Vapor phase growth apparatus and vapor phase growth method

Abstract

A gas phase growth apparatus according to an embodiment includes a reaction chamber, a substrate holding portion provided in the reaction chamber, capable of placing a substrate, having a holding wall capable of holding an outer periphery of the substrate with a prescribed gap, a process gas supply portion provided above the reaction chamber, having a first region that supplies a first process gas to the reaction chamber and a second region provided around the first region, capable of supplying a second process gas having a higher carbon / silicon atomic ratio than the first process gas to the reaction chamber, an inner periphery diameter of the second region being 75% or more and 130% or less of a diameter of the holding wall, a side wall provided in a region between the process gas supply portion and the substrate holding portion in the reaction chamber, an inner periphery diameter being 110% or more and 200% or less of an outer periphery diameter of the second region, a first heater provided below the substrate holding portion, a second heater provided between the side wall and an inner wall of the reaction chamber, and a rotation driving mechanism that rotates the substrate holding portion.

Description

Technical Field

[0001] This invention relates to a vapor phase growth apparatus and a vapor phase growth method for supplying gas to form a film. Background Technology

[0002] As a method for forming high-quality semiconductor films, epitaxial growth technology is used to grow single-crystal films on substrates such as wafers through vapor phase growth. In a vapor phase growth apparatus using epitaxial growth technology, a wafer is placed in a substrate holding section within a reaction chamber that is maintained at atmospheric pressure or reduced pressure.

[0003] Furthermore, while heating the wafer, process gases, such as source gases that will become the raw materials for film formation, are supplied from the top of the reaction chamber to the wafer surface inside the reaction chamber. Thermal reactions of the source gases occur on the wafer surface, resulting in the formation of an epitaxial single crystal film on the wafer surface.

[0004] There are cases where impurities are introduced as dopants into epitaxial single-crystal films. To ensure a uniform resistance distribution in the epitaxial single-crystal film, the concentration distribution of the impurities needs to be uniform.

[0005] Patent Document 1 describes a method in which, during the formation of an epitaxial single crystal film of silicon carbide (SiC), process gases with different C (carbon) / Si (silicon) ratios are supplied to the center and the outer periphery of the substrate in order to make the concentration distribution of impurities uniform.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent No. 5265985 Summary of the Invention

[0009] Problems solved by the invention

[0010] The problem solved by the present invention is to provide a vapor phase growth apparatus and a vapor phase growth method that can improve the uniformity of the concentration distribution of impurities in a membrane.

[0011] Methods for solving problems

[0012] One embodiment of the vapor phase growth apparatus of the present invention includes: a reaction chamber; a substrate holding portion disposed in the reaction chamber, capable of holding a substrate and having a holding wall capable of holding the outer periphery of the substrate with a predetermined gap; a process gas supply portion disposed above the reaction chamber, having a first region and a second region, the first region capable of supplying a first process gas to the reaction chamber, and the second region disposed around the first region capable of supplying a second process gas to the reaction chamber, the second process gas having a higher carbon / silicon atomic ratio than the first process gas, and the inner circumferential diameter of the second region being 75% to 130% of the diameter of the holding wall; a side wall disposed in the reaction chamber between the process gas supply portion and the substrate holding portion, the inner circumferential diameter of which is 110% to 200% of the outer circumferential diameter of the second region; a first heater disposed below the substrate holding portion; a second heater disposed between the side wall and the inner wall of the reaction chamber; and a rotation drive mechanism for rotating the substrate holding portion.

[0013] In the vapor phase growth apparatus of the above configuration, it is preferable that the inner circumferential diameter of the second region is 100% or more of the diameter of the retaining wall.

[0014] In the vapor phase growth apparatus of the above configuration, it is preferable that the inner circumferential diameter of the sidewall is 105% to 200% of the diameter of the substrate holding portion.

[0015] In the vapor phase growth apparatus described above, it is preferable that the rotary drive mechanism rotates the substrate at a rotational speed of 300 rpm to 3000 rpm.

[0016] In the above-described vapor phase growth apparatus, it is preferable that the process gas supply section has a third region disposed around the second region, which is capable of supplying a third process gas to the region between the sidewall and the second heater, and the sidewall has a gas passage hole that allows the third process gas to pass from the outside of the sidewall to the inside of the sidewall.

[0017] In the gas phase growth apparatus described above, it is preferable that the gas used in the third process is argon.

[0018] In one aspect of the vapor phase growth method of the present invention, a substrate is rotated at a rotational speed of 300 rpm or more, the substrate is heated, a first process gas is supplied toward the substrate at a first flow rate, and a second process gas is supplied toward the substrate at a second flow rate for a region further outward than the first process gas. The second process gas has a higher carbon / silicon atomic ratio than the first process gas. The first flow rate, the second flow rate, and the rotational speed are controlled to form a flow that introduces the second process gas toward the center of the substrate, thereby forming a silicon carbide film on the surface of the substrate.

[0019] In another aspect of the vapor phase growth method of the present invention, a substrate is rotated at a speed of 300 rpm or higher, the substrate is heated, a first process gas comprising carbon, silicon, and n-type impurities is supplied toward the substrate, and a second process gas comprising carbon, silicon, and n-type impurities is supplied toward the substrate to a region further outward than the region to which the first process gas is supplied. This second process gas has a higher carbon / silicon atomic ratio than the first process gas. When the effective carbon / silicon atomic ratio of the process gas directly above the surface of the substrate is less than 1, the substrate... A first silicon carbide film is formed on the surface of the substrate. A third process gas containing carbon, silicon, and n-type impurities is supplied to the substrate. A fourth process gas containing carbon, silicon, and n-type impurities is supplied to the substrate for a region further outward than the region where the third process gas is supplied. The fourth process gas has a higher carbon / silicon atomic ratio than the third process gas. When the effective carbon / silicon atomic ratio of the process gas directly above the surface of the substrate is 1 or higher, a second silicon carbide film with a lower n-type impurity concentration than the first silicon carbide film is formed on the surface of the substrate.

[0020] The effects of the invention

[0021] According to the present invention, a vapor phase growth apparatus and a vapor phase growth method are provided that can improve the uniformity of the concentration distribution of impurities in a membrane. Attached Figure Description

[0022] Figure 1 This is a schematic cross-sectional view of the vapor phase growth apparatus of the first embodiment.

[0023] Figure 2 This is a schematic cross-sectional view showing another specific example of the process gas supply unit in the first embodiment.

[0024] Figure 3 This is an explanatory diagram showing the dimensions of the components of the vapor phase growth apparatus according to the first embodiment.

[0025] Figure 4 This is an explanatory diagram of the flow of process gas in the reaction chamber of the vapor phase growth method of the first embodiment.

[0026] Figure 5 This diagram illustrates the problems encountered during the formation of the SiC film.

[0027] Figure 6 This is a graph showing the relationship between the parameters of the vapor phase growth method of the first embodiment and the distribution of impurity concentration in the wafer surface.

[0028] Figure 7 This is an explanatory diagram of the flow of process gas in the reaction chamber of the vapor phase growth method of the first embodiment.

[0029] Figure 8 This is a schematic cross-sectional view of the vapor phase growth apparatus of the second embodiment.

[0030] Figure 9 This is an explanatory diagram of the flow of process gas in the reaction chamber of the vapor phase growth method of the second embodiment.

[0031] Figure 10 This is a cross-sectional view of a silicon carbide film formed using the vapor phase growth method of the third embodiment.

[0032] Figure 11 This is an explanatory diagram of the vapor phase growth method according to the third embodiment.

[0033] Figure 12 This is an explanatory diagram illustrating the function and effect of the vapor phase growth method in the third embodiment.

