Prevention method of a notching caused by surface charging in silicon reactive ion etching

This paper proposes a method to prevent silicon from a notching in a reactive ion etching (RIE) process by introducing a self-aligned metal interlayer to a silicon/glass bonded fixture. A metal interlayer prevents a charge buildup at the bottom of a silicon trench, therefore silicon structures do not suffer from charge-induced local damage. A self-aligning process of Ti/Au interlayer is accomplished by a lift-off process using a photoresist etch mask as a sacrificial layer. Titanium is a diffusion barrier of gold to silicon and gold is preferred due to its chemical stability in a pre-cleaning step. The effectiveness of the proposed method is verified by applying it to the fabrication of a simple trench and comb electrode. The applicability of the proposed methodology is examined by fabricating an optical knife edge device.