MULTI-EXPOSURE LITHOGRAPHY EMPLOYING DIFFERENTIALLY SENSITIVE PHOTORESIST LAYERS

• US 20090311491A1
• Filed: 06/16/2008
• Published: 12/17/2009
• Est. Priority Date: 06/16/2008
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Wang, Ping-Chuan, Huang, Wu-Song, Li, Wai-kin
• Granted Patent: US 8,158,014 B2
• Time in Patent Office: Days
• US Class Current: 428/195.100
• CPC Class Codes: G03F 7/70466 Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature stitching G03F7/70475
• CPC Class Codes: Y10S 438/947 Subphotolithographic processing
• CPC Class Codes: Y10S 438/948 Radiation resist
• CPC Class Codes: Y10T 428/24802 Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.]

Abstract

A stack of a second photoresist having a second photosensitivity and a first photoresist having a first photosensitivity, which is greater than second photosensitivity, is formed on a substrate. A first pattern is formed in the first photoresist by a first exposure and a first development, while the second photoresist underneath remains intact. A second pattern comprising an array of lines is formed in the second photoresist. An exposed portion of the second photoresist underneath a remaining portion of the first photoresist forms a narrow portion of a line pattern, while an exposed portion of the second photoresist outside the area of the remaining portions of the photoresist forms a wide portion of the line pattern. Each wide portion of the line pattern forms a bulge in the second pattern, which increases overlay tolerance between the second pattern and the pattern of conductive vias.

Claims

1. A method of forming a patterned structure comprising:

forming a stack of, from bottom to top, a second photoresist and a first photoresist on a substrate;

lithographically patterning said first photoresist with a first pattern, wherein a top surface of said second photoresist is exposed in an area of said first pattern; and

lithographically forming a second pattern in said second photoresist, wherein said second pattern includes a plurality of line troughs, wherein each of said plurality of line troughs includes a narrow portion having a first width, and wherein at least one of said plurality of line troughs includes a bulge portion having a second width greater than said first width, wherein said bulge portion is formed underneath said area of said first pattern.

2. The method of claim 1, wherein said second photoresist has a second photosensitivity and said first photoresist has a first photosensitivity, and wherein said first photosensitivity is greater than said second photosensitivity.

3. The method of claim 2, wherein said first photoresist is a positive photoresist that becomes chemically less stable upon exposure.

4. The method of claim 3, wherein said second photoresist is another positive photoresist that becomes chemically less stable upon exposure.

5. The method of claim 2, wherein said first photoresist comprises a grey resist.

6. The method of claim 2, wherein said first photoresist comprises a first photosensitive chemical and said second photoresist comprises a second photosensitive chemical, wherein said first photosensitive chemical has greater photosensitivity than said second photosensitive chemical.

7. The method of claim 1, wherein said second pattern is formed by simultaneously lithographically exposing said first photoresist having said first pattern and said second photoresist with a light exposure pattern generated by a lithographic mask containing a pattern of a set of parallel lines of a constant width.

8. The method of claim 7, wherein said light exposure pattern has a modulation of light intensity in a direction perpendicular to said set of parallel lines, wherein light intensity is non-zero throughout an exposure field.

9. The method of claim 8, wherein an entirety of said first photoresist having said first pattern is exposed, while exposed portions of said second photoresist forms said second pattern.

10. The method of claim 9, further comprising developing and removing said entirety of said first photoresist having said first pattern.

11. The method of claim 1, wherein said first width is a lithographic width of a lithography tool employed to expose said first photoresist with said first pattern and said second photoresist.

12. The method of claim 11, wherein a first narrow portion in one of said plurality of line troughs and a second narrow portion in a neighboring line trough of said plurality of line troughs are separated by a lithographic spacing of a lithography tool employed to expose said first photoresist with said first pattern and said second photoresist.

13. The method of claim 12, wherein said first narrow portion is separated from a bulge portion in said neighboring line trough by a separation distance equal to a sum of said lithographic width and said lithographic spacing less said second width.

14. The method of claim 13, wherein said separation distance is a sublithographic dimension.

15. The method of claim 12, wherein said lithographic width is a minimum lithographic width and said lithographic spacing is a minimum lithographic spacing.

16. The method of claim 1, further comprising:

transferring said second pattern into said substrate by etch, wherein said second pattern is replicated in an upper surface of said substrate; and

forming a plurality of conductive lines embedded in said substrate, wherein each of said plurality of conductive lines includes a narrow conductive portion having a third width, and wherein at least one of said plurality of conductive lines includes a conductive bulge portion having a fourth width greater than said third width.

17. The method of claim 16, wherein said third width is substantially the same as said first width, and wherein said fourth width is substantially the same as said third width.

18. The method of claim 1, further comprising forming an anti-reflective coating (ARC) layer directly on said substrate, wherein said second photoresist is formed directly on said ARC layer, wherein said ARC layer is not photosensitive.

19. A patterned structure comprising:

at least one exposed second photoresist portion located on a substrate and laterally abutted by at least one second photoresist portion, wherein said at least one second photoresist portion comprises a second unexposed photosensitive material and said at least one exposed second photoresist portion comprises a second exposed photosensitive material, wherein said second exposed photoresist material is a material derived from said second unexposed photoresist material by lithographic exposure; and

at least one exposed first photoresist portion located directly on said at least one exposed second photoresist portion and said at least one second photoresist portion and comprising a first exposed photosensitive material.

20. The patterned structure of claim 19, wherein said first exposed photoresist material is a material derived from a first unexposed photoresist material by lithographic exposure, and wherein said first unexposed photoresist material has a first photosensitivity and said second unexposed photosensitive material has a second photosensitivity, and wherein said first photosensitivity is greater than said second photosensitivity.

21. The patterned structure of claim 20, wherein said first unexposed photoresist material is a positive photoresist that becomes chemically less stable upon exposure, and wherein said second unexposed photoresist material is another positive photoresist that becomes chemically less stable upon exposure.

22. The patterned structure of claim 19, wherein a portion of said at least one exposed second photoresist portion does not underlie said at least one exposed first photoresist portion, and a portion of said at least one second photoresist portion does not underlie said at least one exposed first photoresist portion.

23. The patterned structure of claim 19, wherein said at least one exposed second photoresist portion comprises a plurality of exposed second photoresist lines in a first one-dimensional array, and wherein said at least one second photoresist portion comprises a plurality of unexposed second photoresist lines in a second one-dimensional array.

24. The patterned structure of claim 23, wherein each of said plurality of exposed second photoresist lines comprises at least one narrow exposed second photoresist line portion having a first width and underlying said at least one second photoresist portion and at least one wide exposed second photoresist line portion having a second width and not underlying said at least one second photoresist portion, wherein said second width is greater than said first width.

25. The patterned structure of claim 19, wherein said at least one exposed first photoresist portion comprises a plurality of exposed first photoresist lines in a one-dimensional array, wherein each of said plurality of exposed first photoresist lines has a constant width and a constant spacing from a neighboring exposed first photoresist line.