In-process correction of stage mirror deformations during a photolithography exposure cycle

• US 20040135980A1
• Filed: 12/12/2003
• Published: 07/15/2004
• Est. Priority Date: 12/12/2002
• Status: Active Grant

• Current Assignee: Zygo Corporation (Ametek Incorporated)
• Original Assignee: Zygo Corporation (Ametek Incorporated)
• Inventors: Hill, Henry A.
• Granted Patent: US 7,075,619 B2
• Time in Patent Office: Days
• US Class Current: 355/52
• CPC Class Codes: G01B 2290/45 Multiple detectors for detecting interferometer signals
• CPC Class Codes: G01B 2290/70 Using polarization in the interferometer
• CPC Class Codes: G01B 9/02018 Multipass interferometers, e.g. double-pass
• CPC Class Codes: G01B 9/02019 contacting different points on same face of object
• CPC Class Codes: G01B 9/02021 contacting different faces of object, e.g. opposite faces
• CPC Class Codes: G01B 9/02027 Two or more interferometric channels or interferometers
• CPC Class Codes: G01B 9/0207 Error reduction by correction of the measurement signal based on independently determined error sources, e.g. using a reference interferometer
• CPC Class Codes: G03F 7/70591 Testing optical components
• CPC Class Codes: G03F 7/70775 Position control, e.g. interferometers or encoders for determining the stage position

Abstract

A microlithography method includes: interferometrically measuring information about a position of a microlithography stage with respect to each of multiple metrology axes during a photolithographic exposure cycle; analyzing the position information to determine correction factors indicative of a local slope on a side of the stage used to reflect an interferometric measurement beam and optical gradients caused by environmental effects produced by the photolithographic exposure cycle; and applying the correction factors to subsequent interferometric measurements of the stage.

Claims

1. A microlithography method including:

interferometrically measuring information about a position of a microlithography stage with respect to each of multiple metrology axes during a photolithographic exposure cycle;

analyzing the position information to determine correction factors indicative of local slope oil a side of the stage used to reflect an interferometric measurement beam and optical gradients caused by environmental effects produced by the photolithographic exposure cycle; and

applying the correction factors to subsequent interferometric measurements of the stage.

2. The method of claim 1, wherein the stage carries a wafer exposed to illumination light during the photolithographic exposure cycle.

3. The method of claim 1, wherein the stage carries a reticle through which illumination light passes to expose a wafer during the photolithographic exposure cycle.

4. The method of claim 1, wherein the information is measured when exposing a first region of a wafer during the photolithography exposure cycle, and wherein the correction factors are applied to subsequent interferometric measurements of the stage when exposing subsequent regions or layers of the wafer during the photolithography exposure cycle.

5. The method of claim 1, wherein the information is measured when exposing a first region of a wafer during the photolithography exposure cycle, and wherein the correction factors are applied to subsequent interferometric measurements of the stage when exposing a region of another wafer during its photolithography exposure cycle.

6. The method of claim 1, wherein the correction factors are determined based on averaging information for multiple scans of the stage along at least a first direction.

7. The method of claim 1, wherein the position information is measured using at least one high stability plane mirror interferometer.

8. The method of claim 1, wherein the position information is measured using at least one single beam interferometer.

9. The method of claim 8, wherein the single beam interferometer is a dynamic single beam interferometer.

10. The method of claim 8, wherein the single beam interferometer is a passive single beam interferometer.

11. The method of claim 1, wherein the correction factors are indicative of the local slope on at least two sides of the stage used to reflect an interferometric measurement beam.

12. The method of claim 1, wherein the correction factors are indicative of the local slope of the side of the stage along an in-plane direction.

13. The method of claim 1, wherein the multiple metrology axes provide redundant information about the stage position in the absence of the local slope and optical gradient variations.

14. A method comprising fabricating integrated circuits using tile lithography method of claim 1.