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Proceedings Paper

Improved overlay measurement of CMP processed layers
Author(s): Jeong-Ho Yeo; Jeong-Lim Nam; Seok-Hwan Oh; Joo-Tae Moon; Young-Bum Koh; Nigel P. Smith; Andrew M.C. Smout
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Paper Abstract

We report the results of an investigation into the quality of overlay data obtained from a chemical-mechanical polish (CMP) process. The limiting step height for standard bright field optical imaging is examined and found to be less than 200 angstrom. Tool repeatability improvements are demonstrated using a mixture of imaging system modifications and image processing techniques. Using these it is possible to achieve very repeatable data. Good tool precision is insufficient evidence of good data quality as the process can distort the target so that it does not accurately measure the stepper overlay error. We report an examination of data quality obtained using different target designs and both with and without an additional etch- back step to enhance the contrast of the image being measured. Several different techniques have been applied to determine whether the data is accurate. We conclude that bar and frame type targets give much more accurate results than traditional box styles. In addition the tool performance is also improved by using the same target designs. With this choice of target design accurate data is obtained and meaningful correction of stepper errors becomes possible.

Paper Details

Date Published: 21 May 1996
PDF: 10 pages
Proc. SPIE 2725, Metrology, Inspection, and Process Control for Microlithography X, (21 May 1996); doi: 10.1117/12.240095
Show Author Affiliations
Jeong-Ho Yeo, Samsung Electronics Co., Ltd. (South Korea)
Jeong-Lim Nam, Samsung Electronics Co., Ltd. (South Korea)
Seok-Hwan Oh, Samsung Electronics Co., Ltd. (South Korea)
Joo-Tae Moon, Samsung Electronics Co., Ltd. (South Korea)
Young-Bum Koh, Samsung Electronics Co., Ltd. (South Korea)
Nigel P. Smith, Bio-Rad Labs. (United Kingdom)
Andrew M.C. Smout, Bio-Rad Labs. (United Kingdom)

Published in SPIE Proceedings Vol. 2725:
Metrology, Inspection, and Process Control for Microlithography X
Susan K. Jones, Editor(s)

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