A Gated Field Emission Triode Using Silicon Needles Fabricated by Highly Selective Anisotropic Dry Etching

Abstract

We demonstrated a gated field emission triode using silicon needles which were fabricated by highly selective anisotropic dry etching. The etching mask was oxygen precipitation in the silicon substrate. In order to fabricate the triode using the silicon needles, the top level of a gate electrode was located at the same level as the tips of the silicon needles. As a result of the evaluation, it was found that anode current per tip 1 nA/tip at a gate voltage of 33 V was obtained even at a low pressure of 2×10-3 Torr and that it was almost proportional to the number of tips. Thus, most of the tips are expected to contribute to emission current, in spite of a fluctuation in height of the silicon needle. Emission efficiency, which was defined as the ratio of the anode current to total emission current, decreased from 96% to 76% with increasing gate voltage. Furthermore, from a Fowler–Nordheim plot, it followed that electric field was remarkably enhanced around the tips. The field enhancement factor β for the anode current was estimated to be about 2.4×106 cm-1.