Use of dual patterning masks for printing holes of small dimensions

Abstract

The present invention addresses a problem associated with exposing a photoresist layer of non-uniform thickness. Oftentimes, trench patterns etched into a layer of a semiconductor structure will have trenches of varying sizes. Larger trenches in the structure become filled with photoresist material, while smaller trenches do not leading to non-uniformity of photoresist layer thickness with respect to the large and small trenches. The present invention addresses this non-uniformity in photoresist layer thickness by employing at least two exposure steps when exposing the photoresist layer. A first exposure step exposes portions of the photoresist layer corresponding to the large trenches using a first reticle and first energy level. Next, a second exposure step exposes portions of the photoresist layer corresponding to the small trenches using a second reticle and second energy level. The first and second energy levels corresponding to proper exposure of the respective photoresist layer portions of different thicknesses.

Dependencies are inferred from the claim text.