Reticle for determining rotational error
View Patent ↗A method for determining rotational error portion of total misalignment error in a stepper. In one embodiment, the method comprises a series of steps in a stepper, starting with the step of receiving a wafer, having a first pattern and an error-free fine alignment target, in the stepper. In another step, the wafer is aligned in the stepper using the error-free fine alignment target. Then a second pattern is created on the wafer overlaying said first pattern. In another step, the rotational error portion of the total misalignment error is determined by measuring the circumferential misalignment between the first pattern and the second pattern.
1. A reticle adaptable for determining a rotational error portion of a total misalignment error, said reticle comprising:
a first pattern, said first pattern located in a center region of said reticle, said first pattern including a fine alignment target; and
a second pattern, said second pattern located in an outer region of said reticle, said second pattern and said first pattern adaptable to form overlaying images in a wafer for measuring said rotational error portion of a total misalignment error.
2. The reticle recited in claim 1 wherein said first pattern is an overlay.
3. The reticle recited in claim 1 wherein said first pattern is a duplicate fine alignment target.
4. The reticle recited in claim 1 wherein said second pattern is a mating overlay.
5. The reticle recited in claim 1 wherein said mating overlay is adapted to overlay a fine alignment target.
6. The reticle recited in claim 1 further comprising a plurality of second patterns, said second patterns arranged in a matrix.
7. An arrangement for determining a rotational error portion of a total misalignment error on a wafer, the arrangement comprising:
a stepper that includes a light source, masking blades, a lens and a stage; and
a reticle having
a first pattern located in a center region of the reticle, the first pattern including a fine alignment target, and
a second pattern located in an outer region of the reticle, wherein the second pattern and the first pattern form overlaying images in the wafer for measuring the rotational error portion of the total misalignment error.
8. The arrangement recited in claim 7 , wherein the first pattern is an overlay.
9. The arrangement recited in claim 7 , wherein the first pattern is a duplicate fine alignment target.
10. The arrangement recited in claim 7 , wherein the second pattern is a mating overlay.
11. The arrangement recited in claim 10 , wherein the mating overlay is adapted to overlay a fine alignment target.
12. The arrangement recited in claim 7 , further comprising a plurality of the second patterns, the plurality of second patterns arranged in a matrix.
13. The arrangement recited in claim 7 , wherein the fine alignment target is projected through a center region of the stepper lens onto the wafer.
14. The arrangement recited in claim 7 , wherein the second pattern is projected through an outer region of the stepper lens onto the wafer.