Film formation method and film formation device

Abstract

To provide a technology capable of controlling a film shape in forming a film on a surface with an uneven structure.SOLUTION: A film formation method according to an embodiment of the present disclosure comprises: preparing a substrate having an uneven structure; forming a first film containing carbon on the surface of the uneven structure; supplying a nitrogen-containing plasma to the substrate and forming, on a portion of the surface of the first film, a low-carbon region in which the concentration of carbon is reduced; and supplying a halogen-containing material to the substrate and etching the low-carbon region.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a film formation method and a film formation apparatus. [Background technology]

[0002] Techniques for filling recesses formed in a substrate with a silicon-containing film have been disclosed (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-174902 [Patent Document 2] Japanese Patent Publication No. 2023-065305 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a technique that can control the shape of a film when it is formed on the surface of a concave-convex structure. [Means for solving the problem]

[0005] A film formation method according to one embodiment of the present disclosure includes preparing a substrate having a textured structure, forming a first film containing carbon on a surface of the textured structure, supplying a plasma containing nitrogen to the substrate to form a low-carbon region in a portion of the surface of the first film where the concentration of carbon is reduced, and supplying a halogen-containing substance to the substrate to etch the low-carbon region. [Effects of the Invention]

[0006] According to the present disclosure, it is possible to control the shape of a film when forming the film on the surface of a concave-convex structure. [Brief explanation of the drawings]

[0007] [Figure 1]2 is a flowchart illustrating a film forming method according to an embodiment. [Figure 2] 2 is a flowchart showing an example of step S3 in FIG. 1. [Figure 3] 1 is a cross-sectional view (1) showing a film forming method according to an embodiment. [Figure 4] FIG. 2 is a cross-sectional view (2) showing the film forming method according to the embodiment. [Figure 5] FIG. 3 is a cross-sectional view (3) showing the film forming method according to the embodiment. [Figure 6] 1 is a cross-sectional view showing a film forming apparatus according to an embodiment. [Figure 7] FIG. 10 is a diagram showing the relationship between the carbon concentration of a SiCN film and the etching amount. 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] [Film formation method] A film formation method according to an embodiment will be described with reference to Fig. 1 to Fig. 5. Fig. 1 is a flowchart showing the film formation method according to the embodiment. Fig. 2 is a flowchart showing an example of step S3 in Fig. 1. Figs. 3 to 5 are cross-sectional views showing the film formation method according to the embodiment. The film formation method according to the embodiment includes steps S1 to S7 shown in Fig. 1.

[0010] Step S1 includes preparing a substrate 100, as shown in FIG. 3(a). The substrate 100 has a base substrate 101. The base substrate 101 is, for example, a silicon wafer. The base substrate 101 has a recess 102 on its surface. The recess 102 is, for example, a trench. The recess 102 may also be a hole. The recess 102 is an example of a concave-convex structure.

[0011] 3(b), step S2 includes forming a SiCN film 103 on the surface of the recess 102. Step S2 includes forming the SiCN film 103 by, for example, atomic layer deposition (ALD) in which a silicon-containing gas, a carbon-containing gas, and a nitrogen-containing gas are not simultaneously supplied to the substrate 100. In this case, the SiCN film 103 can be conformally formed on the surface of the recess 102. Step S2 may also include forming the SiCN film 103 by chemical vapor deposition (CVD) in which a silicon-containing gas, a carbon-containing gas, and a nitrogen-containing gas are simultaneously supplied to the substrate 100. When the SiCN film 103 having a desired thickness is formed on the surface of the recess 102, step S2 is terminated.

[0012] Step S3 includes supplying nitrogen-containing plasma to the substrate 100 to form a low-carbon region 104 in which the carbon concentration is reduced in a portion of the surface of the SiCN film 103. Step S3 includes steps S31 to S33 shown in FIG.

[0013] Step S31 includes determining whether or not to etch the SiCN film 103 in a V-shape. If the SiCN film 103 is etched in a V-shape (YES in step S31), plasma generated from nitrogen (N2) gas (hereinafter referred to as "N2 plasma") is supplied to the substrate 100 (step S32). Active species contained in the N2 plasma react with the SiCN film 103 to desorb carbon from the SiCN film 103. The active species contained in the N2 plasma have a short lifetime and are easily lost, making it difficult for them to reach the lower part of the recess 102. Therefore, when N2 plasma is supplied to the substrate 100, carbon is more likely to desorb from the upper part of the SiCN film 103 than from the lower part of the recess 102. As a result, as shown in FIG. 4(a), low-carbon regions 104 with reduced carbon concentration are formed on the top and side surfaces of the recess 102, but are less likely to be formed on the bottom surface of the recess 102. The low-carbon regions 104 are formed more in the upper part of the side surfaces of the recess 102 than in the lower part in the depth direction.

