Photodefinition and structure-property relations for polynorbornene based dielectric.

摘要

Polynorbornene based copolymer, poly[decylnorbornene-co-epoxidenorbornene], has been developed as a low dielectric constant dielectric. Decyl side chains are chosen to improve the mechanical properties, including modulus and elongation-to-break, of the polymer film while the epoxide side chains are selected to provide crosslinkable sites. By adding photoactive compounds, including the photoinitiator and sensitizer, the polymers are photodefinable.; In this study, the photochemistry of the polymer was studied and the photoinitiator and the sensitizer were selected based on their solubility, thermal stability, and reactivity. The photodefinition of the polymer was explored. The effects of copolymer composition, concentration of photoactive compounds, and processing conditions on photodefiniton were investigated. A mechanism based on the diffusion of photoactive compounds was proposed to explain the photodefinition properties of poly [decylNB-co-epoxideNB] copolymer. The chemical, electrical, and mechanical properties of the polymer films were studied as functions of copolymer compositions and processing conditions. In particular, crosslinking density, moisture absorption, multilayer capability, refractive index, dielectric constant, residual stress, modulus and coefficient of thermal expansion (CTE) were examined. Lower epoxideNB content results in lower moisture absorption, dielectric constant, modulus and residual stress but leads to poor multilayer capability. High crosslinking density lowers dielectric constant and CTE but causes high modulus and residual stress.