Gate oxide integrity of NMOS transistor arrays

The time-dependent dielectric breakdown (TDDB) of the channel oxide on n-channel MOS 1000-transistor arrays was investigated as a function of voltage stress on the gate and transistor temperature. The gate oxide is 25 nm thick. The field acceleration factor derived from the TDDB measurements is a linear function of the reciprocal temperature, in agreement with a thermodynamic model proposed by McPherson and Baglee. The thermal activation energy is a function of the temperature and consequently is not described by a simple Arrhenius equation. The field acceleration factor and effective temperature acceleration factor, as determined by the measurements, are used to project failure rates which are many orders of magnitude less than one failure in 10
⁹
h for 10-V 55°C operation of the 1000- transistor array.