Time dependent breakdown of ultrathin gate oxide

Time dependent dielectric breakdown (TDDB) of ultrathin gate oxide (<40 Ang strom) was measured for a wide range of oxide fields (3.4 < \E-ox\ < 10.3 M V/cm) at various temperatures (100 less than or equal to T less than or equ al to 342 degrees C). It was found that TDDB of ultrathin oxide follows the E model. It was also found that TDDB t(50) starts deviating from the 1/E m odel for fields below 7.2 MV/cm. Below 4.8 MV/cm, TDDB t(50) of intrinsic o xide 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 fou nd to have linear dependence on oxide field. In addition, we found that gam ma (the field acceleration parameter) decreases with increasing temperature . Furthermore, It was found that testing at high temperatures (up to 342 de grees C) and low electric field values did not introduce new gate oxide fai lure mechanism. It is also shown that TDDB data obtained at very high tempe rature (342 degrees 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 Angstrom) are in complete agreement with previous results by McPherson and Mogul. Additionally, it was found th at TDDB is exponentially dependent on the gate voltage.