Helium implantation in silicon: the effects of implantation temperature

Thermal helium desorption spectrometry (THDS) was used to study the effects of implantation temperature on bubble formation in helium implanted silicon at 5×1016 cm−2 with 50 keV, from RT to 800 °C. Both isochronal and partial annealing schemes have been used and have allowed to raise important process and behaviour. Helium release from bubbles/cavities in silicon is well described by the permeation from cavities to the surface. Entropy effects play a major role in the helium desorption from bubbles. Partial desorption results show that the release of helium by permeation from bubbles/cavities to the surface has an activation energy of 1.8 eV whatever the implantation temperature may be, but also whatever the implantation energy may be. These results are discussed in highlight of the transmission electron microscopy (TEM) observations. As for example, an implantation temperature of 600 °C is needed to create cavities empty of gases. However, with increasing temperature more and more extended defects are formed. Finally at 800 °C, no cavities or bubbles are created but only extended defects.