Patent ID: 8389183

Claim:
A photomask comprising: a transparent substrate including: a first portion; a second portion atop the first portion, the second portion comprising a first pedestal and including an undercut adjacent the first portion; a third portion atop the first portion, the third portion comprising a second pedestal; and a fourth portion adjacent the third portion and atop the first portion; a first sidewall spacer along the second portion of the transparent substrate; and a second sidewall spacer along the third portion of the transparent substrate, wherein the first, second, third, and fourth portions of the transparent substrate are disposed to provide a plurality of transmission paths through the photomask, the plurality of transmission paths including: a first transmission path through the first portion and producing a first phase shift; a second transmission path through the second portion and the first portion, producing a second phase shift different from the first phase shift; a third transmission path through the second portion, an atmosphere within the undercut, and the first portion, producing a third phase shift intermediate the first phase shift and the second phase shift; a fourth transmission path through the first sidewall spacer, an atmosphere beneath the first sidewall spacer, and the first portion of the transparent substrate, producing a fourth phase shift intermediate the first phase shift and the third phase shift; a fifth transmission path through the third portion and the first portion, producing a fifth phase shift substantially equal to the second phase shift; a sixth transmission path through the fourth portion of the transparent substrate and the first portion of the transparent substrate, producing a sixth phase shift intermediate the first phase shift and the fifth phase shift; and a seventh transmission path through the second sidewall spacer, the fourth portion of the transparent substrate, and the first portion of the transparent substrate, producing a seventh phase shift intermediate the fifth phase shift and the sixth phase shift.