Substrate processing method and substrate processing device

Abstract

[Problem] To etch silicon nitride while securing selectivity regarding silicon without using oxygen. [Solution] A substrate processing method includes a step for providing a substrate on which a silicon film and a silicon nitride film are formed in a processing space. In the processing space maintained in a vacuum atmosphere, processing gas, containing at least ammonia gas and fluorine-containing gas, is used on the substrate in a processing container, and when executing exhausting for maintaining the processing space in the vacuum atmosphere, the ammonia gas is supplied to the processing space without first supplying the fluorine-containing gas to the processing space, and then the fluorine-containing gas is supplied to the processing space without supplying the ammonia gas to the processing space so as to subject the substrate to etching processing, thereby etching the silicon nitride film while securing selectivity regarding the silicon film.

Description

Substrate processing method and substrate processing apparatus

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

[0002] Conventionally, various substrate processing methods have been developed for selectively etching a silicon (Si) film and a silicon nitride (SiN) film formed on a wafer as a substrate. For example, a substrate processing method is known in which, prior to etching the SiN film, the wafer is subjected to an oxygen-containing plasma treatment to oxidize the surface of the Si film and form a modified layer, making the Si film difficult to etch (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2020-25070

[0004] The technique according to the present disclosure etches silicon nitride without using oxygen while ensuring a selectivity to silicon.

[0005] One aspect of the technology disclosed herein is a substrate processing method for etching the silicon nitride film while ensuring a selectivity to the silicon film, the method comprising the steps of: placing a substrate, on which a silicon film and a silicon nitride film are formed, in a processing space; applying a processing gas containing at least ammonia gas and a fluorine-containing gas to the substrate in the processing vessel in the processing space maintained in a vacuum atmosphere; and, when exhausting is performed to maintain the processing space in a vacuum atmosphere, first supplying the ammonia gas to the processing space without supplying the fluorine-containing gas to the processing space, and then supplying the fluorine-containing gas to the processing space without supplying the ammonia gas to the processing space, thereby etching the substrate.

[0006] According to the technique of the present disclosure, silicon nitride can be etched without using oxygen while ensuring a selectivity to silicon.

[0007] FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a substrate processing apparatus in an embodiment of the technology disclosed herein. FIG. 2 is a flowchart showing an example of a SiN etching process as a substrate processing method according to the present embodiment, which is performed in the etching apparatus of FIG. 1. FIG. 3 is a process diagram of the example of the SiN etching process of FIG. 2. FIG. 4 is a process diagram of the example of the SiN etching process of FIG. 2. FIG. 4 is a flowchart showing a modified example of the SiN etching process performed in the etching apparatus of FIG. 1. FIG. 5 is a process diagram of the example of the SiN etching process of FIG. 4. FIG. 5 is a process diagram of the example of the SiN etching process of FIG. 4. FIG. 6 is a graph showing an example of the etching amount of a Si film and a SiN film in Examples and Comparative Examples 1 to 3.

[0008] However, as described above, when a wafer is subjected to an oxygen-containing plasma treatment to selectively etch a SiN film relative to a Si film, a modified layer is formed on the surface of the Si film, resulting in loss of the Si film by the amount of the modified layer. Furthermore, it becomes necessary to remove the modified layer, which is an oxide film, in a subsequent process, but this requires a separate etching process, which reduces throughput.

[0009] Furthermore, when a wafer is subjected to an oxygen-containing plasma treatment, a thin modified layer may be formed on the surface of the SiN film, which inhibits etching of the SiN film, reduces the etching rate of the SiN film, and also reduces throughput.

[0010] In contrast, the technology according to the present disclosure is ammonia (NH ３ By using the SiO 2 gas, the SiN film can be etched without using oxygen while ensuring a selectivity to the Si film, thereby suppressing a decrease in throughput.