[0034] Figure 13 This is an explanatory diagram illustrating the function and effect of the vapor phase growth method in the third embodiment.

[0035] Figure 14 This is an explanatory diagram illustrating the function and effect of the vapor phase growth method in the third embodiment. Detailed Implementation

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0037] In this manual, the same or similar parts are sometimes referred to by the same symbol.

[0038] In this specification, the direction of gravity when the vapor phase growth apparatus is set up to form a film is defined as "down," and its opposite direction is defined as "up." Therefore, "lower" means the position relative to a reference point in the direction of gravity, and "below" means the direction of gravity relative to a reference point. Furthermore, "upper" means the position relative to a reference point in the direction opposite to gravity, and "above" means the position relative to a reference point in the direction opposite to gravity. Additionally, "longitudinal" refers to the direction of gravity.

[0039] In addition, in this specification, the term "process gas" is a general term for gases used to form a film on a substrate, for example, including source gas, auxiliary gas, dopant gas, carrier gas, and mixtures thereof.

[0040] (First Embodiment)

[0041] The vapor phase growth apparatus of the first embodiment includes: a reaction chamber; a substrate holding section disposed in the reaction chamber, capable of holding a substrate, and having a holding wall capable of holding the outer periphery of the substrate with a predetermined gap; a process gas supply section disposed above the reaction chamber, having a first region and a second region, the first region supplying a first process gas to the reaction chamber, and the second region disposed around the first region capable of supplying a second process gas to the reaction chamber, the second process gas having a higher carbon / silicon atomic ratio than the first process gas, and the inner circumferential diameter of the second region being 75% to 130% of the diameter of the holding wall; a side wall disposed in the reaction chamber between the process gas supply section and the substrate holding section, the inner circumferential diameter being 110% to 200% of the outer circumferential diameter of the second region; a first heater disposed below the substrate holding section; and a second heater disposed between the side wall and the inner wall of the reaction chamber; and a rotation drive mechanism for rotating the substrate holding section.

[0042] In addition, in the vapor phase growth method of the first embodiment, the substrate is rotated at a rotational speed of 300 rpm or more, the substrate is heated, a first process gas is supplied toward the substrate at a first flow rate, and a second process gas is supplied toward the substrate at a second flow rate for a region further outward than the first process gas. The second process gas has a higher carbon / silicon atomic ratio than the first process gas. The first flow rate, the second flow rate, and the rotational speed are controlled to form a flow in which the second process gas is introduced toward the center of the substrate, thereby forming a silicon carbide film on the surface of the substrate.

[0043] Figure 1 This is a schematic cross-sectional view of the vapor phase growth apparatus of the first embodiment. The vapor phase growth apparatus 100 of the first embodiment is, for example, a monolithic epitaxial growth apparatus for epitaxially growing a single-crystal SiC film on a single-crystal SiC substrate.

[0044] The vapor phase growth apparatus 100 of the first embodiment includes a reaction chamber 10 and a process gas supply unit 12. The reaction chamber 10 includes a base 14 (substrate holding part), a rotating body 16, a rotating shaft 18, a rotating drive mechanism 20, a first heater 22, a reflector 28, a support column 30, a fixed stage 32, a fixed shaft 34, a baffle 40 (side wall), a second heater 42, and a gas outlet 44. The process gas supply unit 12 includes a first gas supply port 52, a second gas supply port 54, a first gas ejection hole 56, and a second gas ejection hole 58. The circular region of the process gas supply unit 12 with the first gas ejection hole 56 is the first region 12a, and the annular region with the second gas ejection hole 58 is the second region 12b.

[0045] The following explanation will take the case of epitaxially growing a single-crystal SiC film on a single-crystal SiC wafer using a vapor phase growth apparatus 100 as an example.

[0046] The process gas supply unit 12 is located above the reaction chamber 10. The process gas supply unit 12 has the function of supplying process gas to the reaction chamber 10.

[0047] The first gas supply port 52 and the second gas supply port 54 are provided on the upper part of the process gas supply section 12. The first gas supply port 52 supplies, for example, a first process gas G1 into the process gas supply section 12. The second gas supply port 54 supplies, for example, a second process gas G2 into the process gas supply section 12.

[0048] The first gas ejector hole 56 and the second gas ejector hole 58 are located at the lower part of the process gas supply unit 12. The first gas ejector hole 56 and the second gas ejector hole 58 are arranged facing the reaction chamber 10.

[0049] The second gas ejection port 58 is disposed around the first gas ejection port 56. The area of ​​the process gas supply unit 12 where the first gas ejection port 56 is disposed is the first region 12a, and the area where the second gas ejection port 58 is disposed is the second region 12b. Therefore, the second region 12b is disposed around the first region 12a.

[0050] A first process gas G1 is supplied to the reaction chamber 10 from a first gas ejector port 56. A second process gas G2 is supplied to the reaction chamber 10 from a second gas ejector port 58. In other words, the first process gas G1 is supplied to the reaction chamber 10 from a first region 12a, and the second process gas G2 is supplied to the reaction chamber 10 from a second region 12b.

[0051] The process gas supply unit 12 includes a first region 12a and a second region 12b, thereby enabling the supply of process gases of different compositions to the center and outer periphery of the wafer W at different flow rates. Furthermore, in this specification, the flow rate is determined by dividing the gas flow rate introduced from the gas supply port or the gas flow rate through the gas ejection port by the cross-sectional area of ​​the corresponding gas ejection port.

[0052] The first process gas G1 is, for example, a mixture of a source gas containing silicon (Si), a source gas containing carbon (C), a dopant gas containing n-type impurities, an auxiliary gas to inhibit silicon clustering, and a carrier gas. The source gas for silicon is, for example, silane (SiH4). The source gas for carbon is, for example, propane (C3H8). The dopant gas for n-type impurities is, for example, nitrogen. The auxiliary gas is, for example, hydrogen chloride (HCl). The carrier gas is, for example, argon or hydrogen.

[0053] The second process gas G2 is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, an auxiliary gas, and a carrier gas. The silicon source gas is, for example, silane. The carbon source gas is, for example, propane. The n-type impurity dopant gas is, for example, nitrogen. The auxiliary gas is, for example, hydrogen chloride (HCl). The carrier gas is, for example, argon or hydrogen.

[0054] The carbon / silicon atomic ratio (hereinafter also referred to as C / Si ratio) of the second process gas G2 is higher than that of the first process gas G1. For example, by making the proportion of silicon source gas in the second process gas G2 relative to carbon source gas lower than that in the first process gas G1, the C / Si ratio of the second process gas G2 can be made higher than that of the first process gas G1. Alternatively, for example, by making the second process gas G2 contain no silicon source gas and only use the source gas as the carbon source gas, the C / Si ratio of the second process gas G2 can be made higher than that of the first process gas G1.

[0055] Furthermore, this explanation will take the method of mixing all the process gases before supplying process gases to the process gas supply unit 12 to form the first process gas G1 and the second process gas G2 as an example. However, the process gases may be mixed in the process gas supply unit 12 or after being supplied to the reaction chamber 10.

[0056] For example, before supplying the reaction chamber 10, all or part of the silicon source gas, carbon source gas, and dopant gas and auxiliary gas of n-type impurities can be separated.

[0057] For example, multiple gas ejection holes can be provided as the first gas ejection hole 56, so that different types of process gases can be supplied from each gas ejection hole. The same applies to the second gas ejection hole 58.

[0058] Figure 2 This is a schematic cross-sectional view showing another specific example of the process gas supply unit in the first embodiment. The process gas supply unit 72 includes a silicon source gas supply port 82, a carbon source gas supply port 84, a first separation chamber 83, a second separation chamber 85, a silicon source gas ejection port 86, and a carbon source gas ejection port 88. When the process gas supply unit 72 is used, the silicon source gas and the carbon source gas are mixed after being supplied to the reaction chamber 10.

