Epitaxial wafer manufacturing method and epitaxial growth apparatus

Abstract

To remove polysilicon that accumulates on a susceptor surface after an epitaxial layer is formed, and also suppress metal contamination caused by deterioration of a back surface of the susceptor.SOLUTION: In an epitaxial wafer manufacturing method using an epitaxial growth apparatus 10, an upper gas G1 containing a silane-based gas and a carrier gas is introduced into an upper space S1 at a first upper gas flow rate, and a lower gas G2 flowing into a lower space S2 is introduced at a first lower gas flow rate during film formation to form an epitaxial layer on a semiconductor substrate W. The upper / lower flow rate ratio during film formation, which is the first lower gas flow rate / the first upper gas flow rate, is set to (0.015 to 0.045)×X (X is volume V2 of the lower space / volume V1 of the upper space), and when etching is performed by introducing a gas containing hydrogen chloride and the carrier gas into the upper space, the upper / lower flow rate ratio during etching, which is a second lower gas flow rate / a second upper gas flow rate, is set to be larger than the upper / lower flow rate ratio during film formation and equal to or less than 1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing an epitaxial wafer and an epitaxial growth apparatus. [Background technology]

[0002] In recent years, there has been a demand for further reduction in contamination of the epitaxial layer during the manufacture of epitaxial wafers. In order to reduce metal contamination of the epitaxial layer, for example, it has been proposed to change the ratio of gas flow rates between the top and bottom during the deposition of the epitaxial layer.

[0003] Patent Document 1 discloses a method for forming a low-carbon epitaxial layer in an epitaxial layer deposition apparatus (CVD apparatus) in which the ratio of the combined flow rates of slit purge gas and main purge gas flowing through the lower space to that of 20.5 or less is set when the flow rate of the process gas flowing through the upper space during epitaxial layer deposition is taken as 100, thereby suppressing the uplifting of carbon atmosphere from the lower space to the upper space.

[0004] Patent Document 2 discloses a method for growing an epitaxial layer in advance by determining a range of upper and lower gas flow ratios in which the level of metal contamination is relatively low. It also discloses that when changing the upper and lower gas flow ratios, it is desirable to adjust the ratio by changing only the lower H2 carrier gas flow rate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-4760 A [Patent Document 2] JP 2009-4424 A Summary of the Invention [Problem to be solved by the invention]

[0006] The disclosures of the above-mentioned prior art documents are incorporated herein by reference. The following analysis was conducted by the present inventors.

[0007] However, the cause of metal contamination of the epitaxial layer is not limited to the time of forming the epitaxial layer. During the formation of the epitaxial layer, the inside of the epitaxial layer forming device is cleaned (etched), and the contamination of the epitaxial layer caused by the deterioration of the back surface of the susceptor on which the epitaxial wafer is placed during the cleaning (etching) can also cause contamination of the epitaxial layer. Therefore, even if the contamination is suppressed during the formation of the epitaxial layer as in Patent Document 1 and Patent Document 2, it is not sufficient to suppress the contamination of the epitaxial layer.

[0008] In view of the above-mentioned problems, an object of the present invention is to provide a method for manufacturing an epitaxial wafer and an epitaxial growth apparatus that removes polysilicon that accumulates on the surface of a susceptor after formation of an epitaxial layer and suppresses metal contamination of the epitaxial wafer caused by deterioration of the back surface of the susceptor. [Means for solving the problem]

