Method for forming pattern
In an exposure step, a combination of a first photomask and a second mask is used. The first mask has a real pattern corresponding to the pattern actually formed on the film to be processed, and a dummy pattern added for controlling pattern pitch in the first photomask within a prescribed range; and the second photomask has a pattern isolating a real-pattern-formed region from a dummy-pattern-formed region. In forming the pattern, after forming a film to be processed on a substrate, a first mask is formed on the film to be processed, by lithography, using the first photomask, and a second mask is formed on the film to be processed, by lithography, using the second photomask. Thereafter, the film to be processed is etched off and removed using the first and second masks as masks to form the pattern.
1. A method for forming patterns comprising:
forming, on a substrate, a film to be processed;
forming a first mask, which is a hard mask, on said film to be processed, by lithography, using a first photomask, wherein forming said first mask includes
forming a first material film that becomes the material film of said first mask on said film to be processed,
forming a first anti-reflective film on said first material film,
forming a first resist pattern by transferring the pattern of said first photomask onto said first anti-reflective film, using photolithography, said first photomask having a real pattern, which is an actual pattern on said film to be processed, and a dummy pattern added to control pattern pitch in said first photomask to within a prescribed range for resolution enhancement of the real pattern of said first photomask, and
etching said first material film and said first anti-reflective film using said first resist pattern as an etching mask;
forming a second mask, which is a hard mask, on said film to be processed and on said first mask, by lithography, using a second photomask, wherein forming said second mask includes
forming a second material mask that becomes the material film of said second mask on said film to be processed and on said first mask,
forming a second anti-reflective film on said second material film,
forming a second resist pattern by transferring the pattern of said second photomask onto said second anti-reflective film, using photolithography, said second photomask having a pattern isolating a region in which said dummy pattern is formed from a region in which said real pattern is formed, and
etching said second material film and said second anti-reflective film using said second resist pattern as an etching mask; and
etching said film to be processed using said first mask and said second mask as masks.
2. The method for forming patterns according to claim 1 , wherein said first mask is a silicon nitride film and said second mask is a silicon oxide film.
3. The method for forming patterns according to claim 1 , including using a quadrapole illumination source for exposure in the lithography used in forming said first mask.
4. The method for forming patterns according to claim 1 , including using a dipole illumination source for exposure in the lithography used in forming said first mask.
5. The method for forming patterns according to claim 1 , including using a circular illumination source for exposure in the lithography used in forming said first mask.
6. The method for forming patterns according to claim 1 , wherein said first photomask is an attenuated phase shifting mask.
7. The method for forming patterns according to claim 1 , wherein said first photomask is an alternating phase shifting mask.