Apparatus for aberration detection and measurement

• US 20070019171A1
• Filed: 09/27/2006
• Published: 01/25/2007
• Est. Priority Date: 12/13/2002
• Status: Active Grant

• Current Assignee: Bruce W. Smith
• Original Assignee: Bruce W. Smith
• Inventors: Smith, Bruce
• Granted Patent: US 7,345,735 B2
• Time in Patent Office: Days
• US Class Current: 355/52
• CPC Class Codes: G01M 11/0264 by using targets or reference patterns
• CPC Class Codes: G03F 7/706 Aberration measurement

Abstract

Aberrations in an optical system can be detected and measured using a method comprised of a test target in the object plane of a projection system and imaging a photoresist film with the system. The test target comprises at least one open figure which comprises a multiple component array of phase zones, where the multiple zones are arranged within the open figure so that their response to lens aberration is interrelated and the zones respond uniquely to specific aberrations depending on their location within the figure. This is a unique and new method of detecting a variety of aberration types including coma, spherical, astigmatism, and three-point through the exposure of a photoresist material placed in the image plane of the system and the evaluation of these images.

Claims

1. A test target comprising at least one open figure including a multiple component array of phase zones, wherein the multiple zones are arranged within the open figure so that their responses to lens aberrations are interrelated and the zones respond uniquely to specific aberrations depending on their location within the figure.

2. The test target of claim 1 wherein the multiple component array of phase zones comprises a central phase zone and a plurality of circumferential phase zones.

3. The test target of claim 1 wherein there are at lest two phase zones and one is larger than the other.

4. The test target of claim 1 wherein the circumferential phase zones features are disposed at equal radial locations from the central phase zone and and are equally angularly spaced from each other.

5. The test target of claim 1 wherein there are at least eight circumferential phase zones.

6. The test target of claim 5 wherein the eight cirumferential phase zones are located at 0, 45, 90, 135, 180, 225, 270, and 315 degrees with respect to the central phase zone.

7. The test target of claim 1 having at least two circumferential phase zones spaced 180 degrees apart from each other for detecting positive or neagative astigmatism.

8. The test target of claim 7 having at least two more circumferential phase zones spaced 180 apart from each other and 90 degrees from the first two circumfertial phase zones for deteting positive and negative astigmatism.

9. The test target of claim 1 having at least four circumferential phase zones located at 0, 90, 180, 270 dgreees and two more phase zones at 135 and 315 degrees or 45 and 225 degrees to detect 45 degree astigmatism.

10. The test target of claim 9 wherein the phase zones have the same or different shapes.

11. The test target of claim 9 wherein the phase zones have circular or rectangular sphapes.

12. The test target of claim 9 wherein the phase zones have the same shape.

13. The test target of claim 9 wherein the central phase zone has one shape and the circumferential phase zones have a different shape.

14. The test target of claim 1 wherein the size of the phase zones and the spaces between the phase zones are between 0.5λ

/NA to 1.5λ

/NA where λ

is the wavelenght of the light exposing the target and NA is the numerical aperture of the exposure system.

15. The test target of claim 1 wherein the size of the target is between 2.5λ

/NA to 5.0λ

/NA where λ

is the wavelenght of the light exposing the target and NA is the numerical aperture of the exposure system.

16. The test target of claim 1 wherein the phase zones are 180 degrees out of phase with respect to the rest of the target.

17. The test target of claim 1 wherein the phase zones are etched into the surface of the target.