Silicon as a Mechanical Material

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420 PROCEEDINGS OF THE IEEE, VOL. 70, NO. 5, MAY 1982
Silicon as a Mechanical Material
KURT E. PETERSEN, MEMBER, IEEE
Abstract-Single-crystal silicon is being increasingly employed in a variety of new commercial products not because of its well-established electronic properties, but rather because of its excellent mechanical properties. In addition, recent trends in the engineering literature indicate a growing interest in the use of silicon as a mechanical material with the ultimate goal of developing a broad range of inexpensive, batch-fabricated, high-performance sensors and transducers which are easily interfaced with the rapidly proliferating microprocessor. This review describes the advantages of employing silicon as a mechanical material, the relevant mechanical characteristics of silicon, and the processing techniques which are specific to micromechanical structures. Finally, the potentials of this new technology are illustrated by numerous detailed examples from the literature. It is clear that silicon will continue to be aggressively exploited in a wide variety of mechanical applications complementary to its traditional role as an electronic material. Furthermore, these multidisciplinary uses of silicon will significantly alter the way we think about all types of miniature me chanical devices and componenta

I. INTRODUCTION
.
IN THE SAME WAY that silicon has already revolutionized
the way we think about electronics, this versatile material is now in the process of altering conventional perceptions of
miniature mechanical devices and components [ 1]. At least
eight firms now manufacture and/or market silicon-based pressure transducers [ 2] (first manufactured commercially over 10
years ago), some with active devices or entire circuits integrated on the same silicon chip and some rated up to 10 000 psi.
Texas Instruments has been marketing a thermal point head
[ 3] in several computer terminal and plotter products in which the active printing element abrasively contacting the paper is a silicon integrated circuit chip. The crucial detector component of a high-bandwidth frequency synthesizer sold by Hewlett-

Packard is a silicon chip [4] from which cantilever beams have been etched to provide thermally isolated regions for the diode detectors. High-precision alignment and coupling assemblies
for fiber-optic communications &stems are produced by
Western Electric from anisotropically etched silicon chips
simply because this is the only technique capable of the high accuracies required. Within IBM, ink jet nozzle arrays and
charge plate assemblies etched into silicon wafers [5] have
been’ demonstrated, again because of the high precision capabilities of silicon IC technology. These examples of silicon
micromechanics are not laboratory curiosities. Most are wellestablished, commercial developments conceived within about
the last 10 years.
The basis of micromechanics is that silicon, in conjunction
with its conventional role as an electronic material, and taking advantage of an already advanced microfabrication technology, can also be exploited as a high-precision high-strength highreliability mechanical material, especially applicable wherever

Manuscript received December 2, 1981; revised March 11, 1982. The submission of this paper was encouraged after the review of an advance proposal.
The author was with IBM Research Laboratory, San Jose, CA 95193. He is now with Transensory Devices, Fremont, CA 94539.
miniaturized mechanical devices and components must be
integrated or interfaced with electronics such as the examples given above.
The continuing development of silicon micromechanical
applications is only one aspect of the current technical drive toward miniaturization which is being pursued over a wide
front in many diverse engineering disciplines. Certainly silicon microelectronics continues to be the most obvious success in the ongoing pursuit of miniaturization. Four factors have
played...
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