High-temperature ion implantation in silicon

Abstract

The properties of silicon implanted with various doping and inert gas ions at target temperatures Ti from 600 to 1100°C are reviewed. Ion mass and T1 are the main factors governing the behaviour of lattice defects and impurity atoms. The observed residual damage is the result of decomposition of the supersaturated solid solution of point defects. Transition from the homogeneous to heterogeneous nucleation of the stable damage (extrinsic dislocation loops) occurs with the increase of the ion mass due to increasing probability to form loop nuclei within more dense displacement spikes. Heterogeneous nucleation leads to the formation of a large number of stable faulted loops in the region of maximal elastic losses. Homogeneous nucleation results in the growth of coarse perfect dislocation loops penetrating deeper than 1 μm. Their formation may be prevented by heating the target over 900°C. Dislocation loops are suggested to be the reason for incomplete electrical activity of the implanted dopants both for the “hot” and the “cold” implantation followed by annealing, provided the temperatures in both cases are higher than 800°C. The excess of mobile point defects causes an impurity diffusion enhancement which becomes observable at Ti > 700°C. Retrograde temperature dependence of the dopant diffusivity and the occurence of up-hill diffusion are noted at very high T1.