# US 9,439,275 B2 · System and method for generating extreme ultraviolet light > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,439,275 B2 - Document ID: US9439275B2 - Status: Granted - Kind: B2 - Application number: 14/590,833 - Filed: 2015-01-06 - Published: 2015-05-07 - Granted: 2016-09-06 - Earliest claimed: 2011-11-16 - Assignees: Gigaphoton Inc. - Applicants: Gigaphoton Inc. - Inventors: Masato Moriya; Osamu Wakabayashi - Web page: https://patentgrep.com/patent/US9439275B2 ## CPC - G01J 1/4257: {applied to monitoring the characteristics of a beam, e.g. laser beam, headlamp beam (monitoring arrangements for lasers in general H01S3/0014)} - G01J 1/429: {applied to measurement of ultraviolet light (using counting tubes G01T)} - G01J 1/44: Electric circuits {(for command of an exposure part G03B7/02)} - G03F 7/70258: {Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system} - H05G 2/0086: {Optical arrangements for conveying the laser beam to the plasma generation location} - G01J 1/0429: {using polarisation elements} - G01J 9/00: Measuring optical phase difference (devices or arrangements for controlling the phase of light beams G02F1/01); Determining degree of coherence; Measuring optical wavelength (spectrometry G01J3/00) - G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N) - 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) - H05G: X-RAY TECHNIQUE (investigating or analysing materials by the use of X-rays G01N23/00; apparatus for X-ray photography G03B42/02; X-ray tubes H01J35/00; TV systems having X-ray input H04N5/321) ## Abstract A system for generating extreme ultraviolet light may include a chamber, a target supply device configured to supply a target material into the chamber, a laser apparatus configured to output a laser beam to irradiate the target material, a wavefront adjuster configured to adjust a wavefront of the laser beam, an imaging optical system configured to focus the laser beam reflected by the target material, an image detector configured to capture an image of the laser beam focused by the imaging optical system, and a controller configured to control the wavefront adjuster based on the captured image. ## Claims ### Claim 1 A system for generating extreme ultraviolet light, comprising: a chamber; a target supply device configured to supply a target material to a specific region in the chamber; a first laser apparatus configured to output a first laser beam to irradiate the target material; an optical system configured to focus the first laser beam outputted from the first laser apparatus; a detector configured to detect a backpropagating beam of the first laser beam reflected by the target material; and a controller configured to control a focus position of the optical system based on the backpropagating beam detected by the detector. ### Claim 2 (depends on 1) The system according to claim 1, wherein the optical system includes first and second optical elements, the first optical element is a concave lens, and the controller controls a distance between the first optical element and the second optical element. ### Claim 3 (depends on 1) The system according to claim 1, wherein the optical system includes first and second optical elements, the first optical element is a concave mirror, and the controller controls a distance between the first optical element and the second optical element. ### Claim 4 (depends on 1) The system according to claim 1, wherein the detector includes: an imaging lens configured to focus the backpropagating beam; and an image sensor configured to capture an image of the backpropagating beam focused by the imaging lens, and the controller controls the focus position based on the image captured by the image sensor. ### Claim 5 (depends on 1) The system according to claim 1, wherein the detector includes: a microlens array configured to focus the backpropagating beam; and a wavefront sensor configured to detect a wavefront of the backpropagating beam focused by the imaging lens, and the controller controls the focus position based on the wavefront detected by the wavefront sensor. ### Claim 6 (depends on 1) The system according to claim 1, further comprising: an attenuator configured to attenuate a first laser beam passing therethrough; and a moving mechanism configured to move the attenuator into or out of a beam path of the first laser beam outputted from the first laser apparatus, wherein the controller controls the moving mechanism so that the attenuator is disposed on the beam path when extreme ultraviolet light is not to be generated. ### Claim 7 (depends on 1) The system according to claim 1, further comprising a second laser apparatus configured to output a second laser beam to irradiate the target material having been irradiated with the first laser beam. ### Claim 8 (depends on 7) The system according to claim 7, further comprising a beam combiner configured to conform a beam axis of the first laser beam to a beam axis of the second laser beam. ### Claim 9 (depends on 1) The system according to claim 1, further comprising a beam dump configured to absorb the laser beam having been passed through the specific region. ### Claim 10 (depends on 1) The system according to claim 1, further comprising a profile adjuster configured to convert a profile of the first laser beam into a top-hat profile. ### Claim 11 A method for generating extreme ultraviolet light in a system which includes a chamber, a target supply device configured to supply a target material to a specific region in the chamber, a first laser apparatus configured to output a first laser beam to irradiate the target material, an optical system configured to focus the first laser beam outputted from the first laser apparatus, a detector configured to detect a laser beam reflected by the target material, and a controller configured to control a focus position of the optical system, the method comprising: detecting, by the detector, a backpropagating beam of the first laser beam reflected by the target material; and controlling, by the controller, the focus position of the optical system based on the backpropagating beam detected by the detector.