Investigation of spatial and energy profiles of plasma process-induced latent defects in Si substrate using capacitance–voltage characteristics

Abstract

Spatial and energy profiles of latent defects in Si substrate created during plasma processes were investigated based on a model prediction framework using capacitance–voltage (C–V) characteristics in combination with experimental results. The C–V curves of metal–oxide–semiconductor (MOS) capacitor were simulated with respect to various spatial and energy profiles of the defects predicted by numerical simulations and experimental surface analyses reported so far. The distortions of C–V curves significantly depend on the defect profiles. As the peak density of defects locates at deeper levels in the Si bandgap, the characteristic hump appears in the depletion region of the C–V curve. The position of the hump moves as the energy profile changes against the depth. We compared the model predictions with experimental results for damaged devices after Ar plasma irradiation. We found the difference in the distortion of C–V curves after an inductively coupled plasma or a capacitively coupled plasma exposures, which implied that the energy profiles significantly depend on plasma conditions. We experimentally revealed that, for a certain plasma process condition, the major portion of defects locates at deep levels in the Si bandgap. The present prediction model is useful for an in-depth understanding the nature of defect creation and controlling plasma process-induced damage to future MOS devices.