Reliability of Thin Gate Oxides Irradiated under X-Ray Lithography Conditions

The effect of X-ray lithography (XRL) process on the reliability of thin gate oxide has been investigated. A large increase in the low-field excess leakage current was observed on irradiated oxides, which was very similar to the electrical stress-induced leakage currents. However, it has been found that the long-term reliability of ultra-thin gate oxide is not affected by XRL process. The excess leakage current could be eliminated by thermal annealing at 400°C and above and no residual damages in the oxide were observed after the annealing.