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New method removing SEM image noise to characterize CD and LWR
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Paper Abstract

It is important to remove image noise properly to measure critical dimension (CD) and roughness values from scanning electron microscope (SEM) images. In order to reduce image noise, the number of electron beam (EB) scans, or frame number, is increased. However, this excess EB irradiation damages the objects being measured and changes their size. In this paper, a new image analysis method is introduced to remove image noise without a typical noise filter. In this method, each image frame is used in a four dimensional array, and several artificial images are generated and edge coordinates are calculated. As a result of this new method, we can separate the line width roughness (LWR) components into process roughness and image noise, and analyze images with lower number of frames with minimal EB damage.

The impact of image noise on the accuracy of CD extraction is explained in the section on analysis of variance (ANOVA). The variation is separated as wafer to wafer (WTW), field to field (FTF), die to die (DTD), pattern to pattern (PTP), line width roughness (LWR), and stochastic pattern noise (SPN; which is random variation per a pattern) at this ANOVA. Roughness component from image noise is included in SPN. It is possible to remove the image noise component from SPN by applying this new image analysis method, and it is also possible to discuss the SPN from shot noise of exposure tool or variation of resist material component. ANOVA can put an end to discussion of measurement length of line pattern to know the state of low frequency roughness. LWR component of long wavelength is distributed to PTP and SPN when short patterns are measured. It is important to remove image nose properly and to compare the statistical analysis processed SPN value.

Paper Details

Date Published: 26 March 2019
PDF: 10 pages
Proc. SPIE 10959, Metrology, Inspection, and Process Control for Microlithography XXXIII, 109592N (26 March 2019); doi: 10.1117/12.2514661
Show Author Affiliations
Shinji Kobayashi, Tokyo Electron Kyushu Ltd. (Japan)
Satoru Shimura, Tokyo Electron Kyushu Ltd. (Japan)
Masashi Enomoto, Tokyo Electron Kyushu Ltd. (Japan)
Robert Kern, Enthought, Inc. (United States)
Timothy Diller, Enthought, Inc. (United States)
Tony McDaniel, Enthought, Inc. (United States)
Nan Qin, Enthought, Inc. (United States)
Thomas Reay, Enthought, Inc. (United States)
Roger Serwy, Enthought, Inc. (United States)


Published in SPIE Proceedings Vol. 10959:
Metrology, Inspection, and Process Control for Microlithography XXXIII
Vladimir A. Ukraintsev; Ofer Adan, Editor(s)

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