Evaluation of Materials for Fan-Out Panel Level Packaging (FOPLP) Applications

Present study focuses on lithography evaluation of dielectric and resist materials for panel level fan out fabrication. All experiments have been conducted on Gen 3 (550x650mm) size glass panels. Slit coating and Laser Direct Imaging (LDI) methods has been used for coating and exposure of dielectric and resist materials respectively. In this study, two positive tone photo definable polymer dielectric (PD) materials and one positive tone photo resist (PR) have been evaluated for process ability in terms of coating uniformity and pattern resolution capability. A special test structures lay out with different size vias and line traces of various Line Width/ Line Space (LW/LS) has been designed for these materials evaluation. Slit coating process was optimized and achieved target coating of $7 \mu {\mathrm{ m}}$ thick PR layer and $10 \mu {\mathrm{ m}}$ thick PD layer with TTV of 1% and 3% respectively. Extensive DOE has been carried out to optimize the LDI parameters like exposure dose, focus and laser power to identify optimum conditions for fine LW/LS patterns and smallest via openings on PR and PD layers respectively. Experiment results revealed that fine LW/LS of $2 \mu {\mathrm{ m}}/2 \mu {\mathrm{ m}}$ in $7 \mu {\mathrm{ m}}$ thick PR layer and smallest vias of $3 \mu {\mathrm{ m}}$ openings in $10 \mu {\mathrm{ m}}$ PD layers can be achieved using optimized LDI process. The detailed process parameters optimization and material evaluation results have been reported in the subsequent sessions of this paper.