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6680824 
Book/Book Chapter 
Numerical simulation for the sacrificial release of MEMS square diaphragms 
Li, WJ; Shih, JC; Mai, JD; Chih-Ming, H; Jianqiang, L; Yu-Chong, T 
1998 
1998 International Conference on Modeling and Simulation of Microsystems, Semiconductors, Sensors and Actuators 
59-64 
INSPEC:6495349 
Chemical etching of sacrificial layers is a widely used technique in surface micromachining. Etch rate prediction of the sacrificial layer in an etchant is critical for optimization of a given fabrication process. This paper presents a moving-boundary numerical scheme to predict the motion of a hydrofluoric (HF) acid and phosphosilicate-glass (PSG) etching interface. Results showed that the prediction of the etch front propagation for square structures is universally possible for HF concentrations ranging from 3 to 49% in the process, and that some physical mechanisms governing the HF-PSG 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.