Method for processing substrate and device for processing substrate

Abstract

To provide a technique for enabling adjustment of the etching selectivity of an oxide film with respect to a nitride film.SOLUTION: The method for processing a substrate includes the steps of: (a) preparing a substrate having a first region in which a nitride film is formed and a second region in which an oxide film is formed; (b) exposing the substrate to plasma generated from a first processing gas containing hydrogen gas and oxygen gas; (c) supplying a second processing gas containing a fluorine-containing gas and a basic gas to the substrate; (d) performing step (b) and step (c) in this order a first number of times; and (e) heating the substrate after step (d).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 has been disclosed in which hydrogen gas and oxygen gas are supplied to a SiCN film formed on the surface of a substrate to oxidize the surface layer of the SiCN film to form an oxide film, and then the oxide film is removed by etching (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-179001 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can adjust the etching selectivity of an oxide film to a nitride film. [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 first region on which a nitride film is formed and a second region on which an oxide film is formed; (b) exposing the substrate to plasma generated from a first processing gas containing hydrogen gas and oxygen gas; (c) supplying a second processing gas containing a fluorine-containing gas and a basic gas to the substrate; (d) performing steps (b) and (c) in this order a first number of times; and (e) heat-treating the substrate after step (d). [Effects of the Invention]

[0006] According to the present disclosure, the etching selectivity of an oxide film to a nitride film can be adjusted. [Brief explanation of the drawings]

[0007] [Figure 1] 3 is a flowchart illustrating a substrate processing method according to an embodiment. [Figure 2] 1 is a vertical cross-sectional view showing a substrate processing apparatus according to an embodiment. [Figure 3] 1 is a horizontal cross-sectional view showing a substrate processing apparatus according to an embodiment. [Figure 4] FIG. 10 is a diagram showing the relationship between the first number of times and the etching amount of the SiO 2 film. [Figure 5] FIG. 10 is a diagram showing the relationship between the first number of times and the etching amount of the SiN film. [Figure 6] FIG. 1 is a diagram showing the etching selectivity of an SiO 2 film to an SiN film. [Figure 7] FIG. 1 is a diagram showing an example of a surface reaction of an SiO 2 film. [Figure 8] FIG. 10 is a diagram showing another example of a surface reaction of an SiO 2 film. DETAILED DESCRIPTION OF THE INVENTION

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

[0009] [Substrate Processing Method] A substrate processing method according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a flowchart showing the substrate processing method according to the embodiment. The substrate processing method according to the embodiment includes steps S1 to S9 shown in Fig. 1.

[0010] In step S1, a substrate is prepared. The substrate is, for example, a silicon wafer. The substrate has a first region on which a nitride film is formed and a second region on which an oxide film is formed. The nitride film is, for example, a film containing silicon (Si) and nitrogen (N). The film containing silicon and nitrogen is, for example, a SiN film or a SiCN film. The nitride film may further contain an element different from silicon and nitrogen. The different element is, for example, oxygen (O), boron (B), or a combination thereof. The nitride film may be a film containing boron and nitrogen. The film containing boron and nitrogen is, for example, a BN film. The oxide film is, for example, a thermal oxide film. The thermal oxide film is, for example, a SiO2 film.

[0011] In step S2, the substrate prepared in step S1 is subjected to radical processing. The radical processing includes exposing the substrate to plasma generated from a first processing gas containing hydrogen gas and oxygen gas. The plasma contains activated species such as oxygen radicals.

[0012] In the radical process, activated species react with the surface layer of the nitride film, oxidizing the surface layer of the nitride film and forming an oxide layer. In the radical process, the thickness of the oxide layer can be adjusted by changing the flow rate ratio of hydrogen gas to oxygen gas contained in the first process gas. For example, the thickness of the oxide layer can be increased by increasing the ratio of the flow rate of oxygen gas to the flow rate of hydrogen gas. The thicker the oxide layer, the greater the amount of etching of the nitride film in step S8.

