Lithographic evaluation of the hydrogenated amorphous carbon film

Electrical measurement techniques and aerial image simulation were used to quantify the lithographic benefits of an IBM hydrogenated amorphous carbon attenuated phase shifting mask for 0.25 and 0.2 mu m features. Both a chrome and attenuated amorphous carbon blank were patterned with electrically testable structures consisting of varying dimensions and pitch. Detailed characterization was performed on the blanks to confirm phase, transmission, and dimensional accuracy. Process window characterization as a function of image biasing and pitch were evaluated using SPLAT simulations and electrical measurements for SVGL Micrascan II exposures combined with exposure-defocus analysis techniques. The electrical linewidth data showed a 12.5% reduction of depth-of-focus corresponding to a 25 nm offset from optimum bias, demonstrating the importance of accurate mask biasing. Electrical measurements structures were patterned on doped polysilicon films using APEX-E resist. Exposure latitude enhancement was achieved for isolated and nested features producing process window enhancements as large as 50% relative to chrome-based imaging of 0.25 and 0.2 mu m features. Finally, depth-of-focus varied systematically with pitch. (C) 1995 American Vacuum Society.