Spin-on Mesoporous Silica Films with Ultralow Dielectric Constants, Ordered Pore Structures, and Hydrophobic Surfaces

Yang, Chia-Min; Cho, A. T.; Pan, Fu‐Ming; Tsai, T. G.; Chao, Kuei Jung

doi:10.1002/1521-4095(200107)13:14<1099::aid-adma1099>3.0.co;2-0

Cited by 142 publications

(89 citation statements)

References 2 publications

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“…Such materials are synthesized typically by the traditional solgel process [3][4][5][6][7] or a template directed procedure. [8][9][10][11][12][13][14][15] Sol-gel derived silicas have a high porosity (60-90%) and offer a tunable k value, but their low mechanical stability, wide pore size distribution, and hydrophilicity limit their applications in microelectronic industry. Compared to sol-gel derived silica, surfactant-templated mesoporous silica has much more uniform and controllable pores.…”

Section: Introductionmentioning

confidence: 99%

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

Zhu

Müller

Lercher

2008

Adv Funct Materials

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Composite films with low dielectric constants (k) containing micro‐ and mesopores are synthesized from precursor solutions for the preparation of mesoporous silica and ethanolic suspensions of silicalite‐1 nanoparticles. The material contains silicalite‐1 nanoparticles (include nanocrystals and nanoslabs/intermediates) embedded in a randomly oriented matrix of highly porous mesoporous silica. Micropores result from the incorporated silicalite‐1 nanoparticles, while decomposition of the porogen F127 leads to additional mesopores. The porosity of the composite films increases from 9 to 60% with the increase in porogen loading, while in parallel the elastic modulus and hardness decrease. The elastic moduli of the films are in the range of 13–20 GPa. Hydrophobic surfaces of the composite films are obtained by introducing methyl triethoxysilane during the preparation of both precursor solutions, leading to the incorporation of CH3 groups in the final composite films. These methyl groups are stable up to at least 500 °C. A low k value of approximately 2 is observed for films cured at 400 °C in N2 flow, which is ideal for removing templates without decomposing methyl groups. Due to the intrinsic hydrophobicity of the material, post‐silylation is not required rendering the composite films attractive candidates for future low k materials.

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Section: Introductionmentioning

confidence: 99%

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

Zhu

Müller

Lercher

2008

Adv Funct Materials

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“…1 For a large range of applications such as low-k insulators, 2 antireflective coatings, 3 and optical sensors, 4 it would be desirable to produce mesoporous silicas in the form of thin films. Fabrication of thin films made of mesoporous silicas has conventionally been performed by liquid deposition methods such as epitaxial growth 5 or sol-gel method.…”

mentioning

confidence: 99%

Formation of Ordered Mesostructured Silica by Vapor Infiltration of Tetraethoxysilane into Hexagonally Arranged Surfactant–Catalyst Nanocomposites

