Hot spots suppression by high thermal conductivity film in thin-sub strate CMOS ICs for 3D integration

In this work, three CMOS ring oscillator chips designed for hot spot generation in the LSI device are employed on a Si substrate with the thickness of 525 μm and a thin Si substrate with the thickness of 100 μm. Since a hot spot is observed on the 100 μm thick substrate, a high thermal conductivity film of 10 μm-thick is integrated on the reverse side of the thin substrate as a heat spreader. The ring oscillator generates heat by a short pulse with the shorter width than the acquisition time of the thermography image. A transitional thermal diffusivity characteristic is evaluated in the device. As a result, for the substrate with the heat spreader, the effective thermal diffusivity is 39% higher than the substrate without the heat spreader. The temperature of ring oscillator area is reduced 15% after applying 7 V power for 0.05 seconds. Moreover the peak temperature at the hot spot is confirmed with 24% reduction.