Recess structure forming method

Abstract

A technology is provided that can reduce the diffusion of precious metals contained in a catalyst layer to a substrate. [Solution] A method for forming a recess structure according to one aspect of the present disclosure includes forming a barrier film on a substrate, forming a catalyst layer containing a precious metal on the barrier film, forming a resist pattern on the catalyst layer, etching the catalyst layer using the resist pattern as an etching mask, and forming a recess structure in the substrate by etching the substrate in an area covered with the catalyst layer by metal-assisted etching.

Description

[Technical Field]

[0001] The present disclosure relates to a method for forming a recess structure. [Background technology]

[0002] Patent Document 1 discloses that a Ru catalyst film is patterned using photolithography, and then immersed in an etchant solution to perform catalytic etching. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2023-548321 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can reduce the diffusion of precious metals contained in a catalyst layer to a substrate. [Means for solving the problem]

[0005] A method for forming a recess structure according to one aspect of the present disclosure includes forming a barrier film on a substrate, forming a catalyst layer containing a precious metal on the barrier film, forming a resist pattern on the catalyst layer, etching the catalyst layer using the resist pattern as an etching mask, and forming a recess structure in the substrate by etching the substrate in an area covered with the catalyst layer by metal-assisted etching. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to reduce the diffusion of the precious metal contained in the catalyst layer to the substrate. [Brief explanation of the drawings]

[0007] [Figure 1]1 is a flowchart illustrating a recess structure forming method according to an embodiment. [Figure 2] 1A and 1B are cross-sectional views (1) illustrating a recess structure forming method according to an embodiment. [Figure 3] 10 is a cross-sectional view (2) showing the recess structure forming method according to the embodiment. FIG. [Figure 4] 10 is a cross-sectional view (3) showing the recess structure forming method according to the embodiment. FIG. [Figure 5] 10 is a cross-sectional view (4) showing the recess structure forming method according to the embodiment. FIG. [Figure 6] 10 is a cross-sectional view (5) showing the recess structure forming method according to the embodiment. [Figure 7] 10 is a cross-sectional view (6) showing the recess structure forming method according to the embodiment. FIG. [Figure 8] 10 is a cross-sectional view (7) showing the recess structure forming method according to the embodiment. [Figure 9] 8 is a cross-sectional view (8) showing the recess structure forming method according to the embodiment. [Figure 10] 9 is a cross-sectional view showing the recess structure forming method according to the embodiment. FIG. [Figure 11] 10 is a cross-sectional view showing a recess structure forming method according to an embodiment. FIG. [Figure 12] 10A to 10C are cross-sectional views showing a method for forming a recess structure according to a comparative example. 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] [Method for forming recess structure] A recess structure forming method according to an embodiment will be described with reference to Fig. 1 to Fig. 11. Fig. 1 is a flowchart showing the recess structure forming method according to an embodiment. Fig. 2 to Fig. 11 are cross-sectional views showing the recess structure forming method according to an embodiment. The recess forming method according to an embodiment includes steps S1 to S9 shown in Fig. 1.

[0010] Step S1 includes preparing a silicon substrate 1, as shown in Figure 2. The silicon substrate 1 is an example of a substrate.

[0011] Step S2 includes forming a titanium nitride film 2 on the silicon substrate 1, as shown in FIG. 3. The titanium nitride film 2 is an example of a barrier film. The titanium nitride film 2 can be formed by, for example, chemical vapor deposition (CVD). The thickness of the titanium nitride film 2 is, for example, 2 nm or more. In this case, it is easy to reduce the diffusion of ruthenium into the silicon substrate 1 in step S3. The thickness of the titanium nitride film 2 is, for example, 10 nm or less. In this case, etching of the silicon substrate 1 is easy to proceed during metal-assisted chemical etching (MACE), which will be described later.

[0012] Step S3, as shown in FIG. 4, includes forming a ruthenium film 3 on the titanium nitride film 2. The ruthenium film 3 is an example of a catalyst layer. The ruthenium film 3 can be formed by, for example, chemical vapor deposition. The ruthenium film 3 may be formed by atomic layer deposition (ALD) or physical vapor deposition (PVD). The thickness of the ruthenium film 3 is, for example, 20 nm. In step S3, the ruthenium film 3 is formed with the surface of the silicon substrate 1 covered with the titanium nitride film 2. Therefore, the ruthenium film 3 does not contact the silicon substrate 1. As a result, the diffusion of ruthenium into the silicon substrate 1 can be reduced.

[0013] 5, step S4 includes forming a silicon-containing anti-reflective coating 4 on the ruthenium film 3. The silicon-containing anti-reflective coating 4 can be formed by, for example, spin coating. The thickness of the silicon-containing anti-reflective coating 4 is, for example, 20 nm.

[0014] 6, step S5 forms a resist pattern 5 on the silicon-containing anti-reflective coating 4. The resist pattern 5 can be formed, for example, by applying a resist onto the silicon-containing anti-reflective coating 4 and removing a portion of the resist by photolithography. The thickness of the resist pattern 5 is, for example, 380 nm.

