Use of attenuating phase-shifting mask for improved printability of clear-field patterns

• US 6,255,024 B1
• Filed: 03/30/2000
• Issued: 07/03/2001
• Est. Priority Date: 12/30/1997
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Pierrat, Christophe
• Primary Examiner(s): ROSASCO, STEPHEN D
• Application Number:
  US09/539,084
• Time in Patent Office: 460 Days
• Field of Search: 430/5, 430/322, 250/237.R, 250/492.2, 250/492.22, 359/888
• US Class Current: 430/5
• CPC Class Codes: G03F 1/32 Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof

Abstract

An improved photolithographic method employs a pattern of subresolution openings to enhance the printability of clear-field patterns. Incorporating a subresolution opening along the edges of the transmission areas prevents the printing of side lobe light and enables incorporation of a positive bias in the clear-field pattern. This is turn increases the lithographic process latitudes. The photomask must be significantly overexposed as a result of using a positive bias. To compensate for the impact of increased exposure on large transmission areas and avoid degradation of the corresponding resist, a pattern of subresolution openings is incorporated in the large transmission areas. The size and orientation of the subresolution areas creates a diffraction grating effect, reducing the exposure of the area under each transmission area.

Claims

1. A photolithographic method comprising:

illuminating a photomask that includes one or more transmission areas intermingled with one or more transparent areas, including;

illuminating amplitude-attenuating, phase-shifting material on the photomask in the one or more transmission areas; and

illuminating a plurality of subresolution openings in the one or more transmission areas.

2. The method of claim 1, wherein illuminating a photomask that includes one or more transmission areas further comprises illuminating a clear-field pattern on the photomask.

3. The method of claim 2, wherein illuminating the photomask includes positively biasing the one or more transmission areas on the photomask.

4. The method of claim 1, wherein illuminating the photomask includes illuminating openings parallel to and inside each edge of the one or more transmission areas.

5. The method of claim 1, wherein illuminating the photomask includes illuminating a grid of regularly spaced openings in the plurality of subresolution openings.

6. A semiconductor wafer manufactured using a process that includes the photolithographic method of claim 1.

7. A semiconductor die manufactured using a process that includes the photolithographic method of claim 1.

8. The method of claim 1, wherein illuminating the photomask includes over-exposing the photomask.

9. The method of claim 8, wherein illuminating the photomask includes positively-biasing a clear-field photomask.

10. The method of claim 1, wherein illuminating the photomask includes diffracting the light transmitted through the amplitude-attenuating, phase-shifting material and the plurality of subresolution openings such that side lobe illumination is reduced.

11. A method of directing light to a wafer through a photomask comprising:

illuminating one or more transmission areas intermingled with one or more transparent areas on a photomask, including;

illuminating amplitude-attenuating phase-shifting material on the photomask in the one or more transmission areas;

illuminating a plurality of subresolution openings in the attenuating phase-shifting material parallel to and inside each edge of the one or more transmission areas; and

illuminating a grid of subresolution openings within a plurality of the one or more transmission areas.

12. A semiconductor wafer manufactured using a process that includes the method of claim 11.

13. A semiconductor die manufactured using a process that includes the method of claim 11.

14. The method of claim 11, wherein illuminating the one or more transmission areas includes over-exposing the wafer.

15. The method of claim 14, wherein illuminating the one or more transmission areas includes positively-biasing a clear-field photomask.

16. The method of claim 11, wherein illuminating the one or more transmission areas includes diffracting the light transmitted through the amplitude-attenuating, phase-shifting material and the plurality of subresolution openings such that side lobe illumination is reduced.

17. The method of claim 16, wherein diffracting the light includes preventing trench formation in the area of the wafer aligned with one of the amplitude-attenuating, phase-shifting material and the plurality of subresolution openings.

18. The method according to claim 11, wherein illuminating amplitude-attenuated, phase-shifted material includes phase-shifting the light about 180 degrees.

19. A photolithographic method comprising:

illuminating a wafer through a photomask having a pattern of amplitude-attenuating material on a transparent plate, the pattern including;

one or more transparent areas; and

one or more transmission areas intermingled with the one or more transparent areas, one or more of each of the one or more transmission areas including a pattern of subresolution openings.

20. The photolithographic method of claim 19, wherein the pattern of attenuating material is a clear-field pattern.

21. The photolithographic method of claim 20, wherein the transmission areas are positively biased.

22. The photolithographic method of claim 21, wherein the pattern of subresolution openings comprises subresolution openings parallel to each edge of the one or more transmission areas.

23. The photolithographic method of claim 21, wherein the pattern of subresolution openings further comprises a grid of regularly spaced openings.

24. A semiconductor wafer manufactured using a process that includes the photolithographic method of claim 19.

25. A semiconductor die manufactured using a process that includes the photolithographic method of claim 19.

26. A method of illuminating resist on a wafer, comprising:

illuminating a positively biased clear-field pattern of amplitude-attenuating material on a transparent plate positioned in front of the wafer, the pattern including;

one or more transparent areas; and

one or more transmission areas intermingled with one or more transparent areas, the one or more transmission areas including;

a pattern of subresolution openings parallel to and inside each edge of the one or more transmission areas; and

a pattern of subresolution openings comprising a grid of regularly spaced openings.

27. A semiconductor wafer manufactured using a process that includes the method of claim 26.

28. A semiconductor die manufactured using a process that includes the method of claim 26.

29. A photolithographic method comprising:

illuminating a photomask that includes one or more transmission areas intermingled with one or more transparent areas, including;

illuminating a lightly transmissive absorbent, phase-shifting material on the photomask in the one or more transmission areas; and

illuminating a plurality of subresolution openings in the one or more transmission areas.

30. The method of claim 29, wherein illuminating the lightly transmissive absorbent, phase-shifting material includes attenuating and phase-shifting the illumination passed through the lightly transmissive absorbent, phase-shifting material.