Silicon photodiodes for low-voltage electron detection in scanning electron microscopy and electron beam lithography

Silicon photodiode (SPD) detectors can be used for secondary electron detection in miniature electron beam columns, where small apertures, tight lens spacings, and short working distances make traditional detectors impractical. Monte Carlo simulations presented in this article suggest that in these configurations, SPDs have an advantage over traditional secondary electron detectors due to their potentially higher collection efficiency. Responsivity results presented here for SPDs with 40 and 60 Å passivation layers show measurable responsivity for electron energies down to 80 eV . High contrast images obtained using a SPD mounted with the Novelx miniature electron beam column and biased with a floating voltage to accelerate low-energy electrons demonstrate the effectiveness of SPDs for secondary electron detection. Based on these simulations and results, it is believed that SPDs present a reliable, inexpensive solution for secondary electron detection in miniature electron beam columns, as well as a robust mechanism for system calibration in column arrays for lithography.