Benefits of energetic ion bombardment for tailoring stress and microstructural evolution during growth of Cu thin films

Cemin, Felipe; Abadias, G.; Minea, Tiberiu; Furgeaud, Clarisse; Brisset, François; Solas, Denis; Lundin, Daniel

doi:10.1016/j.actamat.2017.09.007

Cited by 60 publications

(31 citation statements)

References 68 publications

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“…However, in high power impulse magnetron sputtering (HiPIMS) discharges, a large fraction of sputtered atoms, up to 50–80%, gets ionized [ 115 ], so that applying a bias voltage can be advantageously used to tailor the film microstructure by controlling the energy of film-forming species. Cemin et al [ 116 ] have reported that the thickness at which Cu films are continuous could be increased from

~7 to ~12 nm by increasing the bias from 0 to 130 V, due to enhanced adatom mobility. This results in the formation of Cu films with larger grain size, reduced compressive stress, and higher electrical conductivity [ 116 , 117 ].…”

Section: Growth Of Metal Films On Weakly-interacting Substratesmentioning

confidence: 99%

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools

et al. 2020

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Continued downscaling of functional layers for key enabling devices has prompted the development of characterization tools to probe and dynamically control thin film formation stages and ensure the desired film morphology and functionalities in terms of, e.g., layer surface smoothness or electrical properties. In this work, we review the combined use of in situ and real-time optical (wafer curvature, spectroscopic ellipsometry) and electrical probes for gaining insights into the early growth stages of magnetron-sputter-deposited films. Data are reported for a large variety of metals characterized by different atomic mobilities and interface reactivities. For fcc noble-metal films (Ag, Cu, Pd) exhibiting a pronounced three-dimensional growth on weakly-interacting substrates (SiO2, amorphous carbon (a-C)), wafer curvature, spectroscopic ellipsometry, and resistivity techniques are shown to be complementary in studying the morphological evolution of discontinuous layers, and determining the percolation threshold and the onset of continuous film formation. The influence of growth kinetics (in terms of intrinsic atomic mobility, substrate temperature, deposition rate, deposition flux temporal profile) and the effect of deposited energy (through changes in working pressure or bias voltage) on the various morphological transition thicknesses is critically examined. For bcc transition metals, like Fe and Mo deposited on a-Si, in situ and real-time growth monitoring data exhibit transient features at a critical layer thickness of ~2 nm, which is a fingerprint of an interface-mediated crystalline-to-amorphous phase transition, while such behavior is not observed for Ta films that crystallize into their metastable tetragonal β-Ta allotropic phase. The potential of optical and electrical diagnostic tools is also explored to reveal complex interfacial reactions and their effect on growth of Pd films on a-Si or a-Ge interlayers. For all case studies presented in the article, in situ data are complemented with and benchmarked against ex situ structural and morphological analyses.

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Section: Growth Of Metal Films On Weakly-interacting Substratesmentioning

confidence: 99%

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools

et al. 2020

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“…Ionized film-forming species can be accelerated to the substrate by applying a potential (i.e., substrate bias), which allows setting the energy range and nature of species arriving at the substrate, i.e., ions offer an additional tool to engineer the morphology of growing films. [33]…”

Section: Magnetron Sputter-depositionmentioning

confidence: 99%

“…The energy of arriving species on the substrate is instrumental in the texture evolution of the growing film, i.e., high-energy atoms promote surface rearrangement processes. [33,67] Deposition profile and rate, as well as energy 3.6 Influence of process parameters on microstructural evolution and direction of sputtered particles can be simulated with the Simulation of the Metal Transport (SiMTra) Monte Carlo program. [68] It simulates the transport of sputtered particles through the working gas considering binary collisions, and the user can implement the experimental setup (e.g., chamber dimensions).…”

Section: 63mentioning

confidence: 99%

Thin metal films on weakly-interacting substrates : Nanoscale growth dynamics, stress generation, and morphology manipulation

