Patent ID: 7432025
Filing Date: 2008-10-07
Classification: G03F

Abstract:
1. A method of forming a reticle, comprising: providing a reticle substrate having a quartz base, a phase-shifting material over the base, and a chromium-containing material over the phase-shifting material; the substrate comprising a main-field area and a boundary area laterally surrounding the main-field area; the chromium-containing material within the main-field and boundary areas being first and second portions of the chromium-containing material, respectively; providing a first photoresist mask which covers at least the majority of the second portion of the chromium-containing material and leaves at least some of the first portion exposed, the first photoresist mask having a first thickness; thinning the exposed chromium-containing material while protecting the remainder of the chromium-containing material with the first photoresist mask; after the thinning, at least some of the chromium-containing material within the boundary area being thicker than at least some of the chromium-containing material within the main-field area; removing the first photoresist mask, and thereafter forming a second photoresist mask which is patterned over the thinned chromium-containing material across the main-field area, the second photoresist mask having a second thickness which is less than the first thickness; and transferring the pattern from the second photoresist mask into the main-field area to pattern the phase-shifting material.