MECHANISMS FOR POLYCRYSTALLINE SILICON DEFECT PASSIVATION BY HYDROGENATION IN AN ELECTRON-CYCLOTRON-RESONANCE PLASMA

An in-line mass spectrometer and Langmuir probes have been employed to examine mechanisms of plasma immersion hydrogen passivation of grain boundary defects in polycrystalline silicon thin film transistors. Rel ative fluxes of H+ and H-2(+) as well as total ion current density wer e measured at the substrate location in an electron cyclotron resonanc e hydrogen discharge. Measurements were made over a range of operating conditions over which passivation rates have been shown to vary drama tically. Data presented show a strong correlation of both H+ flux and ion bombardment energy with good transistor performance obtained at op erating pressures below 1 mTorr. This suggests that discharge operatin g conditions that promote dissociation of H-2 to form H and H+ (which may diffuse more rapidly through solid material than H-2), as well as increased sheath voltages and therefore ion energy at the substrate, a re important to obtaining acceptable process rates. (C) 1995 American Institute of Physics.