METHOD AND APPARATUS FOR TESTING A PHOTOMASK

• US 20060190196A1
• Filed: 02/24/2005
• Published: 08/24/2006
• Est. Priority Date: 02/24/2005
• Status: Active Grant

• Current Assignee: GlobalFoundries, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Rankin, Jed H.
• Granted Patent: US 7,914,949 B2
• Time in Patent Office: Days
• US Class Current: 702/42
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects

Abstract

A method, a recording medium and an apparatus for testing a photomask are provided. In the disclosed method, a particular region of a photomask is selected, either from a physical instance of the photomask, or from the photomask as represented by a digital representation thereof. The particular region is then characterized by identifying a pattern type present in the particular region. A lithographic process stress condition is determined for the particular region, considering the pattern type, and thereafter, a result of lithographically patterning a feature is determined by simulating a photolithographic exposure, using the particular region of the photomask under the lithographic process stress condition. Then, it is decided whether the particular region of the photomask is acceptable based on the result of the simulated exposure only under the lithographic process stress condition.

Claims

1. A method of testing a photomask, comprising:

a) selecting a particular region of a photomask;

b) identifying a pattern type present in the particular region to characterize the particular region;

c) determining a lithographic process stress condition for the particular region, in consideration of the pattern type;

d) determining a result of lithographically patterning a feature by simulating a photolithographic exposure using the particular region of the photomask under the lithographic process stress condition; and

e) deciding whether particular region of the photomask is acceptable based on the result of the simulated exposure only under the lithographic process stress condition.

2. The method as claimed in claim 1, wherein the lithographic process stress condition is defined by setting a condition of the photolithographic exposure to a process tolerance limit.

3. The method as claimed in claim 2, wherein the condition of the photolithographic exposure includes at least one of a focus, a dose, a mask height, a resist thickness, and a lens aberration.

4. The method as claimed in claim 1, further comprising selecting another region of the photomask as the particular region and repeating steps b), c) and d) until results of patterning with all regions of the photomask have been determined and deciding whether the photomask is acceptable based on the results of patterning with all regions of the photomask.

5. The method as claimed in claim 1, wherein the lithographic process stress condition is determined by using the identified pattern type to reference a table.

6. The method as claimed in claim 1, wherein the lithographic process stress condition is a worst case process condition for the identified pattern type.

7. The method as claimed in claim 1, wherein the lithographic exposure is simulated using inspection data obtained by imaging the mask.

8. The method as claimed in claim 7, wherein the inspection data includes data selected from the group consisting of actinic and non-actinic inspection data.

9. A machine-readable recording medium having recorded thereon information recorded thereon for performing a method of testing a photomask, the method as claimed in claim 1.

10. A method of testing a digital representation of a photomask usable to construct a physical instance of the photomask, comprising:

a) selecting a particular region of the photomask as represented by the digital representation;

b) identifying a pattern type present in the particular region to characterize the particular region;

c) determining a lithographic process stress condition for the particular region, considering the pattern type;

d) determining a result of lithographically patterning a feature by simulating a photolithographic exposure using the particular region of the photomask under the lithographic process stress condition; and

e) deciding whether the particular region of the photomask is acceptable based on the result of the simulated exposure only under the lithographic process stress condition.

17. A machine-readable recording medium having information recorded thereon for performing a method of testing a photomask, the method as claimed in claim 10.

11. The method as claimed in 10, wherein the digital representation has not been corrected for optical proximity prior to simulating the lithographic exposure.

12. The method as claimed in 10, wherein the digital representation has been corrected for optical proximity prior to simulating the lithographic exposure.

13. The method as claimed in claim 12, wherein, when by the determining step d) the feature is not acceptably patterned, performing the steps of f) incrementally improving the lithographic process stress condition, g) determining a result of lithographically patterning the feature under the improved lithographic process condition, and h) determining whether that result is acceptable.

14. The method as claimed in claim 13, further comprising repeating the steps f), g) and h) until the feature is acceptably patterned.

15. The method as claimed in claim 14, further comprising i) recording the last improved lithographic stress condition until the feature is acceptably patterned.

16. The method as claimed in claim 15, further comprising using the results of patterning in accordance with all regions of the mask to report an overall process window for the mask.

18. An apparatus for performing a method of testing a photomask, the apparatus including a processor, the processor being operable to a) select a particular region of a photomask;

b) identify a pattern type present in the particular region to characterize the particular region;

c) determine a lithographic process stress condition for the particular region in consideration of the pattern type;

d) determine a result of lithographically patterning a feature by simulating a photolithographic exposure using the particular region of the photomask under the lithographic process stress condition; and

e) determine whether the particular region of the photomask is acceptable based on the result of the simulated exposure only under the lithographic process stress condition.