The initial stages of cobalt metal growth by atomic layer deposition are described using the precursors bis(1,4-di-tert-butyl-1,3-diazadienyl)cobalt and formic acid. Ruthenium, platinum, copper, Si(100), Si-H, SiO, and carbon-doped oxide substrates were used with a growth temperature of 180 °C. On platinum and copper, plots of thickness versus number of growth cycles were linear between 25 and 250 cycles, with growth rates of 0.98 Å/cycle. By contrast, growth on ruthenium showed a delay of up to 250 cycles before a normal growth rate was obtained. No films were observed after 25 and 50 cycles. Between 100 and 150 cycles, a rapid growth rate of ∼1.6 Å/cycle was observed, which suggests that a chemical vapor deposition-like growth occurs until the ruthenium surface is covered with ∼10 nm of cobalt metal. Atomic force microscopy showed smooth, continuous cobalt metal films on platinum after 150 cycles, with an rms surface roughness of 0.6 nm. Films grown on copper gave rms surface roughnesses of 1.1-2.4 nm after 150 cycles. Films grown on ruthenium, platinum, and copper showed resistivities of <20 μΩ cm after 250 cycles and had values close to those of the uncoated substrates at ≤150 cycles. X-ray photoelectron spectroscopy of films grown with 150 cycles on a platinum substrate showed surface oxidation of the cobalt, with cobalt metal underneath. Analogous analysis of a film grown with 150 cycles on a copper substrate showed cobalt oxide throughout the film. No film growth was observed after 1000 cycles on Si(100), Si-H, and carbon-doped oxide substrates. Growth on thermal SiO substrates gave ∼35 nm thick layers of cobalt(ii) formate after ≥500 cycles. Inherently selective deposition of cobalt on metallic substrates over Si(100), Si-H, and carbon-doped oxide was observed from 160 °C to 200 °C. Particle deposition occurred on carbon-doped oxide substrates at 220 °C.

The atomic layer deposition growth of Ga 2 O 3 films was demonstrated using Ga 2 (NMe 2 ) 6 and water with substrate temperatures between 150 and 300 °C. At 250 °C, surface saturative growth was achieved with Ga 2 (NMe 2 ) 6 vapor pulse lengths of g1.5 s. The growth rate was 1.0 Å/cycle at substrate temperatures between 170 and 250 °C. Growth rates of 1.1 and 0.89 Å/cycle were observed at 150 and 275 °C, respectively. In a series of films deposited at 250 °C, the film thicknesses varied linearly with the number of deposition cycles. Time-of-flight elastic recoil detection analyses demonstrated stoichiometric Ga 2 O 3 films, with carbon, hydrogen, and nitrogen levels between 1 and 2.1, 4.8-5.4, and 0.6-0.9 at. %, respectively, at substrate temperatures of 170, 200, and 250 °C. The as-deposited films were amorphous, but crystallized to β-Ga 2 O 3 films upon annealing between 700 and 900 °C under a nitrogen atmosphere. Atomic force microscopy showed root-mean-square surface roughnesses of 0.4 and 0.6 nm for films deposited at 170 and 250 °C, respectively.

Treatment of anhydrous rare earth chlorides with three equivalents of lithium 1,3-di-tertbutylacetamidinate (prepared in situ from the di-tert-butylcarbodiimide and methyllithium) in tetrahydrofuran at ambient temperature afforded Ln( t BuNC(CH 3 )N t Bu) 3 (Ln = Y, La, Ce, Nd, Eu, Er, Lu) in 57-72% isolated yields. X-Ray crystal structures of these complexes demonstrated monomeric formulations with distorted octahedral geometry about the lanthanide(III) ions. These new complexes are thermally stable at .300 uC, and sublime without decomposition between 180-220 uC/0.05 Torr. The atomic layer deposition of Er 2 O 3 films was demonstrated using Er( t BuNC(CH 3 )N t Bu) 3 and ozone with substrate temperatures between 225-300 uC. The growth rate increased linearly with substrate temperature from 0.37 A ˚per cycle at 225 uC to 0.55 A ˚per cycle at 300 uC. Substrate temperatures of .300 uC resulted in significant thickness gradients across the substrates, suggesting thermal decomposition of the precursor. The film growth rate increased slightly with an erbium precursor pulse length between 1.0 and 3.0 s, with growth rates of 0.39 and 0.51 A ˚per cycle, respectively. In a series of films deposited at 250 uC, the growth rates varied linearly with the number of deposition cycles. Time of flight elastic recoil analyses demonstrated slightly oxygen-rich Er 2 O 3 films, with carbon, hydrogen and fluorine levels of 1.0-1.9, 1.7-1.9 and 0.3-1.3 atom%, respectively, at substrate temperatures of 250 and 300 uC. Infrared spectroscopy showed the presence of carbonate, suggesting that the carbon and slight excess of oxygen in the films are due to this species. The as-deposited films were amorphous below 300 uC, but showed reflections due to cubic Er 2 O 3 at 300 uC. Atomic force microscopy showed a root mean square surface roughness of 0.3 and 2.8 nm for films deposited at 250 and 300 uC, respectively.

