Etching method and etching apparatus

Abstract

The present disclosure provides an etching method and an etching apparatus capable of adjusting a distribution of an etching amount in a substrate plane. An etching method of one embodiment of the present disclosure includes preparing a substrate whose surface has a first film, and etching the first film, wherein the etching includes supplying a first gas from an outer side in a radial direction of the substrate toward the substrate, the first gas containing an alkaline gas and not containing a halogen-containing gas, and after the first gas is supplied, supplying a second gas from the outer side in the radial direction of the substrate toward the substrate, the second gas containing the halogen-containing gas and the alkaline gas.

Description

Technical Field

[0001] This disclosure relates to an etching method and etching apparatus. Background Technology

[0002] Patent document 1 discloses the following technique: alternatingly repeating the formation of a silicon oxide film and etching of the silicon oxide film using hydrogen fluoride gas and ammonia gas, so as to fill the recesses formed on the substrate with the silicon oxide film.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2012-199306 Summary of the Invention

[0006] The problem the invention aims to solve

[0007] This disclosure provides a technique for adjusting the distribution of etching amount within a substrate surface.

[0008] means for solving problems

[0009] One aspect of the etching method disclosed herein includes: preparing a substrate having a first film on its surface; and etching the first film, wherein the etching includes: supplying a first gas toward the substrate from the outer side in a radial direction of the substrate, the first gas comprising an alkaline gas and not comprising a halogen-containing gas; and after supplying the first gas, supplying a second gas toward the substrate from the outer side in a radial direction of the substrate, the second gas comprising the halogen-containing gas and the alkaline gas.

[0010] Invention Effects

[0011] According to this disclosure, the distribution of etching amount within the substrate surface can be adjusted. Attached Figure Description

[0012] Figure 1 This is a vertical cross-sectional view showing the etching apparatus involved in the embodiment.

[0013] Figure 2 This is a horizontal cross-sectional view showing the etching apparatus involved in the embodiment.

[0014] Figure 3 This is a diagram showing an example of a substrate.

[0015] Figure 4 This is a timing diagram illustrating the etching method involved in the embodiment.

[0016] Figure 5 Figure (1) is used to illustrate the reaction that occurs on the surface of the substrate.

[0017] Figure 6 Figure (2) is used to illustrate the reaction that occurs on the surface of the substrate.

[0018] Figure 7 Figure (3) is used to illustrate the reaction that occurs on the surface of the substrate.

[0019] Figure 8 Figure (4) is used to illustrate the reaction that occurs on the surface of the substrate.

[0020] Figure 9 This is a diagram illustrating the distribution of etching amounts within the substrate surface involved in the embodiment.

[0021] Figure 10 This is a diagram showing the distribution of the amount of etching within the substrate surface involved in the comparative example. Detailed Implementation

[0022] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all the drawings, the same or corresponding components or parts are labeled with the same or corresponding reference numerals, and repeated descriptions are omitted.

[0023] [Etching apparatus]

[0024] Reference Figure 1 and Figure 2 The etching apparatus 1 according to the embodiment will be described below. Figure 1 This is a vertical cross-sectional view showing the etching apparatus 1 according to the embodiment. Figure 2 This is a horizontal cross-sectional view showing the etching apparatus 1 involved in the embodiment.

[0025] Etching apparatus 1 is a batch processing apparatus that processes multiple substrates W at a time. The substrates W are, for example, semiconductor wafers. Etching apparatus 1 includes a processing container 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, and a control unit 90.

[0026] The interior of the processing container 10 is capable of depressurization. The processing container 10 houses the substrate W. The processing container 10 has an inner tube 11 and an outer tube 12. The inner tube 11 has a topped cylindrical shape that is open at the lower end. The outer tube 12 has a topped cylindrical shape that is open at the lower end and covers the outside of the inner tube 11. The inner tube 11 and the outer tube 12 are formed of a heat-resistant material such as quartz. The inner tube 11 and the outer tube 12 have a double-layer tube structure arranged coaxially.

[0027] A receiving portion 13 for accommodating a gas supply pipe is formed on the side wall of the inner tube 11 along the length direction (vertical direction). For example, a portion of the side wall of the inner tube 11 is made to protrude outward to form a protrusion 14, and the receiving portion 13 is formed inside the protrusion 14.

