# US 8,542,354 B2 · Inspection apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,542,354 B2 - Document ID: US8542354B2 - Status: Granted - Kind: B2 - Application number: 12/361,954 - Filed: 2009-01-29 - Published: 2009-08-13 - Granted: 2013-09-24 - Earliest claimed: 2008-01-31 - Assignees: Hitachi High-Technologies Corporation - Applicants: Masaaki Ito; Minori Noguchi; Shigeru Matsui - Inventors: Masaaki Ito; Minori Noguchi; Shigeru Matsui - Web page: https://patentgrep.com/patent/US8542354B2 ## CPC - G01N 21/9501: {Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)} - G01N 21/95623: {using a spatial filtering method (per se G02B)} - G01N 2021/8822: {Dark field detection} - G06V 10/88: Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters - 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) - G06V: IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING ## Abstract The present invention provides an inspection apparatus having a high throughput and high sensitivity with respect to a number of various manufacturing processes and defects of interest in inspection of a specimen such as a semiconductor wafer on which a pattern is formed. The apparatus illuminates with light the specimen having the pattern formed thereon, forms an image of the specimen on an image sensor through a reflective optics, and determines the existence/nonexistence of a defect. The reflective optics has a conjugate pair of Fourier transform optics. An aberration of the reflective optics is corrected off-axis. The reflective optics has a field of view in non-straight-line slit form on the specimen surface. Also, the optics is of a reflection type, includes a conjugate pair of Fourier transform optics and has a field of view in non-straight-line slit form. An optimum wavelength band is selected according to the specimen (FIG. 1). ## Claims ### Claim 1 An inspection apparatus which determines an existence and a non-existence of a defect, the apparatus comprising: an illumination system which illuminates a specimen with light; and a Fourier transform system comprising: a first Fourier transform unit which includes first reflective elements; a second Fourier transform unit which includes second reflective elements; and an image sensor which acquires an image by using reflected light from the second reflective elements, wherein: the first Fourier transform unit and the second Fourier transform unit are conjugate, the first Fourier transform unit includes an objective element which reflects light from the specimen, an aberration of the Fourier transform system is corrected off-axis, and a field of view of the Fourier transform system on a surface of the specimen is in non-straight-line slit form. ### Claim 2 (depends on 1) The inspection apparatus according to claim 1, further comprising a spatial filter on a Fourier transform plane between the first Fourier transform unit and the second Fourier transform unit. ### Claim 3 (depends on 2) The inspection apparatus according to claim 2, wherein diffracted light from the pattern of the specimen is blocked by the spatial filter. ### Claim 4 (depends on 2) The inspection apparatus according to claim 2, wherein part of scattered light from the specimen is blocked by the spatial filter. ### Claim 5 (depends on 1) The inspection apparatus according to claim 1, further comprising a polarization filter on a Fourier transform plane between the first Fourier transform unit and the second Fourier transform unit. ### Claim 6 (depends on 1) The inspection apparatus according to claim 1, wherein the field of view on the specimen surface is in circular-arc slit form. ### Claim 7 (depends on 1) The inspection apparatus according to claim 1, wherein the optical axis of the Fourier transform system is inclined with respect to the direction of a normal to the specimen surface, and the field of view on the specimen surface is in slit form corresponding to a portion of an ellipse. ### Claim 8 (depends on 1) The inspection apparatus according to claim 1, further comprising a stage for scanning the specimen along a shorter-side direction of the field of view in slit form on the specimen surface. ### Claim 9 (depends on 8) The inspection apparatus according to claim 8, further comprising a laser interferometer, wherein an error in scanning of the stage is measured by the laser interferometer and misalignment of an image of the specimen is corrected. ### Claim 10 (depends on 1) The inspection apparatus according to claim 1, wherein light in a predetermined single wavelength band is selected in a range from a visible light region to a vacuum ultraviolet region according to the specimen to illuminate the specimen. ### Claim 11 (depends on 1) The inspection