A method of preparing a hafnium nitrate thin film includes placing phosphorus
pentoxide
in a first vessel; connecting the first vessel to a second vessel containing hafnium
tetrachloride; cooling the second vessel with liquid nitrogen; dropping fuming
nitric acid into the first vessel producing N2O5 gas; allowing
the N2O5 gas to enter the second vessel; heating the first
vessel until the reaction is substantially complete; disconnecting the two vessels;
removing the second vessel from the liquid nitrogen bath; heating the second vessel;
refluxing the contents of the second vessel; drying the compound in the second
vessel by dynamic pumping; purifying the compound in the second vessel by sublimation
to form Hf(NO3)4, and heating the Hf(NO3)4
to produce HfO2 for use in an ALCVD process.
