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Proceedings Paper

Improve the efficiency of the inspection process via a thorough control of the scanning focus
Author(s): Ernesto Villa; Luca Sartelli; Hiroyuki Miyashita
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Paper Abstract

Requirements coming from the customer, as well as internal needs of improvements consequent to the increasing complexity of the layout of the newest devices, lead to the necessity of exploring all the potential improvements achievable at the mask manufacturing inspection process. A key point to manage for the better DB inspections is that of being able to achieve a proper matching between the images to be compared, tasks which is accomplished by the tool architecture by means of a pre-swath calibration process on which the quality of the focus is playing a relevant role. From here the decision to focus on this parameter aiming of working out and evaluate a different approach to be used to set the scanning focus on the inspection tool moving from the vendor theory based on the edge speed on a specific test plate to a new one based on intensity measurements into specific features on a purposely designed test vehicle. A matter of relevant importance for mask makers, either for the smoothness of the inspection process or for the homogeneity of the quality of the products being delivered, but on which any tool vendor likes providing official commitments, is that of correlating the overall performance of similar tools. This was accomplished with the new approach with two different tools achieving optical images with similar grey scale distributions into the most critical features. Moreover, the improvement of the matching of the images being compared allows extending the usage of the tool for products for which the complexity of the layout forced the inspection with different pixels or with more advanced tools, with a positive impact either on costs or on the cycle time of the masks being delivered. A careful assessment-verification of the shadowing limitation induced by the frame of the pellicle was another task successfully carried out with the new methodology, with some improvement regarding the inspectable area. The extended its usage the wider the field of application will become, but few advantages can be appreciated since the beginning: the focus will be set on a production like layer, its choice will not be depending on a human decision, it will be a simple, fast and reliable process runable at any time and at any operating level.

Paper Details

Date Published: 14 October 2011
PDF: 16 pages
Proc. SPIE 8166, Photomask Technology 2011, 81662V (14 October 2011); doi: 10.1117/12.896570
Show Author Affiliations
Ernesto Villa, DNP Photomask Europe (Italy)
Luca Sartelli, DNP Photomask Europe (Italy)
Hiroyuki Miyashita, DNP Photomask Europe (Italy)


Published in SPIE Proceedings Vol. 8166:
Photomask Technology 2011
Wilhelm Maurer; Frank E. Abboud, Editor(s)

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