Handbook of Silicon Based MEMS Materials and Technologies

23.3.1. DRIE of Silicon

The main DRIE techniques are Bosch and cryo-processes [14–16]. The Bosch process is also known as a “switched process” or “time domain multiplexed process.” Both Bosch and cryo-processes use purely fluorine-based plasma chemistry, since fluorine-based etching processes for silicon offer superior etch rates and high mask selectivities. In particular, simple photoresist masking and easy resist removal make fluorine processes attractive. However, because of the high chemical reactivity and spontaneous etching nature of the fluorine radicals, and the high volatility of the silicon fluorides, the etch is intrinsically isotropic. Since fluorine radicals do not need ion activation to initiate or enhance their reaction with silicon, ...