New build-up insulation material based on cyclo-olefin polymer for high-performance IC packages

Abstract

A variety of mobile devices such as smart phones, ultra thin laptops, and tablet PCs have been introduced to the world wide market, and the demands are gaining momentum. In technological perspectives, the trend is going to increased amount of data transfer and further miniaturization of the devices for more comfortable browsing and convenience. With this trend, a build-up insulation film material that plays an important role in interposer substrates for semiconductor packaging, is required to have higher performance to cover 1) low transmission loss, 2) extremely small line and space (L/S) with an ultra-smooth copper surface, and 3) low coefficient of thermal expansion (CTE). It has been very challenging to develop build-up film materials to meet all requirements. We have developed a new build-up insulation film material based on a unique polymer, cyclo-olefin polymer (COP), which has much lower moisture absorption, Dk, and Df than standard epoxy-based materials. The COP-based build-up insulation material has shown outstanding performance; low tangent loss (0.0045 at 5 GHz), 4 um/4 um in L/S with ultra smooth surface for copper plating (Ra < 100 nm), copper peel strength (7 N/cm), and low CTE (17 ppm°C). It has also been found that the COP-based material demonstrates a wide process window for semi-additive process (SAP) that could help ensure easy manufacturing of interposer substrates besides the outstanding performance. For instance, as the material has strong chemical resistance against desmear solution, it does not significantly alter/damage surface roughness, plated copper peel strength, and via morphology. The newly developed build-up insulation material can be promising not only for bearing high electric performance to more sophisticated mobile devices, but also for contributing to high yield manufacturing thanks to easy processability, based on the new polymer, COP.