Byproduct removal method for SiC epitaxial growth device

Abstract

A SiC epitaxial growth apparatus according to one embodiment is provided with: a chamber into which a process gas containing at least silicon and carbon is introduced and which is capable of accommodating a substrate on which a film is formed by the process gas; a pipe that discharges a gas containing by-products generated along with film formation of the substrate from the chamber; and a pressure control valve provided in the middle of the piping. The valve has an inflow port into which gas flows from an upstream portion of a pipe that communicates the chamber and the valve, and an outflow port through which gas flows out toward a downstream portion of the pipe that communicates with the upstream portion via the valve. A portion of the upstream portion is provided at least at a position lower than the inflow port, or a portion of the downstream portion is provided at a position lower than the outflow port.

Description

[0001] This application is a divisional application of the application with application number "202080007995.8", application date April 8, 2020, and invention name "SiC epitaxial growth device". Technical Field

[0002] An embodiment of the present invention relates to a SiC epitaxial growth apparatus. Background Art

[0003] As one type of epitaxial growth apparatus that uniformly forms a thin film on a single crystal substrate having a wide area, there is a SiC epitaxial growth apparatus. The SiC epitaxial growth apparatus forms a SiC single crystal thin film on a substrate using a process gas containing silicon (Si), carbon (C), etc.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2010-222148 Summary of the invention

[0007] Problem that the invention aims to solve

[0008] The SiC epitaxial growth device discharges byproducts generated during SiC film formation. Byproducts are generally explosive, and especially when the film formation gas contains chlorine, fluid byproducts are generated, and safety considerations are particularly important when removing them.

[0009] It is known that such byproducts will liquefy near the valve for pressure control in the exhaust path, that is, the location where the pressure changes. Moreover, the viscosity of the liquefied byproduct is relatively high, so it is easy to remain in the valve. Therefore, frequent replacement and cleaning of the valve is required.

[0010] An embodiment of the present invention provides a SiC epitaxial growth apparatus in which byproducts accompanying SiC epitaxial growth are less likely to remain in a valve provided in the middle of a discharge path, and the frequency of valve replacement and cleaning can be reduced.

[0011] Means used to solve problems

[0012] An SiC epitaxial film forming apparatus according to one embodiment includes: a chamber into which a raw material gas containing at least silicon and carbon is introduced and which can accommodate a substrate formed by the raw material gas; a pipe that discharges a gas containing a byproduct generated accompanying the film forming of the substrate from the chamber; and a valve for pressure control, which is arranged in the middle of the pipe. The valve has an inlet for allowing gas to flow in from an upstream portion of the pipe connecting the chamber to the valve, and an outlet for allowing gas to flow out toward a downstream portion of the pipe connecting to the upstream portion via the valve. At least a part of the upstream portion is arranged at a position lower than the inlet, or a part of the downstream portion is arranged at a position lower than the outlet.

[0013] Effects of the Invention

[0014] According to one embodiment, byproducts accompanying the epitaxial growth of SiC are less likely to remain in a valve provided in the middle of a discharge path, and the replacement frequency of the valve can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a diagram showing a schematic configuration of a SiC epitaxial growth apparatus according to the first embodiment.

[0016] Figure 2 It is a diagram showing a schematic configuration of a SiC epitaxial growth apparatus according to a comparative example.

[0017] Figure 3 This is a schematic diagram showing a modified example in which the outflow port of the valve is arranged obliquely downward.

[0018] Figure 4 This is a graph showing the relationship between the pipe diameter and the amount of residual by-products.

[0019] Figure 5 is used for Figure 4 The piping structure of the experimental results shown in .

[0020] Figure 6 Is based on Figure 4 The experimental results shown in FIG. 1 and the pipe length when the by-product amount ratio becomes 0.05 are shown in FIG.

[0021] Fig. 7A This is a schematic diagram showing a modified example in which the collecting section is arranged on the downstream side of the lowest portion of the upstream portion.

[0022] Figure 7B This is a schematic diagram showing that the collecting section is arranged on the upstream side of the lowest part of the downstream portion.

[0023] Fig. 8A This is a schematic diagram showing a modified example of a valve in which the inlet and outlet are open in the vertical direction.

[0024] Figure 8BThis is a schematic diagram showing a modified example of a valve in which the inlet and outlet are opened in the horizontal direction.

[0025] Fig. 9A This is a schematic diagram showing a modified example in which the collecting section is branched from the pipe.

[0026] Fig. 9B This is a schematic diagram showing another modified example in which the collecting section is branched from the pipe.

