Temperature behavior and annealing of insulated gate transistors subjected to localized lifetime control by proton implantation

Localized lifetime control by proton implantation can result in a considerable improvement in the trade-off between device turn-off time and forward voltage when compared with the unlocalized method of electron irradiation. After a proton dose of 3 × 10¹¹cm⁻² at 3.1 MeV implanted here into insulated gate transistors, turn-off time is reduced by more than an order of magnitude compared to unimplanted devices. When the implanted devices are operated as high voltage switches at a current of 152 A cm⁻² and at a forward blocking voltage of 400 V, the following increases are observed by increasing device operating temperatures from 20 to 150°C, (a) forward voltage: 2.5 V to 2.7 V; (b) turn-off time: 0.78 μs to 1.23 μs; (c) leakage current: 20 nA to 1 mA. The physical mechanisms responsible for the qualitative temperature dependences are identified: MOS channel resistance for forward voltage, carrier capture cross-section for turn-off time, and generation and diffusion components of leakage current. Since no catastrophic or unrecoverable behavior is observed, normal device operation within the tested temperature range is possible. Isothermal annealing curves of turn-off time measured after annealing, and corresponding to a few hours annealing time, reveal that a constant turn-off time is reached after about an hour. The constant value increases with temperature, but is still below the unimplanted value after 4 h at 525°C. The turn-off time was verified to be constant even after 24 h of annealing at 200°C. Lifetime control by proton implantation seems to be more thermally stable than that caused by electon irradiation.