Sakae Nakatsuka

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

Fabrication of 8 in. high-performance continuous diamondlike carbon (DLC) 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 CrNx 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 CrNx 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 ±5% with a 280-nm-feature size in a 135×43 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-thi...

Fabrication of complete 8 in. stencil mask for electron projection lithography

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 ±20 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 SF6 and CHF3 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 ...

Performance improvement of diamondlike carbon membrane masks for electron projection lithography

This article describes the fabrication of eight-inch continuous membrane masks with a 15‐nm-thick support membrane for electron projection lithography (EPL). 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 0.5Pa chamber pressure. Long-term membrane stress stability of Si-added extremely thin membranes were particularly improved. It was less than 3MPa in elapsed times of 400h. The zero-loss electron transmittance for the fabricated 15‐nm-thick membran...

Stencil mask technology for electron-beam projection lithography

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.

25nm pitch master and replica mold fabrication for nanoimprinting lithography for 1Tbit/inch 2 bit patterned media

Nanoimprint Lithography and a mold, mold replication from an EB master mold as well, those are essential for a large-scale production of bit patterned media. 1Tbit/inch2 (bit pitch 25nm) areal density on a 2.5inch HDD media, it is feasibility demonstration target all the media makers and the HDD makers are aiming at. This paper describes difficulties we faced, and solutions we established by designing and optimizing materials and process, to fabricate 25nm pitch master mold by EBL as well as working replica mold by NIL.

Master mold and working replica fabrication for nano-imprinting lithography for 1Tbit/inch2 and 25nm pitch bit patterned media

Bit Patterned Media (BPM) is essential of HDD media areal density increase, which will be combined with heatassisted magnetic recording (HAMR) eventually for thermal diffusion prevention. 1Tbit/inch2 areal density is the first demonstration target, which is 25nm pitch hole array, for the BPM development. Nano-Imprinting Lithography (NIL) is indispensable too, so molds as well, for the BPM large-scale production for throughput. At the beginning, 52nm pitch and below was successfully made on quartz master-mold. However, by our comprehensive development and improvement in material and process, we successfully fabricate 25nm pitch master-mold by EB Lithography, 25nm pitch working-replica by Nano-Imprinting Lithography as well.