Focus test mask, focus measurement method, exposure method and exposure apparatus

• US 8,343,693 B2
• Filed: 11/05/2010
• Issued: 01/01/2013
• Est. Priority Date: 11/05/2009
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Hirukawa, Shigeru, Kondo, Shinjiro
• Primary Examiner(s): YOUNG, CHRISTOPHER G
• Application Number:
  US12/940,292
• Publication Number:
  US 20110212389A1
• Time in Patent Office: 788 Days
• Field of Search: 430/5, 430/22, 430/30, 355/53, 382/151
• US Class Current: 430/5
• CPC Class Codes: G03F 1/44 Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales
• CPC Class Codes: G03F 7/70641 Focus
• CPC Class Codes: G03F 9/7026 Focusing

Abstract

A focus test reticle for measuring focus information includes an outer pattern. The outer pattern has a line pattern composed of a light shielding film extending in the Y direction, a phase shift portion provided on a side in the +X direction of the line pattern and formed to have a line width narrower than the line pattern, a transmitting portion provided on a side in the −X direction of the line pattern and formed to have a line width narrower than the line pattern, a transmitting portion provided on a side in the +X direction of the phase shift portion, and a phase shift portion provided on a side in the −X direction of the transmitting portion. Focus information of a projection optical system is measured at a high measuring reproducibility and a high measuring efficiency.

Claims

1. A focus test mask comprising a test pattern which is to be projected onto an object via a projection optical system,

wherein the test pattern includes:

a first light shielding portion which extends in a line form in a first direction and which shields a light;

a first phase shift portion which is provided on one side of the first light shielding portion in relation to a second direction perpendicular to the first direction, which extends in a line form in the first direction, which is formed to have a line width in relation to the second direction narrower than a line width of the first light shielding portion, and which changes a phase of the light transmitted therethrough;

a first transmitting portion which is provided on the other side of the first light shielding portion in relation to the second direction, which extends in a line form in the first direction, which is formed to have a line width in relation to the second direction narrower than the line width of the first light shielding portion, and through which the light is transmitted; and

a second phase shift portion which is provided on a side of the first transmitting portion opposite to the first light shielding portion in relation to the second direction, which is formed to have a line width in relation to the second direction wider than the first transmitting portion, and which changes the phase of the light transmitted therethrough.

2. The focus test mask according to claim 1, wherein the line width of the first transmitting portion in the second direction is same as the line width of the first phase shift portion in the second direction.

3. The focus test mask according to claim 1, wherein the test pattern includes a second transmitting portion which is provided on a side of the first phase shift portion opposite to the first light shielding portion in relation to the second direction, which is formed to have a line width in relation to the second direction wider than the first phase shift portion, and through which the light is transmitted.

4. The focus test mask according to claim 3, wherein the line width of the second transmitting portion in the second direction is same as the line width of the second phase shift portion in the second direction.

5. The focus test mask according to claim 1, wherein the line width of the first light shielding portion in the second direction is at least four times the line width of the first phase shift portion in the second direction.

6. The focus test mask according to claim 3, wherein the line width of the first light shielding portion in the second direction is same as the line width of the second transmitting portion in the second direction and the line width of the second phase shift portion in the second direction.

7. The focus test mask according to claim 1, wherein an image, of the first light shielding portion, which is formed by the projection optical system has a line width in the second direction which is at least 200 nm.

8. The focus test mask according to claim 1, further comprising an auxiliary pattern which is provided to measure a positional deviation of an image of the test pattern.

9. The focus test mask according to claim 8, wherein the auxiliary pattern includes:

a second light shielding portion which extends in a line form in the first direction and which shields the light;

a third transmitting portion which is provided on one side of the second light shielding portion in relation to the second direction, which extends in a line form in the first direction, which is formed to have a line width in relation to the second direction narrower than a line width of the second light shielding portion, and through which the light is transmitted;

a third phase shift portion which is provided on the other side of the second light shielding portion in relation to the second direction, which extends in a line form in the first direction, which is formed to have a line width in relation to the second direction narrower than the line width of the second light shielding portion, and which changes the phase of the light transmitted therethrough; and

a fourth phase shift portion which is provided on a side of the third transmitting portion opposite to the second light shielding portion in relation to the second direction, which is formed to have a line width in relation to the second direction wider than the third transmitting portion, and which changes the phase of the light transmitted therethrough.

10. The focus test mask according to claim 9, wherein the test pattern includes a second transmitting portion which is provided on a side of the first phase shift portion opposite to the first light shielding portion in relation to the second direction, which is formed to have a line width in relation to the second direction wider than the first phase shift portion, and through which the light is transmitted;

and

the auxiliary pattern includes a fourth transmitting portion which is provided on a side of the third phase shift portion opposite to the second light shielding portion in relation to the second direction, which is formed to have a line width in relation to the second direction wider than the third phase shift portion, and through which the light is transmitted.

