Abstract
A two-chip stacking 3D IC with 0.18 μm technology has been mounted in a QFP package for conducting measurement of thermal resistance from junction to the package case surface (bottom). The thermal resistances for the layers of chips, micro bumps, underfill resin between chips, and ceramic substrate are also being analyzed with the thermal RC model theory and the cumulative structure function. The top chip is embedded with through-silicon vias (TSVs) and is thinned down to 60 μm thick. The bottom chip has no TSV and the thickness is the same as a normal IC chip. Both chips have the same layout and include two types of heaters. The first heater is designed to emulate a hot spot and is located at the chip center. The second heater, with heat flux level (uniform heating) close to 1/20 of the first heater, is designed to heat up the surrounding area of the first heater. A simulation model of the QFP package is developed and a set of equivalent thermal conductivity correlations in planar (xy) and vertical (z) directions of TSVs are used in order to simplify the simulation model and shorten the computational time. Comparisons between simulation models show that the result is accurate for uniform heating condition and satisfactory for hot spot heating condition.
