PHASE MASK AND METHOD OF FABRICATION

摘要

A method of fabricating a two-layer phase mask comprises subjecting a photoresist material to two overlapping laser beams that create light and dark fringes in the overlapping beam regions. The photoresist can comprise a liquid crystal and a photo-sensitive material, including, for example, a photo-sensitive monomer and/or polymer. The two laser beams can be first directed towards one side of the photoresist. In the areas subjected to lighter fringes, the polymer molecules can link together and force the liquid crystal into the areas subjected to the darker fringes. This can leave an alternating pattern of linear strips of polymer-rich and liquid crystal-rich regions. The exposure time can be limited so that the strips are formed only partially through the thickness of the photoresist. The photoresist can be then rotated 90 degrees and the overlapping laser beams directed towards the opposite side of the photoresist. Alternating strips of polymer-rich and liquid crystal-rich regions can be formed that extend partially through the photoresist. These strips can be arranged orthogonally to the strips formed on the opposite side of the photoresist. The material in liquid crystal-rich regions can be washed out when the photoresist is developed. A two-layer, integrated phase mask can therefore be produced. Exemplary methods eliminate the need for complicated alignment techniques.