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Proceedings Paper

Spectral tunability for accuracy, robustness, and resilience
Author(s): Einat Peled; Eran Amit; Yuval Lamhot; Alexander Svizher; Dana Klein; Anat Marchelli; Roie Volkovich; Tal Yaziv; Aaron Cheng; Honggoo Lee; Sangjun Han; Minhyung Hong; Seungyoung Kim; Jieun Lee; Dongyoung Lee; Eungryong Oh; Ahlin Choi; DongSub Choi; DoHwa Lee; Sanghuck Jeon; Jungtae Lee; Seongjae Lee; Zephyr Liu; Jeongpyo Lee; John C. Robinson
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Paper Abstract

In overlay (OVL) metrology the quality of measurements and the resulting reported values depend heavily on the measurement setup used. For example, in scatterometry OVL (SCOL) metrology a specific target may be measured with multiple illumination setups, including several apodization options, two possible laser polarizations, and multiple possible laser wavelengths. Not all possible setups are suitable for the metrology method as different setups can yield significantly different performance in terms of the accuracy and robustness of the reported OVL values. Finding an optimal measurement setup requires great flexibility in measurement, to allow for high-resolution landscape mapping (mapping the dependence of OVL, other metrics, and details of pupil images on measurement setup). This can then be followed by a method for analyzing the landscape and selecting an accurate and robust measurement setup. The selection of an optimal measurement setup is complicated by the sensitivity of metrology to variations in the fabrication process (process variations) such as variations in layer thickness or in the properties of target symmetry. The metrology landscape changes with process variations and maintaining optimal performance might require continuous adjustments of the measurement setup. Here we present a method for the selection and adjustment of an optimal measurement setup. First, the landscape is measured and analyzed to calculate theory-based accurate OVL values as well as quality metrics which depend on details of the pupil image. These OVL values and metrics are then used as an internal ruler (“self-reference”), effectively eliminating the need for an external reference such as CD-SEM. Finally, an optimal measurement setup is selected by choosing a setup which yields the same OVL values as the self-reference and is also robust to small changes in the landscape. We present measurements which show how a SCOL landscape changes within wafer, wafer to wafer, and lot to lot with intentionally designed process variations between. In this case the process variations cause large shifts in the SCOL landscape and it is not possible to find a common optimal measurement setup for all wafers. To deal with such process variations we adjust the measurement setup as needed. Initially an optimal setup is chosen based on the first wafer. For subsequent wafers the process stability is continuously monitored. Once large process variations are detected the landscape information is used for selecting a new measurement setup, thereby maintaining optimal accuracy and robustness. Methods described in this work are enabled by the ATL (Accurate Tunable Laser) scatterometry-based overlay metrology system.

Paper Details

Date Published: 27 April 2018
PDF: 7 pages
Proc. SPIE 10585, Metrology, Inspection, and Process Control for Microlithography XXXII, 105850S (27 April 2018); doi: 10.1117/12.2300507
Show Author Affiliations
Einat Peled, KLA-Tencor Israel (Israel)
Eran Amit, KLA-Tencor Israel (Israel)
Yuval Lamhot, KLA-Tencor Israel (Israel)
Alexander Svizher, KLA-Tencor Israel (Israel)
Dana Klein, KLA-Tencor Israel (Israel)
Anat Marchelli, KLA-Tencor Israel (Israel)
Roie Volkovich, KLA-Tencor Israel (Israel)
Tal Yaziv, KLA-Tencor Israel (Israel)
Aaron Cheng, KLA-Tencor Taiwan (Taiwan)
Honggoo Lee, SK Hynix, Inc. (Korea, Republic of)
Sangjun Han, SK Hynix, Inc. (Korea, Republic of)
Minhyung Hong, SK Hynix, Inc. (Korea, Republic of)
Seungyoung Kim, SK Hynix, Inc. (Korea, Democratic Peoples Republic of)
Jieun Lee, SK Hynix, Inc. (Korea, Republic of)
Dongyoung Lee, SK Hynix, Inc. (Korea, Republic of)
Eungryong Oh, SK Hynix, Inc. (Korea, Republic of)
Ahlin Choi, SK Hynix, Inc. (Korea, Republic of)
DongSub Choi, KLA-Tencor Korea (Korea, Republic of)
DoHwa Lee, KLA-Tencor Korea (Korea, Republic of)
Sanghuck Jeon, KLA-Tencor Korea (Korea, Republic of)
Jungtae Lee, KLA-Tencor Korea (Korea, Republic of)
Seongjae Lee, KLA-Tencor Korea (Korea, Republic of)
Zephyr Liu, KLA-Tencor Korea (Korea, Republic of)
Jeongpyo Lee, KLA-Tencor Korea (Korea, Republic of)
John C. Robinson, KLA-Tencor Corp. (United States)

Published in SPIE Proceedings Vol. 10585:
Metrology, Inspection, and Process Control for Microlithography XXXII
Vladimir A. Ukraintsev, Editor(s)

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