100 Nanometer Features are Produced Using 248 Nanometer Lithography
Processes
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TOKYO--(BUSINESS WIRE)--April 14, 1998-- Researchers from Photronics, MicroUnity, National Semiconductor and
SEMATECH recently announced results of their collaboration which combined optical proximity correction (OPC) design
features with alternating phase-shift photomasks (PSM) to provide the potential for a manufacturable process window at less
than half the wavelength of light. The work, presented at the Photomask Japan '98 Conference held at Kanagawa Science Park
last week, cites good critical dimension (CD) control of 100 nanometer features on the wafer using 248 nanometer deep
ultra-violet wavelength exposure on 4X lithography systems. Photomask Japan '98 is a major annual symposium on photomask
and x-ray mask technology sponsored by SPIE, BACUS and Photomask Japan.
The collaboration is an integral part of SEMATECH's DELPHI project, which has been designed to determine the practical
limits of optical microlithography.
''We are extremely pleased with results on the printed layers,'' said John S. Petersen, SEMATECH Fellow and DELPHI
Project Leader. ''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.''
The collaboration began about a year ago when SEMATECH contracted MicroUnity to provide photomask design and
process support to help address the proximity effect problems seen with phase-shift reticles. As features approach one another,
their diffraction patterns change causing CD's to vary significantly from the drawn design. The CD variation caused by these
proximity effects can significantly limit the yield for integrated circuits manufactured using the semiconductor industry's most
advanced fabrication processes. The proximity effect problem, and the resulting yield loss, worsen as circuit features shrink
below the wavelength of light used to print them. This problem is made more severe by strengthening the effect of phase-shifting
using highly coherent light to illuminate the PSM.
''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.'' He added, ''The long-standing relationship we have
with Photronics has been critical in our better understanding of the intricacies involved in the manufacture of complex OPC
reticles using our unique software. It was only natural that when we needed to build a reticle of this complexity, we looked to
their advanced process capability and state-of-the-art reticle production technology.''
Doug Van Den Broeke, Photronics' Director of Research and Development stated, ''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 nanometer lithography far beyond the expectations of the 1997 SIA Technology Roadmap.'' He added, ''Our
long working relationship with MicroUnity on OPC development and our internally driven development work on phase-shift
reticles provides an unsurpassed experience base, which enabled us to successfully combine these two complex lithographic
enhancement strategies.''
Photronics was contracted as the reticle supplier because of their proven ability and experience in providing high resolution
advanced OPC and phase-shift photomasks that are required by the DELPHI project team. Together, SEMATECH, National
Semiconductor, Photronics and MicroUnity engineers designed test reticles which contained a myriad of 180 degree
phase-shifted structures that were combined with MicroUnity's sub-resolution scattering bar features and fine selective biasing.
The designs were drawn with a customized version of MicroUnity's MaskRigger(tm) software. Prior to reticle fabrication, two
types of simulations were done. First, the entire imaging process was simulated with PROLITH 3D(tm), a simulation program
provided by FINLE Technologies of Austin, Texas, that incorporates the latest resist models used at SEMATECH. These
simulations fine tuned the placement and size of the OPC structures needed to obtain the desired image. Second, to minimize
diffraction related feature placement problems and to further improve process latitude, TEMPEST, a simulation program from
the University of California at Berkeley that simulates the electromagnetic field at the mask, was used to design the best mask
topography for shaping the projected image. Then, in the case of alternating PSM, topographical design was validated with
non-OPC test masks designed by Benchmark Technologies, Lynnfield, MA and manufactured by Photronics.
Upon completion of the design phase, Photronics fabricated the OPC reticles using their proprietary UltraRes(tm) process and
phase-shift fabrication techniques, which allow the Company to achieve resolution of features on the reticle down to 0.25
micron. SEMATECH then used these highly complex reticles to print wafers using 248nm exposure tool with a numerical
aperture of 0.53, from Integrated Solutions, Incorporated, Austin, TX. 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.
''As a SEMATECH member, National Semiconductor plays a key role as one of the corporate sponsors of SEMATECH's
DELPHI project. Now as a result of this collaboration, we are optimistic that our 248 nanometer deep ultra-violet capital
infrastructure can survive a few more generations.'' said Robert Socha, Senior Engineer assigned to DELPHI.
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Based in Austin, Texas, SEMATECH is a non-profit consortium of U.S. semiconductor manufacturing companies. Its members
are: AMD, Digital, Hewlett-Packard, IBM, Intel, Lucent Technologies, Motorola, National Semiconductor, Rockwell and
Texas Instruments. International SEMATECH is a subsidiary of SEMATECH. In addition to the SEMATECH members, its
participating companies are Hyundai, Philips, SGS-THOMSON [NYSE:STM - news], Siemens and Taiwan Semiconductor
Manufacturing Company. Additional information on SEMATECH and International SEMATECH is available at
www.sematech.org.
Photronics is a leading worldwide manufacturer of photomasks. Photomasks are high precision quartz plates that contain
microscopic images of electronic circuits. A key element in the manufacture of semiconductors, photomasks are used to transfer
circuit patterns onto semiconductor wafers during the fabrication of integrated circuits. They are produced in accordance with
circuit designs provided by customers at strategically located manufacturing facilities in Arizona, California, Connecticut, Texas,
Germany, Korea, Singapore, Switzerland and the United Kingdom. Additional information on the Company can be accessed at
www.photronics.com.
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matters discussed in this news release that may be considered forward-looking statements may be subject to certain risks and
uncertainties that could cause the actual results to differ materially from those projected, including uncertainties in the market,
pricing competition, procurement and manufacturing efficiencies, and other risks detailed from time to time in the Company's
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