First-Principles Predictions and <i>in Situ</i> Experimental Validation of Alumina Atomic Layer Deposition on Metal Surfaces

Lu, Junling; Liu, Bin; Guisinger, Nathan P.; Stair, Peter C.; Greeley, Jeffrey; Elam, Jeffrey W.

doi:10.1021/cm503178j

Cited by 73 publications

(90 citation statements)

References 56 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…22 Coincidentally, we have observed that trimethylaluminum (TMA) undergoes dissociative chemisorption to form AlCH 3 * (the asterisk designates a surface species) on noble metal surfaces (Pd, Pt, and Ir) in the first Al 2 O 3 ALD cycle using TMA and water at 200°C. 36,37 Zaera et al observed that bis[(N,N′-di-sec-butyl acetamidinate)-Cu] adsorbs dissociatively on Ni(110) surfaces at temperatures between approximately 77 and 177°C; 38 Braun et al reported that ferrocene can even adsorb dissociatively on Au(111) surfaces at temperatures as low as 80 K using low temperature scanning tunneling microscopy (STM). 39 Such dissociative chemisorption of metal precursors on noble metal surfaces seems to be general due to the catalytic nature of noble metals.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Elam

2015

Chem. Mater.

Self Cite

View full text Add to dashboard Cite

Thermal atomic layer deposition (ALD) of noble metals is frequently performed using molecular oxygen as the nonmetal precursor to effect combustion-type chemistry at r e l a t i v e l y h i g h t e m p e r a t u r e s o f 3 0 0°C . B i s -(ethylcyclopentadienyl)ruthenium (Ru(EtCp) 2 ) is one of the commonly used metal precursors for Ru ALD. Using Ru(EtCp) 2 and oxygen as reactants, Ru ALD was achieved at near 300°C. Here, we demonstrate that Ru ALD can proceed at as low as 150°C by using successive exposures to oxygen and hydrogen as the coreactants. In situ quartz crystal microbalance (QCM) and quadrupole mass spectroscopy (QMS) measurements both suggest that this ABC-type ALD occurs through dissociative chemisorption, combustion, and reduction for the Ru(EtCp) 2 , oxygen, and hydrogen steps, respectively, in a similar manner to processes using ozone and hydrogen as coreactants reported previously. Moreover, we believe this molecular O 2 and H 2 based ABC-type ALD could be exploited for the ALD of other noble metals to decrease the deposition temperature and reduce oxygen impurities. ■ INTRODUCTIONUltrathin conformal Ru films have been used as electrodes in a variety of microelectronics applications including positivechannel metal oxide semiconductor (PMOS) metal gates and dynamic random access memory (DRAM) capacitors, due to the high work function (4.7 eV), low bulk resistivity (7.1 μΩ· cm), good thermal stability, and, more importantly, oxygen diffusion barrier property of Ru. 1−5 As the size of semiconductor devices decreases according to Moore's Law, complicated three-dimensional (3-D) nanostructures will be needed to achieve high storage capacities. 6−9 As a consequence, the requirements for conformality, thickness control, and low temperature of the Ru deposition process become more severe. Among the various thin film deposition techniques, atomic layer deposition (ALD) is considered to be the most promising for meeting these requirements. 10−12 Ruthenium ALD has been widely explored using a variety of Ru precursors including metallocenes, β-diketonates, and their derivatives. 13−21 In these studies, molecular oxygen is most often employed as the nonmetal precursor for thermal Ru ALD. As with similar noble metal ALD processes utilizing O 2 (e.g., Pt, Rh, and Ir), the Ru ALD is thought to follow a combustiontype mechanism in which the metal organic precursor first reacts with surface oxygen to burn off a fraction of the ligands, and then the rest of the ligands are further combusted in the subsequent oxygen exposure step. The oxygen exposure also serves to replenish the surface oxygen through dissociation on the noble metal surface. Carbon dioxide and water are the major gaseous products formed during the two half reactions, 13,22−25 while in some cases dehydrogenation can also occur. 24,26 This oxygen-based, combustion-type noble metal ALD typically requires relatively high temperature above 200°C (near 300°C in most cases), to burn off the organic ligands. [13][14][15][16][17][18][19][20]25,27,28 Th...

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Elam

2015

Chem. Mater.

