Method for producing semiconductor wafer

Abstract

To provide a method for producing a semiconductor wafer containing silicon carbide crystals (SiC crystals) having a large surface roughness by a simple process.SOLUTION: A method for producing a semiconductor wafer having, on the surface thereof, protrusions made of silicon carbide crystals, the method comprising a step of forming, on a silicon substrate, a silicon film containing carbon at a first temperature, a step of precipitating silicon carbide crystals in the silicon film by annealing the silicon substrate on which the silicon film has been formed at a second temperature, and a step of polishing the silicon film on the annealed silicon substrate to produce a semiconductor wafer in which protrusions made of the silicon carbide crystals are formed on the silicon substrate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a semiconductor wafer. [Background technology]

[0002] Diamond is attracting attention as a next-generation semiconductor material. Silicon carbide (SiC) is seen as a promising material for the seed layer of diamond growth (the substrate for growing single-crystal diamond), and it is known that diamond grows particularly easily on SiC with a rough surface. However, SiC is difficult to process, and it has been difficult to intentionally grind the surface to increase the surface roughness.

[0003] As a method for manufacturing a substrate for growing a diamond single crystal, a method has been proposed in which protrusions derived from impurities are formed by etching, taking advantage of the difference in etching rates between silicon and impurities.

[0004] Furthermore, a method for producing carbon-derived impurity SiC has been proposed, which includes the steps of: subjecting a silicon single crystal substrate to RTA treatment in a carbon-containing gas atmosphere to cause carbon to adhere to the surface of the silicon single crystal substrate; reacting the carbon with the silicon single crystal substrate to form a 3C-SiC single crystal film on the surface of the silicon single crystal substrate; subjecting the silicon single crystal substrate on which the 3C-SiC single crystal film has been formed to RTA treatment in an oxidizing atmosphere to oxidize the 3C-SiC single crystal film to form an oxide film and diffuse carbon inward into the silicon single crystal substrate; and removing the oxide film (Patent Document 1).

[0005] Furthermore, Patent Document 2 describes a method for manufacturing a substrate for growing a single crystal diamond thin film, in which carbon ions are implanted at an appropriate ion current density into a single crystal substrate maintained at a high temperature, and a layer of diamond crystal fine particles that is epitaxially formed on the surface and / or near the surface of the ion-implanted portion of the single crystal substrate is formed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-038444 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-352537 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in view of the above circumstances, and has an object to provide a method for manufacturing a semiconductor wafer including silicon carbide crystal (SiC crystal) with a large surface roughness using a simple process. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a semiconductor wafer having protrusions made of silicon carbide crystals on its surface, comprising the steps of: forming a silicon film containing carbon on a silicon substrate at a first temperature; annealing the silicon substrate on which the silicon film has been formed at a second temperature to precipitate silicon carbide crystals in the silicon film; and polishing the silicon film on the annealed silicon substrate to produce a semiconductor wafer having protrusions made of silicon carbide crystals formed on the silicon substrate.

[0009] This method involves depositing a silicon film containing carbon, then heat treating it to precipitate SiC crystals in the silicon film, and then utilizing the difference in polishing rate between the silicon film and the silicon carbide crystals to form SiC crystal protrusions on the surface.This method therefore improves processability and makes it possible to manufacture semiconductor wafers containing SiC crystals with high surface roughness.

[0010] In this case, it is preferable that the second temperature is higher than the first temperature.

[0011] By setting the temperature at such a level, it is possible to more efficiently precipitate silicon carbide crystals in the carbon-containing silicon film.

[0012] The first temperature is preferably set to 400°C to 1000°C.

[0013] Furthermore, at this time, it is more preferable that the first temperature is set to 600°C to 800°C.

[0014] By forming a silicon film containing carbon at such a first temperature, it is possible to efficiently form a silicon film containing carbon from which silicon carbide crystals can be precipitated.

[0015] The carbon-containing silicon film is formed by oxidizing the silicon film so that the carbon atom concentration is 1.0×10 19 atoms / cm 3 That's it, 5.0 x 10 21 atoms / cm 3 It is preferable to form it as follows:

[0016] Furthermore, at this time, the carbon-containing silicon film is formed by oxidizing the silicon film so that the carbon atom concentration is 1.0×10 20 atoms / cm 3 That's it, 1.0 x 10 21 atoms / cm 3 It is more preferable to form it as follows:

[0017] It is practically preferable to set the carbon atom concentration of the carbon-doped silicon film within this range.

