AVS 51st International Symposium
    Thin Films Monday Sessions
       Session TF-MoM

Paper TF-MoM4
Evaluation of Plasma Enhanced Atomic Layer Deposition TaN for Metal Gate Electrode Application

Monday, November 15, 2004, 9:20 am, Room 303C

Session: ALD and Applications
Presenter: H. Kim, IBM Thomas J. Watson Research Center
Authors: H. Kim, IBM Thomas J. Watson Research Center
D.-G. Park, IBM Semiconductor Research and Development Center
P. Ronsheim, IBM Semiconductor Research and Development Center
S.M. Rossnagel, IBM Thomas J. Watson Research Center
Correspondent: Click to Email
TaN has been one of the most attractive materials as a diffusion barrier for Cu interconnect technology due to its good diffusion barrier properties, good adhesion to dielectrics, and high thermal stability. More recently, TaN has been considered as a strong candidate for a direct metal gate material due to its proper work function (~4.3eV) as n-type conductivity. As for the deposition technique of metal gate electrode, previous study on TiN metal gate demonstrated that atomic layer deposition (ALD) has benefits including negligible defect generation and improved device reliability compared to other deposition method. Previously, we have reported that PE-ALD from TaCl@sub 5@ and N@sub 2@/H@sub 2@ plasma produced low resistivity cubic TaN films with various N/Ta ratios with excellent barrier properties for Cu metallization. In this study, PE-ALD TaN was evaluated as a gate electrode for metal-oxide-semiconductor (MOS) capacitors composed of TaN/SiO@sub 2@/p-Si with nanoscale thick (1.8-5.5 nm) SiO@sub 2@ dielectric. For as-patterned MOS structure, the leakage current characteristics were strong functions of N/Ta ratio and plasma power. A dramatic decrease of leakage current with two orders of magnitude was observed with decrease of the plasma power from 500W to 200W. For PE-ALD TaN electrode with stoichiometric N/Ta ratio, we observed a severe damage at SiO@sub 2@/Si interface as observed by a distorted capacitance-voltage (C-V) curve shape near the valence band edge of Si band gap. While the interface damages were partially disappeared after forming gas anneal, the gate leakage current level was remained high. However, the reduction of leakage current was more prominent for TaN@sub x@ films deposited with N@sub 2@ only plasma at both high and low plasma power condition with improved C-V characteristics. Additionally, a comparative study with PVD TaN electrode will be presented focusing on the impurity effect of TaN metal gate.