Thin film membrane based on a-SiGe: B and MEMS technology for application in cochlear implants

In this work is presented the fabrication of a thin film membrane as a bio-transducer for aural assistance detection, therefore it will operate at low pressure. The resonant membrane was deposited by PECVD technique at low temperature of deposition T = 270 °C, using SiH4, GeH4, and Boron gases. The membrane was suspended on a micromachined crystalline silicon frame obtained by wet chemical etching. The a-SiGe:B film presented a resistivity of 2.46 × 103 (Ω-cm), resistance of 20.8 kΩ. Using these experimental data we succeeded in designing a simple structure for sensing low pressure variations. The output voltage of the sensor was measured for a range of pressure from 0 to 3000 Pa and at bias voltage of 10 V.

► A pressure sensor using a membrane structure was fabricated at the first time.
► The membrane is based on a-SiGeB thin films deposited by LF-PECVD.
► The aSiGe: B presented a resistivity of 2.4 × 103 (Ω-cm), and a resistance of 20.8 kΩ.
► The sensor showed a sensitivity of .03mVPa-1with changes of resistance in kΩ.
► The fabrication process allows integration at low T of processing for Si- technology.