METHOD TO DETERMINE THE USEFULNESS OF ALIGNMENT MARKS TO CORRECT OVERLAY, AND A COMBINATION OF A LITHOGRAPHIC APPARATUS AND AN OVERLAY MEASUREMENT SYSTEM
First Claim
1. A method comprising:
- a) transferring a first pattern to a substrate, said first pattern including at least N alignment marks, wherein each alignment mark is positioned at a respective predefined nominal position in the first pattern;
b) measuring a position of each of the N alignment marks and determining an alignment mark displacement for each of the N alignment marks from the respective nominal position by comparing the respective nominal position of an alignment mark with the respective measured position of said alignment mark;
c) fitting a model to the N alignment mark displacements;
d) transferring a second pattern to the substrate using the fitted model in order to align the second pattern with respect to the first pattern;
e) measuring an overlay error by measuring a relative position of the first pattern with respect to the second pattern, wherein said overlay error is representative for a displacement of the second pattern relative to a perfect alignment between first and second pattern;
f) determining a model error for each of the N alignment marks by comparing the position of an alignment mark according to the fitted model with the respective measured position of said alignment mark;
g) comparing the determined model errors with the overlay error; and
h) determining a usefulness of each of the N alignment marks to correct the corresponding overlay error based on the comparison between model errors and overlay error.
1 Assignment
0 Petitions
Accused Products
Abstract
A method to determine the usefulness of an alignment mark of a first pattern in transferring a second pattern to a substrate relative to the first pattern already present on the substrate includes measuring the position of the alignment mark, modeling the position of the alignment mark, determining the model error between measured and modeled position, measuring a corresponding overlay error between first and second pattern and comparing the model error with the overlay error to determine the usefulness of the alignment mark. Subsequently this information can be used when processing next substrates thereby improving the overlay for these substrates. A lithographic apparatus and/or overlay measurement system may be operated in accordance with the method.
17 Citations
15 Claims
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1. A method comprising:
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a) transferring a first pattern to a substrate, said first pattern including at least N alignment marks, wherein each alignment mark is positioned at a respective predefined nominal position in the first pattern; b) measuring a position of each of the N alignment marks and determining an alignment mark displacement for each of the N alignment marks from the respective nominal position by comparing the respective nominal position of an alignment mark with the respective measured position of said alignment mark; c) fitting a model to the N alignment mark displacements; d) transferring a second pattern to the substrate using the fitted model in order to align the second pattern with respect to the first pattern; e) measuring an overlay error by measuring a relative position of the first pattern with respect to the second pattern, wherein said overlay error is representative for a displacement of the second pattern relative to a perfect alignment between first and second pattern; f) determining a model error for each of the N alignment marks by comparing the position of an alignment mark according to the fitted model with the respective measured position of said alignment mark; g) comparing the determined model errors with the overlay error; and h) determining a usefulness of each of the N alignment marks to correct the corresponding overlay error based on the comparison between model errors and overlay error. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. In combination a lithographic apparatus and an overlay measurement system, wherein the lithographic apparatus comprises:
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an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate; an alignment system with an alignment sensor, said alignment sensor being configured to measure the position of alignment marks on a substrate, and a lithographic apparatus control unit configured to control the position of the patterned radiation beam relative to a substrate based on the measured position of the alignment marks on the substrate; wherein the overlay measurement system comprises an overlay sensor configured to measure a relative position between two patterns on a substrate, and an overlay measurement control unit configured to determine an overlay error based on the measured relative position, wherein the lithographic apparatus is configured to carry out; a) transferring a first pattern to a substrate, said first pattern including at least N alignment marks, wherein each alignment mark is positioned at a respective predefined nominal position in the first pattern; b) measuring a position of N alignment marks and determining an alignment mark displacement for each of the N alignment marks from the respective nominal position by comparing the respective nominal position of an alignment mark with the respective measured position of said alignment mark; c) fitting a model to the N alignment mark displacements; d) transferring a second pattern to the substrate using the fitted model in order to align the second pattern with respect to the first pattern; and wherein the overlay measurement system is configured to carry out; e) measuring an overlay error by measuring a relative position of the first pattern with respect to the second pattern, wherein said overlay error is representative for a displacement of the second pattern relative to a perfect alignment between first and second pattern; f) determining a model error for each of the N alignment marks by comparing the position of an alignment mark according to the fitted model with the respective measured position of said alignment mark; g) comparing the determined model errors with the overlay error; and h) determining a usefulness of each of the N alignment marks to correct the corresponding overlay error based on the comparison between model errors and overlay error. - View Dependent Claims (14, 15)
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Specification