Physical origin of suppressed effective work function modulation at boron segregated NiSi∕SiON interface

In order to elucidate influences of nitrogen on the change of effective work function (ΔΦeff) with impurity segregation, we systematically investigated the ΔΦeff at arsenic (As) and boron (B) segregated NiSi∕SiO2 and NiSi∕SiON interfaces. These impurities are introduced to NiSi∕SiON (SiO2) interfaces by using the conventional predoping process. It was found that increase in Φeff with B segregation is suppressed as low as ΔΦeff=+0.05eV at NiSi∕SiON interface compared to ΔΦeff=+0.14eV at NiSi∕SiO2 interface, though there is little change in decrease of Φeff with As segregation. Moreover, the opposite (negative) Φeff modulation occurred at NiSi∕SiON interface in the case of low B dose. We also performed the B postdoping process, in which B atoms were introduced after Ni silicide gate formation with lower thermal process (∼500°C) than conventional predoping process (∼1000°C). A large ΔΦeff of +0.2eV occurred even at NiSi∕SiON system in the postdoping process. Based on the results of backside x-ray photoelectr...