Characterization and application of a low-profile metal endash semiconductor endash metal detector for low energy backscattered electrons

A metal endash semiconductor endash metal (MSM) detector for low energy backscattered electrons has been developed and tested. The effects of detector symmetry, finger spacing, and detection area on signal to dark current ratio were studied in order to determine an optimized detector geometry. The detector assembly consisting of Ni-GaAs MSM structures with low dark 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 applications. With this experimental setup, backscattered electron images of alignment 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 commercial Everhart endash Thornley detector. It is demonstrated that MSM detectors can be used as backscattered electron detectors in microcolumns. copyright 1996 American Vacuum Society