Fabrication of wide and deep cavities for silicon MEMS devices without wafer bonding

This paper presents a novel, versatile process for the fabrication of wide and deep cavities for silicon MEMS devices without the need for wafer bonding. Instead of filling large trenches with sacrificial materials before encapsulation or directly using wafer bonding, we present a method that utilizes isotropic etching with XeF
₂
gas through a thin silicon dioxide film prior to the deposition of encapsulation materials to create and encapsulate large cavities. The process is demonstrated to be robust and can be easily incorporated into the fabrication of a variety of MEMS structures, including pressure sensors, ultrasonic devices, microfluidics chips, hermetically encapsulated silicon resonators, inertial sensors, and more.