Cavities in He-Implanted SiC

摘要

Helium implantation has been examined to form stable cavities in 4H- and 6H-SiC. At room temperature implantation with 2x10~(16) He/cm~2 at 1.3 MeV only prismatic loops of about 10nm in diameter and lying in the basal plane (0001) are observed. However, large perturbed zones have been observed on each sides. At higher dose, 10~(17) He/cm~2, small bubbles are readily formed but the implantation also leads to amorphization. A three layers structure is observed: an amorphous region surrounded by crystalline zones of point defects. When annealing at sufficiently high temperature (1500℃), bubbles grow and the complete structural recovery is obtained. However, crystallization takes also place during high temperature annealing and polytypisme transitions are observed. Implantation of Helium (50keV, 10~(17)cm~(-2)) at 750℃ avoids the amorphous state and only one layer structure including small bubbles is observed. Desorption of helium from keV implanted 6H-SiC shows two peaks corresponding to two helium associated defects.