APPARATUS FOR INSPECTION OF SEMICONDUCTOR WAFERS AND MASKS USING A LOW ENERGY ELECTRON MICROSCOPE WITH TWO ILLUMINATING BEAMS

摘要

A novel dual beam low energy electron microscope (LEEM) apparatus for inspecting semiconductor circuits or masks. Direct imaging records many pixels in parallel, offering higher inspection rates than prior art scanning methods. A low energy flood beam is superimposed with a second, higher energy flood beam. The use of two beams avoids charging effects upon insulating or partially insulating substrates. Under appropriate conditions, the net charging flux to each image element can be balanced on a pixel by pixel, as well as global basis. Either the low energy or the higher energy beam may be used to form an image of the surface. An electron optical apparatus and configuration for this dual beam LEEM is described.