Diffractive grey-tone phase masks for laser ablation lithography

We investigated a fast parallel method for the fabrication of continuous pr ofile structures in polymer surfaces using a XeCl excimer laser at a wavele ngth of 308 nm. The used quartz grey tone phase masks consist of diffractiv e gratings which diffract a fraction of the impinging light out of the aper ture of the projection lens. The masks were generated by electron beam lith ography and reactive ion etching on standard mask blanks. A variation of th e duty cycle of the gratings enables us to control the transmitted zero ord er flux for different positions on the mask. Using this method, diffractive optical elements were ablated in polyimide films. For good optical perform ance, it was necessary to pre-compensate the response of the polymer film w ith regard to threshold and non-linearity. The structure profiles and diffr action efficiency of blazed gratings were measured and correlated with the correction parameters. (C) 2001 Elsevier Science BY All rights reserved.