Temperature dependence of MeV heavy ion irradiation-induced viscous flow in SiO2

In-situ wafer curvature measurements were performed to determine the mechanical stress in thermally grown SiO₂ films on Si during 4 MeV Xe ion irradiation at various temperatures in the range from 90 to 575 K. Radiation induced viscous flow is observed and the radiation induced viscosity is determined at various temperatures. It ranges from 2.9 x 10²³ at Pa ion/cm² 90-300 K to 1.6X 10²³ Pa ion/cm² at 500 K. Both its magnitude and temperature dependence can be explained in terms of a phenomenological model in which stress relaxation takes place in locally heated, mesoscopic regions of low viscosity, centered around individual ion tracks. According to this model, stress relaxation occurs in ~ 10 ps and within ~ 3 nm of the ion track.