Method of and device for planarizing a surface of a semiconductor wafer

• US 6,010,828 A
• Filed: 02/19/1998
• Issued: 01/04/2000
• Est. Priority Date: 02/19/1998
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Lippitt, Maxwell W.
• Primary Examiner(s): Gibson, Sharon
• Assistant Examiner(s): Holloman, Jill N.
• Application Number:
  US09/026,447
• Time in Patent Office: 684 Days
• Field of Search: 430/269, 430/313, 430/323, 430/322, 430/396, 430/945
• US Class Current: 430/313
• CPC Class Codes: G03F 7/168 Finishing the coated layer, e.g. drying, baking, soaking
• CPC Class Codes: G03F 7/2026 for the removal of unwanted material, e.g. image or background correction
• CPC Class Codes: H01L 21/31055 the removal being a chemical etching step, e.g. dry etching etching per se H01L21/311

Abstract

The present invention provides a method of and a device for planarizing a photosensitive material, such as a photoresist, located over an irregular surface of a semiconductor wafer. In one embodiment, the method comprises the steps of passing radiation through a first medium and a second medium wherein the first medium is interfaced with the second medium. The method further comprises the steps of passing the radiation from the second medium into the photosensitive material that is interfaced with the second medium to expose the photosensitive material. The first and second mediums and the photosensitive material have radiation absorption coefficients such that the radiation terminates substantially within a plane of the photosensitive material. The method further includes the step of etching the exposed photosensitive material to the plane.

Claims

1. A method of planarizing a photosensitive layer located over an irregular surface of a semiconductor wafer, comprising:

passing radiation through a first medium and a second medium, said first medium interfaced with second medium;

passing said radiation from said second medium into said photosensitive layer interfaced with said second medium to uniformly expose said photosensitive layer, said first and second mediums and said photosensitive layer having radiation absorption coefficients such that said radiation terminates substantially within a plane of said photosensitive layer; and

etching said photosensitive material to said plane, whereby said photosensitive layer is substantially planarized at said plane.

2. The method as recited in claim 1 wherein passing said radiation through said first medium includes passing said radiation through a transparent glass plate positioned over said semiconductor surface, said transparent glass plate forming a substantially flat interface with said second medium.

3. The method as recited in claim 1 wherein passing said radiation through said second medium includes passing said radiation through a fluid medium.

4. The method as recited in claim 3 wherein said fluid medium is water or gas.

5. The method as recited in claim 1 wherein said first and second mediums and said photosensitive layer have substantially equal refractive indices.

6. The method as recited in claim 1 wherein passing radiation includes passing laser radiation through said first and second medium and into said photosensitive layer.

7. The method as recited in claim 1 further comprising positioning said semiconductor wafer substantially parallel to said first medium.

8. The method as recited in claim 1 further comprising positioning said photosensitive layer a predetermined distance from said first medium, said predetermined distance being a function of an absorption rate of said photosensitive layer.

9. The method as recited in claim 1 wherein said photosensitive layer is a photoresist.

10. The method as recited in claim 1 wherein said second medium conforms to a surface of said photosensitive layer.

11. The method as recited in claim 1 further comprising etching into said irregular surface to planarize said irregular surface.

12. A method for planarizing a photosensitive material located over an irregular surface of a semiconductor wafer, comprising:

positioning a first medium and a second medium substantially parallel to said semiconductor wafer, said second medium interfaced with said first medium;

positioning a photosensitive layer on said semiconductor wafer a predetermined distance from said first medium, said predetermined distance being a function of an absorption rate of said photosensitive material;

passing radiation through said first and second mediums and into said photosensitive layer to uniformly expose said photosensitive layer, said first and second mediums and said photosensitive layer having radiation absorption coefficients such that said radiation terminates substantially within a plane of said photosensitive layer; and

etching said photosensitive layer to said plane, whereby said photosensitive layer is substantially planarized at said plane.

13. The method as recited in claim 12 wherein passing radiation through said first and second mediums includes passing laser radiation through first and second mediums wherein said first medium is a transparent glass plate and said second medium is a fluid.

14. The method as recited in claim 13 wherein passing laser radiation includes passing radiation through said first medium wherein said first medium has a refractive index between 1.1 and 1.3 and a radiation absorption coefficient in the range of 5-20% and said second fluid medium has a refractive index substantially equal to said first medium.