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Method for carbon removal from optical surfaces

IP.com Disclosure Number: IPCOM000011519D
Publication Date: 2003-Feb-26
Document File: 3 page(s) / 66K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for carbon removal from optical surfaces. Benefits include improved functionality.

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Method for carbon removal from optical surfaces

Disclosed is a method for carbon removal from optical surfaces. Benefits include improved functionality.

Background

              A successful method is required for cleaning the optics and masks used in extreme ultraviolet light (EUVL) exposure tools. These optics and masks become coated with carbon that results from residual hydrocarbons in the EUVL exposure tool vacuum environment. Oxidation reactions can be used to remove this carbon, but surface oxidation can destroy the optics and masks. They are especially vulnerable when a protective capping layer is used that oxidizes, such as silicon.

              No conventional optics cleaning solution exists, but previous investigations have tried using atomic hydrogen or water vapor in the presence of EUV light to clean the surface (see Figure 1).

General description

              The disclosed method is carbon removal from optical surfaces. An electron beam and low-pressure water environment remove carbon from the surface of optics.

              The optic is put in a vacuum chamber with a low partial pressure of an oxidizer, such as oxygen gas or water vapor. The optic surface is irradiated by a scanning electron beam. The surface excitation caused by the electron beam leads the water to react with the graphitic carbon, forming volatile carbon oxides. The volatilization removes carbon from the optic surface.

Advantages

              The disclosed method provides advantages, including:

•             Improved functionality due to successfully cleaning the optical surface

Detailed description

              The disclosed method is carbon removal from optical surfaces. Carbon deposited on the silicon surface bonds wit...