AVS 51st International Symposium
    Electronic Materials and Processing Tuesday Sessions
       Session EM-TuA

Paper EM-TuA6
Variation of WNx Gate Work Function after High Temperature Annealing

Tuesday, November 16, 2004, 3:00 pm, Room 304B

Session: Defects and Interfaces in Electronic Materials and Devices
Presenter: P.-C. Jiang, National Cheng Kung University, Taiwan
Authors: P.-C. Jiang, National Cheng Kung University, Taiwan
J.S. Chen, National Cheng Kung University, Taiwan
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The selection of the gate electrode material has become a critical issue as the dimension of CMOS devices continues to scale down. According to the 2001 ITRS roadmap, WNx is a promising material as the gate electrode for the PMOS transistor, because the WNx has a Fermi level near the silicon valence band. In this work, we investigate the variation of metal work function (Φm) of reactive sputtered WNx films after annealing at different temperatures (400-600â"f). The annealing atmosphere is forming gas (N2:H2=135:15) and the annealing time is 30min. By measuring the C-V curves of the MOS structure with oxides of different thickness, we can derive the Φm of the WNx gate. After annealing, the phases of the WNx films had changed and their nitrogen contents also varied due to the out-diffusion of nitrogen to the ambient. The variation of nitrogen content in WNx upon annealing will lead to the change of Φm. By measuring the I-V curves of the MOS structure with reverse bias, the leakage current increases with decreasing the Φm. As a result, the Φm not only affects the threshold voltage of the device but also changes the leakage current of the oxide layer, and the nitrogen content in WNx is the key point to determine the Φm.