Low Temperature Curable Photo-sensitive Insulator

In recent years, novel electronic products have become dramatically smaller and more highly functionalized. Based on these market trends, packaging structures for semiconductors are also required to become smaller, thinner and more complicated. To satisfy various requirements, packaging technologies such as WL-CSP, FO-WLP. 2.5D interposer, 3D-TSV, and so on, are used. For these packaging structures, the photo-sensitive organic materials used for buffer coating, passivation layers, and insulators for re-distribution are required to exhibit low temperature curability and low residual stress. To meet these requirements, we have developed a low temperature curable (around 200 degrees C) photo-sensitive insulator. The design concept of our photo-sensitive insulators is based on phenolic resins as the main component to perform good lithography and cross-linkers containing epoxy functional units. Moreover, our photo-sensitive insulators contain naphtoquinone diazide (DNQ) compounds commonly used in positive tone resists. Specifically, we have developed new phenolic resins containing flexible units. Our photo-sensitive insulators containing the new polymer showed low residual stress, low elastic modulus, good chemical resistance and good lithography performance.