MEMS Electrostatic Energy Harvester Developed by Simultaneous Process for Anodic Bonding and Electret Charging

In this paper, we present a new structure and a process for electrostatic energy harvesters fabricated using a silicon-on-glass wafer. Conventional electret-based MEMS energy harvesters are produced using a silicon-on-insulator (SOI) wafer, which is inevitably accompanied by parasitic capacitances across the buried oxide layer. The new harvester, on the other hand, can be formed by individually developing silicon and glass parts and subsequently putting them together by anodic bonding, thereby virtually eliminating parasitic capacitance. Special caution is taken not to cause the destruction of the electret layer during high-temperature anodic bonding. The device has been successfully fabricated and experimentally confirmed to function as an energy harvester. This silicon-on-glass structure is beneficial in not only suppressing the parasitic capacitance but also increasing its output power compared with those made by the conventional SOI-based process.