Film formation method

Abstract

This invention provides a technology that allows for the selective formation of a silicon-containing film on the bottom surface of each of a plurality of recesses having different opening widths. [Solution] A film formation method according to one aspect of the present disclosure comprises: preparing a substrate having a plurality of recesses having different opening widths; forming a silicon-containing film along the surface of the plurality of recesses; filling the inside of the plurality of recesses where the silicon-containing film is formed with a carbon-containing film; exposing the silicon-containing film formed on the upper part of the plurality of recesses from the carbon-containing film by performing anisotropic etching of the carbon-containing film in the thickness direction of the substrate; and removing the silicon-containing film exposed from the carbon-containing film by etching the silicon-containing film using the carbon-containing film as an etching mask.

Description

Technical Field

[0001] The present disclosure relates to a film forming method.

Background Art

[0002] Patent Document 1 discloses a technique for bottom-up growth of a silicon film from the bottom surface side of a recess toward an opening. In Patent Document 1, a silicon film is formed over the entire inside of the recess, and then, by etching using chlorine gas, the silicon film on the upper part of the inner wall of the recess is removed while leaving the silicon film on the bottom surface of the recess, and then, a silicon film is selectively formed on the silicon film remaining on the bottom surface of the recess.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a technique capable of selectively forming a silicon-containing film on the bottom surface of each of a plurality of recesses having different opening widths.

Means for Solving the Problems

[0005] A film forming method according to an aspect of the present disclosure includes preparing a substrate on which a plurality of recesses having different opening widths are formed, forming a silicon-containing film along the surfaces of the plurality of recesses, filling the inside of the plurality of recesses in which the silicon-containing film is formed with a carbon-containing film, performing anisotropic etching in the thickness direction of the substrate with respect to the carbon-containing film to expose the silicon-containing film formed on the upper parts of the plurality of recesses from the carbon-containing film, and removing the silicon-containing film exposed from the carbon-containing film by etching the silicon-containing film using the carbon-containing film as an etching mask. [Effects of the Invention]

[0006] According to this disclosure, a silicon-containing film can be selectively formed on the bottom surface of each of a plurality of recesses having different opening widths. [Brief explanation of the drawing]

[0007] [Figure 1] This is a flowchart showing the film deposition method according to the embodiment. [Figure 2] This is a cross-sectional view (1) showing the film deposition method according to the embodiment. [Figure 3] This is a cross-sectional view (2) showing the film deposition method according to the embodiment. [Figure 4] This is a cross-sectional view (3) showing the film deposition method according to the embodiment. [Figure 5] This is a cross-sectional view (4) showing the film deposition method according to the embodiment. [Figure 6] This is a cross-sectional view (5) showing the film deposition method according to the embodiment. [Figure 7] This is a cross-sectional view (6) showing the film deposition method according to the embodiment. [Figure 8] This is a cross-sectional view (7) showing the film deposition method according to the embodiment. [Modes for carrying out the invention]

[0008] Hereinafter, exemplary embodiments of the present disclosure, not limited to those described herein, will be described with reference to the attached drawings. In all attached drawings, identical or corresponding members or components are denoted by the same or corresponding reference numerals, and redundant descriptions are omitted.

[0009] [Film formation method] The film deposition method according to the embodiment will be described with reference to Figures 1 to 8. Figure 1 is a flowchart of the film deposition method according to the embodiment. Figures 2 to 8 are cross-sectional views showing the film deposition method according to the embodiment. The film deposition method according to the embodiment has steps S11 to S17 shown in Figure 1.

[0010] In step S11, a substrate 100 is prepared as shown in Figure 2. The substrate 100 has a silicon substrate 110. The surface of the silicon substrate 110 is provided with a plurality of recesses 120 having different opening widths. In the example in Figure 2, the surface of the silicon substrate 110 is provided with a recess 120a having a first opening width W1 and a recess 120b having a second opening width W2. The second opening width W2 is wider than the first opening width W1. Recesses 120a and 120b are, for example, trenches. In this specification, recesses 120a and 120b are collectively referred to as recesses 120. A silicon oxide film 130 is provided on the surface of the recesses 120. The silicon oxide film 130 is an example of an insulating film.

[0011] In step S12, as shown in Figure 3, a silicon film 140 is formed along the surface of the multiple recesses 120. In step S12, the silicon film 140 may be formed so as to cover the surface of the silicon oxide film 130. In step S12, the silicon film 140 may be formed so as not to block the openings of each of the multiple recesses 120. The silicon film 140 is amorphous. The silicon film 140 is undoped. For example, the silicon film 140 can be formed by chemical vapor deposition (CVD) using silicon source gas. The silicon film 140 is an example of a silicon-containing film.

