Authors: W.J. Li, J.C. Shih, J.D. Mai, C-M. Ho, J. Liu and Y-C. Tai
Affilation: UC-Los Angeles, United States
Pages: 59 - 64
Keywords: sacrificial-etching, surfacemicromachining, HF-PSG, MEMS-diaphragm, etchingmodel
Chemical etching of sacrifeial layers is a widely used technique in surface micromachining Etch rate prediction of the sacrif cial layer in an etchant is critical for optimizing a giving fabrication process. This paper presents a moving-boundary numerical scheme to predict the motion of a hydrofluoric (HF) acid and phosphosilicate-glass fPSG) etching interface. Results showed the prediction of the etch front pmpagation for square structures is universally possible for HF concentrations ranging from 3 to 49?/a In the process, some physical mechanisms governing the HFPSG etching phenomenon were elucidated The results also indicate that the moving-boundary scheme can be extended to predict the etch rate of more complex geometries.