Substrate processing method and substrate processing apparatus

Abstract

To provide a technology that can adjust the in-plane distribution of etching volume.SOLUTION: A substrate processing method according to an aspect of the present disclosure has (a) a step for preparing a substrate having a silicon oxide film on its surface, (b) a step for supplying a first gas containing hydrogen fluoride gas and containing no basic gas to the surface of the substrate, and (c) after the step (b), a step for supplying a second gas containing hydrogen fluoride gas and a basic gas to the surface of the substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a substrate processing method and a substrate processing apparatus. [Background technology]

[0002] A technique is known in which a silicon oxide film is etched using a mixed gas of hydrogen fluoride gas and ammonia gas (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-343094 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique capable of adjusting the in-plane distribution of the etching amount. [Means for solving the problem]

[0005] A substrate processing method according to one embodiment of the present disclosure includes the steps of: (a) preparing a substrate having a silicon oxide film on a surface thereof; (b) supplying a first gas containing hydrogen fluoride gas and no basic gas to the surface of the substrate; and (c) after step (b), supplying a second gas containing hydrogen fluoride gas and a basic gas to the surface of the substrate. Effect of the Invention

[0006] According to the present disclosure, the in-plane distribution of the etching amount can be adjusted. [Brief description of the drawings]

[0007] [Figure 1] 3 is a flowchart illustrating a substrate processing method according to the embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing an example of a substrate. [Diagram 3] FIG. 13 shows the surface reaction when a HF supply step is performed before a COR step. [Figure 4] FIG. 13 shows a surface reaction when a HF supply step is not performed before a COR step. [Diagram 5] 1 is a cross-sectional view showing a substrate processing apparatus according to an embodiment. [Figure 6] FIG. 13 is a diagram showing the results of measuring the in-plane distribution of the etching amount of a silicon oxide film. [Figure 7] FIG. 13 is a diagram showing the results of measuring the in-plane distribution of the etching amount of a silicon nitride film. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, non-limiting exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. In all of the accompanying drawings, the same or corresponding members or parts are designated by the same or corresponding reference numerals, and duplicated descriptions will be omitted.

[0009] [Silicon oxide film etching] There is a known technique for etching a silicon oxide film formed on the surface of a substrate by a chemical oxide removal (COR) process. In the COR process, a mixture of hydrogen fluoride (HF) gas and ammonia (NH3) gas is supplied to the silicon oxide film to etch it.

[0010] Etching of silicon oxide film by COR treatment is a highly reactive process. Therefore, when a mixture of hydrogen fluoride gas and ammonia gas is supplied from the periphery of the substrate along the surface of the substrate, the amount of silicon oxide film etched at the outer periphery of the substrate becomes larger than the amount of silicon oxide film etched at the center of the substrate, and the in-plane uniformity of the amount of etching may deteriorate. This is thought to be because the hydrogen fluoride gas and ammonia gas react with the silicon oxide film at the outer periphery of the substrate and are consumed before reaching the center of the substrate.

[0011] As the COR process time is increased, the center of the substrate is gradually etched more easily than the periphery, improving the in-plane uniformity. However, as the etching time is increased, the amount of silicon oxide film etched increases. Therefore, it is difficult to improve the in-plane uniformity of the amount of silicon oxide film etched with a small amount of etching.

[0012] When a silicon nitride film is formed on the surface of a substrate as a hard mask, it is required that the silicon nitride film is not etched or is hardly etched when the silicon oxide film is etched. However, if the COR process time is extended, the silicon nitride film is easily etched.

[0013] The present inventors have found that, by supplying a first gas containing hydrogen fluoride gas but not containing a basic gas to the surface of the substrate before performing the COR process, it is possible to adjust the in-plane distribution of the etching amount of the silicon oxide film with a small etching amount. Hereinafter, a substrate processing method and a substrate processing apparatus according to an embodiment will be described.

[0014] [Substrate Processing Method] A substrate processing method according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a flowchart showing the substrate processing method according to the embodiment. Figure 2 is a cross-sectional view showing an example of a substrate 100.

[0015] As shown in FIG. 1, the substrate processing method according to the embodiment includes a preparation step S10, an HF supplying step S20, a COR step S30, and a PHT step S40.

