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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) / 218K

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

•        � �...