[0013] In the radical treatment, activated species act on the surface layer of the oxide film, modifying the surface layer of the oxide film to form a modified layer. The modified layer reduces the transformation of the oxide film into reaction products in the COR treatment in step S4. In the radical treatment, the film quality of the modified layer can be adjusted by changing the flow rate ratio of hydrogen gas to oxygen gas contained in the first treatment gas. The film quality may include film density. For example, the film density of the modified layer can be increased by increasing the ratio of the flow rate of oxygen gas to the flow rate of hydrogen gas. The higher the film density of the modified layer, the less the amount of etching of the oxide film in step S8.

[0014] In step S2, the flow rate ratio of the hydrogen gas and the oxygen gas contained in the first process gas may be adjusted so that the etching selectivity ratio of the oxide film to the nitride film falls within a given range.

[0015] The first process gas may further include an inert gas such as argon gas, nitrogen gas, etc. Step S2 may include maintaining the temperature of the substrate at a first temperature, which may be, for example, 80° C. or less.

[0016] In step S3, purging is performed. Purging may include evacuating the processing space where the substrate is processed to remove gas remaining in the processing space. Purging may also include supplying an inert gas such as argon gas or nitrogen gas into the processing space where the substrate is processed to remove gas remaining in the processing space.

[0017] In step S4, a chemical oxide removal (COR) process is performed. The COR process involves supplying a second process gas containing a fluorine-containing gas and a basic gas to the substrate without generating plasma. In the COR process, the fluorine-containing gas and the basic gas react with the oxide layer and oxide film to transform the oxide layer and oxide film, generating a reaction product, ammonium silicofluoride [(NH4)2SiF6]. The fluorine-containing gas is, for example, hydrogen fluoride (HF) gas. The basic gas is, for example, ammonia (NH3) gas. The second process gas may further contain an inert gas, such as argon gas or nitrogen gas. Step S4 may also include maintaining the temperature of the substrate at a second temperature. The second temperature is, for example, between 50°C and 100°C. The second temperature may be the same as the first temperature. In this case, the radical process and the COR process can be performed consecutively without changing the temperature. This improves productivity.

[0018] In step S5, purging is performed, which may be the same as the purging in step S3.

[0019] In step S6, it is determined whether steps S2 to S5 have been performed in this order a first number of times. If the number of times has not reached the first number (NO in step S6), steps S2 to S5 are performed again. If the number of times has reached the first number of times (YES in step S6), the process proceeds to step S7. In this way, by repeating steps S2 to S5 in this order until the number of times reaches the first number of times, the thickness of the oxide layer formed on the surface layer of the nitride film and the film quality of the modified layer formed on the surface layer of the oxide film are adjusted. As a result, the etching selectivity of the oxide film to the nitride film can be adjusted to fall within a given range. The first number of times may be one, two, or more.

[0020] In step S7, the temperature of the substrate is increased from the second temperature to a third temperature, which is higher than the second temperature, for example, 200° C. or higher.

[0021] In step S8, the substrate is heat-treated. The heat treatment includes heat-treating the substrate in an atmosphere of an inert gas such as argon gas or nitrogen gas while maintaining the temperature of the substrate at a third temperature. During the heat treatment, ammonium silicofluoride, which is a reaction product, is sublimated and removed from the substrate.

[0022] In step S9, purging is performed. The purging in step S9 may be the same as the purging in step S3. After purging in step S9, the process ends.

[0023] As described above, according to the substrate processing method of the embodiment, a substrate having a first region where a nitride film is formed and a second region where an oxide film is formed is prepared, then the substrate is subjected to a first number of radical treatments and a COR treatment in this order, and then the substrate is heat-treated. In this case, by changing the first number of treatments, the thickness of the oxide layer formed on the surface of the nitride film and the film quality of the modified layer formed on the surface of the oxide film can be adjusted. Therefore, the etching selectivity of the oxide film to the nitride film can be adjusted.

[0024] The etching selectivity of an oxide film to a nitride film can also be adjusted by changing the COR processing conditions, such as the temperature, the flow rate ratio of hydrogen fluoride gas to ammonia gas, and the pressure. However, the adjustment range of the etching selectivity by changing the COR processing conditions is small. In contrast, the substrate processing method according to the embodiment allows a wide adjustment range of the etching selectivity of an oxide film to a nitride film.

