Through-wafer electrical interconnect for multilevel microelectromechanical system devices

Abstract

This article reports the design, fabrication, and experimental demonstration of through-wafer interconnects capable of allowing direct electrical access to the interior of a multilevel microelectromechanical system device. The interconnects exploit the ability to conformally coat a high aspect ratio trench with a thick layer of tetraethylorthosilicate to isolate a through-wafer silicon plug that can provide electrical contact across two sides of a low resistivity wafer. They hold the potential of a tenfold reduction in the parasitic capacitance of previously reported through-wafer vias, and are shown to make reliable contacts to the back side of a polysilicon resistive element. The high temperature capability of the interconnects is also examined, however, their application is found to be limited to temperatures below 1000 °C due to localized degradation near the isolating trenches.