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Method for EUVL mask particle protection inside an EUV exposure tool

IP.com Disclosure Number: IPCOM000042254D
Publication Date: 2005-Feb-03
Document File: 8 page(s) / 134K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for extreme ultraviolet lithography (EUVL) mask particle protection inside an EUV exposure tool. Benefits include improved functionality and improved yield.

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Method for EUVL mask particle protection inside an EUV exposure tool

Disclosed is a method for extreme ultraviolet lithography (EUVL) mask particle protection inside an EUV exposure tool. Benefits include improved functionality and improved yield.

Background

              EUVL masks can be contaminated by particles during mask exposure in an EUV exposure tool.

              The conventional optical mask uses a pellicle, which is a thin organic membrane on a metal frame, with a stand-off distance of <6 mm. The pellicle is mounted on the clean optical mask to cover the clean mask-patterned region. Particles that fall onto the pellicle do not print (unless the particle is extremely large) because the image is out-of-focus due to the greater pellicle frame stand-off distance.

              Due to light absorption of all solid materials at EUV wavelength, no pellicle material exists that can be used for an EUVL mask. The conventional pellicle technology is not extendible to EUVL mask.

General description

              The disclosed method prevents particle contamination on an EUVL mask during EUV exposure. The method is comprised of three options to protect the EUVL mask. Two sideguard parallel plates comprise a particle broom. A protection plate is underneath the particle broom parallel to the mask scanning stage. This plate has small openings of 500 µm to several millimeters. A series of parallel plates form an enclosure with only small openings between the individual plates to provide maximum protection.

              The key elements of the disclosed method include:

•             Sideguards
•             Sticky adhesive

•             Parallel protection plates with openings for EUVL light exposure

•             Optional thin Si membrane (<100A) for covering the openings in the protection plates

Advantages

              The disclosed method provides advantages, including:
•             Improved functionality due to preventing particles from falling onto the EUVL mask during exposure
•             Improved yield due to preventing contamination of the EUVL mask

Detailed description

              The disclosed method prevents particles from reaching an EUVL mask. The method includes the following protective features:

•             Particle broom

•             Under-broom protection plate

•             Optional silicon membrane

•             Optional half-cycle scanning

•             Series of parallel plates

Particle broom

Two sideguards on the mask stage comprise a particle broom. Its sticky sides retain particles on contact. Because the sideguards are not exposed to EUV light, the only requirement on the sideguard material and adhesive is to meet the material out-gassing specification under vacuum conditions. The particle broom can be mounted on the e-chuck that is mounted on the scanning stage (see Figure 1).

              Alternatively, the particle broom can be mounted directly on the scanning stage (see Figure 2).

              The effectiveness of the particle broom relies on...