Water effect in the synthesis of nanostructured thin films of HfO2 deposited by the ultrasonic spray pyrolysis technique

Abstract

HfO2 thin films are proposed as high-k gate dielectric, especially for the fabrication of ultra-large-scale integration systems. The effect of adding deionized water during the synthesis of HfO2 thin films on its structural and dielectric properties is reported. The study of nanostructured HfO2 thin films deposited on crystalline silicon wafers is made by applying the ultrasonic spray pyrolysis (USP) technique. For the synthesis of hafnium oxide thin films, hafnium acetylacetonate was dissolved in dimethylformamide as a hafnium source material. Varying the substrate temperature from 400 and up to 550 °C in increments of 50 °C and adding deionized water during the process, favoring films with well-defined monoclinic well as polycrystalline structures. The thin films presented a nanostructured morphology and a rugosity with a minimum value of 0.45 nm. Refractive index values between 1.87 and 2.02 have been obtained with an average thickness of ~ 21 nm. The carbon and O-H binds decrease considerably, adding deionized water to the deposit. The electrical characterization revealed that the films deposited with deionized water have a high dielectric constant with a maximum value of 14.4, demonstrating that this addition during deposition allows thinner films with good dielectric properties.