Instead of conventional lenses, exposure equipment operating in the EUV(Extreme Ultraviolet) wavelength range requires the use of multilayer mirrors, which incorporate alternating layers of film made of different materials. Creating such mirrors demands the most advanced level of ultra-precision processing in the world, requiring accuracy at the atomic level(the radius of a hydrogen atom is approximately 0.1 nm). In addition, because of the aspherical shape of the mirrors, the processing techniques must also be highly sophisticated.

Canon is currently working on IBF(Ion Beam Figuring) technologies to refine the shape of mirrors used in EUV exposure equipment. The IBF technology ensures high-precision figuring over a spatial frequency domain of the shape without degrading surface roughness. Selecting the figuring diameter of the IB gun also makes it possible to correct shapes over a wide spatial frequency domain.

In tests using a Canon-developed IBF system, mirrors with 0.36 nmRMS (Root Mean Square) roughness before correction were successfully corrected to 0.13 nmRMS roughness, achieving the world's highest level of surface accuracy and clearly demonstrating the system's high figuring accuracy. The development of the IBF system was assigned to the EUVA (Extreme Ultraviolet Lithography System Development Association) by NEDO(New Energy and Industrial Technology Development Organization) as part of Japan's Ministry of Economy, Trade and Industry's Program for Fundamental Technologies in Advanced Semiconductor Device Processing as a theme of the Extreme Ultraviolet(EUV) Lithography System Development Project.

Before processing:
0.36 nmRMS roughness(2.510 nmPV)

After processing:
0.13 nmRMS roughness(0.975 nmPV)

Results of Shape-Correction Testing Using a Mirror Material