The present invention describes an aperture including: an opaque plate; two sliver openings located in the opaque plate, the two sliver openings having rectangular shapes, the two sliver openings being parallel to each other.The present invention further describes a method including: decomposing a pattern into horizontal sub-features and vertical sub-features; forming a first mask corresponding to the horizontal sub-features; forming a second mask corresponding to the vertical sub-features; forming a first aperture with two parallel horizontal sliver openings corresponding to the first mask; forming a second aperture with two parallel vertical sliver openings corresponding to the second mask; exposing a wafer using the first aperture and the first mask; exposing the wafer using the second aperture and the second mask; and exposing the wafer with the third mask.