Low cost thin film based piezoresistive MEMS tactile sensor

Most reported MEMS tactile sensors are fabricated by silicon micromachining process. Presently, the cost of the silicon-based MEMS fabrication is still relatively high, thus alternative process should be developed for low cost applications. In this work, we develop a low-cost non-silicon-based process for MEMS tactile sensor fabrication. The MEMS tactile sensor with a trampoline membrane structure has been fabricated by successive sputtering of Cr, Al, AlN, indium tin oxide (ITO), and Au layers through electroplated Ni micro-shadow masks over an 8 μm-thick photoresist sacrificial layer on a glass substrate. In addition, the sensitivity of the sensor has been optimized by controlling sputtering parameters including oxygen flow rate and film thickness of the ITO piezoresistive layer. The fabricated tactile sensor has been tested for displacement and force sensing by a Dektak surface profiler. The fabricated sensor is capable of small force sensing in μN ranges with good linear sensitivity of 0.2 mV/μN.