Inspection technique of photomask

• US 6,091,845 A
• Filed: 02/24/1998
• Issued: 07/18/2000
• Est. Priority Date: 02/24/1998
• Status: Expired due to Term

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Pierrat, Christophe, Burdorf, James
• Primary Examiner(s): Boudreau, H.
• Assistant Examiner(s): Werner, Brian P.
• Application Number:
  US09/028,878
• Time in Patent Office: 875 Days
• Field of Search: 382/144, 382/145, 382/149, 382/151, 382/257, 382/266, 382/285, 356/384, 356/390, 356/394, 356/237.4, 356/237.5, 348/87, 348/126, 348/129, 348/130, 438/16, 250/559.04, 250/559.05, 250/559.06, 250/559.07, 250/559.08, 250/559.2, 250/559.39, 250/559.45, 250/559.46, 703/13, 703/14, 716/19, 716/21
• US Class Current: 382/144
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G03F 1/84 Inspecting
• CPC Class Codes: G03F 7/70483 Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0006 using a design-rule based approach

Abstract

An improved technique for inspecting photomasks employs simulated images of the resist pattern. A simulated image of an original pattern is compared to a simulated image generated from a pattern captured from a photomask manufactured from the original pattern. Alternatively, simulated images generated from captured data from two different instances of the same original pattern formed in a photomask are compared.

Claims

1. A method of inspecting a mask, comprising:

acquiring mask image data from the mask;

modifying the acquired mask image data according to characteristics of resist material at different deposition elevations and producing therefrom acquired mask elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired mask image data;

applying a second elevation to an unmasked area of the acquired mask image data; and

interpolating an edge between the mask area and the unmask area of the acquired mask image data at the first common elevation;

generating a first image simulation of the acquired mask elevation image data;

acquiring image pattern data from a pattern used for forming the mask;

generating a second image simulation of the acquired image pattern data; and

comparing the first and second image simulations for a defect.

2. The method of claim 1, wherein the first and second image simulations are two-dimensional.

3. The method of claim 1, wherein the first and second image simulations are three-dimensional.

4. The method of claim 1, wherein at least generating a first image simulation and generating a second image simulation is performed off-line.

5. A method of inspecting a mask, comprising:

acquiring mask image data from the mask;

generating a first image simulation of the acquired mask image data;

acquiring pattern image data from a pattern used for forming the mask;

modifying the acquired pattern image data according to characteristics of resist material at different deposition elevations and producing therefrom acquired pattern elevation data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired pattern image data;

applying a second common elevation to an unmasked area of the acquired pattern image data; and

interpolating an edge between the mask area and the unmasked area of the acquired pattern image data at the first common elevation;

generating a second image simulation of the acquired pattern elevation image data; and

comparing the first and second image simulations for a defect.

6. The method of claim 5, wherein the first and second image simulations are two-dimensional.

7. The method of claim 5, wherein the first and second image simulations are three-dimensional.

8. The method of claim 5, wherein at least generating a first image simulation and generating a second image simulation is performed off-line.

9. A method of inspecting a mask, comprising:

acquiring image data of a first pattern from the mask;

modifying the image data of the first pattern according to characteristics of resist material at different deposition elevations and producing therefrom acquired first pattern elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired image data from the first pattern;

applying a second common elevation to an unmasked area of the acquired image data from the first pattern; and

interpolating an edge between the mask area and the unmasked area of the acquired image data from the first pattern of the mask at the first common elevation;

generating a first image simulation of the acquired first pattern elevation image data;

acquiring image data of a second pattern from the mask;

generating a second image simulation of the acquired image data from the second pattern; and

comparing the first and second image simulations for a defect.

10. A method of inspecting a mask, comprising:

acquiring image data of a first pattern from the mask;

generating a first image simulation of the acquired image data from the first pattern;

acquiring image data of a second pattern from the mask;

modifying the acquired image data of the second pattern according to characteristics of resist material at different deposition elevations and producing therefrom acquired second pattern elevation data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired image data from the second pattern;

applying a second common elevation to an unmasked area of the acquired image data from the second pattern; and

interpolating an edge between the mask area and the unmasked area of the acquired image data from the second pattern of the mask at the first common elevation;

generating a second image simulation of the acquired second pattern elevation image data; and

comparing the first and second image simulations for a defect.

11. A computer readable medium on a computer, the computer readable medium having computer executable instructions for performing a method comprising:

acquiring mask image data from a mask;

modifying the acquired mask image data according to characteristics of resist material at different deposition elevations and producing therefrom acquired mask elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired mask image data;

applying a second common elevation to an unmasked area of the acquired mask image data; and

interpolating an edge between the mask area and the unmasked area of the acquired mask image data at the first common elevation;

generating a first image simulation of the acquired mask elevation image data;

acquiring image pattern data from a pattern used for forming the mask;

generating a second image simulation of the acquired image pattern data; and

comparing the first and second image simulations for a defect.

12. The computer readable medium of claim 11, wherein the first and second image simulations are two-dimensional.

13. The computer readable medium of claim 11, wherein the first and second image simulations are three-dimensional.

14. The computer readable medium of claim 11, wherein at least generating a first image simulation and generating a second image simulation is performed off-line.

15. A computer readable medium on a computer, the computer readable medium having computer executable instructions for performing a method comprising:

acquiring mask image data from a mask;

generating a first image simulation of the acquired mask image data;

acquiring pattern image data from a pattern used for forming the mask;

modifying the acquired pattern image data according to characteristics of resist material at different deposition elevations and producing therefrom acquired pattern elevation data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired pattern image data;

applying a second common elevation to an unmasked area of the acquired pattern image data; and

interpolating an edge between the mask area and the unmasked area of the acquired pattern image data at the first common elevation;

generating a second image simulation of the acquired pattern elevation image data; and

comparing the first and second image simulations for a defect.

