Atmosphere growth apparatus and atmosphere growth method

Abstract

We provide a vapor phase growth apparatus and a vapor phase growth method capable of reducing defects in the film. A vapor phase growth apparatus of an embodiment comprises a reaction chamber, a holder provided in the reaction chamber for loading a substrate, a source gas path for supplying a first source gas containing silicon and chlorine into the reaction chamber, a purge gas path for supplying a purge gas containing chlorine and hydrogen into the reaction chamber, and a control unit for controlling the supply of the first source gas and purge gas into the reaction chamber. The control unit controls the ratio of the sum of the second amount of chlorine containing the first source gas and the third amount of chlorine containing the purge gas to the first amount of silicon containing the first source gas during a first period such that the ratio is 30 or more, and the control unit controls the flow rate of the first source gas to increase during a second period after the first period.

Description

Technology Field

[0001] This application enjoys priority based on Japanese Patent Application No. 2024-017526 (filing date: February 7, 2024). By referring to this basic application, this application includes all the contents of the basic application.

[0002] The present invention relates to a vapor phase growth apparatus and a vapor phase growth method for forming a film by supplying gas to a substrate. Background Technology

[0003] As a method for forming a high-quality semiconductor film, there is an epitaxial growth technique that forms a single-crystal film on the surface of a substrate by vapor phase growth. In a vapor phase growth apparatus using epitaxial growth technique, a substrate is loaded into a holder in a reaction chamber maintained at atmospheric pressure or reduced pressure.

[0004] Then, while heating the substrate, a process gas containing the raw material for the film is supplied to the reaction chamber via a gas inlet at the top of the reaction chamber. A thermal reaction of the process gas occurs on the surface of the substrate, and an epitaxial single-crystal film is formed on the surface of the substrate.

[0005] Defects may occur on the surface of the formed epitaxial single-crystal film. The defects are, for example, pits or bumps. The problem to be solved

[0006] One aspect of the present invention provides a vapor phase growth apparatus and a vapor phase growth method capable of reducing defects in a film. means of solving the problem

[0007] A vapor phase growth apparatus of one embodiment of the present invention comprises a reaction chamber, a holder provided in the reaction chamber for loading a substrate, a source gas path for supplying a first source gas containing silicon and chlorine into the reaction chamber, a purge gas path for supplying a purge gas containing chlorine and hydrogen into the reaction chamber, and a control unit for controlling the supply of the first source gas and the purge gas into the reaction chamber. The control unit controls the ratio ((second amount of substance + third amount of substance) / first amount of substance) of the sum of the first amount of substance containing chlorine in the first source gas supplied to the reaction chamber per unit time and the first amount of substance containing chlorine in the purge gas supplied to the reaction chamber per unit time, to the first amount of substance containing silicon in the first source gas supplied to the reaction chamber per unit time during a first period, such that the ratio is 30 or more. The control unit controls the flow rate of the first source gas to increase during a second period after the first period.

[0008] A vapor phase growth method of one embodiment of the present invention is a vapor phase growth method for forming a silicon carbide film on a substrate loaded in a holder provided in a reaction chamber, wherein during a first period, a first source gas containing silicon and chlorine and a purge gas containing chlorine and hydrogen are supplied into the reaction chamber such that the ratio of the sum of the second amount of chlorine containing the first source gas supplied to the reaction chamber per unit time and the third amount of chlorine containing the purge gas supplied to the reaction chamber per unit time to the first amount of silicon containing the first source gas supplied to the reaction chamber per unit time ((second amount of chlorine + third amount of chlorine) / first amount of chlorine) is 30 or more, and during a second period after the first period, the flow rate of the first source gas supplied into the reaction chamber is increased. Brief explanation of the drawing

[0009] FIG. 1 is a schematic cross-sectional view of a vapor growth apparatus of a first embodiment. FIG. 2 is an enlarged schematic cross-sectional view of a part of the gas introduction section of a vapor phase growth device of the first embodiment. FIG. 3 is an enlarged schematic cross-sectional view of a part of the gas introduction section of a vapor phase growth device of the first embodiment. FIG. 4 is an explanatory diagram of control by the control circuit of the vapor growth device of the first embodiment. FIG. 5 is an explanatory diagram of control by the control circuit of the vapor growth device of the first embodiment. FIG. 6 is an explanatory diagram of control by the control circuit of the vapor growth device of the first embodiment. FIGS. 7a and 7b are explanatory diagrams of the operation and effects of a vapor growth apparatus and a vapor growth method of a first embodiment. FIG. 8 is an explanatory diagram of the operation and effects of the vapor growth apparatus and vapor growth method of the first embodiment. FIG. 9 is an explanatory diagram of a vapor growth apparatus and a vapor growth method of a first embodiment. FIG. 10 is an explanatory diagram of a vapor growth apparatus and a vapor growth method of a first embodiment. FIG. 11 is an explanatory diagram of a vapor growth apparatus and a vapor growth method of a first embodiment. FIG. 12 is a schematic cross-sectional view of a vapor growth device of a second embodiment. FIG. 13 is an explanatory diagram of control by the control circuit of a vapor growth device of a second embodiment. FIG. 14 is an explanatory diagram of control by the control circuit of a vapor growth device of a second embodiment. FIG. 15 is an explanatory diagram of control by the control circuit of a vapor growth device of a second embodiment. Specific details for implementing the invention

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0011] In this specification, identical or similar components may be denoted by the same reference numerals. In this specification, the direction of gravity in a state where a vapor-phase growth device is installed to enable film formation is defined as "down," and the opposite direction is defined as "up." Accordingly, "down" refers to a position in the direction of gravity relative to a reference, and "downward" refers to the direction of gravity relative to a reference. Furthermore, "upward" refers to a position in the opposite direction of gravity relative to a reference, and "upward" refers to the opposite direction of gravity relative to a reference. Additionally, "vertical direction" refers to the direction of gravity.

[0012] Additionally, in this specification, "process gas" is a general term for gases used for forming a film, and is a concept that includes, for example, source gas, assist gas, dopant gas, carrier gas, purge gas, and mixtures thereof.

[0013] (First embodiment)

[0014] A vapor phase growth apparatus of a first embodiment comprises a reaction chamber, a holder provided in the reaction chamber for loading a substrate, a source gas path for supplying a first source gas containing silicon and chlorine into the reaction chamber, a purge gas path for supplying a purge gas containing chlorine and hydrogen into the reaction chamber, and a control unit for controlling the supply of the first source gas and purge gas into the reaction chamber. The control unit controls the ratio ((second amount of substance + third amount of substance) / first amount of substance) of the sum of the second amount of substance containing chlorine in the first source gas supplied to the reaction chamber per unit time and the third amount of substance containing chlorine in the purge gas supplied to the reaction chamber per unit time, to the first amount of substance containing silicon in the first source gas supplied to the reaction chamber per unit time during a first period, such that the ratio is 30 or more, and the control unit controls the flow rate of the first source gas to increase during a second period after the first period.

[0015] FIG. 1 is a schematic cross-sectional view of a vapor phase growth apparatus of a first embodiment. The vapor phase growth apparatus (100) of the first embodiment is a single-wafer type epitaxial growth apparatus for epitaxially growing a single-crystal SiC film (silicon carbide film) on, for example, a single-crystal SiC substrate (silicon carbide substrate). The vapor phase growth apparatus (100) of the first embodiment is a vertical type vapor phase growth apparatus in which a process gas is supplied in a longitudinal direction to the surface of a SiC substrate.

[0016] A vapor growth device (100) of the first embodiment comprises a reaction chamber (10), a gas introduction section (11), and a control circuit (12) (control section). The reaction chamber (10) includes a susceptor (14) (holder), a rotating body (16), a rotating shaft (18), a rotary driving mechanism (20), a first heater (22), a reflector (28), a support column (30), a fixing stand (32), a fixing shaft (34), a hood (40), a second heater (42), and a gas outlet (44). The gas introduction section (11) includes a first source gas area (51), a second source gas area (52), a first purge gas area (53), a second purge gas area (54), a rectifier plate (60), a partition plate (61, 62, 63), a ceiling plate (64), a first source gas conduit (71), a second source gas conduit (72), a first purge gas conduit (73), and a second purge gas conduit (74).

[0017] A vapor growth device (100) of the first embodiment includes a first source gas supply pipe (81), a second source gas supply pipe (82), a first purge gas supply pipe (83), a second purge gas supply pipe (84), a first mass flow controller MFC1, a second mass flow controller MFC2, a third mass flow controller MFC3, a fourth mass flow controller MFC4, a first valve V1, a second valve V2, a third valve V3, and a fourth valve V4.

[0018] The first source gas supply pipe (81), the first source gas region (51), and the first source gas conduit (71) form a first source gas flow path. The first source gas flow path supplies the first source gas (SG1) to the reaction chamber (10).

[0019] The second source gas supply pipe (82), the second source gas region (52), and the second source gas conduit (72) form a second source gas flow path. The second source gas flow path supplies the second source gas (SG2) to the reaction chamber (10).

[0020] The first source gas flow and the second source gas flow are examples of source gas flow.

[0021] The first purge gas supply pipe (83), the first purge gas area (53), and the first purge gas conduit (73) form a first purge gas flow path. The second purge gas supply pipe (84), the second purge gas area (54), and the second purge gas conduit (74) form a second purge gas flow path.

[0022] The first purge gas path and the second purge gas path supply purge gas PG to the reaction chamber (10). The first purge gas path and the second purge gas path are examples of purge gas paths.

