Anisotropic Vapor HF etching of silicon dioxide for Si microstructure release

TL;DR

This paper investigates anisotropic vapor HF etching of silicon dioxide, showing that ion implantation significantly increases etch rate, enabling precise microstructure release with reduced underetch in MEMS fabrication.

Contribution

It introduces a method to enhance silicon dioxide etch rate via ion implantation, allowing better control and prediction of sacrificial layer patterning in MEMS.

Findings

Etch rate ratio exceeds 150 in vapor HF for implanted vs. unimplanted silicon dioxide

Ion implantation damages increase etch rate, enabling anisotropic etching

Simulation can predict patterning based on experimentally measured etch rates

Abstract

Damages are created in a sacrificial layer of silicon dioxide by ion implantation to enhance the etch rate of silicon-dioxide in liquid and vapor phase hydrofluoric acid. The etch rate ratio between implanted and unimplanted silicon dioxide is more than 150 in vapor hydrofluoric acid (VHF). This feature is of interest to greatly reduce the underetch of microelectromechanical systems anchors. Based on the experimentally extracted etch rate of unimplanted and implanted silicon dioxide, the patterning of the sacrificial layer can be predicted by simulation.