Evaluating a geometric or material property of a multilayered structure

• US 6,812,047 B1
• Filed: 03/08/2000
• Issued: 11/02/2004
• Est. Priority Date: 03/08/2000
• Status: Expired due to Term

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Boxer Cross Inc. (Applied Materials Incorporated)
• Inventors: Li, Jiping, Borden, Peter G.
• Primary Examiner(s): Pert, Evan
• Application Number:
  US09/521,232
• Time in Patent Office: 1,700 Days
• Field of Search: 438/5, 438/7, 438/8, 438/9, 438/10, 438/14, 438/16, 438/17, 356/2, 356/491, 356/492, 356/495, 356/496, 356/503, 356/504, 356/511, 356/516, 356/364, 356/369, 250/492.2
• US Class Current: 438/16
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G01N 21/95684 Patterns showing highly reflecting parts, e.g. metallic elements
• CPC Class Codes: G01R 31/311 of integrated circuits G01R31/31728 takes precedence
• CPC Class Codes: H01L 22/12 for structural parameters, e.g. thickness, line width, refractive index, temperature, warp, bond strength, defects, optical inspection, electrical measurement of structural dimensions, metallurgic measurement of diffusions electrical measurement of diffusions H01L22/14

Abstract

A structure having a number of traces passing through a region is evaluated by using a beam of electromagnetic radiation to illuminate the region, and generating an electrical signal that indicates an attribute of a portion (also called “reflected portion”) of the beam reflected from the region. The just-described acts of “illuminating” and “generating” are repeated in another region, followed by a comparison of the generated signals to identify variation of a property between the two regions. Such measurements can identify variations in material properties (or dimensions) between different regions in a single semiconductor wafer of the type used in fabrication of integrated circuit dice, or even between multiple such wafers. In one embodiment, the traces are each substantially parallel to and adjacent to the other, and the beam has wavelength greater than or equal to a pitch between at least two of the traces. In one implementation the beam is polarized, and can be used in several ways, including, e.g., orienting the beam so that the beam is polarized in a direction parallel to, perpendicular to, or at 45° to the traces. Energy polarized parallel to the traces is reflected by the traces, whereas energy polarized perpendicular to the traces passes between the traces and is reflected from underneath the traces. Measurements of the reflected light provide an indication of changes in properties of a wafer during a fabrication process.

Claims

1. A method for evaluating a structure, the method comprising:

illuminating a region of the structure, the structure having a plurality of lines passing through said region;

generating an electrical signal indicative of an attribute of a portion of a beam, the portion being reflected from said region;

repeating the acts of “

illuminating” and

“

generating”

in another region having another plurality of lines, thereby to obtain another electrical signal; and

comparing said electrical signal with said another electrical signal to identify variation of a property between said region and said another region;

wherein;

the attribute being measured is the optical phase.

2. The method of claim 1 wherein:

the beam is polarized in a direction substantially parallel to one of the lines; and

said portion is reflected by at least some lines in said plurality of lines.

3. The method of claim 2 wherein:

said portion passes through a transmissive medium other than a layer of a semiconductor wafer, the transmissive medium being located between a source of the beam and said some lines.

4. The method of claim 2 wherein the beam is hereinafter “

first beam”

, the method further comprising;

illuminating said region with a second beam, a portion of energy in said second beam that is not reflected by said region being converted into heat, said second beam having an intensity modulated at a predetermined frequency being sufficiently small to cause a majority of said heat to transfer by diffusion from said region;

wherein the portion of the first beam sensed in the act of generating is modulated in phase with modulation of said second beam.

5. The method of claim 4 wherein:

the second beam is polarized in a direction parallel to said some lines; and

at least a portion of the second beam reflects from a surface of said some lines.

6. The method of claim 1 wherein:

the beam is nonpolarized;

the optical phase is a first phase of a first component of said portion polarized in a direction substantially perpendicular to some lines in said plurality of lines, and the electrical signal is hereinafter “

first electrical signal”

; and

the method further comprises generating a second electrical signal indicative of a second phase of a second component of said portion polarized in a direction substantially parallel to said some lines.

7. The method of claim 1 wherein:

the beam is polarized in a direction at least substantially perpendicular to one of the two lines;

the structure includes a layer located between the semiconductor substrate and the two lines; and

said portion is reflected by the layer.

8. The method of claim 7 wherein:

the lines are embedded within the layer so that at least a part of the layer is located between said some lines and at least some of said portion passes through said part.

9. The method of claim 7 wherein the beam contains photons having energy equal to or lower than bandgap energy of a semiconductor material in said region, the method further comprising:

creating a plurality of charge carriers in the layer, the charge carriers being modulated at a frequency that is sufficiently low to avoid creation of a wave of the charge carriers;

wherein the portion of the beam used in the act of generating is modulated at said frequency and in phase with modulation of the charge carriers.

