A new approach for optical patterning that interposes a liquid between an exposure tool's projection lens and a wafer to achieve better depth of focus and resolution over conventional projection lithography is known as "Immersion Lithography". As industry focus is getting shifted towards the liquid immersion lithography to manufacture the commercial immersion tools, study of fluid flow and distribution is getting very crucial. The focus of this experimental work was to capture fluid flow and distribution and meniscus behavior on both bare and photoresist-coated glass wafers as well as silicon wafers and address one of the major challenges of immersion; presence of bubbles in the liquid between the lens and the wafer.
A liquid meniscus is created by supplying water through a nozzle onto bare and photo-resist-coated silicon and glass wafer surfaces. This meniscus is formed in the gap between the nozzle end and top surface of the wafer. The meniscus behavior is studied by varying wafer speed, the gap between the nozzle and the wafer, and mass flow rate using high-speed photography. The characteristics of circular nozzle, rectangular nozzle and nozzle lens unit with integral supply and suction port were examined under a variety of operating parameters. Nozzle geometry is of interest in Liquid Immersion Lithography. The use of degassed water is explored in an effort to eliminate any gas evolution. The results indicate that the meniscus shape and the contact angle depend on the wafer surface. Also presence of water droplets on the incoming wafer surface may break meniscus and trap bubbles. This work provides important insight into the field of meniscus behavior and bubble influence in liquid immersion lithography.
Library of Congress Subject Headings
Meniscus (Liquids); Fluid dynamics; Immersion lithography; Microlithography; Water immersion
Department, Program, or Center
Manufacturing and Mechanical Engineering Technology (CAST)
Satish G. Kandlikar
S. M. Ramkumar
Sonawane, Kiran J., "Meniscus Studies in Water Immersion Optical Lithography at 193 nm" (2005). Thesis. Rochester Institute of Technology. Accessed from
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