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present disclosure will now be described with reference to the accompanying drawings, in which: Fig. 1 is a cross-sectional view schematically illustrating an example of the configuration of a substrate processing apparatus according to an embodiment of the present disclosure;

[0012] 1, an etching apparatus 10 serving as a substrate processing apparatus includes a sealed processing vessel 11 that accommodates a wafer W (substrate). The processing vessel 11 is made of, for example, aluminum (Al) or an Al alloy, and has an open upper end that is closed by a lid 12 that forms a ceiling. A sidewall 13 of the processing vessel 11 is provided with a loading / unloading port 14 for the wafer W, and the loading / unloading port 14 is opened and closed by a gate valve 15 that is a slide valve.

[0013] A stage 16 on which a wafer W is horizontally placed is disposed at the bottom of the interior of the processing vessel 11. The stage 16 is raised and lowered by an elevating mechanism 17 provided outside the processing vessel 11. The stage 16 is generally cylindrical and includes a mounting plate 18 on which the wafer W is directly placed and a base block 19 that supports the mounting plate 18. A temperature adjustment mechanism 20 for adjusting the temperature of the placed wafer W is provided inside the mounting plate 18. The temperature adjustment mechanism 20 includes, for example, a conduit (not shown) through which a temperature adjustment medium (e.g., water or Galden) circulates, and adjusts the temperature of the wafer W by performing heat exchange between the temperature adjustment medium flowing through the conduit and the wafer W. The stage 16 also includes a plurality of elevating pins (not shown) that can be protruded and retracted from the upper surface of the mounting plate 18 and are used to load and unload the wafer W into and from the processing vessel 11.

[0014] The interior of the processing vessel 11 is divided by a partition plate 21 into an upper plasma generation space P and a lower processing space S. The plasma generation space P is a space where plasma is generated, and the processing space S is a space where plasma processing is performed on the wafer W. Outside the processing vessel 11, a fluorine-containing gas to be converted into plasma, such as nitrogen trifluoride (NF), is introduced. ３ A first gas supply unit 22 is provided to supply a gas that is not converted into plasma, such as an etchant, ammonia (NH ３ ) gas and inert gases such as argon (Ar) gas and nitrogen (N ２) gas to the processing space S instead of the plasma generating space P. In this embodiment, the various gases supplied to the plasma generating space P and the processing space S are collectively referred to as processing gas. ３ In addition to the gas, an inert gas such as Ar gas or N ２ A gas may be supplied to the processing vessel 11. An exhaust mechanism 24 is connected to the bottom of the processing vessel 11. The exhaust mechanism 24 has a vacuum pump, and exhausts the inside of the processing vessel 11, reducing the pressure inside the processing vessel 11 and maintaining a vacuum atmosphere.

[0015] Furthermore, a ring-shaped RF (radio frequency) antenna 25 for generating inductively coupled plasma in the plasma generation space P is disposed on the lid 12, which serves as the ceiling of the processing vessel 11. The RF antenna 25 is connected to a radio frequency power supply 27 via a matching box 26. The radio frequency power supply 27 outputs radio frequency power at a frequency (e.g., 13.56 MHz or higher) suitable for generating plasma by inductively coupled radio frequency discharge. The matching box 26 has a variable reactance matching circuit (not shown) for matching the impedance on the radio frequency power supply 27 side with the impedance on the load (RF antenna 25 and plasma) side. The lid 12 is formed, for example, from a circular quartz plate and functions as a dielectric window. In this manner, the etching apparatus 10 is configured as an inductively coupled plasma etching apparatus using the RF antenna 25.

[0016] The partition plate 21 inside the processing vessel 11 includes at least two plate-shaped members 28 and 29. The plate-shaped members 28 and 29 have a shape corresponding to the horizontal cross-sectional shape of the processing vessel 11, e.g., a substantially circular shape in a plan view. The plate-shaped members 28 and 29 are arranged so as to overlap each other from the plasma generation space P toward the processing space S. A spacer 30 is arranged between the plate-shaped members 28 and 29 to maintain a constant distance between them. A plurality of slits (not shown) are formed in each of the plate-shaped members 28 and 29, penetrating them in the overlapping direction. The slits are arranged parallel to each other, and the slits 47 in the plate-shaped members 28 and 29 do not overlap each other when the partition plate 21 is viewed from the processing space S. Note that the plate-shaped members 28 and 29 may have a plurality of through holes instead of the slits.