10. The method of claim 1 wherein the structure is a semiconductor wafer, the method further comprising, prior to the acts of illuminating and “

generating”

;

adding dopant atoms to at least said region; and

creating said plurality of lines in at least said region.

11. The method of claim 10 further comprising:

changing a process parameter used in either one of the acts of adding and creating, if the variation is greater than a predetermined limit.

12. The method of claim 1 wherein:

said region is at a predetermined location in the structure; and

said another region is at said predetermined location in another structure.

13. The method of claim 1 wherein:

said region is at a first location in the structure; and

said another region is at a second location in said structure.

14. The method of claim 1 wherein:

all lines comprise a metal; and

the property is a material property of the metal.

15. The method of claim 1 wherein:

all lines comprise a suicide; and

the property is a material property of the silicide.

16. The method of claim 1 wherein:

all lines comprise a gas in a corresponding plurality of grooves; and

the property is a geometric property of the grooves.

17. The method of claim 1 wherein:

at least one of said lines has a void therein; and

the property is voiding.

54. The method of claim 17 wherein,

all lines comprise a metal;

and

the property is a material property of the metal.

18. A method for evaluating a structure, the method comprising:

illuminating a region of the structure, the structure having a plurality of lines passing through said region;

generating an electrical signal indicative of an attribute of a portion of a beam, the portion being reflected from said region;

repeating the acts of “

illuminating” and

“

generating”

in another region having another plurality of lines, thereby to obtain another electrical signal; and

comparing said electrical signal with said another electrical signal to identify variation of a geometric or material property between said region and said another region;

wherein;

at least two of the lines pass through the region and are each at least substantially parallel to and adjacent to the other; and

the beam has a wavelength greater than a pitch of the two lines;

the attribute is either intensity or phase; and

the plurality of lines act as a polarizer so that reflection of the beam from the structure is allowed only from particular polarization orientations.

19. The method of claim 18 wherein:

the beam is polarized in a direction substantially parallel to one of the two lines; and

said portion is reflected by the two lines.

20. The method of claim 19 wherein:

the structure includes a layer located between a source of the beam and the two lines; and

the layer is at least partially transmissive, so that said portion passes through the layer.

21. The method of claim 19 wherein:

said portion passes through a transmissive medium other than a layer of a semiconductor wafer, the transmissive medium being located between a source of the beam and the two lines.

22. The method of claim 19 wherein the beam is hereinafter “

first beam”

, the method further comprising;

illuminating said region with a second beam, a portion of energy in said second beam that is not reflected by said region being converted into heat, said second beam having an intensity modulated at a predetermined frequency being sufficiently small to cause a majority of said heat to transfer by diffusion from said region;

wherein the portion of the first beam sensed in the act of generating is modulated in phase with modulation of said second beam.

23. The method of claim 22 wherein:

the second beam is polarized in a direction parallel to one of the two lines; and

at least a portion of the second beam reflects from a surface of said “

one of the two lines.”

24. The method of claim 18 wherein:

the beam is nonpolarized;

the attribute is a first intensity of a first component of said portion polarized in a direction substantially perpendicular to one of the two lines, and the electrical signal is hereinafter “

first electrical signal”

; and

the method further comprises generating a second electrical signal indicative of a second intensity of a second component of said portion polarized in a direction substantially parallel to said one of the two lines.

25. The method of claim 18 wherein:

the beam is polarized in a direction at least substantially perpendicular to one of the two lines;

the structure includes a layer located between the semiconductor substrate and the two lines; and

said portion is reflected by the layer.

26. The method of claim 25 wherein:

the lines are embedded within the layer so that at least a part of the layer is located between the two lines and at least some of said portion passes through said part.

27. The method of claim 25 wherein the beam contains photons having energy equal to or lower than bandgap energy of a semiconductor material in said region, the method further comprising:

creating a plurality of charge carriers in the layer, the charge carriers being modulated at a frequency that is sufficiently low to avoid creation of a wave of the charge carriers;

wherein the portion of the beam used in the act of generating is modulated at said frequency and in phase with modulation of the charge carriers.

28. The method of claim 18 wherein the structure is a semiconductor wafer, the method further comprising, prior to the acts of illuminating and “

generating”

;

adding dopant atoms to at least said region; and

creating said plurality of lines in at least said region.

29. The method of claim 28 further comprising:

changing a process parameter used in either one of the acts of adding and creating, if the variation is greater than a predetermined limit.

30. The method of claim 18 wherein:

said region is at a predetermined location in the structure; and

said another region is at said predetermined location in another structure.

