Characterization of Atom Diffusion in Polycrystalline Si/SiGe/Si Stacked Gate

In the aggressive scaling of the gate dielectric thickness for continuous shrinkage of MOSFETs, a increase in the gate resistance emerges as one of major concerns from the viewpoint of eliminations in both the voltage drop through the gate under higher gate leakage current [1] and the gate depletion effect [2]. Especially, in case of poly-Si gate, with decreasing gate size, the gate depletion effect becomes serious due to dopant loss reflecting impurity pile-up [3]. Poly-SiGe gate is one of the promising candidate for a gate material of next-generation MOSFETs because of lower resistivity and less depletion effect [3–5] in comparison with poly-Si gate in addition to the consideration about controllability of work function and matching with conventional silicon process [6,7]. In the implementation of poly-SiGe gate, the control of the redistribution of Ge atoms in a gate stack structure during dopant activation anneal is of great importance. In this work, we have studied the thermal diffusion and redistribution of Ge atoms in the poly-Si/poly-SiGe/poly-Si stacked structures.