[0025] In an embodiment, steps S2 to S9 may be performed in the same processing vessel. In this case, the radical treatment, COR treatment, and heat treatment can be performed in one processing vessel. However, some of steps S2 to S9 may be performed in different processing vessels. For example, steps S8 and S9 may be performed in a processing vessel different from steps S2 to S6. In this case, step S7 can be omitted.

[0026] The substrate processing method according to the embodiment may be performed in a processing chamber that accommodates a plurality of substrates in a shelf-like arrangement. In this case, multiple substrates can be processed at once, thereby improving productivity.

[0027] [Substrate Processing Apparatus] A substrate processing apparatus 100 according to an embodiment will be described with reference to Figures 2 and 3. Figure 2 is a vertical cross-sectional view showing the substrate processing apparatus 100 according to an embodiment. Figure 3 is a horizontal cross-sectional view showing the substrate processing apparatus 100 according to an embodiment. As shown in Figures 2 and 3, the substrate processing apparatus 100 includes a processing chamber 1, a gas supply unit 20, a plasma generation unit 30, an exhaust unit 40, a heating unit 50, and a control unit 90.

[0028] The processing vessel 1 has a vertical cylindrical shape with a ceiling and an open bottom end. The processing vessel 1 is made of, for example, quartz. A ceiling plate 2 is provided near the upper end of the processing vessel 1, and the area below the ceiling plate 2 is sealed. The ceiling plate 2 is made of, for example, quartz. A cylindrical metal manifold 3 is connected to the opening at the lower end of the processing vessel 1 via a sealing member 4. The sealing member 4 is, for example, an O-ring.

[0029] The manifold 3 supports the lower end of the processing vessel 1. The boat 5 is inserted into the processing vessel 1 from below the manifold 3. The boat 5 holds multiple (e.g., 25 to 150) substrates W approximately horizontally with spacing between them in the vertical direction. The boat 5 is made of, for example, quartz. The boat 5 has, for example, three support columns 6, and the multiple substrates W are supported by grooves formed in the support columns 6.

[0030] The boat 5 is placed on a rotating table 8 via a heat-insulating tube 7. The heat-insulating tube 7 is made of, for example, quartz. The heat-insulating tube 7 suppresses heat radiation from the opening at the lower end of the manifold 3. The rotating table 8 is supported on a rotating shaft 10. The opening at the lower end of the manifold 3 is opened and closed by a lid 9. The lid 9 is made of, for example, a metal material such as stainless steel. The rotating shaft 10 passes through the lid 9.

[0031] A magnetic fluid seal 11 is provided at the penetration portion of the rotating shaft 10. The magnetic fluid seal 11 airtightly seals the rotating shaft 10 and rotatably supports it. A seal member 12 is provided between the periphery of the lid 9 and the lower end of the manifold 3 to maintain airtightness inside the processing vessel 1. The seal member 12 is, for example, an O-ring.

[0032] The rotating shaft 10 is attached to the tip of an arm 13 supported by an elevator mechanism such as a boat elevator. When the arm 13 moves up and down, the boat 5, the heat-retaining cylinder 7, the turntable 8, and the lid 9 move up and down together with the rotating shaft 10, and are inserted into and removed from the processing vessel 1.

[0033] The gas supply unit 20 supplies various process gases into the process vessel 1. The gas supply unit 20 includes, for example, a gas nozzle 21, a gas nozzle 22, a gas nozzle 23, and a gas nozzle 24. The gas nozzle 21, the gas nozzle 22, the gas nozzle 23, and the gas nozzle 24 are made of, for example, quartz. The gas supply unit 20 may further include another gas nozzle.

[0034] The gas nozzle 21 has an L-shape that penetrates the sidewall of the manifold 3 inward, bends upward, and extends vertically. The vertical portion of the gas nozzle 21 is provided inside the processing vessel 1. The vertical portion of the gas nozzle 21 has multiple gas holes 21a. The multiple gas holes 21a are provided at predetermined intervals along the extension direction of the gas nozzle 21. Each gas hole 21a is oriented toward the center CT of the processing vessel 1, for example.

