Steven E. Staller

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.<<ETX>>

A novel method of forming a thin single crystal silicon diaphragm with precise thickness for potential use in fabricating micromechanical sensors using merged epitaxial lateral overgrowth

A novel epitaxial growth and micromachining technology were used for form a thin single-crystal silicon diaphragm for micromechanical sensors. Merged epitaxial lateral overgrowth (MELO) of silicon and SiO/sub 2/ etch-stop technology were successfully used to fabricate a diaphragm with a precise thickness. Its implementation to the formation of a large thin diaphragm is demonstrated. The silicon epitaxial growth rate is the only controlling parameter to define the diaphragm thickness. An average growth uniformity of the MELO film across the three-inch wafers was determined to be less than 5%. However, the average percentage variation of the growth at the same position on the wafer, from wafer to wafer in a single run, was measured to be within 2%. Diaphragms of 9+or-0.05 mu m thick and more than 200 mu m wide and 1000 mu m long were successfully fabricated using this technique.<<ETX>>