[0028] A rectangular opening 15 is formed along the length of the side wall of the inner tube 11. The opening 15 faces the receiving part 13.

[0029] The opening 15 is formed as a gas exhaust port for venting gas from the inner tube 11. The length of the opening 15 is the same as or longer than the length of the wafer boat 16 and extends upward and downward respectively.

[0030] The lower end of the processing container 10 is supported by a cylindrical manifold 17. The manifold 17 is made of, for example, stainless steel. A flange 18 is formed at the upper end of the manifold 17. The flange 18 supports the lower end of the outer tube 12. A sealing member 19, such as an O-ring, is provided between the flange 18 and the lower end of the outer tube 12. Thus, the interior of the outer tube 12 is maintained as airtight.

[0031] A ring-shaped support portion 20 is provided on the inner wall of the upper part of the manifold 17. The support portion 20 supports the lower end of the inner tube 11. A cover 21 is airtightly installed at the opening at the lower end of the manifold 17 via a sealing member 22 such as an O-ring. Thus, the opening at the lower end of the processing container 10, i.e., the opening of the manifold 17, is airtightly sealed. The cover 21 is, for example, made of stainless steel.

[0032] A rotating shaft 24 is provided through the center of the cover 21 via a magnetohydrodynamic seal 23. The lower part of the rotating shaft 24 is supported by the arm 25A of the lifting mechanism 25, which is composed of a wafer boat lifting mechanism, in a rotatable manner.

[0033] A rotating plate 26 is provided at the upper end of the rotating shaft 24. A wafer boat 16 holding substrates W is placed on the rotating plate 26 via a quartz-made warming stage 27. The wafer boat 16 rotates by rotating the rotating shaft 24. The wafer boat 16 moves up and down integrally with the cover 21 by raising and lowering the lifting mechanism 25. Thus, the wafer boat 16 is inserted into and detached from the processing container 10. The wafer boat 16 can be housed within the processing container 10. The wafer boat 16 holds multiple (e.g., 50 to 150) substrates W in a rack-like manner. The wafer boat 16 holds multiple wafers W approximately horizontally with spacing in the vertical direction.

[0034] The gas supply unit 30 supplies various gases into the inner tube 11. The gas supply unit 30 has a gas nozzle 31 and a gas nozzle 32. Gas nozzle 31 is an example of a first gas nozzle. Gas nozzle 32 is an example of a second gas nozzle. Gas nozzles 31 and 32 are, for example, formed of quartz. The gas supply unit 30 may also have other gas nozzles.

[0035] Gas nozzle 31 is fixed to manifold 17. Gas nozzle 31 extends linearly in the vertical direction near the inner tube 11, and bends in an L-shape within the manifold 17, extending horizontally and penetrating the manifold 17. Multiple air holes 31h are provided at the portion of gas nozzle 31 located within the inner tube 11. Each air hole 31h is arranged at predetermined intervals in the vertical direction. Each air hole 31h is used to horizontally eject gas from the outer radial direction of the substrate W towards the substrate W. Gas is ejected from each air hole 31h parallel to the main surface of the substrate W.

[0036] A supply path L11 is connected to the gas nozzle 31. In the supply path L11, a hydrogen fluoride (HF) gas supply source G11, a mass flow controller F11, and a valve V11 are sequentially arranged from upstream to downstream in the gas flow direction. Hydrogen fluoride gas is an example of a halogen-containing gas. The timing of the hydrogen fluoride gas supply from the supply source G11 is controlled by the valve V11, and the flow rate is adjusted to a specified value by the mass flow controller F11. The hydrogen fluoride gas flows into the gas nozzle 31 from the supply path L11 and is ejected into the inner tube 11 through multiple gas holes 31h.

[0037] A supply path L12 is connected downstream of valve V11 in supply path L11. In supply path L12, a nitrogen supply source G12, a mass flow controller F12, and valve V12 are sequentially arranged from upstream to downstream in the gas flow direction. Nitrogen is an example of an inert gas. The nitrogen supply to supply source G12 is timed by valve V12 and adjusted to a specified flow rate by mass flow controller F12. Nitrogen flows from supply path L12 into gas nozzle 31 and is ejected from multiple gas holes 31h into inner tube 11.

