Two new types of silsesquioxanes, (HSiO 3/2 ) x [( t BuO)SiO 3/2 ] z or T H Q and (HSiO 3/2 ) x (RSiO 3/2 ) y [( t BuO)SiO 3/2 ] z or T H T R Q (R ) octadecyl), were synthesized and studied as low-k dielectric materials for electronic applications. The materials were prepared by cohydrolysis and condensation of alkoxy monomers, (AcO) 2 Si(O t Bu) 2 , HSi(OEt) 3 , and CH 3 (CH 2 ) 17 Si(OMe) 3 . Spectroscopic data supported retention of tertiary alkoxy groups [( t BuO)SiO 3/2 or ( t BuO) 2 SiO 2/2 ] and presence of silanol. The molecular weight of (HSiO 3/2 ) x [( t BuO)SiO 3/2 ] z increased with the T/Q ratio, while that for (HSiO 3/2 ) x (RSiO 3/2 ) y [( t BuO)SiO 3/2 ] z exhibited less dependence on composition. The tert butoxy groups were eliminated in both materials at low temperatures (<450 °C), and subsequent decomposition of octadecyl group (R) in (HSiO 3/2 ) x (RSiO 3/2 ) y -[( t BuO)SiO 3/2 ] 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 (HSiO 3/2 ) x [( t BuO)SiO 3/2 ] z determined by nitrogen sorption porosimetry increased with increasing Q content up to 0.313 cm 3 /g or 38% porosity by volume. The porosity for (HSiO 3/2 ) x (RSiO 3/2 ) y [( t BuO)SiO 3/2 ] z ranged from 32 to 54% (0.349-0.701 cm 3 /g), which represented an ∼10% increase over (HSiO 3/2 ) x [( t BuO)SiO 3/2 ] z . Thin films prepared from (HSiO 3/2 ) x [( t BuO)SiO 3/2 ] z exhibited a modulus between 10 and 19 GPa, but had a high dielectric constant due to residual silanol. Incorporation of RSiO 3/2 group allowed for formation of porous materials with low silanol contents. The dielectric constant and modulus of (HSiO 3/2 ) x (RSiO 3/2 ) y -[( t BuO)SiO 3/2 ] z were in the range of 1.7-2.6 and 1.8-4.7 GPa, respectively.
Silicone resins were investigated as a replacement of silica filled organic polymers for microelectronic packaging. Self‐curable silicone resins containing up to 40 mol% of in‐situ generated silica‐like species were prepared by a novel process involving controlled hydrolysis‐condensation of SiH moieties without gelation. These in‐situ Q filled resins are stable and easy to process compared to post‐filled organic polymers. The thermo‐mechanical properties upon self‐addition and condensation cure of the in‐situ filled silicone resins are superior to conventional addition and condensation cured silicone resins and are in the range of organic polymers with the added advantage of high thermal and moisture resistance critical in microelectronic. Storage modulus and plateau modulus as high as 3.5 GPa with a very low fall in modulus below 5% were demonstrated. Coefficients of thermal expansion were as low as 55 to 65 ppm/K in the application temperature up to 170 °C.
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