Evaluation of o₂ plasma and xef₂ vapor etch release processes for rf-mems switches fabricated using cmos interconnect technology

Abstract

This paper evaluates two commercially available dry etch processes for releasing integrated RF MEMS devices. The first is an oxygen microwave plasma removal of a Diamond-Like Carbon (DLC) sacrificial layer and the second is a XeF2 vapor phase removal of an amorphous silicon (a-Si) sacrificial layer. The studied techniques were selected for compatibility in fabricating monolithically integrated RF-MEMS devices within the interconnect levels of CMOS and Bi-CMOS technologies. To determine the etch rate of the sacrificial release layer, test wafers were fabricated using a simple 1-mask lithography level that allows direct observation of the release etch through a dielectric membrane. Effects relating to changes in the release etch rate are documented and discussed. Additionally, the ability of XeF2 to extract sacrificial layers through small via holes, and bulk vs. thin-film etching of a-Si for MEMS release etches are presented. The results of this study demonstrate that both oxygen microwave plasma removal of DLC and XeF2 vapor phase etch of a-Si can be used to manufacture RF-MEMS devices using high volume CMOS interconnect manufacturing processes.