Substrate processing method

Abstract

To provide a substrate processing method to selectively form nitride film on top of photoresist film.SOLUTION: A substrate processing method comprises: a step for preparing a substrate with a base film, a step for forming a photoresist film on top of the base film; a step for exposing and developing the photoresist film to form a pattern of apertures in the photoresist film; a step for exposing the photoresist film to an infiltration gas containing a first element to infiltrate the first element into the top of the photoresist film to form a modified layer; and a step for selectively forming a nitride film containing a second element on top of the modified layer.SELECTED DRAWING: Figure 2

Description

[Technical field]

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

[0002] Patent Document 1 discloses a method for manufacturing a semiconductor device, comprising the following steps for forming a trench having a substantially vertical sidewall in a silicon substrate, the method comprising: (a) providing, on a silicon substrate, a first photoresist layer, a silicon nitride layer, and a second photoresist layer having a higher sensitivity and being thinner than the first photoresist layer, in that order; (b) forming a desired pattern in the second photoresist layer, transferring the pattern to the silicon nitride layer by reactive ion etching using CF4, and transferring the pattern to the first photoresist layer by reactive ion etching using low-pressure oxygen; and (c) forming a trench in the silicon substrate by reactive ion etching in a CF4 plasma having an extremely low concentration of fluorine through an opening in a mask formed by steps (a) and (b). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 59-013329 Summary of the Invention [Problem to be solved by the invention]

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

[0005] In order to solve the above problem, a substrate processing method is provided, comprising the steps of: preparing a substrate having an undercoat film; forming a photoresist film on the undercoat 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 to form a modified layer; and selectively forming a nitride film containing a second element on the modified layer. Effect of the Invention

[0006] According to one aspect of the present disclosure, a substrate processing method can be provided for selectively forming a nitride film on a photoresist film. [Brief description of the drawings]

[0007] [Figure 1] 4 is a flowchart showing an example of a substrate processing method according to the present embodiment. [Diagram 2] 5A to 5C are schematic cross-sectional views of a substrate in each process; [Diagram 3] 13 shows an example of a substrate after the development process in step S104. [Figure 4] 11 is a graph showing an example of atomic concentrations in a substrate processed in step S105. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment 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 duplicated descriptions may be omitted.

[0009] An example of a substrate processing method according to the present embodiment will be described with reference to Fig. 1 and Fig. 2. Fig. 1 is a flow chart showing an example of the substrate processing method according to the present embodiment. Fig. 2 is a schematic cross-sectional view of a substrate in each process.

[0010] In step S101, a substrate is prepared. Here, the substrate to be prepared includes a base 200 and a hard mask 210. The base 200 is, for example, any one of Si, TiN, TiO, and SiN. The hard mask 210 is formed on the base 200. The hard mask 210 includes a SOC (Spin On Carbon) film 211 and a SOG (Spin On Glass) film 212. The SOC film 211 is a carbon-containing film. The SOG film 212 is a silicon-containing film. Note that the configuration of the hard mask 210 is not limited to this. The hard mask 210 may be only one of the SOC film 211 and the SOG film 212, or may have another film. For example, the hard mask 210 may have a film such as an anti-reflective film (BARC: Bottom Anti-Reflective Coating). Note that in the following description, a film disposed under the photoresist film 220 is also referred to as an undercoat film. 2, the SOG film 212 serves as the base film. The base film is not limited to the SOG film 212 (silicon-containing film), but may be an SOC film 211 (carbon-containing film) or an anti-reflection film (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 later. The photoresist film 220 may be a negative photoresist film or a positive photoresist film.

[0012] In step S103, the substrate is subjected to an exposure process. Here, in a nitrogen atmosphere, the photoresist film 220 of the substrate is irradiated with EUV (Extreme Ultraviolet) through a photomask having a predetermined pattern, and an exposed portion irradiated with EUV and an unexposed portion not irradiated with EUV are formed in the photoresist film 220.

[0013] In step S104, the substrate is subjected to a development process. Here, either the exposed portion or the unexposed portion of the photoresist film 220 is selectively removed by the development process. The development process can be at least one of a wet process and a dry process. In a negative photoresist film, the unexposed portion is selectively removed by the development process and the exposed portion is left, thereby forming an opening pattern in the photoresist film. In a positive photoresist film, the exposed portion is selectively removed by the development process and the unexposed portion is left, thereby forming an opening pattern in the photoresist film. FIG. 2(a) is an example of a schematic cross-sectional view of the substrate after the development process. As shown in FIG. 2(a), 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 is formed by the development process in step S104 will be described with reference to FIG. 3. FIG. 3 shows an example of the substrate after the development process in step S104. FIG. 3(a) is a view of the substrate from above. FIG. 3(b) is an example of a schematic cross-sectional view of the substrate as viewed from one cross-sectional direction (BB cross-section). FIG. 3(c) is an example of a schematic cross-sectional view of the substrate as viewed from another cross-sectional direction (CC cross-section). In FIG. 3, the surface directions of the substrate are the X and Y directions, and the thickness direction of the substrate is the Z direction.