[0059] In this configuration, the C / Si ratio introduced into the reaction chamber 10 can be varied by adjusting the flow rates of the gas supplied to the carbon source gas ejection port 88 and the silicon source gas ejection port 86. Furthermore, by changing the density (number of gas ejection ports per unit area) of the carbon source gas ejection port 88 and the silicon source gas ejection port 86 in the first region 12a and the second region 12b, the C / Si ratio in the first region 12a and the second region 12b can be changed (making the C / Si ratio in the second region 12b higher than that in the first region 12a). Additionally, for example, the C / Si ratio in the first region 12a and the second region 12b can be varied by adjusting the cross-sectional area of ​​the carbon source gas ejection port 88 and the silicon source gas ejection port 86 in the first region 12a and the second region 12b (making the C / Si ratio in the second region 12b higher than that in the first region 12a).

[0060] The reaction chamber 10 is made of stainless steel, for example. The reaction chamber 10 has a cylindrical inner wall 10a. Inside the reaction chamber 10, a SiC film is formed on the wafer W.

[0061] The base 14 is disposed inside the reaction chamber 10. A wafer W, which serves as a substrate, can be placed on the base 14. An opening may also be provided at the center of the base 14.

[0062] The base 14 has a retaining wall 14a capable of holding the outer periphery of the wafer W with a predetermined gap. The horizontal movement of the wafer W is suppressed by the retaining wall 14a. The difference between the diameter of the retaining wall 14a and the diameter of the wafer W is, for example, 3 mm or less.

[0063] The base 14 is formed of a heat-resistant material such as SiC, carbon, or carbon coated with SiC or TaC.

[0064] The base 14 is fixed to the upper part of the rotating body 16. The rotating body 16 is fixed to the rotating shaft 18. The base 14 is indirectly fixed to the rotating shaft 18.

[0065] The rotating shaft 18 can be rotated by the rotating drive mechanism 20. By rotating the rotating shaft 18 by the rotating drive mechanism 20, the base 14 can be rotated. By rotating the base 14, the wafer W placed on the base 14 can be rotated.

[0066] For example, the wafer W is rotated at a speed between 300 rpm and 3000 rpm. The rotation drive mechanism 20 is, for example, composed of a motor and bearings.

[0067] The first heater 22 is disposed below the base 14. The first heater 22 is disposed inside the rotating body 16. The first heater 22 heats the wafer W held on the base 14 from below. The first heater 22 is, for example, a resistance heater. The first heater 22 is, for example, a circular plate with a comb-shaped pattern.

[0068] The reflector 28 is positioned below the first heater 22. The first heater 22 is positioned between the reflector 28 and the base 14.

[0069] The reflector 28 reflects heat emitted from the first heater 22 downwards, improving the heating efficiency of the wafer W. Additionally, the reflector 28 prevents components located below it from being heated. The reflector 28 is, for example, in the shape of a circular plate. The reflector 28 is formed, for example, from a material with high heat resistance, such as carbon coated with SiC.

[0070] The reflector 28 is fixed to the mounting platform 32, for example, by a plurality of support columns 30. The mounting platform 32 is supported, for example, by a fixed shaft 34.

[0071] Within the rotating body 16, a lifting pin (not shown) is provided to allow the base 14 to be detached from the rotating body 16. The lifting pin, for example, passes through the reflector 28 and the first heater 22.

[0072] The second heater 42 is disposed between the baffle 40 and the inner wall 10a of the reaction chamber 10. The second heater 42 heats the wafer W held on the base 14 from above. In addition to the first heater 22, the second heater 42 heats the wafer W, thereby enabling the wafer W to be heated to the temperature necessary for SiC film growth, such as above 1500°C. The second heater 42 is, for example, a resistance heater.

[0073] A baffle 40 is disposed in the area between the process gas supply section 12 and the base 14 within the reaction chamber 10. The baffle 40 is, for example, cylindrical. The baffle 40 has the function of preventing the first process gas G1 and the second process gas G2 from contacting the second heater 42. The baffle 40 is formed, for example, from a material with high heat resistance such as carbon covered with SiC.

[0074] Gas outlet 44 is located at the bottom of reaction chamber 10. Gas outlet 44 discharges the remaining reaction products and remaining process gases after the source gas reacts at the surface of wafer W to the outside of reaction chamber 10. Gas outlet 44 is connected, for example, to a vacuum pump (not shown).

[0075] Additionally, a wafer inlet / outlet and a gate valve (not shown) are provided in the reaction chamber 10. The wafer W can be moved into or out of the reaction chamber 10 via the wafer inlet / outlet and the gate valve.

[0076] Figure 3 This is an explanatory diagram showing the dimensions of the components of the vapor phase growth apparatus according to the first embodiment. Figure 3 The diagram shows a portion of the process gas supply section 12, a baffle 40, a base 14, and a wafer W mounted on the base 14.

[0077] Figure 3 The top image is a sectional view, and the bottom image is a top view. In the top view, section lines are drawn for regions 12a and 12b. In the top view, dotted lines represent the wafer W after omitting the orientation plane and notch.

[0078] The inner diameter of the second region 12b is defined as d1. The inner diameter of the second region 12b is defined by the diameter of the circle inscribed in the innermost nozzle of the second gas ejection orifice 58. The outer diameter of the second region 12b is defined as d2. The outer diameter of the second region 12b is defined by the diameter of the circle circumscribed in the outermost nozzle of the second gas ejection orifice 58.

[0079] The diameter of the retaining wall 14a of the base 14 is set to d3. The diameter of the base 14 is set to d4. In addition, the inner circumferential diameter of the baffle 40 is set to d5.

[0080] The inner circumferential diameter d1 of the second region 12b is more than 75% and less than 130% of the diameter d3 of the retaining wall 14a. The outer circumferential diameter d2 of the second region 12b is, for example, larger than the diameter d3 of the retaining wall 14a.

[0081] The inner circumferential diameter d5 of the baffle 40 is 110% to 200% of the outer circumferential diameter d2 of the second region 12b. Furthermore, the inner circumferential diameter d5 of the baffle 40 is preferably 105% to 200% of the diameter d4 of the base 14.

[0082] Next, the vapor phase growth method of the first embodiment will be described. The vapor phase growth method of the first embodiment uses... Figure 1 The epitaxial growth apparatus shown is illustrated. An example will be given of a single-crystal SiC film formed on the surface of a single-crystal SiC wafer, in which nitrogen is doped as an n-type impurity.

[0083] First, the substrate 14, on which the wafer W is placed, is moved into the reaction chamber 10. The wafer W is single-crystal SiC.

[0084] Next, the wafer W is rotated at a speed of 300 rpm or higher by the rotary drive mechanism 20. Then, the wafer W is heated by the first heater 22 and the second heater 42.

[0085] Next, a first process gas G1 is supplied from the first region 12a of the process gas supply section 12 at a first flow rate toward the center of the surface of the wafer W. The first process gas G1 ejected from the first gas ejection port 56 becomes a laminar flow from the process gas supply section 12 toward the surface of the wafer W.

[0086] Additionally, a second process gas G2 is supplied from the second region 12b of the process gas supply section 12 at a second flow rate to a region further outward than the center of the wafer W. The second process gas G2 is supplied to the region outside the wafer W compared to the first process gas G1. The second process gas G2 ejected from the second gas ejection port 58 becomes a laminar flow from the process gas supply section 12 toward the surface of the wafer W.

[0087] The first and second flow velocities are, for example, above 0.2 m / sec and below 1.0 m / sec.

