US 5,773,836 AGranted

Method for correcting placement errors in a lithography system

AssigneeInternational Business Machines Corporation

InventorJohn George Hartley

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Abstract

A method for correcting placement errors in a lithography system, and a system therefor, are disclosed. The method comprises the steps of obtaining metrology data of sufficient density to smoothly map an error to be corrected, deriving a metrology data grid coordinate system from the data, aligning the metrology data grid coordinate system to remove rigid body components, and for each of a plurality of lithographic fields: identifying a number of metrology sites nearest to the center of the field; establishing a reference grid coordinate system coinciding with the lithographic field; determining at least one correction factor which minimizes the residual errors; and applying at least one correction factor for at least one field to the first lithography system to correct a placement error. Such a method and system are particularly useful for error correction in e beam lithography tools.

Claims11

Dependent claims

A method for correcting placement errors in a lithography system comprising the steps of:

(a) obtaining metrology data from at least one substrate selected from (i) a lithographic substrate produced by a first lithography system and (ii) a lithographic substrate produced by a second lithography system using a substrate produced by said first lithography system, said data being of sufficient density to smoothly map an error to be corrected;
(b) deriving a metrology data grid coordinate system from said metrology data;
(c) aligning the metrology data grid coordinate system to the coordinate system of said first lithography system to remove rigid body errors;
and
(d) for each of a plurality of first lithography system substrate fields,
(i) determining a smoothness radius about the center of said field and the total number of metrology sites lying within an area defined by said smoothness radius about the center of said field;
(ii) identifying from said total number of metrology sites in step (d)(i) a number N of metrology sites about the center of the field, wherein N is not less than the number of degrees of freedom to be corrected, and wherein none of the N sites is collinear with any other two of the sites;
(iii) establishing a reference grid coordinate system wherein the origin of said reference grid coordinate system coincides with center of said field;
and
(iv) fitting the metrology data for the identified N metrology sites to the reference grid coordinate system to determine at least one correction factor which minimizes residual errors;
and
(e) applying at least one correction factor for at least one field to said first lithography system to correct a placement error.

9 more elements

A system for correcting placement errors in a lithography system comprising:

(a) a means for obtaining metrology data from at least one substrate selected from (i) a lithographic substrate produced by a first lithography system and (ii) a lithographic substrate produced by a second lithography system using a substrate produced by said first lithography system, said data being of sufficient density to smoothly map an error to be corrected;
(b) a means for deriving a metrology data grid coordinate system from said metrology data;
(c) a means for aligning the metrology data grid coordinate system to the coordinate system of said first lithography system to remove rigid body error;
and
(d) a means capable of operating on each of a plurality of first lithography system substrate fields, said means being for
(i) determining a smoothness radius about the center of said field and the total number of metrology sites lying within an area defined by said smoothness radius about the center of said field;
(ii) identifying from said total number of metrology sites in step (d)(i) a number N of metrology sites about the center of the field, wherein N is not less than the number of degrees of freedom to be corrected, and wherein none of the N sites is collinear with any other two of the N sites;
(iii) establishing a reference grid coordinate system wherein the origin of said reference grid coordinate system coincides with center of said field;
and
(iv) fitting the metrology data for the identified N metrology sites to the reference grid coordinate system to determine at least one correction factor which minimizes residual errors;
and
(e) a placement error correction means for said first lithography system which means is responsive to at least one correction factor for at least one field of said first lithography system.

9 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/739,137Filed 28 Oct 1996
Granted: 30 Jun 1998
Term ends: Not estimatedThe source records don’t support an estimate.

Classification10 codes

G03F 7/706
Testing optical components: aberration measurement
G03F 7/70425
Microphotolithographic exposure; Apparatus therefor: imaging strategies, e.g. for increasing throughput or resolution, printing product fields…
G03F 7/70475
Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating…
G03F 7/70633
Monitoring the printed patterns: overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the…