METHOD AND DEVICE FOR INSPECTING SPATIAL LIGHT MODULATOR, AND EXPOSURE METHOD AND DEVICE

• US 20140320835A1
• Filed: 08/30/2012
• Published: 10/30/2014
• Est. Priority Date: 09/02/2011
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Fujiwara, Tomoharu
• Granted Patent: US 10,317,346 B2
• Time in Patent Office: Days
• US Class Current: 355/67
• CPC Class Codes: G01B 11/24 for measuring contours or curvatures
• CPC Class Codes: G01B 11/255 for measuring radius of curvature measuring diameter G01B11/08
• CPC Class Codes: G01M 11/005 Testing of reflective surfaces, e.g. mirrors
• CPC Class Codes: G01N 2021/9511 Optical elements other than lenses, e.g. mirrors testing of optical apparatus in G01M11/00
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01N 21/95 characterised by the material or shape of the object to be examined G01N21/89 - G01N21/91, G01N21/94 take precedence
• CPC Class Codes: G02B 26/06 for controlling the phase of light G02B26/08 takes precedence , measuring optical phase difference G01J9/00
• CPC Class Codes: G02B 27/62 Optical apparatus specially adapted for adjusting optical elements during the assembly of optical systems
• CPC Class Codes: G02B 7/003 Alignment of optical elements G02B7/001, G02B7/002 take precedence; for mirrors G02B7/1822
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G03F 7/70291 Addressable masks, e.g. spatial light modulators [SLMs], digital micro-mirror devices [DMDs] or liquid crystal display [LCD] patterning devices
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: G06T 2207/10061 from scanning electron microscope
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

A method for inspecting a spatial light modulator includes: performing such control that in an inspection target area in an array of mirror elements, the mirror elements in a first state in which incident light is given a phase change amount of 0 and the mirror elements in a second state in which incident light is given a phase change amount of 180° (π) become arrayed in a checkered pattern; guiding light having passed the inspection target area to a projection optical system with a resolution limit coarser than a width of an image of one mirror element, to form a spatial image; and inspecting a characteristic of the spatial light modulator from the spatial image. This method allows us to readily perform the inspection of the characteristic of the spatial light modulator having the array of optical elements.

Claims

1. A method for inspecting a spatial light modulator having an array of optical elements to be illuminated with light, the method comprising:

performing such control that in at least a partial inspection target area in the array of optical elements, the optical elements in a first state which allow incident light to pass with a phase change of a first phase and the optical elements in a second state which allow incident light to pass with a phase change of a second phase 180°

different from the first phase become arrayed in a checkered pattern;

guiding light having passed the inspection target area to a projection optical system with a resolution limit coarser than a width of an image of one said optical element, to form a spatial image; and

inspecting a characteristic of the spatial light modulator from the spatial image formed by the projection optical system.

2. The method for inspecting the spatial light modulator according to claim 1, wherein for inspecting the characteristic of the spatial light modulator, an optical element with a defect in the inspection target area is specified from the spatial image formed by the projection optical system.

3. The method for inspecting the spatial light modulator according to claim 2, wherein for specifying the optical element with the defect, a position of an optical element corresponding to a portion where a light intensity is stronger than a predetermined threshold in the spatial image is obtained in the inspection target area.

4. The method for inspecting the spatial light modulator according to claim 2, comprising:

dividing the inspection target area into a first region and a second region each of which includes a plurality of said optical elements and which are adjacent in a first direction being an array direction of the optical elements; and

when the optical element with the defect is located in the first region, defining an optical element located away in the first direction from the optical element with the defect in the second region, as a substitute optical element for the optical element with the defect.

5. The method for inspecting the spatial light modulator according to claim 1, wherein for inspecting the characteristic of the spatial light modulator, distortion information of a reflective surface of the optical elements in the inspection target area is obtained from the spatial image formed by the projection optical system.

6. The method for inspecting the spatial light modulator according to claim 5, wherein a stress is applied to the inspection target area of the spatial light modulator, based on the distortion information of the reflective surface.

7. The method for inspecting the spatial light modulator according to claim 1, wherein for inspecting the characteristic of the spatial light modulator, an amount of stray light caused by the spatial light modulator is obtained from the spatial image formed by the projection optical system.

8. The method for inspecting the spatial light modulator according to claim 7, comprising:

dividing the inspection target area into a first illumination region and a second illumination region surrounding the first illumination region;

setting the optical elements in the first illumination region into the first state, and setting the second illumination region into a state in which the optical elements in the first state and the optical elements in the second state are arrayed in the checkered pattern;

forming an inspection spatial image via the projection optical system from the light having passed the inspection target area; and

obtaining flare information of the projection optical system from the spatial image and the inspection spatial image formed by the projection optical system.

