Page 27 - Microsensors, MEMS and Smart Devices - Gardner Varadhan and Awadelkarim

2

Electronic Materials and

Processing

2.1 INTRODUCTION

Integrated circuit (1C) processing is a mature technology for the fabrication of electronic
devices and systems. Steady advances in 1C fabrication technology have been the basis
for the microelectronic revolution, starting with the first discrete germanium transistors in
the 1950s to the 64-MB dynamic random access memories (DRAMs) of today. The main
purpose of this chapter is to introduce the reader to the basic terminology and to provide a
basic overview of the processing steps required to process silicon wafers. Therefore, this
chapter begins with the introduction of a special group of materials that may be referred
to as electronic materials. These materials are commonly used in conventional 1C tech-
nologies and some of them are used as microelectromechanical system (MEMS) materials
(see following chapter). Electronic materials have no common physical or chemical prop-
erties: for instance, their electrical properties span the range from near-ideal insulators to
excellent conductors, and their chemical composition may consist of one atom in simple
materials to several atoms in compound electronic materials. Therefore, the term elec-
tronic materials has no physical or chemical meaning; it solely describes materials used
in IC fabrication.
A more detailed discussion of conventional silicon IC processing is presented in
Chapter 4, which describes the additional steps required to package electronic chips. There
are also a number of excellent textbooks that describe in full the processing of conven-
tional electronic IC chips, such as microprocessors and DRAMs (for further information
see Sze (1985, 1988); Fung et al. (1985)).

2.2 ELECTRONIC MATERIALS AND THEIR
DEPOSITION

Many different kinds of bulk materials and thin films are used in the fabrication of ICs. The
bulk materials are predominantly semiconducting. The most important semiconductors in
IC fabrication are silicon and gallium arsenide. There are four important thin-film materials
(or class of materials) in IC fabrication: