5.1 Introduction

Device-level circuit design in VLSI requires a rather intimate knowledge of how devices are made. This is in contrast to the design of circuits made with discrete components, where one can use a commercially available transistor, knowing only its electrical parameters but not what it looks like inside the package or how it was made. In VLSI, a knowledge of device structures affords two advantages to the circuit designer: (1) The designer can choose device shapes, dimensions, and placement (the latter as part of the "layout" processes, discussed in Chap. 6); this represents a degree of freedom without which many state-of-the-art circuits would not have been possible. (2) The designer is able to determine the ways in which different devices, packed closely together on one chip, can interfere with each other and to devise ways to eliminate such interference.

This chapter is devoted to fabrication technology (often referred to simply as technology or fabrication processing or simply processing). A detailed exposition of fabrication technology can be found elsewhere [ ^{[1] [2] [3] [4] [5] [6]}]. The information provided here can be considered as the minimum needed for the design of relevant, working circuits (as opposed to circuits that work only "in principle," i.e., on paper). We will consider the most important fabrication processes and will describe the components such processes make available to the designer, including transistors, resistors, and capacitors. The reader is certainly familiar with the ideal models (i.e., the defining relations) of...