Method for manufacturing an epitaxial wafer

Abstract

An object of the present invention is to provide a method for manufacturing an epitaxial wafer that defines a growth rate at which a gettering epitaxial film crystallizes into a single crystal. 【Means for Solving the Problem】 When forming a gettering epitaxial film made of silicon doped with carbon in a mixed gas atmosphere containing silicon and carbon on a silicon substrate using a reduced pressure CVD apparatus, a method for manufacturing an epitaxial wafer in which the growth rate of the gettering epitaxial film is set to 2.4 nm / sec or less.

Description

[Technical field]

[0001] The present invention relates to a method for producing an epitaxial wafer. [Background technology]

[0002] Metal contamination is known to deteriorate the electrical characteristics of semiconductor devices. To reduce the effects of metal contamination, a widely used method is to prepare a metal gettering layer to trap the metal and prevent metal contamination from reaching the device region.

[0003] Conventionally, carbon is ion-implanted into the surface of a silicon substrate in advance, and then epitaxial growth is performed on the surface, so that a metal gettering layer is fabricated mainly from the ion-implanted carbon (Patent Document 1). The method using an ion implantation device has problems such as cross-contamination and high costs.

[0004] As an alternative to the method using an ion implantation apparatus, a metal gettering layer is produced by a method of gas-doping carbon (Patent Document 2 and Patent Document 3). However, Patent Document 2 and Patent Document 3 make no mention of the growth rate, which is important in terms of productivity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-216327 A [Patent Document 2] JP 2006-216934 A [Patent Document 3] Patent No. 7487407 [Patent Document 4] Japanese Patent Application Publication No. 08-139027 [Patent Document 5] JP 2013-045805 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above problems, and has an object to provide a method for manufacturing an epitaxial wafer in which the growth rate at which a gettering epitaxial film becomes single crystallized is specified. [Means for solving the problem]

[0007] The present invention has been made to achieve the above-mentioned object, and provides a method for manufacturing an epitaxial wafer, in which, when a gettering epitaxial film made of silicon gas-doped with carbon is formed on a silicon substrate in an atmosphere of a mixed gas containing silicon and carbon using a low-pressure CVD apparatus, the growth rate of the gettering epitaxial film is set to 2.4 nm / sec or less.

[0008] According to such a method for producing an epitaxial wafer, a growth rate at which the gettering epitaxial film is single-crystallized can be achieved, thereby improving the productivity in the production of epitaxial wafers including a high-quality gettering epitaxial film.

[0009] At this time, the growth rate of the gettering epitaxial film can be set to 0.1 nm / sec or more.

[0010] This allows for a realistic growth rate for the production of industrial products.

[0011] At this time, the growth rate of the gettering epitaxial film can be set to 1.2 nm / sec or more.

[0012] This makes it possible to define a growth rate that allows a higher quality gettering epitaxial film to be grown with high productivity.

[0013] At this time, the carbon atom concentration of the gettering epitaxial film is set to 1.0×10 20 atoms / cm3 ~3.0×10 21 atoms / cm 3 The range may be:

[0014] As a result, a sufficient gettering ability can be obtained, and when a silicon epitaxial film is formed on the gettering epitaxial film, the silicon epitaxial film can have good crystallinity.

[0015] At this time, the carbon atom concentration of the gettering epitaxial film is set to 3.0×10 20 atoms / cm 3 ~1.0×10 21 atoms / cm 3 The range may be:

[0016] This makes it possible to obtain a silicon epitaxial film having excellent crystallinity while still having sufficient gettering ability.

[0017] At this time, the gettering epitaxial film can be formed under a pressure of 667 Pa to 10666 Pa.

[0018] This makes it possible to easily make the gettering epitaxial film uniform in thickness and carbon atom concentration.

[0019] At this time, the gettering epitaxial film can be formed under a pressure of 667 Pa to 2666 Pa.

[0020] This makes it possible to more reliably make the film thickness and carbon atom concentration uniform.

[0021] In this case, the gettering epitaxial film may have a thickness of 0.025 μm to 3 μm.

[0022] This makes it possible to obtain sufficient gettering ability and also to prevent the formation of a gettering epitaxial film that is thicker than necessary, thereby making it possible to manufacture epitaxial wafers at lower cost.

[0023] In this case, the gettering epitaxial film may have a thickness of 0.025 μm to 1 μm.

[0024] This makes it possible to manufacture epitaxial wafers having sufficient gettering ability at lower costs.

[0025] At this time, the gettering epitaxial film can be formed at a temperature of 700°C to 800°C.

