Paragkumar Thadesar, a Ph.D. student in the School of Electrical and Computer Engineering (ECE) at Georgia Tech, has received an IBM Ph.D. Fellowship for the 2014-2015 academic year. Thadesar is a member of the Integrated 3D Systems Research Group, led by ECE Associate Professor Muhannad Bakir.

The bandwidth and energy demands from multicore microprocessors, along with the increasing need for heterogeneous nanoelectronic systems featuring RF, logic, and memory, have caused the semiconductor industry to explore 3D and 2.5D integration methodologies. The key technology driving this integration innovation is through-silicon-vias (TSVs). Parag and Bakir have designed, fabricated, and characterized a new generation of electrical TSVs that exhibit low electrical loss and thermomechanical stress. Two examples of the novel TSVs are: 1) photodefined polymer-clad TSVs and 2) photodefined polymer-embedded vias. With respect to the first approach, TSVs consist of "thick" polymer dielectric liner, which is in contrast to current state-of-the-art TSVs that feature thin silicon dioxide liner. The thick polymer liner helps reduce TSV stress and electrical loss. With respect to the second approach, TSVs consist of copper vias embedded in photodefined polymer wells that help attain even greater reduction in electrical loss.

To characterize the fabricated TSV technologies, both thermomechanical and electrical characterizations were performed in this research. First, in collaboration with Dr. Suresh Sitaraman (George W. Woodruff School of Mechanical Engineering), thermomechanical strain characterization was performed for the fabricated polymer-clad TSVs using synchrotron x-ray diffraction (XRD) at the Lawrence Berkeley National Laboratory, demonstrating 30 percent reduction in the maximum first principal strain in the silicon compared to state-of-the-art TSVs. Then, high-frequency characterization was performed for the fabricated polymer-embedded vias, demonstrating up to 80 percent reduction in the TSV insertion loss at 50 GHz compared to state-of-the-art TSVs.

The IBM Ph.D. Fellowship Awards Program is an intensely competitive worldwide program, which honors exceptional Ph.D. students who have an interest in solving problems of interest to IBM and which are fundamental to innovation including innovative software, new types of computers, technology, and interdisciplinary projects that create social and business value. IBM Ph.D. Fellows are awarded a stipend for one academic year and are matched with an IBM mentor according to their technical interests.