[0009] In order to achieve the above object, a method for manufacturing an epitaxial wafer is provided for growing an epitaxial layer on a semiconductor substrate by vapor phase growth using an epitaxial growth apparatus having a susceptor for mounting a semiconductor substrate thereon, an upper space having the susceptor disposed therein and located above the susceptor and through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part through which a lower gas flows, the upper gas and the lower gas flow from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port, and a controller for controlling the gas flow rates of the upper gas and the lower gas, An upper gas containing hydrogen chloride and a carrier gas is introduced from the upper gas inlet at a first upper gas flow rate, a lower gas flowing into the lower space is introduced from the lower gas inlet at a first lower gas flow rate, and an upper / lower flow rate ratio during film formation, which is the first lower gas flow rate / first upper gas flow rate, is set to (0.015 to 0.045) × X (where X = volume V2 of lower space / volume V1 of upper space), and during etching in which a gas containing hydrogen chloride and a carrier gas is introduced into the upper space to perform etching, an upper gas is introduced from the upper gas supply port at a second upper gas flow rate, and the lower gas flowing into the lower space is introduced from the lower gas supply port at a second lower gas flow rate, and the upper / lower flow rate ratio during etching, which is the second lower gas flow rate / second upper gas flow rate, is set to be larger than the upper / lower flow rate ratio during film formation and not more than 1.

[0010] In the above-mentioned epitaxial wafer manufacturing method, the upper gas is controlled so as not to flow from the upper space to the lower space as much as possible during etching, and conversely, the gas is controlled so as to flow from the upper space to the lower space as much as possible during deposition of the Si epitaxial layer. With this configuration, while removing the polysilicon deposited on the susceptor surface after deposition of the epitaxial layer, it is possible to suppress the HCl gas from reaching the back surface of the susceptor and coat the back surface of the susceptor with Si, thereby suppressing deterioration of the back surface of the susceptor and suppressing metal contamination caused by deterioration of the back surface of the susceptor.

[0011] In addition, in the above-mentioned method for producing an epitaxial wafer, the upper / lower flow rate ratio during etching is preferably set to (0.075 to 0.125) x X. When the lower gas is increased, the intrusion of HCl into the lower space is suppressed, and the transport of Fe to the surface side (i.e., the contamination is reduced), but if the lower gas is increased too much, the transport of contamination to the upper space increases.

[0012] In addition, in the above-mentioned method for producing an epitaxial wafer, it is preferable that during etching, the upper gas is exhausted without flowing into the lower space, and during deposition of an epitaxial layer, a part of the upper gas flows into the lower space via the communicating part. This is to prevent the deterioration of the susceptor rear surface by suppressing the arrival of HCl gas at the susceptor rear surface and coating the susceptor rear surface with Si while removing polysilicon deposited on the susceptor front surface after deposition of the epitaxial layer, and to suppress metal contamination caused by deterioration of the susceptor rear surface.

[0013] In addition, in the above-mentioned epitaxial wafer manufacturing method, it is preferable that the air pressure in the upper space is made higher than the air pressure in the lower space during deposition of an epitaxial layer on a semiconductor substrate, and the air pressure in the upper space is made lower than the air pressure in the lower space during etching, in order to prevent the upper gas from escaping from the upper space to the lower space as much as possible during etching, and conversely, to control the upper gas to escaping from the upper space to the lower space as much as possible during deposition of a Si epitaxial layer.

[0014] In the epitaxial wafer manufacturing method, the surface roughness of the back surface of the susceptor is preferably set to 7.5 to 17.5 μm. If the surface roughness of the susceptor 1 increases (=increased particle size), contamination of the substrate C increases, but if the surface roughness decreases, the stability of the wafer placement position decreases (wafer slippage), and slippage occurs due to a decrease in the uniformity of the in-plane temperature.

[0015] Further, in order to achieve the above object, there is provided a method for producing an epitaxial wafer, which comprises vapor-phase growing an epitaxial layer on a semiconductor substrate using an epitaxial growth apparatus having: a susceptor for mounting a semiconductor substrate thereon; an upper space having the susceptor installed therein and located above the susceptor and through which an upper gas flows; and a lower space located below the susceptor and communicating with the upper space via a communication part and through which a lower gas flows, the upper gas and the lower gas flow from an upper gas inlet and a lower gas inlet toward an exhaust outlet, the communication part being located between the susceptor and the exhaust outlet; and a controller for controlling the rotation speed of the susceptor, wherein it is preferable that the rotation speed of the susceptor is less than the rotation speed during film formation. By making the rotation speed of the susceptor during HCl etching faster than the rotation speed of the susceptor during epitaxial growth, it is possible to prevent the bottom gas (HCl) from entering the lower space during HCl etching and to prevent the bottom gas from rising to the upper space during epitaxial growth.

