E-beam-Deposited Tungsten Contacts for Carbon Nanofiber Interconnect Test Devices
Cambridge University Press / Microscopy Society of America
As the downward scaling of integrated circuits continues, the problem of electromigration in copper interconnects becomes increasingly severe. Carbon nanofiber (CNF) can potentially be a replacement for Cu in on-chip interconnects because of its excellent thermal and electrical properties and vertically aligned growth at low temperature. To consider CNF as an on-chip interconnect, the contact resistance between the CNF and the metal electrode must be optimized. Using lithography technique to form contact between CNF and metal requires a complicated and costly device fabrication process . Thus we proposed an alternative method using focused ion beam (FIB) . The resulting total resistance decreased by a factor of about 1000 from that for the pre-W-deposited device . However, FIB has the risk of damaging the on-chip devices because of its high beam energy, and gallium from the ion beam could result in device contamination. To address this problem, we have developed a technique for W deposition using a well-controlled electron beam in a variablepressure scanning electron microscope (VP-SEM). In this technique, the source gas is delivered via a specially designed gas injection system (GIS)  and guided by the focused electron beam to yield deposition on a selected target at a lower energy than FIB.
N. Kanzaki, S. Maeda, P. Wilhite, T. Yamada, T. Saito, and C.Y. Yang, “E-beam-Deposited Tungsten Contacts for Carbon Nanofiber Interconnect Test Devices,” Microscopy and Microanalysis 17 (Suppl 2), 1518-1519 (2011).