Tanaka¹,

Maruo²,

Nishiyama³

et al. 2005

Chemistry Letters

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Hexagonally arranged surfactant-catalyst composites were treated only with tetraethoxysilane vapor, resulting in the formation of the silica mesostructures without phase transition.Syntheses of ordered mesoporous silicas require surfactant templates which form lyotropic liquid crystal phases in the solvent (usually water) and silicate species interacts with the surfactant and polymerizes to form a silica network encapsulating the surfactant micelles. 1For a large range of applications such as low-k insulators, 2 antireflective coatings, 3 and optical sensors, 4 it would be desirable to produce mesoporous silicas in the form of thin films. Fabrication of thin films made of mesoporous silicas has conventionally been performed by liquid deposition methods such as epitaxial growth 5 or sol-gel method. 6,7 Self-assembled surfactant-silicate composites are deposited from a liquid phase under acidic or basic conditions.On the other hand, we have reported a novel synthetic route of mesoporous silica films from vapor phase.8 Spin-on surfactant films were treated with tetraethoxysilane (TEOS) and hydrochloric acid (HCl) vapors in a closed vessel. Surfactant-silicate composites were rearranged from lamer to hexagonal structure under vapor infiltration.8a A drawback of the previous method is difficulty adjusting to a continuous vapor flow system because it is unavoidable that the TEOS/HCl vapor reacts and produces silicate particles not only on the film but also in gas phase.Here, we report an advanced vapor phase synthesis of mesoporous silica films using surfactant-catalyst composites. The objective of the present study is to prepare mesoporous silica films using only TEOS in vapor phase. Thus, the catalyst should be present in the surfactant film. Nonvolatile acids such as sulfuric acid (H 2 SO 4 ) and phosphoric acid (H 3 PO 4 ) must be a candidate as a catalyst instead of a volatile acid, HCl. Further, a novel phenomenon of the formation of surfactant-catalyst nanocomposite is presented here.First, we have performed vapor phase synthesis in a batch reactor using surfactant films containing different catalysts, such as H 2 SO 4 , H 3 PO 4 , HCl, and acetic acid (CH 3 COOH). Cetyltrimethylammonium bromide (CTAB) was used as a surfactant. The detailed synthesis and characterization methods are shown in the references and notes section. Figure 1a shows the XRD pattern of the spin-on film prepared using CTAB and H 2 SO 4 . The XRD pattern has two reflection peaks, indicating that the (100) family of planes of the hexagonal unit cell (d ¼ 4:5 nm) is oriented parallel to the surface of the substrate. The CTAB/H 2 SO 4 nanocomposite already has a hexagonal structure even before the TEOS vapor treatment. For reference, we prepared spin-on films using CTAB and volatile acid such as HCl or CH 3 COOH. The films have a lamellar structure with d ¼ 2:8 nm (Figures 1d and 1g). We consider that a large amount of H 3 O þ and SO 4 À could adsorb on the hydrophilic head of CTAB molecules. The bulky head of surfactants caused an arrangeme...

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“…[1][2][3][4][5] So far various strategies have been exerted to tailor new class of mesopore structures, to develop more convenient route to syntheses, and to understand formation mechanisms. [6][7][8][9][10][11][12] The so-called evaporation induced self-assembly (EISA) process, initiated by Brinker's group, has realized a facile fabrication of mesoporous silica thin films.…”

Section: Introductionmentioning

confidence: 91%

Derivation of Cubic and Hexagonal Mesoporous Silica Films by Spin-coating

2005

Bulletin of the Korean Chemical Society

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By introducing spin-coating method to the evaporation induced self-assembly (EISA) process, a simple and reproducible route in controlling the mesophase of silica thin films has been developed for the first time in this work. When a comparatively solvent-rich Si-sol (The atomic ratio of TEOS : F127 : HCl : H2O : EtOH = 1 : 0.006 : 0.2 : 9.2 : 30) was used as coating solution, the mesophase of resultant silica films was selectively controlled by adjusting the spin-on speed. The cubic mesophase has been obtained from the coating at a low rpm, such as 600 rpm, while the 2-D hexagonal mesophase is formed at a high rpm, such as 2,500 rpm. At a medium coating speed, a mixture of cubic and hexagonal mesophase has been found in the fabricated films. The present results confirm that the evaporation rate of volatile components at initial step is critical for the determination of mesopore structures during the EISA process.

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Spin-on Mesoporous Silica Films with Ultralow Dielectric Constants, Ordered Pore Structures, and Hydrophobic Surfaces

Cited by 142 publications

References 2 publications

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

Single Step Preparation of Novel Hydrophobic Composite Films for Low‐k Applications

Formation of Ordered Mesostructured Silica by Vapor Infiltration of Tetraethoxysilane into Hexagonally Arranged Surfactant–Catalyst Nanocomposites

Derivation of Cubic and Hexagonal Mesoporous Silica Films by Spin-coating

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