[0038] Gas nozzle 32 is fixed to manifold 17. Gas nozzle 32 extends linearly in the vertical direction near the inner tube 11, and bends in an L-shape within the manifold 17, extending horizontally and penetrating the manifold 17. Gas nozzle 32 and gas nozzle 31 are arranged circumferentially around the inner tube 11. Multiple air holes 32h are provided at the portion of gas nozzle 32 located within the inner tube 11. Each air hole 32h is arranged at predetermined intervals in the vertical direction. Each air hole 32h is used to horizontally eject gas from the outer radial direction of the substrate W towards the substrate W. Gas is ejected parallel to the main surface of the substrate W from each air hole 32h.

[0039] A supply path L21 is connected to the gas nozzle 32. In the supply path L21, an ammonia (NH3) supply source G21, a mass flow controller F21, and a valve V21 are sequentially arranged from upstream to downstream in the gas flow direction. Ammonia is an example of an alkaline gas. The ammonia supply to the supply source G21 is timed by the valve V21 and adjusted to a specified flow rate by the mass flow controller F21. The ammonia flows into the gas nozzle 32 from the supply path L21 and is ejected into the inner tube 11 through multiple gas holes 32h.

[0040] A supply path L22 is connected downstream of valve V21 in supply path L21. In supply path L22, a nitrogen supply source G22, a mass flow controller F22, and valve V22 are sequentially arranged from upstream to downstream in the gas flow direction. Nitrogen is an example of an inert gas. The nitrogen supply to supply source G22 is timed by valve V22 and adjusted to a specified flow rate by mass flow controller F22. Nitrogen flows from supply path L22 into gas nozzle 32 and is ejected from multiple gas holes 32h into inner tube 11.

[0041] The exhaust section 40 exhausts the gas that exits from the inner pipe 11 through the opening 15 and through the space P1 between the inner pipe 11 and the outer pipe 12 from the gas outlet 41. The gas outlet 41 is formed on the upper side wall of the manifold 17 and above the support 20. An exhaust flow path 42 is connected to the gas outlet 41. A pressure regulating valve 43 and a vacuum pump 44 are sequentially arranged in the exhaust flow path 42, which can exhaust the gas inside the processing container 10.

[0042] A heating element 50 is disposed around the outer tube 12. The heating element 50 is disposed, for example, on the base plate 28. The heating element 50 has a cylindrical shape to cover the outer tube 12. The heating element 50 includes, for example, a heating element to heat the interior of the processing container 10 and each substrate W within the processing container 10.

[0043] The control unit 90 is an electronic circuit such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit). The control unit 90 executes various control actions described in this application specification by executing instruction codes stored in memory or by designing circuits for special purposes.

[0044] [Etching Method]

[0045] Reference Figures 3 to 8 The etching method involved in the implementation will be described below. Figure 3This is a diagram showing an example of substrate W. Figure 4 This is a timing diagram illustrating the etching method involved in the embodiment. Figures 5 to 8 This diagram illustrates the reaction that occurs on the surface of the substrate W. The etching method described in the embodiment is performed under the control of the control unit 90.

[0046] First, the control unit 90 raises arm 25A to move the wafer boat 16, which holds multiple substrates W, into the processing container 10, and achieves a seal by hermetically sealing the opening at the lower end of the processing container 10 with cover 21. For example, as Figure 3 As shown, each substrate W has a silicon nitride film 110, a silicon film 120, and a silicon nitride film 140. The silicon nitride film 110 has a flat upper surface. The silicon film 120 is disposed on the upper surface of the silicon nitride film 110. The silicon film 120 is convex. The silicon film 120 is, for example, an amorphous silicon film. The silicon nitride film 110 and the silicon film 120 form a recess 130. The recess 130 has a bottom surface 131, a side surface 132, and a top surface 133. The silicon nitride film 110 forms the bottom surface 131. The silicon film 120 forms the side surface 132 and the top surface 133. Furthermore, in... Figure 3 In this example, the recess 130 is formed by a silicon nitride film 110 and a silicon film 120, but the type of film forming the recess 130 is not limited to this. A silicon nitride film 140 is disposed along the inner surface of the recess 130. The silicon nitride film 140 is an example of the first film.

