Detection of structural asymmetries in Forksheet FET arrays using Mueller matrix ellipsometry: a theoretical study

Abstract

Background: With the appearance of ever-smaller transistors and new structures, new metrological challenges also arise, including the detection of different structural defects. Mueller matrix (MM) measurement can provide an opportunity to investigate them.Aim: Defects can cause a deterioration in device performance; therefore, their characterization is particularly important. Our goal is to investigate the possibility of detecting asymmetry defects using MM measurement and to study the distinguishability of these structural imperfections in the case of forksheet field-effect transistor (FET).Approach: Simulation of MM measurements with different degrees and directions of forksheet FET's profile asymmetries. To quantify the distinguishability of the optical responses caused by the defects, the correlation between the asymmetry parameters was calculated. Since the precise alignment of a sample is a key factor in the detection of asymmetries, the effect of the alignment uncertainty and a method for filtering it out were also investigated.Results and Conclusions: MM measurement is sensitive to both the magnitude and direction of the profile bending and the shift of the dielectric wall. The correlation coefficients show that the optical responses of the asymmetry defects and the alignment error can be distinguished. The latter can even be eliminated with a method presented in this article.