Three-dimensional chip stacks are better connected with through-silicon-vias (TSVs) filled with carbon nanotubes instead of copper, according to researchers at Chalmers University of Technology in Gothenburg, Sweden.
TSVs promise to speed up the communications among all the chips that make up an electronic system by stacking them in 3-D instead of laying them out flat on circuit boards. Unfortunately, filling the vias with copper causes problems with thermal expansion, since copper expands more than the surrounding silicon. Carbon nanotubes could solve this problem.
“Carbon nanotubes have much better properties than copper, both in terms of thermal and electrical conductivity”, said Kjell Jeppsson, a member of the Chalmers research team. “They expand about the same amount as the surrounding silicon while copper expands more, which results in mechanical tension that can cause the components to break.” Other team members included Teng Wang and Johan Liu.