Metrology method and apparatus

Patent metadata

Field	Value
Publication number	US-2016146740-A1
Application number	US-201514945257-A
Country	US
Kind code	A1
Filing date	Nov 18, 2015
Priority date	Nov 21, 2014
Publication date	May 26, 2016
Grant date	—

Abstract

A method to determine an overlay error between a first structure and a second structure, wherein the first structure and second structures are on different layers on a substrate and are imaged onto the substrate by a lithographic process, the method comprising: obtaining an apparent overlay error; obtaining a systematic error caused by a factor other than misalignment of the first and second structures; and determining the overlay error by removing the systematic error from the apparent overlay error. The method may alternatively comprise obtaining apparent characteristics of diffraction orders of diffraction by an overlapping portion of the first and second structures; obtaining corrected characteristics of the diffraction orders; determining the overlay error from the corrected characteristics; and adjusting a characteristic of the lithographic process based on the overlay error.

First claim

What is claimed is:

1 . A method to determine an overlay error between a first structure and a second structure, wherein the first structure and second structures are on different layers on a substrate and are imaged onto the substrate by a lithographic process, the method comprising:
obtaining an apparent overlay error; obtaining a systematic error caused by a factor other than misalignment of the first and second structures; and determining the overlay error by removing the systematic error from the apparent overlay error.

2 . The method of claim 1 , wherein obtaining the systematic error comprises determining the systematic error after the first structure is fabricated and before the second structure is fabricated.

3 . The method of claim 1 , wherein obtaining the systematic error comprises determining the systematic error after both the first and second structures are fabricated.

4 . The method of claim 1 , wherein part of the first structure but not part of the second structure is in a first area, wherein parts of both the first and second structures are in a third area.

5 . The method of claim 4 , wherein part of the second structure but not part of the first structure is in a second area.

6 . The method of claim 4 , wherein obtaining the systematic error comprises obtaining an apparent characteristic of diffraction orders of both the first and second structures in the third area, and a characteristic of the first structure in the first area.

7 . The method of claim 5 , wherein obtaining the systematic error comprises obtaining an apparent characteristic of diffraction orders of both the first and second structures in the third area, a characteristic of the first structure in the first area, and a characteristic of the second structure in the second area.

8 . The method of claim 6 , wherein the characteristic of the first structure comprises periodicity, shape, size or a combination thereof, of the first structure; or wherein the characteristic of the second structure comprises periodicity, shape, size or a combination thereof, of the second structure.

9 . The method of claim 1 , wherein the first structure is a first grating at least partially overlapping the second structure, and/or wherein the second structure is a second grating at least partially overlapped by the first structure.

10 . The method of claim 1 , wherein obtaining the apparent overlay error comprises interpolating or extrapolating from a fitted curve.

11 . The method of claim 1 , further comprising adjusting a characteristic of the lithographic process based on the overlay error.

12 . A method to determine an overlay error between a first structure and a second structure, wherein the first structure and second structures are on different layers on a substrate and are imaged onto the substrate by a lithographic process, the method comprising:
obtaining an apparent characteristic of diffraction orders of diffraction by an overlapping portion of the first and second structures; obtaining a corrected characteristic of the diffraction orders; and determining the overlay error from the corrected characteristic.

13 . The method of claim 12 , wherein obtaining the corrected characteristic comprises subtracting from the apparent characteristic a contribution of a factor other than misalignment of the first and second structures.

14 . The method of claim 12 , wherein obtaining the corrected characteristic comprises determining the contribution after the first structure is fabricated and before the second structure is fabricated.

15 . The method of claim 12 , wherein obtaining the corrected characteristic comprises determining the contribution after both the first and second structures are fabricated.

16 . The method of claim 12 , wherein part of the first structure but not part of the second structure is in a first area, wherein parts of both the first and second structures are in a third area.

17 . The method of claim 12 , wherein the first structure is a first grating at least partially overlapping the second structure, and/or wherein the second structure is a second grating at least partially overlapped by the first structure.

18 . The method of claim 12 , wherein obtaining the apparent characteristic comprises optically measuring diffraction.

19 . The method of claim 12 , further comprising adjusting a characteristic of the lithographic process based on the overlay error.

20 . A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions when executed by a computer implementing the method of claim 1 .

Assignees

• Asml Netherlands Bv

Inventors

• Lu Yen-Wen
• Chen Jay Jianhui
• Liu Wei
• Menchtchikov Boris
• Wang Jen-Shiang
• Huang Te-Chih

Classifications

• G01B11/272

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