CHARACTERIZATION AND APPLICATION OF A LOW-PROFILE METAL-SEMICONDUCTOR-METAL DETECTOR FOR LOW-ENERGY BACKSCATTERED ELECTRONS

A metal-semiconductor-metal (MSM) detector for low energy backscattere d electrons has been developed and tested. The effects of detector sym metry, Linger spacing; and detection area on signal to dark current ra tio were studied in order to determine an optimized detector geometry. The detector assembly consisting of Ni-GaAs MSM structures with low d ark current densities was mounted in a scanning electron microscope on a special sample holder which enabled the test of the detector under conditions which can be expected in electron beam microcolumn applicat ions. With this experimental setup, backscattered electron images of a lignment marks of 50-nm-thick Au on a Si substrate were obtained. The signal to noise performance of the device has been compared to a comme rcial Everhart-Thornley detector. It is demonstrated that MSM detector s can be used as backscattered electron detectors in microcolumns. (C) 1996 American Vacuum Society.