EFFECT OF JUNCTION FRINGING FIELD ON RADIATION-INDUCED LEAKAGE CURRENT IN OXIDE ISOLATION STRUCTURES AND NONUNIFORM DAMAGE NEAR THE CHANNELEDGES IN MOSFETS

A significant contribution of fringing field effect on radiation-induc ed leakage current in oxide isolation structure and damage nonuniformi ty in MOSFET was demonstrated using analytical expressions for electri cal field. A two dimensional analytical model describing electrical fi eld distribution in oxide isolation and MOSFET structures was elaborat ed to provide the dynamics of positive oxide trapped charge build-up p rocess. The leakage current at the bottom of the recessed field oxide calculation was performed using oxide trapped charge density profile o btained through charge build-up process simulated applying electrical field model to changing conditions during irradiation process. Calcula tions are presented for leakage current versus dose dependencies for d ifferent structure dimensions and irradiation conditions; leakage curr ent versus voltage shift of buried layer during irradiation ana P+-cha nnel stop region doping level; and I-V characteristics of parasitic tr ansistor. Experimental data concerning damage nonuniformity are discus sed together with calculated data for electrical field pattern and non uniformity length in MOSFETs.