[0023] A first valve V1 and a first mass flow controller MFC1 are provided in the first source gas supply pipe (81). The first valve V1 has the function of switching the introduction of the first source gas (SG1) introduced into the first source gas supply pipe (81) to start and stop the introduction. The first mass flow controller MFC1 has the function of adjusting the flow rate of the first source gas (SG1) introduced into the first source gas supply pipe (81) to a predetermined amount.

[0024] The second valve V2 and the second mass flow controller MFC2 are provided in the second source gas supply pipe (82). The second valve V2 has the function of switching the introduction of the second source gas (SG2) introduced into the second source gas supply pipe (82) to start and stop the introduction. The second mass flow controller MFC2 has the function of adjusting the flow rate of the second source gas (SG2) introduced into the second source gas supply pipe (82) to a predetermined amount.

[0025] The third valve V3 and the third mass flow controller MFC3 are provided in the first purge gas supply pipe (83). The third valve V3 has the function of switching the introduction of purge gas PG introduced into the first purge gas supply pipe (83) and the introduction of stop. The third mass flow controller MFC3 has the function of adjusting the flow rate of purge gas PG introduced into the first purge gas supply pipe (83) to a predetermined amount.

[0026] The fourth valve V4 and the fourth mass flow controller MFC4 are provided in the second purge gas supply pipe (84). The fourth valve V4 has the function of switching the introduction of purge gas PG introduced into the second purge gas supply pipe (84) to start and stop the introduction. The fourth mass flow controller MFC4 has the function of adjusting the flow rate of purge gas PG introduced into the second purge gas supply pipe (84) to a predetermined amount.

[0027] The first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the first mass flow controller MFC1, the second mass flow controller MFC2, the third mass flow controller MFC3, and the fourth mass flow controller MFC4 are controlled by the control circuit (12).

[0028] The reaction chamber (10) is, for example, made of stainless steel. The reaction chamber (10) has cylindrical walls. Inside the reaction chamber (10), a SiC film is formed on a wafer (W). The wafer (W) is an example of a substrate.

[0029] A susceptor (14) is provided in the reaction chamber (10). A wafer (W) can be loaded into the susceptor (14). An opening may be provided in the center of the susceptor (14). The susceptor (14) is an example of a holder.

[0030] The susceptor (14) is formed from a material with high heat resistance, such as SiC or carbon, or carbon coated with SiC or TaC.

[0031] The susceptor (14) is fixed to the upper part of the rotating body (16). The rotating body (16) is fixed to the rotation axis (18). The susceptor (14) is indirectly fixed to the rotation axis (18).

[0032] The rotation axis (18) can be rotated by a rotation drive mechanism (20). By rotating the rotation axis (18) by the rotation drive mechanism (20), it is possible to rotate the susceptor (14). By rotating the susceptor (14), it is possible to rotate the wafer (W) loaded on the susceptor (14).

[0033] It is possible to rotate, for example, a wafer (W) at a rotational speed of 300 rpm or more and 3000 rpm or less by means of a rotary drive mechanism (20). The rotary drive mechanism (20) is composed of, for example, a motor and a bearing.

[0034] The first heater (22) is provided below the susceptor (14). The first heater (22) is provided within the rotating body (16). The first heater (22) heats the wafer (W) held and supported by the susceptor (14) from below. The first heater (22) is, for example, a resistance heating heater. The first heater (22) is, for example, a disc-shaped plate with a comb-like pattern. Additionally, the first heater (22) may be divided into an outer heater (not shown) that heats the outer periphery of the wafer and an inner heater (not shown) that heats the inner periphery of the wafer.

[0035] The reflector (28) is provided below the first heater (22). The first heater (22) is provided between the reflector (28) and the susceptor (14).

[0036] The reflector (28) reflects heat radiated downward from the first heater (22) to improve the heating efficiency of the wafer (W). Additionally, the reflector (28) prevents a member located below the reflector (28) from being heated. The reflector (28) is, for example, in the shape of a disc. The reflector (28) is formed from a material with high heat resistance, such as carbon coated with SiC, for example.

[0037] The reflector (28) is fixed to the fixed base (32), for example, by a plurality of support columns (30). The fixed base (32) is supported, for example, by a fixed shaft (34).

[0038] In the rotating body (16), an unillustrated push-up pin is provided to detach the susceptor (14) from the rotating body (16). The push-up pin passes through, for example, the reflector (28) and the first heater (22).

[0039] The second heater (42) is provided between the hood (40) and the inner wall of the reaction chamber (10). The second heater (42) heats the wafer (W) held and supported by the susceptor (14) from above. By adding the wafer (W) to the first heater (22) and heating it with the second heater (42), it becomes possible to heat the wafer (W) to a temperature required for the growth of the SiC film, for example, 1500°C or higher. The second heater (42) is, for example, a resistance heating heater.

[0040] The hood (40) is, for example, cylindrical in shape. The hood (40) has the function of preventing process gas from coming into contact with the second heater (42). The hood (40) is formed of a material with high heat resistance, such as carbon coated with SiC, for example.

[0041] A gas outlet (44) is provided at the bottom of the reaction chamber (10). The gas outlet (44) discharges excess reaction products and excess process gases after the source gas reacts on the surface of the wafer (W) to the outside of the reaction chamber (10). The gas outlet (44) is connected to, for example, a vacuum pump not shown.

[0042] Additionally, the reaction chamber (10) is provided with a wafer inlet / outlet and a gate valve, which are not shown. Through the wafer inlet / outlet and the gate valve, it is possible to bring a wafer (W) into the reaction chamber (10) or take it out of the reaction chamber (10).

[0043] The gas introduction section (11) is provided on the reaction chamber (10).

[0044] In the first source gas area (51), the first source gas (SG1) is introduced from the first source gas supply pipe (81). The first source gas area (51) is provided between the first purge gas area (53) and the ceiling plate (64).

[0045] In the second source gas area (52), the second source gas (SG2) is introduced from the second source gas supply pipe (82). The second source gas area (52) is provided between the second purge gas area (54) and the first purge gas area (53).

[0046] In the first purge gas area (53), purge gas PG is introduced from the first purge gas supply pipe (83). The first purge gas area (53) is provided between the second source gas area (52) and the first source gas area (51).

[0047] In the second purge gas area (54), purge gas PG is introduced from the second purge gas supply pipe (84). The second purge gas area (54) is provided between the second source gas area (52) and the reaction chamber (10).

[0048] A rectifier plate (60) is provided between the reaction chamber (10) and the second purge gas region (54). The rectifier plate (60) has a plurality of holes (60a) and a plurality of holes (60b).

[0049] A partition plate (61) is provided between the second purge gas region (54) and the second source gas region (52). The partition plate (61) has a plurality of holes (61a).

[0050] A partition plate (62) is provided between the second source gas region (52) and the first purge gas region (53). The partition plate (62) has a plurality of holes (62a).

[0051] A partition plate (63) is provided between the first purge gas area (53) and the first source gas area (51). The partition plate (63) has a hole (63a).

[0052] The ceiling plate (64) is provided on the first source gas area (51).

[0053] The first source gas (SG1) is a source gas of silicon (Si). The first source gas (SG1) includes silicon (Si) and chlorine (Cl). The first source gas (SG1) is, for example, silane (SiH4) or chlorosilane (SiH4). 4-n Cl n : n=1 to 4) is included. The first source gas (SG1) includes, for example, hydrogen chloride (HCl). The first source gas (SG1) includes, for example, hydrogen gas (H2). The first source gas (SG1) is, for example, a mixed gas of silane (SiH4), hydrogen chloride (HCl), and hydrogen gas (H2).

[0054] Hydrogen chloride (HCl) is an assist gas that inhibits the clustering of silicon. In addition, hydrogen chloride has the function of etching by-products containing silicon that are deposited in the flow path of the first source gas (SG1).

[0055] Hydrogen gas (H2) is a carrier gas. It is also possible to use, for example, argon gas (Ar) as a carrier gas.

[0056] The second source gas (SG2) is a source gas of carbon (C). The second source gas (SG2) contains carbon (C). The second source gas (SG2) contains, for example, hydrocarbons. The second source gas (SG2) is, for example, a mixed gas of propane (C3H8) and hydrogen gas (H2).

[0057] The second source gas (SG2) includes, for example, a dopant gas of n-type impurities. The dopant gas of n-type impurities is, for example, nitrogen gas.

[0058] The purge gas PG has the function of preventing the first source gas (SG1) supplied to the reaction chamber (10) from returning from the reaction chamber (10) side into the interior of the first purge gas conduit (73). Additionally, the purge gas PG has the function of preventing the second source gas (SG2) supplied to the reaction chamber (10) from returning from the reaction chamber (10) side into the interior of the second purge gas conduit (74).

[0059] Purge gas PG contains chlorine (Cl) and hydrogen (H). Purge gas PG contains, for example, hydrogen chloride (HCl). Purge gas PG contains, for example, hydrogen gas (H2). Purge gas PG is a mixed gas of, for example, hydrogen chloride (HCl) and hydrogen gas (H2).

[0060] Instead of hydrogen gas (H2), it is also possible to use, for example, argon gas (Ar).

[0061] The atomic concentration of chlorine in the purge gas PG is lower than, for example, the atomic concentration of chlorine in the first source gas (SG1). The atomic concentration of chlorine in the purge gas PG is, for example, one-fifth or less of the atomic concentration of chlorine in the first source gas (SG1). In addition, the purge gas PG introduced into the first purge gas supply pipe (83) and the purge gas PG introduced into the second purge gas supply pipe (84) may each have different gas mixing ratios and different types of gas.

