Observations of the Temperature Gradient Zone Melting Process for Isolating Small Devices

Abstract

The temperature gradient zone melting process (TGZM) for doping semiconductors is being investigated for the purpose of using it to create the isolation region in a relatively small geometry thyristor. The small size of the chip puts tougher morphological requirements on this liquid zone process than in past TGZM investigations. We discuss here a number of problems encountered which include enhanced diffusion of the aluminum dopant in the silicon, lateral motion of the molten zone at the edge of the wafer, breakup and smearing of the molten zone, and outdiffusion of the aluminum into the passivating oxide layer.