[0016] Specifically, it is preferable that the rotation speed of the susceptor is set to R=(6±3)×X during film formation and R=(15±6)×X during etching. If the rotation speed of the susceptor is slow during HCl etching, the upper gas G1 (HCl) will enter the lower space S2 and the back surface of the susceptor 1 will be excessively etched, causing contamination. On the other hand, if the rotation speed of the susceptor is fast during epitaxial growth, the lower gas G2 will rise into the upper space S1 and contaminate the epitaxial layer.

[0017] An epitaxial growth apparatus made to achieve the above object includes a susceptor for mounting a semiconductor substrate thereon, an upper space in which the susceptor is installed and located above the susceptor and through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part and through which a lower gas flows, the upper gas and the lower gas flow from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port, and a chamber in which an upper gas containing a silane-based gas and a carrier gas is introduced from the upper gas inlet at a first upper gas flow rate and a lower gas flowing into the lower space is preheated at a first lower gas flow rate during film formation of an epitaxial layer on a semiconductor substrate. and a controller that controls the gas flow rates of the upper gas and the lower gas so that an upper / lower flow rate ratio during etching, which is the second lower gas flow rate / the second upper gas flow rate, is greater than the upper / lower flow rate ratio during film formation and is equal to or less than 1, during etching, in which a gas containing hydrogen chloride and a carrier gas is introduced into the upper space from the upper gas supply port at a second upper gas flow rate and a lower gas flowing into the lower space from the lower gas supply port at a second lower gas flow rate, and the upper gas and the lower gas are introduced from the lower gas supply port at a second lower gas flow rate.

[0018] In the above epitaxial growth apparatus, the upper gas is controlled so as not to flow from the upper space to the lower space as much as possible during etching, and conversely, the gas is controlled so as to flow from the upper space to the lower space as much as possible during deposition of the Si epitaxial layer. With this configuration, while removing the polysilicon deposited on the susceptor surface after deposition of the epitaxial layer, it is possible to prevent the HCl gas from reaching the back surface of the susceptor and coat the back surface of the susceptor with Si, thereby preventing deterioration of the back surface of the susceptor and preventing metal contamination caused by deterioration of the back surface of the susceptor.

[0019] In addition, in the epitaxial growth apparatus, the upper / lower flow rate ratio during etching is preferably set to (0.075 to 0.125) x X. When the lower gas is increased, the intrusion of HCl into the lower space is suppressed and the Fe concentration on the epitaxial layer surface is reduced (i.e., contamination is reduced), but if the lower gas is increased too much, contamination transport to the upper space increases.

[0020] In order to achieve the above object, an epitaxial growth apparatus preferably includes a susceptor for mounting a semiconductor substrate thereon, an upper space in which the susceptor is installed and located above the susceptor, through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part through which a lower gas flows, the upper gas and the lower gas flow from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port, and a controller for controlling the rotation speed of the susceptor so that the rotation speed during film formation is smaller than the rotation speed during etching. By making the rotation speed of the susceptor faster during HCl etching than the rotation speed of the susceptor during epitaxial growth, it is possible to suppress the intrusion of the lower gas (HCl) into the lower space during HCl etching and to suppress the lower gas from rising to the upper space during epitaxial growth. Effect of the Invention