[0062] FIG. 2 is an enlarged schematic cross-sectional view of a part of the gas introduction section of a gas phase growth device of a first embodiment. FIG. 2 is a cross-sectional view including a first source gas conduit (71) and a first purge gas conduit (73).

[0063] The first source gas conduit (71) supplies the first source gas (SG1) to the reaction chamber. The first source gas conduit (71) is inserted into the holes (60a, 61a, 62a, 63a). The first source gas conduit (71) passes through the rectifier plate (60) and the partition plates (61, 62, 63).

[0064] The first source gas conduit (71) has an annular flange (71a) at the top. The first source gas conduit (71) is detachable from the partition plate (63). The first source gas conduit (71) supports its own weight by having the flange (71a) loaded onto the partition plate (63).

[0065] The first purge gas conduit (73) supplies purge gas PG to the reaction chamber (10). The first purge gas conduit (73) is inserted into the holes (60a, 61a, 62a). The first purge gas conduit (73) passes through the rectifier plate (60) and the partition plates (61, 62).

[0066] The first purge gas conduit (73) has an annular flange (74a) at the top. The first purge gas conduit (73) is detachable from the partition plate (62). The first purge gas conduit (73) supports its own weight by having the flange (74a) loaded onto the partition plate (62).

[0067] A first source gas conduit (71) is inserted into the inner side of the first purge gas conduit (73). The first purge gas conduit (73) and the first source gas conduit (71) are spaced apart. There is a gap between the first purge gas conduit (73) and the first source gas conduit (71). The gap between the first purge gas conduit (73) and the first source gas conduit (71) becomes the flow path for the purge gas PG.

[0068] FIG. 3 is an enlarged schematic cross-sectional view of a part of the gas introduction section of a gas phase growth device of the first embodiment. FIG. 3 is a cross-sectional view including a second source gas conduit (72) and a second purge gas conduit (74).

[0069] The second source gas conduit (72) supplies the second source gas (SG2) to the reaction chamber. The second source gas conduit (72) is inserted into the hole (60a) and the hole (61a). The second source gas conduit (72) passes through the rectifier plate (60) and the partition plate (61).

[0070] The second source gas conduit (72) has an annular flange (72a) at the top. The second source gas conduit (72) is detachable from the partition plate (61). The second source gas conduit (72) supports its own weight by having the flange (72a) loaded onto the partition plate (61).

[0071] The second purge gas conduit (74) supplies purge gas PG to the reaction chamber (10). The second purge gas conduit (74) is inserted into the hole (60a). The second purge gas conduit (74) passes through the rectifier plate (60).

[0072] The second purge gas conduit (74) has an annular flange (74a) at the top. The second purge gas conduit (74) is detachable from the rectifier plate (60). The second purge gas conduit (74) supports its own weight by having the flange (74a) loaded onto the rectifier plate (60).

[0073] A second source gas conduit (72) is inserted into the inner side of the second purge gas conduit (74). The second purge gas conduit (74) and the second source gas conduit (72) are spaced apart. The space between the second purge gas conduit (74) and the second source gas conduit (72) becomes a flow path for purge gas PG. The hole (60b) of the rectifier plate (60) also becomes a flow path for purge gas PG.

[0074] The first source gas conduit (71), the second source gas conduit (72), the first purge gas conduit (73), and the second purge gas conduit (74) are formed of a material with high heat resistance, for example, carbon coated with SiC. Additionally, the rectifier plate (60) and the partition plates (61, 62, 63) are formed of a material with high heat resistance, for example, carbon coated with SiC.

[0075] The control circuit (12) has the function of controlling the supply of the first source gas (SG1), the second source gas (SG2), and the purge gas PG into the reaction chamber (10).

[0076] The control circuit (12) controls the first valve V1, the second valve V2, the third valve V3, the fourth valve V4, the first mass flow controller MFC1, the second mass flow controller MFC2, the third mass flow controller MFC3, and the fourth mass flow controller MFC4. The control circuit (12) is an example of a control unit.

[0077] The control circuit (12) controls, for example, the opening and closing of the first valve V1, the opening and closing of the second valve V2, the opening and closing of the third valve V3, and the opening and closing of the fourth valve V4. The control circuit (12) transmits a command value of gas flow rate to, for example, the first mass flow controller MFC1, the second mass flow controller MFC2, the third mass flow controller MFC3, and the fourth mass flow controller MFC4.

[0078] The control circuit (12) controls the flow rate of the first source gas (SG1) by, for example, transmitting a flow rate command value of the first source gas (SG1) to the first mass flow controller MFC1. The control circuit (12) controls the flow rate of the second source gas (SG2) by, for example, transmitting a command value to the second mass flow controller MFC2. The control circuit (12) controls the flow rate of the purge gas PG by, for example, transmitting a command value to the third mass flow controller MFC3. The control circuit (12) controls the flow rate of the purge gas PG by, for example, transmitting a command value to the fourth mass flow controller MFC4.

[0079] The control circuit (12) is, for example, an electronic circuit. The control circuit (12) includes, for example, hardware and software.

[0080] The control circuit (12) includes, for example, a Central Processing Unit (CPU). The control circuit (12) includes, for example, a memory device. The memory device included in the control circuit (12) is, for example, a semiconductor memory, a Solid State Device (SSD), or a hard disk.

[0081] FIG. 4 is an explanatory diagram of control by the control circuit of a vapor phase growth device of the first embodiment. FIG. 4 is a diagram showing the time change of the flow rate of the process gas supplied to the reaction chamber (10) of the vapor phase growth device (100). The flow rate of the process gas is controlled by the control circuit (12).

[0082] When forming a SiC film on a wafer (W), the control circuit (12) controls the supply of the first source gas (SG1) and purge gas PG to the reaction chamber (10) to begin at time t0. Specifically, for example, the control circuit (12) opens the first valve V1, the third valve V3, and the fourth valve V4 by sending a command signal to the first valve V1, the third valve V3, and the fourth valve V4 at time t0, thereby starting the supply of the first source gas (SG1) and purge gas PG to the reaction chamber (10).

[0083] The control circuit (12) controls the flow rate of the first source gas (SG1) and the flow rate of the purge gas so that they become the desired flow rates. Specifically, for example, the control circuit (12) sends a command signal to the first mass flow controller MFC1, the third mass flow controller MFC3, and the fourth mass flow controller MFC4 to adjust the opening degree of the first mass flow controller MFC1, the third mass flow controller MFC3, and the fourth mass flow controller MFC4, thereby controlling the flow rate of the first source gas (SG1) and the flow rate of the purge gas PG so that they become the desired flow rates. In addition, the flow rate of the purge gas PG below is the sum of the flow rates of the purge gas PG supplied from the first purge gas supply pipe (83) and the second purge gas supply pipe (84).

[0084] The control circuit (12) controls the flow rate of the first source gas (SG1) and the flow rate of the purge gas to be constant, for example, between time t0 and time t1. The period between time t0 and time t1 is called the initial period. The initial period is an example of the first period.

[0085] The control circuit (12) controls the supply of the second source gas (SG2) to the reaction chamber (10) to begin at time t1. Specifically, for example, the control circuit (12) opens the second valve V2 by sending a command signal to the second valve V2 at time t1, thereby starting the supply of the second source gas (SG2) to the reaction chamber (10).

[0086] The control circuit (12) controls the flow rates of the first source gas (SG1) and the second source gas (SG2) to increase, for example, between time t1 and time t2. Additionally, the control circuit (12) controls the flow rate of the purge gas PG to remain constant, for example, between time t1 and time t2. The period between time t1 and time t2 is referred to as the flow rate increase period. The flow rate increase period is an example of the second period.

[0087] The period of flow increase is the period following the initial period. The period of flow increase and the initial period are continuous.

[0088] The control circuit (12) controls the flow rates of the first source gas (SG1), the second source gas (SG2), and the purge gas to become constant after time t2. The period after time t2 is referred to as the constant flow rate period.

[0089] The constant flow period is the period following the flow increase period. The constant flow period and the flow increase period are continuous.

[0090] FIG. 5 is an explanatory diagram of control by the control circuit of a vapor phase growth apparatus of the first embodiment. FIG. 5 is a diagram showing the time change of the amount of silicon (Si) per unit time and the amount of chlorine (Cl) per unit time in the process gas supplied to the reaction chamber (10) of the vapor phase growth apparatus (100). The amount of material per unit time is controlled by the control circuit (12).

[0091] The control circuit (12) has, for example, a first amount of silicon (Si) that is the amount of silicon contained in the first source gas (SG1) supplied per unit time to the reaction chamber (10) during the initial period. SG1 ), a second amount of substance (Cl) which is the amount of chlorine contained in the first source gas (SG1) supplied per unit time to the reaction chamber (10). SG1 ), a third amount of substance (Cl) which is the amount of chlorine contained in the purge gas PG supplied per unit time to the reaction chamber (10). PG Controls so that ) becomes constant.

[0092] First amount of substance (Si SG1 ) can be calculated from the flow rate of the first source gas (SG1) and the atomic concentration of silicon contained in the first source gas (SG1). In addition, the second amount of substance (Cl SG1 ) can be calculated from the flow rate of the first source gas (SG1) and the atomic concentration of chlorine contained in the first source gas (SG1). In addition, the third amount of substance (Cl PG ) can be calculated from the flow rate of purge gas PG and the atomic concentration of chlorine contained in purge gas PG.

