Application of silane-free atmospheric-plasma silicon deposition to MEMS devices

We have developed a silane-free atmospheric-pressure plasma Si deposition process and investigated the properties of the deposited films by fabricating strain gauge type pressure sensors for the first time. The Si deposition process, which is known as plasma-enhanced chemical transport, utilizes the temperature difference between the solid Si source and the substrate in atmospheric hydrogen plasma. The Si films were deposited at a low temperature of 300 °C at 700 Torr. We have clarified that the Si films were composed of poly crystals by X-ray diffraction (XRD) patterns and Raman spectra. We fabricated strain gauges using the poly-Si films. The gauge factor of approximately 10 was achieved. The bridge voltage of the pressure sensor was found to be proportional to the pressure. The Si films are deemed appropriate for use as MEMS devices.