[0015] 7, step S6 includes etching the silicon-containing antireflective coating 4 using the resist pattern 5 as an etching mask to remove the silicon-containing antireflective coating 4 in areas not covered by the resist pattern 5. For example, reactive ion etching (RIE) using a mixed gas of CF4 gas and argon gas can be used to selectively remove the silicon-containing antireflective coating 4 relative to the resist pattern 5. At this time, the resist pattern 5 may also be slightly etched. The silicon-containing antireflective coating 4 may also be removed by reactive ion etching using a fluorine-containing gas.

[0016] As shown in FIG. 8, step S7 involves etching the ruthenium film 3 and the titanium nitride film 2 using the silicon-containing anti-reflective coating 4 as an etching mask, thereby removing the ruthenium film 3 and the titanium nitride film 2 in areas not covered by the silicon-containing anti-reflective coating 4. For example, reactive ion etching using oxygen gas can be used to selectively remove the ruthenium film 3 and the titanium nitride film 2 relative to the silicon-containing anti-reflective coating 4. Chlorine gas may be added to the oxygen gas. The ruthenium film 3 and the titanium nitride film 2 may also be removed by wet etching using an oxidizing agent. In step S7, ruthenium is not or barely diffused into the silicon substrate 1, so diffusion of ruthenium into the silicon substrate 1 due to heat applied to the silicon substrate 1 during reactive ion etching is unlikely to occur. In step S7, the resist pattern 5 is also removed, as shown in FIG. 9. After step S7, the silicon substrate 1 may be immersed in a nitric acid-based chemical solution with a nitric acid concentration of 15% or less. In this case, residues adhering to the surface of the silicon substrate 1 can be removed. Instead of the nitric acid-based chemical solution having a nitric acid concentration of 15% or less, the silicon substrate 1 may be immersed in a diluted aqueous solution of hydrofluoric acid having a concentration of 5 mol / L or less.

[0017] Step S8, as shown in FIG. 10 , involves etching the silicon substrate 1 in the region covered with the ruthenium film 3 by metal-assisted etching to form a recessed structure 6 in the silicon substrate 1. The recessed structure 6 can be formed by, for example, immersing the silicon substrate 1 in an etching solution 7 containing hydrofluoric acid and an oxidizing agent. The oxidizing agent is, for example, hydrogen peroxide. When the etching solution 7 is supplied to the silicon substrate 1, only the region covered with the ruthenium film 3 is selectively and vertically etched by metal-assisted etching, forming a recessed structure 6 in the silicon substrate 1. At this time, the titanium nitride film 2 hardly inhibits the etching of the silicon substrate 1 by metal-assisted etching. This is because the titanium nitride film 2 is conductive. In step S8, ruthenium is not or hardly diffused in the surface of the silicon substrate 1 in the region not covered with the ruthenium film 3. Therefore, etching by metal-assisted etching does not proceed in the surface of the silicon substrate 1 in the region not covered with the ruthenium film 3. As a result, it is possible to reduce surface roughness of the silicon substrate 1 resulting from the diffusion of ruthenium into the silicon substrate 1 in areas not covered with the ruthenium film 3. The recessed structure 6 is, for example, a nanostructure. The nanostructure may be a trench or a hole with a high aspect ratio.

[0018] 11, step S9 includes removing the ruthenium film 3. The ruthenium film 3 can be removed by immersing the silicon substrate 1 in, for example, a nitric acid-based chemical solution having a nitric acid concentration of 15% or less. After immersing the silicon substrate 1 in the chemical solution, the silicon substrate 1 may be washed by supplying pure water to the silicon substrate 1.

[0019] According to the recess structure forming method of the embodiment, a titanium nitride film 2 is formed between a silicon substrate 1 and a ruthenium film 3. Then, the silicon substrate 1 in the region covered with the ruthenium film 3 is etched by metal-assisted etching to form a recess structure 6 in the silicon substrate 1. In this case, when the ruthenium film 3 is formed, the surface of the silicon substrate 1 is covered with the titanium nitride film 2. Therefore, the ruthenium film 3 does not contact the silicon substrate 1. As a result, the diffusion of ruthenium into the silicon substrate 1 can be reduced. Furthermore, when the silicon substrate 1 is etched by metal-assisted etching, no or very little ruthenium diffuses into the surface of the silicon substrate 1 in the region not covered with the ruthenium film 3. Therefore, etching by metal-assisted etching does not progress in the surface of the silicon substrate 1 in the region not covered with the ruthenium film 3. As a result, the surface roughness of the silicon substrate 1 caused by the diffusion of ruthenium into the silicon substrate 1 can be reduced in the region not covered with the ruthenium film 3.