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

[0016] 3(c), there is a risk that a reduced-film portion 229, in which the film thickness is reduced, is 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 structure, there is a risk that pinching may occur. Also, when the pattern structure is a hole structure, there is a risk that merging may occur.

[0017] Returning to FIG. 1, in step S105, a denatured 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. As a result, the first element of the infiltration gas is infiltrated into the upper part of the photoresist film 220, and a denatured layer 221 is formed 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 titanium (Ti)-containing infiltration gas may be, 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 condition in which the infiltration gas forms a film by a CVD (chemical vapor deposition) reaction. This prevents 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 will be shown below. Process temperature: within the range of 50°C to 200°C, preferably around 100°C (within the range of 80°C to 120°C) Pressure range: 10Pa to 100,000Pa

[0023] FIG. 2(b) is an example of a schematic cross-sectional view of a substrate after a process for forming a denatured layer 221. Here, the photoresist film 220 has a reactive group (for example, -COOR, where R is a hydrocarbon group) that bonds with the infiltration gas. The infiltration gas reacts with the upper part of the photoresist film 220, so that the first element infiltrates the upper part of the photoresist film 220 and forms the denatured layer 221. The photoresist film 220 is made of resin, and the infiltration gas diffuses to the surface layer of the photoresist film 220. On the other hand, the SOG film 212 has a sufficiently small number of reactive groups that bond with the infiltration gas. The SOG film 212 is also annealed to be glassy, ​​and the infiltration gas is difficult to diffuse. Therefore, the infiltration gas selectively reacts with the upper part of the photoresist film 220 and forms the denatured layer 221 on the upper part of the photoresist film 220.

[0024] In step S105, a process of supplying an infiltration gas and a process of supplying a purge gas (e.g., N2 gas) may be set as one cycle, and this cycle may be repeated. This allows the amount of infiltration of the first element to be increased by repeating the number of cycles. Also, the infiltration gas physically adsorbed on the surface of the SOG film 212 or the like can be removed by the purge gas. Also, the frequency of contact of the infiltration gas between the upper part of the photoresist film 220 and the sidewall in the opening is higher in the upper part of the photoresist film 220 than in the sidewall in the opening. Therefore, a denatured layer 221 is selectively formed in the upper part of the photoresist film 220.

[0025] Fig. 2(b) is an example of a schematic cross-sectional view of the substrate after the formation process of the denatured layer 221. As shown in Fig. 2(b), the denatured layer 221 is selectively formed on the upper part of the photoresist film 220. In addition, the denatured layer 221 is prevented from being formed on the side wall in the opening of the photoresist film 220. In addition, the infiltration gas is prevented from being adsorbed to the SOG film 212 at the bottom of the opening.

[0026] Here, an example of the first element of the infiltration gas infiltrating into the photoresist film 220 by the processing of step S105 will be described with reference to FIG. 4. FIG. 4 is a graph showing an example of the atomic concentration in the substrate processed in step S105. Here, the atomic concentration of the 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 indicates the etch time, which corresponds to the depth direction of the substrate. The vertical axis indicates the atomic concentration.

[0027] 4, the atomic concentration of Ti is high near the surface layer of the substrate (where the etching time is near 0). This indicates that titanium (Ti), which is the first element, has infiltrated into the surface layer 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). The first element and the second element are preferably 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 (for example, 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 raw material 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 forming the nitride film 230 by plasma ALD, one cycle includes a step of supplying a raw material gas into a processing vessel and exposing a substrate to the raw material gas, a step of supplying a purge gas to purge the raw material gas and the like from within the processing vessel, a step of supplying a reactive gas into the processing vessel, 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 the like from within the processing vessel, and these steps are repeated a predetermined number of times.

[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. Thus, 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 includes a process of supplying a source gas into a processing vessel and exposing the substrate to the source gas, a process of supplying a purge gas to purge the source 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, NH3 can be used. In addition, N2, H2, and Ar may be added to the reactive gas.