[0016] The preparation step S10 includes preparing a substrate 100 having a silicon nitride film 102 and a silicon oxide film 103 on its surface, as shown in FIG. 2. The silicon nitride film 102 and the silicon oxide film 103 are formed on a base substrate 101. The base substrate 101 is, for example, a silicon wafer. The silicon oxide film 103 is, for example, a thermal oxide film formed by a thermal oxidation process. The preparation step S10 may include adjusting and maintaining the substrate 100 at a predetermined temperature. The predetermined temperature may be the same as a first process temperature described below. In this case, there is no need to change the temperature when transitioning from the preparation step S10 to the HF supply step S20. This improves productivity.

[0017] The HF supplying step S20 is performed after the preparing step S10. The HF supplying step S20 includes supplying a first gas containing hydrogen fluoride gas and not containing a basic gas to the surface of the substrate 100. When the hydrogen fluoride gas is supplied to the surface of the substrate 100, the silicon oxide film 103 reacts with the hydrogen fluoride gas to generate silicon tetrafluoride (SiF4). If a native oxide film exists on the silicon nitride film 102, the native oxide film reacts with the hydrogen fluoride gas to be etched. The first gas may further include an inert gas such as nitrogen (N2) gas. The first gas is, for example, a mixed gas of hydrogen fluoride gas and nitrogen gas. The HF supplying step S20 may include adjusting and maintaining the substrate 100 at a first processing temperature. The first processing temperature is, for example, the same as a second processing temperature described later.

[0018] The COR step S30 is performed after the HF supply step S20. The COR step S30 includes converting at least the surface layer of the silicon oxide film 103 into a reaction product by a COR process that performs chemical etching without generating plasma. The COR step S30 includes supplying a second gas containing hydrogen fluoride gas and a basic gas to the surface of the substrate 100. When the hydrogen fluoride gas and the basic gas are supplied to the surface of the substrate 100, the silicon oxide film 103 reacts with the hydrogen fluoride gas and the basic gas to generate ammonium silicofluoride [(NH4)2SiF6]. The basic gas is, for example, ammonia gas. The basic gas may be hydrazine (N2H4) gas. The second gas may further include an inert gas such as nitrogen gas. The second gas is, for example, a mixed gas of hydrogen fluoride gas, ammonia gas, and nitrogen gas.

[0019] The COR step S30 may be performed continuously with the supply of hydrogen fluoride gas continuing after the HF supply step S20. In other words, the COR step S30 may be performed without performing a purge step after the HF supply step S20. In this case, the COR step S30 can be performed without desorbing silicon tetrafluoride generated on the surface of the substrate 100 in the HF supply step S20 from the surface of the substrate 100.

[0020] The COR step S30 may include maintaining the temperature of the substrate 100 at a second process temperature. The second process temperature may be, for example, 0° C. or higher and may be higher than room temperature. The second process temperature may be 120° C. or lower, or may be 80° C. or lower. When the second process temperature is 120° C. or lower, the silicon oxide film 103 is easily etched.

[0021] The time for the HF supplying step S20 may be longer than the time for the COR step. In this case, silicon tetrafluoride is likely to be generated over the entire surface of the substrate 100. The time for the HF supplying step S20 is, for example, 20 minutes. The time for the COR step S30 is, for example, 60 seconds.

[0022] The PHT step S40 is performed after the COR step S30. The PHT step S40 includes sublimating reaction products by PHT (post heat treatment) in which the substrate 100 is heat-treated while being maintained at a third processing temperature higher than the second processing temperature. By performing the PHT step S40, reaction products remaining on the surface of the substrate 100 can be removed. The PHT step S40 may include supplying a third gas to the surface of the substrate 100. The third gas is, for example, hydrogen (H2) gas.

[0023] The surface reaction when the HF supplying step S20 and the COR step S30 are performed consecutively in this order will be described with reference to Fig. 3. Fig. 3 is a diagram showing the surface reaction when the HF supplying step S20 is performed before the COR step S30.

[0024] 3(a), when hydrogen fluoride gas is supplied to the surface of the substrate 100 in the HF supplying step S20, the silicon oxide film 103 reacts with the hydrogen fluoride gas to generate silicon tetrafluoride. The chemical reaction formula at this time is as follows:

[0025] SiO2+4HF→SiF4+2H2O (1)

[0026] Next, in the COR step S30, when fluorine gas and ammonia gas are supplied to the surface of the substrate 100, the silicon oxide film 103 reacts with the hydrogen fluoride gas and ammonia gas to generate silicon tetrafluoride. The chemical reaction formula at this time is as follows.

