Lithography challenges for fan-out

An article written by Mark LaPedus for SEMICONDUCTOR ENGINEERING – Advanced packaging moves into high-volume mobile markets, but requires more sophisticated equipment and lower-cost processes. Higher density fan-out packages are moving toward more complex structures with finer routing layers, all of which requires more capable lithography equipment and other tools.

The latest high-density fan-out packages are migrating toward the 1µm line/space barrier and beyond, which is considered a milestone in the industry. At these critical dimensions (CDs), fan-outs will provide better performance, but there are several manufacturing and cost challenges to reach and break the 1µm barrier. Moreover, at this point only a few customers require these high-end packages.

Nevertheless, fan-out packaging is gaining steam in high-volume markets. “Mobile continues to be one main growth driver for both low-density and high-density fan-out,” said John Hunt, senior director of engineering for ASE. “Automotive will start to pick up momentum, as we get fan-out qualified for grade 1 and 2. And server applications are seeing growth for the high-end market.”

A key part of a fan-out is the redistribution layer (RDL). RDLs are the copper metal connection lines or routing layers that electrically connect one part of the package to another. RDLs are measured by line and space, which refer to the width and pitch of a metal line… Full article


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