Control of the Cu morphology on Ru-passivated and Ru-doped TaN surfaces – promoting growth of 2D conducting copper for CMOS interconnects

Nies, Cara-Lena; Natarajan, Suresh Kondati; Nolan, Michael

doi:10.1039/d1sc04708f

Cited by 6 publications

(14 citation statements)

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“…3D metal growth is undesirable in many applications, in particular in microelectronics manufacturing. For instance, it is known that, in general, the Cu films deposited as interconnects by ALD exhibit significantly increased resistivity, allegedly because they form nonconducting islands rather than smooth conducting films . Ideal ALD processes provide conformal 2D films, but in the case of Cu deposition on silicon oxide substrates that appears to be difficult to attain.…”

Section: Discussionmentioning

confidence: 99%

On the Mechanism of the Atomic Layer Deposition of Cu Films on Silicon Oxide Surfaces: Activation Using Atomic Hydrogen and Three-Dimensional Growth

2023

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The molecular details of the atomic layer deposition (ALD) of metallic copper on silicon oxide substrates using metallorganic precursors, iminopyrrolidinate complexes in particular, were characterized under ultrahigh vacuum conditions by temperature-programmed desorption (TPD), in its temperature ramping and isothermal modes, and by X-ray photoelectron spectroscopy (XPS). Two specific issues were addressed. First, it was demonstrated that H 2 is quite inefficient as a reducing agent and cannot be effectively used to remove the organic ligands in the adsorbed species during the ALD cycles; insufficient ligand removal leads to the incorporation of impurities in the growing films. On the other hand, atomic hydrogen can accomplish both metal reducing and ligand removal functions and can be incorporated in ALD processes to deposit incremental amounts of Cu in sequential cycles. The second aspect discussed here is the fact that the deposited metallic Cu grows in the form of three-dimensional (3D) nanoparticles rather than as conformal twodimensional films. The TPD and XPS evidence collected in our studies points to a mechanism where individual Cu atoms, once cleaned from their organic ligands and reduced to their metallic state, become quite mobile and diffuse on the SiO 2 surface to form the 3D nanostructures. Similar Cu atom mobility and sintering were seen even in Cu physical vapor deposition processes carried out at room temperature and may therefore be an intrinsic feature of these ALDs regardless of the source of the metal atoms.

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Section: Discussionmentioning

confidence: 99%

On the Mechanism of the Atomic Layer Deposition of Cu Films on Silicon Oxide Surfaces: Activation Using Atomic Hydrogen and Three-Dimensional Growth

2023

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“…Additionally, the ratios of metals in the material can be used to further tune the material to have low resistivity and good wettability while maintaining strong barrier properties. This type of work also includes our work on Ru-doped TaN which demonstrated that Cu wetting can be promoted on TaN surfaces by incorporating a known liner material and provides the foundation for the work presented in this paper [29][30][31].…”

Section: Introductionmentioning

confidence: 95%

“…In our previous work [29][30][31] we showed that by doping Ru atoms into the top layer of a TaN surface, a single material with both barrier and liner properties can be created. Such a material can be deposited using ALD.…”

Section: Introductionmentioning

confidence: 99%

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Incorporation of tungsten or cobalt into TaN barrier layers controls morphology of deposited copper

Nies¹,

Nolan²

2023

J. Phys. Mater.

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Progress in semiconductor devices, which has enabled the information and communications technology explosion of the 21st century, has been driven by Moore’s Law and the accompanying aggressive scaling of transistors. However, it is now acknowledged that the currently used copper interconnects are becoming a bottleneck in sub-nm scaling. Semiconductor devices require a diffusion barrier and a seed layer in the volume available to the interconnect metal. This then limits the minimum size of the interconnect and copper suffers from a preference to form 3D islands which are non-conducting rather than conducting films. Therefore there is a pressing need to either replace copper, which has its own difficulties, or to reduce the volume taken up by the diffusion barrier and liner; ideally finding a single material displaying both properties is needed. We have previously shown that incorporation of Ru into the surface layer of TaN is a strong alternative to the usual TaN/Ta or TaN/Ru stacks. In this work we study other possible metals that can be incorporated into TaN, namely Co and W, which are less expensive and critical than Ru and can potentially outperform it. Our first principles density functional theory (DFT) results from static relaxations and ab initio Molecular Dynamics (aiMD) show that there are several compositions of both Co- and W-doped TaN which should promote growth of 2D copper interconnects without compromising the barrier properties of TaN. With this selection of materials it should be possible to design new experimental processes that promote downscaled copper interconnects for the next generation of electronic devices. Additionally, our work presents an improved method towards prediction of thin film morphology on a given substrate, which can be of use for a variety of materials science applications.