[0035] A supply path L1 is connected to the gas nozzle 21. An oxygen gas supply source G1, a mass flow controller F1, and an on-off valve V1 are provided on the supply path L1, in that order from upstream to downstream in the gas flow direction. The supply timing of the oxygen gas from the supply source G1 is controlled by the on-off valve V1, and the mass flow controller F1 adjusts the flow rate to a predetermined value. The oxygen gas flows from the supply path L1 into the gas nozzle 21 and is ejected horizontally from multiple gas holes 21a toward the center CT of the processing chamber 1.

[0036] Gas nozzle 22 has an L-shape that penetrates the sidewall of manifold 3 inward, bends upward, and extends vertically. A vertical portion of gas nozzle 22 is provided inside processing vessel 1. A plurality of gas holes 22a are provided in the vertical portion of gas nozzle 22. The plurality of gas holes 22a are provided at predetermined intervals along the extension direction of gas nozzle 22. Each gas hole 22a is oriented toward, for example, the center CT of processing vessel 1.

[0037] A supply path L2 is connected to the gas nozzle 22. A hydrogen fluoride gas supply source G2, a mass flow controller F2, and an on-off valve V2 are provided on the supply path L2, in this order from upstream to downstream in the gas flow direction. Hydrogen fluoride gas is an example of a fluorine-containing gas. The supply timing of the hydrogen fluoride gas from the supply source G2 is controlled by the on-off valve V2, and the mass flow controller F2 adjusts the flow rate to a predetermined value. The hydrogen fluoride gas flows from the supply path L2 into the gas nozzle 22 and is ejected horizontally from multiple gas holes 22a toward the center CT of the processing chamber 1.

[0038] The gas nozzle 23 has an L-shape that penetrates the sidewall of the manifold 3 inward, bends upward, and extends vertically. The vertical portion of the gas nozzle 23 is provided in the plasma generation space P. The vertical portion of the gas nozzle 23 is provided with a plurality of gas holes 23a. The plurality of gas holes 23a are provided at predetermined intervals along the extension direction of the gas nozzle 23. Each gas hole 23a is oriented toward the center CT of the processing vessel 1, for example.

[0039] A supply path L3 is connected to the gas nozzle 23. A hydrogen gas supply source G3, a mass flow controller F3, and an on-off valve V3 are provided on the supply path L3, in that order from upstream to downstream in the gas flow direction. The supply timing of the hydrogen gas from the supply source G3 is controlled by the on-off valve V3, and the flow rate is adjusted to a predetermined value by the mass flow controller F3. The hydrogen gas flows from the supply path L3 into the gas nozzle 23 and is ejected horizontally from multiple gas holes 23a toward the center CT of the processing chamber 1.

[0040] A supply path L4 is connected to the gas nozzle 23. The supply path L4 may be connected to the supply path L3 downstream of the on-off valve V3. An ammonia gas supply source G4, a mass flow controller F4, and an on-off valve V4 are provided on the supply path L4, in this order from upstream to downstream in the gas flow direction. Ammonia gas is an example of a basic gas. The supply timing of the ammonia gas from the supply source G4 is controlled by the on-off valve V4, and the flow rate is adjusted to a predetermined value by the mass flow controller F4. The ammonia gas flows from the supply path L4 into the gas nozzle 23 and is discharged horizontally toward the center CT of the processing vessel 1 through multiple gas holes 23a.

[0041] The gas nozzle 24 has a straight pipe shape that extends horizontally and penetrates the sidewall of the manifold 3. The tip of the gas nozzle 24 is provided inside the processing vessel 1. The tip of the gas nozzle 24 is open.

[0042] A supply path L5 is connected to the gas nozzle 24. An argon gas supply source G5, a mass flow controller F5, and an on-off valve V5 are provided on the supply path L5, in this order from upstream to downstream in the gas flow direction. Argon gas is an example of an inert gas. The supply timing of the argon gas from the supply source G5 is controlled by the on-off valve V5, and the mass flow controller F5 adjusts the flow rate to a predetermined value. The argon gas flows from the supply path L5 into the gas nozzle 24 and is discharged into the processing chamber 1 from an opening at the tip.

