by Ed Korczynski, Senior Technical Editor, Solid State Technology
Through-silicon vias (TSV) can be used to connect 3D multi-chip module stacks with improved performance and reduced timing delays. A new report by analysts at TechSearch International, [PDF file] Through Silicon Via Technology: The Ultimate Market for 3D Interconnect provides a forecast for millions of silicon wafers to be made with TSV in the year 2014. For the next few years, however, it is likely that image-sensors and memory chip stacks will be the major high-volume applications, building on the estimated less than 50,000 wafers to be fabbed with TSV this year according to TechSearch President Jan Vardaman.
The industry is now moving past the feasibility (R&D) phase for TSV technology and into the commercialization phase, where economic realities will determine which technologies are adopted. Low-cost fine via hole formation and highly reliable via filling technologies have been demonstrated; process equipment and materials are available. Global research organizations are looking at applications for TSVs including image sensors, flash, DRAM, microprocessors, FPGAs, and power amplifiers.
There is no question that 3D TSV will be adopted, but the timing for mass production depends on how the cost of the new technology compares with that of existing technologies. In particular, as confirmed by Vardaman, if there are only 2 silicon layers to be assembled it is generally more cost-effective today to use flip-chip with wire-bonders. Another 1 or 2 chip layers can be easily added to the bottom side of an interposer, still without the need for TSV.