Takeharu Motobe

Novel 200 degC curable positive tone poly(benzoxazole) materials

Photo-definable polyimides and polybenzoxazoles (PBO) have been widely used as dielectrics for re-distribution layers in wafer level chip size packages. These materials can simplify the manufacturing process and ensure high reliability owing to their good mechanical properties and high thermal stability. For next generation electronic components fabricated by utilizing advanced packaging technologies such as 3D-stacking using TSV, package-on-package, fan-out WL-CSP etc., the most important requirements for dielectric materials are high lithographic performance, high adhesion to Cu RDL and high chemical resistance. The improvement in lithographic performance of conventional PBOs by re-designing the photo-definable components has already been published. In this paper, the enhancement of Cu adhesion and chemical resistance obtained by re-designing key components of the formulation that include the photo-initiator and cross-linker will be reported. As a result, strong Cu adhesion and high chemical resistance was obtained when cured at temperatures <; 200 °C.

Evaluation of fan-out wafer level package using 200 °C curable positive-tone photodefinable polybenzoxazoles

Polyimides (PI) and polybenzoxazoles (PBO) have good heat resistance, mechanical properties and electrical insulation. Therefore, they have been widely used as buffer coating and interlayer dielectrics with protection property for electric applications. Recently, fan-out wafer level package (FOWLP) has been attracting attention, because it has advantages of multi-pin, thinner and interposer-free. In this application, it is preferable that the curing temperature of PI and PBO is less than 300 °C for reducing the thermal damage of semiconductor devices and packaging materials. To meet the requirement of lower curing temperature, HD MicroSystems has developed new PBO named HD-8940 designed to satisfy 200 °C curing process. In this study, we evaluated reliabilities of HD-8940 in FOWLP, assembling two types of test element grope (TEG). We also simulated thermal stress during reliability test by finite element method. Finally, we confirmed the applicability of HD-8940 to FOWLP.

Recent progress in low temperature curable photosensitive dielectrics

Hitachi Chemical DuPont MicroSystems (HDMS) has been developing 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 wafer level packaging. These materials offer an easy manufacturing process as well as ensuring high reliability in semiconductor packages such as fan-out wafer level packaging (FOWLP). Currently, dielectrics for FOWLP applications are cured at around 230°C. However, even lower cure temperatures are now required due to the limitations in heat resistance of packaging materials, a reduction in warpage of re-constituted wafers as well as yield improvement with embedded memory ICs. To meet these challenges, HDMS has been focusing on the development of a low temperature curable PI and PBO that can also achieve high resolution and excellent cured film properties. In this paper, recent progress in our latest PI and PBO materials will be introduced.