[0093] If the atomic concentration of silicon contained in the first source gas (SG1) and the atomic concentration of chlorine contained in the first source gas (SG1) are constant, then during the initial period, if the flow rate of the first source gas (SG1) is maintained constant as shown in FIG. 4, then as shown in FIG. 5, the first amount of substance (Si SG1 ) and the second amount of substance (Cl SG1 ) becomes constant. In this case, the first amount of substance (Si SG1 The second amount of substance (Cl) for ) SG1 The ratio of ) (amount of second substance / amount of first substance) becomes constant.

[0094] For example, if the atomic concentration of chlorine contained in the purge gas PG is constant, as shown in FIG. 4, and the flow rate of the purge gas PG is maintained constant, then during the initial period, as shown in FIG. 5, a third amount of substance (ClPG ) becomes constant.

[0095] The control circuit (12) is, for example, a first amount of substance (Si during the flow rate increase period) SG1 ) and the second amount of substance (Cl SG1 ) controls to increase. In addition, the control circuit (12) controls, for example, a third amount of substance (Cl) during the flow rate increase period. PG Controls so that ) becomes constant.

[0096] If the atomic concentration of silicon contained in the first source gas (SG1) and the atomic concentration of chlorine contained in the first source gas (SG1) are constant, then during the flow rate increase period, if the flow rate of the first source gas (SG1) is increased as shown in FIG. 4, the first amount of substance (Si) as shown in FIG. 5 SG1 ) and the second amount of substance (Cl SG1 ) increases. In this case, the first amount of substance (Si SG1 The second amount of substance (Cl) for ) SG1 The ratio of ) (amount of second substance / amount of first substance) is kept constant.

[0097] For example, if the atomic concentration of chlorine contained in the purge gas PG is constant, and during the flow rate increase period, the flow rate of the purge gas PG is maintained constant as shown in Fig. 4, then the third substance amount (Cl) as shown in Fig. 5 PG ) becomes constant.

[0098] The control circuit (12) is, for example, a first amount of substance (Si during a constant flow rate period SG1 ), second amount of substance (Cl SG1 ) and third amount of substance (Cl PG Controls so that ) becomes constant.

[0099] If the atomic concentration of silicon contained in the first source gas (SG1) and the atomic concentration of chlorine contained in the first source gas (SG1) are constant, then during a constant flow rate period, if the flow rate of the first source gas (SG1) is maintained constant as shown in FIG. 4, then as shown in FIG. 5, the first amount of substance (Si SG1 ) and the second amount of substance (Cl SG1 ) becomes constant. In this case, the first amount of substance (Si SG1 The second amount of substance (Cl) for ) SG1 The ratio of ) (amount of second substance / amount of first substance) is kept constant.

[0100] For example, if the atomic concentration of chlorine contained in the purge gas PG is constant, and the flow rate of the purge gas PG is maintained constant during a constant flow rate period as shown in FIG. 4, then as shown in FIG. 5, the third amount of substance (Cl PG ) becomes constant.

[0101] FIG. 6 is an explanatory diagram of control by the control circuit of a vapor phase growth apparatus of a first embodiment. FIG. 6 shows a first amount of substance (Si SG1 The second amount of substance (Cl) for ) SG1 ) and the third amount of substance (Cl PG This is a diagram showing the time change of the ratio of the sum of ((second amount of substance + third amount of substance) / first amount of substance). (Second amount of substance + third amount of substance) / first amount of substance is controlled by a control circuit (12).

[0102] The control circuit (12) has, in the initial period, a first amount of substance (Si SG1 Regarding ), the second amount of substance (Cl SG1 ) and the third amount of substance (Cl PG Control is applied so that the ratio of the sum of ((amount of 2 substances + amount of 3 substances) / amount of 1 substance) is 30 or more. (Amount of 2 substances + amount of 3 substances) / amount of 1 substance is, (Cl SG1 +Cl PG ) / Si SG1 It can be written as.

[0103] The control circuit (12) can control the flow rate of the first source gas (SG1) and the flow rate of the purge gas PG by taking into account the atomic concentration of silicon and chlorine contained in the first source gas (SG1) and the atomic concentration of chlorine contained in the purge gas PG, thereby making (second amount of substance + third amount of substance) / first amount of substance 30 or more. (second amount of substance + third amount of substance) / first amount of substance is, for example, 30 or more and 200 or less.

[0104] By controlling the flow rates of the first source gas (SG1) and purge gas PG as shown in FIG. 4, the (second amount of substance + third amount of substance) / first amount of substance in the initial period is maintained constant as shown in FIG. 6. Additionally, by controlling the flow rates of the first source gas (SG1) and purge gas PG as shown in FIG. 4, the (second amount of substance + third amount of substance) / first amount of substance in the flow rate increase period is reduced as shown in FIG. 6. Additionally, by controlling the flow rates of the first source gas (SG1) and purge gas PG as shown in FIG. 4, the (second amount of substance + third amount of substance) / first amount of substance in the flow rate constant period is maintained constant as shown in FIG. 6.

[0105] The control circuit (12) is, for example, a first amount of substance (Si SG1 A fourth amount of substance (C), which is the amount of carbon contained in the second source gas (SG2) supplied to the reaction chamber (10) per unit time for ) SG2 The flow rates of the first source gas (SG1) and the second source gas (SG2) are controlled so that the ratio (fourth amount of substance / first amount of substance) is 1.2 or less.

[0106] Fourth amount of substance (C SG2 ) can be calculated from the flow rate of the second source gas (SG2) and the atomic concentration of carbon contained in the second source gas (SG2).

[0107] Next, a vapor phase growth method of the first embodiment is described. The vapor phase growth method of the first embodiment is a vapor phase growth method for forming a silicon carbide film on a substrate loaded in a holder provided in a reaction chamber. During a first period, a first source gas containing silicon and chlorine and a purge gas containing chlorine and hydrogen are supplied into a reaction chamber such that the ratio of the sum of the second amount of chlorine containing the first source gas supplied to the reaction chamber per unit time and the third amount of chlorine containing the purge gas supplied to the reaction chamber per unit time ((second amount of chlorine + third amount of chlorine) / first amount of chlorine) to the first amount of silicon containing the first source gas supplied to the reaction chamber per unit time is 30 or more, and during a second period after the first period, the flow rate of the first source gas supplied into the reaction chamber is increased.

[0108] The vapor phase growth method of the first embodiment uses the vapor phase growth apparatus (100) shown in FIG. 1. Below, a case in which a single-crystal SiC film (13) (silicon carbide film) is formed on the surface of a single-crystal SiC wafer (W) is described as an example.

[0109] The first source gas (SG1) contains silicon and chlorine. The second source gas (SG2) contains carbon. The purge gas PG contains chlorine and hydrogen.

[0110] Hereinafter, an example is given in which the first source gas (SG1) is a mixed gas of silane (SiH4), hydrogen chloride (HCl), and hydrogen gas (H2), the second source gas (SG2) is a mixed gas of propane (C3H8) and hydrogen gas (H2), and the purge gas PG is a mixed gas of hydrogen chloride (HCl) and hydrogen gas (H2).

[0111] The atomic concentration of silicon in the first source gas (SG1), the atomic concentration of chlorine in the first source gas (SG1), the atomic concentration of carbon in the second source gas (SG2), and the atomic concentration of chlorine in the purge gas PG are each maintained at a constant level.

[0112] First, a susceptor (14) loaded with a wafer (W) is introduced into a reaction chamber (10). The wafer (W) is single-crystal SiC.

[0113] Next, the wafer (W) is rotated at a rotational speed of 300 rpm or more by a rotary drive mechanism (20). Then, the wafer (W) is heated by a first heater (22) and a second heater (42).

[0114] Next, as shown in FIG. 4, at time t0, the supply of the first source gas (SG1) to the reaction chamber (10) is initiated. The first source gas (SG1) is introduced into the first source gas region (51) from the first source gas supply pipe (81) and supplied to the reaction chamber (10) through the first source gas conduit (71). The flow rate of the first source gas (SG1) is controlled by the control circuit (12).

[0115] Additionally, as shown in FIG. 4, at time t0, the supply of purge gas PG to the reaction chamber (10) is initiated. The purge gas PG is introduced into the first purge gas region (53) from the first purge gas supply pipe (83) and supplied to the reaction chamber (10) through the first purge gas conduit (73). Additionally, the purge gas PG is introduced into the second purge gas region (54) from the second purge gas supply pipe (84) and supplied to the reaction chamber (10) through the second purge gas conduit (74) and the hole (60b) of the rectifier plate (60). The flow rate of the purge gas PG is controlled by the control circuit (12).

[0116] As shown in FIG. 4, during the initial period between time t0 and time t1, for example, the flow rate of the first source gas (SG1) is kept constant. Also, during the initial period, for example, the flow rate of the purge gas PG is kept constant.

[0117] As shown in FIG. 5, during the initial period, for example, a first amount of substance (Si SG1 ) and the second amount of substance (ClSG1 ) is made to remain constant. In addition, as shown in FIG. 5, during the initial period, for example, a third amount of substance (Cl PG Make ) constant.

[0118] In addition, as shown in FIG. 6, during the initial period, a first amount of substance (Si SG1 Regarding ), the second amount of substance (Cl SG1 ) and the third amount of substance (Cl PG A first source gas (SG1) and a purge gas PG are supplied to the reaction chamber (10) so that the ratio of the sum of ((amount of second substance + amount of third substance) / amount of first substance) is 30 or more. During the initial period, (amount of second substance + amount of third substance) / amount of first substance is, for example, constant.

