A capacitive silicon microphone has been fabricated. The component consists of two freestanding polysilicon membranes, a low-stress bending membrane and a high-stress backplate, which are separated by an air gap. Sound pressure changes the capacitance between the membranes. A back-chamber is arranged by encapsulation and static pressure changes are prevented with small equalisation holes in the bending membrane. The component is fabricated combining bulk and surface micromachining techniques. Silicon substrates are etched in TMAH and sacrificial oxide between the membranes is etched in PSG-etch followed by freeze drying to prevent sticking. The measured acoustic sensitivity of the microphone with 1 × 1 mm2 membrane was 2mV/Pa (1 kHz frequency) and the resolution 35 dB (A-weighted sound level).
|Number of pages||4|
|Journal||Physica Scripta: Topical Issues|
|Publication status||Published - 1 Dec 1999|
|MoE publication type||A4 Article in a conference publication|
|Event||18th Nordic Semiconductor Meeting, NSM18 - Linköping, Sweden|
Duration: 8 Jun 1998 → 10 Jun 1998