[0027] Fig. 9C This is a schematic diagram showing still another modified example in which the collecting section is branched from the pipe.

[0028] Fig.10 It is a diagram showing a schematic configuration of a SiC epitaxial growth apparatus according to a second embodiment. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments of the present invention will be described with reference to the drawings. These embodiments do not limit the present invention.

[0030] (First embodiment)

[0031] Figure 1 1 is a diagram showing a schematic configuration of a SiC epitaxial growth apparatus according to Embodiment 1. In this embodiment, an example is described in which a semiconductor wafer W is used as a substrate for epitaxial growth and a single film or a plurality of thin films are stacked on the semiconductor wafer W for vapor phase epitaxial growth.

[0032] Figure 1 The SiC epitaxial growth apparatus 1 shown in FIG. 1 includes a chamber 10, a pipe 20, a valve 30, a collecting unit 40, a pump 50, a pressure sensor 60, a control unit 70, and a detoxification device 80. Hereinafter, each component of the SiC epitaxial growth apparatus 1 will be described.

[0033] The semiconductor wafer W is stored in the chamber 10 in a state of being placed on the platform 11. The placed wafer may be a single wafer, or multiple wafers may be placed at the same time. In addition, a process gas G1 is introduced into the chamber 10. In the present embodiment, the process gas G1 contains silicon, carbon and chlorine (Cl). As a gas containing silicon, for example, monosilane (SiH4) or dichlorosilane (SiH2Cl2) or trichlorosilane (SiHCl3) may be used. As a gas containing carbon, for example, propane (C3H8) or acetylene (C2H2) may be used. As a gas containing chlorine, for example, hydrogen chloride (HCl) may be used. In addition, hydrogen (H2) or argon (Ar) as a carrier gas may also be flowed in at the same time as one of the process gases. In addition, nitrogen (N2) or trimethylaluminum (TMAl) as a doping gas may also be added. When the process gas G1 is introduced into the chamber 10 and the wafer is heated to, for example, 1650°C using a heating source such as a heater (not shown), a SiC single crystal thin film is formed on the semiconductor wafer W, and by-products are generated at the same time.

[0034] In the present embodiment, the byproduct is a polymer containing at least silicon, hydrogen (H), chlorine, and carbon. The exhaust gas G2 is discharged from the chamber 10 toward the pipe 20, and the byproduct is generated as a polymer in the gas flowable portion after the pipe 20.

[0035] The pipe 20 has an upstream portion 21 that connects the chamber 10 to the valve 30, and a downstream portion 22 that connects to the upstream portion 21 via the valve 30. Figure 1 As shown, one end of the upstream portion 21 is connected to the bottom surface of the chamber 10. Alternatively, one end of the upstream portion 21 can also be connected to the side surface of the chamber 10.

[0036] like Figure 1 As shown, the upstream portion 21 and the downstream portion 22 are bent into a U-shape. That is, there is a bent portion at the lower portion. A valve 30 is provided between the upper end portion of the upstream portion 21 and the upper end portion of the downstream portion 22.

[0037] The valve 30 includes a valve box 31 and a valve body 32. An inlet 31a and an outlet 31b are provided in the valve box 31. The exhaust gas G2 discharged from the chamber 10 toward the upstream portion 21 of the pipe 20 flows into the inlet 31a. In the present embodiment, the inlet 31a opens in the horizontal direction and is connected to the upper end of the upstream portion 21 bent in a U shape.

[0038] The outflow port 31b allows the exhaust gas G2 flowing into the inflow port 31a to flow out toward the downstream portion 22. In the present embodiment, the outflow port 31b opens vertically downward and is connected to the upstream upper end portion of the downstream portion 22 bent in a U-shape.

[0039] The valve body 32 operates in the valve box 31 based on the control of the control unit 70. The opening of the valve 30, in other words, the flow pressure of the exhaust gas G2 at the inlet 31a changes due to the operation of the valve body 32. By controlling the operation of the valve body 32, the internal pressure of the upstream portion 21 of the pipe 20 and the chamber 10 can be controlled.

[0040] The collecting section 40 is provided at the lower end of the downstream portion 22 bent into a U-shape. That is, the collecting section 40 is provided at a position lower than the valve 30. Thus, the byproduct X discharged from the outlet 31b of the valve 30 is accumulated in the lower part of the collecting section 40. Figure 1 As shown, the lower portion of the collecting section 40 is provided below the pipe 22, and the inner diameter d1 of the collecting section 40 is much larger than the inner diameter d2 of the pipe 22. That is, in a plane perpendicular to the flow direction of the exhaust gas G2, the collecting section 40 has a sufficiently large cross-sectional area relative to the pipe 22, so even if the byproduct X accumulates in the collecting section 40, the flow path of the exhaust gas G2 is ensured in the collecting section 40. Therefore, the flow of the exhaust gas G2 at the downstream portion 22 is not hindered.

