Measurement technique of telecentricity for the illumination system in the 193 nm photolithography

摘要

The location of mask and wafer for the photolithography is one of the important and precise parts in a lithographic test pattern. If mask and wafer are illuminated obliquely (that is to say telecentricity) by incident light, the diffracted waves will occur asymmetrically. If such an asymmetry is relatively large in the illuminate system, which makes the illuminate system no longer a telecentric system, the non-imaging optical system becomes imaging optical system, and the projection lithography will be meaningless. Therefore, in this paper we propose a measurement method of telecentricity for lithographic test pattern and investigate the influences of various factors on the imaging properties by numerical simulation. Telecentricity measurement can be performed using a pinhole that comprises 40 × 40 point under the different illumination system (conventional and dipole) in the wafer plane. We show measurement values and measurement errors of telecentricity for illumination system (conventional and dipole). The results indicate that measurement values and measurement errors of telecentricity satisfy the measurement requirement from our method in the wafer plane.