Double-sided structured mask for sub-micron resolution proximity i-line mask-aligner lithography

Diffractive mask-aligner lithography allows printing structures that have a sub-micrometer resolution by using non-contact mode. For such a purpose, masks are often designed to operate with monochromatic linearly polarized light, which is obtained by placing a spectral filter and a polarizer in the beam path. We propose here a mask design that includes a wire-grid polarizer (WGP) on the top side of a photo-mask and a diffractive element on the bottom one to print a 350 nm period grating by using a classical mask-aligner in proximity exposure mode. Linearly polarizing locally an unpolarized incident beam is only possible by using a WGP on the top side of the mask. This configuration opens the possibility to use different linear polarization orientation on a single mask and allows to print high resolution structures with different orientation within one exposure.