[0043] The plasma generating unit 30 is provided on a part of the sidewall of the processing vessel 1. The plasma generating unit 30 generates plasma from hydrogen gas and ammonia gas supplied from the gas nozzle 23. The plasma generating unit 30 includes a plasma partition wall 32, a pair of plasma electrodes 33, a power supply line 34, an RF power supply 35, and an insulating protective cover 36.

[0044] The plasma compartment wall 32 is airtightly welded to the outer wall of the processing vessel 1. The plasma compartment wall 32 is made of, for example, quartz. The plasma compartment wall 32 has a concave cross section and covers an opening 31 formed in the side wall of the processing vessel 1. The opening 31 is formed to be elongated in the vertical direction so that it can cover all of the substrates W supported by the boat 5 in the vertical direction. The plasma compartment wall 32 defines a plasma generation space P, which is an inner space that communicates with the inside of the processing vessel 1.

[0045] The pair of plasma electrodes 33 each have an elongated shape and are arranged facing each other in the vertical direction on the outer surfaces of both sides of the plasma compartment wall 32. A power supply line 34 is connected to the lower end of each plasma electrode 33.

[0046] The power supply line 34 electrically connects each plasma electrode 33 to the RF power supply 35. For example, one end of the power supply line 34 is connected to the lower end, which is the side of the short side of each plasma electrode 33, and the other end is connected to the RF power supply 35.

[0047] The RF power supply 35 is electrically connected to the lower end of each plasma electrode 33 via a power supply line 34. The RF power supply 35 supplies RF power of, for example, 13.56 MHz to the pair of plasma electrodes 33. This applies the RF power to the plasma generation space P defined by the plasma partition wall 32.

[0048] The insulating protective cover 36 is attached to the outside of the plasma compartment wall 32 so as to cover the plasma compartment wall 32. A coolant passage (not shown) is provided inside the insulating protective cover 36. The plasma electrode 33 is cooled by flowing a coolant such as cooled nitrogen gas through the coolant passage. A shield (not shown) may be provided between the plasma electrode 33 and the insulating protective cover 36 so as to cover the plasma electrode 33. The shield is made of a good conductor such as metal and is electrically grounded.

[0049] The exhaust unit 40 has an exhaust port 41. The exhaust port 41 is provided in a sidewall portion of the processing vessel 1. The exhaust port 41 is provided at a position opposite the opening 31. The exhaust port 41 is formed to be elongated in the vertical direction corresponding to the boat 5. A cover member 42 having a U-shaped cross section is attached to the portion of the processing vessel 1 corresponding to the exhaust port 41 so as to cover the exhaust port 41. The cover member 42 extends upward along the sidewall of the processing vessel 1. An exhaust pipe 43 is connected to the lower part of the cover member 42. A pressure adjustment valve 44 and a vacuum pump 45 are provided in the exhaust pipe 43, in this order from upstream to downstream in the gas flow direction. The pressure adjustment valve 44 adjusts the pressure inside the processing vessel 1. The vacuum pump 45 exhausts gas inside the processing vessel 1.

[0050] The heating unit 50 includes a heater 51. The heater 51 has a cylindrical shape that surrounds the processing vessel 1 on the radially outer side of the processing vessel 1. The heater 51 heats the entire periphery of the processing vessel 1, thereby heating each substrate W accommodated in the processing vessel 1.

[0051] The control unit 90 is an electronic circuit such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), ASIC (Application Specific Integrated Circuit), etc. The control unit 90 executes various control operations described in this specification by executing instruction codes stored in a memory or by being a circuit designed for a specific application.

[0052] [Operation of the Substrate Processing Apparatus] The operation of the substrate processing apparatus 100 when the substrate processing method according to the embodiment is performed in the substrate processing apparatus 100 will be described.

