High quality, stoichiometric thin films of hafnium diboride are deposited by chemical vapor deposition from the precursor Hf[BH4](4) at deposition temperatures as low as 200 degrees C. An activation energy of 0.43 eV(41 kJ/mol) is obtained for the overall process as monitored by temperature programmed reaction studies. Films deposited at low temperatures (< 500 degrees C) are structurally amorphous to x-ray diffraction; a 12 nm thick film is sufficient to prevent copper diffusion into silicon during a 600 degrees C anneal for 30 min. Films deposited above 500 degrees C are crystalline, but have a columnar microstructure with low density. All the films are metallic, but the low temperature amorphous films have the lowest resistivity similar to 440 mu Omega cm. The process is also highly conformal, e.g., a 65 nm wide trench with a 19:1 depth-width aspect ratio was coated uniformly. (c) 2005 American Vacuum Society.