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Cleaning Contaminants from EUV Mirrors

IP.com Disclosure Number: IPCOM000085002D
Publication Date: 2005-Mar-02
Document File: 2 page(s) / 142K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses low-energy electrons to remove contaminants from the surface of EUV mirrors. Benefits include an in-situ solution that can clean localized regions or the entire surface of the mirror.

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Cleaning Contaminants from EUV Mirrors

Disclosed is a method that uses low-energy electrons to remove contaminants from the surface of EUV mirrors. Benefits include an in-situ solution that can clean localized regions or the entire surface of the mirror.

Background

Lithium is used as a target material to produce EUV light for EUV lithography, by either laser produced plasma (LLP) or discharge produced plasma (DPP). However, a major problem with this approach is the contamination of the EUV collector mirrors, the first set of mirrors facing the LLP source. When the mirrors are contaminated with lithium debris or atoms on the surfaces, the reflectivity is reduced.

Currently, mechanical baffles are placed between the collector mirrors and the source
(see Figure 1); however this does not block all of the debris particles or vapor from contaminating the mirrors. In addition, there are no methods to clean the mirrors without taking them apart. Disassembling the mirrors is a major procedure that leaves the tool inoperable for many days.

General Description

The disclosed method uses low-energy electrons (about10-100eV) to stimulate the desorption of lithium atoms adsorbed on the mirror surfaces. Figure 2 shows a schematic description of the method in two types of collector mirrors. The electron source can range from simple filament types to field emitters. The source is mounted on a mechanical manipulator for positioning the source. A high current is desired for a more efficient cle...