Anisotropic vapor HF etching of silicon dioxide for Si microstructure release

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.

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► Enhancement of etch rate between implanted and unimplanted silicon-dioxide is shown.
► Using vapor phase acid a very large selectivity is demonstrated.
► TCAD simulation of implantation and etching with liquid or vapor phase acid is shown.
► Ideal use of implanted silicon-dioxide etched with VHF is demonstrated by simulation.