[0014] If the SiCN film 103 is not etched in a V-shape (NO in step S31), plasma generated from ammonia (NH) gas (hereinafter referred to as "NH plasma") is supplied to the substrate 100 (step S33). The activated species contained in the NH plasma have a long lifetime and are difficult to dissipate, so they easily reach the lower part of the recess 102. Therefore, when the NH plasma is supplied to the substrate 100, carbon is desorbed from the SiCN film 103 at the upper and lower parts of the recess 102. As a result, as shown in FIG. 5(a), low-carbon regions 104 are conformally formed along the bottom, side, and top surfaces of the recess 102. Instead of the NH plasma, plasma generated from a mixed gas of nitrogen gas and hydrogen (H) gas (hereinafter referred to as "N / H plasma") may be used. In this case, the low-carbon regions 104 are conformally formed along the bottom, side, and top surfaces of the recess 102, similar to the NH plasma.

[0015] Step S4 includes supplying hydrogen fluoride (HF) gas to the substrate 100 to etch the low-carbon region 104. Hydrogen fluoride gas has the property of etching the SiCN film 103 more effectively when the carbon concentration in the SiCN film 103 is lower. Therefore, when hydrogen fluoride gas is supplied to the substrate 100, the SiCN film 103 is hardly etched, while the low-carbon region 104 is etched and removed. That is, the low-carbon region 104 is selectively removed relative to the SiCN film 103. When hydrogen fluoride gas is supplied to the substrate 100 to which N2 plasma has been supplied, the SiCN film 103 in the recess 102 becomes V-shaped as shown in FIG. 4(b). When hydrogen fluoride gas is supplied to the substrate 100 to which NH3 plasma has been supplied, the SiCN film 103 in the recess 102 becomes shaped to conform to the surface of the recess 102 as shown in FIG. 5(b). In this way, by changing the type of plasma supplied to the substrate 100 in step S3, it is possible to control the film shape of the SiCN film 103 in the recess 102. Hydrogen fluoride gas is an example of a halogen-containing substance.

[0016] Step S5 includes determining whether steps S3 and S4 have been performed a first number of times. If the number of times has not reached the first number (NO in step S5), steps S3 and S4 are performed again. If the number of times has reached the first number of times (YES in step S5), the process proceeds to step S6. By repeating steps S3 and S4 until the number of times reaches the first number, the amount of SiCN film 103 etched increases. The first number of times may be determined according to the ratio of the depth to the width (hereinafter referred to as the "aspect ratio") of the recess 102. For example, when a recess 102 with a high aspect ratio is to be filled in a V-shape, the first number of times may be increased. In this case, the angle of the V-shape of the SiCN film 103 in the recess 102 becomes larger. Therefore, voids and seams are less likely to occur when the SiCN film 103 is filled in the recess 102.

[0017] Step S6 includes determining whether steps S2 to S5 have been performed a second number of times. If the number of times has not reached the second number of times (NO in step S6), steps S2 to S5 are performed again. If the number of times has reached the second number of times (YES in step S6), the process proceeds to step S7. In this manner, steps S2 to S5 are repeated until the number of times reaches the second number of times, thereby filling the recess 102 with the SiCN film 103. The second number of times may be determined according to the target film thickness of the SiCN film 103. The first number of times of step S5 may be changed halfway through the second number of times. For example, when filling the recess 102 in a V-shape, the first number of times may be decreased halfway through the second number of times. In this case, the SiCN film 103 can be filled in the recess 102 without generating voids or seams, while improving productivity.

[0018] Step S7 includes forming a SiCN film 103 on the surface of the recess 102. For example, as shown in FIG. 4(c), the SiCN film 103 is formed on the surface of the recess 102 until the recess 102 is filled with the SiCN film 103. This allows the recess 102 to be filled with the SiCN film 103 with few gaps such as voids and seams. Note that step S7 may not be performed, or a film other than the SiCN film 103 may be formed in step S7.

