Method of making a hard disk drive write pole using a tri-tone attenuated phase shift mask
A write pole of a write head of a hard disk drive can be manufactured by forming a photoresist layer over a magnetic material layer located over a substrate, disposing a tri-tone lithographic mask over the photoresist layer, lithographically exposing the photoresist layer through the lithographic mask, developing the photoresist layer to form a patterned photoresist layer, and patterning the magnetic material layer into the write pole by removing portions of the magnetic material layer that are not covered by the photoresist layer. The tri-tone lithographic mask includes a patterned opaque material layer and a patterned partially-transparent material layer located over a transparent substrate. The patterned opaque material layer includes a uniform width region and a flare region. The patterned partially-transparent material layer includes a pair of partially-transparent strips extending adjacent to a respective edge of the patterned opaque material layer, and partially-transparent assist bars.
1. A method of manufacturing a write pole of a write head of a hard disk drive, comprising:
forming a photoresist layer over a magnetic material layer located over a substrate;
disposing a lithographic mask comprising a tri-tone mask including a patterned opaque material layer and a patterned partially-transparent material layer located over a transparent substrate, wherein the patterned opaque material layer comprises a uniform width region extending along a lengthwise direction and having a first uniform width, and a flare region adjoined to a first end of the uniform width region and having a variable lateral dimension along a direction that is perpendicular to the lengthwise direction of the uniform width region, wherein the patterned partially-transparent material layer comprises a pair of partially-transparent strips extending adjacent to a respective edge of the patterned opaque material layer, and partially-transparent assist bars that are laterally spaced from the pair of partially-transparent strips;
lithographically exposing the photoresist layer through the lithographic mask;
developing the photoresist layer to form a patterned photoresist layer; and
patterning the magnetic material layer into the write pole by removing portions of the magnetic material layer that are not covered by the patterned photoresist layer.
2. The method of claim 1 , wherein each of the partially-transparent assist bars comprises a respective parallel segment that is parallel to the lengthwise direction of the uniform width region and a respective slanted segment that is parallel to a respective edge of the flare region.
3. The method of claim 2 , wherein each of the slanted segments of the partially-transparent assist bars laterally extends along a respective direction that is at a fixed or variable angle with respective to the lengthwise direction of the uniform width region of the patterned opaque material layer, the fixed or variable angle being in a range from 20 degrees to 60 degrees.
4. The method of claim 3 , wherein the fixed or variable angle is the variable angle that decreases with a distance from a second end of the uniform width region that is distal from the flare region along a direction that is parallel to the lengthwise direction of the uniform width region.
5. The method of claim 1 , wherein the write pole has a pattern that replicates a pattern of a combination of the patterned opaque material layer and the pair of partially-transparent strips and does not include any pattern that replicates a pattern of the partially-transparent assist bars.
6. The method of claim 1 , wherein the partially-transparent assist bars comprise:
a set of two or more first partially-transparent assist bars located on a first side of the patterned opaque material layer; and
a set of two or more second partially-transparent assist bars located on a second side of the patterned opaque material layer and laterally spaced from the first set of two or more first partially-transparent assist bars by the patterned opaque material layer.
7. The method of claim 6 , wherein a pattern of the set of two or more first partially-transparent assist bars and a pattern of the set of two or more second partially-transparent assist bars have a mirror symmetry with respect to a vertical plane passing through a geometrical center of the patterned opaque material layer along a lengthwise direction of the uniform width region.
8. The method of claim 6 , wherein each of the partially-transparent assist bars has a respective uniform bar width that is in a range from 75% to 125% of a width of each partially-transparent strip within the pair of partially-transparent strips.
9. The method of claim 8 , wherein a lateral spacing between a neighboring pair of first partially-transparent assist bars within the set of two or more first partially-transparent assist bars is in a range from 150% to 500% of the uniform bar width of each of the partially-transparent assist bars.
10. The method of claim 9 , wherein:
the set of two or more first partially-transparent assist bars comprises a first inner partially-transparent assist bar that is most proximal to an adjacent one of the partially-transparent assist strips; and
the first inner partially-transparent assist bar is laterally spaced from the adjacent one of the partially-transparent assist strips by a uniform lateral spacing that is in a range from 150% to 500% of the uniform bar width of each of the partially-transparent assist bars.
11. The method of claim 1 , wherein:
the write pole comprises a uniform-width write pole portion having a uniform pole width; and
the uniform pole width is greater than a first uniform width.
12. The method of claim 11 , wherein the uniform pole width is in a range from a sum of the first uniform width and a second uniform width of one of the pair of partially-transparent strips to a sum of the first uniform width of the patterned opaque material layer and three times the second uniform width.
13. The method of claim 1 , wherein:
the patterned opaque material layer blocks at least 99.8% of incident illumination radiation during the step of lithographically exposing the photoresist layer; and
the patterned partially-transparent material layer blocks from 90% to 98% of the incident illumination radiation.
14. The method of claim 1 , wherein the patterned opaque material layer comprises chromium, and the patterned partially-transparent material layer comprises molybdenum silicide.
15. The method of claim 1 , wherein the step of lithographically exposing the photoresist layer comprises exposing the photoresist layer to a quadrupole shaped annular ultraviolet radiation beam.
16. A tri-tone lithographic mask comprising a patterned opaque material layer and a patterned partially-transparent material layer located over a transparent substrate, wherein:
the patterned opaque material layer comprises a uniform width region extending along a lengthwise direction and having a first uniform width and a flare region adjoined to a first end of the uniform width region and having a variable lateral dimension along a direction that is perpendicular to the lengthwise direction of the uniform width region;
the patterned partially-transparent material layer comprises a pair of partially-transparent strips extending adjacent to a respective edge of the patterned opaque material layer, and partially-transparent assist bars that are laterally spaced from the pair of partially-transparent strips; and
each of the partially-transparent assist bars comprises a respective parallel segment that is parallel to the lengthwise direction of the uniform width region and a respective slanted segment that is parallel to a respective edge of the flare region.
17. The tri-tone lithographic mask of claim 16 , wherein each of the slanted segments of the partially-transparent assist bars laterally extends along a respective direction that is at a fixed or variable angle with respective to the lengthwise direction of the uniform width region of the patterned opaque material layer, the fixed or variable angle being in a range from 20 degrees to 60 degrees.
18. The tri-tone lithographic mask of claim 17 , wherein the fixed or variable angle is the variable angle that decreases with a distance from a second end of the uniform width region that is distal from the flare region along a direction that is parallel to a lengthwise direction of the uniform width region.
19. The tri-tone lithographic mask of claim 16 , wherein the partially-transparent assist bars comprise:
a set of two or more first partially-transparent assist bars located on a first side of the patterned opaque material layer; and
a set of two or more second partially-transparent assist bars located on a second side of the patterned opaque material layer and laterally spaced from the first set of two or more first partially-transparent assist bars by the patterned opaque material layer.
20. The tri-tone lithographic mask of claim 16 , wherein:
the patterned opaque material layer comprises chromium;
the patterned partially-transparent material layer comprises molybdenum silicide; and
the transparent substrate comprises glass or quartz.