HIGH ASPECT RATIO TRENCH ISOLATION PROCESS FOR SURFACE MICROMACHINED SENSORS AND ACTUATORS

摘要

HIGH ASPECT RATIO TRENCH ISOLATION PROCESS FOR SURFACE MICROMACHINEDSENSORS AND ACTUATORSA process for fabricating an integrated circuit sensor/actuator is described. Highaspect ratio deep silicon beams are formed by a process of deep trench etch and siliconundercut release etch by using oxide spacers to protect the silicon beam sidewalls duringrelease etch. An oxide layer is then formed, followed by deposition of a controlled thicknessof polysilicon which is then thermally oxidized. The polysilicon layer inside the trenches getsfully oxidized resulting in void-free trench isolation. This process creates a silicon island orbeam on three sides leaving the third side for interfacing with the sensor/actuator beams.The sensor/actuator is formed by a similar process of deep trench etch and release etchprocess on the same substrate. These suspended beams of the sensors and actuators arebridged with the silicon islands from the fourth side. The above process finally results insuspended silicon beams connected to electrically isolated silicon islands.