Apparatus and methods for determining overlay of structures having rotational or mirror symmetry
First Claim
1. A semiconductor target for determining a relative shift between two or more successive layers of a substrate, the target comprising:
- a plurality of first structures formed in a first layer with a first center of symmetry (COS); and
a plurality of second structures formed in a second layer with a second COS, wherein the first and second structures have a particular rotational symmetry, without having a second rotational symmetry, with respect to the first and second COS, respectively,wherein the first COS and the second COS correspond to an overlay error between the first and second structures, and wherein the first and second structures have a 180°
rotational symmetry, without having a second different rotational symmetry, with respect to the first and second COS, respectively.
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Abstract
A semiconductor target for determining a relative shift between two or more successive layers of a substrate is provided. The target comprises a plurality of first structures formed in a first layer, and the first structures have a first center of symmetry (COS). The target further comprises a plurality of second structures formed in a second layer, and the second structures have second COS. The difference between the first COS and the second COS corresponds to an overlay error between the first and second layer and wherein the first and second structures have a 180° rotational symmetry, without having a 90° rotational symmetry, with respect to the first and second COS, respectively.
221 Citations
22 Claims
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1. A semiconductor target for determining a relative shift between two or more successive layers of a substrate, the target comprising:
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a plurality of first structures formed in a first layer with a first center of symmetry (COS); and a plurality of second structures formed in a second layer with a second COS, wherein the first and second structures have a particular rotational symmetry, without having a second rotational symmetry, with respect to the first and second COS, respectively, wherein the first COS and the second COS correspond to an overlay error between the first and second structures, and wherein the first and second structures have a 180°
rotational symmetry, without having a second different rotational symmetry, with respect to the first and second COS, respectively.
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2. A semiconductor target for determining a relative shift between two or more successive layers of a substrate, the target comprising:
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a plurality of first structures formed in a first layer, and the first structures having at least two subsets of the first structures that are spaced apart from each other and have a first center of symmetry (COS); and a plurality of second structures formed in a second layer, and the second structures having at least two subsets of the second structures that are spaced apart from each other and have a second COS, wherein the difference between the first COS and the second COS corresponds to an overlay error between the first and second structures and wherein the first and second structures have a 180°
rotational symmetry, without having a 90°
rotational symmetry, with respect to the first and second COS, respectively. - View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A metrology system for measuring an overlay error of a target, comprising:
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a scatterometry module for directing radiation towards a plurality of targets and detecting scattered signals from the targets; and a processor configured to analyze the detected scattered signals to thereby determine an overlay error of such targets, wherein the targets comprise a plurality of first structures formed in a first layer with a first center of symmetry (COS) and a plurality of second structures formed in a second layer with a second COS, wherein the first and second structures have a particular rotational symmetry, without having a second rotational symmetry, with respect to the first and second COS, respectively, wherein the first COS and the second COS correspond to an overlay error between the first and second structures, and wherein the first and second structures have a 180°
rotational symmetry, without having a second different rotational symmetry, with respect to the first and second COS, respectively. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22)
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Specification