Electrospun Nano-Fibrous Polymer Films with Barium Titanate Nanoparticles for Embedded Capacitor Applications

Continued miniaturization, increased performance, as well as increased reliability of microelectronics require development of new design and manufacturing methods. Embedding discrete passive components into the substrate has been identified as a solution capable of accommodating a portion of the future demands on microelectronics. As embedded passive components are fundamentally different from discrete passive components, development of new materials is necessary. These new materials must meet requirements on manufacturability, electrical performance, reliability and cost. This paper presents the results of a parametric study where electrospun nano-fibrous polymer films containing barium titanate nanoparticles have been evaluated as possible dielectric materials for embedded decoupling capacitor applications. The study is of experimental character and demonstrates a novel technique for manufacturing of embedded capacitor dielectrics. Samples were produced with a standard electrospinning setup using various processing parameters. The produced samples were electrically characterized by guidance of the ASTM standard, using a parallel-plate test fixture and a HP 4284A precision LCR meter. The properties studied were specific capacitance and dissipation factor. Two different polymers were studied, designated polymer A and polymer B. Successful samples of polymer A and polymer B loaded with barium titanate were electrospun and characterized. Scanning electron microscopy (SEM) was used to characterize the surface morphology of the electrospun films. Polymer A samples showed good mechanical performance with and without barium titanate loading. Polymer B samples demonstrated a contrary behavior having inferior adhesion to the substrate and being brittle. Inclusion of barium titanate nanoparticles into the samples, of both polymer A and polymer B, showed indications of improved adhesion to the substrate and higher Young´s Modulus of samples. It was shown that inclusion of ba- rium titanate into polymer A significantly changed the electrical properties of the films, increasing both specific capacitance and dissipation factor but also drastically reducing the frequency stability. The highest achieved specific capacitance for polymer A loaded with barium titanate was approximately 210 pF/cm². High dissipation factors, reaching up to 0.6, were observed. Characterization of electrospun pure polymer B revealed a frequency stable dielectric with a low dissipation factor in the order of 0.01. The achieved specific capacitance was approximately 54 pF/cm². Polymer B with 50.0 weight percent barium titanate nanoparticle loading, reaching values of 175 pF/cm², had a different dispersion showing less frequency stability. As previously, inclusion of particles led to increased dissipation factors, reaching values of approximately 0.7.