Study of Low-k Films and Anti-Corrosion Films Prepared from Pure-Silica-Zeolite Nanoparticles
Date Issued
2014
Date
2014
Author(s)
Li, Ting-Yi
Abstract
Pure-silica-zeolite (PSZ) Mobil-Five (MFI) and MFI-like noncrystalline silica (NCS) nanoparticles synthesized using tetrapropylammonium hydroxide (TPAOH) as a structure directing agent were produced via hydrothermal processes, and those nanoparticles were applied to fabricate porous silica low dielectric constant (low-k) films and anti-corrosion films in this dissertation.
When hydrothermally producing the PSZ MFI nanoparticle suspensions, effect of wall thickness of autoclave reactor is studied. Heat transfer simulation indicates that decreasing the wall thickness increases temperature rising rate in the reactor at initial stage of hydrothermal synthesis. An increased initial temperature rising rate produces the suspensions with large particle size. That is, initial temperature rising rate in the reactor affects significantly on sizes of the PSZ MFI nanoparticles at the final stage of hydrothermal synthesis.
Porous silica low-k films are prepared from coating solutions containing the nanoparticles and surfactants. Effects of TPAOH concentration, hydrophobic tail length of polysorbate surfactants, and hydrothermal time on coating solutions to produce low-k films are studied. Because increasing the TPAOH concentration or decreasing the hydrothermal time increases the number of silanol groups (or hydrophilic property) on the particles and because increasing the tail length decreases hydrophilic property of the surfactants, coated films from coating solutions containing these particles and surfactants with various hydrophilic properties are substantially different. Thus, their effects on low-k film properties (i.e., k value, leakage current density, porosity, surface morphology, hardness, and elastic modulus) are investigated. Using nanoparticles or surfactants with a low hydrophilic property produces films with high porosity. Additionally, particles with few silanol groups are preferable to prepare films with ultra-low-k values. However, when the hydrophilic property of particles is too low, large micelle aggregates that form in coating solutions result in large holes on film surfaces after the calcination. These large holes can cause extremely high leakage current densities and high k values >2. Further, mechanical strength of films decreases as the number of silanol groups on particles decreases. Additionally, surfaces of the resulting films with poor mechanical strength have some nano-sized cracks. Conversely, increasing hydrophilicity of surfactants increases their interaction with silica particles, resulting in a decreased number of remaining silanol groups in films after hexamethyldisilazane (HMDS) surface treatment. The small number of remaining of silanol groups can cause films to have low k values, low leakage current densities, and high breakdown fields.
When using a short hydrothermal time to synthesize the nanoparticle suspensions, only MFI-like NCS nanoparticle suspensions are produced. The MFI-like NCS particles with small size of about 5 nm are attempted to prepare dense silica coatings for protection of aluminum from corrosion. However, as coating thickness increases, the number and size of cracks increase. Cracks on films are a result of thermal expansion mismatch between silica particles and aluminum substrate. To produce thick and crack-free films as anti-corrosion coatings, MFI-like NCS suspensions were mixed with an organosilane solution to develop hybrid coating solutions. Anti-corrosion ability increases as the suspension loading increases. Hybrid films with smooth surface and thickness of about 4 μm have good anti-corrosion ability. Additionally, the films have pencil hardness of 3H, which is comparable with that of a commercial product of NanoMateR 5200.
Subjects
孔洞型二氧化矽薄膜
低介電薄膜
低介電常數
MFI沸石
MFI-like非結晶氧化矽
四丙基氫氧化銨
水熱程序
抗腐蝕薄膜
有機-無機混成薄膜
Type
thesis
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