Development of Advanced Warpage Measurement Systems: Shadow Moiré with Nonzero Talbot Distance and Far Infrared Twyman-Green Interferometry
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Coefficient of thermal expansion mismatches in microelectronic devices induce deformation when these devices are subjected to thermal loading during manufacturing or everyday operation, creating failures and other reliability concerns. High-sensitivity out-of-plane deformation measurement systems are therefore required to characterize these deformations for design analysis and model verification. Two advanced systems improving on known techniques have been developed to fill needs not met by existing systems. A novel shadow moiré implementation using the nonzero Talbot distance overcomes fundamental limitations to conventional practice, providing an enhanced dynamic range uniquely capable of measuring large deformations and non-coplanar surfaces. In addition, an advanced interferometer using an infrared source enables characterization of rough surfaces which are too diffusive for traditional visible interferometry. This system's Twyman-Green configuration also circumvents inherent limitations to previous Fizeau implementations. Results from experiments conducted on representative flip-chip specimens demonstrate both systems' unique capabilities.