A new method of forming a thin single-crystal silicon diaphragm using merged epitaxial lateral overgrowth for sensor applications

Merged epitaxial lateral overgrowth (MELO) of silicon was combined with an SiO/sub 2/ etch stop to form a 9- mu m-thick and 250- mu m*1000- mu m single-crystal Si membrane for micromechanical sensors. When epitaxial lateral overgrowth (ELO) silicon merges on SiO/sub 2/ islands, it forms a local silicon-on-insulator (SOI) film of moderate doping concentration. The SiO/sub 2/ island then acts as a near-perfect etch top in a KOH- or ethylenediamine-based solution. The silicon diaphragm thickness over a 3-in wafer has a standard deviation of 0.5 mu m and is precisely controlled by the epitaxial silicon growth rate ( approximately=0.1 mu m/min) rather than by conventional etching techniques. Diodes fabricated in the substrate and over MELO regions have nearly identical reverse-bias currents, indicating good quality silicon in the membrane.<
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