Temperature dependence of gate current in ultra thin SiO2 in direct-tunneling regime

In this paper, we examine the temperature dependence of gate current in the direct tunneling regime in ultra thin oxide MOS capacitors under positive and negative gate bias. It was found that for temperature above ~348 K and low fields, the gate current is exponentially dependent on 1/T. In this temperature range, it was found that gate current is dominated by a thermionic-type of emission current. However, below ~348 K, the gate current is weakly dependent on temperature and is dominated by field activated direct tunneling. This finding holds for PMOS and NMOS devices operating in accumulation and inversion. The activation energies for the thermionic-type emission for different gate voltage conditions were determined from the Arrhenius plots to be between 0.64 eV and 0.84 eV for PMOS and between 0.73 eV and 0.82 eV for NMOS. It was also found that the activation energy decreases with increasing gate voltage. In addition, it was found that the activation energy is lower for injection from p-type electrodes than that for injection from n-type electrodes