Method of soft x-ray imaging

• US 5,778,042 A
• Filed: 07/18/1996
• Issued: 07/07/1998
• Est. Priority Date: 07/18/1996
• Status: Expired due to Fees

• Current Assignee: University of Hawai'i
• Original Assignee: University of Hawai'i
• Inventors: Pong, William
• Primary Examiner(s): Church, Craig E.
• Application Number:
  US08/690,189
• Time in Patent Office: 719 Days
• Field of Search: 378/58, 378/35, 378/34
• US Class Current: 378/58
• CPC Class Codes: G01B 15/06 for measuring the deformation in a solid
• CPC Class Codes: G03F 1/22 Masks or mask blanks for imaging by radiation of 100nm or shorter wavelength, e.g. X-ray masks, extreme ultraviolet [EUV] masks; Preparation thereof
• CPC Class Codes: G03F 1/84 Inspecting

Abstract

A method for inspecting masks used in x-ray lithography is described. An x-ray lithography mask is placed over a glass surface, followed by exposure of the mask and glass surface to soft x-rays. Portions of the mask absorb the soft x-rays while other portions of the mask, corresponding to circuit elements, allow the soft x-rays to strike the glass surface. The soft x-rays striking the glass surface cause the glass surface to darken, thereby forming an image of the circuit pattern in the glass surface corresponding to the stenciled circuit in the mask. An inspection of the image can reveal any defects in the x-ray lithography mask.

Claims

1. A method of forming an image on a glass surface using soft x-rays, comprising the steps of:

a. providing a source of soft x rays, a mask and a glass surface;

b. positioning said mask between said glass surface and said source of soft x-rays; and

c. exposing said glass surface to soft x-rays from said source of soft x-rays, whereby said mask blocks a portion of said soft x-rays and an image is formed on said glass surface, said image corresponding to areas on said glass surface exposed to said soft x-rays.

2. The method of claim 1 wherein said glass comprises sodium.

3. The method of claim 1 wherein said source of soft x-rays is a synchrotron.

4. The method of claim 1 wherein said source of soft x-rays is an x-ray tube.

5. A method of forming an image on a glass surface using soft x-rays, comprising the steps of:

a. providing a source of soft x rays, a mask and a glass surface;

b. positioning said mask between said glass surface and said source of soft x-ras;

c. exposing said glass surface to soft x-rays from said source of soft x-rays, whereby said mask blocks a portion of said soft x-rays and areas on said glass surface exposed to said soft x-rays discolor and other areas do not discolor;

d. applying a thin film of a photoelectron-emitting material to said glass surface; and

e. projecting a blue light from behind said glass surface through said photoelectron-emitting material in order to cause electron emissions from portions of said photon-emitting material.

6. The method of claim 5 wherein said photoelectron-emitting material is cesium.

7. The method of claim 5 wherein said photoelectron-emitting material is potassium.

8. A method for inspecting a semiconductor mask, comprising the steps of:

a. providing a source of soft x-rays, a glass surface, and a semiconductor mask for creating integrated circuits;

b. positioning said semiconductor mask in contact with said glass surface;

c. positioning said source of soft x-rays so that said semiconductor mask is between said glass surface and said source of soft x-rays;

d. irradiating said glass surface with soft x-rays from said source of soft x-rays whereby said semiconductor mask blocks a portion of said soft x-rays from striking said glass surface so that regions of said glass surface exposed to said soft x-rays discolor while regions of said glass surface not exposed to said soft x-rays do not discolor; and

e. inspecting said discoloration on said glass surface for defects which correspond to defects in said semiconductor mask.

9. The method of claim 8, wherein said glass comprises sodium.

10. The method of claim 8, wherein said source of soft x-rays is a synchrotron.

11. The method of claim 8, wherein said source of soft x-rays is an x-ray tube.