[0019] As described above, the film formation method according to the embodiment includes forming the SiCN film 103 on the surface of the recess 102, and supplying nitrogen plasma or ammonia plasma to form the low-carbon region 104 in part of the surface of the SiCN film 103. In this case, by selecting nitrogen plasma, it is possible to form the V-shaped SiCN film 103 in the recess 102, and by selecting ammonia plasma, it is possible to form the SiCN film 103 in the recess 102 so that the SiCN film 103 has a shape that conforms to the surface of the recess 102. In other words, it is possible to control the film shape when forming the SiCN film 103 in the recess 102.

[0020] [Film forming equipment] The film forming apparatus 1 according to the embodiment will be described with reference to Fig. 6. Fig. 6 is a cross-sectional view showing the film forming apparatus 1 according to the embodiment.

[0021] The film forming apparatus 1 includes a processing vessel 2. The processing vessel 2 accommodates a substrate W. The substrate W may be the substrate 100 described above. The processing vessel 2 has a substantially cylindrical shape. The processing vessel 2 is a vacuum vessel whose interior can be depressurized. An exhaust chamber 21 is provided in the center of the bottom wall of the processing vessel 2.

[0022] The exhaust chamber 21 has a generally cylindrical shape that protrudes downward. An exhaust flow path 22 is connected to the side of the exhaust chamber 21. An exhaust unit 24 is connected to the exhaust flow path 22 via a pressure adjustment unit 23. The pressure adjustment unit 23 includes a pressure adjustment valve such as a butterfly valve. The pressure adjustment unit 23 adjusts the pressure inside the processing vessel 2. The exhaust unit 24 includes a vacuum pump. The exhaust unit 24 reduces the pressure inside the processing vessel 2 via the exhaust flow path 22. A transfer port 25 is provided on the side of the processing vessel 2. The transfer port 25 is an opening through which the substrate W passes when being loaded into the processing vessel 2 and when being unloaded from the processing vessel 2. The transfer port 25 is opened and closed by a gate valve 26.

[0023] A mounting table 3 is provided within the processing chamber 2. The mounting table 3 holds the substrate W in a substantially horizontal position. The mounting table 3 has a substantially circular shape in a plan view. The mounting table 3 is supported by a support member 31. A recess 32 is provided on the surface of the mounting table 3. The recess 32 has a substantially circular shape in a plan view. The substrate W is mounted in the recess 32. The recess 32 has an inner diameter slightly larger than the diameter of the substrate W. The recess 32 has a depth substantially equal to the thickness of the substrate W. The mounting table 3 is made of a ceramic material such as aluminum nitride (AlN). The mounting table 3 may also be made of a metal material such as nickel (Ni). Instead of the recess 32, an annular guide member for guiding the peripheral edge of the substrate W may be provided on the surface of the mounting table 3.

[0024] A lower electrode 33 is provided inside the mounting table 3. An RF power supply 34 is connected to the lower electrode 33 via a matching box 35. The RF power supply 34 supplies a first RF (Radio Frequency) power to the lower electrode 33. The first RF power is bias RF power for attracting ions into the substrate W. The first RF power has a frequency in the range of 100 kHz to 60 MHz, for example. A DC (Direct Current) power supply may be connected to the lower electrode 33. The DC power supply supplies bias DC power or pulsed DC power to the lower electrode 33. The lower electrode 33 may be grounded. When the entire mounting table 3 is made of metal, the entire mounting table 3 functions as the lower electrode. Therefore, the lower electrode 33 does not need to be provided inside the mounting table 3.

[0025] A temperature adjustment mechanism 36 is provided inside the mounting table 3. The temperature adjustment mechanism 36 is located below the lower electrode 33. The temperature adjustment mechanism 36 adjusts the temperature of the substrate W placed in the recess 32 to a set temperature based on a control signal from the control unit 9. The temperature adjustment mechanism 36 includes, for example, a heater. The temperature adjustment mechanism 36 may also include a fluid flow path through which a temperature adjustment fluid flows.

[0026] The mounting table 3 is provided with a plurality of (e.g., three) lifting pins 41. The plurality of lifting pins 41 hold and lift up and down the substrate W placed in the recess 32. Each lifting pin 41 is made of ceramics such as alumina (Al2O3). Each lifting pin 41 may also be made of quartz. The lower ends of the lifting pins 41 are attached to a support plate 42. The support plate 42 is connected via a lifting shaft 43 to a lifting mechanism 44 provided outside the processing chamber 2.