11. The focus test mask according to claim 10, further comprising a plurality of pattern groups which are composed of a plurality of pieces of the test pattern and a plurality of pieces of the auxiliary pattern;

wherein a first pattern group of the plurality of pattern groups is formed by arranging the test pattern and the auxiliary pattern, from one side in the second direction, in an order of the second transmitting portion, the first phase shift portion, the first light shielding portion, the first transmitting portion, the second phase shift portion, the fourth phase shift portion, the third transmitting portion, the second light shielding portion, the third phase shift portion, and the fourth transmitting portion.

12. The focus test mask according to claim 11, wherein the second phase shift portion also serves as the fourth phase shift portion.

13. The focus test mask according to claim 11, wherein a second pattern group of the plurality of pattern groups is formed by arranging the second transmitting portion, the first phase shift portion, the first light shielding portion, the first transmitting portion, the second phase shift portion, the fourth phase shift portion, the third transmitting portion, the second light shielding portion, the third phase shift portion, and the fourth transmitting portion in this order from the other side in the second direction.

14. The focus test mask according to claim 11, wherein a third pattern group of the plurality of pattern groups is formed by arranging the second transmitting portion, the first phase shift portion, the first light shielding portion, the first transmitting portion, the second phase shift portion, the fourth phase shift portion, the third transmitting portion, the second light shielding portion, the third phase shift portion, and the fourth transmitting portion in this order from one side in the first direction.

15. The focus test mask according to claim 11, wherein a fourth pattern group of the plurality of pattern groups is formed by arranging the second transmitting portion, the first phase shift portion, the first light shielding portion, the first transmitting portion, the second phase shift portion, the fourth phase shift portion, the third transmitting portion, the second light shielding portion, the third phase shift portion, and the fourth transmitting portion in this order from the other side in the first direction.

16. The focus test mask according to claim 1, wherein the test pattern is formed on a light-exiting surface of the focus test mask;

the first light shielding portion is formed to be higher than the first transmitting portion; and

the first and second phase shift portions are formed to be lower than the first transmitting portion.

17. A focus measuring method for measuring image plane information of a projection optical system, the focus measuring method comprising:

arranging the focus test mask as defined in claim 1 on a side of an object plane of the projection optical system;

projecting, onto a measuring surface, an image of the test pattern provided on the focus test mask, the image being formed by the projection optical system; and

measuring position information in a measuring direction of the image of the test pattern.

18. The focus measuring method according to claim 17, wherein the focus test mask includes an auxiliary pattern which is provided to measure a positional deviation of the image of the test pattern;

and

the position information in the measuring direction of the image of the test pattern includes a spacing distance in the measuring direction between the image of the test pattern and an image of the auxiliary pattern.

19. The focus measuring method according to claim 17, wherein the projecting the image of the test pattern formed by the projection optical system includes projecting the image onto a photosensitive substrate and developing the photosensitive substrate.

20. The focus measuring method according to claim 18, wherein the measuring the position information in the measuring direction of the image of the test pattern and the image of the auxiliary pattern includes measuring a light intensity distribution in the measuring direction of the image by using a spatial image measuring system.

21. An exposure method comprising:

arranging a mask for a device on a side of an object plane of a projection optical system;

adjusting a focus position of an image of a pattern of the mask for the device based on the position information of the image of the test pattern measured by using the focus measuring method as defined in claim 17, the image of the pattern of the mask for the device being formed by the projection optical system; and

projecting onto a substrate the image, of the pattern of the mask for the device, of which focus position has been adjusted.

22. An exposure apparatus which illuminates a pattern of a mask with an exposure light and exposes a substrate with the exposure light via the pattern and a projection optical system, the exposure apparatus comprising:

a mask stage which holds the focus test mask as defined in claim 1; and

a controller which causes the projection optical system to project an image of the test pattern of the focus test mask and which determines image plane information of the projection optical system based on position information in a measuring direction of the image of the test pattern.

23. The exposure apparatus according to claim 22, wherein the focus test mask is held in an area which is located closely to an area of the mask stage in which the mask is held.

24. The exposure apparatus according to claim 22, further comprising a spatial image measuring system which detects the image of the test pattern formed by the projection optical system.

25. A method for producing a device, the method comprising:

transferring a pattern onto a substrate by using the exposure apparatus as defined in claim 22; and

processing the substrate, onto which the pattern has been transferred, based on the pattern.