[0026] This allows the gettering epitaxial film to be formed and the carbon to be doped efficiently.

[0027] At this time, the silicon source of the mixed gas atmosphere containing silicon and carbon is SiH 4 , SiH 2 Cl 2 , SiHCl 3 , Si 2 H 6 or SiCl 4 can be used.

[0028] Such a silicon source gas is suitable for obtaining a gettering epitaxial film containing silicon and carbon.

[0029] At this time, SiH(CH) was used as a carbon source for the mixed gas atmosphere containing silicon and carbon. 3 ) 3 , C.H. 3 SiH 3 or C 3 H 8 can be used.

[0030] Such a carbon source gas is suitable for obtaining a gettering epitaxial film containing silicon and carbon. Effect of the Invention

[0031] As described above, according to the epitaxial wafer manufacturing method of the present invention, it is possible to achieve a growth rate at which the gettering epitaxial film is single-crystallized, thereby making it possible to improve the productivity in the manufacture of epitaxial wafers including high-quality gettering epitaxial films. [Brief description of the drawings]

[0032] [Figure 1] The conditions for single crystallization or polycrystallization in XRD (X-Ray Diffraction) measurement of the epitaxial wafers produced in the examples and comparative examples are shown below. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] The present invention will be described in detail below, but the present invention is not limited thereto.

[0034] As described above, there has been a demand for a method of manufacturing an epitaxial wafer in which the growth rate at which the gettering epitaxial film becomes single crystallized is specified.

[0035] In order to solve the above problems, the present inventors used a low-pressure CVD apparatus to fabricate gettering epitaxial films containing silicon and carbon on silicon substrates under reduced pressure while changing the growth rate. Then, the crystallinity of each gettering epitaxial film was evaluated by XRD measurement, the correlation between the growth rate and the crystallinity was examined, and the growth rate at which the gettering epitaxial film becomes single crystallized was clarified.

[0036] As a result of the above investigations, the inventors have found that when a gettering epitaxial film made of silicon gas-doped with carbon is formed (hereinafter also referred to as "epitaxial growth") on a silicon substrate in an atmosphere of a mixed gas containing silicon and carbon using a low-pressure CVD apparatus, a method for manufacturing an epitaxial wafer in which the growth rate of the gettering epitaxial film is 2.4 nm / sec or less can achieve a growth rate at which the gettering epitaxial film becomes single crystallized, thereby improving the productivity in the manufacture of epitaxial wafers including high-quality gettering epitaxial films, and have completed the present invention.

[0037] The method for producing an epitaxial wafer of the present invention will now be described.

[0038] There are no particular limitations on the type of low pressure CVD (RP-CVD) apparatus that can be suitably used in the epitaxial wafer manufacturing method of the present invention, and for example, a low pressure CVD apparatus that has been conventionally used can be used.

[0039] The silicon substrate is not particularly limited, and may be obtained by slicing an ingot produced by the Czochralski method or the floating zone method, and may have a diameter of, for example, 200 to 300 mm or more. Other conditions are not particularly limited, and the substrate may be doped, the conductivity type may be p-type or n-type, and may have low resistivity or high resistivity.

[0040] Using the above-mentioned low pressure CVD apparatus, a gettering epitaxial film made of silicon gas-doped with carbon is formed on the above-mentioned silicon substrate in an atmosphere of a mixed gas containing silicon and carbon.

[0041] In the manufacturing method of the present invention, when the gettering epitaxial film is formed, the growth rate of the gettering epitaxial film is set to 2.4 nm / sec or less.

[0042] Incidentally, the growth rate of a silicon epitaxial film is usually 1.0 μm / min (=16.7 nm / sec) (paragraph

[0001] of Patent Document 4) or 3.6 μm / min (=60 nm / sec) (paragraph

[0016] of Patent Document 5), and the above-mentioned growth rate in the manufacturing method of the present invention is considerably slower than these growth rates.

[0043] According to such an epitaxial wafer manufacturing method, the growth rate can be set to such that the gettering epitaxial film becomes single crystallized, and therefore it is not necessary to slow down the growth rate more than necessary, thereby improving the productivity in the manufacture of epitaxial wafers including high-quality gettering epitaxial films.

[0044] Before forming the gettering epitaxial film, it is preferable to perform DHF cleaning and hydrogen baking on the silicon substrate to remove the native oxide film of the silicon substrate. This allows the gettering epitaxial film to grow directly on the surface of the silicon substrate.

[0045] The growth rate of the gettering epitaxial film is preferably 0.1 nm / sec or more, and more preferably 1.2 nm / sec or more. This makes it possible to set a realistic growth rate for manufacturing industrial products, and also to specify a growth rate that allows the growth of a higher quality gettering epitaxial film.

