Preparation of macroporous silicon array by micromachining processes

A macroporous silicon arrays (MSA) was prepared based on bulk-micromachining technology by both dry and wet etching processes respectively. In dry etching, MSA with 15-30 aspect ratio of the microchannel, 6-20 ¿m dimension of pore, 6-8 ¿m space were prepared by Inductively Coupled Plasma (ICP) etcher. It was shown that there are very differences in process of high aspect ratio microstructures between the deep pores, a closed structure, and the deep trenches, a open structure. The morphology and the aspect ratio dependent etching were analyzed and discussed. The macroporous silicon etched by ICP process yields an uneven, re-entrant, notched and ripples surface within the pores. The main factors effecting on the RIE lag of HARP etching are the passivation cycle time, the pressure of reactive chamber, and the platen power of ICP system. In wet process, an n-type silicon wafer was selected as the substrate for MSA with 50 of aspect ratio by photo-electrochemical (PEC) etching techniques. The electrochemical mechanism of silicon anisotropy etching were investigated and discussed. The results shown the electrochemical process for macroporous silicon arrays has lower cost and more simple steps than ICP process.