First Micromachined Silicon Load Cell for Loads up to 1000 kg

In this paper, a bulk micromachined silicon load cell is presented, designed for loads up to 1000 kg. ANSYS simulations were used to determine the load cell dimensions and strain gauge positions. The load cell consists of two parts, which are bonded to each other using Low Temperature Silicon Direct Bonding processes (LTSDB). To isolate the membrane with the sensors from lateral displacements within the load cell (e.g. expansion due to compression) thin silicon springs are incorporated in the design. To make these springs, a cryogenic RIE process with a high selectivity for resist was developed. A special housing was developed to apply a homogeneous load to the load cell. The sensor was successfully tested with loads up to 1000 kg using poly-silicon strain gauges