Method for manufacturing a magnetic write head
View Patent ↗A method for measuring recession in a wafer undergoing an asymmetrical ion mill process. The method includes the formation of first and second reference features and possibly a dummy feature. The reference features are constructed such that the location of the midpoint between them is unaffected by the asymmetrical ion mill. By measuring the distance between a portion of the dummy feature and the midpoint between the reference features, the amount of recession of the dummy feature can be measured. The measurement can be used to calculate the relative location of the flare to the read sensor rear edge through overlay information. By keeping the angles of the sides of the features steep (ie. nearly parallel with the direction in which the ion mill is asymmetrical) the amount of material consumed on each of the reference features is substantially equal and the midpoint between the reference features is substantially stationary.
1. A method for manufacturing a magnetic write head, comprising:
providing a wafer;
depositing material on the wafer;
performing a photolithographic patterning step, the patterning step defining a plurality of features on the material and also defining first and second reference features on the material, the first and second reference features being separated by a distance measured in a y direction;
performing a sweeping ion mill to the plurality of features and the first and second reference features formed on the material, the sweeping ion mill being symmetrical in an x direction and asymmetrical in the y direction; and
measuring a distance between one of the plurality of features and a midpoint between the reference features.
2. The method as in claim 1 wherein the first and second reference features each have a width measured along the x direction and a length measured in the y direction, and where in the width is smaller than the length.
3. The method as in claim 1 wherein the first and second reference features are isosceles triangles each having an apex that faces an apex of the other reference feature.
4. The method as in claim 1 wherein the first and second reference features are isosceles triangles each having an apex that faces an apex of the other reference feature, the triangles each having first and second sides that define an angle less than or equal to 10 degrees with respect to the y direction.
5. The method as in claim 1 wherein the first and second reference features are isosceles triangles each having an apex that faces the apex of the other reference feature, the triangles each having first and second sides that define an angle less than 5 degrees with respect to the y axis.
6. A method for manufacturing a magnetic write head, comprising:
providing a wafer;
depositing a magnetic material;
depositing a photosensitive mask material;
photolithographically patterning the photosensitive mask material to define a dummy write pole feature having a flare point, and first and second reference features each being separated by a distance measured in a y direction and defining a midpoint between the first and second reference features;
performing a sweeping ion mill to the dummy write pole feature and the first and second reference features, the sweeping ion mill being asymmetrical in the y direction and symmetrical in an x direction that is perpendicular to the y direction; and
measuring a distance between the flare point of the dummy write pole feature and the midpoint between the first and second reference features.
7. The method as in claim 6 further comprising terminating the sweeping ion mill when the distance between the flare point in the dummy write pole feature and the midpoint between the first and second reference features reaches a predetermined value.
8. The method as in claim 6 wherein the measuring the distance between the flare point in the write pole feature and the midpoint between the first and second reference features is performed at least partially simultaneously with said sweeping ion mill, the method further comprising terminating the sweeping ion mill when the distance between the flare point in the dummy write pole feature and the midpoint between the first and second reference features reaches a predetermined value.
9. The method as in claim 6 wherein the first and second reference features are narrower in the x direction than in the y direction.
10. The method as in claim 6 wherein the first and second reference features have first and second sides that define an angle of no greater than 10 degrees with respect to the y direction.
11. The method as in claim 6 wherein the first and second reference features each define a triangle having first and second sides that define an angle of no greater than 10 degrees with respect to the with respect to the y direction.
12. The method as in claim 6 wherein the first and second reference features each define an isosceles triangle each having an apex that faces the other reference feature.
13. The method as in claim 6 wherein the first and second reference features each define an isosceles triangle each having an apex that faces the other reference feature and each having first and second sides that define an angle no greater than ten degrees with respect to the y direction.
14. The method as in claim 6 wherein the photolithographic patterning further defines a plurality of write pole features.
15. The method as in claim 6 wherein the photolithographic patterning also defines a write pole, the write pole being symmetrical about the y axis.
16. The as in claim 5 wherein the first and second reference features each define a triangle having first and second sides that define an angle of less than 5 degrees with respect to the y axis.
17. A method for measuring ion mill induced recession, the method comprising:
providing a wafer, the wafer having x and y dimensions, the x dimension being measured in an x axis, and the y dimension being measured in a y axis that is perpendicular to the x axis;
depositing a material on the wafer;
forming first, second and third features on the material, the second and third features being reference features, the second and third features being separated by a distance measured in the y dimension and having a midpoint therebetween;
performing a sweeping ion mill to the first, second and third features formed on the material, the sweeping ion mill being symmetrical in the x direction and asymmetrical in the y direction; and
measuring the distance between the first feature and the midpoint between the second and third features.
18. The method as in claim 17 , wherein the second and third features are both symmetrical about the y axis.
19. The method as in claim 17 wherein the second and third features each have a width measured along the x dimension and a length measured alone the y dimension, and where in the width is smaller than the length.
20. The method as in claim 17 wherein each of the second and third reference features is configured as a triangle configured with first and second sides that define an angle of ten degrees or less with respect to the y axis.
21. The method as in claim 17 wherein each of the second and third reference features is triangle configured with an acute corner, and wherein the acute corner of the second reference feature faces the acute corner of the third reference feature.
22. The method as in claim 17 wherein each of the second and third features is configured as an isosceles triangle configured with an apex, and wherein the apexes of the second and third features face one another.
23. The method as in claim 17 further comprising a fourth feature, and wherein the first feature is a dummy feature that that has a recession rate that is similar to the fourth feature formed on the wafer.
24. The method as in claim 17 wherein the first feature is a dummy feature that has recession rate that is similar to a write pole formed on the wafer.
25. The method as in claim 17 wherein the first feature is a write pole.