Oxygen Stabilization of Damage Induced by Mev Ion Implantation

Abstract

ABSTRACTAs devices are scaled down and their performance is enhanced, the role of oxygen in silicon remains critical. The precipitation of oxygen away from the device region leads to desirable gettering of deleterious impurities and is a useful technique. In the device region, however, oxygen has recently been shown to take part in the annealing of dopant implants and segregate to damaged regions. This may result in the stabilization of damage structures and the attraction of unwanted impurities to sensitive regions of the device. In this work we examine these phenomena and their potential impact on device performance. For example, oxygen has been observed to segregate at two positions following a 1000°C, one hour anneal of a 2 MeV, 3.5×1015/cm2 phosphorus implant into CZ p-Si. The oxygen concentration is greatly enhanced above its initial level of 1018 O/cm3, both in the end-of-range region and at approximately half that depth, near the peak of the predicted damage profile. Iron deliberately introduced at the surface prior to annealing, getters out strongly at these locations No significant redistribution of carbon can be detected. The results assume significance in view of the increasing use of high energy implantation for both epi-layer replacement and retrograde well formation.