[0047] Next, the control unit 90 controls the exhaust unit 40 to bring the pressure inside the processing container 10 to a set pressure, and controls the heating unit 50 to bring the temperature inside the processing container 10 to a first temperature T1. As a result, each substrate W inside the processing container 10 is heated to the first temperature T1. The first temperature T1 is, for example, 50°C or higher and 100°C or lower.

[0048] Next, while maintaining the processing container 10 at a first temperature T1, the control unit 90 etches the silicon nitride film 140 within the processing container 10. The etching of the silicon nitride film 140 is, for example, performed by... Figure 4 The method shown in the timing diagram is used.

[0049] At time t11, the control unit 90 controls the gas supply unit 30 to start the supply of ammonia gas from the gas nozzle 32 into the processing container 10, while the supply of hydrogen fluoride gas from the gas nozzle 31 into the processing container 10 does not start. The supply of ammonia gas from the gas nozzle 32 into the processing container 10 continues until time t13.

[0050] During the period from time t11 to time t12, ammonia gas is supplied to the processing container 10, but hydrogen fluoride gas is not supplied, so ammonia gas permeates the entire processing container 10. As a result, as... Figure 5 As shown, ammonia gas permeates the entire surface of each substrate W.

[0051] During the period from time t11 to time t12, the control unit 90 may also control the gas supply unit 30 to supply nitrogen gas from the gas nozzle 32 into the processing container 10. In this case, the flow rate of ammonia gas supplied from the gas nozzle 32 increases, and therefore the time required for ammonia gas to spread throughout the entire processing container 10 is shortened.

[0052] At time t12, the control unit 90 controls the gas supply unit 30 to start supplying hydrogen fluoride gas from the gas nozzle 31 into the processing container 10 while ammonia gas is being continuously supplied from the gas nozzle 32 into the processing container 10. The supply of hydrogen fluoride gas from the gas nozzle 31 into the processing container 10 continues until time t13.

[0053] During the period from time t12 to time t13, hydrogen fluoride gas and ammonia gas are supplied into the processing container 10. Thereby, the hydrogen fluoride gas and ammonia gas react with the silicon nitride film 140 formed on the surface of each substrate W to form a modified layer. The modified layer may contain, for example, ammonium fluorosilicate (NH4)2SiF6.

[0054] At the time (t12) when hydrogen fluoride and ammonia gas are first supplied to the processing container 10, ammonia gas has already been pre-distributed throughout the entire surface of each substrate W. Therefore, by controlling the flow rate of hydrogen fluoride gas to adjust the inflow pattern of hydrogen fluoride gas into the surface of the substrate W, the thickness distribution of the modified layer within the surface of the substrate W can be adjusted. For example, as... Figure 6 As shown, hydrogen fluoride gas is supplied under conditions where the amount of hydrogen fluoride gas reaching the center of substrate W is approximately the same as the amount of hydrogen fluoride gas reaching the ends of substrate W. This allows the formation of a modified layer with approximately the same thickness distribution at the center and ends of substrate W, or a modified layer with a thickness distribution at the center of substrate W that is thicker than at the ends. For example, as... Figure 7 As shown, hydrogen fluoride gas is supplied such that more hydrogen fluoride gas reaches the ends than reaches the center of the substrate W. This allows the formation of a modified layer with a thickness distribution where the thickness at the center of the substrate W is thinner than that at the ends. Conversely, if ammonia gas is not supplied to the processing container 10 before supplying hydrogen fluoride gas and ammonia gas, at time t12, ammonia gas does not permeate the entire surface of each substrate W. Therefore, as... Figure 8 As shown, the formation of the altered layer progresses from the end of the substrate W, making it difficult to adjust the thickness distribution of the altered layer within the surface of the substrate W.

[0055] Furthermore, when ammonia gas has been pre-distributed throughout the entire surface of each substrate W at the time (time t12) when hydrogen fluoride gas and ammonia gas are first supplied into the processing container 10, the thickness distribution of the modified layer in the surface of the substrate W can be made uniform among multiple substrates W.

