Molecular Dynamic Simulation Study of Stress Memorization in Si Dislocations

TM Shen and YT Tung and YY Cheng and DC Chiou and CY Chen and CC Wu and YM Sheu and HT Tsai and CM Huang and G Hsieh and G Tsai and S Fung and J Wu and CH Diaz, 2012 IEEE INTERNATIONAL ELECTRON DEVICES MEETING (IEDM) (2012).

Stress-Memorization-Technique by Si dislocations is effective in enhancing NFET device performance 1,2. For the first time, MD (Molecular Dynamic) simulations are applied to explain the formation mechanism of dislocations during the Solid-Phase-Epitaxy-Regrowth (SPER) process. A semi- empirical TCAD method based on lattice-KMC (L-KMC) is then developed to predict dislocation formation. The simulated dislocation positions agree well with silicon experiments characterized by TEM. TCAD simulations show that the resulting dislocations are along the 111 direction and provide similar to 650MPa average longitudinal stress in channel regions, consistent with Nano-Beam-Diffraction (NBD) strain measurement. The channel stress is predicted by simulation to further increase by 1.5X after the poly-silicon gate removal step in a replacement-gate process. The dislocation SMT enhances NFET electron mobility by 25% and Ion-Ioff performance by 15%.

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