31. The method of claim 18 wherein:

said region is at a first location in the structure; and

said another region is at a second location in said structure.

32. The method of claim 18 wherein:

all lines comprise a silicide; and

the property is a material property of the suicide.

33. The method of claim 18 wherein:

all lines comprise a gas in a corresponding plurality of grooves; and

the property is a geometric property of the grooves.

34. The method of claim 18 wherein:

at least one of said lines has a void therein; and

the property is voiding.

35. The method of claim 18 wherein:

all lines comprise a metal; and

the property is a material property of the metal.

36. The method of claim 35 wherein:

the structure includes a layer located between a source of the beam and said some lines; and

the layer is at least partially transmissive, so that said portion passes through the layer.

37. A method for evaluating a structure having at least a plurality of lines and a layer in contact with said lines, at least two lines in the plurality being each at least substantially parallel to the other, the method comprising:

illuminating the structure with a beam of electromagnetic radiation having at least two polarized components wherein a first component is substantially parallel to the two lines, and a second component is substantially perpendicular to the two lines;

generating a first electrical signal indicative of intensity of a portion of the first component reflected by at least said two lines; and

generating a second electrical signal indicative of intensity of a portion of the second component reflected by the layer;

wherein the acts of generating are performed at least contemporaneously relative to one another.

38. The method of claim 37 wherein:

the lines are non-conductive;

the structure is a wafer having formed therein a plurality of integrated circuit dice; and

the method further comprises changing a process parameter used in creation of another wafer based on said profile.

39. The method of claim 37 wherein:

all lines comprise a metal; and

the property is a material property of the metal.

40. The method of claim 37 wherein:

all lines comprise a silicide; and

the property is a material property of the silicide.

41. The method of claim 37 wherein:

all lines comprise a gas in a corresponding plurality of grooves; and

the property is a geometric property of the grooves.

42. The method of claim 37 wherein:

the acts of generating are performed simultaneously relative to one another.

43. The method of claim 37 wherein:

at least one of said lines has a void therein; and

the property is voiding.

44. A method for evaluating a structure having at least a plurality of lines and a layer in contact with said lines, the method comprising:

illuminating a region of the structure using a beam of electromagnetic radiation, the structure having a plurality of lines in said region, the beam having a wavelength greater than or equal to a pitch between at least two lines in the plurality, said two lines being each at least substantially parallel to and adjacent to the other; and

generating an electrical signal indicative of an attribute of a portion of the beam, the portion being reflected from said region;

wherein

the attribute is either intensity or phase; and

the plurality of lines act as a polarizer so that the portion of the beam reflected from said region is only from particular polarization orientations.

45. The method of claim 44 wherein:

the lines are conductive;

the structure is a wafer having formed therein a plurality of integrated circuit dice; and

the method further comprises changing a process parameter used in creation of another wafer based on the electrical signal.

46. The method of claim 44 further comprising:

repeating the acts of “

illuminating” and

“

generating”

in another region having another plurality of lines, thereby to obtain additional electrical signal for said another region; and

comparing said electrical signal with said another electrical signal to identify variation of a material property between said region and said another region.

47. The method of claim 44 wherein:

the attribute is a first intensity of a first component of said portion polarized in a direction perpendicular to one of the two traces, and the electrical signal is hereinafter “

first electrical signal”

; and

the method further comprises generating a second electrical signal indicative of a second intensity of a second component of said portion polarized in a direction parallel to said one of the two lines.

48. The method of claim 47 wherein:

the acts of generating are performed contemporaneously.

49. The method of claim 48 wherein:

the lines are conductive;

the structure is a wafer having formed therein a plurality of integrated circuit dice; and

the method further comprises changing a process parameter used in creation of another wafer if the first electrical signal differs from the second electrical signal by a predetermined limit.

50. The method of claim 44 wherein:

all lines comprise a silicide; and

the property is a material property of the suicide.

51. The method of claim 44 wherein:

all lines comprise a gas in a corresponding plurality of grooves; and

the property is a geometric property of the grooves.

52. The method of claim 44 wherein:

at least one of said lines has a void therein; and

the property is voiding.

53. The method of claim 44 wherein:

the lines are non-conductive;

the structure is a wafer having formed therein a plurality of integrated circuit dice; and

the method further comprises changing a process parameter used in creation of another wafer based on the electrical signal.

55. A method for evaluating a structure having at least a plurality of lines and a layer in contact with said lines, at least two lines in the plurality being each at least substantially parallel to the other, the method comprising:

illuminating a first region of the structure with a first beam of electromagnetic radiation;

illuminating a second region of the structure with a second beam of electromagnetic radiation;

generating a first electrical signal indicative of intensity of a portion of the first beam reflected from the first region;

generating a second electrical signal indicative of intensity of a portion of the second beam reflected from the second region; and

using a difference between the first electrical signal with the second electrical signal as a profile of a surface in the structure;

wherein;

each of the first beam and the second beam is polarized; and

the first beam has a polarization direction perpendicular to the polarization direction of the second beam.

