X‐ray irradiation‐induced degradation in Hf 0.5 Zr 0.5 O 2 fully depleted silicon‐on‐insulator n‐type metal oxide semiconductor field‐effect transistors

Abstract The n‐type ultrathin fully depleted silicon‐on‐insulator (FDSOI) metal–oxide–semiconductor field‐effect transistors (MOSFETs), with a Hf 0.5 Zr 0.5 O 2 high dielectric permittivity (high‐ k ) dielectric as gate insulator, were fabricated. The total ionizing dose effects were investigated, and an X‐ray radiation dose up to 1500 krad(Si) was applied for both long‐ and short‐channel devices. The short‐channel devices (0.025–0.100 μm) exhibited less irradiation sensitivity compared with the long‐channel devices (0.35–16 μm), leading to a 71% reduction in the irradiation‐induced drain current growth and a 26% decrease in the shift of the threshold voltage. It was experimentally demonstrated that the OFF mode is the worst case among the three working conditions (OFF, ON and All0) for short‐channel devices. Also, the determined effective electron mobility was enhanced by 38% after X‐ray irradiation, attributed to the different compensations for charges triggered by radiation between the high‐ k dielectric and buried oxide. By extracting the carrier mobility, gate length modulation, and source/drain (S/D) parasitic resistance, the degradation mechanism on X‐ray irradiation was revealed. Finally, the split capacitance–voltage measurements were used to validate the analysis.