SELF-ALIGNED PHASE-SHIFTING MASK

摘要

SELF-ALIGNED PHASE-SHIFTING MASK A phase-shifting mask with self-aligned spacers of phase-shift material adjacent to the edges of the opaque mask pattern and a method for making the same is disclosed. The method of the invention deposits a blanket layer of an appropriate phase-shift material over a transparent mask substrate having a patterned opaque layer followed by a removal step which forms the spacers. The mask is preferably comprised of a quartz substrate covered with a patterned chrome layer fabricated following the normal inspection and repair procedure. A layer of phase-shift material is then blanket deposited. The thickness and index of refraction of the phase-shift material is chosen to provide a phase-shift of 0.67 pi radians (120 degrees) to pi radians (180 degrees) in the completed mask which is the range of phase-shift demonstrated to be effective. The phase-shift layer is then blanket etched anisotropically in a Reactive Ion Etch (RIE) chamber, using the chrome and quartz as etch stops. Following the etch, the remaining phase-shift material forms a roughly quarter-cylinder cross-section shaped spacer pattern. The spacer pattern is self-aligned to the edges of the opaque mask pattern.