PROCESS FOR HYBRID PHASE-SHIFTING MASK FABRICATION

Publishing Venue

Motorola

Related People

Abstract

The fabrication of state-of-the-art integrated circuits requires imaging of sub-O.5 micron features to increase both circuit density and device performance. The ability to print miniium feature size is often limited by the resolution of the available optical tool. Phase-shitbig pro- vides a way to extend the performance of both existing and new optical tools by improving resolution, depth of focus, exposure latitude, and resist sidewall profdes. To take advantage of the capabilities provided by phase- shifting, masks with well-defined, tightly controlled imag- ing characteristics must be produced.

MOTOROLA INC. Technical Developments Volume 19 March 1993

PROCESS FOR HYBRID PHASE-SHIFTING MASK FABRICATION

by Fourmun Lee and Tom Zirkle

   The fabrication of state-of-the-art integrated circuits requires imaging of sub-O.5 micron features to increase both circuit density and device performance. The ability to print miniium feature size is often limited by the resolution of the available optical tool. Phase-shitbig pro- vides a way to extend the performance of both existing and new optical tools by improving resolution, depth of focus, exposure latitude, and resist sidewall profdes. To take advantage of the capabilities provided by phase- shifting, masks with well-defined, tightly controlled imag- ing characteristics must be produced.

  Phase-shiiing masks which combine chrome and chromeless structures (hybrid chromeless phase-shifting mask) offer the ability to print the wide variety of fea- ture sizes and geometries needed to produce random- logic devices such as gate arrays and Iriicroprocessors. The process flow shown in Figure 1 provides a method to fabricate a hybrid chromeless phase-shift mask. The method described is a self-aligned process which allows fabrication of phase-shift structures with very tight CD and alignment tolerances which is beyond the capability of current mask making tools.

  In this fabrication process, the starting material is a standard chrome-covered quartz blank coated with a layer of e-beam or optically sensitive resist. Depending on

the method of data preparation, this resist layer can be positive or negative acting. The resist layer is exposed in the patterning tool and developed to create openings in selected areas of the mask blank. The resist pattern is then used as a ste...