Inspection technique of photomask

• US 6,272,236 B1
• Filed: 07/18/2000
• Issued: 08/07/2001
• 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, Leo
• Assistant Examiner(s): Werner, Brian P.
• Application Number:
  US09/618,503
• Time in Patent Office: 385 Days
• Field of Search: 382/144, 382/145, 382/149, 382/151, 382/157, 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, 716/22, 702/40, 702/159, 430/30
• 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 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 adding elevation data to the acquired mask image data and producing therefrom acquired mask elevation image data;

a processor operable for creating a first simulated image using the acquired mask elevation image data according to the behavior of a resist material;

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 in the mask.

2. The mask inspection system of claim 1, wherein the processor is further operable modifying the acquired pattern image data to characteristics of resist materials used for forming a wafer using the mask.

3. A method of inspecting a mask, comprising:

acquiring mask image data by imaging the mask;

adding elevation data to the acquired mask image data and producing therefrom acquired mask elevation image data;

generating a first image simulation of the acquired mask elevation image data according to the behavior of a resist material;

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 in the mask.

4. The method of claim 3, wherein adding elevation data to the acquired mask image data includes:

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

applying a second common elevation to an unmask ed 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.

5. A method of inspecting a mask, comprising:

acquiring mask image data by imaging 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;

adding elevation data to the acquired pattern image data and producing therefrom acquired pattern elevation data;

generating a second image simulation of the acquired pattern elevation image data according to the behavior of a resist material;

comparing the first and second image simulations for a defect in the mask.

6. The method of claim 5, wherein adding elevation data to the acquired pattern image data 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.

7. A method of inspecting a mask, comprising:

acquiring image data of a first pattern by imaging the mask;

adding elevation data to the acquired image data from the first pattern and producing therefrom acquired first pattern elevation image data;

generating a first image simulation of the acquired first pattern elevation image data according to the behavior of a resist material;

acquiring image data of a second pattern by imaging 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 in the mask.

8. The method of claim 7, wherein adding elevation data to the acquired image data from the first pattern 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.

9. 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 by imaging the first pattern;

acquiring image data of a second by imaging from the mask;

adding elevation data to the acquired image data by imaging the second pattern and producing therefrom acquired second pattern elevation data;

generating a second image simulation of the acquired second pattern elevation image data according to the behavior of a resist material; and

comparing the first and second image simulations for a defect in the mask.

10. The method of claim 9, wherein adding elevation data to the acquired image data from the second pattern 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.

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 by imaging a mask;

adding elevation data to the acquired mask image data and producing therefrom acquired mask elevation image data;

generating a first image simulation of the acquired mask elevation image data according to the behavior of a resist material;

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 in the mask.

12. The computer readable medium of claim 11, wherein adding elevation data to the acquired mask image data 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.

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

acquiring mask image data by imaging a mask;

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

acquiring pattern image data by imaging a pattern used for forming the mask;

adding elevation data to the acquired pattern image data and producing therefrom acquired pattern elevation data;

generating a second image simulation of the acquired pattern elevation image data according to the behavior of a resist material; and

comparing the first and second image simulations for a defect in the mask.

14. The computer readable medium of claim 13, wherein adding elevation data to the acquired pattern image data 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.

15. 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 by imaging a mask;

adding elevation data to the acquired image data from the first pattern and producing therefrom acquired first pattern elevation image data;

generating a first image simulation of the acquired first pattern elevation image data according to the behavior of a resist material;

acquiring image data of a second pattern by imaging 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 in the mask.

16. The computer readable medium of claim 15, wherein adding elevation data to the acquired image data from the first pattern 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.

17. 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 by imaging a mask;

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

acquiring image data of a second pattern by imaging the mask;

adding elevation data to the acquired image data from the second pattern and producing therefrom acquired second pattern elevation data;

generating a second image simulation of the acquired second pattern elevation image data according to the behavior of a resist material; and

comparing the first and second image simulations for a defect in the mask.

18. The computer readable medium of claim 17, wherein adding elevation data to the acquired image data from the second pattern 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.

19. 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 adding elevation data to the first acquired image data and producing therefrom first acquired elevation image data;

the processor further operable for creating a first simulated image using the first acquired elevation image data according to the behavior of a resist material;

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 in the mask.

20. The mask inspection system of claim 19, wherein the addition of elevation data to the first acquired image data by the processor includes:

the processor further operable for applying a first common elevation to a mask area of the first acquired image data;

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

the processor further operable for interpolating an edge between the mask area and the unmasked area of the first acquired image data at the first common elevation.

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 adding elevation data to the second acquired image data and producing therefrom second acquired elevation image data;

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 according to the behavior of a resist material; and

the processor fiuther operable for comparing the first and second simulated images for defects in the mask.

22. The mask inspection system of claim 21, wherein the addition of elevation data to the second acquired image data by the processor includes:

the processor further operable for applying a first common elevation to a mask area of the second acquired image data;

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

the processor further operable for interpolating an edge between the mask area and the unmasked area of the second acquired image data at the first common elevation.