[0041] However, if the accumulation of the byproduct X increases in the collecting section 40, the collecting section 40 needs to be replaced. Therefore, it is preferred that at least the downstream portion 22 of the collecting section 40 is installed in a replaceable manner. Furthermore, the method for installing the downstream portion 22 of the collecting section 40 is not particularly limited, but a simple method is preferably used in which the time required for the replacement operation is shortened. In addition, the collecting section 40 can be provided not only in the downstream portion 22 but also in the upstream portion 21.

[0042] The pump 50 is a vacuum pump provided downstream of the collecting unit 40. The pump 50 performs a decompression operation to make the inside of the pipe 20 and the chamber 10 a vacuum state. The exhaust gas G2 is sucked from the chamber 10 into the pipe 20 by the decompression operation.

[0043] The pressure sensor 60 is provided in the chamber 10 . Alternatively, the pressure sensor 60 may be provided in the upstream portion 21 of the pipe 20 . The pressure sensor 60 detects the internal pressure of the chamber 10 and outputs the detected internal pressure to the control unit 70 .

[0044] The control unit 70 receives the result obtained by monitoring the pressure inside the chamber 10 in the SiC epitaxial growth device 1 using the pressure sensor 60, and controls the opening of the valve 30 in such a way that the pressure inside the chamber 10 becomes a pressure suitable for vapor phase epitaxial growth, for example, 200 Torr, or in such a way that the pressure inside the chamber 10 becomes a pressure suitable for each step of the film forming process, thereby controlling the introduction of the process gas G1 or the discharge of the exhaust gas G2, etc.

[0045] The detoxification device 80 is provided to remove harmful gases contained in the exhaust gas G2 or render them harmless so as to release them into the atmosphere.

[0046] Figure 2 1 is a diagram showing a schematic configuration of a SiC epitaxial growth apparatus according to a comparative example. Figure 2 In, with Figure 1 The same components of the SiC epitaxial growth apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0047] Figure 2 In the SiC epitaxial growth apparatus 100 shown in FIG. 1 , the valve 30 is connected to the downstream portion 22 of the pipe 20 at a position lower than the collecting portion 40. In addition, the outlet 31b of the valve 30 opens vertically upward. Therefore, the byproduct X contained in the exhaust gas G2 is easily attached to the valve box 31 of the valve 30.

[0048] On the other hand, according to this embodiment, Figure 1 As shown, the outlet 31b of the valve 30 opens vertically downward. Therefore, the byproduct X adhering to the vicinity of the outlet 31b in the valve box 31 is facilitated to be discharged from the outlet 31b due to gravity. As a result, the byproduct X is less likely to adhere to the valve box 31, so the replacement frequency of the valve 30 can be reduced.

[0049] In the present embodiment, the outlet 31b opens vertically downward, but any structure may be used as long as it opens downward in a manner that promotes the discharge of the byproduct X generated near the valve body 32 inside the valve 30 from the outlet 31b due to gravity. Figure 3 As shown, the outlet 31b of the valve 30 may also open obliquely downward.

[0050] Alternatively, even if the outflow port 31b opens in the horizontal direction, the byproducts are not accumulated and the discharge of the byproducts from the valve 30 is promoted. That is, when the outflow port 31b opens in the horizontal direction, the pipe connected thereto is also oriented in the horizontal direction, but if the length of the horizontal portion of the pipe is sufficiently short relative to the pipe diameter, the byproducts are not accumulated in the valve 30 and the discharge of the byproducts is promoted.

[0051] Since the length of the horizontal portion that allows byproducts to be discharged without accumulating near the valve depends on the pipe diameter, the relationship between the pipe diameter (inner diameter) and the amount of residual byproducts was investigated. When the inner diameter (D) of the pipe was set to 40 mm, 50 mm, and 100 mm, and the length of the horizontal portion of the pipe (pipe length: L) was changed to 2000 mm, the amount of byproducts (v) accumulated in the horizontal portion of the pipe was actually measured, and the results were as follows: Figure 4 The study used Figure 5 Here, Figure 4 The horizontal axis represents the horizontal length (L) of the exhaust pipe, and the vertical axis represents the amount of byproducts accumulated in the horizontal portion (v) relative to the volume of the horizontal portion of the exhaust pipe (V = (L * π * (D / 2)2 ))'s ratio (v / V).