[0018] Furthermore, it is preferable that the polishing stock removal in the step of polishing the silicon film is 3 nm or more and less than the film thickness of the silicon film.

[0019] By setting the polishing stock removal to 3 nm or more, it is possible to more reliably expose the irregularities caused by the protrusions made of silicon carbide crystals on the surface of the semiconductor wafer. [Effects of the Invention]

[0020] According to the present invention, a silicon film containing carbon is formed, followed by heat treatment to precipitate SiC crystals in the silicon film, and then the difference in polishing rate between the silicon film and the silicon carbide crystals is utilized to form SiC crystal protrusions on the surface, which improves processability and allows the production of semiconductor wafers containing SiC crystals with high surface roughness. The present invention is also advantageous in that the density and roughness of the SiC crystals can be adjusted by the concentration of carbon contained in the silicon film and the heat treatment conditions. [Brief explanation of the drawings]

[0021] [Figure 1] 1A to 1C are cross-sectional views showing steps in an example of a method for producing a semiconductor wafer according to the present invention. [Figure 2] 1 is an AFM image of the surface of a semiconductor wafer produced in Example 2. [Figure 3] 1 is an AFM image of the surface of a semiconductor wafer produced in Example 3. [Figure 4] 1 is an AFM image of the surface of a semiconductor wafer produced in Example 4. DETAILED DESCRIPTION OF THE INVENTION

[0022] As described above, there has been a demand for the development of a method for manufacturing semiconductor wafers containing silicon carbide crystals (SiC crystals) with large surface roughness using a simple process.

[0023] As a result of extensive research into the above-mentioned problems, the inventors discovered a method in which a silicon film containing carbon is formed on a silicon substrate, followed by heat treatment to precipitate SiC crystals in the silicon film, and then the difference in polishing rate between the silicon film and the silicon carbide crystals is utilized to form SiC crystal protrusions on the surface, thereby completing the present invention.

[0024] That is, the present invention is a method for manufacturing a semiconductor wafer having protrusions made of silicon carbide crystals on its surface, comprising: a step (step S1) of forming a silicon film containing carbon on a silicon substrate at a first temperature; a step (step S2) of annealing the silicon substrate on which the silicon film has been formed at a second temperature to precipitate silicon carbide crystals in the silicon film; and a step (step S3) of polishing the silicon film on the annealed silicon substrate to produce a semiconductor wafer having protrusions made of silicon carbide crystals formed on the silicon substrate.

[0025] The present invention will be described in detail below, but the present invention is not limited thereto.

[0026] Figure 1 shows cross-sectional views of each step in an example of a method for manufacturing a semiconductor wafer according to the present invention. In the present invention, a semiconductor wafer is obtained by carrying out steps S1 to S3. The following description will be made with reference to Figure 1. Note that Figure 1 is a schematic view for the purpose of explanation, and actual dimensions may differ.

[0027] <Process S1> Step S1 is a step of forming a carbon-containing silicon film 12 on a silicon substrate 10 at a first temperature, as shown in FIG. 1(a).

[0028] In this step, first, a silicon substrate 10 is prepared. The silicon substrate 10 is not particularly limited, but is preferably a single crystal silicon substrate. The single crystal silicon substrate is also not particularly limited, and may be a CZ single crystal substrate or an FZ single crystal substrate. It may be undoped or doped. If doped, it may be n-type or p-type. If it is n-type, it may be doped with, for example, P, Sb, or As. If it is p-type, it may be doped with, for example, B, Al, or Ga. There are also no particular limitations on the surface orientation, diameter, resistivity, etc. of the substrate.

[0029] Next, a carbon-doped silicon film 12 containing carbon (carbon-doped silicon film) is formed on the prepared silicon substrate at a first temperature. The silicon film 12 is a silicon epitaxial layer, and can be formed by, for example, CVD, preferably RP-CVD (reduced pressure CVD). The source gases used in this process include, for example, monomethylsilane or trimethylsilane as a carbon source and dichlorosilane or monosilane as a silicon source. However, the source gases are not limited to these. The film formation temperature is the "first temperature," and can be, for example, 400 to 1000°C, preferably 600 to 800°C, but is not limited thereto. The carbon atom concentration doped into the silicon layer can be adjusted by the flow rate of the source gas and the film formation temperature. The pressure during CVD can be 1 to 80 Torr (133 to 10640 Pa).