[0046] As a silicon source in a mixed gas atmosphere containing silicon and carbon, SiH 4 , SiH 2 Cl 2 , SiHCl 3 , Si 2 H 6 or SiCl 4 can be used as a carbon source, and SiH(CH 3 ) 3 , C.H. 3 SiH 3 or C 3 H8 can be used. Such gases are suitable for obtaining gettering epitaxial films containing silicon and carbon.

[0047] The carbon atom concentration of the gettering epitaxial film is 1.0×10 20 atoms / cm 3 ~3.0×10 21 atoms / cm 3 The range is preferably 3.0×10 20 atoms / cm 3 ~1.0×10 21 atoms / cm 3 It is more preferable to set the range to . As a result, a sufficient gettering ability can be obtained, and when a silicon epitaxial film is formed on the gettering epitaxial film, the silicon epitaxial film can have good crystallinity.

[0048] The gettering epitaxial film may have a thickness of preferably 0.025 μm to 3 μm, and more preferably 0.025 μm to 1 μm. This makes it possible to obtain sufficient gettering ability and also to prevent the formation of a gettering epitaxial film that is thicker than necessary, thereby making it possible to manufacture epitaxial wafers at lower cost.

[0049] The epitaxial growth is preferably carried out under a pressure of 667 Pa to 10666 Pa, and more preferably 667 Pa to 2666 Pa. This makes it possible to easily make the gettering epitaxial film uniform in thickness and carbon atom concentration.

[0050] Moreover, the epitaxial growth is preferably carried out at a temperature of 700°C to 800°C. This allows the gettering epitaxial film to be formed and the carbon to be doped efficiently. EXAMPLES

[0051] Hereinafter, the present invention will be specifically described with reference to examples, which do not limit the present invention.

[0052] (Example) On a silicon substrate with a diameter of 300 mm, using an RP-CVD apparatus, under a reduced pressure of 740 °C and 667 Pa (5 Torr), SiH 4 and SiH 3 (CH 3 ) in a mixed gas atmosphere containing silicon and carbon getter epitaxial films (carbon atom concentration: 1×10 20 , 3×10 20 , 6×10 20 , 1×10 21 , 2×10 21 , 3×10 21 atoms / cm 3 : measured by SIMS) were each formed to a thickness of 0.3 μm at growth rates of 1.2 nm / sec and 2.4 nm / sec, and epitaxial wafers were manufactured.

[0053] XRD measurements were performed to evaluate the crystallinity of the formed epitaxial film. From the results of the XRD measurements, it was determined whether the getter epitaxial film was single crystal or polycrystal.

[0054] Fig. 1 shows the conditions for single crystallization or polycrystallization in the XRD measurement of the manufactured epitaxial wafer. As shown in Fig. 1, at any carbon atom concentration, single crystallization occurred at growth rates of 1.2 nm / sec and 2.4 nm / sec.

[0055] (Comparative Example) Epitaxial wafers were manufactured under the same conditions as in the example, except that the growth rates of the getter epitaxial films were 4.8 nm / sec and 6.4 nm / sec.

[0056] To evaluate the crystallinity of the formed epitaxial film, XRD measurements and evaluations were performed in the same manner as in the example.

[0057] The evaluation results are shown in Figure 1. As shown in Figure 1, for both carbon atom concentrations, polycrystallization occurred at growth rates of 4.8 nm / sec and 6.4 nm / sec.

[0058] As described above, according to the embodiment of the present invention, the gettering epitaxial film can be single-crystallized by setting the growth rate to 2.4 nm / sec or less. In addition, since a low growth rate is not practical for manufacturing industrial products, the lower limit of the growth rate can be set to 0.1 nm / sec. From the above, the growth rate of the gettering epitaxial film can be specified as 0.1 to 2.4 nm / sec.

