A dicing free SOI process for MEMS devices

This paper presents a full wafer, dicing free, dry release process for MEMS silicon-on-insulator (SOI) sensors and actuators. The developed process is particularly useful for inertial sensors that benefit from a large proof mass, for example accelerometers and gyroscopes. It involves consecutive front and backside deep reactive ion etching (DRIE) of the substrate to define the device features, release holes, and trenches. This is followed by hydrofluoric acid vapor phase etching (HF VPE) to release the proof mass and the handle wafer underneath to allow vertical displacements of the proof mass. The release process also allows the devices to be detached from each other and the substrate without the need of an extra dicing step that may damage the delicate device features or create debris. In the work described here, the process is demonstrated for the full wafer release of a high performance accelerometer with a large proof mass measuring 4 × 7 mm2. The sensor was successfully fabricated with a yield of over 95%.

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► We present a wafer level and dicing free MEMS-SOI fabrication process.
► Based on this work, a detailed set of design rules is also developed.
► This enables the process to be used for a wide range of MEMS devices.
► The process is demonstrated to fabricate high performance accelerometers.
► Using the design rules, they were fabricated with a high yield of >95%.