Morphology and properties of low dielectric constant polymeric films with electrophoresis induced gradient close-pore distribution

Low dielectric constant films with gradient pore distributions were prepared by the electrophoresis method. Anionic charged polymeric hollow particles were dispersed in the UV-curable monomer. These particles were attracted toward the anode and fixed after UV curing. In low-k applications, the dense skin is necessary for the porous film to prevent Cu ion migration. Without introducing the traditional pore sealing process, a non-porous skin was created on the surface of the low-k film. The incorporation of hollow particles effectively decreased the dielectric constants of the films. The non-porous skin also increased the nanoindentation hardness and modulus near the film surface. The gradient distribution of the close pores can be arranged vertically or horizontally by the electrophoresis method. These porous textures cannot be prepared by the phase-inversion method. The influences of the pore size, pore distribution, pore concentration and baking procedure on the cross-sectional morphology and dielectric properties of the cured films were studied.