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Method for a double-exposure technique with a reverse tone-mask pattern or trim mask for flare compensation in lithography

IP.com Disclosure Number: IPCOM000010024D
Publication Date: 2002-Oct-09
Document File: 4 page(s) / 150K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a double-exposure technique with a reverse tone-mask pattern or trim mask for flare compensation in lithography. Benefits include improved performance.

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Method for a double-exposure technique with a reverse tone-mask pattern or trim mask for flare compensation in lithography

Disclosed is a method for a double-exposure technique with a reverse tone-mask pattern or trim mask for flare compensation in lithography. Benefits include improved performance.

Background

              Flare in photolithography systems can occur from various sources, including:

•             Unwanted sources of light reflecting off the lens column

•             Inhomogenieties in the lens, typically with deep ultraviolet (DUV) systems

•             Rough mirrors, typically with extreme ultraviolet (EUV) systems

              Flare impact is long-range. The imaging in one part of the die is dependant on the pattern density around it. If the pattern density is not uniform, within-die flare variation results in within-die color display (CD) variation. In the case of conventional DUV systems where the overall flare level is low, large variation occurs across the die, even without a pattern (see Figure 1).

              Conventionally, no known method for compensation of pattern density variation exists other than dummification.

              However, dummification has limits in logic patterns. Despite contrary efforts, pattern density variations result in within-die CD variations. In the case of conventional DUV systems, flare levels are low enough that they do not significantly impact patterning performance.

      PL1 masks are clear field masks where the features are dark and the background is clear. The reverse tone is a dark field mask with clear features.

General description

              The disclosed method compensates for pattern density variation by exposing the layer with a mask that has a reverse tone pattern and then makes the regular exposure. The result is uniform pattern density and reduced flare variation.

              The key elements of the disclosed method include:

•             Regular mask and a reverse tone mask

•             Second exposure step with a selective reverse tone mask

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