[0056] During the period from time t12 to time t13, the control unit 90 can also control the gas supply unit 30 to supply nitrogen gas into the processing container 10 from the gas nozzle 31. In this case, by controlling the flow rate of the nitrogen gas supplied from the gas nozzle 31 into the processing container 10, the flow rate of the hydrogen fluoride gas supplied from the gas nozzle 31 can be adjusted. For example, by increasing the flow rate of the nitrogen gas supplied from the gas nozzle 31 into the processing container 10, the flow rate of the hydrogen fluoride gas supplied from the gas nozzle 31 increases, making it easier for the hydrogen fluoride gas to reach the center of each substrate W. As a result, the ratio of the thickness of the modified layer formed at the center of the substrate W to the thickness of the modified layer formed at the ends of the substrate W becomes higher.

[0057] During the period from time t12 to time t13, the control unit 90 can also control the gas supply unit 30 to supply nitrogen gas from the gas nozzle 32 into the processing container 10. In this case, by controlling the flow rate of the nitrogen gas supplied from the gas nozzle 32 into the processing container 10, the flow rate of the ammonia gas supplied from the gas nozzle 32 can be adjusted. For example, by increasing the flow rate of the nitrogen gas supplied from the gas nozzle 32 into the processing container 10, the flow rate of the ammonia gas supplied from the gas nozzle 32 increases, and the ammonia gas easily reaches the center of each substrate W. As a result, the ratio of the thickness of the altered layer formed at the center of the substrate W to the thickness of the altered layer formed at the ends of the substrate W becomes higher.

[0058] At time t13, the control unit 90 controls the gas supply unit 30 to stop the supply of hydrogen fluoride gas and nitrogen gas from the gas nozzle 31 to the processing container 10, and to stop the supply of ammonia gas and nitrogen gas from the gas nozzle 32 to the processing container 10. As a result, during the period from time t13 to time t14, the processing container 10 is evacuated, and the hydrogen fluoride gas and ammonia gas remaining in the processing container 10 are discharged from the processing container 10.

[0059] At time t14, the control unit 90 controls the heating unit 50 to bring the temperature inside the processing container 10 to a second temperature T2, which is higher than the first temperature T1. This second temperature is above the sublimation temperature of ammonium fluorosilicate, for example, above 200°C. As a result, the substrate W is annealed at the second temperature T2, and the ammonium fluorosilicate sublimates. Consequently, the silicon nitride film 140 formed on the surface of each substrate W is etched. Since the thickness distribution of the modified layer within the surface of the substrate W has been adjusted, the silicon nitride film 140 is etched with the same distribution as the adjusted modified layer thickness distribution. Thus, by adjusting the modified layer thickness distribution, the distribution of the etching amount within the surface of the substrate W can be adjusted. Furthermore, since the thickness distribution of the modified layer within the surface of the substrate W is consistent across multiple substrates W, the etching shape of the silicon nitride film 140 can be made consistent across multiple substrates W.

[0060] [Experimental Results]

[0061] In this embodiment, a substrate with a silicon nitride film on its surface is first prepared. Next, the prepared substrate is housed within the processing container 10 of the etching apparatus 1. Then, the etching process is performed within the processing container 10. Figure 4 The etching method shown in the timing diagram was used to etch the silicon nitride film. Specifically, during the etching of the silicon nitride film, ammonia gas was initially supplied to the substrate without hydrogen fluoride gas, and then hydrogen fluoride gas and ammonia gas were supplied to the substrate from the middle of the etching process. In the embodiment, the thickness of the silicon nitride film before and after etching was measured, and the difference in thickness before and after etching was calculated as the etching amount of the silicon nitride film.

[0062] In the comparative example, a substrate with a silicon nitride film on its surface was prepared in the same manner as in the embodiment. Next, the prepared substrate was placed into the processing container 10 of the etching apparatus 1. Then, hydrogen fluoride gas and ammonia gas were supplied to the substrate within the processing container 10. In the comparative example, the process of supplying ammonia gas to the substrate without supplying hydrogen fluoride gas was not performed. In the comparative example, the thickness of the silicon nitride film before and after etching was measured in the same manner as in the embodiment, and the difference in thickness of the silicon nitride film before and after etching was calculated as the etching amount of the silicon nitride film.

