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VA: Vakuumphysik und Vakuumtechnik

VA 1: Vakuumverfahrenstechnik: EUV-Lithografie

VA 1.2: Hauptvortrag

Montag, 26. März 2001, 10:10–10:50, R221

Optical Lithography at 157 nm and the impact on the performance of photoresists — •Wolfgang Radlik — Infineon, Erlangen

For almost 25 years optical lithography is predicted to come to an end within the particular decade following. As the limiting factor mainly the optical resolution has to be taken into account. Neverteheless, optical lithography is still capable to follow the more and more accelerating shrink of the IC’s critical dimensions and will face the 70nm node at 157 nm exposure wavelength in about four years. Lithography at 157nm wavelength is not only a challenge for the optical exposure system, but also addresses many requirements in terms of resolution, transparency and stability against photo decompostion to the resist system. Several of these issues are depending on each other such as the transparency of the resist layer for 157nm and it’s minimum film thickness according to the etch conditions for the subsequent patterning process. Seperating the requirements for optical performance and etch selectivity by a bilayer resist approach represents very promising conception to solve this interdependencies. Given by the numerical aperture of the exposure tool and the wavelength, the minimum feature size being printable in the photo resist at 157 nm is limited at approximately 100nm and above. To meet the targets beyond, various enhancement techniques such as phase shifting masks have been introduced to overcome the optical limitations. Further potential is opend up by photoresists holding chemical amplification mechanisms. Chemical amplification does mean to achieve an additional shrink of the features after exposure, based on the well controlled growth of organic material on the surface of the underlying photopatterned resist.