[0119] Additionally, during the initial period, since the second source gas (SG2), which is the source gas of carbon (C), is not supplied to the reaction chamber (10), the SiC film (13) is not formed on the surface of the wafer (W).

[0120] Next, as shown in FIG. 4, at time t1, the supply of the second source gas (SG2) to the reaction chamber (10) is initiated. The second source gas (SG2) is introduced into the second source gas region (52) from the second source gas supply pipe (82) and supplied to the reaction chamber (10) through the second source gas conduit (72). The flow rate of the second source gas (SG2) is controlled by the control circuit (12).

[0121] The first source gas (SG1), the second source gas (SG2), and the purge gas PG supplied from the gas introduction section (11) to the reaction chamber (10) become a gas flow directed toward the surface of the wafer (W). As the silicon atoms contained in the first source gas (SG1) and the carbon atoms contained in the second source gas (SG2) react at the surface of the wafer (W), a single-crystal SiC film (13) is formed on the surface of the wafer (W).

[0122] As shown in FIG. 4, during the flow rate increase period after the initial period, the flow rate of the first source gas (SG1) and the flow rate of the second source gas (SG2) are increased. Also, as shown in FIG. 4, during the initial period and the flow rate increase period, the flow rate of the purge gas PG is maintained at a constant level.

[0123] As shown in FIG. 5, during the flow rate increase period, the first amount of substance (Si SG1 ) and the second amount of substance (Cl SG1 ) increases. Also, as shown in FIG. 5, for example, during the initial period and the flow rate increase period, the third amount of substance (Cl PG ) is maintained at a constant level.

[0124] In the initial period and the flow rate increase period, for example, the first amount of substance (Si SG1 The second amount of substance (Cl) for ) SG1 The ratio of ) (amount of second substance / amount of first substance) is kept constant.

[0125] As shown in FIG. 4, during the constant flow rate period after the flow rate increase period, the flow rate of the first source gas (SG1), the flow rate of the second source gas (SG2), and the flow rate of the purge gas PG are maintained at a constant level.

[0126] In the period of increasing flow rate and the period of constant flow rate, for example, a first amount of substance (Si SG1 The fourth amount of substance (C) for ) SG2 The ratio of ) (amount of the fourth substance / amount of the first substance) is 0.1 or more and 1.2 or less.

[0127] After forming the SiC film (13), heating by the first heater (22) and the second heater (42) is stopped to lower the temperature of the wafer (W). Then, the wafer (W) is removed from the reaction chamber (10) together with the susceptor (14).

[0128] Next, the operation and effects of the vapor growth apparatus and vapor growth method of the first embodiment will be explained.

[0129] When forming a SiC film on the surface of a wafer using a vapor phase growth device, defects such as pits or bumps may occur on the surface of the SiC film. The presence of defects on the surface of the SiC film is problematic because, for example, it degrades the characteristics of the semiconductor device formed on the SiC film.

[0130] In the first embodiment, when forming a SiC film on the surface of a wafer, the control circuit (12) controls the supply of a first source gas containing silicon and chlorine and a purge gas containing chlorine and hydrogen to a reaction chamber (10). The control circuit (12) controls, for example, the flow rate of the first source gas and the flow rate of the purge gas.

[0131] The control circuit (12) controls the ratio ((second amount of substance + third amount of substance) / first amount of substance) of the sum of the second amount of substance

[0132] The control circuit (12) additionally controls the flow rate of the first source gas (SG1) so that the flow rate of the first source gas (SG1) increases during the flow rate increase period after the initial period.

[0133] According to the vapor phase growth apparatus (100) of the first embodiment, when forming a SiC film on the surface of a wafer by the above configuration, the occurrence of defects such as pits or bumps on the surface of the SiC film is suppressed.

[0134] In addition, the vapor phase growth method of the first embodiment supplies a first source gas (SG1) containing silicon and chlorine and a purge gas PG containing chlorine and hydrogen into the reaction chamber (10) during the initial period when forming a SiC film on the surface of a wafer, such that the ratio of the sum of the second amount of chlorine contained in the first source gas (SG1) supplied to the reaction chamber (10) per unit time and the third amount of chlorine contained in the purge gas PG supplied to the reaction chamber (10) per unit time ((second amount of chlorine + third amount of chlorine) / first amount of chlorine) to the first amount of silicon contained in the first source gas (SG1) supplied to the reaction chamber (10) per unit time (first amount of chlorine) is 30 or more. In addition, during the flow rate increase period after the initial period, the flow rate of the first source gas (SG1) supplied into the reaction chamber (10) is increased.

[0135] According to the vapor phase growth method of the first embodiment, when forming a SiC film on the surface of a wafer by the above configuration, the occurrence of defects such as pits or bumps on the surface of the SiC film is suppressed.

[0136] FIGS. 7a and 7b are explanatory diagrams of the operation and effects of the first embodiment. FIGS. 7a and 7b are confocal differential interference microscope images of the surface of a SiC film. FIG. 7a is a SiC film produced by the vapor phase growth method of a comparative example, and FIG. 7b is a SiC film produced by the vapor phase growth method of an embodiment.

[0137] In the vapor phase growth method of the comparative example, (amount of second substance + amount of third substance) / amount of first substance during the initial period, i.e., (Cl SG1 +Cl PG ) / Si SG1 ...is 24.5. Also, in the comparative example, the ratio of the amount of the fourth substance to the amount of the first substance (amount of the fourth substance / amount of the first substance), i.e., C, during the period of increasing the flow rate and the period of constant flow rate. SG2 / Si SG1 It is 0.95.

[0138] Meanwhile, in the vapor phase growth method of the embodiment, (amount of second substance + amount of third substance) / amount of first substance, i.e., (Cl SG1 +Cl PG ) / Si SG1 ...is 32.75. In addition, in the vapor phase growth method of the embodiment, the ratio of the fourth amount of substance to the first amount of substance (fourth amount of substance / first amount of substance), i.e., C, during the flow rate increase period and the flow rate constant period. SG2 / Si SG1 The value is 0.95. In the vapor phase growth method of the embodiment, the second amount of chlorine contained in the first source gas (SG1) for the embodiment is increased to about 1.8 times that of the embodiment, thereby increasing (second amount of chlorine + third amount of chlorine) / first amount of chlorine during the initial period.

[0139] As shown in FIG. 7a, in the comparative example, the occurrence of defects such as pits or bumps on the surface of the SiC film is observed. On the other hand, as shown in FIG. 7b, in the embodiment, the occurrence of defects such as pits or bumps on the surface of the SiC film is suppressed.

[0140] FIG. 8 is an explanatory diagram of the operation and effects of a vapor phase growth apparatus and a vapor phase growth method according to a first embodiment. FIG. 8 is a diagram showing the relationship between the number of defects on the surface of a SiC film and the ratio of the sum of the second and third amounts of substance to the first amount of substance during the initial period ((second amount of substance + third amount of substance) / first amount of substance). FIG. 8 shows the number of defects on the surface of a SiC film when only the ratio of the sum of the second and third amounts of substance to the first amount of substance ((second amount of substance + third amount of substance) / first amount of substance) is changed using a vapor phase growth method similar to the vapor phase growth method of the first embodiment.

[0141] As shown in FIG. 8, (amount of second substance + amount of third substance) / amount of first substance, i.e., (Cl SG1 +ClPG ) / Si SG1 When this is 30 or more, the number of defects on the surface of the SiC film is reduced. (2nd amount of substance + 3rd amount of substance) / 1st amount of substance is, for example, 200 or less.

[0142] It is believed that in the early stages of forming the SiC film, the ratio of chlorine to silicon supplied to the reaction chamber (10) is increased, thereby suppressing the generation of silicon-containing particles in the reaction chamber (10).

[0143] In terms of reducing the number of defects on the surface of the SiC film, (amount of second substance + amount of third substance) / amount of first substance is preferably 35 or more, and more preferably 40 or more.

[0144] In terms of stably forming a SiC film, it is preferable to start supplying a second source gas (SG2) containing carbon into the reaction chamber (10) after an initial period.

[0145] From the perspective of stably forming a SiC film, in the initial period, the flow rate increase period, and the flow rate constant period, a first amount of substance (Si SG1 The second amount of substance (Cl) for ) SG1 It is desirable that the ratio (amount of the second substance / amount of the first substance) of ) is constant.

[0146] From the perspective of stably forming a SiC film, in the initial period, the flow rate increase period, and the flow rate constant period, a third amount of substance (Cl PG It is desirable for ) to be constant.

[0147] First amount of substance (Si SG1 The fourth amount of substance (C) for ) SG2 The ratio of ) (amount of 4 substance / amount of 1 substance), i.e., C SG2 / Si SG1 Silver is adjusted to make the characteristics of the SiC film being formed the desired characteristics. For example, C SG2 / Si SG1 By adjusting it, the uniformity of carrier concentration in the SiC film or the film formation rate can be adjusted.

[0148] In terms of stably forming a SiC film, at the time when supplying the second source gas (SG2) to the reaction chamber (10) begins, the fourth amount of carbon (C) contained in the second source gas (SG2) supplied to the reaction chamber (10) per unit time SG2 ) is C during the time of the Tabernacle SG2 / Si SG1 It is desirable to fix it at a predetermined amount of substance without relying on it.

