Pattern forming method and mask
View Patent ↗Hole patterns are repeatedly arranged on a mask at a constant pitch in each of predetermined directions. In the predetermined directions, a first direction with the smallest pitch and a second direction with the second smaller pitch are specified. A Levenson phase shifter is formed corresponding to the hole patterns to cause the phases of transmitted light through the hole patterns adjacent to each other in the first direction to be opposite to each other. An exposure process is performed by two-point illumination which is adapted to improve the resolution property in the second direction.
1. A method, comprising:
providing a mask over a semiconductor wafer, the mask comprising a plurality of rectangular patterns spaced apart from one another in a two dimensional plane;
wherein a first group of said rectangular patterns are phase shift patterns and a second group of said rectangular patterns are zero phase degree shift patterns, wherein said rectangular patterns that are adjacent to one another in one of an X-axis direction, a Y-axis direction and a slant direction relative to the two dimensional plane belong to a same one of said first and second groups, and wherein said rectangular patterns that are adjacent to one another along the other two of said X-axis, Y-axis and slant directions alternate between said first and second groups; and
performing a two-point illumination with an oblique illumination on the mask in said direction along which said rectangular patterns belong to a same one of said first and second groups.
2. The method as claimed in claim 1 , wherein said direction along which said rectangular patterns belong to a same one of said first and second groups is the slant direction.
3. The method as claimed in claim 1 , wherein said direction along which said rectangular patterns belong to a same one of said first and second groups is the X-axis direction.
4. The method as claimed in claim 1 , wherein said direction along which said rectangular patterns belong to a same one of said first and second groups is the Y-axis direction.
5. The method as claimed in claim 1 , wherein the phase shift patterns are formed by partially using a transparent film in light-transmissive regions of the mask.
6. The method as claimed in claim 1 , wherein the phase shift patterns are formed by etching a mask substrate in light-transmissive regions of the mask to a predetermined depth.
7. The method as claimed in claim 1 , wherein the phase shift patterns are formed by using a semitransparent film around light-transmissive regions of the mask.