TrueAdapt™ to Enable Fine-Pitch Wiring on Flexible Fan-Out (FlexTrate™)
Fan-out-wafer-level-packaging (FOWLP) and fan-out-panel-level-packaging is an attractive cost-effective packaging platform that offers significant cost savings as compared to similar bridge connection technologies or interposers. Due to die-placement error and shift during molding, die assemblies on FOWLP can have significant die-shift. Design rules must ensure the accommodation of die-shift and as a result fine-pitch patterning is limited. TrueAdapt™ aims to solve that by utilizing in-line characterization of the die shift, generation of a new layout using the measured offsets, and patterning with direct-write lithography for high throughput wafer-level and panel-level fabrication at fine-pitches. We have fabricated an assembly of dies interconnected in a daisy chain network with 10 µm pitch wiring on the FlexTrate™, a bio-compatible polydimethylsiloxane (PDMS) based FOWLP architecture. We measure die shift using optical metrology techniques to generate a stitched image of the assembly. The image is then processed using computer vision to measure the die-shift. Furthermore, we generate a layout based on measured die-shift that adaptively routes the wiring in between dies. Via and metal layers are subsequently patterned using direct-write lithography using a 405 nm laser direct-write lithography system. Fan-out packages in addition to die-shift suffer from excessive warpage of the substrates. We have applied focus drilling to direct-write laser lithography, in a process we call Focal Extension, to extend the depth of focus (DOF) of our system to pattern over 100 µm of topography within a single field, making this a truly adaptive patterning process.
PhD student: Golam Sabbir, Henry Sun
Masters student: Mansi Sunil Sheth
Undergraduate student: Travis Ha