A photolithographic method uses different exposure patterns. In one
aspect, a photo-sensitive layer on a substrate is subject to a first
exposure using optics having a first exposure pattern, such as an
x-dipole pattern, followed by exposure using optics having a second
exposure pattern, such as a y-dipole pattern, via the same mask, and with
the photo-sensitive layer fixed relative to the mask. A 2-D post pattern
with a pitch of approximately 70-150 nm may be formed in a layer beneath
the photo-sensitive layer using 157-193 nm UV light, and hyper-numerical
aperture optics, in one approach. In another aspect, hard baking is
performed after both of the first and second exposures to erase a memory
effect of photoresist after the first exposure. In another aspect,
etching of a hard mask beneath the photo-sensitive layer is performed
after both of the first and second exposures.