Kinetic reaction of the formation of the platinum related complex at the origin of the p-type doping effect in silicon

Platinum is widely used in power devices manufacturing to control minority carrier lifetime. In n-type silicon, when platinum is introduced at concentration similar to that of phosphorus, we observed a p-type doping effect, which can lead to a type inversion. This doping effect can be induced during the cooling stage of any thermal process and depends on the applied cooling rate. The lower the cooling rates, the higher the p-type doping. The acceptor state at the origin of this doping effect, located at 0.42 eV from the valence band, is attributed to a Pt-S related complex. A simple calculus of the equilibrium solubility of Pt-i, I, V, C and O-i in silicon makes them suitable for this complex formation with platinum. To decide between these species, we propose a kinetic study of the reaction Pt-s-X <----> Pt-s + X involved during the cooling stage of a platinum diffusion in silicon. The diffusion calculation is integrated by a finite difference method by using the numerical solver PROMIS. The Pt-X concentration profiles are adjusted accordingly to the Spreading Resistance Profiles measured on n-type Fz and Cz samples, Pt diffused at 950degreesC for 8 to 168 hours and then cooled at different cooling rates in the range of [1-14]degreesC/min. Simulation results evidence the oxygen as the best candidate to react with platinum, leading to a Pt-O complex formation.