PSM alignment for Sigma7300: signal quality and resist effects from using the writing DUV laser light, spatial light modulator, and a CCD camera as a measurement tool for 2:nd layer alignment metrology

Thomas Ostrom; Sten Lindau; Mats Ekberg; Hans A. Fosshaug; Raoul Zerne

doi:10.1117/12.535830

24 May 2004 PSM alignment for Sigma7300: signal quality and resist effects from using the writing DUV laser light spatial light modulator and a CCD camera as measurement tool for 2:nd layer alignment metrology

Thomas Ostrom, Sten Lindau, Mats Ekberg, Hans A. Fosshaug, Raoul Zerne

Author Affiliations +

Proceedings Volume 5375, Metrology, Inspection, and Process Control for Microlithography XVIII; (2004) https://doi.org/10.1117/12.535830
Event: Microlithography 2004, 2004, Santa Clara, California, United States

Abstract

One of the sub-functions in the Micronic Sigma 7300 mask writer is the 2:nd layer alignment system for writing of phase shift masks. The strategy chosen for performing PSM alignment is to use the DUV writing laser together with the spatial light modulator (SLM) to create a light stamp image, which is reflected on the first layer alignment marks. The reflected image is captured and measured with a DUV-sensitive CCD camera. Using the writing laser has many benefits since there is no position offsets coming from misalignment of multiple laser sources. The anti-reflection (AR) function in chemically amplified resists (CAR), bottom anti-reflex coatings (BARC) and top anti-reflex coatings (TARC) reduces reflectance for 248 nm incoming light. This could reduce the signal strength and accuracy of the alignment system as the 248 nm laser is used for the alignment. The paper focuses mainly on two issues, image contrast at different resist thicknesses and image contrast when AR coatings are used. The algorithm measuring the fist layer alignment mark positions is also described. The studies of this and results of the final PSM alignment system show that Micronic has found an efficient way of dealing with these issues.

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Thomas Ostrom, Sten Lindau, Mats Ekberg, Hans A. Fosshaug, and Raoul Zerne "PSM alignment for Sigma7300: signal quality and resist effects from using the writing DUV laser light spatial light modulator and a CCD camera as measurement tool for 2:nd layer alignment metrology", Proc. SPIE 5375, Metrology, Inspection, and Process Control for Microlithography XVIII, (24 May 2004); https://doi.org/10.1117/12.535830

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