The effect of junction fringing field on radiation-induced leakage current in oxide isolation structures and nonuniform damage near the channel edges in MOSFETs

A significant contribution of fringing field effect on radiation-induced leakage current in oxide isolation structure and damage nonuniformity in MOSFET was demonstrated using analytical expressions for electrical field. A two dimensional analytical model describing electrical field distribution in oxide isolation and MOSFET structures was elaborated to provide the dynamics of positive oxide trapped charge build-up process. The leakage current at the bottom of the recessed field oxide calculation was performed using oxide trapped charge density profile obtained through charge build-up process simulated applying electrical field model to changing conditions during irradiation process. Calculations are presented for leakage current versus dose dependencies for different structure dimensions and irradiation conditions; leakage current versus voltage shift of buried layer during irradiation and P/sup +/-channel stop region doping level; and I-V characteristics of parasitic transistor. Experimental data concerning damage nonuniformity are discussed together with calculated data for electrical field pattern and nonuniformity length in MOSFETs.<
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