23. 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 adding elevation data to the acquired mask image data and producing therefrom acquired mask elevation image data;

the processor further operable for creating a first simulated image using the acquired mask elevation image data according to the behavior of a resist material;

the processor fuirther 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 in the mask.

24. The mask inspection system of claim 23, wherein the addition of elevation data to the acquired mask image data by the processor includes:

the processor further operable for applying a first common elevation to a mask area of the acquired mask image data;

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

the processor further operable for interpolating an edge between the mask area and the unmasked area of the acquired mask image data at the first common elevation.

25. 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 adding elevation data to the acquired pattern image data and producing therefrom acquired pattern elevation image data;

the processor filrther operable for creating a second simulated image using the acquired pattern elevation image data according to the behavior of a resist material; and

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

26. The mask inspection system of claim 25, wherein the addition of elevation data to the acquired pattern image data by the processor includes:

the processor further operable for applying a first common elevation to a mask area of the acquired pattern image data;

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

the processor further operable for interpolating an edge between the mask area and the unmasked area of the acquired pattern image data at the first common elevation.

27. A computer program product, comprising:

a computer usable medium having a computer readable code means embodied therein for causing a detection of defects in a mask used in a photolithography system, the computer readable program code means in said computer program product comprising;

computer readable program code means for causing a computer to receive a set of digitized image data from the mask;

computer readable code means for adding elevation data to the digitized image data and producing therefrom digitized elevation image data;

computer readable program code means for causing a computer to generate a first three-dimensional image from the set of digitized elevation image data according to the behavior of a resist material;

computer readable program code means for causing a computer to receive a set of digitized image data from a pattern used to defme the mask;

computer readable program code means for causing a computer to generate a second three-dimensional image from the set of digitized pattern data; and

computer readable program code means for causing a computer to compare the first and second three-dimensional images for a defect in the mask.

28. The computer readable medium of claim 27, wherein computer readable code means for adding elevation data to the digitized image data includes:

computer readable code means for applying a first common elevation to a mask area of the digitized image data from the mask;

computer readable code means for applying a second common elevation to an unmasked area of the digitized image data from the mask; and

computer readable code means for interpolating an edge between the mask area and the unmasked area of the digitized image data from the mask at the first common elevation.

29. A computer program product, comprising:

a computer usable medium having a computer readable code means embodied therein for causing a detection of defects in a mask used in a photolithography system, the computer readable program code means in said computer program product comprising;

computer readable program code means for causing a computer to receive a set of digitized image data from the mask;

computer readable program code means for causing a computer to generate a first three-demensional image from the set of digitized elevation image data;

computer readable program code means for causing a computer to receive a set of digitized image data from a pattern used to define the mask;

computer readable code means for adding elevation data to the digitized image data from the pattern used to define the mask and producing therefrom digitized elevation pattern data;

computer readable program code means for causing a computer to generate a second three-dimensional image from the set of digitized elevation pattern data according to the behavior of a resist material; and

computer readable program code means for causing a computer to compare the first and second three-dimensional images for a defect in the mask.

30. The computer readable medium of claim 29, wherein computer readable code means for adding elevation data to the digitized image data from the pattern used to define the mask includes:

computer readable code means for applying a first common elevation to a mask area of the digitized image data from the pattern used to define the mask;

computer readable code means for applying a second common elevation to an unmasked area of the digitized image data from the pattern used to define the mask; and

computer readable code means for interpolating an edge between the mask area and the unmasked area of the digitized image data from the pattern used to define the mask at the first common elevation.

32. The computer readable medium of claim 29, wherein computer readable code means for adding elevation data to the digitized image data from the first pattern includes:

computer readable code means for applying a first common elevation to a mask area of the digitized image data from the first pattern;

computer readable code means for applying a second common elevation to an unmasked area of the digitized image data from the first pattern; and

computer readable code means for interpolating an edge between the mask area and the unmasked area of the digitized image data from the first pattern at the first common elevation.

31. A computer program product, comprising:

a computer usable medium having a computer readable code means embodied therein for causing a detection of defects in a mask having a plurality of identical patterns, including a first pattern and a second pattern, in a photolithography system, the computer readable program code means in said computer program product comprising;

computer readable program code means for causing a computer to receive a set of digitized image data from the first pattern;

computer readable code means for adding elevation data to the digitized image data from the first pattern and producing therefrom digitized elevation image data from the first pattern;

computer readable program code means for causing a computer to generate a first three-dimensional image from the set of digitized elevation image data from the first pattern according to the behavior of a resist material;

computer readable program code means for causing a computer to receive a set of digitized image data from the second pattern;

computer readable program code means for causing a computer to generate a second three-dimensional image from the set of digitized image data from the second pattern; and

computer readable program code means for causing a computer to compare the first and second three-dimensional images for a defect in the mask.