# US 11,306,001 B2 · Polycrystalline silicon rod and method for producing same

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- Number: US 11,306,001 B2
- Document ID: US11306001B2
- Status: Granted
- Kind: B2
- Application number: 16/310,532
- Filed: 2017-06-21
- Published: 2019-08-15
- Granted: 2022-04-19
- Earliest claimed: 2016-06-23
- Assignees: Mitsubishi Materials Corporation
- Applicants: Mitsubishi Materials Corporation
- Inventors: Kazuyuki Ito
- Web page: https://patentgrep.com/patent/US11306001B2

## CPC

- C01B 33/035: by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process
- C01B 33/02: Silicon (forming single crystals or homogeneous polycrystalline material with defined structure C30B)
- C23C 16/24: Deposition of silicon only
- C23C 16/46: characterised by the method used for heating the substrate (C23C16/48, C23C16/50 take precedence)
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)

## Abstract

The present invention provides a polycrystalline silicon rod whose rod surface portion has a phosphorus concentration of 0.015 ppba or less, in which the ratio (P2/P1) of the phosphorus concentration (P2) of the rod center portion to the phosphorus concentration (P1) of the rod surface portion is within the range of 2 or lower. The present invention also provides a method for producing a polycrystalline silicon rod by the Siemens method that assembles a polycrystalline silicon seed rod in a reactor, then heats the seed rod up to a temperature of 1000° C. or more and less than the melting point of silicon by energization heating, and supplies a raw material gas including trichlorosilane gas and hydrogen gas as the main components to the reactor at the heating temperature to deposit and grow silicon on the seed rod surface.

## Claims

### Claim 1

A polycrystalline silicon rod whose rod surface portion has a phosphorus concentration of 0.015 ppba or less, wherein a ratio (P2/P1) of a phosphorus concentration (P2) of a rod center portion to a phosphorus concentration (P1) of the rod surface portion is within the range of 1 to 2, wherein the rod center portion is a region of up to 20 mm in diameter centering around a seed rod including the seed rod of the polycrystalline silicon rod, and the rod surface portion is a region extending 5 to 10 mm from the surface of the polycrystalline silicon rod toward the rod center portion.

### Claim 2 (depends on 1)

A method for producing a polycrystalline silicon chunk by crushing the polycrystalline silicon rod according to claim 1.

### Claim 3

A method for producing a polycrystalline silicon rod by the Siemens method comprising:
assembling a polycrystalline silicon seed rod in a silicon deposition reactor,
heating the seed rod up to a temperature of 1000° C. or more and less than the melting point of silicon by energization heating, and
supplying a raw material gas including trichlorosilane gas and hydrogen gas as the main components to the reactor at the heating temperature to deposit and grow silicon on the seed rod surface, wherein
the seed rod is heated up to a temperature of 1000° C. or more and less than the melting point of silicon, and then a mixed gas of silicon tetrachloride gas and hydrogen gas is supplied to the reactor for at least 10 min with the reactor wall temperature maintained at 30° C. or more and the pressure in the reactor maintained at 0.1 MPaG or less to etch the surface of the seed rod in the reactor, and subsequently a raw material gas including trichlorosilane gas and hydrogen gas as the main components is subsequently supplied at the heating temperature.

### Claim 4 (depends on 3)

The method for producing a polycrystalline silicon rod according to claim 3, wherein the produced polycrystalline silicon rod has a bulk metal impurity of iron (Fe) concentration of 0.04 ppbw or less, a bulk metal impurity of nickel (Ni) concentration of 0.007 ppbw or less, and a bulk metal impurity of chromium (Cr) concentration of 0.005 ppbw or less.

### Claim 5 (depends on 3)

The method for producing a polycrystalline silicon rod according to claim 3, wherein the silicon tetrachloride gas supplied to the reactor is a silicon tetrachloride gas purified by recovering a gas containing silicon tetrachloride discharged from the reactor and separating components except the silicon tetrachloride gas from the gas containing silicon tetrachloride.