Colloidal processing of polymer ceramic nanocomposite integral capacitors

Polymer ceramic composites form a suitable material system for low temperature fabrication of embedded capacitors appropriate for the MCM-L technology. Improved electrical properties such as permittivity can be achieved by efficient filling of polymers with high dielectric constant ceramic powders such as lead magnesium niobate-lead titanate (PMN-PT) and barium titanate (BT). Photodefinable epoxies as the matrix polymer allow fine feature definition of the capacitor elements by conventional lithography techniques. The optimum weight percent of dispersant is tuned by monitoring the viscosity of the suspension. The dispersion mechanism (steric and electrostatic contribution) in a slightly polar solvent such as propylene glycol methyl ether acetate (PGMEA) is investigated from electrophoretic measurements. A high positive zeta potential is observed in the suspension, which suggests a strong contribution of electrostatic stabilization. By optimizing the particle packing using a bimodal distribution and modified processing methodology, a dielectric constant greater than 135 was achieved in PMN-PT/epoxy system. Suspensions are made with the lowest PGMEA content to ensure the efficiency of the dispersion and efficient particle packing in the dried film. Improved colloidal processing of nanoparticle-filled epoxy is a promising method to obtain ultra-thin capacitor films (<2/spl mu/m) with high capacitance density and improved yield. Capacitance of 35 nF/cm/sup 2/ was achieved with the thinnest films (2.5-3.0 /spl mu/m).     

Polymer-ceramic nanocomposite capacitors for system-on-package (SOP) applications

This work focuses on optimizing the dispersion of nanosized ceramic particles for achieving higher dielectric constant, thereby higher capacitance density in polymer/ceramic nanocomposites. It has been observed that high solids loading leads to entrapment of porosity in the microstructure which lowers the effective dielectric constant of the films. The amount of solvent in the suspension and the speed at which spin coating was performed were found to impact the dielectric constant of high filler content nanocomposites. The interplay between the rheological properties of the suspension and processing parameters such as solvent content and coating speeds and its impact on the dielectric properties of the film are discussed. Porosity of thin film composites was measured for the first time to study the impact of these processing parameters. Powders of different particle sizes were mixed to obtain bimodal particle size distribution in order to increase the packing density of the composite. Packing density was improved by modifying the dispersion methodology. A nanocomposite with dielectric constant as high as 135 was obtained for the first time in the low-cost printed wiring board compatible epoxy system. A capacitance densities of /spl sim/35 nF/cm/sup 2/ on a nominal 3.5 micrometer films was achieved on PWB substrates with high yield. The manufacturability of these formulated nanocomposites and their applications as decoupling capacitors have been tested using a large area (300 mm /spl times/ 300 mm) system-on-package (SOP) chip-to-chip communication test vehicle.