[0088] The first process gas G1 is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, an auxiliary gas, and a carrier gas. The silicon source gas is, for example, silane (SiH4). The carbon source gas is, for example, propane (C3H8). The n-type impurity dopant gas is, for example, nitrogen. The auxiliary gas is, for example, hydrogen chloride (HCl). The carrier gas is, for example, argon or hydrogen.

[0089] The second process gas G2 is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, and a carrier gas. The silicon source gas is, for example, silane. The carbon source gas is, for example, propane. The n-type impurity dopant gas is, for example, nitrogen. The carrier gas is, for example, argon or hydrogen.

[0090] The C / Si ratio of the second process gas G2 supplied from the process gas supply unit 12 to the reaction chamber 10 is higher than that of the first process gas G1.

[0091] By supplying a first process gas G1 and a second process gas G2 to the surface of a wafer W, a single-crystal SiC film doped with nitrogen as an n-type impurity is formed on the surface of the wafer W. During the formation of the single-crystal SiC film, a first flow rate of the first process gas G1, a second flow rate of the second process gas G2, and the rotational speed of the wafer W are controlled in such a manner that the flow of the second process gas G2 is introduced towards the center of the wafer W.

[0092] The first flow rate can be controlled, for example, by changing the flow rate of the process gas supplied to the first gas ejector 56 using a mass flow controller (not shown). Similarly, the second flow rate can be controlled, for example, by changing the flow rate of the process gas supplied to the second gas ejector 58 using a mass flow controller (not shown). Furthermore, the rotational speed of the wafer W can be controlled by the rotation drive mechanism 20.

[0093] Figure 4 This is an explanatory diagram of the flow of process gases within the reaction chamber of the vapor phase growth method according to the first embodiment. During the deposition of a single-crystal SiC film, the first process gas G1, ejected vertically as a laminar flow from the first region 12a, flows horizontally towards the outer side of the wafer W on the surface of the wafer W. The second process gas G2, ejected vertically as a laminar flow from the second region 12b, flows horizontally towards the outer side of the wafer W after being introduced towards the center of the wafer W. In other words, the flow direction of the second process gas G2 has a component that flows towards the center of the wafer W before reaching the surface of the wafer W.

[0094] After the single-crystal SiC film is formed, the heating performed by the first heater 22 and the second heater 42 is stopped, causing the temperature of the wafer W to drop. Then, the wafer W and the substrate 14 are removed from the reaction chamber 10.

[0095] Next, the function and effects of the vapor phase growth apparatus and vapor phase growth method of the first embodiment will be explained.

[0096] Figure 5 This diagram illustrates the problems encountered during the formation of the SiC film. Figure 5 The in-plane distribution of impurity concentration is shown when a SiC film doped with nitrogen as an n-type impurity is formed on a wafer.

[0097] like Figure 5 As shown, the nitrogen concentration in the SiC film increases at the outer periphery of wafer W. Therefore, the concentration distribution of n-type impurities in the SiC film becomes non-uniform, and the in-plane resistance distribution of wafer W becomes non-uniform.

[0098] One reason for the higher nitrogen concentration at the outer periphery of wafer W is that silicon, formed from the sublimation of silicon-containing deposits attached to the surface of the substrate 14 on the outer side of wafer W, is mixed into the process gas at the outer periphery of wafer W. The sublimated silicon mixes into the process gas at the outer periphery of wafer W, thereby lowering the C / Si ratio in the process gas supplied to the outer periphery of wafer W. Nitrogen enters the carbon lattice sites in the SiC crystal and is thus incorporated into the crystal. Therefore, the lower C / Si ratio in the process gas results in less carbon, and nitrogen more easily enters the carbon lattice sites in the SiC crystal. Consequently, the nitrogen concentration at the outer periphery is higher than at the center of wafer W.

[0099] In the vapor phase growth apparatus and method of the first embodiment, firstly, a second process gas G2 with a high C / Si ratio is supplied to the outer periphery of the wafer W. Furthermore, by controlling the first flow rate of the first process gas G1 supplied to the center of the wafer W, the second flow rate of the second process gas G2 supplied to the outer periphery of the wafer W, and the rotational speed of the wafer W, the uniformity of the concentration distribution of n-type impurities in the SiC film is improved.

[0100] Figure 6 This is a graph showing the relationship between the parameters of the vapor phase growth method of the first embodiment and the distribution of impurity concentration in the wafer surface. Figure 6 (a) is the case where the parameter is the C / Si ratio of the gas G2 in the second process. Figure 6 (b) is the case where the parameter is the rotational speed of the wafer W. Figure 6 (c) represents the case where the parameter is the second flow rate of the second process gas G2.

[0101] like Figure 6 As shown in (a), if the C / Si ratio of the second process gas G2 is increased, the nitrogen concentration at the outer periphery of wafer W decreases; conversely, if the C / Si ratio is decreased, the nitrogen concentration at the outer periphery of wafer W increases. This is believed to be because increasing the C / Si ratio of G2 results in a higher C / Si ratio at the outer periphery of wafer W, making it less likely for nitrogen to enter the SiC crystal. Conversely, decreasing the C / Si ratio of G2 results in a lower C / Si ratio at the outer periphery of wafer W, making it easier for nitrogen to enter the SiC crystal.

[0102] In addition, such as Figure 6As shown in (b), increasing the rotational speed of wafer W results in a lower nitrogen concentration at the outer periphery of wafer W, while decreasing the rotational speed results in a higher nitrogen concentration at the outer periphery. This is believed to be because increasing the rotational speed of wafer W increases the amount of the second process gas G2 introduced towards the center of wafer W. It is thought that the increased introduction of the second process gas G2 with a high C / Si ratio leads to a higher C / Si ratio at the outer periphery of wafer W, making it less likely for nitrogen to enter the SiC crystal. Conversely, decreasing the rotational speed of wafer W reduces the introduction of the second process gas G2 with a high C / Si ratio, resulting in a lower C / Si ratio at the outer periphery of wafer W, thus making it easier for nitrogen to enter the SiC crystal.

[0103] In addition, such as Figure 6 As shown in (c), if the second flow rate of the second process gas G2 is increased, the nitrogen concentration at the outer periphery of the wafer W increases; conversely, if the second flow rate of the second process gas G2 is decreased, the nitrogen concentration at the outer periphery of the wafer W decreases. This is believed to be because increasing the second flow rate of the second process gas G2 reduces the amount of gas introduced towards the center of the wafer W, making it easier for nitrogen to enter the SiC crystal at the outer periphery of the wafer W. Conversely, decreasing the second flow rate of the second process gas G2 increases the amount of gas introduced towards the center of the wafer W, making it difficult for nitrogen to enter the SiC crystal at the outer periphery of the wafer W.

[0104] In the vapor phase growth apparatus 100 and vapor phase growth method of the first embodiment, a second process gas G2 with a higher carbon / silicon atomic ratio than the first process gas G1 is supplied to the outer region. Furthermore, by controlling the first flow rate of the first process gas G1, the second flow rate of the second process gas G2 supplied to the outer periphery of the wafer W, and the rotational speed of the wafer W, a flow of the second process gas G2 is formed, introducing it towards the center of the wafer W, thereby forming a SiC film. This improves the uniformity of the concentration distribution of n-type impurities in the SiC film.

[0105] In particular, by applying an adjustment to the concentration distribution based on changes in the second flow rate of the second process gas G2 and the rotational speed of the wafer W, the uniformity of the impurity concentration distribution can be improved with higher precision compared to an adjustment based solely on the C / Si ratio of the second process gas G2.

