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International SEMATECH: A Focus on the Photomask Industry by Wally Carpenter, International SEMATECH, Inc. (*IBM Corporation Assignee)
It is well known that the semiconductor industry continues to drive performance improvements through lithography resolution development. Further, the International Technology Roadmap for Semiconductors (ITRS) timing continues to be driven aggressively, resulting in less inherent lithography resolution advantage against the desired linewidth. The effect has been to require significantly tightened photomask specifications with aggressive timing constraints. Mask Error Enhancement Factors (MEEF) and wavelength choices are driving a need for multiple options for the photomask end user, which include Attenuated and Alternating Phase Shifting Masks. The compounded effect of the roadmap move-in results in extreme measures being needed to ensure the photomask infrastructure will be ready for these demands.
Introduction
Historically, the semiconductor industry benefited from the fact that the lithography wavelength was several times shorter than minimum linewidth. As we approach the 130 nm technology node, however, we find we will be using 193 nm lithography. Indeed, we will need to use 193 nm lithography to introduce the 100 nm node, gaining the benefit of 157 nm lithography some time after the first 100 nm production occurs. These continue the trend established at the 180 nm node, using 248 nm lithography, where wavelength exceeds linewidth. The impact of this trend can be seen in the declining k1 represented in Figure 1. The k1 that will be available for the next few technology nodes are shown by the heavier line.
It is this declining k1 that has fostered the Mask Error Enhancement Factors and the growing dependence on the mask as an integral optical element, not just as a mask. We find we must incorporate into the mask materials and features that enhance the inherent resolution capability of the exposure tool. While this enhancement is required on only critical levels, the percentage of levels that are critical and need enhancement is increasing with each succeeding technology node. For the 100 nm mask set, it is quite reasonable to expect several levels will require a weak phase shift mask, with optical proximity correction, and several levels will require strong phase shift masks. The production of phase shift masks, 0.6 157nm 193nm
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k1 with NA = 0.8
This article will review the changes and trends that have occurred in the ITRS and their compounded impact on the photomask industry. Critical issues will be identified and addressed at a photomask industry level. Also, an overview of International SEMATECH’s roadmap will focus on key critical issues in the photomask industry.
Exposure Wavelength
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Technology Node Figure 1. k 1 trend against technology node.
Autumn 2000
Yield Management Solutions
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