Effects of isochronal annealing and irradiation temperature on radiation-induced trapped charge

Radiation-induced trapped charge densities in 45-nm radiation-hardened oxides are estimated via capacitance-voltage (C-V) and thermally stimulated current (TSC) techniques as functions of irradiation and/or isochronal anneal temperature. Reductions in trapped-hole charge were greater for -10 V and 0 V isochronal anneals than for 10 V anneals. This is attributed to enhanced electron-hole dipole pairing during positive-bias anneal. Between 22°C and 125°C, the trapped electron charge increases for 10 V isochronal anneals, and is approximately constant for 0 V and -10 V anneals. Interface-trap charge decreases for 0 V isochronal annealing above 80°C, and ±10 V annealing above 100°C. Elevated temperature irradiation at 10 V shows similar trends to 10 V isochronal anneals. Trapped-hole energy scales derived from C-V measurements for positive or zero bias isochronal anneals are found to be inaccurate, due to the different temperature dependencies of trapped-hole annealing and trapped-electron buildup. Refined estimates of trapped-hole attempt-to-escape frequency are obtained via TSC. Isochronal annealing and elevated temperature irradiation techniques generally cannot be used for hardness assurance testing unless the results are “calibrated” to the low-rate irradiation or long-term annealing response for a given technology