[0021] According to the present invention, it is possible to provide a method for manufacturing an epitaxial wafer and an epitaxial growth apparatus that removes polysilicon that accumulates on the surface of a susceptor after formation of an epitaxial layer and suppresses metal contamination caused by deterioration of the back surface of the susceptor. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram of an epitaxial growth apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flow chart showing an outline of the procedure of an embodiment of a method for producing an epitaxial wafer. [Diagram 3] FIG. 3 is a graph showing the relationship between the change in the flow rate of the lower gas H2 during HCl etching and the Fe concentration on the wafer surface. [Figure 4] FIG. 4 is a graph showing the relationship between the change in the flow rate of the lower gas H2 during epitaxial growth and the Fe concentration and film thickness uniformity on the wafer surface. [Diagram 5] FIG. 5 is a graph showing the relationship between the surface roughness of the susceptor and the Fe concentration and slip length on the wafer surface. [Figure 6] FIG. 6 is a graph showing the relationship between the rotation speed of the susceptor and the Fe concentration on the wafer surface. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention is not limited to the embodiment described below. In addition, in each drawing, the same or corresponding elements are appropriately assigned the same reference numerals. Furthermore, it should be noted that the drawings are schematic, and the dimensional relationship of each element, the ratio of each element, etc. may differ from the actual ones. There may also be parts in which the dimensional relationship and ratio differ between the drawings.

[0024] [Epitaxial growth equipment] Fig. 1 is a schematic diagram of an epitaxial growth apparatus according to an embodiment of the present invention. As shown in Fig. 1, the epitaxial growth apparatus 10 includes a chamber 20 in which a susceptor 1 for mounting a semiconductor substrate W is installed, and a controller 30 for controlling the flow rate of gas introduced into the chamber 20, the rotation speed of the susceptor 1, and the like.

[0025] The chamber 20 has an upper space S1 located above the susceptor 1 and through which an upper gas G1 flows, and a lower space S2 located below the susceptor 1 and through which a lower gas G2 flows. The upper gas G1 and the lower gas G2 flow from an upper gas inlet 3 and a lower gas inlet 4, respectively, toward an exhaust port 5, and are configured so as to be able to move between the upper space S1 and the lower space S2 via a communication part 2 located between the susceptor 1 and the exhaust port 5.

[0026] During deposition of an epitaxial layer on a semiconductor substrate W, the controller 30 controls so that an upper gas G1 containing a silane-based gas and a carrier gas is introduced into the upper space S1 from the upper gas inlet 3 at a first upper gas flow rate, and a lower gas G2 flowing into the lower space S2 is introduced from the lower gas inlet 4 at a first lower gas flow rate. At this time, the controller 30 controls the upper / lower flow rate ratio during deposition, which is the first lower gas flow rate / the first upper gas flow rate, to be (0.015 to 0.045)×X (where X=volume V2 of the lower space / volume V1 of the upper space).

[0027] During etching, in which a gas containing hydrogen chloride and a carrier gas is introduced into the upper space S1, the controller 30 controls the upper gas G1 to be introduced from the upper gas supply port 3 at a second upper gas flow rate into the upper space S1, and the lower gas G2 flowing into the lower space S2 to be introduced from the lower gas supply port 4 at a second lower gas flow rate. At this time, the gas flow rates of the upper gas G1 and the lower gas G2 are controlled so that the upper / lower flow rate ratio during etching, which is the second lower gas flow rate / the second upper gas flow rate, is larger than the upper / lower flow rate ratio during film formation and is 1 or less. Note that the upper / lower flow rate ratio during etching is preferably set to (0.075 to 0.125)×X (where X=volume V2 of the lower space / volume V1 of the upper space).

[0028] In such an epitaxial growth apparatus 10, the upper gas G1 is exhausted without flowing into the lower space S2 during etching, and part of the upper gas G1 flows into the lower space S2 through the communication part 2 during deposition of an epitaxial layer. That is, the upper gas G1 is controlled so as not to flow from the upper space S1 to the lower space S2 as much as possible during etching, and conversely, the upper gas G1 is controlled so as to flow from the upper space S1 to the lower space S2 as much as possible during deposition of a Si epitaxial layer. With such a configuration, while removing polysilicon deposited on the susceptor surface after deposition of the epitaxial layer, the arrival of HCl gas at the susceptor rear surface is suppressed and the susceptor rear surface is coated with Si, thereby suppressing deterioration of the susceptor rear surface and suppressing metal contamination caused by deterioration of the susceptor rear surface.

