Relationship between mobility and residual-mechanical-stress as measured by Raman spectroscopy for nitrided-oxide-gate MOSFETs

The cause of unusual transconductance behavior in MISFETs with nitrided oxide gate insulator films was studied. In particular, the effect of mechanical stress induced by nitrided-oxide films on the transconductance was investigated. The residual mechanical stress in nitrided oxide films was evaluated by Raman spectroscopy and by two-dimensional mechanical stress simulation. It was found that, with higher interfacial nitrogen concentration, the tensile stress rises at the silicon and the gate insulator interface. The transconductance dependence on the mechanical stress was measured by deforming the wafer. All the results suggest that residual tensile stress is one of the causes of the transconductance behavior.<>