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To: slipnsip who wrote (16559)	4/15/1998 9:39:00 AM
From: Andrew Brockway	Read Replies (1) \| Respond to of 25960

Sematech reticle project achieves 0.1-micron results with DUV stepper TOKYO--During a recent photomask conference here, a team of researchers from Photronics, MicroUnity, National Semiconductor and U.S.-based consortium Sematech have reported good critical dimension (CD) control of 100-nanometer features using 248-nm deep ultraviolet (DUV) exposure with a 4X lithography system. The disclosure came at Photomask Japan '98 at the Kanagawa Science Park here, where researchers reported on their collaboration to combine optical proximity correction (OPC) design features with alternating phase-shift photomasks (PSM) in an attempt to develop wafer exposures that work at less than half the wavelength of light. "We are extremely pleased with results on the printed layers," said John S. Petersen, Sematech fellow and the leader of the Delphi project, which aims to determine the practical limits of optical microlithography. "The data clearly indicates that OPC combined with alternating phase-shift can overcome proximity related CD error, while taking full advantage of the resolution improvement of the PSM technique that was first developed, independently, in the early 1980's by Marc D. Levenson and Masato Shibuya. "Ultimately, demonstrating the feasibility of OPC to correct for these effects may be considered one of the milestones on the road to implementation of alternating PSM into sub-wavelength production," he added. The collaboration began a year ago when Austin, Tex.-based Sematech contracted MicroUnity Systems Engineering Inc. of Sunnyvale, Calif., to provide photomask design and process support that addresses the proximity effect problems seen with phase-shift reticles. Production yields can be lowered in chip processing when CD variation is caused by conflicts in proximity effects. Proximity effect problems grow as device features shrink below the wavelength of light used to print them. "This work presents the first clear picture of how to solve the proximity problems encountered with deep sub-wavelength phase-shift processing," said Roger Caldwell, vice president of silicon technology at MicroUnity. "Our strategy in working together with Sematech's DELPHI project is to participate in the fundamental engineering work that will define the requirements for photomask manufacturing. Those requirements will then be implemented into our highly automated software suitable for production of full sized microprocessor and ASIC circuits." MicroUnity has worked closely with mask maker Photronics Inc. of Brookfield, Conn., to better understand the intricacies involved in the manufacture of complex OPC reticles using its software. "The success of this work confirms Photronics' early commitment to high resolution electron beam processing and will enable the production of reticles capable of extending 248-nm lithography far beyond the expectations of the 1997 SIA Technology Roadmap," said Doug Van Den Broeke, director of R&D at Photronics. Upon completion of the design phase in the project, Photronics fabricated the OPC reticles using its UltraRes process and phase-shift fabrication techniques, which result in resolution of features on the reticle down to 0.25 micron. Sematech then used these reticles to print wafers using 248-nm exposure tool with a numerical aperture of 0.53, from Integrated Solutions Inc. in Austin, Tex. Cross-section scanning electron microscopy (SEM) provided by Charles Evans & Associates was used to make thousands of measurements of the tiny resist features. The measurements were then compiled and analyzed by MicroUnity and Sematech to determine optimal process conditions.