Samson Melamed, a graduate student in Electrical and Computer Engineering, won the best student paper award at the IEEE 3DIC Conference held this fall in San Francisco.

The paper, Junction-level Thermal Extraction and Simulation of 3DICs was authored by Samson Melamed, Thorlindur Thorolfsson, Adi Srinivasan, Edmund Cheng, Paul Franzon and Rhett Davis.  Melamed, Thorolfsson, Franzon, and Davis are all with the ECE Department at NC State University.  Srinivasan and Cheng are with Gradient Design Automation.

In 3DICs heat dissipating devices are stacked directly on top of each other leading to a higher heat density than in a comparable 2D chip. 3D integration also moves the majority of active devices further away from the heatsink. This results in a degraded thermal path which makes it more challenging to remove heat from the active devices.

Gradient FireBolt was used to perform an appropriate 3D thermal analysis on a 1024-point, memory-on-logic 3DIC FFT processor for synthetic aperture radar (SAR). The chip was simulated with a spatial resolution of 80 nm, and was modeled to include the effect of each line of interconnect, as well as each via and fill structure exactly as drawn in the layout. Large isolated temperature spikes were found near groups of clock buffers at the edge of the SRAMs on the middle tier.

It was found that lowering the simulation resolution and using composite thermal conductivities failed to accurately predict the location of these tentpoles.

For more information on IEEE 3DIC 2009 visit http://www.3dic-conf.org/.