Fabrication of silicon condenser microphones using single wafer technology

A condenser microphone design that can be fabricated using the sacrificial layer technique is proposed and tested. The microphone backplate is a 1-μm plasma-enhanced chemical-vapor-deposited (PECVD) silicon nitride film with a high density of acoustic holes (120-525 holes/mm²), covered with a thin Ti/Au electrode. Microphones with a flat frequency response between 100 Hz and 14 kHz and a sensitivity of typically 1-2 mV/Pa have been fabricated in a reproducible way. These sensitivities can be achieved using a relatively low bias voltage of 6-16 V. The measured sensitivities and bandwidths are comparable to those of other silicon microphones with highly perforated backplates. The major advantage of the new microphone design is that it can be fabricated on a single wafer so that no bonding techniques are required