Atomic layer deposition of cobalt silicide (CoSi2) thin films on H-terminated Si(111) surfaces, using the cobalt-based precursor tertiarybutylallylcobalttricarbonyl (tBu-AllylCo(CO)3) and trisilane, is investigated by in situ Fourier transform infrared spectroscopy (FTIR) and ex situ X-ray photoelectron spectroscopy (XPS) to uncover the film growth mechanisms. The strong reactivity of tBu-AllylCo(CO)3 with H-terminated silicon surfaces and inertness with silicon oxide surfaces, as previously determined by IR spectroscopy [Chem. Mater. 2012, 24, 1025], opens the door for selective deposition. Deposition of CoSi2 is observed after a brief nucleation period (∼3 cycles), during which the stabilization of the cobalt precursor takes place, as evidenced by a shift of the stretch frequency of the carbonyl groups bonded to the Co center from 2010 to 1980 cm–1. This shift is evidence for completion of the catalytic reaction and leads to a surface termination and configuration that is favorable for subsequent ligand exchange with trisilane, fostering a classical ligand-exchange ALD growth. In steady state, the CoSi2 growth rate is 0.15 ± 0.05 Å per cycle, as measured by Rutherford backscattering spectroscopy (RBS). XPS measurements with depth profiling indicate that the CoSi2 film is stoichiometric with negligible carbon contamination.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
The growth of rhenium nitride and rhenium metal thin films is presented using atomic layer deposition (ALD) with the precursors methyltrioxorhenium and 1,1-dimethylhydrazine. Saturative, self-limiting growth was determined at 340 °C for pulse times of ≥4.0 s for methyltrioxorhenium and ≥0.1 s for 1,1-dimethylhydrazine. An ALD window was observed from 340 to 350 °C with a growth rate of about 0.60 Å per cycle. Films grown at 340 °C revealed a root mean square surface roughness of 2.7 nm for a 70 nm thick film and possessed a composition of ReN0.14 with low O and C content of 1.6 and 2.6 at%, respectively. Enhanced nucleation on in situ grown TiN, relative to thermal SiO2, enabled a conformality of 98% on high aspect ratio trenched structures. Subjecting the ReN0.14 thin films to thermal or chemical and thermal treatments reduced the nitrogen content to ≤1.6 at%, yielding a film purity of about 96 at% rhenium and resistivities as low as 51 μΩ cm. The Re metal film thicknesses on the trenched structures remained intact during the post-deposition annealing treatments and the films did not delaminate from the substrate surfaces.
The atomic layer deposition of copper metal thin films was achieved using a three precursor sequence entailing Cu(OCHMeCH2NMe2)2, formic acid, and hydrazine. A constant growth rate of 0.47−0.50 Å/cycle was observed at growth temperatures between 100 and 170 °C. The resulting films are high purity and have low resistivities.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Molybdenum trioxide films have been deposited using thermal atomic layer deposition techniques with bis(tert-butylimido)bis(dimethylamido)molybdenum. Films were deposited at temperatures from 100 to 300 °C using ozone as the oxidant for the process. The Mo precursor was evaluated for thermal stability and volatility using thermogravimetric analysis and static vapor pressure measurements. Film properties were evaluated with ellipsometry, x-ray photoelectron spectroscopy, secondary ion mass spectroscopy, and secondary electron microscopy. The growth rate per cycle was determined to extend from 0.3 to 2.4 Å/cycle with <4% nonuniformity (1-sigma) with-in-wafer across a 150 mm wafer for the investigated temperature range.
Treatment of MI2 (M = Ca, Sr, Ba) with two equivalents of thallium bis(3,5-di-tert-butylpyrazolyl)borate (TlBptBu2) in tetrahydrofuran at ambient temperature afforded CaBptBu22 (67%), SrBptBu22 (79%), and BaBptBu22(THF) (63%). Sublimation of BaBptBu22(THF) at 205 °C/0.05 Torr afforded BaBptBu22 (37%) along with loss of tetrahydrofuran. Crystal structure determinations of SrBptBu22, BaBptBu22(THF), and BaBptBu22 revealed monomeric structures containing highly distorted κ3-N,N,H-BptBu2 ligands. The M−N−N−B torsion angles in SrBptBu22, BaBptBu22(THF), and BaBptBu22 range from 20.00(8)° to 60.90(1)°, which indicate significant deformation of the 3,5-di-tert-butylpyrazolyl groups in order to avoid intraligand and interligand tert-butyl group steric repulsions. BH2(tBu2pz)(tBu2pzH) was prepared in 78% yield by treatment of Li(BptBu2)(THF) with pivalic acid, and its X-ray crystal structure was determined. To assess the viability of MBptBu22 (M = Ca, Sr, Ba) as potential thin-film growth precursors, solid-state decomposition studies, thermogravimetric analyses, and preparative sublimations were performed. SrBptBu22 is the most thermally stable among the series, with a solid-state decomposition temperature of 325 °C, a sublimation temperature of 190 °C/0.05 Torr, and a nonvolatile residue of 3.6% in a preparative sublimation. The TGA traces of CaBptBu22 and SrBptBu22 show weight loss regimes from 150 to 325 °C, with final percent residues of 20% and 25%, respectively. Several of the new complexes exhibit much higher thermal stability than existing group 2 chemical vapor deposition precursors and, thus, may serve as film growth precursors.
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