Browsing by Subject "Ion implantation"
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Item Molecular dynamic simulations of self-interstitials in silicon(Texas Tech University, 2002-05) Gharaibeh, Maen AAb initio molecular-dynamics simulations in periodic supercells containing 64 up to 216 Si host atoms were used to study the static and dynamic properties of neutral self- interstitial aggregates, In,in silicon. The lowest energy configurations for In, n<5, have been identified. Each of I and I2 has one local minimum, while the potential energy surface for aggregates of three or more Ifs have 2 several local minima, leading to a range of metastable configurations. Constant temperature runs show that I2 and the most stable I3‹ clusters are highly mobile. In these complexes, all the self-interstitials are located around a single bond centered site, a feature that greatly facilitates exchange process and is responsible for the rapid diffusion. Simulations of Ib3 show that the three Is exchange sites with each other, but the center of the defect remains at the same place. Simulations of I and I4 show no diffusion or exchange on the same time scale. Next, the highly mobile Ia3 units' are assumed to be the building blocks for self-interstitial precipitates. We study the interactions Ia3 + Ia3 ¨I6 and I6 + Ia3¨I9 by bringing an Ia3 toward either Ia3 or I6 along various crystalline directions in 216 host silicon atoms supercells. The calculations show that these reactions occur at a substantial gain in energy and that the stacking along some directions is energetically preferred over others. The results suggest that precipitation mechanisms involving rapidly moving self-interstitial clusters could play an important role in the formation of extended defects.Item Ultra-shallow junction formation : co-implantation and rapid thermal annealing(2002-08) Li, Hong-jyh; Banerjee, SanjayBoron diffusion and activation in the presence of co-implanted species are studied experimentally and theoretically (ab initio Molecular Dynamics simulations and SUPREM diffusion process simulator) in this dissertation. Simulation results imply that B diffusion and activation in the presence of coimplanted species can be affected through both the electronic and strain compensation effects and the theoretical prediction is consistent with experimental data. In the presence of co-implanted species, the electronic bonding between B and the co-implant species makes it energetically unfavorable for B to migrate when it comes close to the co-implant species. The bonding can be characterized by the electronegativity difference between B and the coimplanted species. The strain effect, on the other hand, indicates that B tends to stay close to the larger co-implant species (In, for example) so that the strain caused by the size misfit of In and Si can be compensated by the smaller B atom. In order to have both the above factors be effective in B diffusion reduction, we need to increase the concentration of the co-implant species in order to maximize the B diffusion reduction with the co-implant technique. Experiments on B diffusion and activation in the presence of Al, Ga, In, Ge, F and C, with or without capping layers (oxide, nitride or Si), are conducted in this research. Those species are incorporated into Si either by ion implantation or Chemical Vapor Deposition (CVD) process. Boron and co-implant diffusion and activation is studied Rapid Thermal Annealing (RTA) for various process parameters such as ramp-up rate, soak time and peak temperature. Fundamental studies on the interaction of B, defects and the co-implanted species are also included in this dissertation.