Reliability Study of Plasma Etching Damage in ULSI Process

Abstract

ABSTRACTPlasma etching can cause damage in gate oxide during ULSI processing. The damage in the oxide is believed to arise through a high field induced stress current. However, there is another type of damage which is due to ion and photon bombardment on the edge of poly-Si gate during the plasma etching. These two damage mechanisms impose different reliability problems. One is hot-carrier(HC) stress and the other is Fowler-Nordheim(F-N) stress. MOS devices with special test structures to assess plasma process damage were fabricated using 0.35 μm CMOS technology. The devices with different poly gate antennas and etching through different poly-Si gate etching conditions were studied using SEM and various electrical techniques. It was found that oxide charging damaged device is more susceptible to F-N type of stress while ion and photon bombardment damaged device is more susceptible to HC type of stress.