Method and apparatus for measuring linewidths by surface profiles.

摘要

A system for determining surface profiles of specimens such as semiconductor wafers and for making linewidth measurements thereon includes a drive (46) for mounting the wafer (w) for oscillatory movement along a line and an optical imaging system (20, 26, 28) overlying the wafer for focusing a beam on a small spot on the wafer and including a photodetector (42) for detecting the reflected spot from the wafer. The spot is scanned along the line on the wafer while the focal depth of the imaging system is progressively changed while the photodetector and connected digital circuitry generate a plurality of spaced output signals for each scan along the line so that data comprised of a series of spaced signals are provided at a plurality of focus levels extending through the surface profile of the wafer. Computer means (22) are provided for analyzing the data and providing a graphical output (24a, 24b) of the surface profile from which accurate linewidth measurements are made. Such computer means also provides an adjustment factor for measuring a linewidth in the same area while making a scan only at a single focus level so that the remainder of the area can be scanned rapidly.