Fabrication of a continuous diamondlike carbon membrane mask for electron projection lithography

Abstract

Thermal analysis of diamondlike carbon membrane masks in projection electron-beam lithographyStress and image-placement distortions of 200 mm low-energy electron projection lithography masks Fabrication of 8 in. high-performance continuous diamondlike carbon ͑DLC͒ membrane masks for electron projection lithography is described. The mask substrate materials and structures were optimized by evaluating the lithographic performance of the mask. The optimum mask consists of a sandwich structure, consisting of a thicker DLC scatter/a CrN x etching stopper/and a thin DLC support membrane on a bulk silicon wafer. The internal stress of each film component can be controlled by adjusting the film deposition conditions. A DLC film can be easily etched by oxygen gas, and the CrN x etching stopper has a high etching durability. Highly accurate pattern properties can be obtained while also meeting performance requirements. The critical dimension accuracy of a DLC scatterer was less than Ϯ5% with a 280-nm-feature size in a 135ϫ43 mm field. The electron aperture transmittance of a 44-nm-thick DLC membrane, measured by energy and angular distribution analysis for membrane, was 13 times as high as the 150-nm-thick SiN x membrane.

Performance improvement of diamondlike carbon membrane masks for electron projection lithography

“…5 Moreover, it could be applied, not only to the etch stop layer for membrane formation, but also for the formation of mask patterns. For the etch stop material we selected a CrNx.…”

“…5 Figures 6͑a͒ and 6͑b͒ show the electron aperture transmittance evaluation results of formed support membranes with several membrane thicknesses and along with a 150-nm-thick SiNx membrane; all were normal-ized by a zero-loss peak of without specimen. Also exposure throughput of membrane masks with zero-loss electron transmittance of more than 50% is always enhanced in comparison to complementary stencil masks.…”

“…[3][4][5] We have fabricated complete eight-inch EPL stencil mask with complementary patterns of a 70 nm SoC design, named "Anaheim." We have been developing very reliable processes for making both types of EPL masks, namely, the stencil masks and the continuous membrane masks.…”

“…[3][4][5] We have fabricated complete eight-inch EPL stencil mask with complementary patterns of a 70 nm SoC design, named "Anaheim." 5 The zero-loss electron transmittance of the mask was measured to be 41%, although this number does not meet the requirement for the high-throughput exposure. 4,6,7 Using an EPL exposure tool, NSR-EB1A the pattern stitching accuracy of the complementary set was found to be within 20 nm.…”

Thermal analysis of diamondlike carbon membrane masks in projection electron-beam lithography

“…2,3 High-resolution printing through diamondlike carbon (DLC) membrane masks comparable to that using silicon stencil masks has been demonstrated. 1 Fabrication methods of these masks have been developed.…”