Fabrication of MEMS structure with nano-gap using photo-assisted electrochemical etching

In this paper, MEMS comb structures with several tens of nanometer gap and ultra high aspect ratio more than 125:1 has been achieved using modified photo-assisted electro-chemical etching method. It is possible to control the gap of the comb structure from 50 nm to 1 /spl mu/m by adjusting the intensity of the light source, which is unusually blue LED (light emitting diodes) in this experiment. By changing the bias and the composition of electrolyte that consists of H/sub 2/O or DMF (dimethyl-formamide) based 5% HF (hydrofluoric acid) and 20% ethanol as a wetting agent, the characteristics of the etching were observed. Finally MEMS comb structure with uniform 200 nm gap and 25 /spl mu/m depth was well defined.