Cost Analysis of Lithography Options for Panel-Level Fan-Out Packaging

Panel-based fan-out packaging is a continuing topic of interest. The cost reduction associated with processing more die at one time by using a large panel instead of a smaller wafer is attractive, despite the challenges associated with the switch to panels. Those challenges include a lack of alignment within the industry on which panel size to pursue, new material and equipment requirements to support panels, and the fact that a panel may produce so many chips per panel that true high volume and high utilization may never be achieved.

Once these challenges are addressed, there are still questions to be answered about the process itself. There are a number of options to consider for the lithographic portion of the panel fan-out process. This paper will explore the following four options for the formation of the redistribution layer (RDL) on a panel: stepper, aligner, laser direct imaging, and laser ablation.

The paper will introduce the basic process flows for each technology, and the focus of the comparison will be on the costs associated with each lithographic option. Equipment cost, processing throughput, yield, and material costs (dielectric, photoresist, masks, etc.) will be considered. Multiple panel and package sizes will be analyzed. Key variables will be tested to evaluate the sensitivity of each assumption.

Activity based cost modeling will be used for this analysis. This is a bottom-up, detailed approach to cost that accounts for the many cost components associated with every step of the process flow, such as material, labor, and capital depreciation. The goal of this analysis is not to highlight one lithographic option as the best or worst choice, but to understand the cost drivers associated with all four potential choices.