In-line control of Si loss after post ion implantation strip

Spectroscopic ellipsometry could be used as a fast and accurate method to measure Si loss resulting from post ion implantation strip. It was found that upon implantation, even at low energies (around 1 keV), the implanted layer has different optical properties from the crystalline Si. That allows ellipsometry to distinguish between Si substrate, implanted Si and SiO2 on top. The ellipsometric measurements are confirmed by transmission electron microscopy (TEM). TEM shows that even if the Si is not amorphized at low energies, it is damaged (the lattice is strained) which is apparently enough to change the optical properties of Si. The exposure of implanted Si to an ash plasma at elevated temperatures (280 °C) results in SiO2 growth and a decrease of the damaged Si thickness. The decrease is attributed partially to oxidation (Si loss) and partially to restoration of the strained lattice.