IWLPC (Wafer-Level Packaging) Conference Proceedings

Full-Field Projection Scanner Pattering Resolution and Overlay Performance

Authors: Habib Hichri, Markus Arendt, Eric Nguyen, William Vis
Company: SÜSS MicroTec Photonic Systems Inc.
Date Published: 10/18/2016   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Photolithography has long been the key patterning technology for structuring inorganic and organic materials used in advanced packaging applications like flip-chip wafer bumping, electroplated gold, solder bumps, copper pillar technologies and redistribution layers. Photolithography is a key manufacturing process and cost contributor; the careful selection of the right exposure solution is critical to achieve the best possible cost structure in today’s industrial lithography applications.

We introduce a projection scanner, a scanning exposure system that uses large-area photo masks containing the full pattern image for the substrate. This allows the exposure of oversized dies without stitching, the production of non-repeatable features like test die structures, and seamless edge exposure. With a 1:1 projection lens, the scanning exposure technology maintains the full-field exposure advantages while providing high- resolution patterning performance. With the capability of varying NA from 0.07 to 0.14, a large depth of focus can be obtained, which enables superior pattern fidelity for thick resists compared to all other full-field exposure technologies. Full-field projection scanning is also a cost-effective technology for FOWLP applications. Based on the input of die placement data, a software optimization algorithm calculates a global X, Y, and ? offset and enables mask heating and cooling to compensate for errors introduced by mold compound expansion or shrinkage. We will present resolution data on different resists used for RDL and via for FOWLP showing capability to achieve aspect ratios of 5:1. In addition, details on the overlay capability of the projection scanner in thick resist are described and a Cost-of-Ownership comparison for Cu pillars applications is discussed.

Key Words: 

UV Scanner, Projection Lithography, Full-Field Exposure, Advanced Packaging, Exposure Resolution, FOWLP, Overlay In Thick Resist

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