[0149] The fourth amount of carbon (C) contained in the second source gas (SG2). SG2 ) to C SG2 / Si SG1 In the case of fixing to a predetermined amount of substance without relying on, C SG2 / Si SG1 If this small tabernacle condition is selected, the first amount of substance (Si SG1 ) increases. The first amount of substance (Si SG1 If ) increases, (amount of second substance + amount of third substance) / amount of first substance decreases. For this reason, it is desired to adjust (amount of second substance + amount of third substance) / amount of first substance to be 30 or more by increasing at least one of the amount of second substance or amount of third substance.

[0150] For example, the fourth amount of substance / the first amount of substance, i.e., C SG2 / Si SG1 In the case where this becomes 1.2 or less, in order to make (amount of second substance + amount of third substance) / amount of first substance 30 or more, the amount of second substance (Cl SG1 ) or a third amount of substance (Cl PG It is desirable to increase at least one of the following.

[0151] FIGS. 9, 10, and 11 are explanatory diagrams of a vapor phase growth apparatus and a vapor phase growth method according to a first embodiment. For example, in order to make (amount of second substance + amount of third substance) / amount of first substance in the initial state 30 or more, as shown in FIG. 9, the amount of second substance (Cl SG1It does not matter if only ) is increased. In addition, for example, in order to make (amount of second substance + amount of third substance) / amount of first substance in the initial state 30 or more, as shown in FIG. 10, the amount of third substance (Cl PG It does not matter if only ) is increased. In addition, for example, in order to make (amount of second substance + amount of third substance) / amount of first substance in the initial state 30 or more, as shown in FIG. 11, the amount of second substance (Cl SG1 ) and third amount of substance (Cl PG It doesn't matter if you increase both sides of ).

[0152] According to the first embodiment, a vapor phase growth apparatus and a vapor phase growth method capable of reducing defects in the film can be realized.

[0153] (Second embodiment)

[0154] The vapor phase growth apparatus of the second embodiment differs from the vapor phase growth apparatus of the first embodiment in that it is equipped with a mixed source gas flow path that supplies a mixed source gas containing silicon, carbon, and chlorine into a reaction chamber. Additionally, the vapor phase growth method of the second embodiment differs from the vapor phase growth method of the first embodiment in that it supplies a mixed source gas containing silicon, carbon, and chlorine into a reaction chamber. Hereinafter, regarding content that overlaps with the first embodiment, some technical details may be omitted.

[0155] FIG. 12 is a schematic cross-sectional view of a vapor phase growth apparatus of a second embodiment. The vapor phase growth apparatus (200) of the second embodiment is a single-wafer type epitaxial growth apparatus for epitaxially growing a single-crystal SiC film on, for example, a single-crystal SiC substrate. The vapor phase growth apparatus (200) of the second embodiment is a vertical type vapor phase growth apparatus in which a process gas is supplied in a longitudinal direction to the surface of a SiC substrate.

[0156] A gas growth device (200) of a second embodiment comprises a reaction chamber (10), a gas introduction section (11), and a control circuit (12) (control section). The reaction chamber (10) includes a susceptor (14) (holder), a rotating body (16), a rotating shaft (18), a rotary driving mechanism (20), a first heater (22), a reflector (28), a support column (30), a fixing stand (32), a fixing shaft (34), a hood (40), a second heater (42), and a gas outlet (44). The gas introduction section (11) includes a mixed source gas area (55), a rectifier plate (60), a ceiling plate (64), and a purge gas conduit (75). The rectifier plate (60) includes a gas hole (60x).

[0157] The vapor growth device (200) of the second embodiment includes a mixed source gas supply pipe (86), a purge gas supply pipe (87), a first mass flow controller MFC1, a second mass flow controller MFC2, a first valve V1, and a second valve V2.

[0158] The mixed source gas supply pipe (86), the mixed source gas region (55), and the gas hole (60x) form a source gas flow path. The source gas flow path supplies the mixed source gas (SGx) to the reaction chamber (10).

[0159] The purge gas supply pipe (87) and the purge gas conduit (75) form a purge gas flow path. The purge gas flow path supplies purge gas PG to the reaction chamber (10).

[0160] A first valve V1 and a first mass flow controller MFC1 are provided in the mixed source gas supply pipe (86). The first valve V1 has the function of switching the introduction of the mixed source gas (SGx) introduced into the mixed source gas supply pipe (86) to start and stop the introduction. The first mass flow controller MFC1 has the function of adjusting the flow rate of the mixed source gas (SGx) introduced into the mixed source gas supply pipe (86) to a predetermined amount.

[0161] The second valve V2 and the second mass flow controller MFC2 are provided in the purge gas supply pipe (87). The second valve V2 has the function of switching the introduction of purge gas PG introduced into the purge gas supply pipe (87) to start and stop the introduction. The second mass flow controller MFC2 has the function of adjusting the flow rate of purge gas PG introduced into the purge gas supply pipe (87) to a predetermined amount.

[0162] The first valve V1, the second valve V2, the first mass flow controller MFC1, and the second mass flow controller MFC2 are controlled by the control circuit (12).

[0163] The gas introduction section (11) is provided on the reaction chamber (10).

[0164] In the mixed source gas area (55), mixed source gas (SGx) is introduced from the mixed source gas supply pipe (86). The mixed source gas area (55) is provided between the rectifier plate (60) and the ceiling plate (64).

[0165] A rectifier plate (60) is provided between the reaction chamber (10) and the mixed source gas region (55). The rectifier plate (60) has a plurality of gas holes (60x).

[0166] The ceiling plate (64) is placed on the mixed source gas area (55).

[0167] The mixed source gas (SGx) is a source gas of silicon (Si) and carbon (C). The mixed source gas (SGx) contains silicon (Si), carbon (C), and chlorine (Cl). The mixed source gas (SGx) is, for example, silane (SiH4) or chlorosilane (SiH4). 4-n Cl n: n=1 to 4) is included. The mixed source gas (SGx) includes, for example, hydrocarbons. The mixed source gas (SGx) includes, for example, hydrogen chloride (HCl). The mixed source gas (SGx) includes, for example, hydrogen gas (H2). The mixed source gas (SGx) is, for example, a mixed gas of silane (SiH4), propane (C3H8), hydrogen chloride (HCl), and hydrogen gas (H2).

[0168] The mixed source gas (SGx) contains, for example, a dopant gas of n-type impurities. The dopant gas of n-type impurities is, for example, nitrogen gas.

[0169] The purge gas PG has the function of adjusting the distribution of the mixed source gas (SGx) supplied to the reaction chamber (10), for example, on the wafer (W).

[0170] The purge gas PG contains chlorine (Cl) and hydrogen (H). The purge gas PG contains, for example, hydrogen chloride (HCl). The purge gas PG contains, for example, hydrogen gas (H2). The purge gas PG is a mixed gas of, for example, hydrogen chloride (HCl) and hydrogen gas (H2). It is also possible to use, for example, argon gas (Ar) instead of hydrogen gas (H2).

[0171] The atomic concentration of chlorine in the purge gas PG is lower than, for example, the atomic concentration of chlorine in the mixed source gas (SGx). The atomic concentration of chlorine in the purge gas PG is, for example, one-fifth or less of the atomic concentration of chlorine in the mixed source gas (SGx).

[0172] The control circuit (12) controls the first valve V1, the second valve V2, the first mass flow controller MFC1, and the second mass flow controller MFC2. The control circuit (12) is an example of a control unit.

[0173] The control circuit (12) controls, for example, the opening and closing of the first valve V1 and the opening and closing of the second valve V2. The control circuit (12) transmits a command value for the gas flow rate to, for example, the first mass flow controller MFC1 and the second mass flow controller MFC2.

[0174] The control circuit (12) controls the flow rate of the mixed source gas (SGx) by, for example, transmitting a command value for the flow rate of the mixed source gas (SGx) to the first mass flow controller MFC1. The control circuit (12) controls the flow rate of the purge gas PG by, for example, transmitting a command value to the second mass flow controller MFC2.

[0175] FIG. 13 is an explanatory diagram of control by the control circuit of a vapor growth device of a second embodiment. FIG. 13 is a diagram showing the time change of the flow rate of the process gas supplied to the reaction chamber (10) of the vapor growth device (200). The flow rate of the process gas is controlled by the control circuit (12).

[0176] When forming a SiC film on a wafer (W), the control circuit (12) controls the supply of the mixed source gas (SGx) and purge gas PG to the reaction chamber (10) to begin at time t0. Specifically, for example, the control circuit (12) opens the first valve V1 and the second valve V2 by sending a command signal to the first valve V1 and the second valve V2 at time t0, thereby starting the supply of the mixed source gas (SGx) and purge gas PG to the reaction chamber (10).

[0177] The control circuit (12) controls the flow rate of the mixed source gas (SGx) and the flow rate of the purge gas PG so that they become the desired flow rates. Specifically, for example, the control circuit (12) sends a command signal to the first mass flow controller MFC1 and the second mass flow controller MFC2 to adjust the opening degree of the first mass flow controller MFC1 and the second mass flow controller MFC2, thereby controlling the flow rate of the mixed source gas (SGx) and the flow rate of the purge gas PG so that they become the desired flow rates.

[0178] The control circuit (12) controls the flow rate of the mixed source gas (SGx) and the flow rate of the purge gas to be constant, for example, between time t0 and time t1. The period between time t0 and time t1 is called the initial period. The initial period is an example of the first period.

