LATENT THERMALLY ACTIVATED INTERFACE-TRAP GENERATION IN MOS DEVICES

A large increase in interface-trap density (up to a factor of 5) has been observed in commercial MOS devices at very long times after irradiation (> 10(6) s). This "latent" buildup occurs after an initial apparent saturation of interface-trap density, which occurs typically within approximately 10(2)-10(4) s after irradiation. The latent buildup is thermally activated, with an activation energy of approximately 0.47 eV. Within experimental uncertainty, this is equal to the activation energy (approximately 0.45 eV) for the diffusion of molecular hydrogen in bulk fused silica. Latent interface-trap buildup can degrade the performance of devices in low-dose-rate radiation environments (e.g., space).