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Proceedings Paper

Yield Improvement With Pellicalised Masks In Projection Printing Technology
Author(s): A. Rangappan; Chuck Kao
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Paper Abstract

Photomask limited yields in LSI and VLSI processes are examined in this paper. Mask defects are classified into two catagories i.e., soft and hard mask defects. Theoretical modelling indicates a substantial yield improvement with pellicle protected masks. In 1:1 projection technology soft mask defects are the predominent cause of mask limited yield. Use of pellicles eliminates the effect of soft defects up to 100 microns in size, does not cause a degradation of image quality or dimensional control, prolongs mask life, and saves considerable labour and cost in maintaining high quality masks. Pellicle mounting, inspection, and handling techniques used are described. Very large die with 3 micron, NMOS, Si-gate technology are used to determine the actual yield improvement. Lots were processed using identical sets of masks of which one set was pellicle protected. Defect density at each process step and final probe yield are statistically analysed to show the individual contributions of hard mask defects, soft mask defects, and random process defects to the overall device yield. Actual yield increase data is presented. This pellicle technology is directly applicable to 10:1 stepping exposure systems where high soft mask defect density could be a more severe problem than in 1:1 projection systems.

Paper Details

Date Published: 13 September 1982
PDF: 8 pages
Proc. SPIE 0334, Optical Microlithography I: Technology for the Mid-1980s, (13 September 1982); doi: 10.1117/12.933560
Show Author Affiliations
A. Rangappan, Xerox Corporation (United States)
Chuck Kao, Xerox Corporation (United States)

Published in SPIE Proceedings Vol. 0334:
Optical Microlithography I: Technology for the Mid-1980s
Harry L. Stover, Editor(s)

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