[0179] The control circuit (12) controls the flow rate of the mixed source gas (SGx) to increase, for example, between time t1 and time t2. Additionally, the control circuit (12) controls the flow rate of the purge gas PG to remain constant, for example, between time t1 and time t2. The period between time t1 and time t2 is referred to as the flow rate increase period. The flow rate increase period is an example of the second period.

[0180] The period of flow increase is the period following the initial period. The period of flow increase and the initial period are continuous.

[0181] The control circuit (12) controls the flow rate of the mixed source gas (SGx) and the flow rate of the purge gas to become constant after time t2. The period after time t2 is referred to as the constant flow rate period.

[0182] The constant flow period is the period following the flow increase period. The constant flow period and the flow increase period are continuous.

[0183] FIG. 14 is an explanatory diagram of control by the control circuit of a vapor phase growth apparatus of a second embodiment. FIG. 14 is a diagram showing the time change of the amount of silicon (Si) per unit time and the amount of chlorine (Cl) per unit time among the process gases supplied to the reaction chamber (10) of the vapor phase growth apparatus (200). The amount of material per unit time is controlled by the control circuit (12).

[0184] The control circuit (12) is, for example, a first amount of silicon (Si) that is the amount of silicon contained in the mixed source gas (SGx) supplied per unit time to the reaction chamber (10) during the initial period. SGx ), a second amount of substance (Cl) which is the amount of chlorine contained in the mixed source gas (SGx) supplied per unit time to the reaction chamber (10). SGx ), a third amount of substance (Cl) which is the amount of chlorine contained in the purge gas PG supplied per unit time to the reaction chamber (10). PG Controls so that ) becomes constant.

[0185] If the atomic concentration of silicon contained in the mixed source gas (SGx) and the atomic concentration of chlorine contained in the mixed source gas (SGx) are constant, then during the initial period, if the flow rate of the mixed source gas (SGx) is maintained constant as shown in FIG. 13, then as shown in FIG. 14, the first amount of substance (Si SGx ) and the second amount of substance (Cl SGx ) becomes constant. In this case, the first amount of substance (Si SGx The second amount of substance (Cl) for ) SGx The ratio of ) (amount of second substance / amount of first substance) becomes constant.

[0186] For example, if the atomic concentration of chlorine contained in the purge gas PG is constant, and the flow rate of the purge gas PG is maintained constant during the initial period as shown in FIG. 13, then a third substance amount (Cl) as shown in FIG. 14 PG ) becomes constant.

[0187] The control circuit (12) is, for example, a first amount of substance (Si during the flow rate increase period) SGx ) and the second amount of substance (Cl SGx ) controls to increase. In addition, the control circuit (12) controls, for example, a third amount of substance (Cl) during the flow rate increase period. PG Controls so that ) becomes constant.

[0188] If the atomic concentration of silicon contained in the mixed source gas (SGx) and the atomic concentration of chlorine contained in the mixed source gas (SGx) are constant, then during the flow rate increase period, if the flow rate of the mixed source gas (SGx) is increased as shown in FIG. 13, then as shown in FIG. 14, the first amount of substance (Si SGx ) and the second amount of substance (Cl SGx ) increases. In this case, the first amount of substance (Si SGx The second amount of substance (Cl) for ) SGx The ratio of ) (amount of second substance / amount of first substance) is kept constant.

[0189] For example, if the atomic concentration of chlorine contained in the purge gas PG is constant, then during the flow rate increase period, if the flow rate of the purge gas PG is maintained constant as shown in FIG. 13, then as shown in FIG. 14, the third substance amount (Cl PG ) becomes constant.

[0190] The control circuit (12) is, for example, a first amount of substance (Si during a constant flow rate period SGx ), second amount of substance (Cl SGx ) and third amount of substance (Cl PG Controls so that ) becomes constant.

[0191] If the atomic concentration of silicon contained in the mixed source gas (SGx) and the atomic concentration of chlorine contained in the mixed source gas (SGx) are constant, then during a constant flow rate period, if the flow rate of the mixed source gas (SGx) is maintained constant as shown in FIG. 13, then as shown in FIG. 14, the first amount of substance (Si SGx) and the second amount of substance (Cl SGx ) becomes constant. In this case, the first amount of substance (Si SGx The second amount of substance (Cl) for ) SGx The ratio of ) (amount of second substance / amount of first substance) is kept constant.

[0192] For example, if the atomic concentration of chlorine contained in the purge gas PG is constant, then during a constant flow rate period, if the flow rate of the purge gas PG is maintained constant as shown in FIG. 13, then as shown in FIG. 14, a third amount of substance (Cl PG ) becomes constant.

[0193] FIG. 15 is an explanatory diagram of control by the control circuit of a vapor phase growth apparatus of a second embodiment. FIG. 15 shows a first amount of process gas (Si) supplied to the reaction chamber (10) of the vapor phase growth apparatus (200). SGx The second amount of substance (Cl) for ) SGx ) and the third amount of substance (Cl PG This is a diagram showing the time change of the ratio of the sum of ((second amount of substance + third amount of substance) / first amount of substance). (Second amount of substance + third amount of substance) / first amount of substance is controlled by a control circuit (12).

[0194] The control circuit (12) has, in the initial period, a first amount of substance (Si SGx Regarding ), the second amount of substance (Cl SGx ) and the third amount of substance (Cl PG Control is applied so that the ratio of the sum of ((amount of 2 substances + amount of 3 substances) / amount of 1 substance) is 30 or more. (Amount of 2 substances + amount of 3 substances) / amount of 1 substance is (Cl SGx +Cl PG ) / Si SGx It can be written as.

[0195] The control circuit (12) can control the flow rate of the mixed source gas (SGx) and the flow rate of the purge gas PG by taking into account the atomic concentration of silicon and chlorine contained in the mixed source gas (SGx) and the atomic concentration of chlorine contained in the purge gas PG, thereby making (second amount of substance + third amount of substance) / first amount of substance 30 or more. (second amount of substance + third amount of substance) / first amount of substance is, for example, 30 or more and 200 or less.

[0196] By controlling the flow rates of the mixed source gas (SGx) and purge gas PG as shown in FIG. 13, the (second amount of substance + third amount of substance) / first amount of substance is maintained constant during the initial period. Additionally, by controlling the flow rates of the mixed source gas (SGx) and purge gas PG as shown in FIG. 13, the (second amount of substance + third amount of substance) / first amount of substance is reduced during the flow rate increase period. Additionally, by controlling the flow rates of the first source gas (SG1) and purge gas PG as shown in FIG. 13, the (second amount of substance + third amount of substance) / first amount of substance is maintained constant during the flow rate constant period.

[0197] The control circuit (12) is, for example, a fourth amount of substance (C) which is the amount of carbon contained in the mixed source gas (SGx) supplied per unit time to the reaction chamber (10) for a first amount of substance. SG2 The ratio (fourth amount of substance / first amount of substance) is controlled to be 1.2 or less. The control circuit (12) controls, for example, the flow rate of the silicon source gas and the flow rate of the carbon source gas before mixing using a mass flow controller not shown.

[0198] Next, a vapor growth method of the second embodiment will be described.

[0199] The vapor phase growth method of the second embodiment uses the vapor phase growth apparatus (200) shown in FIG. 12. It is explained by taking the example of forming a single-crystal SiC film (13) (silicon carbide film) on the surface of a single-crystal SiC wafer (W).

[0200] The mixed source gas (SGx) contains silicon, carbon, and chlorine. The purge gas PG contains chlorine and hydrogen.

[0201] Hereinafter, an example is given in which the mixed source gas (SGx) is a mixed gas of silane (SiH4), propane (C3H8), hydrogen chloride (HCl), and hydrogen gas (H2), and the purge gas PG is a mixed gas of hydrogen chloride (HCl) and hydrogen gas (H2).

[0202] The atomic concentration of silicon in the mixed source gas (SGx), the atomic concentration of carbon in the mixed source gas (SGx), the atomic concentration of chlorine in the mixed source gas (SGx), and the atomic concentration of chlorine in the purge gas PG are each kept constant.

[0203] First, a susceptor (14) loaded with a wafer (W) is introduced into a reaction chamber (10). The wafer (W) is single-crystal SiC.

[0204] Next, the wafer (W) is rotated at a rotational speed of 300 rpm or more by a rotary drive mechanism (20). Then, the wafer (W) is heated by a first heater (22) and a second heater (42).

[0205] Next, as shown in FIG. 13, at time t0, the supply of the mixed source gas (SGx) to the reaction chamber (10) is initiated. The mixed source gas (SGx) is introduced into the mixed source gas region (55) from the mixed source gas supply pipe (86) and supplied to the reaction chamber (10) through the gas hole (60x) of the rectifier plate (60). The flow rate of the mixed source gas (SGx) is controlled by the control circuit (12).

[0206] Additionally, as shown in FIG. 13, at time t0, the supply of purge gas PG to the reaction chamber (10) is initiated. The purge gas PG is supplied from the purge gas supply pipe (87) to the reaction chamber (10) through the purge gas conduit (75). The flow rate of the purge gas PG is controlled by the control circuit (12).

[0207] As shown in FIG. 13, during the initial period between time t0 and time t1, for example, the flow rate of the mixed source gas (SGx) is kept constant. Also, during the initial period, for example, the flow rate of the purge gas PG is kept constant.

[0208] As shown in FIG. 14, during the initial period, for example, a first amount of substance (Si SGx ) and the second amount of substance (Cl SGx ) is made to remain constant. In addition, as shown in FIG. 14, during the initial period, for example, a third amount of substance (Cl PG Make ) constant.

