Graded tunnelling barrier and oxygen concentration in thermally grown ultrathin SiO_<i>x</i>gate oxide

Abstract

Barrier parameters of a thermally grown SiOx gate oxide are derived by relating the SIMS oxygen concentration profile to the barrier height. Even in the simple analytical form such a graded barrier model agrees with the tunnelling current and its voltage dependence in both directions. Asymmetrical tunnelling I?Vs in the symmetrical n+Si?SiOx?n+Si structure are due to both graded barrier and penetration of carriers into the gate oxide at the SiOx?Si substrate interface.