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Proceedings Paper

Aerial image-based mask inspection: a development effort to detect what might impact printing image quality on wafers
Author(s): Roman Liebe; Henning Haffner; Shirley Hemar; Anja Rosenbusch; Jerry Xiaoming Chen; Franklin D. Kalk
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Paper Abstract

The industry roadmap for IC manufacturing at design rules of 90nm and below foresees low k1-factor optical lithography at 193nm exposure wavelength. Aggressive model-based OPC and Phase Shift Mask technology are being used more and more frequently in order to achieve the extremely tight mask CD specifications required by 90nm technology node. State-of-the-art mask inspection is challenged to detect CD defects close to metrology resolution. Inspection of OPC and PSM masks is critical; OPC feature dimensions are usually near or below the resolution limits of mask exposure. In addition, chrome defects can be semitransparent and change the intensity of light on the wafer. In this paper aerial-image based mask inspection is investigated and presented. The concept inspects a given mask based on its aerial image with selected wafer exposure conditions, thus 'finds only defect which will print'. This paradigm shift in mask inspection philosophy provides the unique opportunities of verifying and controlling the entire aerial image generated by the inspected mask. As reticle enhancement techniques like OPC and EAPSM are designed to enhance the aerial image of a mask, this concept offers a comprehensive way of inspecting these techniques. The focus of the inspection is shifted from detecting every single minor change on mask to detecting what on mask could possibly impact the printing image quality on the wafer. The focus of the paper is to analyze the impact of different exposure and lithography process conditions onto the inspection sensitivity. The standard defect sensitivity and runability test mask UIS10 and other advanced real production masks were printed under different exposure and process conditions resembling production-worthy 193nm lithography processes. The masks then were inspected using Etec's aerial image-based inspection concept. Detection sensitivities and CD variations on the wafer are analyzed and compared.

Paper Details

Date Published: 2 June 2003
PDF: 8 pages
Proc. SPIE 5038, Metrology, Inspection, and Process Control for Microlithography XVII, (2 June 2003); doi: 10.1117/12.483535
Show Author Affiliations
Roman Liebe, Infineon Technologies AG (Germany)
Henning Haffner, Infineon Technologies AG (Germany)
Shirley Hemar, Etec Systems, Inc. (Israel)
Anja Rosenbusch, Etec Systems, Inc. (Israel)
Jerry Xiaoming Chen, DuPont Photomask, Inc. (United States)
Franklin D. Kalk, DuPont Photomask, Inc. (United States)

Published in SPIE Proceedings Vol. 5038:
Metrology, Inspection, and Process Control for Microlithography XVII
Daniel J. Herr, Editor(s)

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