[0030] The carbon atom concentration of the carbon-containing silicon film 12 is preferably 1.0×10 19 atoms / cm 3 That's it, 5.0 x 10 21 atoms / cm 3 and more preferably 1.0 x 10 20 atoms / cm 3 That's it, 1.0 x 10 21 atoms / cm 3 It can be formed as follows: The carbon atom concentration can be confirmed by SIMS (Secondary Ion Mass Spectroscopy).

[0031] The thickness of the carbon-containing silicon film 12 is not particularly limited, but can be, for example, 10 to 1000 nm, preferably 20 to 500 nm, and more preferably 30 to 200 nm.

[0032] <Process S2> Step S2 is a step of precipitating silicon carbide crystals 14 in the carbon-containing silicon film 12 by annealing the silicon substrate 10 on which the carbon-containing silicon film 12 has been formed at a second temperature, as shown in FIG. 1(b).

[0033] At this time, it is preferable that the second temperature in step S2 is set to be higher than the first temperature in step S1. By doing so, it is possible to effectively precipitate silicon carbide crystals 14. The second temperature when annealing can be set to, for example, 800°C or higher, and is preferably 1000 to 1200°C.

[0034] The annealing in step S2 can be performed using the same apparatus as in step S1, or can be performed using other apparatuses. The annealing time is not particularly limited as long as it can precipitate silicon carbide crystals 14, but can be, for example, 1 minute or more, and from the viewpoint of productivity, 12 hours or less.

[0035] <Process S3> Step S3 is a step of producing a semiconductor wafer 20 in which protrusions 24 made of silicon carbide crystals are formed on the silicon substrate 10 by polishing the silicon film 12 on the annealed silicon substrate 10, as shown in FIG. 1(c).

[0036] 1(c) can be formed on the surface of the semiconductor wafer 20. In other words, by polishing the silicon film 12, which has a high polishing rate and includes the silicon carbide crystals 14, only the silicon carbide crystals 14, which have a low polishing rate, remain, and a roughened shape with protrusions 24 made of silicon carbide crystals can be formed on the surface of the semiconductor wafer 20.

[0037] The polishing allowance for polishing the silicon film 12 in step S3 is not limited as long as it is within a range that allows unevenness due to the protrusions 24 made of silicon carbide crystals to be formed on the surface of the semiconductor wafer 20, but is preferably 3 nm or more and less than the film thickness of the silicon film 12. By setting the polishing allowance to 3 nm or more, it is possible to more reliably expose the unevenness due to the protrusions 24 made of silicon carbide crystals on the surface of the semiconductor wafer 20. Furthermore, by setting the polishing allowance to be less than the film thickness of the silicon film 12, it is possible to prevent the entire thickness of the silicon carbide crystals 14 precipitated in step S2 from being polished away.

[0038] The polishing in step S3 can be performed by the usual CMP (chemical mechanical polishing) performed on silicon substrates. In particular, the polishing slurry is not particularly limited as long as it can efficiently polish the silicon film, but for example, a slurry containing silicon dioxide as abrasive grains and potassium hydroxide as alkali can be used.

[0039] By performing the above steps S1 to S3, the present invention can manufacture a semiconductor wafer 20 including protrusions 24 made of silicon carbide crystals with a large surface roughness. Furthermore, the method of the present invention is highly workable and can manufacture a semiconductor wafer including silicon carbide crystals with a large surface roughness.

[0040] The present invention is also advantageous in that the density and roughness of the silicon carbide crystals can be adjusted by the concentration of carbon contained in silicon film 12 in step S1 and the heat treatment conditions in steps S2 and S3. Those skilled in the art can easily adjust the density, size, and surface roughness of the silicon carbide crystals through experimentation. [Example]

[0041] EXAMPLES The present invention will be specifically explained below using examples and comparative examples, but the present invention is not limited to these.

[0042] 1(a) to 1(c), steps S1 to S3 in the semiconductor wafer manufacturing method of the present invention were performed in Examples 1 to 5. On the other hand, in Comparative Example 1 below, only steps S1 and S2 in the semiconductor wafer manufacturing method of the present invention were performed, and in Comparative Example 2, only step S1 was performed.