[0053] First, the control unit 90 raises the arm 13 to load the boat 5 holding the substrates W into the processing vessel 1, and then airtightly closes the opening at the bottom of the processing vessel 1 with the lid 9. Each substrate W has a first region on which a nitride film is formed and a second region on which an oxide film is formed.

[0054] Next, the control unit 90 controls each unit of the substrate processing apparatus 100 to perform steps S2 to S9 in the substrate processing method described above. The control unit 90 adjusts the thickness of the oxide layer formed on the surface of the nitride film and the film quality of the modified layer formed on the surface of the oxide film by changing the first number of times in step S6. This allows the etching selectivity of the oxide film to the nitride film to be adjusted.

[0055] Next, the control unit 90 increases the pressure inside the processing vessel 1 to atmospheric pressure, and decreases the temperature inside the processing vessel 1 to the unloading temperature, and then lowers the arm 13 to unload the boat 5 from the processing vessel 1. This completes the processing of the multiple substrates W.

[0056] 〔experiment〕 First, a substrate having a SiO2 film on its surface and a substrate having a SiN film on its surface were prepared. Next, the prepared substrates were placed in the processing chamber 1 of the substrate processing apparatus 100, and steps S2 to S9 of the substrate processing method described above were performed in the processing chamber 1. In step S6, the first number of times was changed. The first number of times was 1, 3, 5, and 10. In step S2, the flow rate of each gas contained in the first processing gas was changed. The flow rate of each gas was as follows:

[0057] ·Condition A1: H2 / O2 / N2=0sccm / 0sccm / 2450sccm ·Condition A2: H2 / O2 / N2=1400sccm / 500sccm / 550sccm ·Condition A3: H2 / O2 / N2=2000sccm / 8000sccm / 550sccm

[0058] The conditions for the radical treatment (step S2), the COR treatment (step S4), and the heat treatment (step S8) are as follows.

[0059] (radical treatment) Substrate temperature: 65℃ Time: 10 minutes RF power:ON (COR processing) Substrate temperature: 65℃ Time: 1 minute RF power: OFF Second process gas: hydrogen fluoride gas / ammonia gas / nitrogen gas = 300 sccm / 300 sccm / 550 sccm (Heat treatment) Substrate temperature: 300℃ Treatment atmosphere: Nitrogen gas

[0060] Next, the etching amount of the SiO2 film and the etching amount of the SiN film were measured.

[0061] Fig. 4 is a diagram showing the relationship between the first number of times and the etching amount of the SiO2 film. In Fig. 4, the horizontal axis represents the first number of times [times], and the vertical axis represents the etching amount of the SiO2 film [nm]. In Fig. 4, circles represent the results when radical treatment was performed under condition A1, squares represent the results when radical treatment was performed under condition A2, and triangles represent the results when radical treatment was performed under condition A3.

[0062] As shown in Figure 4, when comparing the same first number of times, the etching amount of the SiO2 film is in the following order: Condition A1 > Condition A2 > Condition A3. This result shows that performing radical treatment on the SiO2 film reduces the etching amount of the SiO2 film. It also shows that the etching amount of the SiO2 film decreases as the ratio of the oxygen gas flow rate to the hydrogen gas flow rate contained in the first process gas increases.

[0063] As shown in Figure 4, under condition A2, the etching amount of the SiO2 film increases as the first number of times increases. This result shows that the etching amount of the SiO2 film can be controlled by changing the first number of times. Specifically, the etching amount of the SiO2 film increases as the first number of times increases.

[0064] Fig. 5 is a diagram showing the relationship between the first number of times and the etching amount of the SiN film. In Fig. 5, the horizontal axis represents the first number of times (times), and the vertical axis represents the etching amount of the SiN film (nm). In Fig. 5, circles represent the results when radical treatment was performed under condition A1, squares represent the results when radical treatment was performed under condition A2, and triangles represent the results when radical treatment was performed under condition A3.

[0065] As shown in Figure 5, when comparing the same first number of times, the etching amount of the SiN film is in the following order: Condition A1 < Condition A2 < Condition A3. This result shows that performing radical treatment on the SiN film increases the etching amount of the SiN film. It also shows that the etching amount of the SiN film increases as the ratio of the oxygen gas flow rate to the hydrogen gas flow rate contained in the first processing gas increases.

