A maskless wet etching silicon dioxide post-CMOS process and its application

The complementary metal oxide semiconductor (CMOS) surface micromachining post-process for fabricating suspended microstructures has been investigated. The post-process requires only one wet etching to remove sacrificial layers, which uses a silox vapox III etchant to etch the silicon dioxide layers and to release the suspended structures. The advantages of the post-process are easy execution and low-cost maskless wet etching. Many microstructures, which contain cantilever beams, comb structures and microrotors, are fabricated using the CMOS surface micromachining post-process. Using the same process, two devices such as a radio frequency (RF) switch and a micro-xy stage are successfully developed. Experimental results reveal that the RF switch has an insertion loss of −1.7 dB at 40 GHz and an isolation of −11 dB at 40 GHz. The driving voltage of the RF switch is 19 V.