16. The computer readable medium of claim 15, wherein the first and second image simulations are two-dimensional.

17. The computer readable medium of claim 15, wherein the first and second image simulations are three-dimensional.

18. The computer readable medium of claim 15, wherein at least generating a first image simulation and generating a second image simulation is performed off-line.

19. A computer readable medium on a computer, the computer readable medium having computer executable instructions for performing a method comprising:

acquiring image data of a first pattern from a mask;

modifying the acquired image data from the first pattern according to characteristics of resist material at different deposition elevations and producing therefrom acquired first pattern elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired image data from the first pattern;

applying a second common elevation to an unmasked area of the acquired image data from the first pattern; and

interpolating an edge between the mask area and the unmasked area of the acquired image data from the first pattern of the mask at the first common elevation;

generating a first image simulation of the acquired first pattern elevation image data;

acquiring image data of a second pattern from the mask;

generating a second image simulation of the acquired image data from the second pattern; and

comparing the first and second image simulations for a defect.

20. A computer readable medium on a computer, the computer readable medium having computer executable instructions for performing a method comprising:

acquiring image data of a first pattern from a mask;

generating a first image simulation of the acquired image data from the first pattern;

acquiring image data of a second pattern from the mask;

modifying the acquired image data from the second pattern according to characteristics of resist material at different deposition elevations and producing therefrom acquired second pattern elevation data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired image data from the second pattern;

applying a second common elevation to an unmasked area of the acquired image data from the second pattern; and

interpolating an edge between the mask area and the unmasked area of the acquired image data from the second pattern of the mask at the first common elevation;

generating a second image simulation of the acquired second pattern elevation image data; and

comparing the first and second image simulations for a defect.

21. A mask inspection system, comprising:

a mask having a plurality of identical patterns, including a first pattern and a second pattern;

an inspection machine operable for acquiring image data of the first pattern and for acquiring image data of the second pattern and for producing therefrom first acquired image data and second acquired image data, respectively;

a processor operable for modifying the first acquired image data according to characteristics of resist material at different deposition elevations and producing therefrom first acquired elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the first acquired image data;

applying a second common elevation to an unmasked area of the first acquired image data; and

interpolating an edge between the mask area and the unmasked area of the first acquired image data at the first common elevation;

the processor further operable for creating a first simulated image using the first acquired elevation image data;

the processor further operable for creating a second simulated image using the second acquired image data; and

the processor further operable for comparing the first and second simulated images for defects.

22. The mask inspection system of claim 21, wherein the first and second simulated images are two-dimensional.

23. The mask inspection system of claim 21, wherein the first and second simulated images are three-dimensional.

24. The mask inspection system of claim 21, wherein the processor is further operable for modifying at least the first acquired image data and the second acquired image data using convolution algorithms.

25. The mask inspection system of claim 21, wherein the processor creates at least one of the first simulated image and the second simulated image off-line.

26. A mask inspection system, comprising:

a mask having a plurality of identical patterns, including a first pattern and a second pattern;

an inspection machine operable for acquiring image data of the first pattern and for acquiring image data of the second pattern and for producing therefrom first acquired image data and second acquired image data, respectively;

a processor operable for modifying the second acquired image data according to characteristics of resist material at different deposition elevations and producing therefrom second acquired elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the second acquired image data;

applying a second common elevation to an unmasked area of the second acquired image data; and

interpolating an edge between the mask area and the unmasked area of the second acquired image data at the first common elevation;

the processor further operable for creating a first simulated image using the first acquired mask image data;

the processor further operable for creating a second simulated image using the second acquired elevation image data; and

the processor further operable for comparing the first and second simulated images for defects.

27. The mask inspection system of claim 26, wherein the first and second simulated images are two-dimensional.

28. The mask inspection system of claim 26, wherein the first and second simulated images are three-dimensional.

29. The mask inspection system of claim 26, wherein the processor is further operable for modifying at least the first acquired image data and the second acquired image data using convolution algorithms.

30. The mask inspection system of claim 26, wherein the processor creates at least one of the first simulated image and the second simulated image off-line.

31. A mask inspection system, comprising:

a mask fabricated from a pattern;

an inspection machine operable for acquiring image data from the mask and producing therefrom acquired mask image data;

a processor operable for modifying the acquired mask image data according to characteristics of resist material at different deposition elevations and producing therefrom acquired mask elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired mask image data;

applying a second common elevation to an unmasked area of the acquired mask image data; and

interpolating an edge between the mask area and the unmasked area of the acquired mask image data at the first common elevation;

the processor further operable for creating a first simulated image using the acquired mask elevation image data;

the processor further operable for acquiring image data from the pattern and producing therefrom acquired pattern image data;

the processor further operable for creating a second simulated image using the acquired pattern image data; and

the processor further operable for comparing the first and second simulated images for defects.

32. A mask inspection system, comprising:

a mask fabricated from a pattern;

an inspection machine operable for acquiring image data from the mask and producing therefrom acquired mask image data;

a processor operable for creating a first simulated image using the acquired mask image data;

the processor further operable for acquiring image data from the pattern and producing therefrom acquired pattern image data;

the processor further operable for modifying the acquired pattern image data according to characteristics of resist material at different deposition elevations and producing therefrom acquired pattern elevation image data, wherein the modification includes;

applying a first common elevation to a mask area of the acquired pattern image data;

applying a second common elevation to an unmasked area of the acquired pattern image data; and

interpolating an edge between the mask area and the unmasked area of the acquired pattern image data at the first common elevation;

the processor further operable for creating a second simulated image using the acquired pattern elevation image data; and

the processor further operable for comparing the first and second simulated images for defects.