Physics-based diffusion simulations for preamorphized ultrashallow junctions

In recent years there have been major advances in our understanding of the energetics, Ostwald ripening and transformations between various types of extended self-interstitial defect in Si and Ge ion-implanted silicon. As a result we can now predict the detailed time- and temperature-dependent supersaturation of interstitials during thermal evolution of these defects. This opens the way to predictive simulation of transient enhanced diffusion and dose loss in preamorphized ultrashallow junctions, where dopant movement is driven by free interstitial emitted by self-interstitial "end-of-range" defects. We present recent progress on this topic, emphasizing novel effects in highly doped ultrashallow junctions. Two key influences - the chemical pump effect due to the high concentration of dopants in ultrashallow junctions, and the 'long hop' behaviour of the dopant - are discussed in detail. The paper concludes by presenting simulation results that explain the recent observation of 'uphill diffusion' of B ultrashallow junction profiles.