Densification, anisotropic deformation, and plastic flow of SiO2 during MeV heavy ion irradiation
The response of SiO2 thin films and implantation masks to 4.0 MeV Xe irradiation is studied. Trenches in silica deform dramatically after irradiation with 3X1015 ions/cm2. In situ wafer curvature measurements show that thin planar silica films first densify by 3.6% during irradiation. The resulting stress then relaxes viscously by radiation-enhanced Newtonian flow. At a flux of 3X1010 Xe ions/cm2s the measured shear viscosity was 6X1013Pa s. We find evidence that an irradiation induced anisotropic deformation mechanism is present in the silica films. In equilibrium, this deformation leads to an average compressive saturation stress as large as 4.5X107 Pa.
