Mesoporous Silica Film Preparation by Novel Supercritical Fluid Extraction of Organic Templates
- PDF / 192,499 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 3 Downloads / 204 Views
L8.25.1
Mesoporous Silica Film Preparation by Novel Supercritical Fluid Extraction of Organic Templates Nobuyuki Kawakami, Takayuki Hirano, Yoshito Fukumoto and Yoshiyuki Nagase1 Electronics Research Lab., Kobe Steel, Ltd., Kobe, JAPAN; 1 Chemical & Environmental Technology Lab., Kobe Steel, Ltd., Kobe, JAPAN. ABSTRACT Supercritical fluid extraction (SFE) technique which enables to fabricate mesoporous film at low temperature has been developed. Meso-structure silica films are prepared by sol-gel process based on the self-organization of surfactant templates, and the organic templates are successfully extracted from the films by supercritical CO2 (sc-CO2) modified with hydrogen peroxide at 80 °C and 19.6 MPa. The extraction process is analyzed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy of the films. In order to discuss the feasibility of such films obtained at low temperature for electronics applications with low dielectric and low dielectric loss, the mechanical properties and the densities of the films are compared with various silica films prepared by different method. INTRODUCTION Surfactant-templated mesoporous films with highly ordered nanometer pores have attracted interests in diverse applications [1-6]. As for the electronics applications, the mesoporous materials are expected as the most promising candidates because of the low dielectric constants and low dielectric losses. In order to achieve the low dielectric constants, the surfactant templates have to be removed from the films to form pores, where it is pretty common to calcine at high temperature up to 500 °C. However, there are severe problems in such high temperature processes. One is the collapse of meso-structures which results in less porosity and higher dielectric constant. Others are the integration issues with other materials which are common in large scale integrated circuit of silicon devices. From the point of view of low temperature process to fabricate mesoporous films, we focus on supercritical fluid extraction (SFE) technique by using supercritical CO2 (sc-CO2). Carbon dioxide has the critical temperature of 31 °C and the critical pressure of 7.38 MPa, which are relatively lower values in materials. Although some techniques have been proposed to extract surfactant templates from powders of the mesoporous materials by using sc-CO2 modified with organic solvents such as methanol [7-9], the extraction throughput is quite low for practical uses. In this study, we have applied novel supercritical extraction process to prepare mesoporous films by using hydrogen peroxide solution as a modifier for sc-CO2. The mechanism of the extraction process and the mechanical properties of the films prepared at such a low temperature are discussed.
L8.25.2
EXPERIMENTAL Precursor solution was prepared under acidic condition in the following step. A starting mixture containing tetramethoxysilane (TMOS), water (pH=3) and ethanol was heated at 60 °C for 4 hours. The molar ratio was TMOS:water:ethanol=1:5:22.5. Under thi
Data Loading...