[0052] like Figure 5 As shown in FIG. 1 , as long as there is a horizontal portion in the pipe 22 connected from the valve outlet 31b, a certain amount of byproducts will accumulate in the horizontal portion. If the amount is less than 5% of the volume of the horizontal portion of the pipe, the amount of byproduct accumulation can be ignored. Figure 4 In the above example, find the length L of the pipe with the vertical axis of each plotted value being 0.05. The result is as follows: Figure 6 As shown. The plot of the three points is roughly located on a straight line where the vertical axis is 16 times the horizontal axis. That is, if the length of the pipe is less than 16 times the diameter of the horizontal portion of the pipe, it can be said that the accumulation in the pipe can be ignored. However, although it does not affect the exhaust, considering the frequency of replacement / cleaning of the pipe, it is better to minimize the amount that does not flow into the collection section 40 and accumulates in the horizontal portion, so it is more preferably less than 2 times, and more preferably less than 1 time.

[0053] In addition, according to the present embodiment, the collecting section 40, which is thicker than the pipe 20 (has a larger pipe cross-sectional area), is connected to the downstream portion 22 at a position lower than the valve 30. Therefore, the byproduct X is more likely to be accumulated in the collecting section 40 than in the valve 30. In addition, the byproduct X can be accumulated in the collecting section 40 without hindering the flow of the exhaust gas G2 at the downstream portion 22.

[0054] Furthermore, the collecting portion 40 may be Fig. 7A As shown, it is arranged on the downstream side of the lowest part 21a of the upstream part 21, and can also be Figure 7B As shown, the collecting portion 40 is provided on the upstream side of the lowermost portion 22a of the downstream portion 22. That is, the collecting portion 40 may be provided between the lowermost portion 21a of the upstream portion 21 and the lowermost portion 22a of the downstream portion 22.

[0055] Alternatively, valve 30 may be Fig. 8A As shown, the inlet 31a opens vertically upward, and the outlet 31b opens vertically downward.

[0056] Alternatively, valve 30 may also be Figure 8B As shown, the inlet 31a and the outlet 31b open opposite to each other in the horizontal direction.

[0057] As for the length of the horizontal pipe at this time, the pipe 22 connected from the valve outlet 31b is preferably 16 times or less of the inner diameter D of the pipe as described above. On the other hand, the same study as that for the pipe connected to the outlet was conducted for the pipe 21 connected from the valve inlet 31a, and the same results were obtained. Figure 6Therefore, regarding the pipe 21 connected to the inlet 31a of the valve, it is preferred that the length of the horizontal portion is also 16 times or less of the pipe diameter. It is preferably 2 times or less, and more preferably 1 time or less.

[0058] Furthermore, if Fig. 9A As shown, the collecting section 40 may be configured to store the byproduct X in a portion branched from the lowermost portion rather than in the middle of the pipe 21. With this configuration, the collecting section 40 can be replaced by removing only one portion of the pipe 21.

[0059] In addition, if Fig. 9B As shown, it is preferable to provide a valve V in the middle of the vertical pipe 21b connecting the pipe 21 and the collecting section 40. With this configuration, when the exhaust gas G2 flows out (during film formation), the valve V is first opened to allow the byproduct X to be accumulated in the collecting section 40. On the other hand, when the exhaust gas G2 does not flow out, the valve V is closed, the downstream side of the valve V is made to have atmospheric pressure by a pressure adjustment mechanism (not shown), and the collecting section 40 is removed at the dividing section 21c. Furthermore, the byproduct X accumulated in the collecting section 40 is removed from the collecting section 40, and the inside is preferably cleaned by water washing or the like. Thereafter, the collecting section 40 is connected again, and after the pressure is reduced by a pressure adjustment mechanism (not shown), the valve V is opened to have the same pressure as that of the pipe 21, and film formation is performed. By doing so, when the collecting section 40 is removed, it is not necessary to open the entire pipe 20 to the atmosphere, and operability can be improved.

[0060] In addition, when the exhaust gas G2 flows out (during film formation), the valve V is closed to accumulate the reaction byproduct X in the pipe 21. When the exhaust gas G2 does not flow out, the valve V is opened to transfer the byproduct accumulated in the pipe 21 to the collection unit 40. Then, after the valve V is closed, the downstream side of the valve V is made to be atmospheric pressure by a pressure adjustment mechanism (not shown), and the collection unit 40 is removed from the dividing portion 21c. By doing so, when the collection unit 40 is set upstream of the pressure control valve 31, the volume of the pipe between the chamber 10 and the pressure control valve 31 can be reduced, so that the pressure control by the control unit 70 can be performed more easily.

