Polarization Effect in Laser Processing of Fine Pitch Link Structures for Advanced Memory Designs

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Abstract
Metal fuses for laser redundant links have been widely used for years in laser repair application to enhance yield. Shrinking design rules in IC fabrication have necessitated decreased fuse pitches in the redundancy circuitry. Current infrared lasers are facing the 2 mum pitch barrier due to the diffraction limited spot size and depth of focus capabilities. In this paper, we present experimental results showing how we have achieved successful laser cut processes of future metal fuse structures down to 1.0 mum pitch using a combination of the small spot of short wavelength laser and the polarization effect to tightly pitched neighbor structures. Inline polarization with link length minimizes the adjacent link damages and thus improves the energy process window for robust cutting. Electrical measurement data of metal link structures with various pitches, metal width and top passivation thicknesses shows the importance of controlling of top oxide thickness on the fine pitch structure. This enabling technology provides a viable production solution for laser fuse processing down to 45-nm node technology and below.

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