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Gaseous precursors for the atomic layer deposition (ALD) process can penetrate and deposit inside porous dielectrics. Understanding the relationship between the substrate porosity and the size and shape of precursor molecules used for the ALD of dielectric or metal films on these substrates is crucial for the formation and fabrication of reliable nanostructures. Sealing the surface pores is highly desirable to prevent the deposition of gaseous ALD precursors inside the porous network. In this study, in-diffusion of precursors is investigated using x-ray reflectivity, transmission electron microscopy, and Rutherford backscattering spectrometry for different porous substrates and binary (TaN) and ternary (WNC) ALD systems. Experimental observations are complemented with computational molecular modeling performed in the framework of the density-functional-theory formalism to determine the size and shape of ALD precursors. Pore sealing treatments are used to prevent a precursor penetration and to provide a suitable starting surface for the nucleation and growth of ALD films. [ABSTRACT FROM AUTHOR]

On nanoscale laminate structures, the interface cannot be identified any longer as the separation between two films of bulk materials. The formation of the interface defines the final composition and structure of the laminate structure. As such, the characterization of the interface becomes an important challenge. In this work the nanoscale laminate structures were formed by atomic layer deposition (ALD) of tungsten nitride carbide and tantalum nitride thin films on dense dielectrics [silicon carbide and silicon oxide (SiO2)]. The laminates were studied using x-ray reflectivity. The starting substrate surface is a primary factor in determining the density of the ALD layer. Moreover, in some cases, electron-density perturbations are observed in the vicinity of the interfacial region. A characterization strategy, using a density contrast layer between the silicon substrate and the SiO2 dielectric is presented. Depending on the chemical nature of precursors and substrate, ALD processes can either form specific interfacial organization or induce dielectric modifications, in any case, leading to unexpected metal-dielectric interactions. [ABSTRACT FROM AUTHOR]

Abstract: In order to enable an oxide-free Cu-to-Cu bonding in a (dual) damascene process, 3-aminopropyltrimethoxysilane- and decanethiol-derived self-assembled monolayers are selectively deposited in a dielectric-Cu based metal–insulator–metal (MIM) capacitor used as a test vehicle, which represents a dual damascene architecture environment. A two-steps SAM coating sequence is investigated for this purpose. In a first step, a “sacrificial” SHSAM is deposited on the Cu areas at the bottom of the vias. In a second step, a “barrier” NH2SAM is deposited on the dielectric areas in the field region and via’s sidewalls. This deposition sequence followed by the selective thermal ablation of the “sacrificial” SAM vs. the “barrier” SAM, enable an oxide-free Cu-to-Cu connection at via’s bottom. The differential in thermal stability between the amino and thiol SAMs has been studied by water contact angle and cyclic voltammetry. While the sacrificial SAM is selectively desorbed by thermal ablation already at ∼200°C, the barrier SAM on the dielectric sidewall and field regions withstands a thermal budget as high as ∼350°C. The substrate-selective SAMs depositions are revealed by XPS chemical characterization on the Cu and dielectric areas of the MIM structures supported by the SEM visualization of the Au nanoparticles that selectively decorate the NH2 functionalities of the barrier SAM. [Copyright &y& Elsevier]

Abstract: Interfaces play a crucial role in determining the ultimate properties of nanoscale structures. However, the characterization of such structures is difficult, as the interface can no longer be defined as the separation between two materials. The high sensitivity of electron density to surface and interface reactions has attracted increasing interest in application of X-ray reflectivity (XRR) as probing technique. In this study, the nanolaminate structures were formed by atomic layer deposition (ALD) of tungsten nitride carbide (WNC) and tantalum nitride (TaN) thin films on silicon carbide (SiC), silicon oxide (SiO2) and silicon oxynitride (SiON) substrates and subsequently characterized by XRR. The goal is to establish a relationship between surface chemistry, interface properties and density of the final structure. To achieve this objective, the density variations at the interfaces between ALD TaN and ALD WNC with SiC, SiO2 and SiON films will be quantified by modeling analysis of XRR reflection spectra. From these modeled electron density profiles, specific mechanisms leading to surface dependent structural behavior are proposed. [Copyright &y& Elsevier]

It is known that porous organosilicate glass (OSG) dielectrics tend to lose functional groups and become denser upon the chemical and physical action of the plasmas, but an accurate analysis and estimation of the depth and degree of film densification is not straightforward. In this study, we show that the combination of techniques like x-ray reflectivity, surface acoustic waves, and nanoindentation in depth-sensing and modulus mapping mode allow a complete and self-consistent physical analysis of the damage induced by the direct exposure of porous OSG films to different plasma ambients in reactive ion etching mode. We demonstrate for the chosen dielectric that the characteristics of the damage regions such as density and elastic modulus are very similar regardless of the reducing or oxidizing nature of the plasma. Nevertheless, the physical depth of the damage region shows large variation. Capabilities and limitations of each of the chosen analysis techniques are also discussed. [ABSTRACT FROM AUTHOR]

Abstract: Surface hydrophilisation and effective k-value degradation have been reported in literature after direct-CMP of high porosity SiOC films (without a protective capping layer). In the sequel, attempts to restore ultra low-k (ULK) material initial properties after a standard CMP and post-CMP cleaning process are reported. Annealing treatment has shown to be valuable to remove residual organics and water absorbed at the ultra low-k material surface after direct-CMP. However, as the hydrophilicity of the polished surface remains unchanged, it does not prevent moisture uptake, leading to an increase in k-value with time. Therefore, in order to restore hydrophobic properties and to stabilize the surface in time, three silylating agents – containing chlorosilane reactive groups (–SiMe n Cl3−n ) as well as hydrophobic methyl functions (–CH3) in their structure – have been employed in liquid, gas or dense CO2 phases on the CMP-induced damaged ULK layers. While each of these organic treatments is efficient to restore hydrophobicity on post-CMP ULK surfaces, only one of them proved to be able to keep the k-value low (comparable to the ULK pristine k-value) and stable in time, without inducing significant change in porosity of the ULK material. [Copyright &y& Elsevier]

Abstract: A sacrificial material deposited by CVD is used to demonstrate air gap formation in single damascene structures by UV-assisted decomposition. The material is removed through a porous low-k cap, after completion of the damascene scheme. The porosity of the low-k cap is shown to be critical for efficient air gap formation. Capacitance reduction of ∼50% is demonstrated using this technique compared to conventional SiOC(H) interconnects and an effective dielectric constant of 1.7 is extrapolated. [Copyright &y& Elsevier]

Abstract: The introduction of ultra low-k materials in copper technology has been much slower than anticipated in the ITRS Roadmap. The introduction of porosity in low-k materials has increased the level of complexity tremendously. In this paper, the challenges appearing during the integration of ultra low-k dielectrics will be discussed, since a proper understanding of these issues is essential for downscaling of the interconnect system. The inferior mechanical and thermal properties were always identified as main showstoppers for low-k integration. However, the extreme vulnerability of porous low-k to produces-induced damage (accompanied with the loss of dielectric performance and reliability) demands a continuous innovation of materials, processes and integration approaches. [Copyright &y& Elsevier]