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Proceedings Paper

Multi-level overlay techniques for improving DPL overlay control
Author(s): Charlie Chen; Y. C. Pai; Dennis Yu; Peter Pang; Chun Chi Yu; Robert (Hsing-Chien) Wu; Eros (Chien Jen) Huang; Marson (Chiun-Chieh) Chen; David Tien; Dongsub Choi
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Paper Abstract

Overlay continues to be one of the key challenges for lithography in semiconductor manufacturing, especially in light of the accelerated pace of device node shrinks. This reality will be especially evident at 20nm node where DPL and multi-layer overlay will require 4nm or less in overlay control across many critical layers in order to meet device yield entitlements. The motivation for this paper is based on improving DPL overlay control in face of the high complexity involved with multi-layer overlay requirements. For example, the DPL-2nd-litho layer will need to achieve tight registration with the DPL-1st-litho layer, and at the same time, it will need to achieve tight overlay to the reference-litho layer, which in some cases can also be a DPL layer. Of course, multi-level overlay measurements are not new, but the combination of increased complexity of multi-DPL layers and extremely challenging overlay specifications for 20nm node together will necessitate a better understanding of multi-level overlay control, specifically in terms of root cause analysis of multi-layer related overlay errors and appropriate techniques for improvement In this paper, we start with the identification of specific overlay errors caused by multi-layer DPL processing on full film stack product wafers. After validation of these findings with inter-lot and intra-lot controlled experiments, we investigate different advanced control techniques to determine how to optimize overlay control and minimize both intra-lot and inter-lot sources of error. A new approach to overlay data analysis will also be introduced that combines empirical data with target image quality data to more accurately determine and better explain the root cause error mechanism as well as provide effective strategies for improved overlay control.

Paper Details

Date Published: 5 April 2012
PDF: 10 pages
Proc. SPIE 8324, Metrology, Inspection, and Process Control for Microlithography XXVI, 83242A (5 April 2012); doi: 10.1117/12.915711
Show Author Affiliations
Charlie Chen, United Microelectronics Corp. (Taiwan)
Y. C. Pai, United Microelectronics Corp. (Taiwan)
Dennis Yu, United Microelectronics Corp. (Taiwan)
Peter Pang, United Microelectronics Corp. (Taiwan)
Chun Chi Yu, United Microelectronics Corp. (Taiwan)
Robert (Hsing-Chien) Wu, KLA-Tencor Corp. (Taiwan)
Eros (Chien Jen) Huang, KLA-Tencor Corp. (Taiwan)
Marson (Chiun-Chieh) Chen, KLA-Tencor Corp. (Taiwan)
David Tien, KLA-Tencor Corp. (United States)
Dongsub Choi, KLA-Tencor Corp. (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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