Cavity formation in helium-implanted silicon - Temperature dependence

The formation of cavities by helium implantation into silicon has been studied as function of the implantation temperature using both helium desorption spectroscopy and transmission electron microscopy. Helium desorption reveals overpressurized bubbles for implant temperature up to 550degreesC. Above, less than 0.05% of implanted helium atoms are found to be retained in the sample. For room temperature implant helium is also found to be released from helium-complexes. These results are confirmed by the transmission electron observations. Three different regimes depending on the implant temperature are observed both in helium retained in the sample and in cavity characteristics. However, release of helium from bubbles is governed by single mechanism of activation energy equal to 1.8 eV whatever the implant temperature may be.