Registerable Multilayer Mask Fabrication Technique
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04
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.