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Strained Si-based technology has imposed a new challenge for understanding dopant implantation and diffusion in SiGe that is often used as the buffer layer for a strained Si cap layer. In this work, we describe our latest modeling effort investigating the difference in dopant implantation and diffusion between Si and SiGe. A lattice expansion theory was developed to account for the volume change due to Ge in Si and its effect on defect formation enthalpy. The theory predicts that As diffusion in SiGe is enhanced by a factor of ~10, P diffusion by a factor of ~2, and B diffusion is retarded by a factor of ~6, when compared to bulk Si. These predictions are consistent with experiment. Dopant profiles for As, P, and B were simulated using process simulators FLOOPS and DIOS. The simulated profiles are in good agreement with experiment. Dopant implantation was simulated using REED-MD. The results showed a noticeable difference in peak and tail positions SiGe compared to Si.

Two finite element methods are implemented to investigate localized mechanical stress fields generated during multiple stages of silicon IC fabrication. The boundary loading method (BL) uses the oxide interface stresses as a boundary condition for the substrate solution. In the fully integrated method (n), the strains in substrate are calculated along with the oxide stress computation. Both of the methods can be used to couple stresses generated by oxidation volume expansion to strains present from other sources such as thermal expansion, dopants, and intrinsic film stresses. They are then evaluated on computational intensiveness and in stress solution variation. It is found that the BL method computes nearly the same oxide solution as the FI method and the oxide solution corresponds very well in the oxide and surface films for a LOCOS process.

ABSTRACTmethod for characterizing the mechanical stress induced in silicon technology is described. Analysis by scanning Kelvin probe force microscopy (SKPM) coupled with finite-element (FE) mechanical strain simulations is performed. The SKPM technique detects variations in the semiconductor work function due to strain influences on the band gap. This technique is then used to analyze the strain induced by shallow trench isolation processes for electrical isolation. The SKPM measurements agree with the FE simulations qualitatively.