[0027] SiO2+4HF+4NH3→SiF4+2H2O+4NH3(2)

[0028] In the COR step S30, the silicon tetrafluoride produced in the HF supply step S20 reacts with fluorine gas and ammonia gas to produce ammonium silicon fluoride [(NH4)2SiF6]. The chemical reaction formula at this time is as follows:

[0029] SiF4+2HF+2NH3→(NH4)2SiF6(3)

[0030] When the COR step S30 is performed in a state where silicon tetrafluoride is present on the surface of the substrate 100, the reaction represented by chemical reaction formula (3) is more likely to proceed than the reaction represented by chemical reaction formula (2). Therefore, when hydrogen fluoride gas and ammonia gas are supplied to the surface of the substrate 100, ammonium silicofluoride is likely to be produced by the reaction between silicon tetrafluoride and the hydrogen fluoride gas and ammonia gas.

[0031] 3(b), when fluorine gas and ammonia gas are supplied from the periphery of substrate 100 along the surface of substrate 100, silicon tetrafluoride on the periphery of substrate 100 reacts with hydrogen fluoride gas and ammonia gas to generate ammonium silicon fluoride immediately after the supply starts. This is thought to be because the reaction expressed by chemical reaction formula (3) is highly reactive, and hydrogen fluoride gas and ammonia gas react with silicon tetrafluoride on the periphery of substrate 100 and are consumed before reaching the center of substrate 100.

[0032] Ammonium silicofluoride suppresses the generation of silicon tetrafluoride due to the reaction of the silicon oxide film 103 with hydrogen fluoride gas and ammonia gas. Therefore, the etching of the silicon oxide film 103 at the outer periphery of the substrate 100 is suppressed by ammonium silicofluoride. As a result, the etching rate of the silicon oxide film 103 at the center of the substrate 100 is higher than the etching rate of the silicon oxide film 103 at the outer periphery of the substrate 100. As a result, the in-plane distribution of the etching amount of the silicon oxide film 103 at the center of the substrate 100 is greater than that at the outer periphery of the substrate 100. In other words, the in-plane shape of the etching amount becomes convex.

[0033] 3(c) and 3(d), when the supply of hydrogen fluoride gas and ammonia gas to the substrate 100 continues, the region where ammonium silicofluoride is generated expands from the outer periphery toward the center of the substrate 100. Therefore, the etching rate of the silicon oxide film 103 in the center of the substrate 100 approaches the etching rate of the silicon oxide film 103 in the outer periphery of the substrate 100.

[0034] A surface reaction occurring when the COR step S30 is performed without performing the HF supplying step S20 will be described with reference to Fig. 4. Fig. 4 is a diagram showing a surface reaction occurring when the HF supplying step S20 is not performed before the COR step S30.

[0035] When the COR step S30 is performed without performing the HF supply step S20, when hydrogen fluoride gas and ammonia gas are supplied to the surface of the substrate 100 in the COR step S30, the silicon oxide film 103 reacts with the hydrogen fluoride gas and ammonia gas to generate silicon tetrafluoride. The chemical reaction formula at this time is the same as the above-mentioned formula (2).

[0036] 4(a), when hydrogen fluoride gas and ammonia gas are supplied from the periphery of the substrate 100 along the surface of the substrate 100, the silicon oxide film 103 is etched more in the outer periphery of the substrate 100 than in the center immediately after the supply starts. This is believed to be because the reaction expressed by chemical reaction formula (2) is highly reactive, and the hydrogen fluoride gas and ammonia gas react with the silicon oxide film 103 in the outer periphery of the substrate 100 and are consumed before reaching the center of the substrate 100. As a result, the in-plane distribution results in a greater amount of etching of the silicon oxide film 103 in the outer periphery of the substrate 100 than in the center. In other words, the in-plane shape of the etching amount becomes concave.

[0037] When the supply of hydrogen fluoride gas and ammonia gas to the substrate 100 is continued, ammonium silicofluoride starts to be generated in the outer periphery of the substrate 100 as shown in FIG. 4(b). Furthermore, when the supply of hydrogen fluoride gas and ammonia gas to the substrate 100 is continued, the region where ammonium silicofluoride is generated spreads from the outer periphery to the center of the substrate 100 as shown in FIG. 4(c). Therefore, the etching rate of the silicon oxide film 103 in the center of the substrate 100 becomes higher than the etching rate of the silicon oxide film 103 in the outer periphery of the substrate 100. As a result, the in-plane distribution in which the etching amount of the silicon oxide film 103 in the outer periphery of the substrate 100 is greater than that in the center of the substrate 100 changes to the in-plane distribution in which the etching amount of the silicon oxide film 103 in the center of the substrate 100 is greater than that in the outer periphery of the substrate 100. That is, the in-plane shape of the etching amount changes from a concave shape to a convex shape.

