New class of Zr precursor containing boratabenzene ligand enabling highly conformal wafer-scale zirconium dioxide thin films through atomic layer deposition

Abstract

This study presents the deposition of zirconium oxide (ZrO2) thin films through atomic layer deposition (ALD) using a novel Zr precursor, tris(dimethylamido) dimethylamidoboratabenzene zirconium [eta(6):eta(1)-(C5H5BNMe2)Zr(IV)(NMe2)(3)] and O2 reactant on SiO2/Si substrate in a range of 150-350 degrees C. The successful growth of highly conformal and amorphous ZrO2 films was possible using O2 as a mild oxygen source, which has rarely been found in ZrO2 ALD. This newly proposed process displayed distinct ALD characteristics, including self-limiting film growth and a linear relationship between the number of ALD cycles and film thickness, and exhibited enhanced deposition temperature window and growth per cycle of 0.87 Ang;, which is higher than those using several previously reported Zr precursors. Extremely conformal film growth with complete step coverage on trenches [aspect ratio of similar to 6.3] and uniformity on a 15 cm large SiO2/Si wafer was realized, which is one of the main highlights. Structural studies reveal a predominant amorphous nature of the as-deposited films and transition into nanocrystalline cubic ZrO2 films annealed at 850 degrees C with improved film properties such as stoichiometry, reduced impurities, which is confirmed by Rutherford backscattering spectrometry, X-ray diffraction, X-ray photoelectron spectroscopy, elastic recoil detection, and secondary ion mass spectrometry analyses. The optical properties of the prepared films were also examined via ellipsometry analysis.