[0063] Figure 9 This is a diagram illustrating the distribution of etching amounts within the substrate surface involved in the embodiment. Figure 9 The image shows the distribution of the etching depth [Å] of the silicon nitride film within the substrate surface when the substrate is housed at the top (TOP), middle (CTR), and bottom (BTM) positions of the wafer boat 16. Figure 9 As shown, in the embodiment, there is a tendency for the etching amount of the silicon nitride film in the central part to be greater than that at the ends of the TOP, CTR, and BTM at any position. Based on this result, it can be said that the embodiment can make the etching shape of the silicon nitride film consistent between multiple substrates.

[0064] Figure 10 This is a diagram showing the distribution of etching amount within the substrate surface involved in the comparative example. Figure 10 The image shows the distribution of the etching depth [Å] of the silicon nitride film within the substrate surface when the substrate is housed at the top (TOP), middle (CTR), and bottom (BTM) positions of the wafer boat 16. Figure 10 As shown, in the comparative example, the etch distribution on the substrate surface at the TOP and BTM locations tends to differ from the etch distribution on the substrate surface at the CTR location. Based on this result, it can be concluded that it is difficult to achieve consistent etch patterns of the silicon nitride film between multiple substrates using the comparative example.

[0065] The embodiments disclosed herein should be considered illustrative in all respects, not restrictive. The above embodiments may be omitted, substituted, or modified in various ways without departing from the appended claims and their spirit.

[0066] The above embodiments describe the case where the halogen-containing gas is hydrogen fluoride gas, but this disclosure is not limited to this. The halogen-containing gas may also be fluorine (F2) gas, chlorine trifluoride (ClF3) gas, or nitrogen trifluoride (NF3) gas.

[0067] The above embodiments describe the use of ammonia as the alkaline gas, but this disclosure is not limited to this. The alkaline gas may also be dimethylamine, trimethylamine, or hydrazine.

[0068] The above embodiments describe the use of nitrogen as the inactive gas, but this disclosure is not limited to this. The inactive gas may also be a rare gas such as helium (He), neon (Ne), or argon (Ar).

[0069] In the above embodiments, the case where the first film is a silicon nitride film was described, but this disclosure is not limited to this. The first film may also be a silicon oxide film, a SiON film, a SiOCN film, a SiBN film, or a SiOC film.

[0070] The above embodiments describe a batch etching apparatus that processes multiple substrates at once, but this disclosure is not limited thereto. For example, the etching apparatus may also be a single-sheet apparatus that processes substrates one by one.

[0071] Explanation of reference numerals in the attached figures

[0072] 140: Silicon nitride film; W: Substrate.

Claims

1. An etching method, comprising: Prepare a substrate with a first film on its surface; as well as The first film is etched. The etching process includes: A first gas, comprising an alkaline gas and not containing a halogen-containing gas, is supplied from the outer side of the substrate in the radial direction toward the substrate; and After the first gas is supplied, a second gas is supplied from the outer side of the substrate in the radial direction toward the substrate, the second gas comprising the halogen-containing gas and the alkaline gas.

2. The etching method according to claim 1, wherein, The etching process includes annealing the substrate at a temperature higher than the temperature at which the second gas is supplied after the second gas is supplied.

3. The etching method according to claim 1, wherein, The first gas and the second gas are supplied in a manner parallel to the main surface of the substrate.

4. The etching method according to claim 1, wherein, The halogen-containing gas is supplied to the substrate from the first gas nozzle along with the inactive gas.

5. The etching method according to claim 1, wherein, The alkaline gas is supplied to the substrate from a second gas nozzle along with the inactive gas.

6. The etching method according to any one of claims 1 to 5, wherein, A recess is formed on the surface of the substrate. The first membrane is formed along the inner surface of the recess.

7. The etching method according to any one of claims 1 to 5, wherein, The first film is a silicon nitride film.

8. The etching method according to any one of claims 1 to 5, wherein, The halogen-containing gas is hydrogen fluoride gas. The alkaline gas is ammonia.

9. An etching apparatus comprising: A processing container that houses a substrate; A gas supply unit that supplies gas into the processing container; and Control Department in, The control unit is configured to perform the following processes: Prepare a substrate with a first film on its surface; as well as The first film is etched. The etching process includes: A first gas, comprising an alkaline gas and not containing a halogen-containing gas, is supplied from the outer side of the substrate in the radial direction toward the substrate; and After the first gas is supplied, a second gas is supplied from the outer side of the substrate in the radial direction toward the substrate, the second gas comprising the halogen-containing gas and the alkaline gas.

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