# US 11,440,804 B2 · Process for producing polycrystalline silicon mass

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- Number: US 11,440,804 B2
- Document ID: US11440804B2
- Status: Granted
- Kind: B2
- Application number: 16/050,767
- Filed: 2018-07-31
- Published: 2018-11-29
- Granted: 2022-09-13
- Earliest claimed: 2009-09-16
- Assignees: Shin-Etsu Chemical Co., Ltd.
- Applicants: Shin-Etsu Chemical Co., Ltd.
- Inventors: Shigeyoshi Netsu; Junichi Okada; Fumitaka Kume
- Web page: https://patentgrep.com/patent/US11440804B2

## 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 33/037: Purification (by zone-melting C30B13/00)
- C30B 23/00: Single-crystal growth by condensing evaporated or sublimed materials
- C30B 29/06: Silicon
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR

## Abstract

A clean and high-purity polycrystalline silicon mass having a small content of chromium, iron, nickel, copper, and cobalt in total, which are heavy metal impurities that reduce the quality of single-crystal silicon, can be obtained from a silicon rod by before crushing a polycrystalline silicon rod, removing at least 70 mm of a polycrystalline silicon portion from the electrode side end of the polycrystalline silicon rod extracted to the outside of a reactor is provided. Thereby, the polycrystalline silicon portion in which the total of the chromium, iron, nickel, copper, and cobalt concentrations in a bulk is not less than 150 ppta can be removed.

## Claims

### Claim 1

A process for producing a polycrystalline silicon mass, the process comprising:
vapor depositing silicon on a core wire to obtain a polycrystalline silicon rod, one end of the core wire being connected to a first electrode and the other end thereof being connected to a second electrode;
extracting the polycrystalline silicon rod to an outside of a reactor;
removing at least 70 mm of a polycrystalline silicon portion from an electrode side end of the polycrystalline silicon rod extracted to the outside of the reactor;
crushing the polycrystalline silicon rod into polycrystalline silicon mass, and
washing the polycrystalline silicon mass,
wherein said washing comprises:
prewashing, etching, oxidation treating with an aqueous solution of ozone to coat a surface of the polycrystalline silicon mass with a silicon oxide film, and drying.

### Claim 2 (depends on 1)

The process of claim 1, wherein at least 155 mm of the polycrystalline silicon portion from the electrode side end is removed.

### Claim 3 (depends on 1)

The process of claim 1, wherein the extracting comprises covering a surface of the polycrystalline silicon rod with a bag member.

### Claim 4 (depends on 3)

The process of claim 3, wherein an opening of the bag member that covers the surface of the polycrystalline silicon rod is sealed after the polycrystalline silicon rod is extracted to the outside of the reactor.

### Claim 5 (depends on 3)

The process of claim 3, wherein the bag member is a polyethylene bag.

### Claim 6 (depends on 1)

The process of claim 1, wherein the prewashing is performed in water.

### Claim 7 (depends on 1)

The process of claim 1, wherein the etching is performed in a mixed solution comprising hydrofluoric acid, hydrogen peroxide, and water.

### Claim 8 (depends on 7)

The process of claim 7, wherein the hydrofluoric acid is hydrogen fluoride.

### Claim 9 (depends on 1)

The process of claim 1, wherein the etching is performed in a mixed solution comprising hydrofluoric acid and nitric acid.

### Claim 10 (depends on 9)

The process of claim 9, wherein the etching removes at least 20 μm from a surface of the polycrystalline silicon mass.

### Claim 11 (depends on 1)

The process of claim 1, wherein the drying is performed in air or in a vacuum.