# US 7,611,989 B2 · Polysilicon dummy wafers and process used therewith

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- Number: US 7,611,989 B2
- Document ID: US7611989B2
- Status: Granted
- Kind: B2
- Application number: 11/959,354
- Filed: 2007-12-18
- Published: 2008-06-26
- Granted: 2009-11-03
- Earliest claimed: 2005-03-03
- Assignees: Integrated Materials, Inc.
- Applicants: Doris Mytton, legal representative
- Inventors: James E. Boyle; Reese Reynolds; Raanan Y. Zehavi; Robert W. Mytton; Tom L. Cadwell
- Web page: https://patentgrep.com/patent/US7611989B2

## CPC

- C30B 33/02: Heat treatment (C30B33/04, C30B33/06 take precedence)
- C30B 15/00: Single-crystal growth by pulling from a melt, e.g. Czochralski method (under a protective fluid C30B27/00)
- C30B 29/06: Silicon
- H10P 72/10: using carriers specially adapted therefor, e.g. front opening unified pods [FOUP]
- Y10T 428/24355: Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
- 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
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Non-production wafers of polycrystalline silicon are placed in non-production slots of a support tower for thermal processing monocrystalline silicon wafers. They may have thicknesses of 0.725 to 2 mm and be roughened on both sides. Nitride may be grown on the non-production wafers to a thickness of over 2 μm without flaking. The polycrystalline silicon is preferably randomly oriented Czochralski polysilicon grown using a randomly oriented seed, for example, CVD grown silicon. Both sides are ground to introduce sub-surface damage and then oxidized and etch cleaned. An all-silicon hot zone of a thermal furnace, for example, depositing a nitride layer, may include a silicon support tower placed within a silicon liner and supporting the polysilicon non-production wafers with silicon injector tube providing processing gas within the liner.

## Claims

### Claim 1

A nitride deposition process having a cycle of deposition, comprising
disposing monocrystalline silicon production wafers on some slots of a support tower,
disposing at least one polycrystalline non-production wafer on other slots of the support tower,
in a furnace in which the support tower is disposed, depositing silicon nitride on the production and non-production wafers by chemical vapor deposition; and
repeating the cycle of deposition with different production wafers and the same non-production wafer;
wherein the repeating step continues until silicon nitride is deposited on the same non-production wafer to a thickness of at least 1 micron.

### Claim 2 (depends on 1)

The process of claim 1, wherein the thickness is at least 2 microns.

### Claim 3 (depends on 1)

The process of claim 1, wherein the tower is a silicon tower.

### Claim 4 (depends on 1)

The process of claim 1, wherein the non-production wafer has a thickness in the range of 0.725 to 2 mm.

### Claim 5 (depends on 1)

The process of claim 1, wherein the non-production wafer has both principal sides roughened.

### Claim 6 (depends on 5)

The process of claim 5, wherein both principal sides have sub-surface damage extending at least 25 μm from the principal sides.

### Claim 7 (depends on 1)

The process of claim 1, wherein the polycrystalline non-production wafer comprises a polysilicon member of polysilicon having a substantially randomly oriented crystallography.

### Claim 8 (depends on 1)

The process of claim 1, wherein the polycrystalline non-production wafer comprises CVD-source CZ polysilicon.

### Claim 9 (depends on 1)

The process of claim 1, wherein a diameter of both the production and non-production wafers is a common diameter chosen from 150, 200, 300, and 450 mm.

### Claim 10

A method of fabricating a non-production wafer, comprising:
cutting a wafer from a polycrystalline silicon ingot;
oxidizing the wafer; and
processing the wafer so that it contains sub-surface damage on both sides thereof at the completion of processing, wherein the sub-surface damage includes cracks and crevices and extends to a depth from both said sides of at least 25 microns.

### Claim 11 (depends on 10)

The method of claim 10, wherein the wafer comprises polysilicon having a substantially randomly oriented crystallography.

### Claim 12 (depends on 10)

The method of claim 10, wherein the wafer comprises CVD-source CZ polysilicon.

### Claim 13 (depends on 10)

The method of claim 10, further comprising pulling the ingot from a silicon melt using a polysilicon seed.

### Claim 14 (depends on 10)

The method of claim 10, further comprising:
growing a silicon rod by chemical vapor deposition; and
cutting the polysilicon seed from the silicon rod.