[0209] In addition, as shown in FIG. 15, during the initial period, a first amount of substance (Si SGx Regarding ), the second amount of substance (Cl SGx ) and the third amount of substance (Cl PG Mixed source gas (SGx) and purge gas PG are supplied to the reaction chamber (10) so that the ratio of the sum of ((amount of second substance + amount of third substance) / amount of first substance) is 30 or more. During the initial period, (amount of second substance + amount of third substance) / amount of first substance is, for example, constant.

[0210] The mixed source gas (SGx) and purge gas PG supplied from the gas introduction section (11) to the reaction chamber (10) become a gas flow directed toward the surface of the wafer (W). As the silicon atoms and carbon atoms contained in the mixed source gas (SGx) react at the surface of the wafer (W), a single-crystal SiC film (13) is formed on the surface of the wafer (W).

[0211] As shown in FIG. 13, during the flow rate increase period following the initial period, the flow rate of the mixed source gas (SGx) is increased. Also, as shown in FIG. 13, during the initial period and the flow rate increase period, for example, the flow rate of the purge gas PG is maintained constant.

[0212] As shown in FIG. 14, during the flow rate increase period, the first amount of substance (Si SGx ) and the second amount of substance (Cl SGx ) increases. Also, as shown in FIG. 14, for example, during the initial period and the flow rate increase period, the third amount of substance (Cl PG ) is maintained at a constant level.

[0213] In the initial period and the flow rate increase period, for example, the first amount of substance (Si SGx The second amount of substance (Cl) for ) SGx The ratio of ) (amount of second substance / amount of first substance) is kept constant.

[0214] As shown in Fig. 13, during the constant flow rate period after the flow rate increase period, the flow rate of the mixed source gas (SGx) and the flow rate of the purge gas PG are maintained at a constant level.

[0215] In the period of increasing flow rate and the period of constant flow rate, for example, a first amount of substance (Si SGx The ratio of the amount of the fourth substance to ) (amount of the fourth substance / amount of the first substance) is 0.1 or more and 1.2 or less.

[0216] After forming the SiC film (13), heating by the first heater (22) and the second heater (42) is stopped to lower the temperature of the wafer (W). Then, the wafer (W) is removed from the reaction chamber (10) together with the susceptor (14).

[0217] According to the vapor phase growth apparatus and vapor phase growth method of the second embodiment, during the initial period, the ratio of the sum of the second amount of chlorine contained in the mixed source gas (SGx) supplied to the reaction chamber (10) per unit time and the third amount of chlorine contained in the purge gas PG supplied to the reaction chamber (10) per unit time to the first amount of silicon contained in the mixed source gas (SGx) supplied to the reaction chamber (10) per unit time ((second amount of chlorine + third amount of chlorine) / first amount of chlorine) is controlled to be 30 or more. Accordingly, as in the first embodiment, when forming a SiC film on the surface of a wafer, the occurrence of defects such as pits or bumps on the surface of the SiC film is suppressed.

[0218] According to the second embodiment, a vapor phase growth apparatus and a vapor phase growth method capable of reducing defects in the film can be realized.

[0219] Embodiments of the present invention have been described above with reference to specific examples. The above embodiments are merely illustrative examples and do not limit the present invention. Furthermore, the components of each embodiment may be appropriately combined.

[0220] In the first and second embodiments, 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.

[0221] In addition, in the first and second 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.

[0222] In addition, in the first and second embodiments, nitrogen was described as an example of an n-type impurity, but it is also possible to apply, for example, phosphorus (P) as an n-type impurity. Furthermore, it is also possible to apply p-type impurities as impurities.

[0223] In addition, in the first and second embodiments, a single-wafer type epitaxial growth apparatus for forming a film on one wafer was described as an example, but the present invention can also be applied to a batch type epitaxial growth apparatus for forming films on multiple wafers simultaneously.

[0224] In addition, in the first embodiment, the case where the atomic concentration of silicon in the first source gas (SG1), the atomic concentration of chlorine in the first source gas (SG1), the atomic concentration of carbon in the second source gas (SG2), and the atomic concentration of chlorine in the purge gas PG are constant was described as an example, but it is also possible to change the atomic concentration of silicon in the first source gas (SG1), the atomic concentration of chlorine in the first source gas (SG1), the atomic concentration of carbon in the second source gas (SG2), or the atomic concentration of chlorine in the purge gas PG.

[0225] In addition, in the second embodiment, although the case where the atomic concentration of silicon in the mixed source gas (SGx), the atomic concentration of carbon in the mixed source gas (SGx), the atomic concentration of chlorine in the mixed source gas (SGx), and the atomic concentration of chlorine in the purge gas PG are constant was described as an example, it is also possible to change the atomic concentration of silicon in the mixed source gas (SGx), the atomic concentration of carbon in the mixed source gas (SGx), the atomic concentration of chlorine in the mixed source gas (SGx), or the atomic concentration of chlorine in the purge gas PG.

[0226] In addition, in the first embodiment, the case where the second source gas (SG2) is not supplied to the reaction chamber (10) during the initial period was described as an example, but it is also possible to supply the second source gas (SG2) to the reaction chamber (10) during the initial period.

[0227] In addition, in the second embodiment, although the case in which a carbon source gas is supplied to the reaction chamber (10) during the initial period was described as an example, it is also possible not to supply a carbon source gas to the reaction chamber (10) during the initial period.

[0228] In the first and second embodiments, descriptions of parts that are not directly necessary for the description of the present invention, such as device configurations or manufacturing methods, have been omitted, but necessary device configurations or manufacturing methods may be appropriately selected and used. Furthermore, any vapor phase growth device having elements of the present invention and capable of being appropriately modified by a person skilled in the art is included within the scope of the present invention. The scope of the present invention is defined by the scope of the claims and their equivalents. Explanation of the symbols

[0229] 10: Reaction chamber 11: Gas inlet 12: Control circuit (control unit) 13: SiC film (silicon carbide film) 14: Susceptor (Holder) 100: Vapor growth device 200: Weather growth device SG1: First Source Gas SG2: Second Source Gas SGx: Mixed source gas PG: Purge gas W: Wafer (substrate)

Claims

Claim 1 A vapor phase growth apparatus comprising: a reaction chamber; a holder provided in the reaction chamber for loading a substrate; a source gas path for supplying a first source gas containing silicon and chlorine into the reaction chamber; a purge gas path for supplying a purge gas containing chlorine and hydrogen into the reaction chamber; and a control unit for controlling the supply of the first source gas and the purge gas into the reaction chamber, wherein the control unit controls the ratio ((second amount of substance + third amount of substance) / first amount of substance) of the sum of the first amount of substance containing chlorine in the first source gas supplied to the reaction chamber per unit time and the first amount of substance containing chlorine in the purge gas supplied to the reaction chamber per unit time, to a first amount of substance containing silicon in the first source gas supplied to the reaction chamber per unit time during the initial film formation period, such that the ratio is 30 or more; and wherein the control unit controls the flow rate of the first source gas to increase during the flow rate increase period after the initial film formation period. Claim 2 A vapor phase growth apparatus according to claim 1, wherein the control unit further controls the supply of a second source gas containing carbon into the reaction chamber, and the control unit controls the supply of the second source gas into the reaction chamber after the initial film formation period. Claim 3 A gas phase growth apparatus according to paragraph 2, wherein the control unit controls the ratio of the fourth amount of substance (fourth amount of substance / first amount of substance), which is the amount of carbon contained in the second source gas supplied to the reaction chamber per unit time relative to the first amount of substance, to be 1.2 or less. Claim 4 A vapor phase growth apparatus according to claim 1, wherein the control unit controls the ratio of the second amount of substance to the first amount of substance (second amount of substance / first amount of substance) to be constant during the initial film formation period and the flow rate increase period. Claim 5 A vapor phase growth device according to claim 1, wherein the control unit controls the amount of the third substance to be constant during the initial film formation period and the flow rate increase period. Claim 6 A vapor phase growth method for forming a silicon carbide film on a substrate loaded in a holder provided in a reaction chamber, wherein during the initial film formation period, a first source gas containing silicon and chlorine and a purge gas containing chlorine and hydrogen are supplied into the reaction chamber such that the ratio of the sum of the first amount of chlorine contained in the first source gas supplied to the reaction chamber per unit time and the second amount of chlorine contained in the purge gas supplied to the reaction chamber per unit time ((second amount of chlorine + third amount of chlorine) / first amount of chlorine) to the first amount of silicon contained in the first source gas supplied to the reaction chamber per unit time is 30 or more, and during the flow rate increase period after the initial film formation period, the flow rate of the first source gas supplied into the reaction chamber is increased. Claim 7 A gas phase growth method according to claim 6, wherein, after the initial period of the above-mentioned film formation, a second source gas containing carbon is supplied into the reaction chamber. Claim 8 A gas phase growth method according to claim 7, wherein the ratio of a fourth amount of substance (fourth amount of substance / first amount of substance), which is the amount of carbon contained in the second source gas supplied to the reaction chamber per unit time, to the first amount of substance, is 1.2 or less. Claim 9 A gas phase growth method according to claim 6, wherein the ratio of the second amount of substance to the first amount of substance (second amount of substance / first amount of substance) is constant during the initial period of membrane formation and the period of increased flow rate. Claim 10 In paragraph 6, a vapor phase growth method in which the amount of the third substance is constant during the initial membrane formation period and the flow rate increase period.

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