Effects of UV cure on glass structure and fracture properties of nanoporous carbon-doped oxide thin films

Gage, David M.; Stebbins, Jonathan F.; Peng, Luming; Cui, Zhenjiang; Al-Bayati, A.; MacWilliams, K.P.; M’Saad, Hichem; Dauskardt, Reinhold H.

doi:10.1063/1.2968438

Cited by 33 publications

(27 citation statements)

References 26 publications

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“…This was experimentally confirmed by Gage and co-authors, who showed that UV cure exposure results in a higher degree of film connectivity in the material and significantly enhances the interfacial adhesion strength, but barely influences the fracture toughness of PECVD carbon-doped oxide films. 36 H. Lin and co-authors 28 and Y. Lin and co-authors 29 demonstrated that the fracture energy of OSG materials, measured under mode-I condition using double-cantilever beam technique, scales linearly with the total number density of the two main networking bonds in an OSG material ( Figure 6). 28 This is because fracture of these materials is a bond breaking process and the energy dissipated during fracture scales with the number of broken networking bonds and with the energy of the bonds.…”

Section: Impact Of Network Structure and Uv Radiation On Mechanical Smentioning

confidence: 99%

Mechanical Stability of Porous Low-k Dielectrics

Vanstreels

Baklanov

2014

ECS J. Solid State Sci. Technol.

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This paper reviews the mechanical and fracture properties of porous ultralow-k dielectrics with the focus on chip package interaction related issues. It is shown that the mechanical and fracture properties of porous ultralow-k dielectric films are closely linked with porosity, pore morphology, network structure and deposition technology, while their fracture properties are also sensitive to reactive species in the environment. The survivability of low-k dielectrics upon integration, package assembly and subsequent reliability tests is therefore a combination of their mechanical stability, fracture properties, the specific mechanical or thermo-mechanical load and environmental effects. For the past three decades, the semiconductor industry has been improving the performance of microelectronic devices and the functionality of advanced integrated circuits through the continuous scaling of integrated circuits and the maximization of transistor density.1 Consequently, this encourages the introduction of new materials, processes, chip designs, and packaging strategies into micro-/nano-electronic products. Among these material innovations are insulating materials with a dielectric constant (k) less than that of SiO 2 , so called low-k dielectrics. During the last 15 years, various materials and methods have been developed for fabricating low-k dielectric films, among which the plasma enhanced chemical vapor deposition (PECVD) technology of porous organosilicate glasses (OSG) is the most popular due to its better compatibility with the technological needs.2-5 The reduction in k for low-k dielectrics is being pursued through the introduction of controlled levels of porosity. However, finding a good low-k material has proven to be much more challenging than first expected due to a number of integration and reliability issues.1 Besides the need of being compatible with the different lithography, etching, stripping and cleaning processes that are used in state-of-the-art integration schemes, they must also have sufficient mechanical strength to withstand the high shear stresses as well as harsh chemical environments that are involved during the chemical mechanical polishing process without cohesive or adhesive failure occurring.6-8 On top of that, since low-k dielectrics exhibit intrinsic tensile stresses and have increased coefficients of thermal expansion compared to SiO 2 , thin film cracking and adhesion are serious thermal-mechanical reliability issues for low-k dielectric materials (Figure 1). 9,10 Thermo-mechanical deformation of the package during package assembly and subsequent reliability tests can induce large local stresses that can initiate and propagate cohesive and/or adhesive cracks in different back-end of line (BEOL) layers.11 Therefore, a careful characterization of the mechanical integrity of potential new low-k candidates is required to integrate these new materials and Cu interconnects and to assure reliability during chip packaging and under field conditions. In the microelectronics industry, the elas...

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Section: Impact Of Network Structure and Uv Radiation On Mechanical Smentioning

confidence: 99%

Mechanical Stability of Porous Low-k Dielectrics

Vanstreels

Baklanov

2014

ECS J. Solid State Sci. Technol.

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“…158 UV curing technologies have enabled some reduction in dielectric permittivity (through introduction of interconnected porosity) without a significant reduction in Young's modulus. [159][160][161][162][163][164] A survey of the literature suggests that low-k ILDs with Young's moduli of 5-10 GPa have been successfully integrated into high volume manufacturing interconnect fabrication processes. 24,25,148 Similar to low-k ILDs, low-k DB materials also exhibit reduce mechanical properties relative to the PECVD a-SiN:H films originally employed.…”

Section: -122mentioning

confidence: 99%

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

King

2014

ECS J. Solid State Sci. Technol.

