Browse Prior Art Database

Registerable Multilayer Mask Fabrication Technique

IP.com Disclosure Number: IPCOM000042913D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Peressini, PP: AUTHOR [+3]

Abstract

Normally E-beam exposure generated masks rely on accurate table placement (via laser interferometer) to provide accurate chip placement. Mask-to-mask overlay accuracy using this technique is limited. A more repeatable method is to reference all masks which must register to one another to a "footprint" on the mask to which each written chip can be registered via backscattered electrons. This technique promises to reduce the overlay error. The "footprint" is normally etched or transferred into the mask substrate utilizing a separate lithographic process, i.e., coat the substrate with photoresist, image the "footprint", transfer the "footprint" into the mask substrate, strip the resist, clean the substrate, and fabricate the mask in the conventional manner.

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Registerable Multilayer Mask Fabrication Technique

Normally E-beam exposure generated masks rely on accurate table placement (via laser interferometer) to provide accurate chip placement. Mask-to-mask overlay accuracy using this technique is limited. A more repeatable method is to reference all masks which must register to one another to a "footprint" on the mask to which each written chip can be registered via backscattered electrons. This technique promises to reduce the overlay error. The "footprint" is normally etched or transferred into the mask substrate utilizing a separate lithographic process, i.e., coat the substrate with photoresist, image the "footprint", transfer the "footprint" into the mask substrate, strip the resist, clean the substrate, and fabricate the mask in the conventional manner. The standard technique suffers from a number of drawbacks: 1) increased process steps and associated induced defects and cost, and 2) every mask becomes a re-worked plate which can cause pinhole problems, adhesion problems, etc. This article discloses a technique which eliminates the problems associated with the conventional process. This new technique comprises the following steps: 1) Coat with photoactive resist which will also serve as the multilayer underlay (Fig. 1). 2) Image the footprint (Fig. 2). 3) UV harden and post bake (for example, 200 C); the Cr may now be etched (if desired). 4) Coat photoactive layer for chip geometry resolution (Fig. 3). 5) Write...