Hydrogen effects on a-SiO2: a photoemission study

Negative bias stress experiments on a-Si:H/a-SiO2 Thin Film Transistors show that the instability is predominantly related to charge injection in the gate insulator. We propose that charge injection is occurring in a defected region of the gate insulator adjacent to a-Si'H, caused by the effect of activated hydrogen on a-SiO2 surface during deposition. To investigate the hydrogen influence, we have studied low-energy (100 eV) hydrogen-ion and Ar-ion bombardment effects on a-SiO2 using synchrotron radiation photoemission spectroscopies. Comparing the two kind of treatments, we show that hydrogen treatment produces predominantly Si-H defects, which are observed to induce gap states in a-SiO2.