Page 16 - MEMS Mechanical Sensors

1.5 For Whom Is This Book Intended? 5

Table 1.1 Properties of Silicon and Selected Other Materials
Property Si {111} Stainless Al Al O SiO Quartz
2 3 2
Steel (96%)
Young’s modulus (GPa) 190 200 70 303 73 107
Poisson’s ratio 0.22 0.3 0.33 0.21 0.17 0.16
3
Density (g/cm ) 2.3 8 2.7 3.8 2.3 2.6
Yield strength (GPa) 7 3.0 0.17 9 8.4 9
Thermal coefficient of 2.3 16 24 6 0.55 0.55
expansion (10/K)
Thermal conductivity at 1.48 0.2 2.37 0.25 0.014 0.015
300K (W/cm⋅K)
o
Melting temperature ( C) 1,414 1,500 660 2,000 1,700 1,600

circular wafers with typical diameters of 100 mm (4 inches), 150 mm (6 inches), 200
mm (8 inches), or 300 mm (12 inches) in a variety of thicknesses. Amorphous silicon
does not have a regular crystalline form and contains many defects. Its main use has
been in solar cells, photo-sensors, and liquid crystal displays. Both amorphous and
polysilicon can be deposited as thin-films, usually less than about 5 µm thickness.
Other materials that are often used within the MEMS fabrication process include
glasses, quartz, ceramics, silicon nitride and carbide, alloys of various metals, and a
variety of specialist materials that are used for very specific purposes.

1.5 For Whom Is This Book Intended?

This book is intended for graduate researchers who have taken a first degree in elec-
tronics, electrical engineering, or the physical sciences. It is also aimed at senior
undergraduate students (years three or four) who are studying one of these courses.
The main subject area of the text is that of mechanical microsensors, and in order to
assist the reader in this respect, we have covered some of the fundamental principles
of applied mechanics that might not have been covered in detail during some of
these courses. Those who have a background in mechanical engineering will find
that this book provides an overview of some of the main transducer microfabrica-
tion techniques that can be used to make a variety of transducer systems. Overall, it
should become clear that there is a synergy between the electrical and mechanical
engineering disciplines, and those who work in the field of sensors and actuators
will have the joy of participating in one of the truly interdisciplinary fields in the
whole of science.

References

[1] Nexus MST market analysis, http://www.nexus-mems.com.
[2] Feynman, R. P., “There’s Plenty of Room at the Bottom,” Journal of Microelectromechani-
cal Systems, Vol. 1, No. 1, 1992, pp. 60–66.
[3] Brignell, J. E., and N. M. White, Intelligent Sensor Systems, Bristol, England: IOP
Publishing, 1994.
[4] Judy, J. W., “Microelectromechanical Systems (MEMS): Fabrication, Design and Applica-
tions,” Smart Materials and Structures, Vol. 10, 2001, pp. 1115–1134.