Chemistry of inorganic compounds – Nitrogen or compound thereof – Oxygen containing
Reexamination Certificate
2005-05-31
2005-05-31
Langel, Wayne A. (Department: 1754)
Chemistry of inorganic compounds
Nitrogen or compound thereof
Oxygen containing
C423S608000
Reexamination Certificate
active
06899858
ABSTRACT:
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 N2O5gas; allowing the N2O5gas 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)4to produce HfO2for use in an ALCVD process.
REFERENCES:
patent: 5039502 (1991-08-01), Horn et al.
patent: 6468494 (2002-10-01), Nappier et al.
Field et al.,Tetranitratozirconium(IV)A New Volatile Compound, Proc. Chem. Soc. 1962. pp 76-77, no month.
Evans David R.
Hsu Sheng Teng
Zhuang Wei-Wei
Curtin Joseph P.
Langel Wayne A.
Rabdau Matthew D.
Ripma David C.
Sharp Laboratories of America Inc.
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