Increase of parasitic resistance of shallow p+ extension with SiN sidewall process by hydrogen passivation of boron and its improvement by preamorphization for sub-0.25 /spl mu/m pMOSFETs

With decreasing implantation energy of BF/sub 2/ lower than 10 keV, anomalously low activation efficiency as low as 15% in p+ source/drain extension of pMOSFETs is observed when SiN gate sidewalls are used. It is demonstrated that hydrogen from the SiN film diffuses into the p+ extension, and passivates boron acceptor. Significant decrease of activation efficiency with reducing BF/sub 2/ implantation energy indicates that decrease of amorphization rate at the extension implantation is the origin of low activation efficiency. In sub-0.25 /spl mu/m era, the extra amorphization step is indispensable to suppress hydrogen passivation of boron for achieving low parasitic resistance of pMOSFETs.