Substrate processing method

Abstract

Provided is a substrate processing method for selectively forming a nitride film on a photoresist film.　The substrate processing method includes: a step in which a substrate having a base film is prepared; a step in which a photoresist film is formed on the base film; a step in which the photoresist film is subjected to exposure processing and development processing to form an opening pattern in the photoresist film; a step in which the photoresist film is exposed to a permeation gas containing a first element, the first element permeates the upper part of the photoresist film, and a modified layer is formed; and a step in which a nitride film containing a second element is selectively formed on the modified layer.

Description

Substrate processing method

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

[0002] Patent Document 1 discloses a method for manufacturing a semiconductor device, which includes the following steps for forming a trench having a substantially vertical sidewall in a silicon substrate, and includes the steps of: (i) providing a first photoresist layer on a silicon substrate, a silicon nitride layer, and a second photoresist layer having a higher sensitivity and being thinner than the first photoresist layer, in that order; and (ii) forming a desired pattern in the second photoresist layer, and then forming a CF ４ and transferring the patterned photoresist layer to the silicon nitride layer by reactive ion etching using oxygen at low pressure, and then transferring the patterned photoresist layer to the first photoresist layer by reactive ion etching using oxygen at low pressure; and (c) transferring the patterned photoresist layer to the silicon nitride layer by reactive ion etching using oxygen at low pressure, through the openings in the mask formed by the steps (a) and (b), using CF4 having an extremely low concentration of fluorine. ４ A method for manufacturing a semiconductor device is disclosed which includes forming trenches in the silicon substrate by reactive ion etching in a plasma.

[0003] Japanese Unexamined Patent Publication No. 59-013329

[0004] One aspect of the present disclosure provides a substrate processing method for selectively forming a nitride film on a photoresist film.

[0005] In order to solve the above problem, a substrate processing method is provided, which includes the steps of preparing a substrate having an underlayer film, forming a photoresist film on the underlayer film, exposing the photoresist film to an exposure process and a development process to form an opening pattern in the photoresist film, exposing the photoresist film to an infiltration gas containing a first element to infiltrate the first element into the upper part of the photoresist film and form a modified layer, and selectively forming a nitride film containing a second element on the modified layer.

[0006] According to one aspect of the present disclosure, a substrate processing method can be provided in which a nitride film is selectively formed on a photoresist film.

[0007] A flowchart showing an example of a substrate processing method according to the present embodiment. An example of a schematic cross-sectional view of a substrate in each step. An example of a schematic cross-sectional view of a substrate in each step. An example of a schematic cross-sectional view of a substrate in each step. An example of a schematic cross-sectional view of a substrate in each step. An example of a schematic cross-sectional view of a substrate in each step. An example of a substrate after the development process in step S104. An example of a substrate after the development process in step S104. An example of a substrate after the development process in step S104. A graph showing an example of atomic concentration in a substrate processed in step S105.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

[0009] An example of a substrate processing method according to this embodiment will be described with reference to Fig. 1 and Fig. 2A to Fig. 2F. Fig. 1 is a flowchart showing an example of the substrate processing method according to this embodiment. Fig. 2A to Fig. 2F are example schematic cross-sectional views of a substrate in each process.

[0010] In step S101, a substrate is prepared. The substrate includes a base 200 and a hard mask 210. The base 200 is made of, for example, Si, TiN, TiO, or SiN. The hard mask 210 is formed on the base 200. The hard mask 210 includes a spin-on-carbon (SOC) film 211 and a spin-on-glass (SOG) film 212. The SOC film 211 is a carbon-containing film. The SOG film 212 is a silicon-containing film. The configuration of the hard mask 210 is not limited thereto. The hard mask 210 may include only one of the SOC film 211 and the SOG film 212, or may include other films. For example, the hard mask 210 may include a film such as a bottom anti-reflective coating (BARC). In the following description, a film disposed under the photoresist film 220 is also referred to as an undercoat film. 2A, the base film is an SOG film 212. The base film is not limited to the SOG film 212 (a silicon-containing film), but may be an SOC film 211 (a carbon-containing film) or an anti-reflection film (a silicon-containing film, not shown).

[0011] In step S102, a photoresist film 220 is formed on the substrate. Here, the photoresist film 220 is formed on the SOG film 212, which is an undercoat film. The photoresist film 220 is, for example, a chemically amplified resist (CAR) film. The chemically amplified resist has a reactive group (for example, -COOR, where R is a hydrocarbon group) that bonds with the infiltration gas described below. The photoresist film 220 may be either a negative photoresist film or a positive photoresist film.

