H+ motion in SiO2:: Incompatible results from hydrogen-annealing and radiation models

Two models that incorporate the same mobile H+ entity are the radiation model by McLean [1] and the mobile charge model of hydrogen-annealed oxide by Vanheusden et al. [2]. Mobile charge in hydrogen-annealed silicon-on-insulator (SOI) buried oxides before and after irradiation was studied to investigate discrepancies between the two models. We examined Unibond, low-dose SIMOX, and single- and triple implant standard-dose SIMOX as well as single- and triple-implant SIMOX with supplemental oxygen implantation. To measure H+ motion as fast as 0.01 sec we developed a gate pulse method and combined it with standard I-V techniques to measure the full range of H+ response times. All but single-implant SIMOX exhibit mobile H+ that can be cycled between the Si/SiO2 interfaces without reacting or being trapped. Trapping near the top interface attenuates the cycling of H+ in single-implant SIMOX. The transit H+ times were strongly affected by defects in the oxides and varied by an order of magnitude in oxides with the same thickness. The transit time varied linearly with oxide thickness. The effects of irradiation on the mobile H+ was studied to see if the irradiation would introduce defects that modify the H+ behavior and that bring the two models into agreement. No convergence was observed. After irradiation, H+ could be cycled between the Si/SiO2 interfaces without reacting and its transit time across the oxide was not altered.