Deep silicon etching in inductively coupled plasma reactor for MEMS

We have used an inductively coupled plasma (ICP) reactor to etch deep featu res with SF6/C4F8 pulsed processes. Microelectromechanical system (MEMS) ap plications require 10-500 mu m deep structures to be etched into silicon. T he etch rate has to be carefully defined: in plasma etching the etch rate i s a function of feature size (RIE lag), of etch time (ARDE,aspect ratio dep endent etching) and loading (pattern density). Three processes have been ch aracterized with respect to etch rate, loading, RIP-lag, ARDE and sidewall profile. The high rate process has 5 mu m/min maximum etch rate but it exhi bits severe RIE-lag and ARDE. Two other processes with maximum etch rates o f 3.5 mu m/min and 1.6 mu m/min are much less prone to RIE-lag and ARDE. Et ch profiles and their non-idealities have been studied. Vertical, positivel y sloped, negatively sloped and barrel-like profiles result depending on pr ocess and feature size.