Etching of Si with Cl2 using an electron cyclotron resonance source

Abstract

A Cl2 plasma generated by a multipolar electron cyclotron resonance (ECR) source was used to etch Si. Etch rate of Si was found to increase with microwave power and rf power, but decrease with source distance and Ar addition. Etch rate increases with pressure up to 1 mTorr, then decreases at higher pressure. Temperature ranging from − 130 to 100 °C has no significant influence on the etch rate, profile, and morphology. Vertical profile and smooth morphology in Si can be obtained by using low microwave power and low pressure. With a Cl2 plasma at 1 mTorr, 50 W microwave power, 70 W rf power, and 15 cm below the ECR source, 0.15-μm-wide features in Si were etched with 7:1 aspect ratio. Schottky diodes were fabricated on the etched surface to evaluate etch-induced damage. Breakdown voltage was found to increase with microwave power but decrease with rf power and source distance. Ideality factor and barrier height degrade at high rf power and long source distance. One of the most important factors to maintain high quality diode characteristics is by using low self-induced dc bias voltage. In a system with an ECR source and a rf-powered electrode, it has the advantage of generating high density ions at low ion energy, therefore providing high etch rate with minimal surface damage.