Subresolution grating for attenuated phase shifting mask fabrication

• US 6,042,973 A
• Filed: 08/09/1999
• Issued: 03/28/2000
• Est. Priority Date: 01/08/1998
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Pierrat, Christophe
• Primary Examiner(s): Rosasco, S.
• Application Number:
  US09/370,833
• Time in Patent Office: 232 Days
• Field of Search: 430/5, 430/322, 430/324, 430/311
• US Class Current: 430/5
• CPC Class Codes: G03F 1/26 Phase shift masks [PSM]; PSM blanks; Preparation thereof
• CPC Class Codes: G03F 1/32 Attenuating PSM [att-PSM], e.g. halftone PSM or PSM having semi-transparent phase shift portion,; Preparation thereof
• CPC Class Codes: G03F 7/001 Phase modulating patterns, e.g. refractive index patterns

Abstract

A subresolution grating composed of approximately circular contacts is fabricated around the border of the primary pattern of a photomask. As a result, resolution at the edges of the photomask pattern is improved when the pattern is printed on a wafer surface. In addition, the reduced leakage enables a more efficient use of the glass plate on which the photomask is fabricated as well as a more efficient use of the wafer surface as a result of being able to place patterns closer together.

Claims

1. A photomask produced by a method comprising:

preparing a glass plate;

transferring a primary pattern onto the glass plate, the primary pattern including an edge circumscribing the primary pattern; and

fabricating a plurality of approximately round contacts in the edge of the primary pattern.

2. The photomask of claim 1, wherein fabricating a plurality of approximately round contacts comprises forming octagonal contacts.

3. The photomask of claim 1, wherein transferring the primary pattern comprises selectively depositing attenuating material.

4. A photomask produced by a method comprising:

preparing a glass plate;

selectively depositing attenuating material on the glass plate to form a primary pattern, the primary pattern including an edge circumscribing the primary pattern; and

fabricating a plurality of octagonal contacts in the edge of the primary pattern.

5. A method of transferring a pattern to a wafer, comprising:

placing a photomask between an energy source and a semiconductor wafer, wherein the photomask includes a pattern such that a plurality of approximately round contacts are in an edge circumscribing the pattern; and

transferring an image of the pattern of the photomask on the semiconductor wafer through a controlled application of energy from the energy source.

6. The method of claim 5, wherein the plurality of approximately round contacts include octagonal contacts.

7. The method of claim 5, wherein the pattern includes attenuating material.

8. A subresolution grating, comprising:

an border outlining a primary pattern of a photomask; and

a plurality of approximately circular contacts in the border outlining the primary pattern.

9. The subresolution grating of claim 8, wherein the plurality of approximately circular contacts are octagonal.

10. The subresolution grating of claim 8, wherein the plurality of approximately circular contacts are subresolution in size.

11. A subresolution grating, comprising:

a border outlining a phase-shifting pattern, the border and the phase-shifting pattern formed with attenuating material; and

a plurality of approximately circular contacts in the border outlining the phase-shifting pattern.

12. The subresolution grating of claim 11, wherein the plurality of approximately circular contacts are octagonal.

13. A method of fabricating a photomask, comprising:

transferring a primary pattern onto a glass plate, the primary pattern including an edge circumscribing the primary pattern; and

fabricating a plurality of approximately round contacts in the edge of the primary pattern.

14. The method of claim 13, wherein fabricating a plurality of approximately round contacts comprises forming octagonal contacts.

15. The method of claim 13, wherein transferring the primary pattern comprises selectively depositing attenuating material.

16. A method of fabricating a photomask, comprising:

selectively depositing attenuating material on a glass plate to form a primary pattern, the primary pattern including an edge circumscribing the primary pattern; and

fabricating a plurality of octagonal contacts in the edge of the primary pattern.

17. A method of fabricating a photomask, comprising:

transferring a primary pattern onto a glass plate, the primary pattern including an edge circumscribing the primary pattern; and

fabricating a plurality of approximately round contacts in the edge of the primary pattern, such that adjacent contacts of the plurality of approximately round contacts are separated by a distance approximately equal to a diameter of one of the plurality of approximately round contacts.

18. The method of claim 17, wherein fabricating the plurality of approximately round contacts includes forming octagonal contacts.

19. The method of claim 17, wherein transferring the primary pattern comprises selectively depositing attenuating material.

20. A method of fabricating a photomask, comprising:

transferring a primary pattern onto a glass plate, the primary pattern including an edge circumscribing the primary pattern; and

fabricating a plurality of octagonal contacts in the edge of the primary pattern, such that adjacent contacts of the plurality of octagonal contacts are separated by a distance approximately equal to a width of one of the plurality of octagonal contacts.

21. The method of claim 20, wherein transferring the primary pattern comprises selectively depositing attenuating material.

22. A photomask, comprising:

a primary pattern;

a border outlining the primary pattern; and

a plurality of approximately circular contacts in the border outlining the primary pattern such that adjacent contacts of the plurality of approximately circular contacts are separated by a distance approximately equal to a diameter of one of the plurality of approximately circular contacts.

23. The photomask of claim 22, wherein the primary pattern and the border are composed of attenuating phase-shifting material.

24. The photomask of claim 23, wherein the plurality of approximately circular contacts are octagonal.

25. The photomask of claim 23, wherein the plurality of approximately circular contacts are subresolution in size.

26. A photomask, comprising:

a phase-shifting pattern formed with attenuating material, including a border circumscribing the phase-shifting pattern;

a plurality of approximately circular contacts formed in the border, such that adjacent contacts of the plurality of approximately circular contacts are separated by a distance approximately equal to a diameter of one of the plurality of approximately circular contacts.

27. The photomask of claim 26, wherein the plurality of approximately circular contacts are octagonal.