[0029] More specifically, for example, when the lower space volume V2 / upper space volume V1 is X=4, during upper HCl gas etching to remove the products and Si in the upper space, the lower gas flow rate is set to, for example, 0.3 to 0.5 (X=4) of the upper flow rate to suppress the inflow of HCl gas into the lower space, and during epitaxial growth, the lower gas flow rate is set to 0.06 to 0.18 (X=4) of the upper flow rate to allow Si-containing gas to flow into the lower space and protect the back side of the susceptor with a Si coating. During etching, the upper gas is controlled to not flow from the upper space to the lower space as much as possible, and conversely, during Si epitaxial growth, the gas is controlled to flow from the upper space to the lower space as much as possible. In addition, during deposition of an epitaxial layer on a semiconductor substrate, the air pressure in the upper space S1 can be made higher than the air pressure in the lower space S2, and during etching, the air pressure in the upper space S1 can be made lower than the air pressure in the lower space S2, thereby preventing the upper gas from escaping from the upper space to the lower space as much as possible during etching, and conversely, during Si epi deposition, controlling so that the upper gas escaping from the upper space to the lower space as much as possible.

[0030] [Method for manufacturing epitaxial wafer] Fig. 2 is a flow chart showing an outline of the procedure of an embodiment of a method for producing an epitaxial wafer. As shown in Fig. 2, the method for producing an epitaxial wafer includes a temperature increasing step in a chamber (step S1), an etching step in the chamber (step S2), a step of placing a semiconductor wafer on a susceptor (step S3), an epitaxial film forming step (step S4), a temperature decreasing step in the chamber (step S5), and a step of removing the semiconductor wafer (step S6). The method for producing an epitaxial wafer shown in Fig. 2 can be performed using the epitaxial growth apparatus described with reference to Fig. 1.

[0031] In the chamber temperature increasing step (step S1), the temperature in the chamber 20 of the epitaxial growth apparatus 10 is increased.

[0032] In the etching process (step S2) in the chamber, an upper gas G1 is introduced into the upper space S1 from an upper gas supply port 3 at a second upper gas flow rate, and a lower gas G2 flowing into the lower space S2 is introduced from a lower gas supply port 4 at a second lower gas flow rate. At this time, the gas flow rates of the upper gas G1 and the lower gas G2 are controlled so that the upper / lower flow rate ratio during etching, which is the second lower gas flow rate / the second upper gas flow rate, is greater than the upper / lower flow rate ratio during film formation and is equal to or less than 1. Note that the upper / lower flow rate ratio during etching is preferably set to (0.075 to 0.125)×X.

[0033] In the step of placing the semiconductor wafer on the susceptor (step S3), the semiconductor wafer is placed on the susceptor 1 installed in the chamber 20 of the epitaxial growth apparatus .

[0034] In the epitaxial film formation process (step S4), an upper gas G1 containing a silane-based gas and a carrier gas is introduced into the upper space S1 from an upper gas inlet 3 at a first upper gas flow rate, and a lower gas G2 flowing into the lower space S2 is introduced from a lower gas inlet 4 at a first lower gas flow rate. At this time, the upper / lower flow rate ratio during film formation, which is the first lower gas flow rate / the first upper gas flow rate, is set to (0.015 to 0.045)×X (where X=volume V2 of the lower space / volume V1 of the upper space).

[0035] In a chamber temperature lowering step (step S5), the temperature in the chamber 20 of the epitaxial growth apparatus 10 is lowered. Then, in a semiconductor wafer removal step (step S6), the semiconductor wafer is removed from the chamber 20 of the epitaxial growth apparatus 10 onto the susceptor 1. In the method for manufacturing epitaxial wafers, the above steps S1 to S6 are repeated for a desired number of wafers.

[0036] [Verification of effectiveness] Here, we present the results of verifying the effectiveness of the epitaxial growth apparatus and epitaxial wafer manufacturing method described above. In the verification shown below, the semiconductor wafer (substrate) used was a φ200mm silicon single crystal with a (001) crystal orientation grown by the Czochralski method, sliced, with an oxide film formed on the back side, polished, and RCA cleaned. The dopant was boron, the resistivity was 20mΩ·cm, and the oxygen concentration was 1.0E18atoms / cc.

