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3 MEMS Fabrication

James J. Allen

CONTENTS

3.1 Introduction.................................................................................................... 35
3.2 MEMS Fabrication Technologies ................................................................. 36
3.3 LIGA.............................................................................................................. 38
3.4 Bulk Micromachining.................................................................................... 40
3.4.1 Wet Etching........................................................................................ 41
3.4.2 Plasma Etching................................................................................... 44
3.5 Sacrificial Surface Micromachining.............................................................. 46
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3.5.1 SUMMiT V ............................................................................... 52
3.6 Integration of Electronics and MEMS Technology...................................... 55
3.7 Additional MEMS Materials......................................................................... 60
3.7.1 Silicon Carbide................................................................................... 60
3.7.2 Silicon–Germanium ........................................................................... 61
3.7.3 Diamond ............................................................................................. 62
3.7.4 SU-8.................................................................................................... 62
3.8 Conclusions.................................................................................................... 62
References............................................................................................................... 63

3.1 INTRODUCTION

Making devices small has long had engineering, scientific, and esthetic motivations.
1
John Harrison’s quest to make a small (e.g., hand-sized) chronometer in the 1700s
for nautical navigation was motivated by the desire to have an accurate time-keeping
instrument that was insensitive to temperature, humidity, and motion. A small chron-
ometer could meet these objectives and allow for multiple instruments on a ship for
redundancy and error averaging. The drive toward miniaturization of various mech-
anical and electrical devices advanced over the years, but in the 1950s several key
events occurred that would motivate development at an increased pace.
2
The development of the transistor in 1952, and a manufacturing method for
a planar silicon transistor 3,4 in 1960 set the stage for development of fabrication
processes to achieve small feature sizes. The drive for microelectronic devices with
smaller and smaller features continues to the present day.
Dr. Richard Feynman presented a seminal talk ‘‘There’s Plenty of Room at the
Bottom’’ on December 29, 1959 at the annual meeting of the American Physical

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