Canon Reveals Details of New IDEAL Exposure Method to Push Conventional Optical Lithography Below 70nm.

SANTA CLARA, Calif.--(BUSINESS WIRE)--March 26, 1999--Canon presented the details of its new IDEAL multilevel optical imaging technology to the technical elite of semiconductor chip makers attending the SPIE Microlithography '99 conference held here last week. IDEAL achieves a process k1 factor of 0.3, enabling optical lithography to resolve circuit patterns smaller than one-half the wavelength of the illumination light.

Papers dealing with optical extension through resolution enhancement dominated this year's conference, reflecting the chip-making industry's growing conviction that patterning with conventional optics will be the most viable lithography method for many years to come.

Today's lithographic processes typically achieve k1 factors of only 0.5 in production environments. But, process k1 factors below 0.4 will be needed for ArF based lithography to reach 100nm, and even the most aggressive processes do not exhibit that level of performance. By reducing the k1 factor to 0.3, Canon's IDEAL method will allow high NA 193nm ArF tools to print circuit features as fine as 80nm, and extend 157nm optical lithography to 60nm or less.

Canon's presentation revealed a simple two-mask exposure method developed by its Nanotechnology Research Center and its Semiconductor Production Equipment Development Center, and showed the results of using the new method on conventional KrF steppers with 0.60 and 0.63 NA to achieve difficult 120nm circuit features corresponding to k1 = 0.3 lithography. Data and SEM pictures showed 120nm dense and isolated lines, 130nm logic gate pattern array, and 130nm contact holes with excellent profile.

IDEAL is an acronym for Innovative Double Exposure by Advanced Lithography. According to Phillip M. Ware, the director and assistant general manager of technical marketing for Canon USA Semiconductor Equipment Division, IDEAL enables projection optics to resolve circuit patterns smaller than one-half the wavelength of the illumination light. "IDEAL pushes traditional optical imaging far into the realm of next generation lithography--something that was considered impossible as recently as a year ago," says Mr. Ware.

"IDEAL works with ordinary optical steppers or scanners. It works with a variety of patterns, and with excellent CD control, depth of focus and process latitude. It applies right now to real-world chip manufacturing," Mr. Ware said.

Canon is working with chip makers and circuit designers to optimize their circuit layouts to take full advantage of its IDEAL method in volume device production. The IDEAL technology can be applied to periodic patterns of memory devices, as well as the isolated features of logic and ASIC circuits.

How IDEAL multi-level imaging works

Canon's IDEAL imaging method works by dividing critical layer fine and coarse circuit pattern components between two reticles. By first using a simple alternating phase-shift mask with fine line and space patterns (k1=0.3), then a simple binary mask for rough outline patterning, IDEAL achieves a multi-level exposure dose at the wafer plane. Highly detailed resist patterns are exposed where the accumulated partial dose from the overlapping aerial images of the PSM and the coarse reticles meets or exceeds the resist threshold level. IDEAL avoids complex OPC and PSM shifter layout issues and the technology is compatible with both positive and negative resists.

Canon emphasized that its IDEAL technology not only relaxes reticle design, but also allows significant alignment latitude between the two exposures. Data and SEM pictures in its presentation demonstrated that misaligning the reticle by as much as +/-20nm produced no significant change in critical dimensions. The effect of misalignment between the two exposures on overlay is not a major concern either, since image placement on the wafer is mainly a function of the fine pattern reticle.

To cover its new IDEAL technology, Canon has applied for 48 patents in Japan and the U.S. It plans to license the technology with the sale of its future steppers and scanners which will be optimized for use with IDEAL technology.

One aspect of Canon tool optimization that is essential for implementing IDEAL is already in place. Namely, extremely low aberration lenses, which are key to achieving k1=0.3 lithography in practice. Since 1997, Canon has reengineered its entire lens design, production and tuning process to dramatically reduce both low and high order aberrations. This initiative includes Zernike coefficient-based lens tuning, and Canon's high precision ULTiMA lens measurement process, which became part of its lens production line in early 1996.

"All of the post-optical, NGL approaches have serious technology hurdles to overcome," Mr. Ware said. He said that Canon has the resources to pursue the NGL approaches that look promising, and is doing that today, but that it is likely to be many years before any post-optical approach becomes production-worthy.

"From our vantage point," Mr. Ware said, "optical lithography using 248nm, 193nm and 157nm excimer lasers with extension techniques such as IDEAL appears to hold the most promise, and provides the most flexible and the lowest cost options for practical everyday manufacturing for the foreseeable future."

About the company

Canon's Semiconductor Production Equipment Group, in Utsunomiya, Japan, is part of the company's Optical Products Operations. There are two semiconductor research bodies within the Semiconductor Production Equipment group--the Development Center, and the Nanotechnology Research Center. The Development Center mainly focuses on current lithography development and manufacturing--e.g., i-line, KrF and ArF steppers and scanners. The Nanotechnology Research Center develops near future and NGL technology.

The Semiconductor Equipment Division of Canon U.S.A., Inc., based in Santa Clara, Calif., supplies step-and-repeat and step-and-scan photolithography tools for manufacturing integrated circuits and large active matrix liquid crystal flat panel displays.

Canon U.S.A., Inc., headquartered in Lake Success, N.Y., is an industry leader in professional and consumer imaging, and is a top patent-holder in imaging technology. It employs 12,000 people at more than 30 facilities throughout North, Central and South America and the Caribbean.

Canon, Inc., comprising all Canon Group operations, is a $24-billion company with 78,000 employees. Its headquarters are in Tokyo, Japan, with approximately 80 sales companies, manufacturing companies and R&D centers, worldwide.