# US 4,397,897 A · Bell of translucent fused silica for the precipitation of polysilicon

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- Number: US 4,397,897 A
- Document ID: US4397897A
- Status: Granted
- Kind: A
- Application number: 06/331,938
- Filed: 1981-12-17
- Granted: 1983-08-09
- Earliest claimed: 1981-02-27
- Assignees: Heraeus Quarzschmelze GmbH
- Inventors: Karl A. Schulke
- Web page: https://patentgrep.com/patent/US4397897A

## 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
- C03B 20/00: Processes specially adapted for the production of quartz or fused silica articles {, not otherwise provided for (C03B19/01, C03B19/066, C03B19/106, C03B19/12, C03B19/14, C03B37/00 take precedence)}
- C23C 16/4404: {Coatings or surface treatment on the inside of the reaction chamber or on parts thereof}
- C23C 16/4418: {Methods for making free-standing articles (C23C16/01 takes precedence)}
- Y10T 428/1317: Multilayer [continuous layer]
- Y10T 428/24479: including variation in thickness
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C03B: MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
- 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)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Bell of translucent fused silica having an inner layer of transparent fused silica for the precipitation of polysilicon. The thickness of the transparent fused silica layer increases continuously towards the open end of the bell while the total wall thickness of the bell is kept constant. The thickness increase of the transparent fused silica layer begins preferably beyond the center of the total length of the bell. The thickness of the transparent fused silica layer increases by at least half of the thickness which it has in the top part of the bell.

## Claims

### Claim 1

In a bell of translucent fused silica having an inner layer of transparent fused silica for the precipitation of polysilicon, the improvement wherein the thickness of the transparent fused silica layer increases continuously by at least half of its thickness in a area where the total wall thickness of the bell remains constant, towards the open end of the bell.

### Claim 2 (depends on 1)

A bell according to claim 1, wherein the thickness of the transparent silica layer increases continuously by at least 2 mm towards the open end of the bell.

### Claim 3 (depends on 1)

A bell of claim 1, wherein the increase in the thickness of the transparent fused silica layer begins after the center of the overall length of the bell.

### Claim 4 (depends on 1)

A bell of claim 1, wherein the increase in the thickness of the transparent fused silica layer begins after 2/3 of the overall length of the bell from the top of the bell.

### Claim 5 (depends on 1)

A bell according to claim 1, wherein at the open end, the thickness of the transparent fused silica layer accounts for the total wall thickness of the bell.