Nobuhiro Komine

Method of robust pattern design for lens aberration

Recently, the critical dimension (CD) abnormality due to lens aberrations of exposure tool has become one of the critical issues in production of semiconductor devices. The most remarkable feature of CD abnormality due to lens aberration is asymmetry of symmetric twin pattern. And the asymmetry is only caused by a particular aberration because the influence on CD abnormality of lens aberration depends on the device pattern shape. Therefore, it is important to know the interaction of the device pattern shape with lens aberrations, and to ensure that consideration of the interaction is reflected in the design of device. This paper introduces a pattern design methods robust to lens aberration is based on Zernike Sensitivity (ZS) method. We conclude that our method modifies a pattern sensitive to lens aberration so that it becomes a pattern robust to lens aberration without reduction of the depth of focus (DOF).

Mix-and-match overlay method by compensating dynamic scan distortion error

This paper discusses the compensation method and APC system to reduce errors in mix and matching overlay between scanners. We proposed the compensation model for intra-field errors in mix and matching. And we developed the advanced APC system also to improve dynamic scan distortion using the compensation model.

Overlay sampling optimization by operating characteristic curves empirically estimated

Operating Characteristic (OC) curves, which are probabilities of lot acceptance as a function of fraction defective p, are powerful tools for visualizing risks of lot acceptance errors. The authors have used OC curves for the overlay sampling optimization, and found that there are some differences in probability of acceptance between theoretical calculation and empirical estimation. In this paper, we derive a theoretical formulation of the probability of acceptance for several simple cases by decomposing overlay errors, and show that the origin of the differences is the use of stratified sampling in overlay inspection.