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

Abstract

Atomic layer deposition (ALD) of ruthenium metal films is presented using (η4-2,3-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 °C showed a saturative, self-limited behavior at ≥3.0 s for Ru(DMBD)(CO)3 and ≥0.1 s for 1,1-dimethylhydrazine. An ALD window was observed from 200 to 210 °C, with a growth rate of 0.42 Å/cycle. Films grown at 200 °C showed rms surface roughnesses of <1 nm. X-ray photoelectron spectroscopy of a 42 nm thick film grown at 200 °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 °C with 250 cycles. 42 nm thick ruthenium films grown at 200 °C were subjected to annealing studies under hydrogen and ammonia atmospheres at 400 °C, followed by rapid thermal annealing at 600 °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 Å/cycle within a 200–205 °C ALD window, whereas tert-butylamine gave a growth rate of 0.25 Å/cycle at 200 °C.

Reactions of ruthenium cyclopentadienyl precursor in the metal precursor pulse of Ru atomic layer deposition

“…The surface metal oxides are unstable and decompose to give metals at elevated temperatures. 12 For thermal ALD of Ru using dimethylbutadiene-based precursor Ru(DMBD)(CO)3 and non-oxidative reactants hydrazine, the achieved growth rate is 0.42 Å /cycle with an ALD temperature window from 200 °C to 210 °C. 12 In addition to thermal ALD, plasma-enhanced ALD (PE-ALD) has been used with ammonia or a mixture of N2 and H2 as the N-plasma source.…”

“…12 For thermal ALD of Ru using dimethylbutadiene-based precursor Ru(DMBD)(CO)3 and non-oxidative reactants hydrazine, the achieved growth rate is 0.42 Å /cycle with an ALD temperature window from 200 °C to 210 °C. 12 In addition to thermal ALD, plasma-enhanced ALD (PE-ALD) has been used with ammonia or a mixture of N2 and H2 as the N-plasma source. [13][14][15] For the PE-ALD of Ru using RuCp2 and NH3 plasma at a temperature of 300 °C, a growth rate of 1.2 Å/cycle has been reported, while a growth rate of 1.8 Å/cycle was reported using Ru(EtCp)2 at 300 °C.…”

The Importance of Decarbonylation Mechanisms in the Atomic Layer Deposition of High‐Quality Ru Films by Zero‐Oxidation State Ru(DMBD)(CO)3

“…The authors reported a constant GPC of 0.8 Å/cycle at 260-280 °C, with a decrease or increase in GPC with increasing temperature at temperatures above or below the 260-280 °C range, respectively. Cwik et al [43] reported a constant GPC of 0.4 Å/cycle at 200-210 °C and a steadily increasing GPC with increasing temperature both above and below the 200-210 °C range. The counter-reactant in that study was 1,1-dimethylhydrazine.…”

The Importance of Decarbonylation Mechanisms in the Atomic Layer Deposition of High-Quality Ru Films by Zero-Oxidation State Ru(DMBD)(CO)3

“…and (iii) what is the general expected relationship between GPC and temperature for a zero-oxidation state precursor?Recently, several studies have reported the ALD of high-quality Ru films from η 4 -2,3dimethylbutadiene ruthenium tricarbonyl [Ru(DMBD)(CO)3(0)], using either O2 [34,45,48] or various non-oxidative counter-reactants such as H2O or hydrazine. [43,44,49] The studies indicate that this precursor is an exceptional candidate for Ru vapor deposition, as it is volatile and thermally stable, does not suffer from a nucleation delay on SiO2, and yields pure and smooth Ru films at relatively low temperatures. Yet, a closer look at the reported GPC as a function of temperature and counter-reactant in the earlier reports reveals significant discrepancies.…”