[0066] As shown in Figure 5, under conditions A2 and A3, the etching amount of the SiN film increases as the first number of times increases. This result shows that the etching amount of the SiN film can be controlled by changing the first number of times. Specifically, the etching amount of the SiN film increases as the first number of times increases.

[0067] Fig. 6 is a diagram showing the etching selectivity of an SiO2 film to an SiN film. In Fig. 6, the horizontal axis indicates the conditions, and the vertical axis indicates the etching selectivity of a silicon oxide film to a silicon nitride film (SiO2 / SiN selectivity) when the first number of times is set to 10.

[0068] 6, the etching selectivity of the silicon oxide film to the silicon nitride film was 23.5 under condition A1, 3.4 under condition A2, and 0 under condition A3. This result indicates that the etching selectivity of the oxide film to the nitride film can be adjusted by changing the flow rate ratio of the hydrogen gas and the oxygen gas contained in the first process gas.

[0069] [Surface reaction of SiO2 film] The surface reaction of the SiO2 film will be explained with reference to Figures 7 and 8. Below, we will explain the reaction mechanism that is thought to occur on the surface of the SiO2 film when a substrate having an SiO2 film on its surface is repeatedly subjected to radical treatment and COR treatment in this order.

[0070] Fig. 7 shows an example of the surface reaction of an SiO2 film. Fig. 7 shows the surface reaction of an SiO2 film when a radical treatment and a COR treatment are repeatedly performed in this order on a substrate having an SiO2 film on its surface. Fig. 7 shows the case where the radical treatment is performed under the condition A2 of the above-mentioned experiment.

[0071] As shown in FIG. 7(a), when a substrate 101 having a SiO2 film 102 on its surface is subjected to radical processing under condition A2, a modified layer 110 is formed on the surface of the SiO2 film 102. As a result, the surface of the SiO2 film 102 is covered with the modified layer 110. When the COR processing is performed with the surface of the SiO2 film 102 covered with the modified layer 110, the modified layer 110 prevents hydrogen fluoride (HF) and ammonia (NH3) contained in the first processing gas from reaching the SiO2 film 102. As a result, only a portion of the fluorine (HF) and ammonia (NH3) reaches the SiO2 film 102. Therefore, the SiO2 film 102 is less likely to be transformed into an ammonium silicofluoride layer 103. For example, as shown in FIG. 7(b), a portion of the surface of the SiO2 film 102 is transformed into an ammonium silicofluoride layer 103.

[0072] As shown in FIG. 7(c), when the radical treatment and the COR treatment are repeatedly performed on the substrate 101 in this order, cracks 104 are generated in the modified layer 110 at some point. This allows hydrogen fluoride (HF) and ammonia (NH) to reach the SiO2 film 102 through the cracks 104, facilitating the transformation of the SiO2 film 102 into an ammonium silicofluoride layer 103. As a result, as shown in FIG. 7(d), the thickness of the ammonium silicofluoride layer 103 increases. As a result, when the substrate 101 is heat-treated, the ammonium silicofluoride layer 103 is etched.

[0073] When the radical treatment is performed under condition A2, cracks 104 are unlikely to occur in the modified layer 110 when the number of repetitions (first number) of the radical treatment and the COR treatment is small. For this reason, it is thought that etching of the SiO2 film 102 hardly progresses when the first number of times is small (three or less in the example of FIG. 4), but etching of the SiO2 film 102 begins to progress when the first number of times exceeds a certain number (three in the example of FIG. 4).

[0074] Fig. 8 shows another example of the surface reaction of an SiO2 film. Fig. 8 shows the surface reaction of an SiO2 film when a radical treatment and a COR treatment are repeatedly performed in this order on a substrate having an SiO2 film on its surface. Fig. 8 shows the case where the radical treatment is performed under the condition A3 of the above-mentioned experiment.