[0012] In step S103, the substrate is subjected to an exposure process in which extreme ultraviolet (EUV) is irradiated onto the photoresist film 220 of the substrate through a photomask having a predetermined pattern in a nitrogen atmosphere, forming exposed portions of the photoresist film 220 that are irradiated with EUV and unexposed portions that are not irradiated with EUV.

[0013] In step S104, the substrate is subjected to a development process. This development process selectively removes either the exposed or unexposed portions of the photoresist film 220. The development process can be a wet process or a dry process. For a negative photoresist film, the development process selectively removes the unexposed portions and leaves the exposed portions, thereby forming an opening pattern in the photoresist film. For a positive photoresist film, the development process selectively removes the exposed portions and leaves the unexposed portions, thereby forming an opening pattern in the photoresist film. FIG. 2A is an example of a cross-sectional schematic diagram of the substrate after the development process. As shown in FIG. 2A, an opening pattern 225 is formed in the photoresist film 220.

[0014] Here, an example of the photoresist film 220 in which an opening pattern 225 has been formed by the development process of step S104 will be described with reference to FIGS. 3A to 3C. FIGS. 3A to 3C show an example of a substrate after the development process of step S104. FIG. 3A is a view of the substrate from above. FIG. 3B is an example of a schematic cross-sectional view of the substrate as viewed from one cross-sectional direction (B-B cross-section). FIG. 3C is an example of a schematic cross-sectional view of the substrate as viewed from another cross-sectional direction (C-C cross-section). In FIGS. 3A to 3C, the surface directions of the substrate are defined as the X and Y directions, and the thickness direction of the substrate is defined as the Z direction.

[0015] 3A and 3B, a pattern 225 of openings is formed in the photoresist film 220 by the formation process (S102), the exposure process (S103), and the development process (S104). Here, a linear pattern (line and space) is formed in the photoresist film 220.

[0016] 3C, there is a risk that a reduced-film portion 229, where the film thickness is reduced, will be generated in the photoresist film 220 during the development process. When a pattern is transferred to the SOG film 212 (see S107 described later), the photoresist film 220 having the reduced-film portion 229 may not be able to transfer the pattern properly. For example, when the pattern structure is a line-and-space pattern, there is a risk of pinching occurring. Furthermore, when the pattern structure is a hole, there is a risk of merging occurring.

[0017] 1 , in step S105, a modified layer 221 is formed on the photoresist film 220 on which the pattern 225 is formed. Here, an infiltration gas containing a first element is supplied to a processing vessel containing a substrate, and the substrate is exposed to the infiltration gas. This causes the first element of the infiltration gas to infiltrate the upper part of the photoresist film 220, forming a modified layer 221 on the upper part of the photoresist film 220.

[0018] Here, the first element contained in the infiltration gas is either boron (B) or titanium (Ti).

[0019] The infiltration gas containing boron (B) is, for example, any one of dimethylethoxyboron, triisopentylboron, trimethylboroxine, tributylborate, and borazine.

[0020] The infiltration gas containing titanium (Ti) is, for example, tetrakis(dimethylamino)titanium, tetrakis(ethylmethylamino)titanium, or tetrachlorotitanium.

[0021] In the step (S105) of forming the denatured layer 221, the process temperature is set to a temperature range lower than the temperature conditions for film formation by a chemical vapor deposition (CVD) reaction of the infiltration gas, thereby preventing a film containing the first element from being formed on the surface of the SOG film 212 at the bottom of the opening.

[0022] An example of processing conditions in the step of forming the modified layer 221 is as follows: Process temperature: in the range of 50° C. to 200° C., preferably around 100° C. (in the range of 80° C. to 120° C.) Pressure range: in the range of 10 Pa to 100,000 Pa

[0023] FIG. 2B is an example of a schematic cross-sectional view of a substrate after a process for forming a modified layer 221. Here, the photoresist film 220 has reactive groups (e.g., —COOR, where R is a hydrocarbon group) that bond with the infiltration gas. When the infiltration gas reacts with the upper portion of the photoresist film 220, the first element infiltrates the upper portion of the photoresist film 220, forming the modified layer 221. Furthermore, the photoresist film 220 is made of resin, and the infiltration gas diffuses into the surface layer of the photoresist film 220. Meanwhile, the SOG film 212 has a sufficiently small number of reactive groups that bond with the infiltration gas. Furthermore, the SOG film 212 has been annealed to form a glassy structure, making it difficult for the infiltration gas to diffuse. Therefore, the infiltration gas selectively reacts with the upper portion of the photoresist film 220, forming the modified layer 221 on the upper portion of the photoresist film 220.