apparatus according to claim 1, wherein light in a plurality of predetermined wavelength bands are selected in a range from a visible light region to a vacuum ultraviolet region according to the specimen to illuminate the specimen. ### Claim 12 (depends on 11) The inspection apparatus according to claim 11, wherein light in the plurality of wavelength bands is imaged on a single image sensor. ### Claim 13 (depends on 11) The inspection apparatus according to claim 11, wherein light in the plurality of wavelength bands is imaged on a plurality of the image sensors. ### Claim 14 (depends on 10) The inspection apparatus according to claim 10, wherein light in the predetermined wavelength band is selected from a single light source to illuminate the specimen. ### Claim 15 (depends on 10) The inspection apparatus according to claim 10, wherein light in the predetermined wavelength band is selected from a plurality of light sources to illuminate the specimen. ### Claim 16 (depends on 1) The inspection apparatus according to claim 1, wherein the specimen is illuminated with light in an extreme ultraviolet region. ### Claim 17 (depends on 1) The inspection apparatus according to claim 1, wherein a layer region below the pattern of the specimen is substantially opaque to light with which the specimen is illuminated. ### Claim 18 (depends on 1) The inspection apparatus according to claim 1, wherein an image of an inspection region and an image of a region adjacent or close to the inspection region are compared with each other to determine the existence/nonexistence of the defect. ### Claim 19 (depends on 1) The inspection apparatus according to claim 1, further comprising: an image processing system, wherein an image of an inspection region and an image obtained by simulation from data on the configuration of the pattern of the specimen are compared with each other to determine the existence/nonexistence of a defect by the image processing system. ### Claim 20 (depends on 1) The inspection apparatus according to claim 1, wherein the image sensor is a time-delay-integration-type image sensor. ### Claim 21 (depends on 20) The inspection apparatus according to claim 20, wherein an output array from the time-delay-integration-type image sensor and positions in the field of view of the reflective optics are associated with each other. ### Claim 22 (depends on 1) The inspection apparatus according to claim 1, further comprising an aspherical mirror with which an aberration of the Fourier transform system is corrected off-axis. ### Claim 23 (depends on 11) The inspection apparatus according to claim 11, wherein light in the predetermined wavelength bands is selected from a single light source to illuminate the specimen. ### Claim 24 (depends on 12) The inspection apparatus according to claim 12, wherein light in the predetermined wavelength bands is selected from a single light source to illuminate the specimen. ### Claim 25 (depends on 13) The inspection apparatus according to claim 13, wherein light in the predetermined wavelength bands is selected from a single light source to illuminate the specimen. ### Claim 26 (depends on 11) The inspection apparatus according to claim 11, wherein light in the predetermined wavelength bands is selected from a plurality of light sources to illuminate the specimen. ### Claim 27 (depends on 12) The inspection apparatus according to claim 12, wherein light in the predetermined wavelength bands is selected from a plurality of light sources to illuminate the specimen. ### Claim 28 (depends on 13) The inspection apparatus according to claim 13, wherein light in the predetermined wavelength bands is selected from a plurality of light sources to illuminate the specimen. ### Claim 29 (depends on 1) The inspection apparatus according to claim 1, wherein the illumination system is a multiple wavelength illumination system and changes wavelengths as function of a condition of the specimen. ### Claim 30 (depends on 1) The inspection apparatus according to claim 1, wherein said sensor includes: a plurality of pixels, and the pixels of the sensor correspond to positions in field of view of the Fourier transform system in one-to-one correspondence. ### Claim 31 (depends on 1) The inspection apparatus according to claim 1, further comprising: a diffraction element arranged at an output side of the Fourier transform system; and a plurality of sensors which detect a light diffracted by the diffraction element. ### Claim 32 (depends on 1) The inspection apparatus according to claim 1, wherein the Fourier transform system comprises a plurality of mirrors, and an arrangement of the mirrors is rotation symmetric relative to a normal of the specimen.