Sol-Gel Synthesis of High-k HfO2 Thin Films

HfO2 films were prepared using alkoxy-derived precursor solutions. The effects of the chemical composition of precursor solutions on the microstructure development were investigated for HfO2 films on Si substrates. The microstructure distinguished developed in the HfO2 films prepared using the precursor solutions with and without diethanolamine. This result is considered to be due to the difference in the progress of organic decomposition and the behavior of nucleation and grain growth. The flatness and refractive index of the HfO2 films were improved using diethanolamine-added solution. The refractive index and the dielectric constant of the HfO2 film prepared at 400 degrees C using a diethanolamine-added solution were about 1.85 and 17, respectively. A similar microstructure developed in the HfO2 films on polyimide films. Much flat and uniform HfO2 films are expected for application to integrated optical devices.