Hitachi Chemical DuPont MicroSystems (HDMS) is a supplier of photosensitive negative-tone polyimides (PI) and positive-tone poly(benzoxazole)s (PBO) for use as protection layers in semiconductor ICs or as dielectrics for re-distribution layers in Fan-in or Fan-out wafer level packages. These materials offer an easy manufacturing process as well as ensuring high reliability in semiconductor packages. Recently, design rules and structures for next generation packages are advancing in order to achieve higher end multi-functionality. In accordance with this trend, next generation PIs and PBOs need to be developed to address new challenges that include lithographic properties, in-process compatibility and end-use properties and, in this paper, the latest material sets developed by HDMS will be introduced for advanced packaging applications. The 1 st material set is a low stress photosensitive PI designed especially as a protection layer in advanced process node semiconductor ICs where warpage reduction and better protection capability for fragile low-k layers are needed. The 2 nd and 3 rd material sets are designed as low temperature curable photosensitive PI and PBO for use as dielectrics in Fan-out wafer level package to provide good applicability with future device designs as well as high package reliability by improving resolution, cured film properties, adhesion, insulation reliability, and others.
We have newly developed non photosensitive and photosensitive polyimide having excellent electrical/mechanical properties. At first we have re-designed the polymer backbone in order to obtain low Dk and Df performance. As a result, our new non photosensitive PI achieved 2.9 of Dk at 20 GHz and 0.003 of Df at 20 GHz. In the next step, we selected the photo package of new PI carefully to maintain both low Dk/Df and high resolution. After that, we modified the photo initiator content, crosslinker content, and so on to have both high lithographic performance and high electrical performance. As a result, new photosentive PI cured at 320 °C showed 3.0 of Dk at 20 GHz and 0.006 of Df at 20 GHz. In addition, this material cured at 200 °C also showed 3.0 of Dk at 20 GHz and 0.009 of Df at 20 GHz. We also confirmed high mechanical properties of new PI. Elongation of this PI cured at >250 °C was approximately 70 %. From lithographic aspects, new PI achieved 15 μm L/S opening with 10 μm thickness.
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