[0024] In step S105, a process of supplying a wetting gas and a process of supplying a purge gas (e.g., N ２ The process of supplying the first element and the second element (gas) constitutes one cycle, and this cycle may be repeated. By repeating the cycles, the amount of infiltration of the first element can be increased. Furthermore, the infiltration gas physically adsorbed on the surface of the SOG film 212 can be removed by the purge gas. Furthermore, the frequency of contact of the infiltration gas between the top of the photoresist film 220 and the sidewalls in the openings is higher at the top of the photoresist film 220 than at the sidewalls in the openings. Therefore, a modified layer 221 is selectively formed on the top of the photoresist film 220.

[0025] 2B is an example of a schematic cross-sectional view of the substrate after the process of forming the denatured layer 221. As shown in FIG. 2B, the denatured layer 221 is selectively formed on the upper part of the photoresist film 220. The denatured layer 221 is also prevented from being formed on the sidewalls of the openings in the photoresist film 220. The denatured layer 221 is also prevented from being adsorbed by the SOG film 212 at the bottom of the openings.

[0026] An example of the infiltration of the first element of the infiltration gas into the photoresist film 220 by the processing of step S105 will now be described with reference to FIG. 4 . FIG. 4 is a graph showing an example of the atomic concentration in a substrate processed in step S105. Here, the atomic concentration of a substrate processed in step S105 using tetrakis(dimethylamino)titanium as the infiltration gas was analyzed in the depth direction of the substrate by X-ray photoelectron spectroscopy (XPS). The horizontal axis represents the etch time, which corresponds to the depth direction of the substrate. The vertical axis represents the atomic concentration.

[0027] 4, the atomic concentration of Ti is high near the surface of the substrate (near the etching time of 0). This indicates that titanium (Ti), which is the first element, has infiltrated into the surface of the photoresist film 220, forming a modified layer 221.

[0028] Returning to FIG. 1 , in step S106, a nitride film 230 is formed on the photoresist film 220 on which the pattern 225 is formed. The nitride film 230 is a nitride film containing a second element and nitrogen (N). The second element is either boron (B) or titanium (Ti). Preferably, the first element and the second element are the same element. That is, when the first element is boron (B), the second element is also boron (B). When the first element is titanium (Ti), the second element is also titanium (Ti). The first element and the second element may be different elements (e.g., one is boron and the other is titanium). The nitride film 230 is either BN, TiN, or the like.

[0029] The nitride film 230 is formed using a source gas and a reactive gas. The nitride film 230 can be formed by any of CVD (Chemical Vapor Deposition), ALD (Atomic Layer Deposition), plasma CVD (Plasma Enhanced Chemical Vapor Deposition), plasma ALD (Plasma Enhanced Atomic Layer Deposition), etc.

[0030] For example, when the nitride film 230 is formed by plasma ALD, one cycle is repeated a predetermined number of times, the cycle consisting of a step of supplying a raw material gas into a processing vessel and exposing the substrate to the raw material gas, a step of supplying a purge gas to purge the raw material gas and other substances in the processing vessel, a step of supplying a reactive gas into the processing vessel and generating plasma of the reactive gas, exposing the substrate to the plasma of the reactive gas, and a step of supplying a purge gas to purge the reactive gas and other substances in the processing vessel.

[0031] In a process of supplying a source gas and exposing the substrate to the source gas, the source gas selectively adsorbs to the first element of the modified layer 221. In a process of supplying a reactive gas and exposing the substrate to plasma of the reactive gas, the source gas adsorbed to the modified layer 221 is nitrided to form a nitride film. In the next cycle, the source gas selectively adsorbs to the nitride film. As a result, by repeating the cycle, a nitride film 230 is selectively formed on the modified layer 221.

[0032] It is also preferable to form the nitride film 230 without generating plasma, which can prevent the nitride film 230 from being formed on the SOG film 212 at the bottom of the opening.

[0033] For example, when forming the nitride film 230 by ALD, one cycle is composed of a process of supplying a raw material gas into a processing vessel and exposing the substrate to the raw material gas, a process of supplying a purge gas to purge the raw material gas and other gases in the processing vessel, and a process of supplying a purge gas to purge the reactive gas and other gases in the processing vessel, and this process is repeated a predetermined number of times.

