CHARACTERIZATION AND OPTIMIZATION OF PLASMA NITRIDED GATE OXIDES FOR ADVANCED CMOS GATE DIELECTRIC

摘要

Due to continuous scaling of gate dielectric thickness, gate leakage current has increased significantly. As a result, high power consumption in integrated circuit has become a limiting factor in device operation. Besides gate leakage current increase, thickness scaling challenge, mobility and reliability degradation pose road blocks for new technology implementation into production. To reduce gate leakage current, nitrogen incorporation in silicon dioxide has been developed as a solution. Two primary approaches used for adding nitrogen are conventional thermal nitridation and advanced plasma nitridation. The conventional thermal nitridation degrades carrier mobility since nitrogen is incorporated at gate dielectric and channel interface. The high thermal budget with thermal nitridation also limits the amount of nitrogen to be incorporated and capability of thickness scaling. Decoupled Plasma Nitridation (DPN) allows us to add nitrogen at top portion of a base oxide with low ion energy. Significant amount of nitrogen can be added through plasma source modification with further reduced ion energy. In this paper, we demonstrate that device mobility improvement, leakage current reduction and thickness scaling can be achieved through plasma generation apparatus improvement, approaches of nitrogen incorporation and post nitridation processing optimization. The decoupled plasma nitridation not only can meet current device performance requirement, it is also viable for future technology gate dielectric application.