AVS 45th International Symposium
    Electronic Materials and Processing Division Wednesday Sessions
       Session EM2-WeA

Paper EM2-WeA6
Impact of Deposition Method on the Microstructural and Electrical Properties of Thin Film Silica Aerogels

Wednesday, November 4, 1998, 3:40 pm, Room 316

Session: Application of Scanning Probes to Electronic Materials
Presenter: C. Caragianis-Broadbridge, Trinity College
Authors: C. Caragianis-Broadbridge, Trinity College
L. Carmona, Trinity College
M. Farag, Trinity College
M. Guillorn, Trinity College
F. Stellabotte, Trinity College
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Aerogels are nanoporous materials with unique optical, thermal and electrical properties. Silica thin film aerogels demonstrate great potential as low dielectric constant insulators for interlevel dielectric applications. The focus of this research is the fabrication of thin film silica aerogels through a sol-gel process in conjunction with low-temperature supercritical extraction of CO@sub 2@. The microstructural and electrical properties of the aerogel were studied as a function of deposition method, using non-contact atomic force microscopy (nc-AFM), scanning and transmission electron microscopy (SEM and TEM) and capacitance-voltage (C-V) instrumentation. Alcogels, aerogel precursors, were prepared by hydrolysis and condensation of metal alkoxide, tetraethyothrosilicate, and were catalyzed by both acids and bases, according to a standard reaction. Before gelation, the solution was deposited on two substrates (bare Si and SiO@sub 2@ coated Si ) by two techniques (dipping and spin coating). After supercritical extraction of the CO@sub 2@, the resulting aerogels were characterized using AFM, SEM and TEM to obtain film uniformity, thickness and pore size. C-V data were acquired from metal insulator semiconductor (MIS) capacitors fabricated using the aerogel-coated wafers. This study reveals a correlation between deposition technique and uniformity of the aerogel. Thin films deposited by the spinning technique yield consistently smaller pore sizes, ranging between 150 and 440nm while producing a more uniform film thickness. C-V characterization of the aerogel MIS devices (for both substrates) indicates a high quality dielectric with minimal mobile, fixed and interface state charge. These measurements also reveal that these aerogel MIS capacitors possess a substantially lower dielectric constant (1.5-3.5 vs. 3.9) when compared with standard control SiO2 MOS devices.