[0034] As a source gas containing boron (B), any of dimethylethoxyboron, triisopentylboron, trimethylboroxine, tributylborate, trichloroborane, diborane, trimethylboron, triethylboron, tri(dimethylamino)boron, tri(diethylamino)boron, trimethylborazine, borazine, etc. can be used. As a reactive gas, NH ３ In addition, N can be used as the reaction gas. ２ , H ２ , Ar may be added.

[0035] An example of processing conditions for forming BN as the nitride film 230 is as follows: Temperature: 60° C. to 400° C., preferably 60° C. to 150° C. Pressure: 1 Torr to 100 Torr, preferably 1 Torr to 10 Torr Diluted Ar or N ２ : 100 sccm to 100,000 sccm, preferably 100 sccm to 20,000 sccm Supply flow rate of boron (B)-containing raw material gas: 1 sccm to 5,000 sccm, preferably 10 sccm to 500 sccm Supply flow rate of reaction gas: 1 sccm to 5,000 sccm, preferably 100 sccm to 1,000 sccm RF power (when generating plasma): 10 W to 1,000 W, preferably 10 W to 100 W

[0036] As a source gas containing titanium (Ti), any of tetrakis(dimethylamino)titanium, tetrakis(ethylmethylamino)titanium, tetrachlorotitanium, etc. can be used. As a reactive gas, NH ３ In addition, N can be used as the reaction gas. ２ , H ２ , Ar may be added.

[0037] An example of the processing conditions for forming TiN as the nitride film 230 is as follows: Temperature: 60° C. to 400° C., preferably 60° C. to 150° C. Pressure: 1 Torr to 100 Torr, preferably 1 Torr to 10 Torr Diluted Ar or N ２ : 100 sccm to 100,000 sccm, preferably 100 sccm to 20,000 sccm Supply flow rate of boron (B)-containing raw material gas: 1 sccm to 5,000 sccm, preferably 10 sccm to 500 sccm Supply flow rate of reaction gas: 1 sccm to 5,000 sccm, preferably 100 sccm to 1,000 sccm RF power (when generating plasma): 10 W to 1,000 W, preferably 10 W to 100 W

[0038] 2C is an example of a schematic cross-sectional view of the substrate after the nitride film 230 formation process. Here, the nitride film 230 is formed starting from the denatured layer 221 on the upper part of the photoresist film 220. Therefore, as shown in FIG. 2C, the nitride film 230 is selectively formed on the upper part of the photoresist film 220. The thickness of the nitride film 230 is determined by the thickness of the SOG film 212 and the etching selectivity between the nitride film 230 and the SOG film 212, and is, for example, 5 nm. By suppressing the thickness of the nitride film 230, the nitride film 230 is prevented from growing into a mushroom shape by protruding to the left and right of the opening.

[0039] In step S107, the pattern is transferred to the SOG film 212. Here, the photoresist film 220 on which the pattern 225 is formed is used as a mask to etch the SOG film 212 using a CF-based gas, thereby forming an opening pattern 215 in the SOG film 212. That is, the opening pattern 225 of the photoresist film 220 is transferred to the SOG film 212, thereby forming the opening pattern 215 in the SOG film 212.

[0040] 2D is an example of a schematic cross-sectional view of the substrate after processing to transfer a pattern to the SOG film 212. Here, the nitride film 230 has etching resistance to the CF-based gas used to etch the SOG film 212. Therefore, as shown in FIG. 2D , the SOG film 212 is selectively etched, and an opening pattern 215 is formed in the SOG film 212.

[0041] In step S108, the nitride film 230 is removed. For example, the following is an example of processing conditions for removing the nitride film 230 using a chlorine-containing gas in a CCP (Capacitively Coupled Plasma) type plasma etching apparatus: ４ , Cl ２ , Ar Pressure: 0.01 Torr to 1 Torr High frequency power applied to upper electrode and lower electrode: 100 W to 1,000 W (however, high frequency power applied to upper electrode > high frequency power applied to lower electrode)

[0042] 2E is an example of a schematic cross-sectional view of the substrate after the removal process of the nitride film 230. As shown in Fig. 2E, the nitride film 230 on the upper part of the photoresist film 220 is removed. At the same time, the denatured layer 221 on the upper part of the photoresist film 220 is also removed.

[0043] In step S109, the photoresist film 220 is removed.

[0044] In step S110, a pattern is transferred to the SOC film 211. Here, the SOG film 212 on which the pattern 215 is formed is used as a mask to perform an etching process on the SOC film 211, thereby forming an opening pattern 216 in the SOC film 211. That is, the opening pattern 215 of the SOG film 212 is transferred to the SOC film 211, thereby forming the opening pattern 216 in the SOC film 211.

