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Proceedings Paper

Improving the measurement performance of angle-resolved scattermetry by use of pupil optimization
Author(s): Fan Wang; Qingyun Zhang; Hailiang Lu; Lifeng Duan; Xiaoping Li
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Paper Abstract

As feature sizes decrease, requirements on critical dimension uniformity have become very strict. To monitor variations in lithography process and perform advanced process control it is important to establish a fast and accurate measurement technique for characterizing critical dimension, sidewall angle and height of the resist profile. Various techniques for feature measurement such as CD-SEM, AFM, FE-SEM, and scatterometry have been developed. Among these techniques, scatterometry has both high accuracy and a non-deconstructive measurement modality. It thus provides advantages of low-cost, high throughput, and robustness. Angle-resolved scatterometry has already been shown to provide in-line feedback information necessary for tight process control. In present paper, we introduce a novel angle-resolved scatterometer with pupil optimization. The intensity distribution of the incident light in the pupil plane is optimized considering the feature and the image sensor response properties, which improve the measurement performance of the scatterometer. A first order analysis of measurement sensitivity at different polarization conditions is carried out on resist-coated wafers with 45nm and 22nm features using Rigorous Coupled- Wave analysis (RCWA). Based on the criteria defined as the sum of the absolute difference of the relative intensity values between the nominal and varied conditions in the pupil, the sensitivity of the new technique and traditional scatterometer is compared. Simulation results show that, for 45nm feature, the sensitivity in s and p-polarization is increased by 400% and 300% respectively. While for 22nm feature, the sensitivity is increased by 200% and 130%. Reproducibility of measurement is also analyzed on 45nm and 22nm features using a Monte Carlo method and models for detector noise. Comparison of reproducibility for CD, sidewall angle, and resist height measurement is demonstrated.

Paper Details

Date Published: 5 April 2012
PDF: 7 pages
Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83242M (5 April 2012); doi: 10.1117/12.916115
Show Author Affiliations
Fan Wang, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Qingyun Zhang, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Hailiang Lu, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Lifeng Duan, Shanghai Micro Electronics Equipment Co., Ltd. (China)
Xiaoping Li, Shanghai Micro Electronics Equipment Co., Ltd. (China)

Published in SPIE Proceedings Vol. 8324:
Metrology, Inspection, and Process Control for Microlithography XXVI
Alexander Starikov, Editor(s)

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