[0017] The partition plate 21 has the above-mentioned slit arrangement structure (labyrinth structure), and thus functions as a so-called ion trap that suppresses the transmission of ions in the plasma generated in the plasma generation space P from the plasma generation space P to the processing space S. Therefore, radicals in the plasma are selectively transmitted from the plasma generation space P to the processing space S.

[0018] A heat shield 31 is provided below the partition plate 21 so as to face the wafer W. A plurality of slits (not shown) are formed in the heat shield 31, penetrating from the plasma generation space P toward the processing space S. Each slit is provided so as to face each slit in the plate-like member 29. Radicals in the plasma that have passed through the partition plate 21 pass through these slits and reach the processing space S. Note that a plurality of through holes with increasing diameter may be formed instead of the slits.

[0019] Furthermore, a large number of gas discharge ports (not shown) are formed between the slits in the heat shield plate 31. These gas discharge ports are distributed so as to face the wafer W placed on the stage 16. Each gas discharge port is connected to the second gas supply unit 23, and NH ３The NH 4 gas and the inert gas are uniformly discharged toward the processing space S. ３ It functions as a shower head for discharging gases and inert gases. ３ The gas or inert gas may be supplied directly to the processing space S from the sidewall 13 of the processing vessel 11 .

[0020] Fig. 2 is a flowchart showing an example of a SiN etching process as a substrate processing method according to the present embodiment, which is performed by the etching apparatus 10 of Fig. 1, and Figs. 3A to 3C are each an example of a process diagram of the SiN etching process of Fig. 2. The wafer W to be subjected to the SiN etching process may be any wafer having a silicon (Si) film and a silicon nitride (SiN) film formed thereon. However, for ease of understanding, Figs. 3A to 3C each show an example in which the wafer W is a blanket wafer. On the surface of this blanket wafer W, a Si film 32 made of polysilicon and a SiN film 33 formed by ALD (Atomic Layer Deposition) are disposed.

[0021] First, the wafer W is carried into the processing chamber 11 of the etching apparatus 10 (step S21) and placed on the stage 16. Then, N 2 is supplied as a pressure adjusting gas from the second gas supply unit 23. ２ Gas is supplied into the processing chamber 11, and the temperature of the wafer W is adjusted and stabilized at a relatively low temperature of, for example, 15° C. by the temperature adjustment mechanism 20.

[0022] Next, the inside of the processing chamber 11 is evacuated by the exhaust mechanism 24, and the inside of the processing chamber 11 is set to a vacuum atmosphere, for example, 100 mTorr. After that, NF ３ The second gas supply unit 23 supplies NH 4 to the processing space S. ３ Gas, Ar gas or N ２ At this time, high frequency power is supplied from the high frequency power supply 27 to the RF antenna 25, and the NF ３The gas is excited to generate fluorine (F) plasma (step S23). Then, F radicals in the F plasma generated in the plasma generation space P are selectively transmitted into the processing space S. Therefore, as shown in FIG. 3A, in the processing space S, NH ３ The molecules (white circles in the figure) and F radicals (black circles in the figure) are mixed together.

[0023] where Si, NH ３ and F radicals form a protective layer of silicon-containing by-products (e.g., ammonia fluoride silicon (AFS, (NH ４ ) ２ SiF ４ The mechanism by which AFS is generated is the chemical reaction shown in the following formula (1), but the generation energy when AFS is generated from Si is relatively low. ３ The molecules adhere to the surface of the Si film 32, and when the F radicals reach there, Si, NH ３ The and F radicals immediately undergo a chemical reaction represented by the following formula (1) to form an AFS thin film 34. That is, the surface of the Si film 32 is covered with an AFS thin film 34 (FIG. 3B).

[0024] 3Si + 12F ＊ + 8NH ３ → 3 (NH ４ ) ２ SiF ４ + N ２ …(1)

[0025] On the other hand, the energy required for AFS generation from SiN is relatively high, so NH ３ The molecules adhere to the surface of the SiN film 33, and even if the F radicals reach there, SiN, NH ３ The F radicals do not immediately undergo a chemical reaction, that is, the surface of the SiN film 33 is unlikely to be covered with a thin film of AFS.

