Nitridation induced surface donor layer in silicon and its impact on the characteristics of n- and p-channel MOSFETs

The effects of high-temperature ammonia nitridation on the SiO/sub 2/-Si system have been studied. Unlike previous studies which have focused exclusively on the dielectric properties, this work explores the possible effects on the underlying silicon. Initial results indicate that nitridation introduces nitrogen into the silicon over a depth of approximately 60 nm. Schottky diode and AC surface photovoltage measurements show that the boron-doped nitrogen-rich silicon has n-type characteristics which may be nitrogen-oxygen donor related. The device characteristics of n- and p-MOSFETs using reoxidized nitrided oxide (RONO) gate dielectric are studied. Compared to oxide devices, off-state drain leakage is suppressed in both n- and p-RONO devices. Electron mobility is degraded at low normal field and improved at high normal field, whereas hole mobility degrades at all fields. These unusual characteristics can be qualitatively explained in terms of the formation of nitridation-induced surface donor layer.<>