Process characterization vehicles for 3D Integration

Abstract

Assemblies produced by 3D Integration, whether fabricated at die or wafer level, involve a large number of post fab processing steps. Performing the prove-in of these operations on high value product has many limitations. This work uses simple surrogate process characterization vehicles, which workaround limitations of cost, timeliness of piecparts, ability to consider multiple processing options, and insufficient volumes for adequately exercising flows to collect specific process data for characterization. The test structures easily adapt to specific product in terms of die dimensions, aspect ratios, pitch and number of interconnects, and etc. This results in good fidelity in exercising product-specific processing. The discussed Cyclops vehicle implements a mirrored layout suitable for stacking to itself by wafer-to-wafer, die-to-wafer, or die-to-die. A standardized 2×10 pad test interface allows characterization of any of the integration methods with a single simple setup. This design offers the utility of comparison study of the various methods all using the same basis.