Diffractive grey-tone phase masks for laser ablation lithography

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