[0037] This substrate was subjected to HCl and Si film formation processing based on the procedure shown in Figure 2. The thickness of the Si film was set to 5 μm. At this time, the flow rate of the lower gas G2 (H2) flowing into the lower space S2 was changed. In the chamber of the epitaxial growth device used in the verification experiment, the definition of the upstream and downstream balance, X = (V2 / V1), was "X = 4". It is preferable to design the range of X to be 0.05 to 1.2.

[0038] In this case, the flow rate ratios are as follows: When a mixed gas containing a silicon source gas is flowed into the upper space to form an epitaxial layer on a semiconductor substrate, The ratio Aa of the lower space inflow gas flow rate L2 to the upper space inflow gas flow rate L1 is L2 / L1 = (0.03±0.015)*4 (0.06~0.18). Specifically, the upper gas flow rate L1 is preferably in the range of 20~200 L / min, and the lower gas flow rate L2 is preferably in the range of 2~40 L / min. In addition, the partial pressure of the silicon source gas relative to the carrier gas is preferably in the range of 0.02~0.2. When a mixed gas containing a chlorine-based gas is flowed into the lower space to remove the film formed on the component, The ratio of the lower space inflow gas flow rate L2 to the upper space inflow gas flow rate L1 is Ab = L2 / L1 = (0.1±0.25)*4 (0.3~0.5). Specifically, the upper gas flow rate L1 is preferably in the range of 20~180 L / min, and the lower gas flow rate L2 is preferably in the range of 6~90 L / min. In addition, the partial pressure of the chlorine-based gas relative to the carrier gas is preferably in the range of 0.01~0.3.

[0039] Twenty-five wafers were continuously processed under each condition, and the following evaluation was performed on the 25th wafer. Fe concentration on wafer surface (ICP-MS) ·Si epitaxial layer thickness uniformity measured at nine points on the surface (FT-IR) The surface roughness of the wafer-holding susceptor used in the above test was changed by changing the CVD-SiC film formation temperature. The following evaluations were made in the same test. Fe concentration on wafer surface (ICP-MS) -Slip accumulation length (X-ray topography)

[0040] Figure 3 is a graph showing the relationship between the change in the flow rate of the lower gas H2 during HCl etching and the Fe concentration on the wafer surface. As shown in Figure 3, when the lower gas G2 is increased, the intrusion of HCl, which is the upper gas G1, into the lower space S2 is suppressed, and the Fe concentration on the epitaxial layer surface is reduced (i.e., contamination is reduced). However, if the lower gas G2 is increased too much, the transport of contamination from the lower space S2 to the upper space S1 increases. Therefore, when X=4, the gas flow rate ratio of the lower gas G2 to the upper gas G1 is appropriately set to 0.3 to 0.5.

[0041] FIG. 4 is a graph showing the relationship between the change in the flow rate of the lower gas H2 during epitaxial growth and the Fe concentration and film thickness uniformity on the wafer surface. In FIG. 4, the graph indicated by ▲ shows the relationship between the change in the flow rate of the lower gas H2 and the Fe concentration on the wafer surface, and the graph indicated by ● shows the relationship between the change in the flow rate of the lower gas H2 and the film thickness uniformity. As shown in FIG. 4, when the lower gas G2 is reduced, the effect of protecting the surface of the susceptor 1 is obtained by promoting the circulation of the Si source gas from the upper space S1 to the lower space S2, and contamination is reduced. In particular, when the gas flow rate ratio of the lower gas G1 to the upper gas G1 is less than 0.2, the effect of reducing contamination is large. However, when the partial pressure of the Si source gas in the lower space S2 increases too much, the reaction products in the reactor increase, deteriorating the temperature uniformity on the wafer surface and deteriorating the epitaxial film thickness uniformity. In particular, when the gas flow rate ratio of the lower gas G1 to the upper gas G1 is less than 0.05, the effect of deteriorating the epitaxial film thickness uniformity is large. Therefore, considering the effect of reducing contamination due to the reduction in the lower gas G2 and the impact of the reduction in the epitaxial film thickness uniformity due to the reduction in the lower gas G2, it is appropriate that the gas flow ratio of the lower gas G2 to the upper gas G1 during epitaxial growth is 0.05 to 0.2.