9. The method for inspecting the spatial light modulator according to claim 1, wherein for inspecting the characteristic of the spatial light modulator, a variation of phase of light passing the optical elements of the spatial light modulator is obtained from a contrast of light intensity of the spatial image formed by the projection optical system.

10. The method for inspecting the spatial light modulator according to claim 1, wherein inspecting the characteristic of the spatial light modulator from the spatial image includes optically detecting the spatial image.

11. An exposure method for exposing a substrate with exposure light via a spatial light modulator having an array of optical elements and via a projection optical system, the exposure method comprising:

a step of performing an inspection of the spatial light modulator by the method for inspecting the spatial light modulator according to claim 1.

21. A device manufacturing method comprising:

forming a pattern of a photosensitive layer on a substrate, using the exposure method according to claim 11; and

processing the substrate with the pattern formed thereon.

23. The method for inspecting the spatial light modulator according to claim 3, comprising:

dividing the inspection target area into a first region and a second region each of which includes a plurality of said optical elements and which are adjacent in a first direction being an array direction of the optical elements; and

when the optical element with the defect is located in the first region, defining an optical element located away in the first direction from the optical element with the defect in the second region, as a substitute optical element for the optical element with the defect.

12. An apparatus for inspecting a spatial light modulator having an array of optical elements to be illuminated with light, the apparatus comprising:

an illumination apparatus which illuminates at least a partial inspection target area in the array of optical elements;

a control apparatus which performs such control that in the inspection target area, the optical elements in a first state which allow incident light to pass with a phase change of a first phase and the optical elements in a second state which allow incident light to pass with a phase change of a second phase 180°

different from the first phase become arrayed in a checkered pattern;

a projection optical system which forms a spatial image from light having passed the inspection target area and which has a resolution limit coarser than a width of an image of one said optical element; and

an arithmetic apparatus which performs an inspection of the spatial light modulator, based on the spatial image formed by the projection optical system.

13. The apparatus for inspecting the spatial light modulator according to claim 12, wherein the arithmetic apparatus specifies an optical element with a defect in the inspection target area.

14. The apparatus for inspecting the spatial light modulator according to claim 13, wherein the control apparatus operates as follows:

the control apparatus divides the inspection target area into a first region and a second region each of which includes a plurality of said optical elements and which are adjacent in a first direction being an array direction of the optical elements; and

when the optical element with the defect is located in the first region, the control apparatus defines an optical element located away in the first direction from the optical element with the defect in the second region, as a substitute optical element for the optical element with the defect.

15. The apparatus for inspecting the spatial light modulator according to claim 12, wherein the arithmetic apparatus obtains distortion information of a reflective surface of the optical elements in the inspection target area.

16. The apparatus for inspecting the spatial light modulator according to claim 12, wherein the arithmetic apparatus obtains an amount of stray light caused by the spatial light modulator.

17. The apparatus for inspecting the spatial light modulator according to claim 16,

wherein the control apparatus operates as follows:

the control apparatus divides the inspection target area into a first region and a second region surrounding the first region;

the control apparatus sets the optical elements in the first region into the first state, and sets the second region into a state in which the optical elements in the first state and the optical elements in the second state are arrayed in the checkered pattern; and

wherein the arithmetic apparatus obtains flare information of the projection optical system, based on an inspection spatial image formed via the projection optical system from light having passed the first region and the second region and based on the spatial image.

18. The apparatus for inspecting the spatial light modulator according to claim 12, wherein the arithmetic apparatus obtains a variation of phase of light passing the optical elements of the spatial light modulator from a contrast of light intensity of the spatial image formed by the projection optical system.

19. An exposure apparatus for exposing a substrate with exposure light from an illumination system via a projection system, the exposure apparatus comprising:

a spatial light modulator which is arranged on the object plane side of the projection system and which has an array of optical elements each of which can be controlled so as to guide the exposure light to the projection system; and

the apparatus for inspecting the spatial light modulator according to claim 12.

20. The exposure apparatus according to claim 19, wherein the illumination system also serves as at least a part of the illumination apparatus of the inspection apparatus, and

wherein the projection system also serves as the projection optical system of the inspection apparatus.

24. A device manufacturing method comprising:

forming a pattern of a photosensitive layer on a substrate, using the exposure apparatus according to claim 20; and

processing the substrate with the pattern formed thereon.

22. A device manufacturing method comprising:

forming a pattern of a photosensitive layer on a substrate, using the exposure apparatus according to claim; and

processing the substrate with the pattern formed thereon.