Stencil mask technology for electron-beam projection lithography

摘要

Some new electron-beam projection lithography techniques have been proposed after cell projection (CP) lithography. To make these lithography techniques practicable, development of the stencil mask is an indispensable key technology. Due to reduction in mask magnification, requirements for the stencil mask becomes sever in comparison with that for CP lithography. For example, the stress of the membrane with mask pattern must be controlled within 10 MPa in terms of the pattern image placement (IP) accuracy, and the membrane thickness must be 2 /spl mu/m or thinner from a viewpoint of the pattern aspect ratio. To solve these issues, we developed a new mask substrate with a CrNx intermediate etching stopper, and found that the CrNx material had an etching selectivity of over 1000 enough for the backside etch process. In addition, the internal stress of the CrNx layer can be easily controlled within /spl plusmn/20 MPa by deposition condition adjustment. Also, by using the CrNx stopper layer, membrane warping during the mask fabrication process did not occur. As a result, mask productivity was greatly improved.