Patent ID: 8465906
Filing Date: 2013-06-18
Classification: G03F

Abstract:
1. A photolithography method, comprising: providing a substantially opaque mask having N stepped rows of offset, substantially transparent, rectangular mask features, where N is an integer and N≧2; and illuminating a photoresist layer located over an underlying material layer with dipole illumination through the substantially transparent, rectangular mask features of the substantially opaque mask to form 2N rows of exposed regions in the photoresist layer; wherein the exposed regions have a substantially elliptical or a substantially circular shape when viewed from above the photoresist layer; wherein: adjacent rectangular mask features in each row of the offset, substantially transparent, rectangular mask features are separated by a gap and the rectangular mask features are offset from each other such that individual mask features have one-side dense portions and two-side dense portions; each of the rectangular individual mask features has a characteristic length which corresponds to a shorter side length for each of the individual mask features; for the one-side dense portions, a nearest adjacent mask feature is more than 3 characteristic lengths distant; for the two-side dense portions, a nearest adjacent mask feature is less than 3 characteristic lengths distant; the individual rectangular mask features comprise longer sides oriented in a first direction and shorter sides oriented in a second direction perpendicular to the first direction; the gap is measured between the longer sides of adjacent mask features; the offset is measured as an orthogonal displacement of shorter sides of adjacent mask features in the first direction; each gap and each offset are substantially the same in between adjacent mask features in the N stepped rows of offset rectangular mask features; the one-side dense portions are located at two opposing shorter sides of each mask feature, which is offset with respect to an adjacent mask feature; the two-side dense portions are located in between the two one-side dense portions; a distance measured orthogonally from a first mask feature centerline oriented in the first direction to an adjacent second mask feature centerline oriented in the first direction defines a pitch, and the pitch is between 60 and 80 nm; an angle, in between a first point located at an intersection of the first mask feature centerline and a first shorter side of a first mask feature with a corresponding second point located at an intersection of the second mask feature centerline and a corresponding first shorter side of a second mask feature, ranges from 55 to 70 degrees; and a pitch, in between the exposed regions in the photoresist layer in each of the 2N rows, ranges from 70 to 85 nm.