A Finite Element Analysis of Process-Induced Stress in Scaled-Down MOSFETs. Finite Element Stress Analysis and Evaluation of its Validity by Using Convergent-Beam Electron Diffraction.

Abstract

The residual stress in thin films composing metal oxide semiconductor field emitter transistors (MOSFETs) was quantified, and a finite element method (FEM) based on the residual stress was proposed to predict stress in a scaled-down MOSFET which consists of a variety of thin films. A numerical analysis of process-induced stress in 130-nm-technology node MOSFETs was also carried out. The strain in the Si area in an actual MOSFET was measured by convergent-beam electron diffraction (CBED) and was compared with the FEM results to verify the validity of the FEM methodology. The FEM analysis results showed that (1) the magnitude of the compressive strain in the channel area increases as the source/drain length is reduced, (2) salicide reduces the magnitude of the compressive strain in the channel area, and (3) depositing tensile-stress SiN film in the sidewall spacer effectively reduces the channel strain. From a comparison of the FEM and CBED results it was found that although differences in the strain values obtained by these two methods are recognized, the results for both methods are in good agreement with regard to the shape of the strain distribution.