Low temperature through-wafer reactive ion etching for MEMS

This paper presents the results of experimental work on a low temperature through-wafer reactive ion etching (RIE) technique obtained in the course of development of a process that can be used in small sample processing for microelectromechanical systems (MEMS). Low temperature RIE are a crucial step for many dry MEMS fabrication processes, where can be used to fabricate silicon vias, trenches, and to perform dry release of membranes and other devices. The through-wafer etch developed here can be used also to separate fabricated devices, especially when it is desirable to produce non-rectangular shapes, which cannot be cut using a dicing saw. The presented process works with large silicon wafers as well as with small samples. In this work we developed a method which allows for stabilization of the sample temperature at the correct level during the entire process, which allows through wafer etch of thick silicon samples. The results obtained indicate that there is no universal process suited to all applications. Here we present three different recipes suitable for various applications.