Atomic layer deposition (ALD) processes are reported for ruthenium (Ru) and ruthenium oxide (RuO 2 ) using a zero-oxidation state liquid precursor, η 4 -2,3-dimethylbutadiene ruthenium tricarbonyl [Ru(DMBD)(CO) 3 ]. Both ALD Ru and RuO 2 films were deposited using alternating N 2 -purge-separated pulses of Ru(DMBD)(CO) 3 and O 2 . ALD Ru metal films were deposited via short (2 s) pulses of O 2 . Ru films have an ALD temperature window from 290 to 320 °C with a GPC of 0.067 nm/ cycle and a negligible nucleation delay on SiO 2 . Ru films show a strong hexagonal crystal structure with low resistivity of approximately 14 μΩ cm at 320 °C. RuO 2 films were deposited using longer (20 s) pulses of either molecular O 2 or O 2 plasma. RuO 2 films deposited via thermal ALD using molecular O 2 have a temperature window from 220 to 240 °C with a GPC and nucleation delay on SiO 2 of 0.065 nm/cycle and 35 cycles, respectively. Thermal ALD RuO 2 films show a distinct rutile phase microstructure with a resistivity of approximately 62 μΩ cm. In comparison to thermal ALD, the PEALD RuO x films show a lower growth rate and higher nucleation delay of 0.029 nm/cycle and 76 cycles, respectively. PEALD RuO x films also exhibit less distinct crystallinity and a higher resistivity of 377 μΩ cm.

ZrO 2 thin films were grown onto silicon (100) substrates by atomic layer deposition (ALD) using novel cyclopentadienyl-type precursors, namely (CpMe) 2 ZrMe 2 and (CpMe) 2 Zr(OMe)Me (Cp ¼ cyclopentadienyl, C 5 H 5 ) together with ozone as the oxygen source. Growth characteristics were studied in the temperature range of 250 to 500 C. An ALD-type self-limiting growth mode was verified for both processes at 350 C where highly conformal films were deposited onto high aspect ratio trenches. Signs of thermal decomposition were not observed at or below 400 C, a temperature considerably exceeding the thermal decomposition temperature of the Zr-alkylamides. Processing parameters were optimised at 350 C, where deposition rates of 0.55 and 0.65 A ˚cycle À1 were obtained for (CpMe) 2 ZrMe 2 /O 3 and (CpMe) 2 Zr(OMe)Me/O 3 , respectively. The films grown from both precursors were stoichiometric and polycrystalline with an increasing contribution from the metastable cubic phase with decreasing film thickness. In the films grown from (CpMe) 2 ZrMe 2 , the breakdown field did not essentially depend on the film thickness, whereas in the films grown from (CpMe) 2 Zr(OMe)Me the structural homogeneity and breakdown field increased with decreasing film thickness. The films exhibited good capacitive properties that were characteristic of insulating oxides and did not essentially depend on the precursor chemistry.

No abstract

Ruthenium (Ru) films are deposited using atomic layer deposition (ALD), promoted by a self-catalytic reaction mechanism. Using zero-valent, η 4 -2,3-dimethylbutadiene Ruthenium tricarbonyl (Ru(DMBD)(CO) 3 ) and H 2 O, Ru films are deposited at a rate of 0.1 nm/cycle. The temperature for steady deposition lies between 160 and 210 °C. Film structure and composition are confirmed via X-ray diffraction, high-resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The room-temperature electrical resistivity of 10 nm Ru films is found to be 39 μΩ• cm. In situ quadrupole mass spectrometry and density functional theory are used to understand ALD surface reactions. The ligand, dimethylbutadiene dissociatively desorbs on the surface. On the other hand, the carbonyl ligand is catalyzed by the Ru center. This leads to the water gas shift reaction, forming CO 2 and H 2 . Modulating deposition temperature affects these two ligand dissociation reactions. This in turn affects nucleation, growth, and hence, Ru film properties. Self-catalyzed reactions provide a pathway for low-temperature ALD with milder co-reactants.

The need for the conformal deposition of TiO 2 thin films in device fabrication has motivated a search for thermally robust titania precursors with noncorrosive byproducts. Alkylamido-cyclopentadienyl precursors are attractive because they are readily oxidized, yet stable, and afford environmentally mild byproducts. We have explored the deposition of TiO 2 films on OH-terminated SiO 2 surfaces by in situ Fourier transform infrared spectroscopy using a novel titanium precursor [(EtCp)-Ti(NMe 2 ) 3 (1), Et = CH 2 CH 3 ] with either ozone or water. This precursor initially reacts with surface hydroxyl groups at ≥150 °C through the loss of its NMe 2 groups. However, once the precursor is chemisorbed, its subsequent reactivities toward ozone and water are very different. There is a clear reaction with ozone, characterized by the formation of monodentate formate and/or chelate bidentate carbonate surface species; in contrast, there is no detectable reaction with water. For the ozone-based ALD process, the surface formate/carbonate species react with the NMe 2 groups during the subsequent pulse of 1, forming TiOTi bonds. Ligand exchange is observed within the 250−300 °C ALD window. X-ray photoelectron spectroscopy confirms the deposition of stoichiometric TiO 2 films with no detectable impurities. For the water-based process, ligand exchange is not observed. Once 1 is adsorbed, there is no spectroscopic evidence for further reaction. However, there is still TiO 2 deposition under typical ALD conditions. Co-adsorption experiments with controlled vapor pressures of water and 1 indicate that deposition arises solely from 1/water gas-phase reactions. This striking lack of reactivity between chemisorbed 1 and water is attributed to the electronic and steric effects of the EtCp group and facilitates the observation of gas-phase reactions.