Oxide growth in cluster tools

Abstract

It is shown that wafer processing systems in which wafer pre-clean, dry oxidation and polySi deposition processes are integrated in one vacuum system are very useful to grow thin oxide films with (sub-)monolayer control. Most attention is paid to batch-type cluster systems. The wafer pre-clean is based on vapor-phase HF etch processes. The background H 2O, O 2 concentrations appear to play a major role in such systems. By admixing a small amount of oxygen to the 100 Pa pure nitrogen ambient, surface roughening can be prevented. The capabilities of such systems are illustrated by showing that Si-Si contacts with low contact resistance, poly-emitter structures with tunable, sharply-peaked gain distributions, and poly-gate structures with high electric breakdown fields can be produced. Life tests in which the poly-gate capacitors are current-stressed indicate that HF vapor pre-cleans lead to a lower failure rate at early times than wet HF pre-cleans. However, the charge-to-breakdown (Q bd) of HF vapor etched samples is roughly 10% lower than that of those etched in wet HF solutions. This might be caused by a somewhat larger surface roughening in the HF vapor case.