| Abstract
| - Two new types of stable silsesquioxanes, (HSiO3/2)x[(tBuO)SiO3/2]z and (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z, were synthesized and studied as low-k dielectric materials. The dielectric constant and modulus of the porous films derived from (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z were in the range of 1.7−2.6 and 1.8−4.7 GPa, respectively.
- Two new types of silsesquioxanes, (HSiO3/2)x[(tBuO)SiO3/2]z or THQ and (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]zor THTRQ (R = octadecyl), were synthesized and studied as low-k dielectric materials for electronicapplications. The materials were prepared by cohydrolysis and condensation of alkoxy monomers,(AcO)2Si(OtBu)2, HSi(OEt)3, and CH3(CH2)17Si(OMe)3. Spectroscopic data supported retention of tertiaryalkoxy groups [(tBuO)SiO3/2 or (tBuO)2SiO2/2] and presence of silanol. The molecular weight of(HSiO3/2)x[(tBuO)SiO3/2]z increased with the T/Q ratio, while that for (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]zexhibited less dependence on composition. The tert butoxy groups were eliminated in both materials atlow temperatures (<450 °C), and subsequent decomposition of octadecyl group (R) in (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z occurred through cleavage and re-distribution of carbon−carbon bonds (430−550 °C).Heating at 450 °C for 2 h afforded porous solids. The total pore volume of materials derived from(HSiO3/2)x[(tBuO)SiO3/2]z determined by nitrogen sorption porosimetry increased with increasing Q contentup to 0.313 cm3/g or 38% porosity by volume. The porosity for (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z rangedfrom 32 to 54% (0.349−0.701 cm3/g), which represented an ∼10% increase over (HSiO3/2)x[(tBuO)SiO3/2]z.Thin films prepared from (HSiO3/2)x[(tBuO)SiO3/2]z exhibited a modulus between 10 and 19 GPa, buthad a high dielectric constant due to residual silanol. Incorporation of RSiO3/2 group allowed for formationof porous materials with low silanol contents. The dielectric constant and modulus of (HSiO3/2)x(RSiO3/2)y[(tBuO)SiO3/2]z were in the range of 1.7−2.6 and 1.8−4.7 GPa, respectively.
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