Novel prevention method of stiction using silicon anodization for SOI structure

Abstract

Silicon anodization process has been applied to prevent both `after-rinse stiction' and `in-use stiction' for the sensors with SOI structure. The anodization process roughened the silicon surface causing hillocks of a few tens of nanometer in height and a few hundreds of nanometer in diameter, resulting in increment of water contact angle above 100° as expected from a theory of fractal structure. Prevention effect for `after-rinse stiction' was evaluated with silicon cantilever beam array fabricated by SOI structure. The maximum detachment length became three times longer than that of the beam on usual silicon surface. The roughening of silicon surface reduces the actual contact area, and hence, it is effective in preventing `in-use stiction'. The anodization process was also performed using 73% HF solution without causing attack for aluminum metallization.