XEF_2 ETCHING OF SILICON FOR THE RELEASE OF MICRO-CANTILEVER BASED SENSORS

摘要

The release of microstrnctures from a Si substrate depends directly on the underetching (isotropic) characteristics of the etchant used. For the purpose of this study, XeF_2 gas was selected as the etchant medium. Etching by XeF_2 is primarily afunction of pressure, which determines the rate of interaction between the Si surface and the etchant gas. However, other factors play a large role in XeF2 etching characteristics. Testing was conducted to determine the etch rate and profile of XeF_2 etching when various parameters of the structure designare changed (Si exposure area, size and dimension of structures, spacing of structures). The gas was introduced at a pressure cycle of approximately 4.0 Torr for 180 s. Uniformity of the etched surface is improved by increasing the number of etch cycles, or by increasing the gas pressure of the surrounding XeF_2.