CONTACT LITHOGRAPHY AT 157 nm WITH AN F₂ EXCIMER LASER.

The first use of an F//2 excimer laser and a novel mask technology for high resolution photolithography at 157 nm are reported. With a contact lithography technique resist lines as narrow as 0. 15 mu m have been made. Because of the short wavelength involved, conventional mask technology using quartz substrates could not be employed. Alkaline-earth halide substrates (e. g. , CaF//2) that have high transmittance at 157 nm were used as a base for the mask production. Resolution test masks were prepared using e-beam lithography and reactive ion etching to pattern a polyimide film on the substrates. The development of lithographic techniques at this wavelength is significant since the 157 nm radiation is currently the deepest VUV radiation available with high energy flux from a readily obtained commercial laser.