Extreme High Aspect Ratio RDL Patterning with Low Temperature Curable Polyimide using Double Patterning Technology

In this paper, extreme high aspect ratio RDL patterning technologies using double patterning technology and low temperature curable polyimide is demonstrated. The extreme high aspect ratio patterning is realized by combination of 1st and 2nd patterning before curing, and was used to successfully form both trench and via patterns, as well as combination of via and trench. The aspect ratio was measured by cross-sectional observation of the resulting pattern using an electron microscope, and was found to be over 8 after curing. Finally, a PI film was formed using the double patterning technology, and a single curing step was applied to obtain a permanent film, with reliability evaluation performed using biased HAST and HTS test. Furthermore, the elongation at break and modulus were measured through stress-strain curve. The results of biased HAST and HTS, as well as mechanical property measurements, are promising. The PI permanent film formed by double patterning and obtained by single curing is homogenized, passes the reliability evaluation, and can be applied to actual devices.