Page 10 - MEMS Mechanical Sensors

Preface

The field of microelectromechanical systems (MEMS), particularly micromachined
mechanical transducers, has been expanding over recent years, and the production
costs of these devices continue to fall. Using materials, fabrication processes, and
design tools originally developed for the microelectronic circuits industry, new
types of microengineered device are evolving all the time—many offering numerous
advantages over their traditional counterparts. The electrical properties of silicon
have been well understood for many years, but it is the mechanical properties that
have been exploited in many examples of MEMS. This book may seem slightly
unusual in that it has four editors. However, since we all work together in this field
within the School of Electronics and Computer Science at the University of South-
ampton, it seemed natural to work together on a project like this. MEMS are now
appearing as part of the syllabus for both undergraduate and postgraduate courses
at many universities, and we hope that this book will complement the teaching that
is taking place in this area.
The prime objective of this book is to give an overview of MEMS mechanical
transducers. In order to achieve this, we provide some background information on
the various fabrication techniques and materials that can be used to make such
devices. The costs associated with the fabrication of MEMS can be very expensive,
and it is therefore essential to ensure a successful outcome from any specific produc-
tion or development run. Of course, this cannot be guaranteed, but through the use
of appropriate design tools and commercial simulation packages, the chances of
failure can be minimized. Packaging is an area that is sometimes overlooked in text-
books on MEMS, and we therefore chose to provide coverage of some of the meth-
ods used to provide the interface between the device and the outside world. The
book also provides a background to some of the basic principles associated with
micromachined mechanical transducers. The majority of the text, however, is dedi-
cated to specific examples of commercial and research devices, in addition to dis-
cussing future possibilities.
Chapter 1 provides an introduction to MEMS and defines some of the com-
monly used terms. It also discusses why silicon has become one of the key materials
for use in miniature mechanical transducers. Chapter 2 commences with a brief dis-
cussion of silicon and other materials that are commonly used in MEMS. It then
goes on to describe many of the fabrication techniques and processes that are
employed to realize microengineered devices. Chapter 3 reviews some of the com-
mercial design tools and simulation packages that are widely used by us and other
researchers/designers in this field. Please note that it is not our intention to provide
critical review here, but merely to indicate the various features and functionality

ix