Patent ID: 7556897

Claim:
A method of forming a reticle, comprising: providing a reticle substrate having a base, and having a chromium-containing material over the base; 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; forming a first photoresist mask which covers at least some of the second portion of the chromium-containing material and leaves at least some of the first portion of the chromium-containing material 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 after removing the first photoresist mask, 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.