Effects of carbon residue in atomic layer deposited HfO2 films on their time-dependent dielectric breakdown reliability

The effect of the carbon residue on the reliability of HfO2 thin films was investigated. HfO2 films were deposited on Si wafers by atomic layer deposition at a wafer temperature of 250°C using Hf[N(CH3)2]4 and O3 oxidant with two different densities (160 and 390g∕m3). The films deposited at the higher O3 density contained a lower concentration of carbon impurities. The leakage current density was lower and the time-dependent dielectric breakdown was improved in the higher O3 density films. First principles calculations confirmed that trap sites were generated in the band gap of HfO2 when carbon was interstitially or substitutionally present.