Influence of N2 and NH3 annealing on the nitrogen incorporation and k-value of thin ZrO2 layers

The influence of the annealing atmosphere and temperature on the crystalline phase and composition of thin ZrO2 layers grown by atomic layer deposition on silicon is analyzed. These physical parameters are correlated with the electrical performance of ZrO2 in metal-insulator-semiconductor capacitor structures. For this study, 5.3 nm thick ZrO2 films were annealed at selected temperatures in the range of 400-900 degrees C in either nitrogen or ammonia atmospheres. As shown by grazing-incidence x-ray diffraction, the films start to crystallize at temperatures above 400 degrees C, resulting in a capacitance increase. An annealing in NH3 results in a higher capacitance increase than annealing in N-2. Angular-resolved x-ray photoelectron spectroscopy and secondary ion mass spectrometry show no changes in the chemical composition of ZrO2 after annealing in N-2. In contrast, a significant amount of nitrogen is incorporated into the ZrO2 film and at the ZrO2/Si interface during the temperature treatment in NH3, as also indicated by energy-filtered transmission electron microscopy.