Title :
Isotropic Silicon Etching With
Gas for Wafer-Level Micromachining Applications
Author :
Xu, Dehui ; Xiong, Bin ; Wu, Guoqiang ; Wang, Yuchen ; Sun, Xiao ; Wang, Yuelin
Author_Institution :
Sci. & Technol. on Microsyst. Lab., Shanghai Inst. of Microsyst. & Inf. Technol., Shanghai, China
Abstract :
Wafer-level isotropic etching of silicon with XeF2 gas has been investigated for microelectromechanical-system (MEMS) fabrication. Because of the large exposed silicon area in the wafer-level process, XeF2 gas diffusion in the wafer-level process is different from the chip-level process. The silicon etch rate for the wafer-level XeF2 process is much smaller than chip-level XeF2 etching. Additionally, the silicon etch rate drops off as the etching time increased. The aperture size effect is apparent in the wafer-level XeF2 processing. However, for etching windows with a large size, the aperture size effect will be minimized. Both vertical and lateral aperture size effects depend on the number of etch cycle. Although slight anisotropy is also observed, wafer-level XeF2 etching shows a better isotropy than the chip-level process. Compared with the chip-level process, wafer-level XeF2 etching shows a large etch rate for SiO2. The etch selectivity between silicon and SiO2 is lower than 1000:1. Based on the characteristics of XeF2 etching, the layout design rule for the MEMS device with XeF2 releasing is developed and demonstrated.
Keywords :
etching; micromachining; micromechanical devices; silicon compounds; xenon compounds; MEMS device; MEMS fabrication; SiO2; XeF2 gas; XeF2 releasing; XeF2; chip-level XeF2 etching; chip-level process; etch cycle; etch selectivity; etching time; etching windows; gas diffusion; isotropic silicon etching; large exposed silicon area; lateral aperture size effects; layout design rule; microelectromechanical-system fabrication; silicon etch rate; slight anisotropy; vertical aperture size effects; wafer-level XeF2 etching; wafer-level XeF2 processing; wafer-level isotropic etching; wafer-level micromachining applications; wafer-level process; Apertures; Chemicals; Etching; Mathematical model; Micromachining; Micromechanical devices; Silicon; $hbox{XeF}_{2}$ gas; Design rule; isotropic etching; microelectromechanical systems (MEMS); micromachining; wafer level;
Journal_Title :
Microelectromechanical Systems, Journal of
DOI :
10.1109/JMEMS.2012.2209403