A comprehensive study of SiGe Source/ Drain local stress by Nano Beam Diffraction

摘要

Compressive stress introduced by source/drain (S/D) SiGe is widely used in 45nm node and beyond advanced technology which boost the P-channel hole mobility. Quantitive measurement of localized stress in channel is limited by the scaling shrinking. Transmitted electron microscopy- Nano Beam Diffraction (TEM-NBD) is an effective method for the local stress distribution measurement in channel and well area derived from S/D Si_(1-x)Ge_x. In this paper, we study the channel strain from the following aspect, including ⅰ) active area (AA) width, ⅱ) S/D recess shape, ⅲ) S/D recess trench depth, and iv) Germanium (Ge), Boron (B) concentration of S/D Si_(1-x)Ge_x and Ge, B distribution profile. It is revealed that strain has strong relation with these factors. Pitch with narrow AA width shows lower strain than that of wider AA width. S/D recess shape affects the proximity which is critical for the stress derived from S/D SiGe transmit to channel location. Moreover, S/D recess trench depth determines the volume of filled SiGe then affect the strain to channel. Both of the Ge, B concentration of S/D SiGe and the distribution profile directly affects the lattice mismatch which results in the strain. In general, all these factors affect the volume of the filled SiGe and Ge concentration which eventually determine the strain of S/D to channel area.