133

115

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Over the past decade, the primary focus for improving the performance of nano-electronic metal interconnect structures has been to reduce the impact of resistance-capacitance (RC) delays via utilizing insulating dielectrics with ever lower values of dielectric permittivity. The integration and implementation of such low dielectric constant (i.e. low-k) materials has been fraught with numerous challenges. For intermetal and interlayer (ILD) low-k dielectrics, these challenges have been largely associated to integration with metal interconnect fabrication processes and well documented and reviewed in the literature. Although equally important, less attention has been given to other low-k dielectrics utilized in metal interconnect structures that are commonly referred to as low-k dielectric barriers (DB), etch stops (ES), and/or Cu capping layers (CCL). These materials present numerous challenges as well for integration into metal interconnect fabrication processes. However, they also have more stringent integrated functionality requirements relative to low-k ILD materials that serve only a basic purpose of electrically isolating adjacent metal lines. In this article, we review the integration challenges and associated integrated functionality requirements for low-k DB/ES/CCL materials with a focus on the current status and future direction needed for these materials to facilitate both Moore's law (i.e. More Moore) and More than Moore scaling.

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“…The UV curing was designed to promote cross-linking of the Si-O network bonds and accelerate porogen removal resulting in the formation of nanometer size pores within the film. 11 Diffusion coefficients of linear alkanes with various chain lengths from hexane (C 6 H 14 ) to hexadecane (C 16 H 34 ), and linear fatty alcohols from hexanol (C 6 H 13 OH) to undecanol (C 11 H 23 OH), were measured using the lateral solvent diffusion technique. 9,12 To directly observe liquid penetration in the plane of the nanoporous film, the top surface of the film was first hermetically sealed with an optically transparent SiN layer.…”

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confidence: 99%

Molecular Mobility under Nanometer Scale Confinement

Kim

Dauskardt

2010

Nano Lett.

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The mobility of organic molecules under nanoscale confinement differs greatly from that in the bulk. In this study we show that the conventional free volume dependent mobility relationship explained by the free volume theory of diffusion breaks down for diffusion of linear alkane molecules in organosilicate films with connected nanoporosity. Alkane mobility under such nanoscale confinement was observed to decrease with chain length and was lower than that reported in the bulk. While the activation energy for diffusion was similar to that in the bulk, it was found to decrease with chain length exactly opposite to the trend observed in the bulk. This suggests an increasing molecular free volume with chain length. The effects of molecular polarity and pore size on diffusion were also demonstrated. Molecular mobility was found to be suppressed with increasing molecular polarity and decreasing pore size. KEYWORDS Molecular mobility, nanoporous, nanoconfinementT he mobility of organic molecules when confined at nanometer length scales differs greatly from properties in the bulk. 1,2 We demonstrate that linear alkane molecules exhibit a free volume dependent mobility under nanoconfinement that is exactly opposite to the conventional relationship observed in the bulk. As described by the free volume theory of diffusion, 3-5 linear alkane molecules typically exhibit a lower free volume and mobility with longer chain lengths. 6 However, under nanoscale confinement in nanoporous organosilicate films, we found the activation energy decreases with increasing chain length suggesting an increase in the molecular free volume.The effects of such nanoscale confinement on molecular mobility are attracting increasing interest for applications such as pore filling in solid-state dye-sensitized solar cells 7 and molecular sieving in nanofilters. 8 However, there is a remarkable paucity of molecular mobility data under nanoconfinement, and fundamental descriptions are complicated not only by the effects of the confinement on molecular interactions, conformation, and free volume but also by molecular interactions with the confining surfaces. We recently showed that unentangled surfactant molecules in the bulk become entangled with adjacent molecules when diffusing through interconnected nanopores (d ∼ 2.1 nm) and exhibit signatures of reptation. 9 We also discussed the importance of molecular interactions with pore surfaces. Other studies have shown that long polystyrene molecules with molecular weight above that needed for entanglement diffuse faster in cylindrical alumina nanopores (pore diameter d ∼ 15 nm) due to lower molecular entanglement associated with fewer chains present in the confined region. 10 According to the free volume theory of diffusion, 3-5 the two ends of a linear chain molecule provide a contribution to free volume into which segments of adjacent molecules can move. The fractional free volume, f, provided by the chain ends is inversely proportional to the chain length or the molecular weight, M, and incre...

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Effects of UV cure on glass structure and fracture properties of nanoporous carbon-doped oxide thin films

Cited by 33 publications

References 26 publications

Mechanical Stability of Porous Low-k Dielectrics

Mechanical Stability of Porous Low-k Dielectrics

Dielectric Barrier, Etch Stop, and Metal Capping Materials for State of the Art and beyond Metal Interconnects

Molecular Mobility under Nanometer Scale Confinement

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