High aspect ratio dry etching for microchannel plates

Abstract

Dry etching of GaAs and fused silica for the production of microchannel plates is investigated. Etch methods used are magnetron reactive ion etching, chemically assisted ion beam etching (CAIBE), and electron cyclotron resonance etching (ECR). Extensive characterization of the ECR etcher is carried out with a designed experiment, which uses statistical methods to minimize the number of characterization runs. CAIBE gives high aspect ratio etching of GaAs, but at low etch rates. ECR provides higher etch rates of GaAs and better substrate temperature control. The effect of temperature on sidewall roughness and undercut is examined for temperatures as low as −100 °C. Features with an aspect ratio greater than 30 are presented. Etching of fused silica is difficult due to low etch rates (<0.2 μm/min), and faceting of the metal mask.