Synthesis and characterization of hafnium oxide and hafnium aluminate ultra-thin films by a sol–gel spin coating process for microelectronic applications

Currently there are intense industry-wide efforts in searching for new high dielectric constant (high-k) materials for use in future generations of ultra-large scale integrated circuits (ULSI). There are number of requirements for the new high-k materials, such as high dielectric constant, thermal stability (400 °C or higher), high mechanical strength, and good adhesion to neighboring layers. Oxide spinels comprise a very large group of structurally related compounds many of which are of considerable technological significance. Spinels exhibit a wide range of electronic and magnetic properties in particular nickel, hafnium, cobalt, containing spinels. In the present investigation, crack free, dense polycrystalline monoclinic structure of pure HfO2, and Al2HfO5 ultra-thin films have been prepared by a simple and cost effective sol–gel spin coating method. The formation of the monoclinic HfO2 phase at 600 °C and complete formation of the single phase Al2HfO5 at 800 °C has been reported. The composition of the annealed films has been measured and found to be 70 at.% of O, 30 at.% of Hf for HfO2 and 22 at.% of Al, 12 at.% of Hf and 66 at.% of O for Al2HfO5 films, which are close to the stoichiometry of the HfO2 and Al2HfO5 thin films.