Influences of residual chlorine in CVD-TiN gate electrode on the gate oxide reliability in multiple-thickness oxide technology

Influences of the chemical vapor deposition (CVD)-TiN gate process on gate oxide integrity have been studied, The gate leakage characteristic and reliability of the gate oxide were drastically degraded by 1000 degreesC annealing for thick oxide as compared to for thin oxide. By X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS) analyses, the oxide degradation is confirmed to be due to the formation of a weak spot induced by out-diffusion of residual Cl from the TIN gate electrode into the gate oxide. Out-diffused Cl reacts with defects in the oxide during the high-temperature anneal and forms trap sites. The weak spot which acts as a leakage path appears to be the local spot which has a larger amount of Cl-related trap sites. Controlling of impurities in the CVD metal gate is a key for realizing future multiple-thickness gate oxide technology.