Thermal Decomposition of Hafnium Ethoxide-Mollecular Precursor for Hafnia Dielectric Thin Films

Abstract

The HfO₂ thin-film is a very promising gate dielectric material for last generation transistors. The paper presents the thermal decomposition of hafnium ethoxide used as molecular precursor for obtaining hafnia thin films. The investigated molecular precursor is a mixture of Hf₃O(OC₂H₅)₁₀ and Hf₄O(OC₂H₅)₁₄ moisture sensitive amorphous powder.
The thermal decomposition of hafnium ethoxide precursor was investigated by TG-DTG-DSC analysis from room temperature to 600 ^oC in nitrogen atmosphere at 5 K/min. The composition of gas products resulted during pyrolytic decomposition has been studied by Fourier Transformation Infrared Spectroscopy (FTIR) and Mass Spectroscopy (MS). In the gas products, hydrogen, methyl, ethyl, vinyl, hydroxyl groups, acetic aldehyde and acetylene were identified. From mass spectroscopy and FTIR data results that the loss of ethoxy groups from the molecular precursor occurs in the decomposition steps between 200 and 375 ^oC. That suggests that in different steps, ligands from different coordination spheres are lost.