US 9,810,530 B2 · Autofocus system and method

Abstract

Autofocus system (AF) employing, in addition to specified optical units, fringe projection and fringe detection systems (FPS, FDS) and specifically-configured data processing system. AFS is configured to project with FPS a sinusoidal fringe pattern, formed by a pattern source, on a substrate and to image the so projected pattern from substrate onto optical detector with FDS to form optical image from which topology of the substrate is defined as substrate moves relative to the projected pattern. Pattern source may include diffraction grating oriented that the projected pattern is inclined relative to direction of substrate scanning Topology profile is corrected for tilt of substrate, Goos-Hanchen errors, and for fringe-pattern-induced errors outside a chosen spatial-frequency range. To reduce errors of topology profile, at least five values of phase difference are used. AFS is configured to define temporal phase shifting in optical image without using any moving parts in the AFS.

Claims28

Dependent claims

An autofocus system for use with a lithography exposure tool configured to expose a target substrate, said autofocus system comprising:

a fringe projection system configured to project, at respectively corresponding multiple wavelengths, sinusoidal fringe patterns from a diffraction grating disposed inside the fringe projection system through a first optical element onto a surface of the target substrate, to form target sinusoidal fringe patterns thereon,
said fringe projection system configured to deliver, to the target substrate, only light in +1 and −1 diffraction orders formed by said diffraction grating from light incident thereon;
a fringe detection system having sensing elements positioned
to acquire optical images of respectively corresponding target sinusoidal fringe patterns through a second optical element and an optical polarization-filtering element, and,
to generate corresponding outputs respectively representing said images,
wherein said optical images are formed at different wavelengths and different polarization states;
a data processing system in operable communication with the sensing element and configured
(i) to generate data based on the output, the data indicative of topology features on the surface of the target substrate as the substrate is moved relative to said target sinusoidal fringe patterns;
(ii) to generate processed data to determine a topology profile of the surface of the target substrate in the vicinity of said target sinusoidal fringe patterns as the substrate is moved relative to the target sinusoidal fringe patterns.

6 more elements

An autofocus system for use with a lithography exposure tool configured to expose a target substrate, said autofocus system comprising:

a fringe projection system configured to project a sinusoidal fringe pattern from a source of said sinusoidal fringe pattern disposed inside the fringe projection system onto a surface of the target substrate to be exposed by the lithography exposure tool, to form a target sinusoidal fringe pattern thereon;
a fringe detection system having a sensing element positioned to acquire an optical image of said target sinusoidal fringe pattern and to generate an output representing said optical image;
a data processing system that is in operable communication with the sensing element and configured to:
(i) generate data based on the output, the data indicative of topology features on the surface of the target substrate in the vicinity of said target sinusoidal fringe pattern as the substrate is moved relative to the target sinusoidal fringe pattern, and
(ii) generate processed data to determine a topology profile of the surface of the target substrate as the substrate is moved relative to the target sinusoidal fringe pattern;
and
a first optical element,
wherein said source includes a diffraction grating, and
wherein the fringe projection system is configured to project, through the first optical element, only +1 and −1 diffraction orders formed by said diffraction grating from light incident thereon.

6 more elements

An autofocus system for use with a lithography exposure tool configured to expose a target substrate, said autofocus system comprising:

a fringe projection system configured to project a sinusoidal fringe pattern from a source of said sinusoidal fringe pattern disposed inside the fringe projection system through a first optical element onto a surface of the target substrate to be exposed by the lithography exposure tool, to form a target sinusoidal fringe pattern thereon;
a fringe detection system haying a sensing element positioned to acquire an optical image of said target sinusoidal fringe pattern, formed at said sensing element through a second optical element, and to generate an output representing said image;
a data processing system in operable communication with the sensing element and configured
to generate data based on the output, the data indicative of topology features on the surface of the target substrate as the substrate is moved relative to said target sinusoidal fringe pattern;
wherein the autofocus system is configured to define temporal phase shifting in said optical image without using any moving parts in said autofocus system,
wherein the source includes a diffraction grating, and
wherein the autofocus system is configured to project, through the first optical element, only +1 and −1 diffraction orders formed by said diffraction grating from light incident thereon.

4 more elements

Dependencies are inferred from the claim text.

Autofocus system and method

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Autofocus system and method

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Abstract

Claims28