[0026] The SiN in the SiN film 33 that is not covered with the thin film of AFS and the F radicals undergo a chemical reaction shown in the following formula (2), to form silicon tetrafluoride (SiF ４ At this time, NH 3 adhering to the surface of the SiN film 33 ３The molecule acts as a catalyst and promotes the chemical reaction shown in formula (2) below.

[0027] 2SiN + 8F ＊ + NH ３ → 2SiF ４ ↑ + N ２ + NH ３ …(2)

[0028] Here, SiF ４ Since the boiling point of SiF under atmospheric pressure is -95.5°C, ４ is easily sublimed, and the sublimed SiF ４ The gas is exhausted from the inside of the processing chamber 11 by the exhaust mechanism 24. As a result, the SiN film 33 is etched and removed.

[0029] On the other hand, after the AFS thin film 34 is formed, the surface of the Si film 32 is covered with the AFS thin film 34, so that the Si film 32 and the F radicals do not come into contact with each other. Therefore, the chemical reaction shown in the above formula (2) does not occur in the Si film 32, and SiF ４ As a result, etching of the Si film 32 is suppressed. This allows the SiN film 33 to be etched while ensuring a selectivity to the Si film 32 (FIG. 3C). Thereafter, the wafer W is unloaded from the processing chamber 11 (step S24), and the process is completed.

[0030] According to the process of FIG. 2, the process gas is NF ３ Not only gas but also NH ３ By using this gas, it is possible to cover only the surface of the Si film 32 out of the Si film 32 and the SiN film 33 with the AFS thin film 34. Then, since this AFS thin film 34 suppresses etching of the Si film 32, it is possible to etch the SiN film 33 while ensuring a selectivity to the Si film 32 without using oxygen.

[0031] In addition, in the process of FIG. ３ The molecules of F act as a catalyst to promote the reaction between SiN and F radicals, thereby promoting etching of the SiN film 33. This makes it possible to suppress a decrease in throughput.

[0032] As described above, the surface of the SiN film 33 is hardly covered with the thin film 34 of AFS. However, when F radicals are selectively transmitted into the processing space S, NH ３ The gas is present in excess, and a large number of NH ３ If the molecules of NH are attached to the surface of the SiN film 33, a thin film of AFS may be formed on the surface of the SiN film 33. Therefore, when the F radicals are selectively transmitted into the processing space S, the NH ３ NF so that there is no excess gas. ３ The timing of supplying the gas to the plasma generating space P and the NH ３ The timing at which the gas is supplied to the processing space S may be shifted.

[0033] FIG. 4 is a flowchart showing a modified example of the SiN etching process performed by the etching apparatus 10 of FIG. 1, and FIGS. 5A to 5D are process diagrams of the SiN etching process of FIG.

[0034] First, the wafer W is carried into the processing chamber 11 of the etching apparatus 10 (step S41) and placed on the stage 16. Then, N 2 is supplied as a pressure adjusting gas from the second gas supply unit 23. ２ Gas is supplied into the processing chamber 11, and the temperature of the wafer W is adjusted and stabilized at a relatively low temperature of, for example, 15° C. by the temperature adjustment mechanism 20.

[0035] Next, the inside of the processing chamber 11 is evacuated by the exhaust mechanism 24, and the inside of the processing chamber 11 is set to, for example, 100 mTorr. After that, first, NF ３ NH 4 is supplied from the second gas supply part 23 to the processing space S without supplying gas to the plasma generation space P. ３ Gas, Ar gas or N ２ At this time, as shown in FIG. 5A, NH ３ However, the exhaust mechanism 24 continues to exhaust the gas in order to maintain a vacuum atmosphere inside the processing vessel 11. ３ The molecules of NH 3 in the processing space S are also continuously discharged to the outside of the processing vessel 11. ３The number of NH molecules gradually decreases, and a small number of NH molecules remain on the surfaces of the Si film 32 and the SiN film 33. ３ Only molecules of

[0036] Next, NH ３ NF is supplied from the first gas supply unit 22 to the plasma generation space P without supplying gas. ３ In addition, high frequency power is supplied from the high frequency power supply 27 to the RF antenna 25, and the NF ３ The gas is excited to generate F plasma (step S44). At this time, F radicals in the F plasma generated in the plasma generating space P are selectively transmitted to the processing space S, and NH ３ The molecules and F radicals (black circles in the figure) are mixed together.

