# US 10,119,801 B2 · Height measurement using optical interference

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- Number: US 10,119,801 B2
- Document ID: US10119801B2
- Status: Granted
- Kind: B2
- Application number: 15/480,735
- Filed: 2017-04-06
- Published: 2017-10-12
- Granted: 2018-11-06
- Earliest claimed: 2016-04-07
- Assignees: International Business Machines Corporation
- Applicants: International Business Machines Corporation
- Inventors: Richard A. Haight; James B. Hannon; Rudolf M. Tromp
- Web page: https://patentgrep.com/patent/US10119801B2

## CPC

- G01B 9/02: Interferometers
- G01B 11/026: {by measuring distance between sensor and object (G01B11/0608 takes precedence)}
- G01B 11/0608: {Height gauges}
- G01B 11/14: for measuring distance or clearance between spaced objects or spaced apertures (G01B11/26 takes precedence; rangefinders G01C3/00)
- G03F 7/70775: {Position control, e.g. interferometers or encoders for determining the stage position}
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

Methods and systems for measuring a distance include measuring a first interference pattern between a lens and a target surface using a light source at a first wavelength. A second interference pattern is measured between the lens and the target surface using a light source at a second wavelength, different from the first wavelength. An absolute measurement of a distance between the lens and the target surface is determined based on the first interference pattern and the second interference pattern.

## Claims

### Claim 1

A method for measuring a distance, comprising:
positioning a spherical lens within a maximum measurement distance from a target surface;
measuring a first interference pattern between a the spherical lens and a the target surface using a light source at a first wavelength by measuring a radius of a smallest ring in the first interference pattern;
measuring a second interference pattern between the spherical lens and the target surface using a light source at a second wavelength, different from the first wavelength, by measuring a radius of a smallest ring in the second interference pattern; and
determining an absolute measurement of a distance between the spherical lens and the target surface using a processor based on the first interference pattern and the second interference pattern.

### Claim 2 (depends on 1)

The method of claim 1, wherein the first and second wavelength are not integer multiples of one another.

### Claim 3 (depends on 1)

The method of claim 1, wherein the first and second interference patterns are in the form of Newton's rings.

### Claim 4 (depends on 1)

The method of claim 1, wherein the light source at the first wavelength and the light source at the second wavelength are both lasers.

### Claim 5 (depends on 1)

A computer readable storage medium comprising a computer readable program for distance measurement, wherein the computer readable program when executed on a computer causes the computer to perform the steps of claim 1.