Jamnig

2020

Linköping Studies in Science and Technology. Dissertations

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Vapor-based growth of thin metal films with controlled morphology on weaklyinteracting substrates (WIS), including oxides and van der Waals materials, is essential for the fabrication of multifunctional metal contacts in a wide array of optoelectronic devices. Achieving this entails a great challenge, since weak film/substrate interactions yield a pronounced and uncontrolled 3D morphology. Moreover, the far-from-equilibrium nature of vapor-based film growth often leads to generation of mechanical stress, which may further compromise device reliability and functionality. The objectives of this thesis are related to metal film growth on WIS and seek to: (i) contribute to the understanding of atomic-scale processes that control film morphological evolution; (ii) elucidate the dynamic competition between nanoscale processes that govern film stress generation and evolution; and (iii) develop methodologies for manipulating and controlling nanoscale film morphology between 2D and 3D. Investigations focus on magnetron sputter-deposited Ag and Cu films on SiO2 and amorphous carbon (a-C) substrates. Research is conducted by strategically combining of in situ and real-time film growth monitoring, ex situ chemical and (micro)-structural analysis, optical modelling, and deterministic growth simulations. Preface The present dissertation is the result of my doctoral studies carried out between 2016 and 2020 in the Physics and Properties of Nanostructures (PPNa) group at the

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“…Recently, reactive high-power impulse magnetron sputtering (r-HiPIMS) has become promising technology for various material preparation [18][19][20][21][22][23][24][25]. The magnetron discharge is generated in short pulses (10-100 µs) with low frequency of pulsing (100 Hz-1 kHz).…”

Section: Introductionmentioning

confidence: 99%

Semiconducting p-Type Copper Iron Oxide Thin Films Deposited by Hybrid Reactive-HiPIMS + ECWR and Reactive-HiPIMS Magnetron Plasma System

et al. 2020

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A reactive high-power impulse magnetron sputtering (r-HiPIMS) and a reactive high-power impulse magnetron sputtering combined with electron cyclotron wave resonance plasma source (r-HiPIMS + ECWR) were used for the deposition of p-type CuFexOy thin films on glass with SnO2F conductive layer (FTO). The aim of this work was to deposit CuFexOy films with different atomic ratio of Cu and Fe atoms contained in the films by these two reactive sputtering methods and find deposition conditions that lead to growth of films with maximum amount of delafossite phase CuFeO2. Deposited copper iron oxide films were subjected to photoelectrochemical measurement in cathodic region in order to test the possibility of application of these films as photocathodes in solar hydrogen production. The time stability of the deposited films during photoelectrochemical measurement was evaluated. In the system r-HiPIMS + ECWR, an additional plasma source based on special modification of inductively coupled plasma, which works with an electron cyclotron wave resonance ECWR, was used for further enhancement of plasma density ne and electron temperature Te at the substrate during the reactive sputtering deposition process. A radio frequency (RF) planar probe was used for the determination of time evolution of ion flux density iionflux at the position of the substrate during the discharge pulses. Special modification of this probe to fast sweep the probe system made it possible to determine the time evolution of the tail electron temperature Te at energies around floating potential Vfl and the time evolution of ion concentration ni. This plasma diagnostics was done at particular deposition conditions in pure r-HiPIMS plasma and in r-HiPIMS with additional ECWR plasma. Generally, it was found that the obtained ion flux density iionflux and the tail electron temperature Te were systematically higher in case of r-HiPIMS + ECWR plasma than in pure r-HiPIMS during the active part of discharge pulses. Furthermore, in case of hybrid discharge plasma excitation, r-HiPIMS + ECWR plasma has also constant plasma density all the time between active discharge pulses ni ≈ 7 × 1016 m−3 and electron temperature Te ≈ 4 eV, on the contrary in pure r-HiPIMS ni and Te were negligible during the “OFF” time between active discharge pulses. CuFexOy thin films with different atomic ration of Cu/Fe were deposited at different conditions and various crystal structures were achieved after annealing in air, in argon and in vacuum. Photocurrents in cathodic region for different achieved crystal structures were observed by chopped light linear voltammetry and material stability by chronoamperometry under simulated solar light and X-ray diffraction (XRD). Optimization of depositions conditions results in the desired Cu/Fe ratio in deposited films. Optimized r-HiPIMS and r-HiPIMS + ECWR plasma deposition at 500 °C together with post deposition heat treatment at 650 °C in vacuum is essential for the formation of stable and photoactive CuFeO2 phase.

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Benefits of energetic ion bombardment for tailoring stress and microstructural evolution during growth of Cu thin films

Cited by 60 publications

References 68 publications

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools

In Situ and Real-Time Nanoscale Monitoring of Ultra-Thin Metal Film Growth Using Optical and Electrical Diagnostic Tools

Thin metal films on weakly-interacting substrates : Nanoscale growth dynamics, stress generation, and morphology manipulation

Semiconducting p-Type Copper Iron Oxide Thin Films Deposited by Hybrid Reactive-HiPIMS + ECWR and Reactive-HiPIMS Magnetron Plasma System

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