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Surface Treatment of Discharge Electrodes to Extend the Lifetime of Excimer Lasers

IP.com Disclosure Number: IPCOM000124945D
Publication Date: 2005-May-13
Document File: 3 page(s) / 68K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that treats the surface of excimer laser discharge electrodes. The disclosed method protects the electrodes from erosion caused by the high energy and high temperature fluorine gas plasma during the lasing process. Benefits include extending the life of excimer lasers.

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Surface Treatment of Discharge Electrodes to Extend the Lifetime of Excimer Lasers

Disclosed is a method that treats the surface of excimer laser discharge electrodes. The disclosed method protects the electrodes from erosion caused by the high energy and high temperature fluorine gas plasma during the lasing process. Benefits include extending the life of excimer lasers.

Background

Because of their high brightness and their narrow spectrum, excimer lasers are the light source for DUV micro-lithography. In the laser chamber, the high electric field creates a high density fluorine gas compound plasma. The excited compound plasma is the lasing media of the DUV excimer lasers (KrF for 248nm wavelength and ArF for 193nm wavelength).

The performance of the fluorine gas-based laser degrades over time, mainly due to the erosion of fluorine gas plasma on the discharge electrodes. Cleaning the laser chamber and replacing the electrodes are required after several billion pulses of operation. Therefore, maintenance costs and the correlated down time become central concerns in the lithographic manufacturing environment.

Current excimer lasers use copper alloys (e.g. brass) as the electrode material. They are relatively easy to erode under high power and high temperature fluorine plasma. Current proposals to extend the electrode lifetime include:

§         Reducing the plasma energy. This can increase the lifetime but impacts the process throughput.

§         Using hard-to-erode metal alloys (e.g. stainless 309Cb and NiCrMo alloys) for the electrodes. This increases the material and manufacturing costs, which is not preferable in terms of reducing the total cost of ownership.

General Description

The disclosed method uses a unique and cost effective approach to extend the lifetime of excimer lasers by surface treating the discharge electrodes with conductive materials; this is done to protect them from the erosion of high energy fluorine plasma under the high temperatures. Three different materials/methods of surface treatment to the electrodes are presented. An outline of each process, coating materials, the related technical advantages, and the chances of success of each method are included below (see Figure 1). Engineering...