Rigaku Innovative Technologies introduces commercial reflective optical coatings for extreme-ultraviolet lithography

Nov. 30, 2016
Reflective optics are critical for high-speed printing of chip patterns onto wafers using EUV light.
(image: RIT) Rigaku Innovative Technologies (RIT; Auburn Hills, MI), a producer of high-end multilayer optics, has unveiled a range of precision extreme-ultraviolet lithography (EUVL) optical coatings for manufacturing reflective optics for semiconductor-industry wafer-pattern printing. These optics are the critical parts of the optical chain used inside the large photolithographic EUV scanner tools that are being developed to print chip patterns onto wafers at rates up to 125 wafers per hour. EUV light for photolithography is generated by turning a stream of droplets of tin into plasma one at a time with a CO2 laser; required average power levels of EUV radiation will be on the order of 100 W, with the peak pulse power levels much higher.Coatings must be near-perfect Because the EUV wavelength used for this type of photolithography is only 13.5 nm, transmissive optics cannot be used in these systems. And the multilayer coatings for the reflective optics have layers 30 to 50 times thinner than those designed for use at visible wavelengths. These coatings have to be 1) incredibly precise in their thickness, and 2) almost flawless, as any defect will quickly cause the destruction of the optics. RIT calls itself the only independent volume manufacturer of "world-class refelective optics" in the industry. It is one of the earliest companies to invest in research and development of multilayer coating designed specifically for EUVL devices, according to RIT. Building on its existing in-line deposition system for multilayer coatings, RIT recently developed and installed a second in-line high-throughput system. The new deposition system is made of two independent inline systems that can simultaneously deposit coatings onto 4 large optics up to 800 millimeters in diameter. It can also be used to achieve high-precision coatings on substrates up to 1.5 meters long for synchrotron and other applications with a 2-dimensional "d-spacing" distribution pattern. The new system also has a very low defect rate, says RIT. Rigaku has also developed a process to refurbish optics with x-ray/EUV multilayer coatings to near original performance levels. The refurbishment process increases optic life and offsets the effects of contamination and radiation damage, is critical for reducing production costs, according to RIT. For more information about this process and the products, see www.rigakuoptics.com. Source: Rigaku Innovative Technologies

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