Papers by Author: M.M. De Souza

Abstract: Heavy species such as Sb, In, and Ge are required to meet the challenges of future dopant engineering in planar CMOS technology. An understanding of the interactions of these species with each other and with conventional dopants is urgently required in order to meet aggressive criteria for junction control in sub-sixty nanometer technology nodes. In the current work, the interactions between Sb and In have been explored as a function of ion implantation dose and annealing treatment. The data shows strong interaction between the two species which prevents the dissolution of an as-implanted In profile even after high temperature anneal. The nature of the interaction is probed with fundamental calculations using plane wave density functional theory. A strong binding for an Sb-In-vacancy complex is revealed. Band structure analysis indicates that this defect complex introduces several unoccupied states primarily in the upper half of the bandgap. The two species contribute with nearly equal magnitude to the top valence band.

Abstract: A cluster comprising of indium, antimony and a vacancy in silicon is analysed using the planewave pseudopotential technique. This cluster has a strong binding energy that inhibits indium diffusion after high temperature anneal cycles. Difficulties associated with the simulation of a vacancy using the supercell approach are initially highlighted. In comparison, the indium-antimony-vacancy cluster reveals stronger distortions and reduction in relaxation volume. The indium atom in the relaxed cluster shows nearly six-fold coordination whereas the antimony atom acquires four neighbours. Due to the low symmetry of the centre, in constrast to the isolated vacancy there is no propensity for a Jahn-Teller effect. It gives rise to two defect levels in the bandgap.