# US 4,391,524 A · Method for determining the quality of light scattering material

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 4,391,524 A
- Document ID: US4391524A
- Status: Granted
- Kind: A
- Application number: 06/244,060
- Filed: 1981-03-16
- Granted: 1983-07-05
- Earliest claimed: 1981-03-16
- Assignees: RCA Corporation
- Inventors: Edgar F. Steigmeier; Heinrich Auderset
- Web page: https://patentgrep.com/patent/US4391524A

## CPC

- G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A method of determining the crystalline quality of heteroepitaxial silicon material, particularly silicon-on-sapphire (SOS) and of homoepitaxial silicon material which uses the light scattering is disclosed. The material is exposed to a beam of light of a selected wavelength, and scattered light having an intensity above a threshold is detected to provide a signal which is used to control the intensity of a display beam of a visual display device. The threshold is varied to thereby vary the display beam intensity so as to provide the minimum intensity of display beam which yields a full display. The value of the thusly adjusted threshold intensity is used as a direct measure of the quality of the material.

## Claims

### Claim 1

The method for determining the quality of a material having a property of absorbing light to a given penetration depth comprising the steps of:
(a) exposing one or more regions of said material to a beam of light of a selected wavelength;
(b) detecting scattered light having an intensity greater than a threshold intensity from the exposed material to provide an electrical signal proportional to the intensity of detected scattered light above said threshold intensity;
(c) applying the electrical signal to a visual display device to control the intensity of a display beam of the device; and
(d) varying said threshold intensity to thereby vary the intensity of the display beam so as to provide the minimum intensity of display beam which yields a full display of the exposed material, wherein the value of the threshold intensity is a direct measure of the crystalline quality of the material.

### Claim 2 (depends on 1)

The method of claim 1, wherein the light exposing step comprises scanning the light beam so as to be incident on a selected surface portion of the material.

### Claim 3 (depends on 1)

The method according to claim 1, wherein the light exposing step comprises exposing the material to a plurality of selected spatially separated beams incident on the suface of the material.

### Claim 4 (depends on 1)

The method according to claim 1, wherein the wavelength of said light is selected from a wavelength within the range of 2,600-5,200 angstroms.

### Claim 5 (depends on 4)

The method according to claim 4, wherein said wavelength of light is 4,416 angstroms.

### Claim 6 (depends on 5)

The method according to claim 5, wherein said wavelength of light is 3,250 angstroms.

### Claim 7 (depends on 1)

The method according to claim 1, wherein said material comprises a layer of silicon on a substrate of sapphire.

### Claim 8 (depends on 1)

The method according to claim 1, wherein said material comprises a wafer of bulk silicon material.

### Claim 9 (depends on 1)

The method according to claim 1, wherein said material comprises a metal layer having an absorption characteristic to allow for a preselected penetration depth of said light.

### Claim 10 (depends on 1)

The method according to claim 1, wherein said material comprises a thin layer of epitaxially grown silicon on a substrate of silicon.

### Claim 11 (depends on 1)

The method according to claim 1, wherein said material comprises a dielectric.

### Claim 12 (depends on 1)

The method according to claim 1, wherein said material comprises amorphous silicon.