NEUTRALIZATION OF BORON IN SILICON BY HIGH-TEMPERATURE BOMBARDMENT WITH ARGON IONS

Layers of p-type Si which were formed on n-type Si were bombarded by 1 35-keV Ar+ ions to doses of 10(15)-10(17) cm2 at 900-degrees-C. The p- type layers had a thickness of 0.7 mum and a boron concentration up to 10(19) cm-3. Secondary-ion mass spectrometry, capacitance measurement s, and layer-by-layer Hall measurements were carried out. The capacita nce measurements were aimed at determining the distribution of charged centers. The onset of a radiation-accelerated redistribution of boron due to diffusion is accompanied by a concentration of the boron towar d the surface. This effect increases with the dose. It is accompanied by an electrical neutralization of acceptors. As the boron concentrati on in the surface region increases to 5 X 10(19) cm-3, the hole concen tration does not exceed 3 X 10(15) cm-3 at depths up to 0.2 mum. The b oron neutralization is preserved during annealing to 1100-degrees-C. T he thermal stability of the neutralization increases with the ion dose , The observed effects are explained on the basis that the radiation g ives rise to structural defects, primarily partial dislocation loops, and that there is a drainage of boron atoms to these defects as a resu lt of the radiative acceleration of diffusion.