[0043] Example 1 A C (carbon) non-doped Si substrate with a diameter of 300 mm and a plane orientation (100) was prepared as the silicon substrate 10. A carbon-containing silicon film 12 (C-doped Si layer, carbon atom concentration: 1.0×10) was formed on the silicon substrate 10 by RP-CVD in a mixed gas atmosphere containing SiH and SiH(CH) under conditions of 700°C and 5 Torr. 19 atoms / cm 3 ) was grown to a thickness of 1 μm (step S1). Thereafter, the temperature was raised to 1050°C and annealing was performed (step S2). The annealed silicon substrate 10 was removed from the CVD apparatus, and the silicon film 12 was polished by 100 nm using CMP to produce a semiconductor wafer 20 (step S3). Thereafter, the number of protrusions 24 made of silicon carbide crystals within a 1 μm x 1 μm square (area) was counted using an AFM (atomic force microscope), and there were 158 protrusions.

[0044] Example 2 The carbon concentration of the silicon substrate 10 (non-C doped Si substrate) is 1.0 × 10 20 atoms / cm 3 When the semiconductor wafer 20 was manufactured under the same conditions as in Example 1 except for the above, the number of SiC protrusions in an AFM 1 μm×1 μm square (area) was 798.

[0045] Example 3 The carbon concentration of the silicon substrate 10 (non-C doped Si substrate) is 5.0 × 10 20 atoms / cm 3 When the semiconductor wafer 20 was manufactured under the same conditions as in Example 1 except for the above, the number of SiC protrusions in an AFM 1 μm×1 μm square (area) was 1,256.

[0046] Example 4 The carbon concentration of the silicon substrate 10 (non-C doped Si substrate) is 1.0 × 10 21 atoms / cm 3 When the semiconductor wafer 20 was manufactured under the same conditions as in Example 1 except for the above, the number of SiC protrusions in an AFM 1 μm×1 μm square (area) was 655.

[0047] Example 5 The carbon concentration of the silicon substrate 10 (non-C doped Si substrate) is 5.0 × 10 21 atoms / cm 3 When the semiconductor wafer 20 was manufactured under the same conditions as in Example 1 except for the above, the number of SiC protrusions in an AFM 1 μm×1 μm square (area) was 122.

[0048] (Comparative Example 1) A C-doped Si substrate was prepared as the silicon substrate. A carbon-doped silicon film (C-doped Si layer, carbon atom concentration: 5.0 × 10) was deposited on the silicon substrate using RP-CVD in a mixed gas atmosphere containing SiH and SiH(CH) at 700 °C and 5 Torr. 20 atoms / cm 3 ) was grown to a thickness of 1 μm (corresponding to step S1). Thereafter, the silicon substrate was removed from the CVD apparatus, and the silicon film 12 was polished by 100 nm using CMP to produce a semiconductor wafer (corresponding to step S3). That is, in Comparative Example 1, a semiconductor wafer was produced without performing step S2. Thereafter, the number of protrusions made of silicon carbide crystals within a 1 μm x 1 μm square (area) was counted using an AFM (atomic force microscope), and the result was 0.

[0049] (Comparative Example 2) A C-doped Si substrate was prepared as the silicon substrate. A carbon-doped silicon film (C-doped Si layer, carbon atom concentration: 5.0 × 10) was deposited on the silicon substrate using RP-CVD in a mixed gas atmosphere containing SiH and SiH(CH) at 700 °C and 5 Torr. 20 atoms / cm 3) was grown to a thickness of 1 μm (corresponding to step S1). Thereafter, the silicon substrate was removed from the CVD apparatus and used as the fabricated semiconductor wafer. That is, in Comparative Example 2, a semiconductor wafer was fabricated without performing steps S2 and S3. Thereafter, the number of protrusions made of silicon carbide crystals within a 1 μm x 1 μm square (area) was counted using an AFM (atomic force microscope), and the result was 0.

[0050] The results of Examples 1 to 5 and Comparative Examples 1 and 2 (the number of protrusions made of silicon carbide crystals per 1 μm×1 μm square (area) on the semiconductor wafer surface) are summarized in Table 1. In Examples 1 to 5, the carbon concentration in the number of protrusions made of silicon carbide crystals per 1 μm×1 μm square (area) after epitaxial growth, annealing, and polishing was 1.0×10 21 , 5.0×10 21 This is thought to be because when a silicon film containing carbon is annealed, the size and density of the precipitated silicon carbide crystals increase, and when polished, less silicon is removed, resulting in smaller irregularities measured as protrusions.

