Optical measurements of fine line parameters in integrated circuit processes

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:

• 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.

A method for optically monitoring the image transfer process for an LSI device by:

• 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.