Octadecaborane implant technology for 72nm node stack DRAM p+ poly gate doping process

• Main Authors: Chang, B., Chang, J., Harris, M., Ameen, M., Tran, S., Hsiao, M., Ji, S., Yiliang Lin, Jay Huang, Tsai, P.Y., Chiu, M.
• Format: Conference Proceeding
• Language: English
• Subjects: Atomic beams; Boron; Crystallization; Doping; Implants; MOSFET circuits; Productivity; Random access memory; Silicon; Throughput
• DOI: 10.1109/IWJT.2008.4540051

Octadecaborane (B 18 H 22 ) implant technology was evaluated for p+ poly gate doping process in a 72 nm node stack DRAM device. The evaluation criteria were to improve the productivity of the process, which was initially built with conventional atomic boron implantation ( 11 B), while maintaining process equivalency. Before implanting into device wafers, process matching to conventional boron implant was done using both crystalline silicon and poly-silicon on Si wafers. For the crystalline silicon wafers, the Rs of blanket B 18 H x + implants were compared to that of atomic boron. For the poly-Si silicon wafers, SIMS dopant profiles were compared. For the device wafers, boron penetration, gate depletion, and final yield were compared. In addition, B 18 H 22 implant splits of various energies and doses have been studied for their sensitivities to the electrical performance of the p-MOSFET in the 72 nm node stack DRAM devices. In this study, we have demonstrated that B 18 H 22 can provide up to 5X wafer throughput advantage over conventional atomic boron process due to much higher effective beam currents. Besides the significant productivity improvement, B 18 H 22 implant device characteristics were well matched to the baseline atomic boron process. Additionally, negative impact on post implant ashing and cleaning processes was not observed for the B 18 H 22 process.