[0012] In step S13, as shown in Figure 4, the carbon film 150 is used to fill the recesses 120. In step S13, the carbon film 150 may be formed to cover the entire silicon film 140 formed along the surface of the recesses 120. In step S13, the carbon film 150 may be formed to completely fill the recesses 120. For example, the carbon film 150 is a spin-on carbon film. In this case, it is easier to fill the recesses 120 with the carbon film 150. The carbon film 150 is an example of a carbon-containing film.

[0013] In step S14, as shown in Figure 5, the silicon film 140 formed on the upper part of the multiple recesses 120 is exposed from the carbon film 150 by performing anisotropic etching on the carbon film 150 in the thickness direction of the substrate 100. In step S14, the silicon film 140 formed on the upper part of the upper part of the recesses 120 and the lower part of the sides of the recesses 120 may be exposed from the carbon film 150 without exposing the silicon film 140 formed on the bottom and lower side of the recesses 120. For example, by supplying oxygen plasma to the substrate 100, the silicon film 140 formed on the upper part of the multiple recesses 120 can be exposed from the carbon film 150. When using oxygen plasma, it is easy to remove the carbon film 150 formed on the top and sides of the recesses 120 without removing the carbon film 150 formed on the bottom of the recesses 120. However, by supplying hydrogen plasma to the substrate 100, the silicon film 140 formed on the upper part of the multiple recesses 120 can be exposed from the carbon film 150.

[0014] In step S15, as shown in Figure 6, the silicon film 140 is etched using the carbon film 150 as an etching mask, thereby removing the silicon film 140 exposed from the carbon film 150. For example, the silicon film 140 exposed from the carbon film 150 can be removed by supplying a fluorine-containing gas to the silicon film 140. When removing the silicon film 140, the substrate 100 may be maintained at a temperature of 150°C or lower. In this case, the carbon film 150 will not sublimate.

[0015] In step S16, the carbon film 150 is removed from within the multiple recesses 120, as shown in Figure 7. In step S16, the carbon film 150 is selectively removed so as not to remove the silicon film 140. As a result, the silicon film 140 is selectively left on the bottom surface of each of the multiple recesses 120 having different opening widths. That is, the silicon film 140 can be selectively formed on the bottom surface of each of the multiple recesses 120 having different opening widths. For example, by supplying oxygen plasma to the carbon film 150, the carbon film 150 can be selectively removed from the silicon film 140.

[0016] In step S17, as shown in FIG. 8, the plurality of recesses 120 from which the carbon film 150 has been removed are filled with a germanium film 160. In step S17, the plurality of recesses 120 may be filled with the germanium film 160 by chemical vapor deposition using a germanium-containing gas. In the chemical vapor deposition using a germanium-containing gas, the germanium film 160 does not deposit or hardly deposits on the surface of the silicon oxide film 130, whereas the germanium film 160 deposits on the surface of the silicon film 140. Therefore, the germanium film 160 is selectively formed on the surface of the silicon film 140 with respect to the surface of the silicon oxide film 130. As a result, the germanium film 160 can be grown bottom-up from the bottom surface side to the opening side of the recess 120. The germanium film 160 is amorphous. The germanium film 160 is undoped. The germanium film 160 is an example of a germanium-containing film.

[0017] As described above, according to the film formation method according to the embodiment, first, in step S12, the silicon film 140 is formed along the surfaces of the plurality of recesses 120 having different opening widths. Next, in step S13, the plurality of recesses 120 in which the silicon film 140 is formed are filled with the carbon film 150. Next, in step S14, anisotropic etching is performed on the carbon film 150 in the thickness direction of the substrate 100, so that the silicon film 140 formed on the upper portions of the plurality of recesses 120 is exposed from the carbon film 150. Next, in step S15, the silicon film 140 is etched using the carbon film 150 as an etching mask, so that the silicon film 140 exposed from the carbon film 150 is removed. In this case, the silicon film 140 remains selectively on the bottom surface of each of the plurality of recesses 120. That is, the silicon film 140 can be selectively formed on the bottom surface of each of the plurality of recesses 120 having different opening widths. As a result, the germanium film 160 can be grown bottom-up from the bottom surface side to the opening side of the recess 120.

[0018] On the other hand, there is a method in which a silicon film is formed over the entire concave portion, and then, by etching using chlorine gas, the silicon film on the upper part of the inner wall of the concave portion is removed while leaving the silicon film on the bottom surface of the concave portion, and then a silicon film is selectively formed on the silicon film remaining on the bottom surface of the concave portion. When forming silicon films in a plurality of concave portions having different opening widths using this method, it is difficult to leave silicon films having the same or substantially the same thickness on the bottom surfaces of the plurality of concave portions having different opening widths. Therefore, when subsequently embedding the germanium film 160 in the concave portion, it is difficult to grow the germanium film 160 in a bottom-up manner.

[0019] 〔Type of Gas〕 Specific examples of the gas used in the film formation method according to the embodiment will be described.

