US 11,442,025 B1 · Optical sensor for surface inspection and metrology

Abstract

An interferometer and an imager may include a tunable light source, a beam splitter, a digital imager, and a processor system. The tunable light source may be configured to emit a beam. The beam splitter may be configured to direct the beam toward a sample with a floor surface and a raised surface feature. The digital imager may be configured to receive a reflected beam and to generate an image based on the reflected beam. The reflected beam may be a coherent addition of a first reflection of the beam off a reference plate and a second reflection of the beam off the raised surface feature and third reflection of the beam off the floor surface. The processor system may be coupled to the digital imager and may be configured to determine a distance between the reference surface and the feature surface based on the image. A second digital imager may also be configured to receive a reflected beam and scattered beam to generate a two-dimensional grayscale image of the surface based on these beams and may also be configured to receive fluorescent light generated by the incident light to generate a two-dimensional gray scale an image of the surface based on fluorescent emission.

Claims30

Dependent claims

A method, comprising:

emitting a first light beam of a first wavelength at a first time;
directing the first light beam toward a reference plate and a first sample facing the reference plate, the first sample defining a floor surface and a raised surface feature rising above the floor surface;
generating a first image based on a first reflected light beam, the first reflected light beam being a coherent addition of a first reflection of the first light beam off of a surface of the reference plate, a second reflection of the first light beam off of the raised surface feature and a third reflection of the first light beam off of the floor surface;
and
based on the generated first image, determining a distance between the reference plate and the raised surface feature and determining a distance between the surface of the reference plate and the floor surface.

2 more elements

An optical system configured to measure raised surface features on a surface of a sample, comprising:

a first digital imager and a second digital imager;
a processor system coupled to the first and to the second digital imagers;
a tunable light source configured to emit a first light beam and a second light beam;
a first lens system configured to focus incident light onto the sample surface and to focus reflected light back on the first and second digital imagers;
a reference plate disposed above and facing the sample surface;
an off-axis ring illuminator and configured to receive and direct the second light beam toward the reference plate at angles other than normal to the sample surface;
a first beam splitter configured to direct the first light beam through the first lens system toward the reference plate in a direction normal to the sample surface and to transmit a first reflected light beam of the first light beam reflected by the reference plate and a second reflected light beam of the second light beam reflected by a raised surface feature on the sample;
a second beam splitter configured to transmit at least a portion of the first reflected light beam toward the first digital imager and to reflect at least a portion of the second reflected light beam toward the second digital imager;
wherein the first digital imager is configured to generate a first digital image based at least on the first reflected light beam and wherein the second digital imager is configured to generate a second digital image based at least on the second reflected light beam, and
wherein the processor system is configured to determine a distance between the reference plate and the raised surface feature of the sample based at least on the first and second digital images.

7 more elements

Dependencies are inferred from the claim text.

Optical sensor for surface inspection and metrology

Life of this patent

Optical sensor for surface inspection and metrology

Life of this patent

Abstract

Claims30