Cleaning of tin debris by reactive ion etching in a discharge-produced EUV plasma source
type: CreativeWork
description: Extreme ultraviolet lithography (EUVL) is a promising candidate for the next generation of lithography technique to continue Moore's law. Moore's law has been upheld by shrinking the feature size on devices and driving the development of faster and denser integrated chips. The short wavelength (13.5±0.2 nm) of EUV light enables EUVL to improve the resolution (the minimum feature size) far beyond the conventional limit in current high volume manufacturing. EUV light can be generated by making hot (Te ∼ 30 eV) plasma, and collected by optical mirrors in vacuum. During the light generation process, energetic ions or neutral debris are emitted from the plasma in addition to the desired light. The contamination by such debris will critically affect the life time of the mirror as well as the total light output. The contamination by debris is more serious when making an EUV-emitting plasma with tin (Sn). Sn has a high conversion efficiency leading to higher EUV power, but easily condenses on the surface of all the components in an EUV source system. In this work, a method was investigated of cleaning Sn contamination by reactive ion etching (RIE) using chlorine plasma. The primary investigation revealed details of etch rate selectivity between Sn and Ru, the mirror surface material. The optimal condition, to remove Sn several hundred times faster than Ru with minimum influence on Ru, was identified and other important findings having effects on etching were revealed. By cleaning the Sn-contaminated Ru surface using a plasma etching method, it was shown that Sn can be removed from Ru surface without damaging the Ru surface. A simple surface reaction model of Sn reactive ion etching using chlorine plasma was proposed and validated through the measured etch rate. The model successfully shows that etch rate depends on plasma density and the bias potential in reactive ion etching. Based on the promising preliminary etch rate study, Sn samples were cleaned in a mock-up collector…
abstract: Extreme ultraviolet lithography (EUVL) is a promising candidate for the next generation of lithography technique to continue Moore's law. Moore's law has been upheld by shrinking the feature size on devices and driving the development of faster and denser integrated chips. The short wavelength (13.5±0.2 nm) of EUV light enables EUVL to improve the resolution (the minimum feature size) far beyond the conventional limit in current high volume manufacturing. EUV light can be generated by making hot (Te ∼ 30 eV) plasma, and collected by optical mirrors in vacuum. During the light generation process, energetic ions or neutral debris are emitted from the plasma in addition to the desired light. The contamination by such debris will critically affect the life time of the mirror as well as the total light output. The contamination by debris is more serious when making an EUV-emitting plasma with tin (Sn). Sn has a high conversion efficiency leading to higher EUV power, but easily condenses on the surface of all the components in an EUV source system. In this work, a method was investigated of cleaning Sn contamination by reactive ion etching (RIE) using chlorine plasma. The primary investigation revealed details of etch rate selectivity between Sn and Ru, the mirror surface material. The optimal condition, to remove Sn several hundred times faster than Ru with minimum influence on Ru, was identified and other important findings having effects on etching were revealed. By cleaning the Sn-contaminated Ru surface using a plasma etching method, it was shown that Sn can be removed from Ru surface without damaging the Ru surface. A simple surface reaction model of Sn reactive ion etching using chlorine plasma was proposed and validated through the measured etch rate. The model successfully shows that etch rate depends on plasma density and the bias potential in reactive ion etching. Based on the promising preliminary etch rate study, Sn samples were cleaned in a mock-up collector…
author: Shin, Hyung Joo
language: en
keywords: Extreme Ultraviolet (EUV) source, Plasma, Chlorine, Tin, Cleaning, Etching, Contamination, Mirror, Model
date published: 2010-01-06T16:39:30Z
date modified: 2026-07-22T22:25:08Z
provider: University of Illinois - Urbana-Champaign
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Illinois at Urbana-Champaign

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2142/14691