Influence of the applied cooling rate on the type conversion of platinum diffused n-type silicon

In this work we show that the temperature and the applied cooling rate duri ng a platinum diffusion process strongly influence the electrical conductiv ity in weakly phosphorus doped silicon. Diffusions were done in the range o f 800-950 degreesC for several hours. Spreading resistance profile analyses clearly show an n-type to p-type conversion under the surface when samples are slowly cooled (5 degreesC/min). Only a compensation of the phosphorus donors is observed when samples are quenched. This mechanism is reversible. Five Pt related deep levels, including the acceptor level at 0.23 eV from the conduction band, are observed. One of them is located at 0.427 eV from the valence band and can be related to the acceptor state at the origin of the type conversion mechanism. This acceptor state can be associated with a complex defect based on the association of a substitutional Pt atom with i nterstitial atoms (Pt, O) or intrinsic point defects.