[0042] Figure 5 is a graph showing the relationship between the surface roughness of the susceptor and the Fe concentration and slip length on the wafer surface. In the graph of Figure 5, the graph indicated by ▲ shows the relationship between the surface roughness of the susceptor and the Fe concentration on the wafer surface, and the graph indicated by ● shows the relationship between the surface roughness of the susceptor and the slip length. As shown in Figure 5, when the surface roughness of the susceptor 1 increases (=increase in particle size), the contamination of the substrate C increases. In particular, when the surface roughness of the susceptor exceeds 17.5 μm, the effect of increased contamination is large. On the other hand, when this surface roughness decreases, the stability of the wafer placement position decreases (wafer slip), and slip occurs due to a decrease in the uniformity of the in-plane temperature. In particular, when the surface roughness of the susceptor falls below 7.5 μm, the effect of decreased wafer placement position stability is large. Therefore, considering the effect of increased contamination and the effect on the wafer placement position stability, the rms surface roughness of the susceptor 1 is appropriate to be 7.5-17.5 μm.

[0043] FIG. 6 is a graph showing the relationship between the rotation speed of the susceptor and the Fe concentration on the wafer surface. As shown in FIG. 6, the Fe concentration on the wafer surface also depends on the rotation speed of the susceptor 1. As shown in FIG. 6, if the rotation speed of the susceptor is slow during HCl etching, the upper gas G1 (HCl) enters the lower space S2, causing excessive etching of the back surface of the susceptor 1, which causes contamination. On the other hand, if the rotation speed of the susceptor is fast during epitaxial growth, the lower gas G2 rises to the upper space S1, contaminating the epitaxial layer. In particular, as shown in FIG. 6, by making the rotation speed of the susceptor during HCl etching faster than the rotation speed of the susceptor during epitaxial growth, it is possible to suppress the intrusion of the lower gas G1 (HCl) into the lower space S2 during HCl etching and the rise of the lower gas G2 to the upper space S1 during epitaxial growth. Therefore, the effect of suppressing metal contamination caused by deterioration of the back surface of the susceptor can be obtained simply by setting the rotation speed of the susceptor 1 to be less than the rotation speed during film formation. Specifically, it is appropriate to set the rotation speed of the susceptor to be R=(6±3)*X during film formation and R=(15±6)*X during etching. For example, when X=4, the rotation speed during film formation is preferably within the range of 12 to 36 rpm, and the rotation speed during etching is preferably within the range of 36 to 84 rpm. Note that the change in the susceptor rotation speed during film formation and during etching may be combined with the change in the upper / lower gas flow rate ratio described above. [Explanation of symbols]

[0044] 10 Epitaxial growth equipment 20 Chamber 30 Controller 1. Susceptor 2 Communication section 3 Upper gas inlet 4 Lower gas inlet 5. Exhaust port

Claims

1. a susceptor on which a semiconductor substrate is placed; a chamber having the susceptor installed therein, the chamber having an upper space located above the susceptor and through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part through which a lower gas flows, the upper gas and the lower gas flowing from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port; a controller for controlling a gas flow rate of the upper gas and the lower gas, During deposition of an epitaxial layer on a semiconductor substrate, an upper gas containing a silane-based gas and a carrier gas is introduced into the upper space from the upper gas inlet at a first upper gas flow rate, a lower gas flowing into the lower space is introduced from the lower gas inlet at a first lower gas flow rate, and an upper / lower flow rate ratio during deposition, which is the first lower gas flow rate / the first upper gas flow rate, is set to (0.015 to 0.045)×X (where X=volume V2 of the lower space / volume V1 of the upper space); a gas supply port for supplying an upper gas to the upper space at a second upper gas flow rate and a lower gas flowing into the lower space at a second lower gas flow rate, and a gas supply port for supplying an upper gas to the upper space at a second lower gas flow rate, and a gas supply port for supplying an upper gas to the lower space at a second lower gas flow rate, and an upper / lower flow rate ratio during etching, which is the second lower gas flow rate / the second upper gas flow rate, is set to be greater than the upper / lower flow rate ratio during film formation and to be 1 or less.