[0020] 12, in a comparative example, when there is no titanium nitride film 2 between the silicon substrate 1 and the ruthenium film 3, ruthenium 8 diffuses into the silicon substrate 1 in areas other than the area to be etched when the ruthenium film 3 is formed on the silicon substrate 1. When the silicon substrate 1 is etched by metal-assisted etching, the ruthenium 8 diffused into the silicon substrate 1 etches the areas of the silicon substrate 1 that are not covered with the ruthenium film 3. As a result, the surface of the silicon substrate 1 becomes rough in areas not covered with the ruthenium film 3 due to the diffusion of ruthenium 8 into the silicon substrate 1.

[0021] 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.

[0022] In the above embodiment, the case where the silicon-containing antireflective coating 4 is formed between the ruthenium film 3 and the resist pattern 5 has been described, but the present disclosure is not limited to this. If the ruthenium film 3 can be selectively removed with respect to the resist pattern 5, the silicon-containing antireflective coating 4 does not need to be formed.

[0023] In the above embodiment, the case where the barrier film is the titanium nitride film 2 has been described, but the present disclosure is not limited to this.

[0024] The barrier film may be a metal nitride film containing a metal other than titanium (Ti), such as tantalum (Ta) or tungsten (W), or a metal oxide film containing titanium, tantalum, or tungsten.

[0025] The barrier film may be a silicon nitride film. The silicon nitride film can be formed by, for example, chemical vapor deposition. The silicon nitride film may be formed by plasma nitriding the surface of the silicon substrate 1. When the barrier film is a silicon nitride film, when etching the silicon substrate 1 by metal-assisted etching, etching of the silicon substrate 1 begins after the silicon nitride film is removed. The thickness of the silicon nitride film is, for example, 2 nm or more. In this case, it is easy to reduce the diffusion of ruthenium into the silicon substrate 1 when forming the ruthenium film 3. The thickness of the silicon nitride film is, for example, 5 nm or less. In this case, etching of the silicon substrate 1 by metal-assisted etching is easy to progress. Furthermore, when etching the silicon substrate 1 by metal-assisted etching, it is possible to reduce movement (e.g., tilt) of the ruthenium film 3 caused by the removal of the silicon nitride film.

[0026] The barrier film may be a silicon oxide film. The silicon oxide film can be formed by, for example, chemical vapor deposition. The silicon oxide film may be formed by thermally oxidizing the surface of the silicon substrate 1. The silicon oxide film may be formed by plasma oxidizing the surface of the silicon substrate 1. When the barrier film is a silicon oxide film, when etching the silicon substrate 1 by metal-assisted etching, etching of the silicon substrate 1 begins after the silicon oxide film is removed. The thickness of the silicon oxide film is, for example, 2 nm or more. In this case, it is easy to reduce the diffusion of ruthenium into the silicon substrate 1 when forming the ruthenium film 3. The thickness of the silicon oxide film is, for example, 5 nm or less. In this case, etching of the silicon substrate 1 by metal-assisted etching is easy to progress. Furthermore, when etching the silicon substrate 1 by metal-assisted etching, it is possible to reduce movement (e.g., tilt) of the ruthenium film 3 caused by the removal of the silicon oxide film.

[0027] In the above embodiment, the catalyst layer is a ruthenium film 3, but the present disclosure is not limited to this. The catalyst layer is a film containing a noble metal. The catalyst layer may be a palladium film or a platinum film. [Explanation of symbols]

[0028] 1. Silicon substrate 2. Titanium nitride film 3 Ruthenium film 4. Silicon-containing anti-reflective coating 5. Resist pattern 6. Recessed structure 7. Etching solution

Claims

1. forming a barrier film on a substrate; forming a catalyst layer containing a noble metal on the barrier film; forming a resist pattern on the catalyst layer; Etching the catalyst layer using the resist pattern as an etching mask; forming recess structures in the substrate by etching the substrate in areas covered by the catalyst layer using metal-assisted etching; A method for forming a recess structure, comprising:

2. Etching the catalyst layer includes etching the catalyst layer by reactive ion etching using oxygen gas. The method for forming a recess structure according to claim 1 .

3. The method further includes forming a silicon-containing anti-reflective coating on the catalyst layer between forming the catalyst layer and forming the resist pattern. The method for forming a recess structure according to claim 1 .

4. The method further includes, between forming the resist pattern and etching the catalyst layer, etching the silicon-containing anti-reflective film using the resist pattern as an etching mask. The method for forming a recess structure according to claim 3 .

5. forming the recess structure includes supplying an etching solution containing hydrofluoric acid and an oxidizing agent to the substrate; The method for forming a recess structure according to claim 1 .

6. The noble metal is ruthenium, palladium or platinum; The method for forming a recess structure according to claim 1 .

7. the barrier film is a metal nitride film or a metal oxide film; The method for forming a recess structure according to claim 1 .

8. the barrier film is a titanium nitride film, The thickness of the titanium nitride film is 2 nm or more and 10 nm or less. The method for forming a recess structure according to claim 1 .

9. the barrier film is a silicon nitride film, The thickness of the silicon nitride film is 2 nm or more and 5 nm or less. The method for forming a recess structure according to claim 1 .

Images