Wafer Level Warpage Modelling and Validation for FOWLP Considering Effects of Viscoelastic Material Properties Under Process Loadings

Wafer level warpage model was developed for the 12 inch mold-first FOWLP wafer with model change technique. The sequential process loadings of post-mold curing (PMC) (150 degrees C), warpage correction (150 degrees C and pressure), dielectric curing (190 degrees C), seed layer PVD (160 degrees C) and blank Cu electroplating were applied. The time and temperature dependent material properties of EMC and dielectric were considered in the model. The warpages of the 12 inch mold-first FOWLP wafer after the sequential processes were measured by the Nikon surface profiler and correlated with the predicted wafer warpage results. The predicted warpage results have good correlation with the experimental results. The warpage of FOWLP wafer was reduced after warpage correction. However, the warpage will increase after dielectric coating and curing. After PVD process, warpage will increase further. The viscoelastic material properties of EMC and dielectrics are critical for the warpage prediction under the process loadings. Only considering elastic material properties, the warpage behavior cannot be predicted. The developed wafer level warpage model considering time and temperature dependent material properties can be used for the warpage optimization and control for FOWLP development.