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“…The microelectronic manufacturing community has shown great interest in recent years in finding ways to deposit thin ruthenium films for use in developing metal interconnects (either as diffusion barriers for Cu − or as the conducting material itself) , as well as to introduce seed layers for electroplating, − electrodes in capacitors and dynamic random access memory (DRAM) devices, − and gate metals in transistors, , among other applications. Because of the complex topography and small dimensions of the features in the surfaces of modern microelectronics circuits, thin films with great conformality are required, and one of the most promising routes to achieve that is the use of atomic layer deposition (ALD). − …”

Section: Introductionmentioning

confidence: 99%

Atomic Layer Deposition of Ruthenium Films Using Ruthenium Diketonates and O₂, H₂, or N₂O: The Role of Ruthenium Etching

Qin

Zaera

2022

J. Phys. Chem. C

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The evolution of the surface during the steps that comprise the atomic layer deposition (ALD) of ruthenium films on a nickel substrate using tris(2,2,6,6-tetramethyl-3,5-heptanedionato)ruthenium(III) (Ru(tmhd)3) and molecular oxygen was characterized using a combination of X-ray photoelectron (XPS) and reflection–absorption infrared (RAIRS) spectroscopies. The uptake of the Ru metalorganic precursor was determined to be activated, involving the average loss of two out of the three ligands (and the retention of the third, in molecular form, at the surface–vacuum interface), and self-limited, as required in ALD. The reaction of the resulting layer from that first half of the ALD cycle with O2 proved to be more complex: in addition to the desired removal of the carbon-containing material, the Ni substrate becomes oxidized, and some Ru is etched away in the form of the volatile RuO4 gas. By testing different combinations of exposures and temperatures it was determined that Ru film growth was possible, but tuning and optimizing the ALD or atomic layer etching (ALE) process conditions for maximum film growth or removal rate per cycle proved difficult. Replacing O2 with H2 was shown not to be viable either, as such an agent can reduce the nickel oxide formed after O2 treatments (in fact, Ru(tmhd)3 can do this as well) but not remove the carbonaceous material deposited on the surface by the Ru precursor. The use of N2O, on the other hand, showed much promise, being capable of removing most of the surface carbon without affecting the Ru film or the Ni substrate.

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Control of the Cu morphology on Ru-passivated and Ru-doped TaN surfaces – promoting growth of 2D conducting copper for CMOS interconnects

Abstract: Prolonging the lifetime of Cu as level 1 and level 2 interconnect metal in future nanoelectronic devices is a significant challenge as device dimensions continue to shrink and device structures...

Cited by 6 publications

References 63 publications

On the Mechanism of the Atomic Layer Deposition of Cu Films on Silicon Oxide Surfaces: Activation Using Atomic Hydrogen and Three-Dimensional Growth

On the Mechanism of the Atomic Layer Deposition of Cu Films on Silicon Oxide Surfaces: Activation Using Atomic Hydrogen and Three-Dimensional Growth

Incorporation of tungsten or cobalt into TaN barrier layers controls morphology of deposited copper

Atomic Layer Deposition of Ruthenium Films Using Ruthenium Diketonates and O₂, H₂, or N₂O: The Role of Ruthenium Etching

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Control of the Cu morphology on Ru-passivated and Ru-doped TaN surfaces – promoting growth of 2D conducting copper for CMOS interconnects

Abstract: Prolonging the lifetime of Cu as level 1 and level 2 interconnect metal in future nanoelectronic devices is a significant challenge as device dimensions continue to shrink and device structures...

Cited by 6 publications

References 63 publications

On the Mechanism of the Atomic Layer Deposition of Cu Films on Silicon Oxide Surfaces: Activation Using Atomic Hydrogen and Three-Dimensional Growth

On the Mechanism of the Atomic Layer Deposition of Cu Films on Silicon Oxide Surfaces: Activation Using Atomic Hydrogen and Three-Dimensional Growth

Incorporation of tungsten or cobalt into TaN barrier layers controls morphology of deposited copper

Atomic Layer Deposition of Ruthenium Films Using Ruthenium Diketonates and O2, H2, or N2O: The Role of Ruthenium Etching

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Product

Resources

About

Atomic Layer Deposition of Ruthenium Films Using Ruthenium Diketonates and O₂, H₂, or N₂O: The Role of Ruthenium Etching