We have improved the M-Split complementary mask pattern split program and our electron projection lithography (EPL) data conversion system to achieve a practical data processing time and data volume. The system was designed to rehierarchicalize the data, flattened after the subfield split, by extracting polygons that all have an identical shape as a cell. The M-Split stress check function was improved by using a normalized bending moment as a criterion. A clustered computing system was used to reduce the data processing time. The processing time for a complementary mask pattern split without rehierarchicalizing was reduced to 57 min by using the stress check function and a ten PC cluster system −3–10 times as fast as with commercially available EPL data conversion systems. We successfully fabricated a full-size 8 in. Si stencil mask consisting of 8000 subfields using the data for an actual 70 nm design-rule system on chip device to demonstrate the effectiveness of M-Split. With a higher performance PC cluster system and the rehierarchicalizing, we expect to further reduce the M-Split processing time to 10 min.
Thermionic emission properties of several kinds of refractory carbides, nitrides, and borides of the transition metals in the form of powder were investigated with a newly developed measuring device and evaluated by the figure of merit defined as the ratio of the effective work function to the working temperature at which the vapor pressure becomes 1 x 10(-5) Torr. There are several materials whose thermionic emission properties are better than those of tungsten or compatible to those of tungsten among the carbides and borides, such as TaC, HfC, ZrC, LaB6, and CeB6, as judged by the figure of merit. New preparation methods for carburization, nitriding, and boriding of the wires of matrix metals and alloys were successfully developed for using these materials as the cathode of the electron microscope. Other necessary techniques such as spot welding and electrolytic etching were also developed. From the brightness characteristics, it was found that some of carbides, carbide solid solutions, and borides such as HfC, ZrC (Ta0.8-0.7Hf0.2-0.3)C, TaB2, and HfB2 are very good emitters comparable to LaB6. It is emphasized that the work functions of the carbide-solid solutions (Ta0.8Hf0.2)C and (Ta0.7Hf0.3)C, which have low rates of evaporation at high temperature, show no remarkable rise as compared with that of HfC, so that their figures of merit are better than that of HfC. Feasibility of providing good cathodes with HfC and (Ta0.8Hf0.2)C tips was demonstrated by taking high-resolution electron micrographs.
We developed a mask split algorithm, ''M-Split,'' using some theories of computational geometry. First, we determined which patterns to split based on actual stencil mask fabrication and defined singular patterns. These singular patterns consisted of nonconvex polygons and could be identified by computational geometry. The contoured singular patterns were then split into two complementary masks, balancing the pattern area density. The split resulted in an 80 nm design-rule logic device, showing that the original patterns could be completely split into polygons that could safely fabricate a stencil mask with a pattern area balance of 50.00% between two complementary masks. The ratio of increase of polygons caused by splitting was 4.84. The computational time without contouring and data output for one 1-mm-square sub field on a 4ϫ mask was 14.2 s for the logic device.
Articles you may be interested inResolution-limiting factors in low-energy electron-beam proximity projection lithography: Mask, projection, and resist process J. Vac. Sci. Technol. B 22, 136 (2004); 10.1116/1.1635850 High-performance proximity effect correction for sub-70 nm design rule system on chip devices in 100 kV electron projection lithography Design and implementation of a real-time hierarchical parallel postprocessor for 100 keV electron beam lithography J.
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