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.

We fabricated an 8 in. stencil mask having the complementary pattern of the 70 nm rule system-on-chip device. The 8 in. stencil mask was realized from the development of a mask substrate fabricated by using the sputtering method to form a scattering silicon membrane and an intermediate stopper layer. The intermediate layer material, which functions as an etching stopper, was CrNx. This material has demonstrated high performance in stencil mask fabrication, which is described in detail. The stress in the CrNx could be controlled within Ϯ20 MPa by adjusting the deposition condition. The deposited silicon membrane stress could be easily adjusted in the range of 0-10 MPa. The etching selectivity, when the substrate backside etching was performed, was over 1000 under the low bias power. When the deep etching process was performed using SF 6 and CHF 3 etching gases for the mask pattern formation, the Si/CrNx etching selectivity was over 100 under the low bias power condition. The mask substrate, which is made up of a 2-m-thick deposited silicon membrane and 0.35-m-thick CrNx stopper layer, enabled an 8 in. stencil mask to be fabricated for use with electron projection lithography. In complementary mask split, we used ''M-Split'' which was developed by Selete and ISS as a pattern split software.

Articles you may be interested in Thermal analysis of diamondlike carbon membrane masks in projection electron-beam lithographyThis article describes the fabrication of eight-inch continuous membrane masks with a 15-nm-thick support membrane for electron projection lithography ͑EPL͒. In order to develop an extremely thin support membrane with a tensional stress, two techniques were applied; one is a low pressure deposition process to improve the membrane bulk density, and the other is Si addition during the conventional carbon membrane deposition for improving the atomic distance mismatch between substrate and deposited film, and also to address the membrane volume strain cause by the rise in the tensional stress under the low pressure deposition condition. By using Si-additional techniques, an extremely thin membrane with a tensional stress was formed under the conditions of less than 0.5 Pa chamber pressure. Long-term membrane stress stability of Si-added extremely thin membranes were particularly improved. It was less than 3 MPa in elapsed times of 400 h. The zero-loss electron transmittance for the fabricated 15-nm-thick membrane mask was measured to be 70.4%. Due to the development of an extremely thin membrane with high zero-loss electron transmittance of more than 50%, our high-performance membrane masks are superior to the complementary stencil masks in terms of exposure throughput.

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