Optical measurements of fine line parameters in integrated circuit processes
First Claim
1. In a method for optically measuring the line parameters including line width dimensions, line edge profile or line thicknesses of a diffraction pattern of material disposed on a test sample, said diffraction pattern comprised of a planar array of spaced strips of material having a strip width a and periodicity d, including the steps for exposing and diffraction pattern to a beam of monochromatic light to diffract said beam into diffracted beams of various orders, and for detecting and measuring the intensity of at least two of the diffracted beams to obtain at least two intensity signals, wherein the improvement comprises the steps of:
- scanning said light beam over the grating pattern of the test sample,the beam having a diameter substantially greater than the width of the grating strips, andgenerating continuously information signals representing the diffracted order beams as the beam is scanned over the diffraction pattern, deviations of said information signals from a predetermined reference being a measure of the change in line parameters comprising essentially the lateral dimensions of the lines, the thickness of the lines, and the profile of the edge of the lines of the diffraction pattern.
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Accused Products
Abstract
The image transfer process in integrated circuit (IC) processes such as large scale integrated (LSI) device process manufacturing is monitored by optical measurements on a stage-by-stage basis by measuring a monitor specimen or test sample formed with a diffraction grating of a predetermined pattern having a strip width corresponding to the desired line widths of the wafers or masks being monitored. A beam of monochromatic light is scanned over the test sample to generate diffracted beams of various orders. Line width, line depth, line edge profile process errors can be determined by various combinations of the diffracted beams of the zero, first, second, etc., orders. The test sample is scanned to generate a display for data representing the diffracted beams. The parameter data can be stored for later use for quality control, process monitoring, circuit design parameters, and the like. Moreover, gross process errors are visually discernible on the monitor specimen.
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Citations
21 Claims
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1. In a method for optically measuring the line parameters including line width dimensions, line edge profile or line thicknesses of a diffraction pattern of material disposed on a test sample, said diffraction pattern comprised of a planar array of spaced strips of material having a strip width a and periodicity d, including the steps for exposing and diffraction pattern to a beam of monochromatic light to diffract said beam into diffracted beams of various orders, and for detecting and measuring the intensity of at least two of the diffracted beams to obtain at least two intensity signals, wherein the improvement comprises the steps of:
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scanning said light beam over the grating pattern of the test sample, the beam having a diameter substantially greater than the width of the grating strips, and generating continuously information signals representing the diffracted order beams as the beam is scanned over the diffraction pattern, deviations of said information signals from a predetermined reference being a measure of the change in line parameters comprising essentially the lateral dimensions of the lines, the thickness of the lines, and the profile of the edge of the lines of the diffraction pattern. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method for optically monitoring the image transfer process for an LSI device by:
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scanning a test sample comprising a specimen monitor substrate or mask having a large area diffraction pattern thereof with a monochromatic light beam having a diameter that is substantially smaller than the size of said grating pattern, measuring while scanning with said light beam the physical parameter of width, depth and edge profile of the diffraction grating by comparing one or more pairs of a plurality of pairs of diffracted beams of various orders, repeat processing of said test sample in progressive stages of the image transfer process, and repeat said scanning and measuring steps to determine deviations of said parameters from the previous stage.
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13. In an apparatus for optically measuring the line parameters including line width dimensions, line edge profile or layer thicknesses of a diffraction pattern of material disposed on a test sample, said diffraction pattern comprised of a planar array of spaced strips of material having a strip width a and periodicity d, said apparatus including means for exposing said diffraction pattern to a beam of monochromatic light to diffract said beam into diffracted beams of various orders, detector means including detectors for measuring the intensity of at least two of the diffracted beams to obtain at least two intensity signals, wherein the improvement comprises:
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means for scanning said light beam over the grating pattern of the test sample, the beam having a diameter substantially greater than the width of the grating strips, and means for generating continuously information signals representing the diffracted order beams as the beam is scanned over the diffraction pattern, deviations of said information signals from a predetermined reference being a measure of the change in line parameters comprising essentially the lateral dimensions of the lines, the thickness of the lines, and the profile of the edge of the lines of the diffraction pattern. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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21. A method for optically monitoring the image transfer process for an LSI device by:
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preparing by a given process a product wafer or mask with selected patterns extending over a selected area thereon, and preparing by said given process a test sample comprising a specimen monitor mask or wafer having a diffraction pattern extending over an area thereon substantially equal to the pattern area of said product wafer or mask, gross defects in the diffraction pattern of said specimen monitor mask or wafer being visually discernible and being indicative thereby of similar defects at corresponding area portions on said product wafer or mask.
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Specification