TABLE OF CONTENTS One of the unique properties of semiconductor materials is that their conductivity and the type of conductivity (N or P) can be created and controlled. In this chapter, the formation of specific "pockets" of conductive regions and N-P in and on the wafer surface is described. The principles and practice of the two doping techniques, diffusion and ion-implantation, are explained.
Upon the completion of this chapter, you should be able to:
Define an N-P junction.
Draw a flow diagram of a complete diffusion process.
List the three most common dopants used in silicon technology.
List the three types of deposition sources.
Draw a typical concentration-versus-distance curve for a deposition and drive-in.
List the major parts of an ion implanter.
Describe the principle of an ion implanter.
Compare the advantages and disadvantages of diffusion and ion implant processes.
The structure that makes transistors and diodes work is an N-P or N-P junction. A junction is the separation between a region that is rich in negative electrons (N-type region) and a region that is rich in holes (P-type region). The exact location of a junction is where the concentration of electrons equals the concentration of holes. This concept is explained later in the section, "Formation of a Doped Region and Junction by Diffusion."
The usual way to form junctions in the surface of semiconductor wafer is by thermal diffusion or by ion implantation. With thermal diffusion, dopant...