[0038] In this way, when the COR step S30 is performed without performing the HF supply step S20, the etching time is lengthened in order to adjust the in-plane shape of the etching amount to a convex shape. Therefore, it is difficult to adjust the in-plane shape of the etching amount of the silicon oxide film 103 from a concave shape to a convex shape with an etching amount smaller than the desired etching amount. In addition, when the silicon nitride film 102 is formed on the surface of the substrate 100 as a hard mask, the silicon nitride film 102 becomes more easily etched as the etching time is lengthened, and the etching selectivity of the silicon oxide film 103 to the silicon nitride film 102 decreases.

[0039] As described above, according to the substrate processing method of the embodiment, the HF supplying step S20 is performed before the COR step S30, which allows the in-plane distribution of the etching amount of the silicon oxide film 103 to be adjusted with a small etching amount.

[0040] [Substrate Processing Apparatus] The substrate processing apparatus 1 according to the embodiment will be described with reference to Fig. 5. As shown in Fig. 5, the substrate processing apparatus 1 is a batch type apparatus that processes a plurality of substrates W at once.

[0041] The substrate processing apparatus 1 includes a processing container 10, a gas supply unit 30, an exhaust unit 40, a heating unit 50, and a control unit 80.

[0042] The processing vessel 10 is capable of reducing the pressure inside. The processing vessel 10 accommodates a substrate W therein. The processing vessel 10 has an inner tube 11 and an outer tube 12. The inner tube 11 and the outer tube 12 have a cylindrical shape with a ceiling and an open lower end. The outer tube 12 covers the outside of the inner tube 11. The inner tube 11 and the outer tube 12 have a double tube structure arranged coaxially. The inner tube 11 and the outer tube 12 are formed of a heat-resistant material such as quartz.

[0043] The ceiling of the inner pipe 11 may be flat, for example. A storage section 13 for storing a gas nozzle is formed along the longitudinal direction (vertical direction) of the inner pipe 11 on one side. For example, a part of the side wall of the inner pipe 11 protrudes outward to form a convex section 14, and the inside of the convex section 14 is formed as the storage section 13.

[0044] In the side wall on the opposite side of the inner tube 11 facing the storage portion 13, a rectangular opening 15 is formed along the longitudinal direction (vertical direction).

[0045] The opening 15 is a gas exhaust port formed so as to be able to exhaust the gas inside the inner tube 11. The length of the opening 15 is the same as the length of the boat 16, or is formed so as to extend longer than the length of the boat 16 in the vertical direction.

[0046] The lower end of the processing vessel 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 seal member 19 such as an O-ring is provided between the flange 18 and the lower end of the outer tube 12. This keeps the inside of the outer tube 12 airtight.

[0047] An annular support 20 is provided on the inner wall of the upper part of the manifold 17. The support 20 supports the lower end of the inner tube 11. A lid 21 is air-tightly attached to the opening at the lower end of the manifold 17 via a seal member 22 such as an O-ring. This air-tightly closes the opening at the lower end of the processing vessel 10, i.e., the opening of the manifold 17. The lid 21 is made of, for example, stainless steel.

[0048] A rotating shaft 24 is provided penetrating the center of the lid 21 via a magnetic fluid seal 23. A lower portion of the rotating shaft 24 is rotatably supported by an arm 25A of an elevation mechanism 25 made up of a boat elevator.

[0049] A rotating plate 26 is provided at the upper end of the rotating shaft 24. The boat 16, which holds the substrates W, is placed on the rotating plate 26 via a quartz heat retention stand 27. The boat 16 rotates by rotating the rotating shaft 24. The boat 16 moves up and down together with the lid 21 by raising and lowering the lifting mechanism 25. This allows the boat 16 to be inserted into and removed from the processing vessel 10. The boat 16 can be accommodated within the processing vessel 10. The boat 16 holds a plurality of substrates W (e.g., 50 to 150 substrates) approximately horizontally with a gap between them in the vertical direction.