[0106] From the viewpoint of achieving a highly uniform impurity concentration distribution by ensuring the flow of the second process gas G2 towards the center of the wafer W, the inner circumferential diameter d1 of the second region 12b of the vapor phase growth apparatus 100 needs to be 75% to 130% of the diameter d3 of the holding wall 14a. If it is below this range, the impurity concentration at the center of the wafer W will be low, and the impurity concentration distribution may become uneven. Conversely, if it is above this range, the amount of the second process gas G2 introduced will be insufficient, and the impurity concentration distribution may also become uneven.

[0107] From the viewpoint of suppressing the reduction of impurity concentration in the center of wafer W, it is preferable that the inner circumferential diameter d1 of the second region 12b is 100% or more of the diameter d3 of the holding wall 14a. On the other hand, from the viewpoint of suppressing the insufficient introduction of the second process gas G2, it is preferable that the inner circumferential diameter d1 of the second region 12b is less than 100% of the diameter d3 of the holding wall 14a.

[0108] In the vapor phase growth apparatus 100 of the first embodiment, from the viewpoint of achieving a highly uniform impurity concentration distribution by realizing the flow of the second process gas G2 toward the center direction of the wafer W, the inner circumferential diameter d5 of the baffle 40 needs to be 110% to 200% of the outer circumferential diameter d2 of the second region 12b, preferably 110% to 150%. If it is below the above range, the laminar flow of the second process gas G2 toward the vertical direction may become turbulent due to the influence of the baffle 40. Furthermore, if it is above the above range, the flow of the second process gas G2 toward the baffle 40 side becomes difficult to achieve, and the flow of the second process gas G2 toward the center direction of the wafer W becomes difficult to realize.

[0109] Furthermore, from the viewpoint of achieving a highly uniform impurity concentration distribution by ensuring the flow of the second process gas G2 toward the center of the wafer W, it is preferable that the inner circumferential diameter d5 of the baffle 40 is 105% to 200% of the diameter d4 of the base 14.

[0110] In the vapor phase growth method of the first embodiment, the rotational speed of the wafer W needs to be 300 rpm or more. If the rotational speed is less than 300 rpm, the amount of gas G2 introduced into the center direction of the wafer W in the second process may become insufficient.

[0111] Furthermore, it is preferable that the first flow rate and the second flow rate are 0.2 m / sec or more and 1.0 m / sec or less, and more preferably 0.2 m / sec or more and 0.5 m / sec or less. If they are below the above ranges, the first process gas G1 and the second process gas G2 are easily mixed, and the effect of the first embodiment cannot be observed. In addition, if they are above the above ranges, the vertical flow of the second process gas G2 becomes too fast, and the amount of the second process gas G2 introduced into the center direction of the wafer W may become insufficient.

[0112] From the viewpoint of controlling the amount of the second process gas G2 introduced into the center direction of the wafer W, it is preferable that the second flow rate of the second process gas G2 is 50% to 200% of the first flow rate of the first process gas G1. From the viewpoint of increasing the amount of the second process gas G2 introduced into the center direction of the wafer W, it is preferable that the second flow rate of the second process gas G2 is less than the first flow rate of the first process gas G1. Furthermore, from the viewpoint of suppressing the amount of the second process gas G2 introduced into the center direction of the wafer W, it is preferable that the second flow rate of the second process gas G2 is greater than the first flow rate of the first process gas G1.

[0113] Furthermore, in the vapor phase growth apparatus and method of the first embodiment, the uniformity of the concentration distribution of n-type impurities in the SiC film can be improved by changing the diameter of the wafer W. For example, reducing the inner circumferential diameter d1 of the second region 12b of the process gas supply section 12 and increasing the C / Si ratio of the outer circumference of the wafer W by reducing the diameter of the wafer W requires a design change or replacement of the process gas supply section 12, which is not easy.

[0114] Figure 7 This is an explanatory diagram of the flow of process gas within the reaction chamber of the vapor-phase growth method according to the first embodiment. Figure 7 In, it is shown that in relation to Figure 4 For the case of chip W, the diameter becomes about two-thirds of the original chip W.

[0115] like Figure 7 As shown, by increasing the rotational speed of wafer W or decreasing the second flow rate of the second process gas G2, the amount of the second process gas G2 introduced towards the center of wafer W can be increased. Therefore, even when the diameter of wafer W varies, it is easy to improve the uniformity of the concentration distribution of n-type impurities in the SiC film.

[0116] According to the vapor phase growth apparatus and vapor phase growth method of the first embodiment, the uniformity of the concentration distribution of n-type impurities in the SiC film is improved.

[0117] (Second Implementation)

[0118] The vapor phase growth apparatus of the second embodiment is the same as that of the first embodiment, except that the process gas supply section also has a third region and a gas passage hole is provided on the side wall. Therefore, some descriptions that are repeated in the first embodiment will be omitted.

[0119] Figure 8This is a schematic cross-sectional view of the vapor phase growth apparatus of the second embodiment. The vapor phase growth apparatus of the second embodiment is, for example, a monolithic epitaxial growth apparatus for epitaxially growing a single-crystal SiC film on a single-crystal SiC substrate.

[0120] The vapor phase growth apparatus 200 of the second embodiment includes a reaction chamber 10 and a process gas supply unit 12. The reaction chamber 10 includes a base 14 (substrate holding part), a rotating body 16, a rotating shaft 18, a rotating drive mechanism 20, a first heater 22, a reflector 28, a support column 30, a fixed stage 32, a fixed shaft 34, a baffle 40 (side wall), a second heater 42, and a gas outlet 44. The process gas supply unit 12 includes a first gas supply port 52, a second gas supply port 54, a third gas supply port 55, a first gas ejection port 56, a second gas ejection port 58, and a third gas ejection port 59. The area of ​​the process gas supply unit 12 with the first gas ejection port 56 is designated as region 12a, the area with the second gas ejection port 58 is designated as region 12b, and the area with the third gas ejection port 59 is designated as region 12c.

[0121] The first gas supply port 52, the second gas supply port 54, and the third gas supply port 55 are located on the upper part of the process gas supply unit 12. The first gas supply port 52 supplies, for example, a first process gas G1 to the process gas supply unit 12. The second gas supply port 54 supplies, for example, a second process gas G2 to the process gas supply unit 12. The third gas supply port 55 supplies, for example, a third process gas G3 to the process gas supply unit 12.

[0122] The first gas ejector hole 56, the second gas ejector hole 58, and the third gas ejector hole 59 are located at the lower part of the process gas supply unit 12. The first gas ejector hole 56, the second gas ejector hole 58, and the third gas ejector hole 59 are arranged facing the reaction chamber 10.

[0123] The second gas ejector hole 58 is disposed around the first gas ejector hole 56. The third gas ejector hole 59 is disposed around the second gas ejector hole 58. The area of ​​the process gas supply unit 12 where the first gas ejector hole 56 is disposed is the first area 12a, the area where the second gas ejector hole 58 is disposed is the second area 12b, and the area where the third gas ejector hole 59 is disposed is the third area 12c.

[0124] The third gas outlet 59 supplies the third process gas G3 to the area between the baffle 40 and the second heater 42. The third process gas G3 is, for example, argon.

[0125] The baffle 40 has a gas passage hole 60. The gas passage hole 60 is configured to allow the third process gas G3 to pass from the second heater 42 side to the wafer W side.

[0126] Figure 9 This is an explanatory diagram of the flow of process gas within the reaction chamber of the vapor-phase growth method according to the second embodiment. (See diagram for reference.) Figure 9 As shown, the third process gas G3 flows towards the wafer W side after passing through the gas through-hole 60. Furthermore, the flow of the third process gas G3 pushes the flow of the second process gas towards the center of the wafer W. As a result, the amount of the second process gas G2 introduced towards the center of the wafer W increases.

