Formation of bubbles by high dose He implantation in 4H–SiC

Abstract

1.6 MeV He+ ions were implanted at room temperature into (0001)Si n-type 4H–SiC at a dose of 1×1017 cm−2. Cross-section transmission electron microscopy (TEM) and x-ray diffraction (XRD) were used to characterize the induced defects and the strain-induced effects before and after annealing. Infrared reflectivity was also used to localize changes in the microstructure. In the as-implanted samples, the TEM observations show a three layer damaged region consisting of a continuous amorphous layer surrounded with two buried crystalline zones. Bubbles of small diameter are readily formed in the as-implanted state. Only a few changes are observed after a 800 °C-30 min annealing. Voids formation and recrystallization of the amorphous state in different polytypes are observed for a 1500 °C-30 min annealing. Moreover, XRD shows that the dilatation of the c axis of the lattice observed after implantation completely disappears after the high temperature annealing implying the structural recovery of all the crystalline perturbed regions. An analytical study of atomic redistribution processes under ion implantation is also developed by introducing a frequency probability function of relocation between monolayers. The calculated distribution profiles of atoms are compared with the TEM results.