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Piezoelectric Electrostatic Chuck for Mask Handling and Improving Blank Flatness

IP.com Disclosure Number: IPCOM000124066D
Publication Date: 2005-Apr-07
Document File: 3 page(s) / 107K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for a new type of electrostatic chuck (e-chuck) for handling masks used in lithography processes. Benefits include a solution that localizes the correction of the mask and/or e-chuck flatness.

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Piezoelectric Electrostatic Chuck for Mask Handling and Improving Blank Flatness

Disclosed is a method for a new type of electrostatic chuck (e-chuck) for handling masks used in lithography processes. Benefits include a solution that localizes the correction of the mask and/or e-chuck flatness.

Background

Currently, one cannot chuck a mask (using an electrostatic chuck) to meet the flatness specifications required by an exposure tool, which is usually less than 100nm (peak-to-valley flatness) over a six inch square mask. The current solution is an open-loop, non-active e-chuck design that generates a lateral electrostatic force in the thickness of a mask. However, this solution is not complete, because there is no e-chuck that provides less than 100nm peak-to-valley flatness.

Currently available e-chucks create a chucking mechanism by forming a lateral electrostatic field in the thickness direction of the mask. Commercial masks used in lithography come with thin films on them (usually chromium) that cause deformations in the mask, not to mention non-flatness due to the polishing of the mask substrate (i.e. quartz); this non-flatness is much more critical in the case of extreme-ultraviolet lithography (EUVL) masks that contains multiple layers. This effect becomes much more serious when coupled with the non-flatness of the e-chuck surface.

General Description

The disclosed method uses a piezoelectric chuck (or piezoelectric pieces bonded on one surface of the chuck), for handling masks used in lithography processes. The patterned piezoelectric elements cause the e-chuck and/or e-chucked mask to be flattened by a flatness tool. The disclosed method enables the user to set a custom flatness for each mask that is chucked.

Figure 2a shows the piezoelectric layer placed under the e-chuck layer. The piezoelectric is thickness po...