2. 2. The method for producing an epitaxial wafer according to claim 1, wherein the upper / lower flow rate ratio during etching is set to (0.075 to 0.125)×X.

3. During etching, the upper gas is exhausted without flowing into the lower space, 2. The method for producing an epitaxial wafer according to claim 1, wherein a part of the upper gas flows into the lower space through the communication portion during deposition of an epitaxial layer.

4. During deposition of an epitaxial layer on a semiconductor substrate, the air pressure in the upper space is made higher than the air pressure in the lower space; 2. The method for producing an epitaxial wafer according to claim 1, wherein the air pressure in the upper space is set lower than the air pressure in the lower space during etching.

5. 2. The method for producing an epitaxial wafer according to claim 1, wherein the surface roughness of the back surface of the susceptor is set to 7.5 to 17.5 μm.

6. a susceptor on which a semiconductor substrate is placed; a chamber having the susceptor installed therein, the chamber having an upper space located above the susceptor and through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part through which a lower gas flows, the upper gas and the lower gas flowing from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port; A method for manufacturing an epitaxial wafer, comprising vapor-phase growing an epitaxial layer on a semiconductor substrate using an epitaxial growth apparatus having a controller for controlling a heating speed of the susceptor, A method for producing an epitaxial wafer, characterized in that the rotation speed of the susceptor during film formation is less than the rotation speed during etching.

7. 7. The method for producing an epitaxial wafer according to claim 6, wherein the rotation speed of the susceptor during film formation is R=(6±3)×X, and the rotation speed during etching is R=(15±6)×X.

8. a susceptor on which a semiconductor substrate is placed; a chamber having the susceptor installed therein, the chamber having an upper space located above the susceptor and through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part through which a lower gas flows, the upper gas and the lower gas flowing from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port; During deposition of an epitaxial layer on a semiconductor substrate, an upper gas containing a silane-based gas and a carrier gas is introduced into the upper space from the upper gas inlet at a first upper gas flow rate, a lower gas flowing into the lower space is introduced from the lower gas inlet at a first lower gas flow rate, an upper / lower flow rate ratio during deposition, which is the first lower gas flow rate / the first upper gas flow rate, is set to (0.015 to 0.045)×X (where X=volume V2 of the lower space / volume V1 of the upper space), and a gas containing hydrogen chloride and a carrier gas is introduced into the upper space. and a controller for controlling the gas flow rates of the upper gas and the lower gas during etching, wherein an upper gas is introduced from the upper gas supply port at a second upper gas flow rate and a lower gas flowing into the lower space is introduced from the lower gas supply port at a second lower gas flow rate, and wherein an upper / lower flow rate ratio during etching, which is the second lower gas flow rate / second upper gas flow rate, is greater than the upper / lower flow rate ratio during film formation and is equal to or less than 1.

9. 9. The epitaxial growth apparatus according to claim 8, wherein the upper-lower flow rate ratio during etching is set to (0.075 to 0.125)×X.

10. a susceptor on which a semiconductor substrate is placed; a chamber having the susceptor installed therein, the chamber having an upper space located above the susceptor and through which an upper gas flows, and a lower space located below the susceptor and communicating with the upper space via a communication part through which a lower gas flows, the upper gas and the lower gas flowing from an upper gas inlet and a lower gas inlet toward an exhaust port, the communication part being located between the susceptor and the exhaust port; and a controller that controls the rotation speed of the susceptor so that the rotation speed during film formation is smaller than the rotation speed during etching.

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