Electrical characterization of atomic-layer-deposited hafnium oxide films from hafnium tetrakis(dimethylamide) and water/ozone: Effects of growth temperature, oxygen source, and postdeposition annealing

摘要

The electrical properties of HfO2-based metal–insulator–semiconductor capacitors have been systematically investigated by means of I–V and C–V characteristics, admittance spectroscopy, deep level transient spectroscopy, conductance transient, and flat band voltage transient techniques. Attention is also given to the study of the temperature dependence of the leakage current. HfO2 films were grown on p-type silicon substrates by atomic layer deposition using hafnium tetrakis(dimethylamide) as hafnium precursor, and ozone or water as oxygen precursors. The growth temperature ranged from 150 to 350 °C. Low growth temperatures prevent decomposition and high growth rate, as well as high contamination levels. As a result, the leakage current is lower for lower deposition temperatures. Some of the deposited samples were submitted to a postdeposition annealing at 650 °C in N2 atmosphere, showing a decrease in the leakage current and an increase in the equivalent oxide thickness (EOT), whereas interfacial state density increases and defect density inside the dielectric bulk decreases. Regarding dielectric reliability, in our experimental conditions, HfO2 layers grown at 150 °C exhibit the largest EOT and breakdown voltage. The electrical behaviour is clearly linked with structural properties, and especially with the formation of an interfacial layer between the HfO2 layer and the silicon substrate, as well as with the presence of several impurities.