Optical instruments for submicron linewidth measurement are limited by the resolution associated with the wavelength of light. By measuring phase, rather than intensity, the lateral resolution of the system can be improved. This paper describes a system based upon an interferometric optical profiler using a Linnik interferometer and narrow-band illumination. The system measures surface height directly using phase-measurement interferometry techniques. Three-dimensional maps of surface structure over 1024 X 1024 pixels are produced. The system includes an 80486-based AT-compatible computer and a Videk Megaplus camera. The Videk Megaplus camera has 1320 X 1030 active square pixels spaced at 6.8 micrometers intervals. It outputs an 8-bit digital signal which is interfaced to a framegrabber, and intensity is displayed live on a high resolution monitor. The incoherent optical resolution of the system is 0.34 micrometers , and the detector samples the surface every 0.034 micrometers . It has been found that features as small as 0.5 micrometers can easily be measured. Two calibration standards traceable to NIST with feature sizes on the order of 1 micrometers have been used to calibrate the lateral dimensions of the system. Results of measurements of photoresist lines on silicon with 0.5 micrometers lines are presented.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.