Tensor Evaluation of Stress Relaxation Profile in Strained SiGe Nanostructures on Si Substrate

Abstract

A strained SiGe layer will be used in next-generation transistors to improve device performance along with device scaling. However, the stress relaxation of SiGe layer may be inevitable in nanodevices, because the SiGe layer is processed into nanostructure. In this study, we evaluated the stress relaxation profiles in mesa-shaped strained SiGe layers on Si substrate by electron back scattering pattern (EBSP), super-resolution Raman spectroscopy (SRRS) measurements, and finite element method (FEM) simulation. As a result, the stress relaxation profiles with high spatial resolution were obtained by each measurement. The range of σxx stress relaxation is mostly 100 nm from edge. The drastically σxx stress relaxation was over than approximately 25 percent in that range. Thus, the stress relaxation is inevitable in nanostructure with less than 200 nm scale. Moreover, there is a good correlation between the results of EBSP, SRRS measurements, and FEM simulation. The spatial resolution of EBSP and SRRS measurements were estimated less than 100 nm. Thus, super-resolution algorithm improved the spatial resolution of Raman spectroscopy from approximately 400 nm to sub-100 nm. It is prospective to evaluate the precise stress relaxation profile the sub-100 nm order structures by EBSP and SRRS measurements, respectively. Moreover, the complement of FEM simulation is important to verify the results of EBSP and SRRS. We believe that EBSP, SRRS measurements, and FEM simulation will be indispensable to for evaluating stress in future MOSFETs with high spatial resolution, which will surely surpass the present ones in complexity.