Localized lifetime control in insulated-gate transistors by proton implantation

The application of localized carrier lifetime control to power devices is explored. A new type of power device, the insulated-gate transistor, was chosen for this study. Proton implantation was used as an agent of lifetime control by varying energy (1 to 3.8 MeV) and dose. Most of the proton damage in silicon, and therefore most of the lifetime reduction, occurs near the proton end-of-range, resulting in a localized band of low lifetime. Proton energy determines the depth at which the region of minimum lifetime is placed within the device structure. The effect of localized lifetime reduction on forward voltage, turn-off time, and leakage current was studied. The results lead to an understanding of the proper choice of depth at which to place a region of low lifetime, and illustrate the advantages of localization. With this choice, a significantly better tradeoff curve of forward voltage versus turn-off time is shown to be realized with proton implantation compared to the unlocalized but common technique of electron irradiation.