Atomic layer deposition of insulating hafnium and zirconium nitrides

Highly uniform, smooth, and conformal coatings of higher nitrides of hafnium and zirconium were produced by atomic layer deposition from homoleptic tetrakis(dialkylamido)metal(IV) complexes and ammonia at low substrate temperatures (150-250 degreesC). The precursor vapors were alternately pulsed into a heated reactor, yielding 1.15-1.20 Angstrom of metal nitride film for every cycle. Successful depositions were carried out on silicon, glass, quartz, and glassy carbon. All of the films showed good adhesion to the substrates, were chemically resistant, and did not oxidize over time. The films were characterized by Rutherford backscattering spectrometry and ellipsometry. These films were amorphous as deposited, as shown by X-ray diffraction and transmission electron microscopy. Step coverage is 100% in vias with an aspect ratio of 40:1, as determined by scanning electron microscopy. Evidence is given for the existence of nitrogen-rich phases with compositions Hf3N4 and Zr3N4. These two materials are insulating, transparent, and colored, in contrast to the well-known mononitrides, which are shiny, gold-colored, and highly conducting.