Substrate for Use in Metrology, Metrology Method and Device Manufacturing Method
First Claim
1. A substrate comprising:
- a target, the target having at least one individual grating portion having a structure periodic in a first direction for use in diffraction-based metrology, the grating portion having a length in the first direction and a width in a second direction, perpendicular to the first direction, andwherein an aspect ratio of the grating portion, being a ratio of the length to the width, is substantially greater than 1.
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Accused Products
Abstract
A pattern from a patterning device is applied to a substrate. The applied pattern includes device functional areas and metrology target areas. Each metrology target area comprises a plurality of individual grating portions, which are used for diffraction based overlay measurements or other diffraction based measurements. The gratings are of the small target type, which is small than an illumination spot used in the metrology. Each grating has an aspect ratio substantially greater than 1, meaning that a length in a direction perpendicular to the grating lines which is substantially greater than a width of the grating. Total target area can be reduced without loss of performance in the diffraction based metrology. A composite target can comprise a plurality of individual grating portions of different overlay biases. Using integer aspect ratios such as 2:1 or 4:1, grating portions of different directions can be packed efficiently into rectangular composite target areas.
214 Citations
33 Claims
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1. A substrate comprising:
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a target, the target having at least one individual grating portion having a structure periodic in a first direction for use in diffraction-based metrology, the grating portion having a length in the first direction and a width in a second direction, perpendicular to the first direction, and wherein an aspect ratio of the grating portion, being a ratio of the length to the width, is substantially greater than 1. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A patterning device comprising:
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functional pattern features; and target pattern features, the target pattern features being formed to produce a grating portion if a pattern is applied from the patterning device to a substrate, wherein the grating portion has a structure periodic in a first direction for use in diffraction-based metrology, the grating portion having a length in the first direction and a width in a second direction, perpendicular to the first direction, and wherein an aspect ratio of the grating portion, being a ratio of the length to the width, is substantially greater than 1. - View Dependent Claims (15, 16)
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17. A method of inspecting a substrate having a target for diffraction-based metrology, the target having at least one individual grating portion having a structure periodic in a first direction, the method comprising:
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illuminating the target and detecting radiation diffracted by the periodic structure in directions spread angularly into one or more diffraction orders, wherein the illumination falls on parts of the substrate other than the individual grating portion, wherein an image of the target including the other parts is formed using a selection from among the diffraction orders, wherein the image is analyzed to select an image portion corresponding to the individual grating portion, wherein the individual grating portion has a length in the first direction and a width in a second direction, perpendicular to the first direction, and wherein an aspect ratio of the grating portion, being a ratio of the length to the width, is substantially greater than 1. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
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30. A device manufacturing method comprising:
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transferring a functional device pattern from a patterning device onto a substrate using a lithographic apparatus while substantially simultaneously transferring a metrology target pattern to the substrate; measuring the metrology target pattern by diffraction based metrology; and applying a correction in subsequent operations of the lithographic apparatus in accordance with the results of the diffraction based metrology, wherein the metrology target pattern comprises at least one individual grating portion having a structure periodic in a first direction, each of the grating portions having a length in the first direction and a width in a second direction, perpendicular to the first direction, and wherein an aspect ratio of the grating portion, being a ratio of the length to the width, is substantially greater than 1. - View Dependent Claims (31, 32, 33)
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Specification