[0037] As described above, the energy required for generating AFS from Si is relatively low. Therefore, a small number of NH ３ Even if only molecules of Si and NH are attached, when F radicals reach there, ３ The NH radicals and F radicals immediately undergo the chemical reaction shown in the above formula (1) to form an AFS thin film 34 (FIG. 5C). On the other hand, since the energy required to generate AFS from SiN is relatively high, a small number of NH radicals are deposited on the surface of the SiN film 33. ３ If only the molecules are attached, even if the F radical reaches there, SiN, NH ３ The F radicals do not undergo any chemical reaction, and therefore the SiN film 33 is not covered with a thin film of AFS.

[0038] The SiN in the SiN film 33 that is not covered by the thin film 34 of the AFS and the F radicals undergo a chemical reaction shown in the above formula (2), resulting in SiF ４ As a result, the SiN film 33 is etched and removed. On the other hand, the surface of the Si film 32 is covered with the thin film 34 of AFS, and therefore SiF ４As a result, etching of the Si film 32 is suppressed. That is, the SiN film 33 is etched while reliably ensuring the etching selectivity with respect to the Si film 32 (FIG. 5D). Thereafter, the wafer W is unloaded from the processing chamber 11 (step S45), and the process is completed.

[0039] According to the process of FIG. 4, NH ３ After the gas is supplied, the exhaust mechanism 24 continues to exhaust the gas, and then the F radicals are selectively transmitted into the processing space S. Therefore, by the time the F radicals reach the surface of the SiN film 33, a small number of NH ３ On the other hand, since only a small number of NH molecules are attached to the surface of the Si film 32, the SiN film 33 can be reliably prevented from being covered with a thin film of AFS. ３ Even if only molecules of AFS are attached to the surface of the Si film 32, the surface of the Si film 32 is covered with a thin film of AFS 34. This allows the SiN film 33 to be etched while ensuring a selectivity to the Si film 32.

[0040] The applicant has also investigated the effect of NH ３ First, the applicant confirmed the influence of NH ３ The etching process was performed on the wafer W without using any gas. Specifically, after the wafer W was loaded into the processing chamber 11, the temperature of the wafer W was adjusted to 15° C., and the pressure inside the processing chamber 11 was set to 100 mTorr. Then, Ar gas and N 2 gas were first supplied from the second gas supply unit 23 to the processing space S. ２ Gas was supplied.

[0041] Next, Ar gas and N ２ After the gas supply was continued for 30 seconds, NF ３ Gas is supplied, and high frequency power is supplied from the high frequency power source 27 to the RF antenna 25 to generate NF ３An F plasma was generated from the gas. After the supply of high frequency power to the RF antenna 25 was continued for 10 seconds, the supply of high frequency power to the RF antenna 25 was stopped, and the wafer W was unloaded from the processing chamber 11. The etching amounts of the Si film 32 and the SiN film 33 on this wafer W are shown as Comparative Example 1 in FIG. 6. In FIG. 6, the etching amount of the SiN film 33 is shown as an outline, and the etching amount of the Si film 32 is shown as a hatched area.

[0042] Next, the applicant used NH ３ Although gas is used, NH ３ After gas supply and NF ３ Before supplying the gas, the inside of the processing chamber 11 was evacuated once, and then the etching process was performed on the wafer W. Specifically, after the wafer W was loaded into the processing chamber 11, the temperature of the wafer W was adjusted to 15° C., and the internal pressure of the processing chamber 11 was set to 100 mTorr. Then, NH 4 was first supplied from the second gas supply unit 23 to the processing space S. ３ Gas, Ar gas or N ２ The gas was supplied, and then the inside of the processing vessel 11 was evacuated by the exhaust mechanism 24. This evacuation was strong enough to purge almost all of the gas inside the processing vessel 11, unlike the evacuation for adjusting the pressure inside the processing vessel 11.

