Alignment insensitive anisotropic etching of silicon cavities with smooth 49° sidewalls

Anisotropic etchants like TMAH are used to etch cavities with smooth sidewalls in silicon wafers for MEMS applications. However, complicated crystalline alignment steps are usually needed as crystalline misalignment will enlarge and rotate the etched cavities in an unpredictable way. In this paper, we presented a simple process to avoid unexpected cavity distortion caused by minor crystalline misalignment in TMAH etch. Besides, this process also offers smooth and less inclined sidewalls with a non-standard angle of 49deg on {100} wafers.