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Proceedings Paper

60-seconds puddle time: a tradition to overcome in CA resists: process optimization and defect elimination
Author(s): Eitan Shalom; Shaike Zeid
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Paper Abstract

The develop process of traditional Novolac I-line resists with 2.38% TMAH developers was optimized at 60 second puddle time. This process was embedded in the lithographers' tradition, and so it was transferred to newer resist technologies i.e. CA resists. The dissolution rate of exposed I-line resists is in the order of 1000A/sec, while KrF resists have dissolution rate of ~12,000A/sec, and ArF resists at ~60,000A/Sec. The resist thickness of KrF and ArF resists is usually less than 0.5 micron, which means that the exposed film is dissolved within a fraction of the first second. The extended exposure of the resist features to developer was found to be a major reason for defects described as flying lines in center. There are two routes to eliminate the extended development of the resist: one is to dilute the developer as a method for improving the contrast and reducing the dissolution rate. This approach is very demanding and involves renewing the OPE data package, adding a new line to the tracks with a new material that is not a standard developer, but a special dilution. The other option is reduce develop time in order to minimize the attack on the resist-substrate interface, and resist edge. Experiments were run at 10, 20, 25 and 40-second puddle time, showing only a minor increase in exposure energy is necessary to reach CD target. OPE data was checked by simulation and SEM measurements, showing no significant difference between 60 and 25 second puddle time. Reducing puddle time improved defect density and eliminated the phenomenon of flying lines in the center.

Paper Details

Date Published: 15 April 2008
PDF: 10 pages
Proc. SPIE 6923, Advances in Resist Materials and Processing Technology XXV, 69233W (15 April 2008); doi: 10.1117/12.772558
Show Author Affiliations
Eitan Shalom, Tower Semiconductor Ltd. (Israel)
Shaike Zeid, Tower Semiconductor Ltd. (Israel)

Published in SPIE Proceedings Vol. 6923:
Advances in Resist Materials and Processing Technology XXV
Clifford L. Henderson, Editor(s)

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