Patent ID: 8749760

Claim:
An optical lithography apparatus, comprising: an asymmetrical complementary dipole element comprising: an opaque substrate having first, second, third and fourth regions through which a selected wavelength of light can pass, said first, second, third and fourth region comprising the only openings in said opaque substrate; said first and second regions being equidistant and mirror images about a first axis, said first and second regions having essentially a same first area and a same first optical density relative to said selected wavelength of light; said third and fourth regions being equidistant and mirror images about a second axis, said third and fourth regions having essentially a same second area and a same second optical density relative to said selected wavelength of light, said first area greater than said second area; wherein said first axis is perpendicular to said second axis; said first optical density of said first and second regions is different from said second optical of said third and fourth regions; and wherein said asymmetrical complementary dipole element comprises an opaque layer on a top surface of a transparent substrate, said first and second regions comprise respective openings in said opaque layer that extend from a top surface of said opaque layer completely through said opaque layer, and said third and fourth regions comprise respective openings in said opaque layer that extend from a top surface of said opaque layer part way through said opaque layer.