Characterization of wafer-level XeF2 Gas-phase Isotropic Etching For MEMS Processing

摘要

This paper reports the characteristics of wafer-level XeF2 gas-phase etching. Compared with chip-level XeF2 etching, the silicon etch rate for wafer-level XeF2 process is much smaller, which is mainly caused by the large exposed silicon area in wafer-level process. Additionally, the silicon etch rate drops off as etching time increased. The aperture size effect is apparent in wafer-level XeF2 processing. However, for etching window with large size, the aperture size effect will be minimized. The vertical aperture size effect is direct proportion to the number of etch cycle, while the lateral aperture size effect is first increase then decrease with the number of etch cycle increasing. Slight anisotropy of wafer-level XeF2 etching is also observed. Based on the characteristics of XeF2 etching, layout design rule for MEMS device with XeF2 releasing is developed and demonstrated.