Analysis of photoresist edge bead removal using laser light and gas
2010
Wafer edge defects are currently considered a major problem as they negatively impact device yields in integrated circuit
manufacturing, especially in immersion lithography. A primary source of edge defects is from particles of photoresist
originating from the edge bead of resist caused by spin coating. In this paper, photoresist edge bead removal (EBR) is
studied in a series of experiments using a laser and gas cleaning system. One goal of the experiments was to reduce the
edge exclusion by gradually reducing the area cleaned by the laser and gas system. Reduction of EBR width will increase
die yield. A number of varying exposure algorithms were tested, and are described along with microscope and SEM
photos of the resulting edge geometry and surface condition. Another goal of these experiments is time-efficient removal
of thick edge beads, a problem for conventional expose/develop methods. A matrix of varying laser parameters and gas
types was run to produce a best-known-method (BKM) to meet these goals.
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