[0035] An example of processing conditions for forming BN as the nitride film 230 will be shown below. Temperature: 60°C to 400°C, preferably 60°C to 150°C Pressure: 1 Torr to 100 Torr, preferably 1 Torr to 10 Torr Dilution Ar or N2: 100sccm to 100,000sccm, preferably 100sccm to 20,000sccm Flow rate of raw material gas containing boron (B): 1 sccm to 5,000 sccm, preferably 10 sccm to 500 sccm Reactive gas supply flow rate: 1 sccm to 5,000 sccm, preferably 100 sccm to 1,000 sccm RF power (when generating plasma): 10W to 1,000W, preferably 10W to 100W

[0036] Also, as a raw material gas containing titanium (Ti), any of tetrakis(dimethylamino)titanium, tetrakis(ethylmethylamino)titanium, tetrachlorotitanium, etc. can be used. As a reaction gas, NH3 can be used. In addition, N2, H2, and Ar may be added to the reaction gas.

[0037] An example of processing conditions for forming TiN as the nitride film 230 will be shown below. Temperature: 60°C to 400°C, preferably 60°C to 150°C Pressure: 1 Torr to 100 Torr, preferably 1 Torr to 10 Torr Dilution Ar or N2: 100sccm to 100,000sccm, preferably 100sccm to 20,000sccm Flow rate of raw material gas containing boron (B): 1 sccm to 5,000 sccm, preferably 10 sccm to 500 sccm Reactive gas supply flow rate: 1 sccm to 5,000 sccm, preferably 100 sccm to 1,000 sccm RF power (when generating plasma): 10W to 1,000W, preferably 10W to 100W

[0038] FIG. 2(c) is an example of a schematic cross-sectional view of the substrate after the formation process of the nitride film 230. 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. 2(c), 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, it is possible to suppress the nitride film 230 from growing in a mushroom shape by protruding to the left and right sides of the opening side.

[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 perform an etching process on 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] 2(d) 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. 2(d), 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, 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 will be shown below. Gases used: CF4, Cl2, Ar Pressure: 0.01 Torr ~ 1 Torr High frequency power applied to the upper electrode and the lower electrode: 100W to 1,000W (however, high frequency power applied to the upper electrode > high frequency power applied to the lower electrode)

[0042] Fig. 2(e) 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. 2(e), 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] 2(f) is an example of a schematic cross-sectional view of the substrate after removal of the SOG film 212. As shown in Fig. 2(f), the substrate has a 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, to form an opening pattern in the base 200.

[0047] As described above, the substrate processing method according to this embodiment includes a process (step S105) for selectively forming a denatured layer 221 on the upper part of the photoresist film 220 and a process (step S106) for selectively forming a nitride film 230 on the upper part of the photoresist film 220. 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 a pattern to the SOG film 212 (step S107), the etching resistance of the photoresist film 220 can be improved. Therefore, even if a thin-film portion 229 occurs in the photoresist film 220, the pattern can be suitably transferred.

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

[0050] The above describes the substrate processing method according to the present embodiment, 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 described in the claims. [Explanation of symbols]

[0051] 200 base 210 Hard Mask 211 SOC film (carbon-containing film, base film) 212 SOG film (silicon-containing film, undercoat film) 220 Photoresist film 221 Denatured Layer 230 Nitride film 215,216,225 patterns 229 Film thinning section

Claims

1. Providing a substrate having an undercoat film; forming a photoresist film on the undercoat film; performing an exposure process and a development process on the photoresist film 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 an upper portion of the photoresist film to form a modified layer; and selectively forming a nitride film containing a second element on the modified layer. A method for processing a substrate.

2. The first element is boron (B) or titanium (Ti); The method of claim 1 .

3. The wetting gas is dimethylethoxyboron, triisopentylboron, trimethylboroxine, or tributylborate; The substrate processing method according to claim 2 .

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

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

6. The step of forming the modified layer includes: supplying the infiltration gas; and repeating the steps of: supplying a purge gas; The substrate processing method according to claim 1 .

7. The second element is boron (B) or titanium (Ti); The substrate processing method according to claim 1 .

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

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

10. The step of forming the nitride film includes: supplying a source gas; and repeating the steps of: supplying a reaction gas; The substrate processing method according to claim 1 .

11. The raw material gas is dimethylethoxyboron, triisopentylboron, trimethylboroxine, tributylborate, trichloroborane, diborane, trimethylboron, triethylboron, tri(dimethylamino)boron, tri(diethylamino)boron, trimethylborazine, borazine, tetrakis(dimethylamino)titanium, tetrakis(ethylmethylamino)titanium, or tetrachlorotitanium; The method of claim 10.

12. The reaction gas is N.H. ３ That is, The method of claim 11.

13. The photoresist film is a chemically amplified resist film. The method of claim 1 .

14. The undercoat film is a silicon-containing film or a carbon-containing film; The method of claim 1 .

15. The method further comprises the step of transferring a pattern of the photoresist film to the base film after the step of selectively forming the nitride film. The method of claim 1 .

16. The method further includes a step of removing the nitride film after the step of transferring the nitride film to the base film. The method of claim 15.

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