[0127] According to the vapor phase growth apparatus and method of the second embodiment, the amount of the second process gas G2 introduced towards the center of the wafer W can be adjusted by using the third process gas G3. Therefore, the uniformity of the concentration distribution of n-type impurities in the SiC film is further improved.

[0128] (Third Implementation)

[0129] The vapor phase growth method of the third embodiment involves rotating a substrate at a rotational speed of 300 rpm or more, heating the substrate, supplying a first process gas containing carbon, silicon, and the aforementioned n-type impurities to the substrate, supplying a second process gas containing carbon and the aforementioned n-type impurities with a higher carbon / silicon atomic ratio than the first process gas to the substrate for regions further outward than the region where the first process gas was supplied, forming a first silicon carbide film on the surface of the substrate when the effective carbon / silicon atomic ratio of the process gas directly above the surface of the substrate is less than 1, supplying a third process gas containing carbon, silicon, and the aforementioned n-type impurities to the substrate, supplying a fourth process gas containing carbon and the aforementioned n-type impurities with a higher carbon / silicon atomic ratio than the third process gas to the substrate for regions further outward than the region where the third process gas was supplied, and forming a second silicon carbide film with a lower concentration of the aforementioned n-type impurities than the first silicon carbide film on the surface of the substrate when the effective carbon / silicon atomic ratio of the process gas directly above the surface of the substrate is 1 or more.

[0130] The vapor phase growth method of the third embodiment differs from that of the vapor phase growth method of the first embodiment in that a first silicon carbide film and a second silicon carbide film with different n-type impurity concentrations are formed on the substrate. Hereinafter, some descriptions that are repeated in the vapor phase growth apparatus and vapor phase growth method of the first embodiment will be omitted.

[0131] The vapor phase growth method of the third embodiment uses Figure 1 The epitaxial growth apparatus shown is illustrated. Furthermore, the vapor phase growth method of the third embodiment uses an epitaxial growth apparatus with… Figure 2 The epitaxial growth apparatus shown is located in the process gas supply section. The following explanation will use the case where the n-type impurity is nitrogen as an example.

[0132] Figure 10This is a cross-sectional view of a silicon carbide film formed using the vapor phase growth method of the third embodiment. A buffer film 501 (first silicon carbide film) and an n-type film 502 (second silicon carbide film) are formed above the substrate 500.

[0133] Substrate 500 is a single-crystal SiC wafer. Substrate 500 contains nitrogen as an n-type impurity. The nitrogen concentration of substrate 500 is, for example, 1 × 10⁻⁶. 17 cm －3 Above 1×10 19 cm －3 the following.

[0134] The buffer film 501 is a single-crystal SiC film. The buffer film 501 functions to suppress the migration of basal plane dislocations (BPDs) contained in the substrate 500 to the n-type film 502. During the growth of the buffer film 501, for example, basal plane dislocations are transformed into other types of dislocations.

[0135] Buffer membrane 501 contains nitrogen as an n-type impurity. The nitrogen concentration of buffer membrane 501 is, for example, 1 × 10⁻⁶. 17 cm －3 Above 1×10 19 cm －3 The thickness of the buffer film 501 is, for example, 0.5 μm or more and 2 μm or less.

[0136] From the viewpoint of suppressing the migration of basal surface dislocations into the n-type film 502, it is preferable that the nitrogen concentration of the buffer film 501 is 1×10⁻⁶. 17 cm －3 above.

[0137] n-type film 502 is a single-crystal SiC film. n-type film 502 contains nitrogen as an n-type impurity. The nitrogen concentration of n-type film 502 is, for example, 1 × 10⁻⁶. 14 cm －3 Above 1×10 16 cm －3 The nitrogen concentration of the n-type membrane 502 is lower than that of the buffer membrane 501. The thickness of the n-type membrane 502 is, for example, 10 μm or more and 300 μm or less.

[0138] The n-type film 502 is used, for example, as a drift layer in high-voltage devices such as transistors and diodes. From the viewpoint of extending minority carrier lifetime, the n-type film 502 preferably reduces the amount of carbon vacancies that function as lifetime control agents.

[0139] From the viewpoint of achieving high withstand voltage in transistors and diodes, it is preferable that the nitrogen concentration of the n-type film 502 is 1×10⁻⁶. 16 cm －3 the following.

[0140] First, the substrate 14, on which the wafer W is placed, is moved into the reaction chamber 10. The wafer W is single-crystal SiC.

[0141] Next, the wafer W is rotated at a speed of 300 rpm or higher by the rotary drive mechanism 20. Then, the wafer W is heated by the first heater 22 and the second heater 42.

[0142] Next, a first process gas G1 is supplied from the first region 12a of the process gas supply section 12 toward the center of the surface of the wafer W. The first process gas G1 ejected from the first gas ejection port 56 becomes a laminar flow from the process gas supply section 12 toward the surface of the wafer W. The first process gas contains carbon, silicon, and nitrogen.

[0143] Additionally, a second process gas G2 is supplied from the second region 12b of the process gas supply unit 12 to a region further outward than the center of the wafer W. The second process gas G2 is supplied to the outer region of the wafer W compared to the first process gas G1. The second process gas G2 ejected from the second gas ejection port 58 becomes a laminar flow from the process gas supply unit 12 toward the surface of the wafer W. The second process gas contains carbon and nitrogen.

[0144] The first process gas G1 is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, an auxiliary gas, and a carrier gas. The silicon source gas is, for example, silane (SiH4). The carbon source gas is, for example, propane (C3H8). The n-type impurity dopant gas is nitrogen. The auxiliary gas is, for example, hydrogen chloride (HCl). The carrier gas is, for example, argon or hydrogen.

[0145] The second process gas G2 is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, and a carrier gas. The silicon source gas is, for example, silane. The carbon source gas is, for example, propane. The n-type impurity dopant gas is nitrogen. The carrier gas is, for example, argon or hydrogen.

[0146] The C / Si ratio of the second process gas G2 supplied from the process gas supply unit 12 to the reaction chamber 10 is higher than that of the first process gas G1.

[0147] By supplying process gas G1 and process gas G2 to the surface of wafer W, a buffer film 501 containing nitrogen as an n-type impurity is formed on the surface of wafer W. The nitrogen concentration of the buffer film 501 is, for example, 1 × 10⁻⁶. 17 cm －3 The thickness of the buffer film 501 is, for example, 0.5 μm or more and 2 μm or less.

[0148] The buffer film 501 is formed in a state where the effective carbon / silicon atomic ratio of the process gas directly above the surface of the wafer W is less than 1. For example, when forming the buffer film 501, the effective carbon / silicon atomic ratio directly above the surface of the wafer W in the central portion and the outer peripheral portion of the wafer W is less than 1. Hereinafter, the effective carbon / silicon atomic ratio will be referred to as the "effective C / Si ratio".

[0149] Furthermore, the term "chip center" refers to, for example, the area within 5 mm of the center of chip W. The term "chip periphery" refers to, for example, the area within 5 mm of the outer periphery of chip W.

[0150] Figure 11 This is an explanatory diagram of the vapor phase growth method according to the third embodiment. Figure 11 This is an explanatory graph showing the relationship between the introduced C / Si ratio and the film growth rate of the SiC film on the substrate.

[0151] Here, the so-called "imported C / Si ratio" refers to... Figure 2 The carbon / silicon atomic ratio of the process gas introduced into the process gas supply section is shown. More specifically, it is the carbon / silicon atomic ratio of silicon in the source gas introduced into the source gas supply port 82 (for silicon) to carbon in the source gas introduced into the source gas supply port 84 (for carbon).

