Multilayer Membranes For X-Ray Lithography

Abstract

AbstractMultilayer x-ray lithography membranes were designed and fabricated. Consisting of alternating layers of SiC and SiNx, the membranes were designed to have low reflectance for improved optical alignment of x-ray masks, high fracture strength, superior chemicaletch resistance, and high manufacturing yield. The membranes were prepared from multilayer coatings deposited on silicon wafers in an electron cyclotron resonance chemical vapor deposition system. Membranes with less than 5% reflectance over 150 nm bandwidths were made. External SiNx layers increased the chemical etch resistance of the membranes. The fracture strength was 2–3 times that of SiC, and the membrane yield was 50% higher than that of single-layer SiC. Field-emission SEM of the multilayer coating cross-section showed the presence of 20–150 nm defects near the layer interfaces. The layering confines or stabilizes the defects, thereby increasing the membrane yield and fracture strength.