Negative pattern fabrication using laser exposure of positive photoresist

Abstract

The method of simultaneous positive and negative pattern formation on a single positive photoresist layer is described. A negative photoresist pattern was fabricated by using local laser exposure to crosslink a positive resist layer, consecutive UV flood exposure, and resist developing. The positive pattern is obtained on the same photoresist layer in the areas masked from the UV flood exposure. Effects of laser energy and resist processing parameters on height and width of negative type resist structures were investigated. Metal line grid structures with lines in the region of 3 to 30 micrometers in width were manufactured on a 5' X 5' glass substrate using this technique. The proposed method of positive/negative pattern formation significantly reduces the number of technological steps in the fabrication of diffractive elements for dual-wavelength applications.