Multi-layer X-ray-reflecting mirrors with reduced internal stress

• US 6,160,867 A
• Filed: 07/14/1998
• Issued: 12/12/2000
• Est. Priority Date: 07/17/1997
• Status: Expired due to Fees

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Murakami, Katsuhiko
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): Ho, Allen C
• Application Number:
  US09/115,567
• Time in Patent Office: 882 Days
• Field of Search: 378/84, 378/85, 378/145
• US Class Current: 378/84
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: G02B 5/0891 Ultraviolet [UV] mirrors apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06
• CPC Class Codes: G21K 1/062 Devices having a multilayer structure

Abstract

X-ray-reflecting mirrors are disclosed that exhibit reduced internal stress without any significant reduction in reflectance to X-rays. The mirrors comprise a substrate on a surface of which a multi-layer structure is formed. The multi-layer structure is formed by alternately and superposedly layering, on a surface of the substrate, a first material (e.g., molybdenum) and a second material (silicon with a dopant such as boron). Net internal stress of the multi-layer structure is controllably reduced by controlling the amount of diffused dopant in the second material.

Claims

1. A mirror for reflecting X-rays, comprising:

a substrate having a surface; and

multiple alternating layers of a first material and a second material applied superposedly to the surface of the substrate to form a multi-layer structure on the substrate, the first material consisting essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances, and the second material consisting essentially of silicon and a dopant selected from a group consisting of B, C, and P, the dopant being at a concentration sufficient to reduce net internal stress in the multi-layer structure compared to an otherwise similar multi-layer structure lacking the dopant in the second material.

4. The mirror of claim 1, wherein the substrate is glass.

5. The mirror of claim 1, comprising at least 50 layers of each of the first and second materials.

6. The mirror of claim 1, comprising 30 to 100 layers.

7. The mirror of claim 1, wherein the first material is Mo, and the second material is B-doped Si.

8. The mirror of claim 1, wherein the layer contacting the surface of the substrate is a layer of the first material.

2. A mirror for reflecting X-rays, comprising:

a substrate having a surface; and

multiple alternating layers of a first material and a second material applied superposedly to the surface of the substrate to form a multi-layer structure on the substrate, the first material consisting essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances, and the second material consisting essentially of silicon and a dopant selected from a group consisting of B, C, and P, the dopant being at a concentration of at least 1×

10⁸ atoms/cm³ to reduce net internal stress in the multi-layer structure compared to an otherwise similar multi-layer structure lacking the dopant in the second material.

3. A mirror for reflecting X-rays, comprising:

a substrate having a surface; and

multiple alternating layers of a first material and a second material applied superposedly to the surface of the substrate to form a multi-layer structure on the substrate, the first material consisting essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances, and the second material consisting essentially of silicon and a dopant selected from a group consisting of B, C, and P, wherein the dopant is B at a concentration of at least 1×

10¹⁸ atoms/cm³ that is sufficient to reduce net internal stress in the multi-layer structure compared to an otherwise similar multi-layer structure lacking the dopant in the second material.

9. A mirror for reflecting X-rays, comprising:

a substrate having a surface; and

multiple alternating layers of a first material and a second material applied superposedly to the surface of the substrate to form a multi-layer structure on the substrate, the first material consisting essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances, and the second material consisting essentially of silicon and a dopant selected from a group consisting of B, C, and P, the dopant being at a concentration sufficient to reduce net internal stress in the multi-layer structure compared to an otherwise similar multi-layer structure lacking the dopant in the second material, wherein the layer contacting the surface of the substrate is a layer of the second material.

10. A method for making a mirror that is reflective to X-rays, the method comprising:

(a) providing a rigid substrate having a surface;

(b) applying to the surface a laminar structure consisting of a layer of a first material and a layer of a second material, the first material consisting essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances, and the second material consisting essentially of Si and a dopant selected from a group consisting of B, C, and P, the dopant being at a concentration of at least 0.001 atomic percent relative to the silicon;

(c) superposedly applying at least one additional layer of the first material and of the second material in alternating order superposedly to the laminar structure formed in step (b) to form a multi-layer mirror structure.

11. The method of claim 10, wherein, in step (b), a layer of the first material contacts the substrate surface.

12. The method of claim 10, wherein, in step (b), a layer of the second material contacts the substrate surface.

13. The method of claim 10, wherein the dopant in the second material is at a concentration of at least 1×

10¹⁸ atoms/cm³.

14. The method of claim 13, wherein the dopant is B.

15. The method of claim 10, wherein the first material consists essentially of Mo, and the dopant is B.

16. The method of claim 10, wherein step (a) comprises providing a glass substrate, and providing the surface with a mirror-polish.

17. The method of claim 10, wherein step (c) comprises applying at least 50 layers of each of the first material and of the second material.

18. The method of claim 10, wherein a total of 30 to 100 layers is applied to the substrate.

19. The method of claim 10, wherein steps (b)-(c) are performed by sputtering.

20. A mirror manufactured according to the method of claim 10.

21. A mirror for reflecting X-rays, comprising:

a substrate having a surface; and

multiple alternating layers of a first material and a second material applied superposedly to the surface of the substrate to form a multi-layer structure on the substrate, the first material consisting essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances, and the second material consisting essentially of silicon and a dopant selected from a group consisting of B, C, and P, the dopant being at a concentration sufficient to reduce surface warping compared to an otherwise similar multi-layer structure lacking the dopant in the second material.