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Proceedings Paper

New analytical algorithm for overlay accuracy
Author(s): Boo-Hyun Ham; Sangho Yun; Min-Cheol Kwak; Soon Mok Ha; Cheol-Hong Kim; Suk-Woo Nam
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Paper Abstract

The extension of optical lithography to 2Xnm and beyond is often challenged by overlay control. With reduced overlay measurement error budget in the sub-nm range, conventional Total Measurement Uncertainty (TMU) data is no longer sufficient. Also there is no sufficient criterion in overlay accuracy. In recent years, numerous authors have reported new method of the accuracy of the overlay metrology: Through focus and through color. Still quantifying uncertainty in overlay measurement is most difficult work in overlay metrology. According to the ITRS roadmap, total overlay budget is getting tighter than former device node as a design rule shrink on each device node. Conventionally, the total overlay budget is defined as the square root of square sum of the following contributions: the scanner overlay performance, wafer process, metrology and mask registration. All components have been supplying sufficiently performance tool to each device nodes, delivering new scanner, new metrology tools, and new mask e-beam writers. Especially the scanner overlay performance was drastically decreased from 9nm in 8x node to 2.5nm in 3x node. The scanner overlay seems to reach the limitation the overlay performance after 3x nod. The importance of the wafer process overlay as a contribution of total wafer overlay became more important. In fact, the wafer process overlay was decreased by 3nm between DRAM 8x node and DRAM 3x node. We develop an analytical algorithm for overlay accuracy. And a concept of nondestructive method is proposed in this paper. For on product layer we discovered the layer has overlay inaccuracy. Also we use find out source of the overlay error though the new technique. In this paper, authors suggest an analytical algorithm for overlay accuracy. And a concept of non-destructive method is proposed in this paper. For on product layers, we discovered it has overlay inaccuracy. Also we use find out source of the overlay error though the new technique. Furthermore total overlay error data is decomposed into two parts: the systematic error and the random error. And we tried to show both error components characteristic, systematic error has a good correlation with residual error by scanner condition, whereas, random error has a good correlation with residual error as going process steps. Furthermore, we demonstrate the practical using case with proposed method that shows the working of the high order method through systematic error. Our results show that to characterize an overlay data that is suitable for use in advanced technology nodes requires much more than just evaluating the conventional metrology metrics of TIS and TMU.

Paper Details

Date Published: 4 April 2012
PDF: 9 pages
Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83240A (4 April 2012); doi: 10.1117/12.918002
Show Author Affiliations
Boo-Hyun Ham, Samsung Electronics Co., Ltd. (Korea, Republic of)
Sangho Yun, Samsung Electronics Co., Ltd. (Korea, Republic of)
Min-Cheol Kwak, Samsung Electronics Co., Ltd. (Korea, Republic of)
Soon Mok Ha, Samsung Electronics Co., Ltd. (Korea, Republic of)
Cheol-Hong Kim, Samsung Electronics Co., Ltd. (Korea, Republic of)
Suk-Woo Nam, Samsung Electronics Co., Ltd. (Korea, Republic of)


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

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