Pressure sensor using p-type polycrystalline diamond piezoresistors

Prototype pressure sensor was fabricated using piezoresistive effect of boron-doped diamond. Undoped and boron-doped polycrystalline diamonds were deposited on Si substrate using hot filament chemical vapor deposition (CVD) method. The boron-doped diamond was deposited on an isolation layer of the undoped diamond film. Selective diamond deposition was carried out by metal mask, and 30-μm width patterning of the diamond was possible. In order to improve a sensitivity of the sensor, the diaphragm thickness and boron doping depth were varied from 62 to 5 μm and 2 to 0.5 μm, respectively. The sensors were evaluated in the ranges from room temperature to 250 °C and from 0 to 0.07 M Pa of applied pressure.