[0051] [Table 1]

[0052] 2 to 4 show AFM images of the surfaces of the semiconductor wafers 20 produced in Examples 2 to 4, respectively. Each figure shows a 1 μm x 1 μm square (area), and the height of the irregularities is indicated by the shade of color. From FIGS. 2 to 4, it can be seen that irregularities of silicon carbide crystals are formed in each Example.

[0053] In this way, protrusions made of silicon carbide crystals were formed on the semiconductor wafer 20 manufactured by carrying out steps S1 to S3 of the present invention. Furthermore, the protrusion density can be adjusted by adjusting the conditions.

[0054] [1]: A method for manufacturing a semiconductor wafer having protrusions made of silicon carbide crystals on its surface, comprising: forming a carbon-containing silicon film on a silicon substrate at a first temperature; annealing the silicon substrate on which the silicon film has been formed at a second temperature to precipitate silicon carbide crystals in the silicon film; polishing the silicon film on the annealed silicon substrate to produce a semiconductor wafer having protrusions made of the silicon carbide crystals formed on the silicon substrate; A method for manufacturing a semiconductor wafer, comprising: [2]: The method for producing a semiconductor wafer according to [1] above, wherein the second temperature is higher than the first temperature. [3]: The method for producing a semiconductor wafer according to [1] or [2] above, wherein the first temperature is 400°C to 1000°C. [4]: The method for producing a semiconductor wafer according to [3] above, wherein the first temperature is 600°C to 800°C. [5]: The carbon-containing silicon film is formed by subjecting the carbon atom concentration to 1.0×10 19 atoms / cm 3 That's it, 5.0 x 10 21 atoms / cm 3 A method for manufacturing a semiconductor wafer according to any one of [1] to [4] above, which is formed as follows: [6]: The carbon-containing silicon film is formed by subjecting the carbon atom concentration to 1.0×10 20 atoms / cm 3 That's it, 1.0 x 10 21 atoms / cm 3 The method for manufacturing a semiconductor wafer according to [5] above, which is formed as follows: [7]: The method for manufacturing a semiconductor wafer according to any one of [1] to [6] above, wherein the polishing amount in the step of polishing the silicon film is 3 nm or more and less than the film thickness of the silicon film.

[0055] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention. [Explanation of symbols]

[0056] 10...silicon substrate, 12...carbon-containing silicon film, 14...precipitated silicon carbide crystals, 20...Semiconductor wafer 24...Protrusions made of silicon carbide crystals.

Claims

1. A method for manufacturing a semiconductor wafer having protrusions made of silicon carbide crystals on a surface thereof, comprising: forming a carbon-containing silicon film on a silicon substrate at a first temperature; annealing the silicon substrate on which the silicon film has been formed at a second temperature to precipitate silicon carbide crystals in the silicon film; polishing the silicon film on the annealed silicon substrate to produce a semiconductor wafer having protrusions made of the silicon carbide crystals formed on the silicon substrate; A method for manufacturing a semiconductor wafer, comprising:

2. 2. The method for producing a semiconductor wafer according to claim 1, wherein the second temperature is set to be higher than the first temperature.

3. 2. The method for producing a semiconductor wafer according to claim 1, wherein the first temperature is set to 400°C to 1000°C.

4. 4. The method for producing a semiconductor wafer according to claim 3, wherein the first temperature is set to 600°C to 800°C.

5. The carbon-containing silicon film is formed by subjecting the carbon atom concentration to 1.0×10 １９ atoms / cm ３ That's it, 5.0 x 10 ２１ atoms / cm ３ 2. The method for manufacturing a semiconductor wafer according to claim 1, wherein the semiconductor wafer is formed as follows:

6. The carbon-containing silicon film is formed by subjecting the carbon atom concentration to 1.0×10 ２０ atoms / cm ３ That's it, 1.0 x 10 ２１ atoms / cm ３ 6. The method for manufacturing a semiconductor wafer according to claim 5, wherein the semiconductor wafer is formed as follows:

7. 7. The method for manufacturing a semiconductor wafer according to claim 1, wherein a polishing stock removal in the step of polishing the silicon film is set to 3 nm or more and less than a film thickness of the silicon film.

Images