Abstract
Silicon microphones are among a broad range of devices known as
micro-electromechanical systems (MEMS), an emerging field in which various
sensors and mechanical devices are constructed on a single wafer using
processes developed for making Integrated Circuits (ICs). The chief advantage
of micromachining silicon microphones is cost. Several sensors can be
processed on a chip simultaneously and can be integrated with passive and
active electronic devices. Silicon micro-machined microphones (also known as
silicon microphones or MEMS microphones) have begun to emerge as a competitor
technology to the electret condenser microphone (ECM).
MEMS microphones are more compact than traditional microphone systems because
they capture sound and convert it to a digital signal on the same chip. When
sound waves hit the microphone' s membrane, a thin metal mesh in the middle of
the chip, it vibrates, producing a voltage that contains information about the
analogue sound signal. But since the analogue signal is produced and converted
to a digital signal on the same chip, it never has to experience the harsh
electromagnetic environment outside the circuit. And, because interference is
less of an issue, insulation is not needed. This allows engineers to place the
microphone anywhere that a chip can fit, for example, into a laptop in which
multiple microphones can even fit in the bezel surrounding a laptop' s monitor.
MEMS microphone solutions developed on the CMOS (complimentary metal oxide
semiconductors) MEMS platform frees consumer electronic device designers and
manufacturers from many of the problems associated with ECMs. CMOS MEMS
microphones also integrate an analogue-to-digital converter on the chip,
creating a microphone with a robust digital output. Since the majority of
portable applications will ultimately convert the analogue output of the
microphone to a digital signal for processing, the system architecture can be
made completely digital, removing noise-prone analogue signals from the
circuit board and simplifying the overall design.
Many of these new "miniature" silicon microphones for consumer and computer
communication devices are approximately one-half the size and operate on just
one-third the power of conventional microphones.
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