At its Fab 8 campus in Saratoga County, N.Y., GLOBALFOUNDRIES today demonstrated its first functional 20nm silicon wafers with integrated Through-Silicon Vias (TSVs).
Manufactured using GLOBALFOUNDRIES' 20nm-LPM process technology, the TSV capabilities will allow the foundry's customers to stack multiple chips on top of each other, providing another avenue for delivering the performance, power, and bandwidth requirements of today's electronic devices.
TSVs are vertical vias etched in a silicon wafer that are filled with a conducting material, enabling communication between vertically stacked integrated circuits. The adoption of three-dimensional (3D) chip stacking is increasingly being viewed as an alternative to traditional technology node scaling at the transistor level. However, TSVs present a number of new challenges to semiconductor manufacturers.
GLOBALFOUNDRIES utilizes a "via-middle" approach to TSV integration, inserting the TSVs into the silicon after the wafers have completed the Front End of the Line (FEOL) flow and prior to starting the Back End of the Line (BEOL) process. This approach avoids the high temperatures of the FEOL manufacturing process, allowing the use of copper as the TSV fill material. To overcome the challenges associated with the migration of TSV technology from 28nm to 20nm, GLOBALFOUNDRIES engineers have developed a proprietary contact protection scheme. This scheme enabled the company to integrate the TSVs with minimal disruption to the 20nm-LPM platform technology, demonstrating SRAM functionality with critical device characteristics in line with those of standard 20nm-LPM silicon.