Estimation of interface roughness using tunneling current in ultrathin MOSFET

Interface roughness effects on tunneling current in ultrathin MOS structures are investigated theoretically. The roughness at SiO₂/Si interface is described in terms of Gauss distribution. It is shown that the effects of rough surface on tunneling current can not be neglected while tunneling occurs. The effect of rms (root-mean-square) roughness on the direct tunneling current decreases with the applied voltage increase and increases with rms roughness increase and the effects increase exponentially with oxide thickness or applied voltage decrease. The applied voltage shift at the extreme of current oscillations increases linearly with SiO₂/Si interface roughness increase. The amplitudes of current oscillations in ultrathin gate oxides are shown to decrease with SiO₂/Si interface roughness increase. The factor of attenuation amplitudes increases exponentially with SiO₂/Si interface roughness increase. This means that this shift may be used to obtain the information about the interface roughness as an inexpensive and simple tool.