[0050] The gas supply unit 30 is configured to be able to introduce various process gases used in the above-mentioned substrate processing method into the inner tube 11. The gas supply unit 30 includes a hydrogen fluoride supply unit 31 and an ammonia supply unit 32.

[0051] The hydrogen fluoride supply unit 31 includes a hydrogen fluoride supply pipe 31a inside the processing vessel 10, and a hydrogen fluoride supply path 31b outside the processing vessel 10. A hydrogen fluoride supply source 31c, a mass flow controller 31d, and a valve 31e are provided in the hydrogen fluoride supply path 31b, in this order from the upstream side to the downstream side in the gas flow direction. Thus, the supply timing of the hydrogen fluoride gas from the hydrogen fluoride supply source 31c is controlled by the valve 31e, and the flow rate is adjusted to a predetermined value by the mass flow controller 31d. The hydrogen fluoride gas flows from the hydrogen fluoride supply path 31b into the hydrogen fluoride supply pipe 31a, and is discharged from the hydrogen fluoride supply pipe 31a into the processing vessel 10.

[0052] The ammonia supply unit 32 includes an ammonia supply pipe 32a inside the processing vessel 10, and an ammonia supply path 32b outside the processing vessel 10. An ammonia source 32c, a mass flow controller 32d, and a valve 32e are provided in the ammonia supply path 32b, in this order from the upstream side to the downstream side in the gas flow direction. Thus, the supply timing of the ammonia gas from the ammonia source 32c is controlled by the valve 32e, and the flow rate is adjusted to a predetermined value by the mass flow controller 32d. The ammonia gas flows from the ammonia supply path 32b into the ammonia supply pipe 32a, and is discharged from the ammonia supply pipe 32a into the processing vessel 10.

[0053] Each gas supply pipe (hydrogen fluoride supply pipe 31a, ammonia supply pipe 32a) is fixed to manifold 17. Each gas supply pipe is made of, for example, quartz. Each gas supply pipe extends linearly in the vertical direction near inner pipe 11, and then bends in an L-shape within manifold 17 and extends horizontally, penetrating manifold 17. Each gas supply pipe is provided side by side along the circumferential direction of inner pipe 11, and is formed at the same height as each other.

[0054] A plurality of hydrogen fluoride discharge ports 31f are provided in the hydrogen fluoride supply pipe 31a at a portion located within the inner pipe 11. A plurality of ammonia discharge ports 32f are provided in the ammonia supply pipe 32a at a portion located within the inner pipe 11.

[0055] The outlets (hydrogen fluoride outlet 31f, ammonia outlet 32f) are formed at predetermined intervals along the extension direction of the respective gas supply pipes. Each outlet discharges gas in the horizontal direction. The interval between each outlet is set to be the same as the interval between the substrates W held in the boat 16, for example. The height position of each outlet is set to the midpoint between the substrates W adjacent in the vertical direction. This allows each outlet to efficiently supply gas to the opposing surfaces between the adjacent substrates W.

[0056] The gas supply unit 30 may mix a plurality of types of gases and discharge the mixed gas from one gas supply pipe. The gas supply pipes (hydrogen fluoride supply pipe 31a, ammonia supply pipe 32a) may have different shapes and arrangements. The substrate processing apparatus 1 may further include a gas supply pipe for supplying another gas in addition to the hydrogen fluoride gas and the ammonia gas.

[0057] The exhaust unit 40 exhausts gas that is exhausted from the inner tube 11 through the opening 15 and then exhausted from a gas outlet 41 through a space P1 between the inner tube 11 and the outer tube 12. The gas outlet 41 is formed in an upper side wall of the manifold 17, above the support unit 20. An exhaust passage 42 is connected to the gas outlet 41. A pressure adjustment valve 43 and a vacuum pump 44 are sequentially provided in the exhaust passage 42, so that the inside of the processing vessel 10 can be exhausted.

[0058] The heating unit 50 is provided around the outer tube 12. The heating unit 50 is provided, for example, on the base plate 28. The heating unit 50 has a cylindrical shape so as to cover the outer tube 12. The heating unit 50 includes, for example, a heater, and heats each substrate W in the processing chamber 10.

[0059] The control unit 80 controls the operation of each part of the substrate processing apparatus 1. The control unit 80 may be, for example, a computer. A computer program for controlling the operation of each part of the substrate processing apparatus 1 is stored in a storage medium 90. The storage medium 90 may be, for example, a flexible disk, a compact disk, a hard disk, a flash memory, a DVD, or the like.

