Silicon wafer through-holes fabricated by photo-assisted electrochemical etching

[[abstract]]This research developed photo-assisted electrochemical etching (PAECE) system with low-cost light source for fabricating high-density silicon wafer through-holes array. This process is described as followed: high-density through-holes array in silicon is etched by photo-assisted electrochemical etching under various parameters, such as illumination, surfactants, and concentrations, then to improve the through-hole etching fabrication to obtain through-holes array with high etching rate and smooth etching sidewall. The developed technology will be promising for applications of integrated probe array and wafer-level package in the further. Its advantages are described as followed: low-cost system and fabrication, manufacture, high yield, and suitable for semiconductor process. Using PAECE technology to fabricate wafer through-holes array, we can get the structures with high etching rate and smooth etching sidewall through silicon substrate with thickness of 500 um when the etching time reached 16.7 hours. The smallest width of through-hole by PAECE is 21 um, and the highest aspect ratio is 17.7. The related experimental parameters are described as followed: illumination is 18000-32000 lux, chose surfactants are 1 wt.% DC-1, 1 wt.% MA, 2.5 wt.% H2O2 and 1 wt.% Alcohol. The black micro holes array fabricated by PAECE 2 hr with 1 wt.% MA has ultra-low reflectivity 0.43%, and reflectivity of through-holes array also has equal values about 0.4-05%. Results of this research proved that PAECE technology had been able to partially replace the dry etching technology. It has advantages for applications of integrated probe array and interconnection of wafer-level package. After PAECE fabrication, the black micro holes array will be applied to antireflective structure of solar cell to improve the efficiency obviously.