[0075] As shown in FIG. 8(a), when the substrate 101 having a SiO2 film 102 on its surface is subjected to radical processing under condition A3, a modified layer 120 is formed on the surface of the SiO2 film 102. As a result, the surface of the SiO2 film 102 is covered with the modified layer 120. Condition A3 has a higher ratio of the flow rate of oxygen gas to the flow rate of hydrogen gas than condition A2. Therefore, it is considered that the modified layer 120 has a higher film density than the modified layer 110. When the COR processing is performed with the surface of the SiO2 film 102 covered with the modified layer 120, the modified layer 120 prevents hydrogen fluoride (HF) and ammonia (NH3) contained in the first processing gas from reaching the SiO2 film 102. When the surface of the SiO2 film 102 is covered with the modified layer 120, fluorine (HF) and ammonia (NH3) are less likely to reach the SiO2 film 102 than when the surface of the SiO2 film is covered with the modified layer 110. Therefore, when the surface of the SiO2 film 102 is covered with the modified layer 120, the SiO2 film 102 is less likely to change into the ammonium silicofluoride layer 103 than when the surface of the SiO2 film is covered with the modified layer 110. For example, as shown in FIG. 8(b), the SiO2 film 102 is hardly changed into the ammonium silicofluoride layer 103. As a result, even when the substrate 101 is heat-treated, the SiO2 film 102 is hardly etched.

[0076] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive, and the above-described embodiments may be omitted, substituted, or modified in various ways 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 multiple substrates at once, but the present disclosure is not limited to this. For example, the substrate processing apparatus may be a single-wafer-type apparatus that processes substrates one by one. [Explanation of symbols]

[0078] 1. Processing container 20 Gas supply unit 90 Control Unit 100 Substrate processing apparatus

Claims

1. (a) providing a substrate having a first region on which a nitride film is formed and a second region on which an oxide film is formed; (b) exposing the substrate to a plasma generated from a first process gas comprising hydrogen gas and oxygen gas; (c) supplying a second process gas to the substrate, the second process gas comprising a fluorine-containing gas and a basic gas; (d) performing steps (b) and (c) in this order a first number of times; (e) heat treating the substrate after step (d); A substrate processing method comprising:

2. The step (b) includes oxidizing a surface layer of the nitride film to form an oxide layer. The substrate processing method according to claim 1 .

3. The step (c) includes converting the oxide layer into a reaction product; The step (e) includes removing the reaction product by sublimation. The substrate processing method according to claim 2 .

4. The step (b) includes modifying the oxide film to form a modified layer. The substrate processing method according to claim 1 .

5. the step (b) includes adjusting a flow rate ratio of the hydrogen gas to the oxygen gas so that an etching selectivity of the oxide film to the nitride film falls within a given range; The substrate processing method according to claim 1 .

6. the step (d) includes adjusting the first number of times so that an etching selectivity of the oxide film to the nitride film falls within a given range; The substrate processing method according to claim 1 .

7. step (b) includes maintaining the temperature of the substrate at a first temperature; step (c) includes maintaining the temperature of the substrate at a second temperature; The second temperature is the same as the first temperature. The substrate processing method according to claim 1 .

8. step (e) includes maintaining the temperature of the substrate at a third temperature; The third temperature is higher than the second temperature. The substrate processing method according to claim 7 .

9. The step (c) is carried out in the same processing vessel as the step (b). The substrate processing method according to claim 1 .

10. The nitride film is a SiN film, a SiCN film, or a BN film. The substrate processing method according to claim 1 .

11. The oxide film is a thermal oxide film. The substrate processing method according to claim 1 .

12. The thermal oxide film is made of SiO ２ It is a membrane, The substrate processing method according to claim 11 .

13. A processing vessel; a gas supply unit that supplies a processing gas into the processing vessel; A control unit; Equipped with The control unit (a) providing a substrate having a first region on which a nitride film is formed and a second region on which an oxide film is formed; (b) exposing the substrate to a plasma generated from a first process gas comprising hydrogen gas and oxygen gas; (c) supplying a second process gas to the substrate, the second process gas comprising a fluorine-containing gas and a basic gas; (d) performing steps (b) and (c) in this order a first number of times; (e) heat treating the substrate after step (d); To execute Substrate processing equipment.

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