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Method for the use of piezoelectric actuators for hard pellicle positioning for 157-nm lithography

IP.com Disclosure Number: IPCOM000010739D
Publication Date: 2003-Jan-15

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for the use of piezoelectric actuators (PAs) for hard pellicle positioning for 157-nm lithography. Benefits include improved functionality and improved design flexibility.

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Method for the use of piezoelectric actuators for hard pellicle positioning for 157-nm lithography

Disclosed is a method for the use of piezoelectric actuators (PAs) for hard pellicle positioning for 157-nm lithography. Benefits include improved functionality and improved design flexibility.

Background

        � � � � � Conventional reticle packages protect the chrome features of the mask by placing a pellicle membrane above the surface of the mask (see Figure 1). Because the pellicle is positioned well above the focal plane, particles that fall towards the mask are stopped on the pellicle and are not printed on the wafer surface. N2 purging of the reticle is required for 157-nm lithography due to the high absorbance of O2 and H2O in the atmosphere. For clarity, the figure assumes the entire mask is exposed simultaneously rather than being scanned as is typical of lithographic tools.

� � A simplified view of the 157-nm reticle/pellicle assembly does not include the N2 purge connections for clarity (see Figure 2). The circuit layout is typically patterned in chrome on the surface of the quartz mask.� Running around the perimeter of the quartz mask is the frame, which protects the chrome features and positions the overhanging soft pellicle membrane well off the surface of the chrome features.� With soft pellicles, an adhesive is typically applied around the entire upper perimeter of the frame to bond the pellicle to the four sides of the frame.� This design enables the entire reticle/pellicle assembly to be N2 purged and keeps the soft pellicle membrane well away from the focal plane of the exposure tool. Particles that fall onto the pellicle surface are not printed on the wafer surface.

Description

        � � � � � The disclosed method is the use of piezoelectric actuators (PAs) for hard pellicle positioning for 157-nm lithography. The method enables the precise positioning of hard pellicles within the reticle/pellicle assemblies.

        � � � � � The key elements of the method include:

•        � � � � Use of PAs mounted within the reticle frame or pellicle

•        � � � � Use of the PA as force sensors during the mounting of the hard pellicle to ensure that forces are applied uniformly

•        � � � � Application of the required voltage to the PAs to enable them to expand or contract and correctly position the hard pellicle relative to the underlying quartz mask

•        � � � � Modification of 157-nm exposure systems to supply the required voltages to the reticle/pellicle assemblies when they are mounted within the exposure system

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved functionality due to being able to control the position (tilt, bow, and z-offset) of the hard pellicle

•        � � � � Improved functionality due to adjusting the PA voltages to flatten an S-shaped hard pellicle and to control the position of the pellicle surface in relation to the exposure slit

•        � � � � Improved design flexibility due to applicability to157-nm...