[0060] [Operation of the Substrate Processing Apparatus] The operation of the substrate processing apparatus 1 when carrying out the substrate processing method according to the embodiment will be described.

[0061] First, the control unit 80 controls the lifting mechanism 25 to load the boat 16 holding the substrates W into the processing vessel 10, and hermetically closes the opening at the bottom of the processing vessel 10 with the lid 21. Next, the control unit 80 controls the exhaust unit 40 to reduce the pressure inside the processing vessel 10, and controls the heating unit 50 to adjust the temperature of the substrates W to a predetermined temperature. Each substrate W may be the substrate 100 described above.

[0062] Next, the control unit 80 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to execute the HF supplying step S20. Specifically, first, the control unit 80 controls the heating unit 50 to maintain the temperature of the substrate W at the first processing temperature, controls the gas supply unit 30 to supply a first gas into the processing vessel 10, and controls the exhaust unit 40 to maintain the inside of the processing vessel 10 at the processing pressure. The first gas is a gas that contains hydrogen fluoride gas but does not contain a basic gas. As a result, the silicon oxide film 103 reacts with the hydrogen fluoride gas to generate silicon tetrafluoride.

[0063] Next, the control unit 80 controls the gas supply unit 30, the exhaust unit 40, and the heating unit 50 to execute the COR process S30. Specifically, first, the control unit 80 controls the heating unit 50 to adjust and maintain the temperature of the substrate W at the second processing temperature, controls the gas supply unit 30 to supply a second gas into the processing vessel 10, and controls the exhaust unit 40 to maintain the inside of the processing vessel 10 at the processing pressure. The second gas is a gas containing hydrogen fluoride gas and a basic gas. As a result, the silicon oxide film 103 reacts with the hydrogen fluoride gas and the basic gas to generate ammonium silicofluoride.

[0064] Next, control unit 80 increases the pressure inside processing vessel 10 to atmospheric pressure and decreases the temperature inside processing vessel 10 to the unloading temperature, and then controls lifting mechanism 25 to unload boat 16 from processing vessel 10 .

[0065] [Example] Example 1 In Example 1, a wafer having a silicon oxide film and a silicon nitride film on its surface was prepared. The prepared wafer was then placed in the processing vessel 10 of the substrate processing apparatus 1, and the HF supply step S20, the COR step S30, and the PHT step S40 were carried out in this order. The etching amounts of the silicon oxide film and the silicon nitride film were then measured. The conditions for the HF supply step S20, the COR step S30, and the PHT step S40 were as follows:

[0066] (HF supply process S20) Wafer temperature: 65℃ Processing pressure: 0.2 Torr (26.7 Pa) First gas: HF gas / N2 gas = 300sccm / 2100sccm Processing time: 20 minutes

[0067] (COR process S30) Wafer temperature: 65℃ Processing pressure: 0.2 Torr (26.7 Pa) Second gas: HF gas / NH3 gas / N2 gas = 300sccm / 300sccm to 1800sccm Processing time: 60 seconds

[0068] (PHT process S40) Wafer temperature: 200℃ Third gas: H2 gas Processing time: 30 minutes

[0069] Comparative Example 1 In Comparative Example 1, a wafer having a silicon oxide film and a silicon nitride film on its surface was prepared in the same manner as in Example 1. The prepared wafer was then placed in the processing vessel 10 of the substrate processing apparatus 1, and the COR process S30 and the PHT process S40 were carried out in this order without carrying out the HF supply process S20. Then, the etching amounts of the silicon oxide film and the silicon nitride film were measured in the same manner as in Comparative Example 1. The conditions of the COR process S30 and the PHT process S40 were the same as those of the COR process S30 and the PHT process S40 in Example 1.

[0070] Fig. 6 is a diagram showing the results of measuring the in-plane distribution of the etching amount of the silicon oxide film. In Fig. 6, the horizontal axis indicates the radial position of the wafer, and the vertical axis indicates the etching amount [nm] of the silicon oxide film. In Fig. 6, circles indicate the results of Example 1, and triangles indicate the results of Comparative Example 1.

[0071] 6, it can be seen that the amount of etching of the silicon oxide film at the center of the wafer is greater than the amount of etching of the silicon oxide film at the outer periphery of the wafer in Example 1. In other words, it can be seen that the in-plane shape of the amount of etching of the silicon oxide film in Example 1 is convex.

