The evolution of the ion implantation damage in device processing

In this article the phenomenology related to the mechanisms of defect generation in Shallow Trench Isolation (STI) processes is discussed, and the role of the structure pattern is investigated. Defect formation is studied by plan and cross TEM analyses of wafers with different boron doses and after annealing at various temperatures. In addition, to obtain a wider statistics our analysis was extended by electrical measurements of defect-sensitive structures. It is shown that a modification of the STI flow suppresses the main mechanism of mechanical stress accumulation, hence stress-induced defects are eliminated. However, this approach is found to be critical from the point of view of the implantation damage recovery, specifically for what concerns the implantations carried out before the trench etch. This result can be explained by the role of the silicon surface in reducing the point defect excess generated in the implantation. As a consequence, in this example the presence of the STI structure is beneficial, in that it assists in annealing implantation-related defects. An attempt is also presented to model the evolution of implantation-induced defects by a Kinetic Monte Carlo code. The calculation results are promising, though the capabilities of the model are limited by the computation time.