Stresses and radiation damage in Ar⁺ and Ti⁺ ion-implanted silicon

Abstract

Comparative studies of stress and radiation damage in 〈111〉 silicon were carried out after ion implantation with 28-keV Ar+ and 30-keV Ti+ to doses ranging from 1012 to 1017 ions/cm2. The effect of annealing at 600 °C for 2 h was also investigated. Automatic x-ray diffraction measurement of strains in the specimens shows that in the as-implanted condition the stresses are compressive and they increase linearly with ion dose up to about 10 16 ions/cm2, after which they relieve. This behavior was the same for both the "reactive" (Ti) and the "unreactive" (Ar) ion implantation. However, after annealing the stresses in the Ar+ implanted samples remain compressive and those in the samples implanted with Ti+ become tensile. The change from compressive to tensile stresses is associated with titanium-silicide formation. X-ray diffraction patterns show that the silicide consists of metastable and equilibrium phases. Sheet resistance measurements on the samples with a continuous TiSi2 layer show the resistivity to be as low as 14 μΩ cm. Rutherford backscattering channeling studies show radiation damage to increase linearly with ion dose and, in the case of Ar implantation, saturate at doses ≥5×1014 ions/cm2, due to the complete amorphization of the implanted region. A decrease in defect density with dose occurred at doses >5×1015 ions/cm2 for the Ti implantation. Annealing only reduced the damage observed, except for low doses (≤1014 ions/cm 2), where complete recrystallization occurred.