[0061] Furthermore, if Fig. 9CAs shown, the piping 21 may be branched, and valves Vi, Vo, and a collecting section 40 may be provided in each pipeline. For example, by forming a film in a state where Vi and Vo of one pipeline are closed and Vi and Vo of another pipeline are opened, the byproduct X is accumulated only in the collecting section 40 connected to one pipeline. In a state where the byproduct is accumulated, the pressure of one pipeline where the byproduct has not yet been accumulated may be reduced by a pressure regulating mechanism (not shown), and then Vi and Vo on both sides of the pipeline may be opened, and then Vi and Vo on both sides of the pipeline where the byproduct is accumulated may be closed, and the pressure may be changed to atmospheric pressure by a pressure regulating mechanism (not shown), and the collecting section 40 may be removed at the dividing section 21c. By doing so, if the byproduct X is accumulated in the collecting section 40 of one pipeline, the gas flow system may be switched to accumulate the byproduct X in the collecting section 40 of the other pipeline, and the operability may be further improved.

[0062] (Second embodiment)

[0063] Fig.10 1 is a diagram showing a schematic configuration of a SiC epitaxial growth apparatus according to a second embodiment. Fig.10 In, with Figure 1 The same components of the SiC epitaxial growth apparatus 1 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0064] Fig.10 In the SiC epitaxial growth device 2 shown in , the outlet 31b of the valve 30 opens in the horizontal direction and is connected to the downstream portion 22 of the pipe 20, while the inlet 31a opens vertically downward and is connected to the upstream portion 21. Therefore, when the exhaust gas G2 is discharged, the by-product X attached to the vicinity of the inlet 31a in the valve box 31 is promoted to be discharged from the inlet 31a to the upstream portion 21 due to gravity. Therefore, it is difficult for the by-product X to adhere to the valve box 31, so the replacement frequency of the valve 30 can be reduced. At this time, as shown in FIG. Figure 3 As shown, the inlet 31 a may also open obliquely downward and be connected to the upstream portion 21 .

[0065] In addition, a collecting section 40 is provided at a position lower than the valve 30 in the upstream portion 21. The byproduct X discharged from the inlet 31a can be stored in the collecting section 40.

[0066] Furthermore, in the present embodiment, the inner diameter d1 of the collecting section 40 is larger than the inner diameter d2 of the pipe 20. Therefore, the byproduct X can be accumulated in the collecting section 40 without hindering the flow of the exhaust gas G2 at the upstream portion 21. Furthermore, if the storage amount of the byproduct X increases, it is necessary to replace the collecting section 40. Therefore, it is preferable that the collecting section 40 is installed in the upstream portion 21 in a replaceable manner. In addition, the collecting section 40 can be provided not only in the upstream portion 21 but also in the downstream portion 22.

[0067] In this case, as in the first embodiment, the upstream portion 21 of the valve 30 may have a horizontal portion. In this case, the length of the horizontal portion is preferably 16 times or less, preferably 2 times or less, and more preferably 1 time or less, the pipe diameter.

[0068] The embodiments of the present invention have been described, but the embodiments are presented as examples and are not intended to limit the scope of the invention. The embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the scope of the invention. The embodiments and their variations are included in the scope or spirit of the invention, and are included in the invention recorded in the claims and their equivalents.

Claims

1. A method for removing byproducts of a SiC epitaxial growth device, comprising the following steps: A substrate is placed in a chamber, and a process gas containing at least silicon, carbon, and chlorine is introduced onto the substrate to epitaxially grow a SiC film; exhausting a gas containing byproducts generated along with epitaxial growth on the substrate and containing at least silicon, hydrogen, and chlorine from the chamber to a pipe; adjusting the internal pressure of the chamber and the pressure in the pipe on the upstream side of the valve provided in the middle of the pipe; liquefying the by-product in the valve by pressure changes in the pipe on the upstream side of the valve and the pipe on the downstream side of the valve; discharging the liquefied by-product to the upstream pipe or the downstream pipe by gravity; and The by-product discharged to the upstream pipe or the downstream pipe is removed.

2. The method for removing byproducts of a SiC epitaxial growth device according to claim 1, wherein: The by-product discharged to the upstream pipe or the downstream pipe is accumulated in a collecting portion provided in the upstream pipe or the downstream pipe and removed.

3. The method for removing byproducts of a SiC epitaxial growth device according to claim 2, wherein: The by-products are removed by removing the collecting section from the upstream pipe or the downstream pipe.

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