[0020] As the silicon source gas used when forming the silicon film 140, any gas can be used as long as it is applicable to chemical vapor deposition. For example, one or a combination of a plurality of hydrosilane gases, halogen-containing silicon gases, and aminosilane-based gases can be used. Examples of the hydrosilane gas include SiH4, Si2H6, and Si3H8. Examples of the halogen-containing silicon gas include fluorine-containing silicon gases such as SiF4, SiHF3, SiH2F2, and SiH3F, chlorine-containing silicon gases such as SiCl4, SiHCl3, SiH2Cl2, and SiH3Cl, and bromine-containing gases such as SiBr4, SiHBr3, SiH2Br2, and SiH3Br. Examples of the aminosilane-based gas include DIPAS (diisopropylaminosilane), 3DMAS (trisdimethylaminosilane), and BTBAS (bis-tert-butylaminosilane).

[0021] As the fluorine-containing gas used when removing the silicon film 140, for example, a mixed gas of fluorine gas and nitrogen gas can be used.

[0022] The germanium raw material gas used when forming the germanium film 160 can be any gas applicable to chemical vapor deposition, such as germanium hydride gas, halogen-containing germanium gas, or aminogermane gas. Examples of germanium hydride gases include GeH4, Ge2H6, and Ge3H8. Examples of halogen-containing germanium gases include fluorine-containing germanium gases such as GeF4, GeHF3, GeH2F2, and GeH3F; chlorine-containing germanium gases such as GeCl4, GeHCl3, GeH2Cl2, and GeH3Cl; and bromine-containing gases such as GeBr4, GeHBr3, GeH2Br2, and GeH3Br. Examples of aminogermane gases include DMAG (dimethylaminogermane), DEAG (diethylaminogermane), BDMAG (bisdimethylaminogermane), BDEAG (bisdiethylaminogermane), and 3DMAG (trisdimethylaminogermane).

[0023] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The above embodiments may be omitted, replaced, or modified in various ways without departing from the scope and spirit of the appended claims.

[0024] In the embodiments described above, the case in which the insulating film is a silicon oxide film 130 was explained, but the disclosure is not limited thereto. The insulating film may also be a silicon nitride film or a high-dielectric constant (high-k) film.

[0025] In the above embodiments, the case in which the silicon-containing film is an undoped and amorphous silicon film 140 was described, but the disclosure is not limited thereto. The silicon-containing film can be any film on which a germanium-containing film can be deposited. For example, the silicon-containing film may contain p-type impurities such as boron (B) and n-type impurities such as phosphorus (P). For example, the silicon-containing film may contain carbon (C). For example, the silicon-containing film may contain germanium (Ge).

[0026] In the embodiments described above, the case in which the carbon-containing film is a carbon film 150 was explained, but the disclosure is not limited thereto. For example, the carbon-containing film may contain nitrogen (N).

[0027] In the embodiments described above, the case in which the germanium-containing film is a germanium film 160 was explained, but this disclosure is not limited thereto. For example, the germanium film may be a silicon germanium film. [Explanation of symbols]

[0028] 100 circuit boards 120 recess 140 Silicone film 150 carbon film

Claims

1. Prepare a substrate in which multiple recesses with different opening widths are formed, Forming a silicon-containing film along the surface of the multiple recesses, The plurality of recesses in which the silicon-containing film is formed are filled with a carbon-containing film, By performing anisotropic etching on the carbon-containing film in the thickness direction of the substrate, the silicon-containing film formed on the upper part of the plurality of recesses is exposed from the carbon-containing film. By etching the silicon-containing film using the carbon-containing film as an etching mask, the silicon-containing film exposed from the carbon-containing film is removed. A film formation method having the following characteristics.

2. The embedding with the carbon-containing film includes forming the carbon-containing film so as to cover the entire silicon-containing film formed along the surface of the plurality of recesses. The method for forming a film according to claim 1.

3. The act of filling with the carbon-containing film includes completely filling the multiple recesses with the carbon-containing film. The method for forming a film according to claim 1.

4. Exposing the carbon-containing film includes supplying oxygen plasma to the carbon-containing film. The method for forming a film according to claim 1.

5. Removing the silicon-containing film includes supplying a fluorine-containing gas to the silicon-containing film. The method for forming a film according to claim 1.

6. The carbon-containing film is removed from the plurality of recesses from which the silicon-containing film has been removed, The process involves supplying a germanium-containing gas into the plurality of recesses from which the carbon-containing film has been removed, and forming a germanium-containing film on the silicon-containing film remaining in the plurality of recesses. Having, The method for forming a film according to claim 1.

7. The silicon-containing film is an amorphous silicon film. A method for forming a film according to any one of claims 1 to 6.

8. The carbon-containing film is a spin-on carbon film. A method for forming a film according to any one of claims 1 to 6.

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