ISOLATION IMPLANT STUDIES IN GAAS

The use of implant damage to provide electrical isolation between devices on GaAs substrates was studied. Singly ionized oxygen and singly and doubly ionized boron ions were implanted into bulk doped GaAs substrates at various doses and energies. Carrier concentration profiles of the damage region were used to determine the characteristics of the ion damage profiles (i.e., damage peak and carrier removal per incident ion). These measurements were performed on as-implanted wafers and on samples subjected to temperature cycling that simulates routine wafer processing. The results indicate that both boron and oxygen remove nearly 100 carriers per incident ion and that the damage produced by oxygen ions is more temperature stable. Isolation implants were subsequently performed into wafers whose active layers were formed by implantation and annealing. Leakage current was measured as a function of isolation implant dose. Results indicate that for blanket implanted active layers a minimum in leakage current exists for isolation doses approximately equal to one-tenth of the active layer implant dose. Increasing the isolation dose leads to large increases in leakage current. A simple method for tailoring the isolation implant profile to the active layer profile is presented. © 1990, The Electrochemical Society, Inc. All rights reserved.