Mechanical strain and damage in Si implanted with O and N ions at elevated temperatures : evidence of ion beam induced annealing

Abstract

The accumulation of damage and the development of mechanical strain in crystalline Si (c-Si) by O and N ion implantation to doses up to 431017 cm-² at elevated temperatures have been studied using Rutherford backscattering spectrometry and high resolution x-ray diffraction. The implantation of O or N ions at high temperatures produces two distinct layers in the implanted c-Si: (i) a practically damage-free layer extending from the surface up to ~- half of the depth of the mean projected range (Rp) and presenting negative strain (of contraction); and (ii) a heavily damaged layer located around and ahead of the Rp with no significant strain. Both the damage distribution and the magnitude of the strain were found to be dependent on the ion species implanted. We proposed that besides the spatial separation of Frenkel pair defects due to the mechanics of the collision processes and the intensive dynamic annealing, an ion beam induced annealing process also participate in the formation of the near-surface damage-free layer during high temperature implantation of c-Si.