Reduction of SEM noise and extended application to prediction of CD uniformity and its experimental validation

Hoyeon Kim; Chan Hwang; Seok-hwan Oh; Jeongho Yeo; Young hee Kim

doi:10.1117/12.879590

20 April 2011 Reduction of SEM noise and extended application to prediction of CD uniformity and its experimental validation

Hoyeon Kim, Chan Hwang, Seok-hwan Oh, Jeongho Yeo, Young hee Kim

Author Affiliations +

Proceedings Volume 7971, Metrology, Inspection, and Process Control for Microlithography XXV; 79710K (2011) https://doi.org/10.1117/12.879590
Event: SPIE Advanced Lithography, 2011, San Jose, California, United States

Abstract

As the design rule of Integrated Circuits(IC) becomes smaller, the precise measurement of Critical Dimension (CD) of features and minimization of deviation in CD measured becomes a vital issue. In this paper, a simple frequency analysis method to extract the noise from SEM images was used to evaluate the contribution of SEM noise in CD Uniformity. Multiple SEM images of simple Line and Space (L/S) patterns were analyzed and a model of frequency profile (Power Spectrum Density (PSD) model) was made using an offline analyzing tool based on Matlab®. From this profile, white noise and 1/f profile were separated. Noises are eliminated to generate a noise reduced PSD profile to make CD results. The contribution of white noise on CD measurement can be assessed using Line Width Roughness (LWR) measurement. Furthermore, CD uniformity can be also predicted from the model. This prediction is based on an assumption that CD uniformity is equal to LWR if the inspection area is extended to infinity and appropriate sampling method is applied. The results showed that the contribution of white noise on LWR can be up to around 70% (in power) without any noise reduction measures (sum line averaging) after imaging in photo resist image. For experimental validation, CD uniformity is predicted from the model for different measurement conditions and compared with real measurement. For a result, CD uniformity prediction (3sigma) from the model shows within 20% in accuracy with real CD uniformity value measured from the photo resist image.

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Hoyeon Kim, Chan Hwang, Seok-hwan Oh, Jeongho Yeo, and Young hee Kim "Reduction of SEM noise and extended application to prediction of CD uniformity and its experimental validation", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 79710K (20 April 2011); https://doi.org/10.1117/12.879590

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KEYWORDS

Line width roughness

Critical dimension metrology

Scanning electron microscopy

Inspection

Photoresist materials

Image processing

Denoising

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