[0045] In step S111, the SOG film 212 is removed.

[0046] 2F is an example of a schematic cross-sectional view of the substrate after removal of the SOG film 212. As shown in FIG. 2F, the substrate has an SOC film 211 on which an opening pattern 216 is formed on a base 200. Thereafter, an etching process may be performed on the base 200 using the SOC film 211 on which the opening pattern 216 is formed as a mask, thereby forming an opening pattern in the base 200.

[0047] As described above, the substrate processing method according to this embodiment includes a process of selectively forming a denatured layer 221 on the upper part of the photoresist film 220 (step S105) and a process of selectively forming a nitride film 230 on the upper part of the photoresist film 220 (step S106). As a result, the upper part of the photoresist film 220 is selectively reinforced with the nitride film 230.

[0048] Furthermore, in the process of transferring the pattern to the SOG film 212 (step S107), the etching resistance of the photoresist film 220 can be improved. Therefore, even if a thinned portion 229 occurs in the photoresist film 220, the pattern can be transferred suitably.

[0049] Furthermore, before removing the photoresist film 220 (step S109), the nitride film 230 formed on the photoresist film 220 can be suitably removed (step S108).

[0050] The substrate processing method according to the present embodiment has been described above, but the present disclosure is not limited to the above embodiment, and various modifications and improvements are possible within the scope of the gist of the present disclosure as set forth in the claims.

[0051] This application claims priority based on Japanese Patent Application No. 2023-132102, filed on August 14, 2023, the entire contents of which are incorporated herein by reference.

[0052] 200 Base 210 Hard mask 211 SOC film (carbon-containing film, underlayer) 212 SOG film (silicon-containing film, underlayer) 220 Photoresist film 221 Modified layer 230 Nitride film 215, 216, 225 Pattern 229 Thinned portion

Claims

1. A substrate processing method comprising the steps of: preparing a substrate having an undercoat film; forming a photoresist film on the undercoat film; exposing and developing the photoresist film to form an opening pattern in the photoresist film; exposing the photoresist film to an infiltration gas containing a first element, causing the first element to infiltrate into an upper portion of the photoresist film, thereby forming a modified layer; and selectively forming a nitride film containing a second element on the modified layer.

2. The substrate processing method according to claim 1, wherein the first element is boron (B) or titanium (Ti).

3. The substrate processing method according to claim 2, wherein the infiltration gas is any one of dimethylethoxyboron, triisopentylboron, trimethylboroxine, and tributylborate.

4. The substrate processing method according to claim 2, wherein the infiltration gas is any one of tetrakis(dimethylamino)titanium, tetrakis(ethylmethylamino)titanium, and tetrachlorotitanium.

5. The substrate processing method according to claim 3 or 4, wherein in the step of forming the denatured layer, the process temperature is within a range of 60°C to 200°C, and the pressure is within a range of 10 Pa to 100,000 Pa.

6. The substrate processing method according to claim 1, wherein the step of forming the denatured layer comprises repeating a step of supplying the infiltration gas and a step of supplying a purge gas.

7. The substrate processing method according to any one of claims 1 to 4, wherein the second element is boron (B) or titanium (Ti).

8. The substrate processing method according to claim 7, wherein the first element and the second element are the same element.

9. The substrate processing method according to claim 7, wherein the nitride film is BN or TiN.

10. The substrate processing method according to claim 1, wherein the step of forming the nitride film comprises repeating a step of supplying a source gas and a step of supplying a reactive gas.

11. The substrate processing method according to claim 10, wherein the source gas is any one of dimethylethoxyboron, triisopentylboron, trimethylboroxine, tributylborate, trichloroborane, diborane, trimethylboron, triethylboron, tri(dimethylamino)boron, tri(diethylamino)boron, trimethylborazine, borazine, tetrakis(dimethylamino)titanium, tetrakis(ethylmethylamino)titanium, and tetrachlorotitanium.

12. The reaction gas is NH ３ The method for processing a substrate according to claim 11 , 13. The substrate processing method according to claim 1, wherein the photoresist film is a chemically amplified resist film.

14. The substrate processing method according to claim 1, wherein the undercoat film is a silicon-containing film or a carbon-containing film.

15. The substrate processing method according to claim 1, further comprising the step of transferring a pattern of the photoresist film to the base film after the step of selectively forming the nitride film.

16. The substrate processing method according to claim 15, further comprising the step of removing the nitride film after the step of transferring the nitride film to the base film.

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