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Proceedings Paper

Improvement of the common DoF across field for hole-structure process layers
Author(s): Shu Huei Hou; Edgar Huang; Aroma Tseng; Met Yeh; Bill Lin; Chun Chi Yu; Eason Lin
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Paper Abstract

It is well-known that the available depth of focus (DoF) tend to decrease for each advancing technology node. Moreover the leveling control on wafer topography has become a challenge to affect the focus control on exposure tool capability, especially for the critical hole-structure layer of the back end of line (BEoL). In this study, we used the via layer from the real products as an example of optimizing the exposure tool's leveling system to reduce process-related influences to improve the intra-field focus control range. First, the focus-exposure matrices (FEMs) were applied to a wafer in different leveling modes. Then, patterns' critical dimension (CD) in different locations within the same field were measured to produce the Bossung curves required to determine the best focus. The same steps were repeated on a bare wafer to illustrate how the process reduced the common depth of focus range. We also introduced the non-optical leveling sensor, which measured the wafer by the use of physical methods. Since it does not interact with the film stack or the pattern density, the measurement accuracy will be insensitive to process variation. Therefore, it can be used to compensate the optically induced errors from the optical leveling system and to expand the useful depth of focus for improving CD uniformity. Finally, we briefly summarize the improvement ratio achieved of the common DoF using these optical and non-optical leveling systems with different leveling modes.

Paper Details

Date Published: 7 March 2008
PDF: 8 pages
Proc. SPIE 6924, Optical Microlithography XXI, 692434 (7 March 2008); doi: 10.1117/12.772171
Show Author Affiliations
Shu Huei Hou, United Microelectronics Corp. (Taiwan)
Edgar Huang, United Microelectronics Corp. (Taiwan)
Aroma Tseng, United Microelectronics Corp. (Taiwan)
Met Yeh, United Microelectronics Corp. (Taiwan)
Bill Lin, United Microelectronics Corp. (Taiwan)
Chun Chi Yu, United Microelectronics Corp. (Taiwan)
Eason Lin, ASML Taiwan, Ltd. (Taiwan)

Published in SPIE Proceedings Vol. 6924:
Optical Microlithography XXI
Harry J. Levinson; Mircea V. Dusa, Editor(s)

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