Thermal atomic layer deposition of ruthenium metal thin films using nonoxidative coreactants

Atomic layer deposition (ALD) of ruthenium metal films is presented using (eta(4)-2,3-dimethylbutadiene)(tricarbonyl)ruthenium [Ru(DMBD)(CO)(3)] with the coreactants 1,1-dimethylhydrazine, hydrazine, or tert-butylamine. The dependence of growth rate on precursor pulse lengths at 200 degrees C showed a saturative, self-limited behavior at >= 3.0s for Ru(DMBD)(CO)(3) and >= 0.1s for 1,1-dimethylhydrazine. An ALD window was observed from 200 to 210 degrees C, with a growth rate of 0.42 angstrom/cycle. Films grown at 200 degrees C showed rms surface roughnesses of <1nm. X-ray photoelectron spectroscopy of a 42nm thick film grown at 200 degrees C revealed 90.6% ruthenium, 7.0% nitrogen, and 2.0% oxygen. Ruthenium films were deposited on patterned substrates with TiN surfaces using various treatments at 200 degrees C with 250 cycles. 42nm thick ruthenium films grown at 200 degrees C were subjected to annealing studies under hydrogen and ammonia atmospheres at 400 degrees C, followed by rapid thermal annealing at 600 degrees C. These annealing procedures led to higher purity, more crystalline, and lower resistivity ruthenium films. The coreactants hydrazine and tert-butylamine were evaluated in ruthenium ALD trials using Ru(DMBD)(CO)(3). Hydrazine gave a growth rate of 0.42 angstrom/cycle within a 200-205 degrees C ALD window, whereas tert-butylamine gave a growth rate of 0.25 angstrom/cycle at 200 degrees C.