16. The method according to claim 15, It is characterized in that In step (c), the total amount of the silicon precursor compound and the silicon-based intermediate product is present in the process gas in a molar ratio of 2 to 7 mol%.

17. The method according to claim 16, It is characterized in that In step (c), the total amount of the silicon precursor compound and the silicon-based intermediate product is present in the process gas in a molar ratio of 3 to 6 mol%.

18. The method according to claim 1, It is characterized in that The silicon layer is formed by vapor depositing silicon on a substrate from the silicon precursor compound and / or the silicon-based intermediate product under a pressure of 0.8 to 1.2 bar in the reaction chamber (2).

19. The method according to claim 1, It is characterized in that In the reaction chamber (2), at least the substrate is heated to a temperature of 700° C. to 1400° C.

20. The method according to claim 19, It is characterized in that In the reaction chamber (2), at least the substrate is heated to a temperature of 1000° C. to 1300° C.

21. The method according to claim 20, It is characterized in that In the reaction chamber (2), the substrate is heated to at least a temperature of 1100° C. to 1200° C.

22. A device (1) for carrying out the method for continuously vapour-depositing silicon on a substrate according to any one of claims 1 to 21, said device include: a reaction chamber (2), said reaction chamber (2) comprising at least one inlet (8) for the substrate and at least one outlet (9) for the substrate; a conveying device (10) for conveying the substrate from the inlet (8) to the outlet (9) through the reaction chamber (2); at least two gas inlets (11, 12) for supplying gas into the reaction chamber (2); at least one gas outlet (16) for conducting the gas out of the reaction chamber (2); at least two fluid supply pipes (13, 14), the at least two fluid supply pipes (13, 14) being connected to the two gas inlets (11, 12) of the reaction chamber (2); It is characterized in that The device (1) has at least one control unit (4), and at least one circulation pipeline (5) is arranged between the gas outlet (16) and the gas inlet (12) of the reaction chamber (2), and the circulation pipeline (5) is connected to the fluid supply pipeline (13) and the gas outlet (16) of the reaction chamber (2). The device (1) has at least one measuring unit (3), and the measuring unit (3) is used to measure the molar ratio of the silicon-based intermediate product to the silicon precursor compound and / or a value equivalent to the molar ratio. The control unit (4) and the measuring unit (3) are configured to operate in coordination so that the flow rate of the supply pipeline (13, 14) can be controlled or adjusted based on a signal sent by the measuring unit (3) to the control unit (4).

23. The device according to claim 22, It is characterized in that The at least two fluid supply pipes (13, 14) are gas supply pipes.

24. The device according to claim 22, It is characterized in that The measuring unit (3) is arranged on the circulation pipe (5).

25. The apparatus according to claim 22, It is characterized in that The measuring unit (3) is configured as a spectrometer, a mass flow meter or a volume flow meter.

26. The apparatus according to claim 22, It is characterized in that At least one of the fluid supply conduits (13, 14) has an evaporator (15) for converting the silicon precursor compound and / or the silicon-based intermediate product into a gaseous state.

27. The apparatus according to claim 22, It is characterized in that The circulation pipeline (5) has a gas scrubber (6) and / or a recovery unit (7).

28. The device according to claim 27, It is characterized in that The recovery unit (7) is configured as a distillation separation device and / or has a dry absorber or a dry adsorber.

29. The apparatus according to claim 27, It is characterized in that The circulation pipeline (5) has a plurality of branch pipelines (51, 52, 53) between the recovery unit (7) and the fluid supply pipeline (13, 14), and the branch pipelines (51, 52, 53) are used to return the process gas, the silicon-based intermediate product and / or the silicon precursor compound separately, and each of the branch pipelines (51, 52, 53) has a separate measuring unit (31, 32, 33), and the measuring unit (31, 32, 33) is used to measure the mass flow rate and / or volume flow rate of the process gas, the silicon-based intermediate product and / or the silicon precursor compound.

Images