Time dependent breakdown of ultrathin gate oxide

Time dependent dielectric breakdown (TDDB) of ultrathin gate oxide (<40 /spl Aring/) was measured for a wide range of oxide fields (3.4<|E/sub ox/|<10.3 MV/cm) at various temperatures (100/spl les/T/spl les/342/spl deg/C). It was found that TDDB of ultrathin oxide follows the E model. It was also found that TDDB t/sub 50/ starts deviating from the 1/E model for fields below 7.2 MV/cm. Below 4.8 MV/cm, TDDB t/sub 50/ of intrinsic oxide increased above the value predicted by the E model obtained for fields >4.8 MV/cm. The TDDB activation energy for this type of gate oxide was found to have linear dependence on oxide field. In addition, we found that /spl gamma/ (the field acceleration parameter) decreases with increasing temperature. Furthermore, it was found that testing at high temperatures (up to 342/spl deg/C) and low electric field values did not introduce new gate oxide failure mechanism. It is also shown that TDDB data obtained at very high temperature (342/spl deg/C) and low fields can be used to generate TDDB model at lower temperatures and low fields. Our results (an enthalpy of activation of 1.98 eV and dipole moment of 12.3 e/spl Aring/) are in complete agreement with previous results by McPherson and Mogul. Additionally, it was found that TDDB is exponentially dependent on the gate voltage.