DEVELOPMENT OF 3-DIMENSIONAL MICROSTRUCTURE PROCESSING USING MACROPOROUS N-TYPE SILICON

The development of a micromachining technique for processing arbitrary structures with high aspect ratios in bulk silicon is presented. It i s based on utilizing standard microelectronic processes and electroche mical macropore formation on n-type silicon in electrolytes containing hydrofluoric acid. This pore-etching technique allows us to produce v ery regular pore arrays with pore diameters and distances in the micro meter range and pore lengths up to wafer thickness. Samples with prefa bricated pore arrays which differ in pore spacing, pore diameter and g eometry are used as substrates for a micromachining process. The pores will facilitate the anisotropic etch profile which is required for th e desired high aspect ratios although an isotropic etch process is use d. Very deep microstructures with steep pore walls and aspect ratios o f 10-15 are produced with this technique. It is shown that smaller por e array dimensions improve microstructure resolution.