[0152] Figure 11 This indicates a situation where the amount of silicon in the source gas introduced to the silicon through the source gas supply port 82 is fixed, while the amount of carbon in the source gas introduced to the carbon through the source gas supply port 84 is varied, thus changing the introduced C / Si ratio.

[0153] If the introduced C / Si ratio increases and exceeds a specified value, the film growth rate saturates. The point at which the film growth rate saturates is called the saturation point. Film growth rate saturation occurs when the effective C / Si ratio of the process gas directly above the substrate surface reaches 1. In other words, it occurs at the point where carbon:silicon = 1:1. Since the C / Si ratio in SiC films is 1, if the effective C / Si ratio of the process gas directly above the substrate surface is greater than 1, the film growth rate saturates.

[0154] The saturation point A at the center of the wafer is Figure 11 The position of arrow A in the diagram. The saturation point B on the outer periphery of the wafer is... Figure 11 The position of arrow B in the diagram. In the vapor phase growth apparatus of the third embodiment, the process gas is controlled such that the C / Si ratio is higher towards the outer periphery of the wafer relative to the center of the wafer. Therefore, the saturation point B at the outer periphery of the wafer has a lower C / Si ratio compared to the saturation point A at the center of the wafer.

[0155] In the center of the wafer, the effective C / Si ratio is 1 or higher when the C / Si ratio is introduced above the saturation point A, and less than 1 when the C / Si ratio is introduced below the saturation point A. Furthermore, in the outer periphery of the wafer, the effective C / Si ratio is 1 or higher when the C / Si ratio is introduced above the saturation point B, and less than 1 when the C / Si ratio is introduced below the saturation point B.

[0156] To achieve an effective C / Si ratio of 1 or higher in both the center and periphery of the wafer, a C / Si ratio above the saturation point A is required. On the other hand, to achieve an effective C / Si ratio of less than 1 in both the center and periphery of the wafer, a C / Si ratio below the saturation point B is required.

[0157] By setting an appropriate C / Si ratio, the desired effective C / Si ratio at the desired wafer surface location (W) can be achieved.

[0158] After the buffer film 501 is formed, a third process gas is supplied from the first region 12a of the process gas supply unit 12 toward the center of the surface of the wafer W. The third process gas ejected from the first gas ejection hole 56 becomes a laminar flow from the process gas supply unit 12 toward the surface of the wafer W. The third process gas contains carbon, silicon, and nitrogen.

[0159] Additionally, a fourth process gas is supplied from the second region 12b of the process gas supply unit 12 to a region further outward than the center of the wafer W. The fourth process gas is supplied to the region outside the wafer W compared to the third process gas. The fourth process gas ejected from the second gas ejection port 58 becomes a laminar flow from the process gas supply unit 12 toward the surface of the wafer W. The fourth process gas contains carbon and nitrogen.

[0160] The third process gas is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, an auxiliary gas, and a carrier gas. The silicon source gas is, for example, silane. The carbon source gas is, for example, propane. The n-type impurity dopant gas is nitrogen. The auxiliary gas is, for example, hydrogen chloride. The carrier gas is, for example, argon or hydrogen.

[0161] The fourth process gas is, for example, a mixture of a silicon source gas, a carbon source gas, an n-type impurity dopant gas, and a carrier gas. The silicon source gas is, for example, silane. The carbon source gas is, for example, propane. The n-type impurity dopant gas is nitrogen. The carrier gas is, for example, argon or hydrogen.

[0162] The C / Si ratio of the fourth process gas supplied from the process gas supply unit 12 to the reaction chamber 10 is higher than that of the third process gas.

[0163] By supplying the third process gas and the fourth process gas to the surface of the wafer W, an n-type film 502 containing nitrogen is formed on the surface of the wafer W. The nitrogen concentration of the n-type film 502 is, for example, 1 × 10⁻⁶. 16 cm －3 The thickness of the n-type film 502 is, for example, 10 μm or more and 300 μm or less.

[0164] The n-type film 502 is formed in a state where the effective carbon / silicon atomic ratio, i.e., the effective C / Si ratio, is 1 or higher in the process gas directly above the surface of the wafer W. During the formation of the n-type film 502, the effective C / Si ratio of the process gas region directly above the surface of the wafer W, including the center of the wafer W and the area within 5 mm of the outer periphery of the wafer W, is 1 or higher. The introduced C / Si ratio is set to have an effective C / Si ratio of 1 or higher.

[0165] After the buffer film 501 and the n-type film 502 are formed, the heating performed by the first heater 22 and the second heater 42 is stopped, causing the temperature of the wafer W to drop. Then, the wafer W and the substrate 14 are removed from the reaction chamber 10.

[0166] Next, the function and effects of the vapor phase growth method in the third embodiment will be explained.

[0167] Figure 12 This is an explanatory diagram illustrating the function and effect of the vapor phase growth method in the third embodiment. Figure 12 A graph showing the relationship between the introduced C / Si ratio and the distribution shape of nitrogen concentration within the W-plane of the wafer. Additionally, Figure 12 It is a graph that only qualitatively illustrates the shape changes of nitrogen concentration distribution under various conditions, not a graph that illustrates the high and low changes of nitrogen concentration under various conditions.

[0168] like Figure 12 As shown, when the C / Si ratio is low, the nitrogen concentration at the periphery of wafer W is higher than that at the center. As the C / Si ratio increases from low to medium, the nitrogen concentration at the periphery decreases, and the nitrogen concentration distribution in the SiC film becomes more uniform. Furthermore, if the C / Si ratio is increased to high, the nitrogen concentration at the periphery of wafer W further decreases, reducing the uniformity of the nitrogen concentration distribution in the SiC film. Finally, if the C / Si ratio is further increased to very high, the nitrogen concentration distribution becomes uniform again.

[0169] From a low C / Si ratio to a medium C / Si ratio, the effective C / Si ratio within the plane of wafer W is sufficiently low compared to 1. Conversely, if the C / Si ratio is high, the effective C / Si ratio at the center of wafer W is sufficiently low compared to 1, while the effective C / Si ratio at the outer periphery of wafer W is close to 1. Furthermore, if the C / Si ratio is extremely high, the effective C / Si ratio within the plane of wafer W is sufficiently high compared to 1. In regions where the effective C / Si ratio is below 1, the rate of decrease in nitrogen concentration in the SiC film increases with increasing effective C / Si ratio; conversely, in regions where the effective C / Si ratio is above 1, the rate of decrease in nitrogen concentration in the SiC film decreases with increasing effective C / Si ratio. That is, if the introduced C / Si ratio is increased from low to high, the difference between the effective C / Si ratio at the periphery of wafer W and the effective C / Si ratio at the center of wafer W becomes larger. Furthermore, the rate of reduction in nitrogen concentration in the SiC film is greater with the increase in the effective C / Si ratio. Therefore, the nitrogen concentration at the periphery of wafer W decreases more easily compared to the nitrogen concentration at the center of wafer W. On the other hand, if the introduced C / Si ratio is increased from high to extremely high, a slight increase in the introduced C / Si ratio at the periphery of wafer W results in an effective C / Si ratio exceeding 1, reducing the rate of reduction in nitrogen concentration in the SiC film. However, at the center of wafer W, unless the introduced C / Si ratio is significantly increased, the effective C / Si ratio will not exceed 1. Therefore, the nitrogen concentration at the center of wafer W decreases more easily compared to the nitrogen concentration at the periphery. Based on this reasoning, the following occurs... Figure 12 The shape of the nitrogen concentration distribution in such SiC films changes.

