Deep reactive ion etching of in situ boron doped LPCVD Ge0.7Si0.3 using SF6 and O2 plasma

Abstract

► Fabrication of microelectromechanical resonator is demonstrated by DRIE of boron doped Ge 0.7 Si 0.3 . ► Etch profile control by oxygen flow for doped Ge 0.7 Si 0.3 . ► Increased etch selectivity towards oxide with an increase in temperature. ► Suppressed etch rate with increased boron concentration in Ge 0.7 Si 0.3 alloy. This paper reports on deep reactive ion etching (DRIE) of in situ highly boron doped low pressure chemical vapor deposited Ge 0.7 Si 0.3 alloy in SF 6 and O 2 plasma. The effect of RF power, SF 6 flow, O 2 flow and temperature on the etch rate of Ge 0.7 Si 0.3 films with a boron concentration of 2.1 × 10 21 atoms/cm 3 is investigated. Optimized conditions for a combination of a vertical etch profile and a high selectivity towards PECVD oxide are reported. The effect of boron doping concentration on the etch rate is also investigated. The etch rate is found to decrease with an increase in the dopant concentration. The developed SF 6 and O 2 based DRIE recipes are applied to fabricate GeSi microresonators.