[0027] The lifting mechanism 44 is provided below the exhaust chamber 21. A bellows 45 is provided between the lifting mechanism 44 and an opening 21a for the lifting shaft 43 formed in the lower surface of the exhaust chamber 21. The support plate 42 has a shape that allows it to rise and fall without coming into contact with the support member 31 of the mounting table 3. The lifting mechanism 44 raises and lowers the upper ends of the lifting pins 41 between a position above the bottom surface of the recess 32 and a position below the bottom surface of the recess 32. This causes the substrate W to rise and lower between a position where it is placed on the bottom surface of the recess 32 (the position shown in FIG. 6) and a position away from the bottom surface of the recess 32 (not shown).

[0028] The lower end of the support member 31 passes through the opening 21b of the exhaust chamber 21. The lower end of the support member 31 is supported by a lifting mechanism 46 via a lifting plate 47 provided below the processing vessel 2. A bellows 48 is provided between the bottom of the exhaust chamber 21 and the lifting plate 47. This maintains the airtightness inside the processing vessel 2 even when the lifting plate 47 moves up and down.

[0029] The lifting mechanism 46 lifts and lowers the lifting plate 47, thereby lifting and lowering the mounting table 3. In this way, the gap between the mounting table 3 and the gas supply unit 5 can be adjusted.

[0030] A gas supply unit 5 is provided on a ceiling wall 27 of the processing vessel 2 via an insulating member 28. The gas supply unit 5 functions as an upper electrode. The gas supply unit 5 faces the lower electrode 33. An RF power supply 51 is connected to the gas supply unit 5 via a matching box 52. The RF power supply 51 supplies a second RF power to the gas supply unit 5. The second RF power is RF power for generating plasma required for film formation on the substrate W. The second RF power has a frequency in the range of, for example, 10 MHz to 150 MHz. When RF power is supplied from the RF power supply 51 to the gas supply unit 5, an RF electric field is generated between the gas supply unit 5 (upper electrode) and the lower electrode 33.

[0031] The gas supply unit 5 has a gas diffusion chamber 53. The gas diffusion chamber 53 has a hollow shape. A number of holes 54 are arranged, for example, evenly, on the bottom surface of the gas diffusion chamber 53 to distribute and supply the processing gas into the processing vessel 2. A heating mechanism 55 is embedded above the gas diffusion chamber 53 in the gas supply unit 5. The heating mechanism 55 includes, for example, a heater. The heating mechanism 55 heats the gas supply unit 5 to a set temperature based on a control signal from the control unit 9.

[0032] A gas supply line 6 communicates with the gas diffusion chamber 53. A gas source 61 is connected to the upstream side of the gas supply line 6 via a gas line 62. The gas source 61 includes supply sources of various process gases, a mass flow controller, and a valve. The various process gases include the process gases used in the film formation method according to the embodiment. The various process gases are introduced from the gas source 61 into the gas diffusion chamber 53 via the gas line 62.

[0033] The film forming apparatus 1 includes a control unit 9. The control unit 9 is an electronic circuit such as a CPU (Central Processing Unit), FPGA (Field Programmable Gate Array), or ASIC (Application Specific Integrated Circuit). The control unit 9 executes various control operations described in this specification by executing instruction codes stored in a memory or by being a circuit designed for a specific application.

[0034] [Experimental results] Substrates having SiCN films with different carbon concentrations on their surfaces were prepared and placed on the mounting table 3 installed in the processing chamber 2 of the film formation apparatus 1. The carbon concentrations of the SiCN films were 0 at%, 7 at%, 13 at%, and 33 at%. The pressure in the processing chamber 2 was then adjusted to 13.3 kPa (100 Torr) using the pressure adjustment unit 23, and the substrate temperature was adjusted to 450°C using the temperature adjustment mechanism 36. Hydrogen fluoride gas was then supplied to the substrate by the gas supply unit 5 for 25 minutes, etching the SiCN film. The etching amount of the SiCN film was calculated from the thickness of the SiCN film before and after etching.

[0035] 7 is a diagram showing the relationship between the carbon concentration of the SiCN film and the etching amount, in which the horizontal axis represents the carbon concentration [at %] of the SiCN film and the vertical axis represents the etching amount [nm] of the SiCN film.

