| With advancing semiconductor process, devices become smaller and smaller, it is necessary to create sharp, ultra-shallow profiles with high concentrations of electrically active dopants. According to SIA, for the 0.18μm characteristic length, the junction deep is approximate to 54 ±18nm, for 0.1μm length, the junction deep will be 30 ±10nm. Therefore, ultra-shallow junction of process and simulation are the important things for IC industry. Ion implantation is the most widely used technique for forming shallow junctions. The recent trends in integrated circuit processing point towards the use of low temperature anneals to limit the redistribution of dopants. However, this method decreases the percentage of impurities activation. Boron is the commonly used dopant in Si processing for the formation of p-type doped regions. Anomalous diffusion of ion-implanted boron during thermal anneal is the main problem in shallow junction formation. Besides TED (transient enhanced diffusion), a striking feature of anomalous diffusion is that the peak portion of boron profile is not electrically activated and has remained immobile during annealing. For this study, uniformly boron-doped wafers were used to investigate the impact of ion implant damages on the redistribution of boron atoms. Si ions instead of dopants such as B, P and As atoms were implanted into the Si wafers to avoid data analysis difficulties. With the analysis of the evolution of defects, it shows that the defects change with exponential in different annealing time, and the constant of exponential time is correlative with binding energy between defects and interstitials, the binding energy of 2.41eV is proposed in this model. The similar tendency and approximate evolution time show that the evolution of boron-peak is correlative with RP defects. At present, simulation tools designed to predict dopant diffusion during device processing are not capable of dealing with this phenomenon in a... |
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