Studying the effects of processes on crystalline porous low-k silica thin films
Date Issued
2008
Date
2008
Author(s)
Teng, Chin-Lin
Abstract
Low-dielectric-constant (low-k) material is a critical request in semiconductor industry. Porous silica possesses advantage of low dielectric constant, good thermal stability, and easily-preparation procedures. Effects of baking conditions, hydrothermal process, centrifugation, and base treatment on the properties of crystalline porous low-k silica thin film were studied in the research. Some results can be presented while studying the effect of heat treatment. The thin film prepared with lower baking temperature will possess more porous structure, thus it will have lower k value but poorer mechanical strength. While the hydrothermal process time is longer, the crystallinity is better; however the coating quality is poor. We propose long-time centrifugation process and base treatment to solve coating problem. In this part of research, we establish some trend. First, the better crystallnity would bring about lower k-value but poorer mechanical strength. Second, adding more surfactant would lead lower k-value but make mechanical strength poor. Third, centrifugation could diminish the roughness of thin film and consequently lower the k-value; however excessive centrifugation process would increase the k-value. Fourth, adding base treatment into process and using ammonium as base source, its improvement is unobvious; and altering TEAOH as base source would lead high k-value and poor mechanical strength. Base on results of experiment, we make a discussion about nanozeolite reacting with surfactant. In the beginning, silica species surround TPAOH, and then the center will crystallize slowly. However, tween80 competed with TPAOH to grab Si-OH species. As the results, adding surfactant while crystallinity is poor would induce micropore structure to be taken apart. Because crystal structure would not react with surfactant, crystalline micropore structure would not be destroyed when crystallinity advanced. The best thin film prepared in the research possesses k value =1.83, hardness =1.39GPa, and elastic modulus =12.25GPa.
Subjects
low dielecric constant
thin films
surfactant
zeolite
porous material
crystallinity
centrifugation
Type
thesis
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