# US 5,705,423 A · Epitaxial wafer

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- Number: US 5,705,423 A
- Document ID: US5705423A
- Status: Granted
- Kind: A
- Application number: 08/557,947
- Filed: 1995-11-14
- Granted: 1998-01-06
- Earliest claimed: 1994-11-14
- Assignees: Shin-Etsu Handotai Co., Ltd.
- Inventors: Atsuto Sakata; Hisashi Masumura; Hideo Kudo
- Web page: https://patentgrep.com/patent/US5705423A

## CPC

- C30B 25/02: Epitaxial-layer growth
- C30B 25/18: characterised by the substrate
- Y10S 438/974: Substrate surface preparation
- 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
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

An improved and highly productive method is proposed for the preparation of an epitaxial wafer (EPW) consisting of a single crystal silicon wafer as the substrate having a mirror-polished surface and an epitaxial layer of silicon formed on the mirror-polished surface of the substrate by the method of vapor-phase growing. Different from conventional methods in which the mirror-polishing of the substrate surface is conducted in several steps including, usually, the primary, secondary and finish polishing steps taking a great deal of labor and time, it has been unexpectedly discovered that an EPW having excellent properties not inferior to those conventional EPWs can be obtained by conducting the mirror-polishing with the primary polishing only omitting the subsequent steps provided that the thus mirror-polished surface of the substrate has a surface roughness RMS in the range from 0.3 to 1.2 mm.

## Claims

### Claim 1

An epitaxial wafer which comprises:
(a) a substrate of a single crystal silicon wafer; and
(b) an epitaxial layer of silicon formed by the vapor phase growing method on one of the flat surfaces of the substrate, the surface of the substrate on which the epitaxial layer of silicon is formed having a surface roughness RMS in the range from 0.3 nm to 1.2 nm before formation of the epitaxial layer.

### Claim 2 (depends on 1)

The epitaxial wafer as claimed in claim 1 in which the epitaxial layer of silicon formed on one of the flat surfaces of the substrate has a thickness of at least 1 .mu.m.