As the dimensions of VLSI advanced process development devices increasingly become smaller, the need for an advanced inspection tool for semiconductor manufacturers increases as well. These dimensions, rapidly approaching the sub-micron level, make it difficult to perform accurate inspection and measurement with an optical microscope. The resolution and depth of focus limitations of the optical microscope present problems when attempting to measure or inspect the quality of contact holes. This study discusses the design considerations of a computerized low voltage electron beam. linewidth measuring tool which has been developed by Nanometrics Inc. of Sunnyvale, CA. This system, because of its non-penetrating electrons, permits the inspection and measure ment of contact holes, and alleviates the difficulties encountered with optical microscopes. Because the tool has been optimized to operate at low voltages (< 1KV), minimum charging on non-conducting materials, and the ability to look at the absolute surface of even the thin-nest films, is greatly. improved.