[0043] Next, Ar gas or N gas for adjusting the pressure inside the processing vessel 11 is supplied from the second gas supply unit 23 to the processing space S. ２ After supplying the gas and setting the internal pressure of the processing chamber 11 to 100 mTorr, NF ３ The gas was supplied. Also, high frequency power was supplied from the high frequency power supply 27 to the RF antenna 25 to generate NF ３ An F plasma was generated from the gas. After the supply of high frequency power to the RF antenna 25 was continued for 10 seconds, the supply of high frequency power to the RF antenna 25 was stopped, and the wafer W was unloaded from the processing chamber 11. The etching amounts of the Si film 32 and the SiN film 33 on the wafer W are shown as Comparative Example 2 in FIG. 6 .

[0044] Next, the applicant used NH３ Instead of gas, hydrogen (H ２ ) gas and N ２ The wafer W was subjected to an etching process using the gas. Specifically, after the wafer W was loaded into the processing chamber 11, the temperature of the wafer W was adjusted to 15° C., and the internal pressure of the processing chamber 11 was set to 100 mTorr. Then, H 2 O 3 was first supplied from the second gas supply unit 23 to the processing space S. ２ Gas and N ２ Gas was supplied.

[0045] Next, H ２ Gas and N ２ After the gas supply was continued for 30 seconds, NF ３ Gas is supplied, and high frequency power is supplied from the high frequency power source 27 to the RF antenna 25 to generate NF ３ An F plasma was generated from the gas. After the supply of high frequency power to the RF antenna 25 was continued for 10 seconds, the supply of high frequency power to the RF antenna 25 was stopped, and the wafer W was unloaded from the processing chamber 11. The etching amounts of the Si film 32 and the SiN film 33 on the wafer W are shown as Comparative Example 3 in FIG. 6 .

[0046] 4 was performed on a wafer W. Specifically, after the wafer W was loaded into the processing chamber 11, the temperature of the wafer W was adjusted to 15° C., and the pressure inside the processing chamber 11 was set to 100 mTorr. Then, NH 4 was first introduced into the processing space S from the second gas supply unit 23. ３ Gas, Ar gas or N ２ Gas was supplied.

[0047] Next, NH ３ Gas, Ar gas or N ２ After the gas supply was continued for 30 seconds, NF ３ The gas was supplied. Also, high frequency power was supplied from the high frequency power supply 27 to the RF antenna 25 to generate NF ３An F plasma was generated from the gas. After the supply of high frequency power to the RF antenna 25 was continued for 10 seconds, the supply of high frequency power to the RF antenna 25 was stopped, and the wafer W was unloaded from the processing chamber 11. The etching amounts of the Si film 32 and the SiN film 33 on the wafer W are shown as an example in FIG. 6 .

[0048] As shown in FIG. 6, in Comparative Examples 1 and 2, the etching amount of the Si film 32 is larger than the etching amount of the SiN film 33, and the etching selectivity of the SiN film 33 to the Si film 32 is not ensured.

[0049] In Comparative Example 1, NH ３ In Comparative Example 2, the inside of the processing vessel 11 is evacuated to remove NH ３ Therefore, in Comparative Examples 1 and 2, when F radicals are selectively transmitted into the processing space S, NH ３ There is no gas present on the surface of the Si film 32. ３ As a result, when the F radicals reach the surface of the Si film 32, the Si and F radicals undergo a chemical reaction shown in the following formula (3), resulting in SiF ４ Then, this SiF ４ is sublimated and exhausted from the inside of the processing chamber 11. That is, etching of the Si film 32 is not inhibited.

[0050] SiN + 4F ＊ → SiF ４ ↑ …(3)

[0051] On the other hand, when the F radicals reach the SiN film 33, the SiN and the F radicals undergo a chemical reaction shown in the above formula (2), resulting in SiF ４ but acts as a catalyst ３ Since the molecules of , are not present, the chemical reaction shown in the above formula (2) is not significantly promoted. As a result, it is presumed that the etching amount of the Si film 32 is greater than the etching amount of the SiN film 33.

