Proposal for a 50 nm proximity x-ray lithography system and extension to 35 nm by resist material selection

In this article, a 50 nm generation proximity x-ray lithography (PXRL) system is proposed using shorter wavelengths of exposure light down to around 3 Angstrom. The illumination system uses a mirror at 1 degrees incidence angle such as in the Canon stepper XRA-1000, which can be realized by coating with a fourth or fifth period metal such as Co or Ph. The resist containing chemical elements such as Cl, S, P, Si, and Br whose x-ray absorption edge lies in the wavelength band of the exposure light can yield a strong absorption using this system. Therefore, a resist material containing such elements is highly sensitive when applied to the 50 nm system. The average wavelength of power absorbed by the resist depends on the elements contained in the resist. This suggests that the resolution limits also depend on the resist material even for the same exposure system. Therefore, this system should be extendible down to the 35 nm generation by using such a resist and a thick diamond mask membrane. The system described assumes that the mask-wafer Sap is the currently available 10 mum. In the future, an additional gain in resolution can be expected from a narrower gap. With these improvements, it is foreseeable that PXRL technology can be applied to the 20 nm regime, down to the operational limits of silicon devices at room temperature. (C) 2000 American Vacuum Society. [S0734-211X(00)17406-2].