[0170] Figure 13 This is an explanatory diagram illustrating the function and effect of the vapor phase growth method according to the third embodiment. The figures show measured values ​​showing the relationship between the introduced C / Si ratio and the film growth rate. The saturation point A at the center of the wafer has a C / Si ratio of approximately 1.65. The saturation point B at the outer periphery of the wafer has a C / Si ratio of approximately 1.5.

[0171] To achieve an effective C / Si ratio of 1 or higher in both the center and periphery of the wafer, a C / Si ratio of at least 1.65 or higher is required, which corresponds to a saturation point A. Conversely, to achieve an effective C / Si ratio of less than 1 in both the center and periphery of the wafer, a C / Si ratio of less than 1.5 is required, which corresponds to a C / Si ratio of less than 1.5, which corresponds to a saturation point B.

[0172] Figure 14 This is an explanatory diagram illustrating the function and effect of the vapor phase growth method in the third embodiment. Figure 14 In Figure 13Under the same process conditions, the nitrogen concentration distribution within the W-plane of the wafer is represented by the introduced C / Si ratio as a parameter. The introduced C / Si ratio varies between 1.20 and 1.95. Figure 14 The measurement results were obtained using a wafer W with a diameter of 150 mm.

[0173] according to Figure 14 It can be seen that when the C / Si ratio is introduced to 1.35 and above, the nitrogen concentration distribution within the W-plane of the wafer becomes more uniform. These correspond to the cases where the effective C / Si ratio is less than 1 and the cases where the effective C / Si ratio is 1 or above, respectively.

[0174] In the vapor phase growth method of the third embodiment, during the formation of the high-nitrogen-concentration buffer film 501, the effective C / Si ratio of the surface of the wafer W is made less than 1. This allows the formation of a buffer film 501 with high nitrogen concentration and high in-plane uniformity of nitrogen concentration on the wafer W. Furthermore, during the formation of the low-nitrogen-concentration n-type film 502, the effective C / Si ratio of the surface of the wafer W is made 1 or more. This allows the formation of an n-type film 502 with low nitrogen concentration and high in-plane uniformity of nitrogen concentration on the wafer W.

[0175] Furthermore, in the formation of the n-type film 502, by ensuring that the effective C / Si ratio on the surface of the wafer W is 1 or higher, the amount of carbon vacancies in the film can be reduced. Since the effective C / Si ratio is 1 or higher, carbon remains, thus suppressing the generation of carbon vacancies in the film.

[0176] According to the vapor phase growth method of the third embodiment, a silicon carbide film suitable for manufacturing high-voltage devices such as transistors and diodes can be formed.

[0177] The embodiments of the present invention have been described above with reference to specific examples. These embodiments are merely illustrative and do not limit the present invention. Furthermore, the constituent elements of each embodiment can be appropriately combined.

[0178] In this embodiment, the case of forming a single-crystal SiC film was described as an example, but the present invention can also be applied to the formation of polycrystalline or amorphous SiC films.

[0179] In addition, in the embodiments, a single-crystal SiC wafer was described as an example of a substrate, but the substrate is not limited to a single-crystal SiC wafer.

[0180] Furthermore, in the embodiments, nitrogen was used as an example of an n-type impurity, but phosphorus (P) can also be used as an n-type impurity, for example.

[0181] In this embodiment, details regarding the apparatus configuration, manufacturing method, and other aspects of the invention that are not directly necessary are omitted, but necessary apparatus configurations and manufacturing methods can be appropriately selected and used. Furthermore, all vapor phase growth apparatuses, annular supports, and vapor phase growth methods incorporating elements of the invention and for which design modifications can be appropriately made by those skilled in the art are included within the scope of this invention. The scope of this invention is defined by the scope of the claims and their equivalents.

[0182] Symbol Explanation

[0183] 10 Reaction Chamber

[0184] 10a Inner wall

[0185] 12 Process Gas Supply Department

[0186] 12a Region 1

[0187] 12b Area 2

[0188] 14. Base (substrate holding section)

[0189] 14a Maintain wall

[0190] 20 Rotary drive mechanism

[0191] 22 First heater

[0192] 40 Baffle (side wall)

[0193] 42. Second heater

[0194] 100 Vapor phase growth apparatus

[0195] G1 Process 1 Gas

[0196] G2 Second Process Gas

[0197] W-shaped wafer (substrate)

[0198] d1 Inner diameter of the 2nd area

[0199] d2 is the outer diameter of region 2.

[0200] d3 Maintains the diameter of the wall

[0201] d5 Inner circumference diameter of the baffle (side wall)

Claims

1. A vapor phase growth apparatus, comprising: Reaction chamber; A substrate holding portion is provided in the reaction chamber and is capable of holding a substrate. It has a holding wall that can hold the outer periphery of the substrate and the holding wall suppresses horizontal movement of the substrate, thereby holding the substrate with a predetermined gap between the outer periphery of the substrate and the holding wall. A process gas supply unit is provided above the reaction chamber and has a first region and a second region. The first region is capable of supplying the reaction chamber with a first process gas containing carbon, silicon and n-type impurities. The second region is provided around the first region and is capable of supplying the reaction chamber with a second process gas containing carbon, silicon and n-type impurities. The second process gas has a higher carbon / silicon atomic ratio than the first process gas. The inner circumferential diameter of the second region is more than 75% and less than 130% of the diameter of the retaining wall. The sidewall, located in the reaction chamber between the process gas supply section and the substrate holding section, has an inner circumferential diameter that is 110% to 200% of the outer circumferential diameter of the second region. The first heater is disposed below the substrate holding portion; A second heater is disposed between the aforementioned side wall and the inner wall of the aforementioned reaction chamber; and, A rotary drive mechanism rotates the substrate holding section. The aforementioned process gas supply unit has a third region disposed around the second region, which is capable of supplying a third process gas to the region between the sidewall and the second heater. The aforementioned sidewall has a gas passage hole that allows the aforementioned third process gas to pass from the aforementioned second heater side of the aforementioned sidewall to the aforementioned substrate side of the aforementioned sidewall, and the flow of the aforementioned second process gas is introduced towards the center direction of the aforementioned substrate through the flow of the aforementioned third process gas passing through the aforementioned gas passage hole.

2. The vapor phase growth apparatus as described in claim 1, wherein, The gas used in the third process described above is argon.

3. A vapor-phase growth method, Rotate the substrate. Heating the above-mentioned substrate, A first process gas containing carbon, silicon, and n-type impurities is supplied toward the aforementioned substrate at a first flow rate. Towards the substrate, a second process gas containing carbon, silicon, and n-type impurities is supplied at a second flow rate to a region further outward than the region to which the first process gas is supplied. This second process gas has a higher carbon / silicon atomic ratio compared to the first process gas. A third process gas is supplied to a region further outward than the region where the second process gas is supplied, toward the substrate, in such a manner that the flow of the second process gas is introduced toward the center of the substrate. The amount of the second process gas introduced toward the center of the substrate is adjusted by controlling the first flow rate, the second flow rate, and the rotation speed, and after the second process gas is introduced toward the center of the substrate, it becomes a horizontal flow toward the outside of the substrate, forming a silicon carbide film on the surface of the substrate.

4. The vapor phase growth method as described in claim 3, wherein, The first flow velocity and the second flow velocity mentioned above are both above 0.2 m / sec and below 1.0 m / sec.

5. The vapor phase growth method as described in claim 3, wherein, The second flow velocity mentioned above is more than 50% and less than 200% of the first flow velocity mentioned above.

6. The vapor phase growth method as described in claim 3, wherein, The substrate was heated to 1500°C or higher.

7. The vapor phase growth method as described in claim 3, wherein, The gases in the first and second processes mentioned above contain nitrogen.

8. The vapor phase growth method as described in claim 3, wherein, The substrate is rotated at a speed of 300 rpm or more.

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