8 December 1995 Further work in optimizing PBS: is it capable of meeting specifications for 256 Mbit DRAM reticle manufacturing?
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This paper examines the steps needed to improve CD uniformity to meet desired goals for 250 nm optical lithography. The exploratory study of a number of different approaches included development work on both APT 9155 and Hammatech developer tools, an assessment of different developers and rinses, an examination of solvent delivery systems, and materials evaluations such as resist annealing and determination of resist thickness variations at plate edges. The goal for this project is to reach a 25 nm 3 sigma uniformity. Much of the work focused on CD uniformity in a 132 mm field. Improvements to the PBS process were made with a gravity-flow solvent-delivery system, the use of less aggressive (slower) developers, and the use of single or multiple puddles with the Hammatech tool. Improvements were also observed with higher dose, thinner resist films, and smaller spot sizes. With the initial Hammatech process, uniformity was improved with PBS at 2.0 (mu) C/cm2. The results are plotted. Progress over the initial results is predicted with improvements in materials, optimization of the Hammatech puddle process, and automated gravity-flow solvent delivery. Better performance is also expected with higher doses, smaller spot sizes at the equivalent address, optimum solvents, and thinner resist. These results show that there are still improvements to be made to PBS, which make it a potential candidate for 250 nm reticle manufacturing.
© (1995) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Robert L. Dean, Robert L. Dean, Charles A. Sauer, Charles A. Sauer, } "Further work in optimizing PBS: is it capable of meeting specifications for 256 Mbit DRAM reticle manufacturing?", Proc. SPIE 2621, 15th Annual BACUS Symposium on Photomask Technology and Management, (8 December 1995); doi: 10.1117/12.228192; https://doi.org/10.1117/12.228192


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