[0052] In Comparative Example 3, neither the Si film 32 nor the SiN film 33 was significantly etched.３ H instead of gas ２ Gas and N ２ Gas was used, but NH ３ H than gas ２ The gas reacts more easily with Si and SiN to generate AFS, and the surfaces of both the Si film 32 and the SiN film 33 are covered with AFS. Therefore, after the AFS is generated, the SiN film 33 and the Si film 32 do not come into contact with F radicals. As a result, it is presumed that neither the Si film 32 nor the SiN film 33 was etched significantly.

[0053] On the other hand, in the example, the SiN film 33 is largely etched, while the Si film 32 is hardly etched, and the etching selectivity of the SiN film 33 to the Si film 32 is ensured.

[0054] From the comparison of the results of Comparative Examples 1 and 2 with those of the Example, NH ３ It was confirmed that the Si film 32 was hardly etched when the gas was present. ３ It was confirmed that when the gas was present, a thin film 34 of AFS was formed on the surface of the Si film 32, and this thin film 34 of AFS suppressed etching of the Si film 32. Furthermore, from a comparison of the results of Comparative Examples 1 and 2 with those of the Example, it was found that the presence of NH ３ It was confirmed that the SiN film 33 was significantly etched when the gas was present. ３ It was confirmed that the molecules of NH act as a catalyst to promote etching of the SiN film 33. ３ It has been found that by using the gas as a processing gas, the SiN film 33 can be etched while ensuring a selectivity to the Si film 32 without using oxygen.

[0055] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments, and various modifications and changes are possible within the scope of the gist of the present disclosure.

[0056] For example, in this embodiment, NF is used as the fluorine-containing gas for generating F plasma. ３ Although gas was used, other fluorine-containing gases, such as fluorine (F ２ ) gas may also be used.

[0057] This application claims priority based on Japanese Patent Application No. 2024-092232, filed on June 6, 2024, the entire contents of which are incorporated herein by reference.

[0058] S: Processing space W: Wafer 10: Etching device 11: Processing chamber 32: Si film 33: SiN film

Claims

1. A substrate processing method for etching the silicon nitride film while ensuring a selectivity to the silicon film, comprising the steps of: placing a substrate having a silicon film and a silicon nitride film formed thereon in a processing space; using a processing gas containing at least ammonia gas and a fluorine-containing gas on the substrate in the processing space maintained in a vacuum atmosphere in the processing space; first supplying the ammonia gas into the processing space without supplying the fluorine-containing gas into the processing space when exhausting the processing space to maintain the vacuum atmosphere; and then supplying the fluorine-containing gas into the processing space without supplying the ammonia gas into the processing space, thereby etching the substrate.

2. The substrate processing method according to claim 1, wherein plasma is used when etching the substrate.

3. The substrate processing method according to claim 1, wherein when the ammonia gas is supplied to the processing space without supplying the fluorine-containing gas to the processing space, plasma is not generated from the ammonia gas.

4. The substrate processing method of claim 1, wherein the processing gas does not include an oxygen-containing gas.

5. The substrate processing method according to claim 1, wherein the processing gas contains only an inert gas other than the ammonia gas and the fluorine-containing gas.

6. The substrate processing method according to claim 1, wherein said fluorine-containing gas is nitrogen trifluoride gas.

7. A substrate processing apparatus for etching the silicon nitride film while ensuring a selectivity to the silicon film, comprising: a processing vessel having a processing space for accommodating a substrate having a silicon film and a silicon nitride film formed thereon; wherein, in the processing space maintained in a vacuum atmosphere, a processing gas containing at least ammonia gas and a fluorine-containing gas is used on the substrate in the processing space; when exhausting is performed to maintain the processing space in a vacuum atmosphere, the ammonia gas is first supplied to the processing space without supplying the fluorine-containing gas to the processing space; and thereafter, the fluorine-containing gas is supplied to the processing space without supplying the ammonia gas to the processing space, thereby etching the substrate.

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