Two-dimensional structure for determining an overlay accuracy by means of scatterometry

• US 20030224261A1
• Filed: 11/25/2002
• Published: 12/04/2003
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Advanced Micro Devices, Inc.
• Original Assignee: Advanced Micro Devices, Inc.
• Inventors: Schulz, Bernd
• Granted Patent: US 7,099,010 B2
• Time in Patent Office: Days
• US Class Current: 430/22
• CPC Class Codes: G01B 11/272 using photoelectric detection means
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• CPC Class Codes: H01L 2223/54453 for use prior to dicing
• CPC Class Codes: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A two-dimensional periodic pattern that is symmetrical with respect to a first and a second direction allows the determination of an overlay accuracy that is obtained during the fabrication of the two-dimensional structure. Due to the symmetry of the structure, the overlay accuracy in the first direction may be determined on the basis of substantially the same reference data as used for the determination of the overlay accuracy of the second direction so that establishing libraries is simplified. Moreover, depending on the capability of the metrology tool, the overlay accuracy in both directions may be obtained simultaneously.

Claims

1. A structure for estimating an overlay accuracy in forming successive material layers on a substrate, the structure comprising:

a substrate having formed thereon a plurality of first and second regions, the first and the second regions arranged to form a periodic pattern having a predefined first periodicity along a first direction and along a second direction; and

a plurality of third regions, each of which overlies one of said second regions so as to exhibit a predefined second periodicity, with a pitch that is substantially equal to a pitch of said periodic pattern, along the first and the second directions.

2. The structure of claim 1, wherein the size of the first, the second and the third regions is selected so that each third region lies within the respective second region for a given maximum overlay inaccuracy.

3. The structure of claim 1, wherein each of the first, second and third regions is enclosed by a perimeter region.

4. The structure of claim 3, wherein said perimeter region defines one of a circular shape and a regular polygonal shape.

5. The structure of claim 1, wherein the first region and the second region differ from each other in at least one of type of material and surface topology.

6. The structure of claim 1, wherein the second and the third regions differ from each other in at least one of type of material and surface topology.

7. The structure of claim 1, wherein the first and second regions are substantially equally sized squares.

8. A method of forming a semiconductor device, including a structure for determining an overlay accuracy, the method comprising:

forming a first material layer on a surface of a substrate, the first material layer including a plurality of first regions of a first optical characteristic and a plurality of second regions of a second optical characteristic, the first and second regions arranged to form a two-dimensional periodic pattern with a predefined periodicity along a first direction and a second direction that are substantially parallel to said surface;

aligning said substrate with respect to a second material layer to be formed; and

forming said second material layer, the second material layer including a plurality of third regions, each of the third regions partially covering a respective one of said second regions, wherein a relative position of the third region with respect to the second region is indicative of the overlay accuracy of the first and second material layers with respect to the first and second directions.

9. The method of claim 8, wherein a size of the first, the second and the third regions is selected so that each third region is formed within the respective second region for a given maximum overlay inaccuracy.

10. The method of claim 8, wherein each of the first, second and third regions is enclosed by a perimeter region defining a shape that is symmetrical with respect to a transformation which maps the first direction into the second direction.

11. The method of claim 8, wherein the first and the second regions differ from each other in at least one of type of material and surface topology.

12. The method of claim 8, wherein the second and the third regions differ from each other in at least one of type of material and surface topology.

13. A method of monitoring an overlay accuracy in manufacturing a semiconductor device, the method comprising:

identifying a structure including a plurality of first and second regions, the first and second regions arranged to form a periodic pattern having a predefined first periodicity along a first direction and along a second direction, a plurality of third regions, each of which overlies one of said second regions so as to exhibit a predefined second periodicity along the first and the second directions;

directing a first light beam onto said structure under an angle of incidence such that a portion of the first light beam is reflected to form a first reflected light beam, wherein the first light beam and the first reflected light beam form a plane of incidence that is substantially parallel to said first direction;

detecting said first reflected light beam to obtain a first measurement data;

estimating an overlay accuracy with respect to said first direction on the basis of the first measurement data and reference data;

directing a second light beam onto said structure under an angle of incidence such that a portion of the second reflected light beam is reflected to form a second reflected light beam, wherein the second light beam and the second reflected light beam form a plane of incidence that is substantially parallel to the second direction;

detecting said second reflected light beam to obtain a second measurement data; and

estimating an overlay accuracy with respect to the second direction on the basis of the second measurement data and reference data.

14. The method of claim 13, wherein said first and second light beam are substantially simultaneously directed onto said structure.

15. The method of claim 13, wherein directing said second light beam includes rotating at least one of said substrate and a light source.

16. The method of claim 13, wherein said reference data for estimating an overlay accuracy with respect to the first direction is substantially the same as for estimating an overlay accuracy with respect to the second direction.

17. A substrate comprising a plurality of chip areas and at least one structure including a plurality of first and second regions, the first and second regions arranged to form a periodic pattern having a predefined first periodicity along a first direction and along a second direction, and a plurality of a third regions, each of which overlies one of the second regions so as to exhibit a predefined second periodicity along the first and the second directions.

18. The substrate of claim 17, wherein at least some of said chip areas are separated from each other by scribe lines and said at least one structure is located in at least one of the scribe lines.

19. The substrate of claim 18, wherein said at least one structure is located in at least one chip area.