[0072] In contrast, as shown by the triangles in Fig. 6, in Comparative Example 1, the amount of etching of the silicon oxide film at the center of the wafer is smaller than the amount of etching of the silicon oxide film at the periphery of the wafer. In other words, in Comparative Example 1, the in-plane shape of the amount of etching of the silicon oxide film is concave. This result shows that the in-plane shape of the amount of etching of the silicon oxide film can be adjusted from concave to convex by performing the HF supplying step S20 before the COR step S30.

[0073] Fig. 7 is a diagram showing the results of measuring the in-plane distribution of the etching amount of the silicon nitride film. In Fig. 7, the horizontal axis indicates the radial position of the wafer, and the vertical axis indicates the etching amount [nm] of the silicon nitride film. In Fig. 7, circles indicate the results of Example 1, and triangles indicate the results of Comparative Example 1.

[0074] 7, it can be seen that the etching amount of the silicon nitride film is about 1 nm in Comparative Example 1, whereas the etching amount of the silicon nitride film is about 0.2 nm in Example 1. This result shows that the etching amount of the silicon nitride film can be reduced by performing the HF supply step S20 before the COR step S30. In other words, it shows that the etching selectivity of the silicon oxide film to the silicon nitride film can be increased.

[0075] Previous experiments by the inventors have shown that the more native oxide there is on the silicon nitride film, the more the silicon nitride film is etched by the COR step S30. From this, it is believed that the native oxide on the silicon nitride film is etched by the HF supply step S20, and there is almost no native oxide on the silicon nitride film at the time of the COR step S30, so that the etching of the silicon nitride film is suppressed.

[0076] The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The above-described embodiments may be omitted, substituted, or modified in various forms without departing from the scope and spirit of the appended claims.

[0077] In the above embodiment, the substrate processing apparatus is a batch type apparatus that processes a plurality of substrates at once, but the present disclosure is not limited thereto. For example, the substrate processing apparatus may be a single-wafer type apparatus that processes substrates one by one. For example, the substrate processing apparatus may be a semi-batch type apparatus that rotates a plurality of substrates arranged on a turntable in a processing vessel by the turntable, and processes the substrates by passing them in order through a plurality of processing regions arranged along the rotation direction of the turntable. [Explanation of symbols]

[0078] S10 Preparation process S20 HF supply process S30 COR process

Claims

1. (a) preparing a substrate having a silicon oxide film on its surface; (b) supplying a first gas containing hydrogen fluoride gas and not containing a basic gas to the surface of the substrate; (c) after the step (b), supplying a second gas containing hydrogen fluoride gas and a basic gas to the surface of the substrate; The substrate processing method comprises:

2. The step (c) is carried out continuously after the step (b) while continuing the supply of the hydrogen fluoride gas. The method of claim 1 .

3. The time period of the step (b) is longer than the time period of the step (c); The method of claim 1 .

4. The step (b) includes reacting the silicon oxide film with the hydrogen fluoride gas to generate silicon tetrafluoride; The step (c) includes reacting the silicon tetrafluoride with the hydrogen fluoride gas and the basic gas to produce ammonium silicofluoride. The method of claim 1 .

5. In the steps (b) and (c), the substrate is maintained at the same temperature. The method of claim 1 .

6. In the step (c), the second gas is supplied along the surface of the substrate. The method of claim 1 .

7. the step (c) includes etching the silicon oxide film such that an etching amount of the silicon oxide film in a central portion of the substrate is greater than an etching amount of the silicon oxide film in an outer periphery of the substrate; The method of claim 1 .

8. The basic gas is ammonia gas. The method of claim 1 .

9. (d) after the step (c), a step of heat treating the substrate at a temperature higher than that in the step of supplying the second gas; The substrate processing method according to claim 1 .

10. a processing vessel for accommodating a substrate; a gas supply unit for supplying a processing gas into the processing vessel; A control unit; Equipped with The control unit is placing a substrate having a silicon oxide film on a surface thereof in the processing chamber; supplying a first gas containing hydrogen fluoride gas and not containing a basic gas to the surface of the substrate accommodated in the processing vessel; supplying a second gas containing hydrogen fluoride gas and a basic gas onto the surface of the substrate accommodated in the processing vessel after the step of supplying the first gas; configured to perform a process including Substrate processing equipment.

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