CHEMICAL VAPOR-DEPOSITION OF TITANIUM, ZIRCONIUM, AND HAFNIUM NITRIDE THIN-FILMS

Titanium, zirconium, and hafnium nitride thin films were synthesized from tetrakis(dialkylamido)metal(IV) complexes and ammonia by atmospheric pressure chemical vapor deposition with high growth rates at low substrate temperatures (200-450-degrees-C). Depositions were successfully carried out on silicon, low-sodium glass, soda lime glass, vitreous carbon, and boron substrates. Stainless steel and polyester were also used as substrates for depositions of titanium nitride below 250-degrees-C. All of the films showed good adhesion to the substrates and were chemically resistant. The films were characterized by Rutherford backscattering spectrometry, X-ray photoelectron spectroscopy, ellipsometry, and transmission electron microscopy. Reflectance and transmission spectra were also recorded. Hydrogen in the films was estimated by hydrogen forward recoil scattering spectrometry. The titanium nitride coatings were slightly nitrogen-rich TiN (N/M ratio 1.05-1.15). These films displayed metallic properties and were crystalline as deposited. The zirconium and hafnium nitride films were Zr3N4 and nitrogen-rich Hf3N4 (N/M ratios 1.35 +/- 0.05 and 1.7 +/- 0.1, respectively). They were crystalline, yellow-colored, transparent, and insulating. The hydrogen content of the films diminished as the deposition temperature increased. For depositions carried out at 400-degrees-C the TiN films contained 9 atom % hydrogen and at 300-degrees-C the Zr3N4 and Hf3N4 films contained 10 and 16 atom % hydrogen, respectively. The hydrogen is proposed to be incorporated in the films as NH and NH2 groups in the amorphous portion of a mix composed of amorphous material and imbedded nitride crystallites.