Selective lifetime doping in silicon by laser scanning

Q-switched green laser-beam scanning has been investigated as a new approach for lifetime doping in silicon. The effects of the laser-beam scanning have been studied by p-n junction photoresponse, MOS CV lifetime measurements, and p-n junction leakage measurements. The results indicate there is a range of average laser power (0.5-0.8 mW under certain scanning conditions) over which minority-carrier lifetime decreases at least 3 orders of magnitude. The depth within which minority-carrier lifetime changes significantly is more than 0.4 µm. Also the doping may be accomplished without disturbing passivation and with no visible damage. Furthermore, the lifetime changes are shown to be stable for subsequent thermal processing up to 400°C.