LATENT THERMALLY ACTIVATED INTERFACE-TRAP GENERATION IN MOS DEVICES

A large increase in interface-trap density (up to a factor of 5) has b een observed in commercial MOS devices at very long times after irradi ation (> 10(6) s). This "latent" buildup occurs after an initial appar ent saturation of interface-trap density, which occurs typically withi n 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 e nergy (approximately 0.45 eV) for the diffusion of molecular hydrogen in bulk fused silica. Latent interface-trap buildup can degrade the pe rformance of devices in low-dose-rate radiation environments (e.g., sp ace).