Year: 1996
Type: conference-paper
Abstract: Monolithic silicon microphones have been fabricated which include on-chip JFET buffer amplifiers, providing a complete microphone plus electronics on a single silicon chip.Test data is presented showing sensitivities as high as 40 mV/Pa (-48 dB ref. lV/µBar), with routine sensitivity of 15 mV/Pa (-57 dB ref. lV/µBar) and bandwidth of 70 Hz to 20 kHz.Noise measurements show that electronics noise from the gate bias resistor is dominant, leading to ltf 2 noise spectral density.The fabrication of these microphones uses both surface and bulk micromachining (Fig. 1).Surface micromachining (precision electroforming) is used to make the perforated bridge electrodes, while bulk micromachining is used to form the diaphragm and through-hole.Diaphragms of p + doped silicon from I to 2 mm in diameter have been tested.A monolithic ion implanted JFET and polysilicon resistors are fabricated on-chip.An analysis of the theoretical attainable sensitivity of a micromachined condenser microphone will be presented.A theoretical Figure of Merit proportional to the microphone signal to noise ratio is derived, which allows the microphone design to be optimized.
Authors: J.J. Bernstein, J.T. Borenstein
Institution: Draper Laboratory
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: hybrid
OpenAlex ID: W3119701609