With more than 150 years of success in developing and refining materials to enable the growth of advanced technologies, Corning Inc. is being recognized as a key contributor to the advancement of microlithography. As the semiconductor industry continues its drive to supply smaller and faster integrated circuits, microlithography is widely recognized as one of the key pacing technologies to accomplish this goal.
Corning is the largest supplier of advanced fused silica material worldwide for the krypton fluoride (KrF) and argon fluoride (ArF) lithography nodes. With its HPFS fused silica brand, Corning supplies all major stepper manufacturers with optical blanks for stepper optics. Corning invested millions to be a leading supplier of calcium fluoride materials for the 193nm and 157nm nodes, both for stepper and laser optics. In addition, Corning's ULE zero expansion glass has been identified as the "material of choice" by the Extreme Ultra Violet (EUV) LLC for use in mask blanks and reflective optics.
While Corning's HPFS fused silica - one of the world's highest purity glass - has been a standard component in microlithography steppers for years, Corning scientists are still making improvements to the material that permit technology jumps. The company recently installed new furnaces in its Charleston, SC, manufacturing facility for the production of ultra high transmission ArF grade HPFS. Building off of already stellar optical properties, transmitting a higher percentage of deep ultraviolet light through the material enables the printing of narrower line widths on semiconductor chips.
"Circuit manufacturers who employ ArF HPFS fused silica will be able to increase computer speed and the amount of memory that can be placed on a single chip," said Mike Heslin, manager, semiconductor materials development. "While advanced research in HPFS continues to enable faster and faster silicon-based devices, this material in no way marks the end of the game. Other Corning technologies will push the envelope considerably further."
Calcium fluoride (CaF2) represents the next-generation optical material for semiconductor applications. This crystalline material has outstanding properties including high internal transmission levels along with an outstanding long-term laser durability at the fluences used in stepper lasers. Unlike HPFS, which is created through a Corning-developed vapor deposition process, calcium fluoride is grown over a matter of weeks in specialized furnaces.
"While the industry is now focused on perfecting the 193nm calcium fluoride process, it is also the material of choice for the leap to 157nm steppers," noted Paul Schermerhorn, technology development manager for fluoride crystals at Corning.
In order to complete correlation and qualification of the CaF2, the company's scientists and engineers continue to develop advances in metrology. For instance, x-ray diffraction analysis is used to determine critical crystal orientation measurements, significant investment in laser durability capability continues, and birefringence capabilities for greater than 300mm diameter lens blanks are now possible.
Corning also works closely with customers in the semiconductor industry in order to continue to advance its metrology capabilities.
Looking more than five years into the future, Corning scientists are developing a process to use the company's ULE zero expansion glass for microlithography applications. Unlike HPFS and calcium fluoride that guide the pathways of deep ultraviolet (DUV) light via refraction, ULE directs even shorter extreme ultraviolet (EUV) wavelengths to their target via reflection.
"ULE-based stepper cameras will be unlike any the semiconductor industry has seen before. When ULE is exposed to EUV, the resulting heat from the laser will have little or no effect on the glass. This is essential for holding the figure of microlithography tools, paving the way for narrower line widths on the chips," stated Heslin.
ULE also illustrates Corning's capacity for innovative applications of existing technologies. Exclusive to Corning, ULE zero expansion glass was originally developed for the space industry to maintain the critical performance of optical systems at the extreme temperatures. Many of the world's major observatories have ULE primary mirrors, and ULE lightweight mirror blanks are used in ground-based telescopic systems requiring high mobility.
Through the combined expertise of its Corning Semiconductor Materials and Corning Tropel business units, Corning is a leading supplier of optical materials, precision optics, and metrology instruments for the semiconductor industry.
With sales offices around the world, Corning manufactures fused silica glass in Canton, N.Y., and Charleston, S.C., and optical grade fluoride crystals in North Brookfield, Mass. The ultra-pure materials provide extreme optical clarity and durability, and are used in the manufacture of today's most advanced integrated circuits. Corning Tropel manufactures optical subsystems and advanced form metrology instrumentation in Rochester, N.Y. More information is available at www.hpfs.corning.com or www.tropel.com.
Established in 1851, Corning Inc. (www.corning.com) creates leading-edge technologies for the fastest-growing markets of the world's economy. Corning manufactures optical fiber, cable and photonic products for the telecommunications industry; and high-performance displays and components for television, information technology and other communications-related industries. The company also uses advanced materials to manufacture products for scientific, semiconductor, and environmental markets. Corning revenues for 2000 were $7.1 billion.