[0036] As shown in Figure 7, when the carbon concentration of the SiCN film was 0 at%, 7 at%, 13 at%, and 33 at%, the etching amount of the SiCN film was 14.8 nm, 4.3 nm, 3.2 nm, and 0.3 nm, respectively. The results in Figure 7 show that the lower the carbon concentration, the greater the etching amount of the SiCN film. These results demonstrate that by supplying hydrogen fluoride gas, the low-carbon region 104 of the SiCN film 103 can be selectively etched and removed.

[0037] 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.

[0038] In the above embodiment, the case where the concave-convex structure is a concave portion has been described, but the present disclosure is not limited thereto. Even when the concave-convex structure is a convex portion and a SiCN film is formed on the surface of the convex portion, the film shape of the SiCN film formed on the surface of the convex portion can be controlled in the same way as when the concave-convex structure is a concave portion.

[0039] In the above embodiment, the first film is a SiCN film, but the present disclosure is not limited thereto. The first film may be an amorphous carbon film. The amorphous carbon film can be formed by, for example, a CVD method. The first film may be a film containing carbon and silicon. The film containing carbon and silicon is, for example, a SiC film, a SiCN film, or a SiOCN film. The film containing carbon and silicon can be formed by, for example, an ALD method or a CVD method. The first film may be a film containing carbon and boron. The film containing carbon and boron is, for example, a BCN film. The film containing carbon and boron can be formed by, for example, an ALD method or a CVD method.

[0040] In the above embodiment, the halogen-containing substance is hydrogen fluoride gas, but the present disclosure is not limited thereto. The halogen-containing substance may be hydrogen halide, such as hydrogen chloride (HCl) gas, hydrogen bromide (HBr) gas, or hydrogen iodide (HI) gas. The halogen-containing substance may be a liquid, such as dilute hydrofluoric acid (DHF). In this case, the low-carbon region 104 can be removed by wet etching instead of dry etching.

[0041] In the above embodiment, steps S2, S3, S4, and S7 are performed in the same processing chamber, but the present disclosure is not limited to this. For example, some of steps S2, S3, S4, and S7 may be performed in different processing chambers connected by a vacuum transfer chamber.

[0042] In the above embodiment, the film forming apparatus is a single-wafer type apparatus that processes substrates one by one, but the present disclosure is not limited to this. For example, the film forming apparatus may be a batch type apparatus that processes multiple substrates at once. [Explanation of symbols]

[0043] 100 boards 101 Base substrate 102 recess 103 SiCN film 104 Low Carbon Area

Claims

1. providing a substrate having a relief structure; forming a first film containing carbon on a surface of the concave-convex structure; supplying a plasma containing nitrogen to the substrate to form a low-carbon region in which the concentration of carbon is reduced in a portion of a surface of the first film; providing a halogen-containing material to the substrate and etching the low carbon region; The film forming method includes the steps of:

2. The plasma is generated from nitrogen gas. The film forming method according to claim 1 .

3. the low carbon region is formed on the top surface and side surface of the recessed portion of the uneven structure, but is not formed on the bottom surface of the recessed portion; The film forming method according to claim 2 .

4. the low carbon region is formed more in an upper portion than in a lower portion in a depth direction on the side surface of the recess of the concave-convex structure; The film forming method according to claim 2 .

5. The plasma is generated from ammonia gas or a mixture of nitrogen gas and hydrogen gas. The film forming method according to claim 1 .

6. The low carbon region is formed on the bottom surface, side surface, and top surface of the recessed portion of the uneven structure. The film forming method according to claim 5 .

7. the first film further contains silicon; The film forming method according to claim 1 .

8. the first film is formed by atomic layer deposition; The film forming method according to claim 1 .

9. repeating forming the low carbon region and etching the low carbon region. The film forming method according to claim 1 .

10. repeating forming the first film, forming the low carbon region, and etching the low carbon region; The film forming method according to claim 1 .

11. forming the first film after etching the low carbon region. The film forming method according to claim 1 .

12. The halogen-containing substance is a hydrogen halide. The film forming method according to claim 1 .

13. the first film is a SiCN film, a SiOCN film, or a BCN film; The film forming method according to claim 1 .

14. a processing vessel for accommodating a substrate; a gas supply unit that supplies a gas into the processing chamber; A control unit; Equipped with The control unit providing a substrate having a relief structure; forming a first film containing carbon on a surface of the concave-convex structure; supplying a plasma containing nitrogen to the substrate to form a low-carbon region in which the concentration of carbon is reduced in a portion of a surface of the first film; providing a halogen-containing material to the substrate and etching the low carbon region; configured to perform Film deposition equipment.

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