In-line particle detection for immersion lithography

1. An immersion lithography system, comprising:

a lens unit configured to project a pattern from an end thereof and onto a wafer;

a hood unit configured to confine an immersion fluid to a region of the wafer surrounding the end of the lens unit;

a wafer stage configured to position the wafer proximate the end of the lens unit; and

an image capturing apparatus coupled to the wafer stage and configured to capture an image of a surface of the hood unit proximate the wafer stage during projection of the pattern onto the wafer.

2. The system of claim 1 wherein the image capturing apparatus comprises a light source and a CCD camera.

3. The system of claim 2 wherein the light source is configured to illuminate the surface of the hood unit and the CCD camera is configured to detect illumination reflected from the surface of the hood to thereby detect image defects associated with the surface of the hood unit.

4. The system of claim 2 wherein the light source and CCD camera are embedded in a sensor plate module coupled to the wafer stage.

5. The system of claim 4 wherein the sensor plate module is watertight.

6. A method for immersion lithography, comprising:

positioning a wafer proximate the end of a lens unit using a wafer stage;

projecting a pattern onto the wafer using the lens unit while confining an immersion fluid to a region of the wafer surrounding an end of the lens unit using a hood unit; and

capturing an image of a surface of the hood unit proximate the wafer stage during projection of the pattern onto the wafer using an image capturing apparatus coupled to the wafer stage.

7. The method of claim 6 further comprising cleaning the surface of the hood unit based on analysis of the captured image.

8. The method of claim 7 wherein the image capturing apparatus is configured for automatic in-line detection of particles on the surface of the hood unit.

9. The method of claim 8 wherein the image capturing apparatus is further configured to automatically trigger cleaning of the surface of the hood unit in response to detection of particles on the surface of the hood unit.

10. The method of claim 6 further comprising capturing a baseline image of the surface of the hood unit before positioning the wafer stage proximate the end of the lens unit and projecting the pattern onto the wafer.

11. An immersion lithography system, comprising:

a lens unit configured to project a pattern from an end thereof and onto a wafer;

a hood unit configured to confine an immersion fluid to a region of the wafer surrounding the end of the lens unit;

a wafer stage configured to position the wafer proximate the end of the lens unit, the wafer stage comprising an integrated image capturing apparatus configured to capture an image of a surface of the hood unit proximate the wafer stage during projection of the pattern onto the wafer.

12. The system of claim 11 wherein the image capturing apparatus comprises a light source and a CCD camera.

13. The system of claim 12 wherein the light source is configured to illuminate the surface of the hood unit and the CCD camera is configured to detect illumination reflected from the surface of the hood to thereby detect image defects associated with the surface of the hood unit.

14. The system of claim 12 wherein the light source and CCD camera are embedded in a sensor plate module integrated with the wafer stage.

15. The system of claim 14 wherein the sensor plate module is watertight.

16. The system of claim 14 wherein the integrated image capturing apparatus is embedded within the wafer stage during projection of the pattern onto the wafer.