[0059] The present specification includes the following aspects. [1]: A method for manufacturing an epitaxial wafer, in which a gettering epitaxial film made of silicon gas-doped with carbon is formed on a silicon substrate using a low-pressure CVD apparatus in an atmosphere of a mixed gas containing silicon and carbon, and the growth rate of the gettering epitaxial film is set to 2.4 nm / sec or less. [2]: A method for producing an epitaxial wafer according to the above [1], comprising setting the growth rate of the gettering epitaxial film to 0.1 nm / sec or more. [3]: A method for producing an epitaxial wafer according to the above [1] or [2], comprising setting a growth rate of the gettering epitaxial film to 1.2 nm / sec or more. [4]: The carbon atom concentration of the gettering epitaxial film is 1.0 × 10 20 atoms / cm 3 ~3.0×10 21 atoms / cm 3 The method for producing an epitaxial wafer according to the above [1], [2] or [3], comprising the steps of: [5]: The carbon atom concentration of the gettering epitaxial film is 3.0 × 10 20 atoms / cm 3 ~1.0×10 21 atoms / cm 3The method for producing an epitaxial wafer according to the above [1], [2], [3] or [4], comprising the steps of: [6]: A method for producing an epitaxial wafer according to the above [1], [2], [3], [4] or [5], comprising forming the gettering epitaxial film under a pressure of 667 Pa to 10,666 Pa. [7]: A method for producing an epitaxial wafer according to [1], [2], [3], [4], [5] or [6], comprising forming the gettering epitaxial film under a pressure of 667 Pa to 2666 Pa. [8]: A method for producing an epitaxial wafer according to [1], [2], [3], [4], [5], [6] or [7], comprising setting the thickness of the gettering epitaxial film to 0.025 μm to 3 μm. [9]: A method for producing an epitaxial wafer according to [1], [2], [3], [4], [5], [6], [7] or [8], comprising setting the thickness of the gettering epitaxial film to 0.025 μm to 1 μm.

[10] : A method for producing the epitaxial wafer according to [1], [2], [3], [4], [5], [6], [7], [8] or [9], comprising forming the gettering epitaxial film at a temperature of 700°C to 800°C.

[11] : The silicon source of the mixed gas atmosphere containing silicon and carbon is SiH 4 , SiH 2 Cl 2 , SiHCl 3 , Si 2 H 6 or SiCl 4 A method for producing an epitaxial wafer according to any one of claims 1 to 10, comprising using a method for producing an epitaxial wafer comprising the steps of:

[12] : As a carbon source for the mixed gas atmosphere containing silicon and carbon, SiH(CH 3 ) 3 , C.H.3 SiH 3 or C 3 H 8 A method for producing an epitaxial wafer according to any one of claims 1 to 11, comprising using a method for producing an epitaxial wafer comprising the steps of:

[0060] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention.

Claims

1. When a gettering epitaxial film made of silicon gas-doped with carbon is formed on a silicon substrate in a mixed gas atmosphere containing silicon and carbon by using a low pressure CVD apparatus, A method for producing an epitaxial wafer, characterized in that the growth rate of the gettering epitaxial film is 2.4 nm / sec or less.

2. 2. The method for producing an epitaxial wafer according to claim 1, wherein the growth rate of the gettering epitaxial film is set to 0.1 nm / sec or more.

3. 2. The method for producing an epitaxial wafer according to claim 1, wherein the growth rate of the gettering epitaxial film is set to 1.2 nm / sec or more.

4. The carbon atom concentration of the gettering epitaxial film is set to 1.0×10 ２０ atoms / cm ３ ~3.0 x 10 ２１ atoms / cm ３ 2. The method for producing an epitaxial wafer according to claim 1, wherein the range is

5. The carbon atom concentration of the gettering epitaxial film is set to 3.0×10 ２０ atoms / cm ３ ~1.0 x 10 ２１ atoms / cm ３ 2. The method for producing an epitaxial wafer according to claim 1, wherein the range is

6. 2. The method for producing an epitaxial wafer according to claim 1, wherein the gettering epitaxial film is formed under a pressure of 667 Pa to 10,666 Pa.

7. 2. The method for producing an epitaxial wafer according to claim 1, wherein the gettering epitaxial film is formed under a pressure of 667 Pa to 2666 Pa.

8. 2. The method for producing an epitaxial wafer according to claim 1, wherein the gettering epitaxial film has a thickness of 0.025 μm to 3 μm.

9. 2. The method for producing an epitaxial wafer according to claim 1, wherein the gettering epitaxial film has a thickness of 0.025 μm to 1 μm.

10. 2. The method for producing an epitaxial wafer according to claim 1, wherein the gettering epitaxial film is formed at a temperature of 700° C. to 800° C.

11. The silicon source of the mixed gas atmosphere containing silicon and carbon is SiH ４ , SiH ２ C ２ , SiHCl ３ , Si ２ H ６ or SiCl ４ 2. The method for producing an epitaxial wafer according to claim 1, further comprising the steps of:

12. As a carbon source for the mixed gas atmosphere containing silicon and carbon, SiH(CH ３ ) ３ , C.H. ３ SiH ３ Or C ３ H ８ The method for producing an epitaxial wafer according to any one of claims 1 to 11, further comprising the step of:

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