STRUCTURE AND METHOD FOR DETERMINING AN OVERLAY ACCURACY
First Claim
1. An overlay target assembly adapted for use in determining an alignment accuracy of a first layer and a second layer of a multi-layered device, said assembly comprising:
- at least two targets, each target having a first sub-structure of said first layer and a second sub-structure of said second layer;
wherein, when said first layer and said second layer are correctly aligned;
said first sub-structure and said second sub-structure of at least one of said targets are offset with respect to each other by a programmed offset; and
said overlay target assembly is invariant to at least one transformation selected from rotation about a predetermined angle and reflection.
6 Assignments
0 Petitions
Accused Products
Abstract
An enhanced technique for determination of an alignment accuracy involves an overlay target assembly which comprises at least two targets, each target having a first sub-structure of a first layer and a second sub-structure of a second layer, wherein, when the first layer and the second layer are correctly aligned, the first sub-structure and the second sub-structure of at least one of the targets are offset with respect to each other by a programmed offset and the overlay target assembly is invariant to at least one geometric transformation. If the offset vectors which describe the offset between the first sub-structure and the second sub-structure all have the same norm, the overlay error may be determined without calibration. Redundancy may be increased by providing each target with two or more programmed offsets between elements of the first sub-structure and elements of the second sub-structure.
-
Citations
20 Claims
-
1. An overlay target assembly adapted for use in determining an alignment accuracy of a first layer and a second layer of a multi-layered device, said assembly comprising:
-
at least two targets, each target having a first sub-structure of said first layer and a second sub-structure of said second layer; wherein, when said first layer and said second layer are correctly aligned; said first sub-structure and said second sub-structure of at least one of said targets are offset with respect to each other by a programmed offset; and said overlay target assembly is invariant to at least one transformation selected from rotation about a predetermined angle and reflection. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. An overlay target structure adapted for use in determining an alignment accuracy of a first layer and a second layer of a multi-layered device, said structure comprising:
-
a first sub-structure of said first layer; and a second sub-structure of said second layer, wherein; when said first layer and said second layer are correctly aligned, said first sub-structure and said second sub-structure are offset with respect to each other; and said overlay target structure is invariant to at least one transformation selected from rotation about a predetermined angle and reflection.
-
-
19. A method, comprising:
-
forming an overlay target assembly comprising; at least two targets, each target having a first sub-structure of a first layer and a second sub-structure of a second layer; wherein, when said first layer and said second layer are correctly aligned; said first sub-structure and said second sub-structure of at least one of said targets are offset with respect to each other by a programmed offset; and said overlay target assembly is invariant to at least one transformation selected from rotation about a predetermined angle and reflection; and determining an alignment accuracy between said first layer and said second layer from a spatial relationship of said first sub-structure and said second sub-structure of said at least two targets. - View Dependent Claims (20)
-
Specification