Heavy ion (Xe and I) irradiation effects on photoresist films

This contribution presents a study of heavy ion irradiation induced chemical, structural and tribological modifications in photoresist films. Novolak-diazoquinone films 400 and 800 nm thick have been irradiated with 800 keV Xe++ and 4 MeV I++ ions respectively in a fluence range of 10(13) to 6 x 10(15) ions cm(-2). At these energies, both ions have the same nuclear S. plus electronic S, stopping power, congruent to200 eV Angstrom(-1), but the ratio S-e/S-n is congruent to1/3 for Xe++ and congruent to3 for I++. A detailed investigation of the chemical composition and structural modification of the films due to the irradiation was performed using the ERDA, Raman and nanoindentation techniques. The measured hardness H = 13 GPa and Young's modulus E = 140 GPa for both films and the respective Raman spectra show that, at the largest fluences, both films are transformed into amorphous carbon layers. However, in the region of intermediate fluences the effects of irradiation on H and E are governed by a competition between the nuclear and the electronic stopping powers. The present data are compared with our previous measurements of the same film irradiated with He+ ions, when the nature of the transferred energy density is mainly of electronic origin. (C) 2002 Elsevier Science B.V. All rights reserved.