Self Cite

View full text Add to dashboard Cite

show abstract

“…This is consistent with very low carbon coverage that was observed during the early stages of TMA adsorption at 300 and 473 K ( Figure 5) and literature reports of CH 4 (methane) and C 2 H 6 (ethane) desorption during exposure of Pd nanoparticles to TMA. 20,56,79 Another route for carbon disappearance could be dissolution of carbon in palladium bulk (Figure 14h). 47 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 Figure 15 shows the TMA adsorption and dissociation mechanisms on Pt(111 Fig SI.3).…”

Section: Pd(111)mentioning

confidence: 99%

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

et al. 2015

View full text Add to dashboard Cite

The behavior of trimethylaluminium (TMA) was investigated on the surfaces of Pt(111) andPd(111) single crystals. TMA was found to dissociatively adsorb on both surfaces between 300 -473 K. Surfaces species observed by high-resolution electron energy loss spectroscopy (HREELS) and X-ray photoelectron spectroscopy (XPS) after TMA adsorption at 300 K included Al-CH 3 and CH x,ads (x = 1, 2, or 3) on Pt(111), and ethylidyne (CCH 3 ), CH x,ads (x = 1, 2, or 3), and metallic Al on Pd(111). Density functional theory (DFT) calculations predicted methylaluminum (MA, Al-CH 3 ) to be the most kinetically favorable TMA decomposition product on (111) terraces of both surfaces, however, HREELS signatures for Al-CH 3 were detected only on Pt(111), whereas ethylidyne was observed on Pd(111). XPS demonstrated higher amount of carbonaceous species on Pt(111) than on Pd (111) DFT calculations showed that further dissociation of MA to metallic aluminum and methyl groups to be more kinetically favorable on step sites of both metals. In our proposed reaction mechanism, MA migrates to and dissociates at Pd(111) steps at 300 K forming adsorbed methyl groups and metallic Al. Some methyl groups dehydrogenate and recombine forming ethylidyne. Metallic Al or ejected Pd atoms from steps diffuse across Pd(111) terraces until coalescing into irregularly shaped islands on terraces or steps, as observed by scanning tunneling microscopy (STM). Upon heating above 300 K, the Pd-Al alloy diffuses into the Pd bulk. On Pt(111), a high coverage of carboncontaining species following TMA adsorption at 300 K prevented MA diffusion and dissociation at steps, as evidenced by isolated clusters of MA in STM images. Heating above 300 K resulted in MA dissociation, but no Pt-Al alloy formation was observed. We conclude that the differing abilities of Pd and Pt to hydrogenate carbonaceous species plays a key role in MA dissociation and alloy formation, and, therefore, the adsorption and dissociation chemistry of TMA depends on properties of the metal substrate surface and determines thin film morphology and composition.

show abstract

“…A detailed understanding of ferrocene adsorption and oxidation, as well as the formation of monolayer thick FeO islands on Pt(111), is developed here using a suite of Ultra High Vacuum (UHV) surface sensitive techniques, whose efficacy has been established in previous studies of vacuum ALD. [38][39][40][41][42] …”

Section: Introductionmentioning

confidence: 99%

Atomic Layer Deposition of FeO on Pt(111) by Ferrocene Adsorption and Oxidation

et al. 2015

View full text Add to dashboard Cite

We report the synthesis of a sub-monolayer thick film of FeO(111) on the Pt(111) surface using atomic layer deposition (ALD) under well-defined ultra high vacuum (UHV) conditions. FeO islands were characterized by scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS). FeO(111) on Pt(111) was prepared through adsorption and oxidation of ferrocene. Because ferrocene adsorption is crucial to the overall process, it was studied in detail at different exposures and temperatures. At low exposures and at 300 K, ferrocene was found to adsorb dissociatively mainly as Cp (cyclopentadienyl ring). At high exposures, molecular adsorption dominated, and the dissociation fragments were replaced with ferrocene molecules. The adsorbed ferrocene desorbed from the Pt(111) surface at a temperature between 473 and 573 K. FeO(111) islands were grown by exposing the ferrocene adlayer to 1×10 -6 mbar O 2 at 623 K resulted in islands with the shape of truncated triangles and hexagons. The resulting surface was free of carbon, which presumably oxidized and desorbed as CO 2 . The FeO islands had a uniform height of 0.15 nm as measured by STM, and the FeO coverage could be controlled by the number of ferrocene adsorption/oxidation cycles. Due to rotational and lattice mismatches between FeO(111) and Pt (111), a pattern with approximately 2 nm periodicity was observed. In UHV, FeO began to decompose at a temperature between 673 and 873 K. Annealing in O 2 at 873 K also resulted in a net decrease of FeO amount through iron dissolution in the platinum bulk.

show abstract

First-Principles Predictions and in Situ Experimental Validation of Alumina Atomic Layer Deposition on Metal Surfaces

Cited by 73 publications

References 56 publications

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Low Temperature ABC-Type Ru Atomic Layer Deposition through Consecutive Dissociative Chemisorption, Combustion, and Reduction Steps

Surface Chemistry of Trimethylaluminum on Pd(111) and Pt(111)

Atomic Layer Deposition of FeO on Pt(111) by Ferrocene Adsorption and Oxidation

Contact Info

Product

Resources

About