56. The method of claim 55 wherein:

the lines are conductive;

the structure is a wafer having formed therein a plurality of integrated circuit dice; and

the method further comprises changing a process parameter used in creation of another wafer if the first electrical signal differs from the second electrical signal by a predetermined limit.

57. The method of claim 55 wherein:

the lines are non-conductive;

the structure is a wafer having formed therein a plurality of integrated circuit dice; and

the method further comprises changing a process parameter used in creation of another wafer based on said profile.

58. The method of claim 55 wherein:

all lines comprise a metal; and

the property is a material property of the metal.

59. The method of claim 55 wherein:

all lines comprise a silicide; and

the property is a material property of the silicide.

60. The method of claim 55 wherein:

all lines comprise a gas in a corresponding plurality of grooves; and

the property is a geometric property of the grooves.

61. The method of claim 55 wherein:

at least one of said lines has a void therein; and

the property is voiding.

62. An apparatus for evaluating a structure, the apparatus comprising:

means for illuminating a region of the structure, the structure having a plurality of lines passing through said region;

means for generating an electrical signal indicative of an attribute of a portion of a beam, the portion being reflected from said region; and

means for comparing said electrical signal with said another electrical signal from another region having another plurality of lines, to identify variation of a property between said region and said another region;

wherein;

the attribute being measured is the optical phase.

63. An apparatus for evaluating a structure, the apparatus comprising:

means for illuminating a region of the structure, the structure having a plurality of lines passing through said region;

means for generating an electrical signal indicative of an attribute of a portion of a beam, the portion being reflected from said region;

means for comparing said electrical signal with said another electrical signal from another region having another plurality of lines, to identify variation of a property between said region and said another region;

wherein;

at least two of the lines pass through the region and are each at least substantially parallel to and adjacent to the other; and

the beam has a wavelength greater than a pitch of the two lines;

the attribute is either intensity or phase; and

the plurality of lines act as a polarizer so that reflection of the beam from the structure is allowed only from particular polarization orientations.

64. An apparatus for evaluating a structure having at least a plurality of lines and a layer in contact with said lines, the apparatus comprising:

means for illuminating a region of the structure using a beam of electromagnetic radiation, the structure having a plurality of lines in said region, the beam having a wavelength greater than or equal to a pitch between at least two lines in the plurality, said two lines being each at least substantially parallel to and adjacent to the other; and

means for generating an electrical signal indicative of an attribute of a portion of the beam, the portion being reflected from said region;

wherein

the attribute is either intensity or phase; and

the plurality of lines act as a polarizer so that the portion of the beam reflected from said region is only from particular polarization orientations.

65. An apparatus for evaluating a structure having at least a plurality of lines and a layer in contact with said lines, at least two lines in the plurality being each at least substantially parallel to the other, the apparatus comprising:

means for illuminating the structure with a beam of electromagnetic radiation having at least two polarized components wherein a first component is substantially parallel to the two lines, and a second component is substantially perpendicular to the two lines;

means for generating a first electrical signal indicative of intensity of a portion of the first component reflected by at least said two lines; and

means for generating a second electrical signal indicative of intensity of a portion of the second component reflected by the layer;

wherein the means for generating are operated at least contemporaneously relative to one another.

66. An apparatus for evaluating a structure having at least a plurality of lines and a layer in contact with said lines, at least two lines in the plurality being each at least substantially parallel to the other, the apparatus comprising:

means for illuminating a first region of the structure with a first beam of electromagnetic radiation;

means for illuminating a second region of the structure with a second beam of electromagnetic radiation;

means for generating a first electrical signal indicative of intensity of a portion of the first beam reflected from the first region;

means for generating a second electrical signal indicative of intensity of a portion of the second beam reflected from the second region; and

means for using a difference between the first electrical signal with the second electrical signal as a profile of a surface in the structure;

wherein;

each of the first beam and the second beam is polarized; and

the first beam has a polarization direction perpendicular to the polarization direction of the second beam.

67. An apparatus particularly characterized by the presence of parallel lines in a structure being evaluated such that the lines of the structure being evaluated act as a polarizer from which reflected light is used by the apparatus to generate an electrical signal, representative of phase or intensity, for comparison.

68. A method particularly characterized by the presence of parallel lines in a structure being evaluated such that the lines of the structure being evaluated act as a polarizer from which reflected light is used by the method to generate an electrical signal, representative of phase or intensity, for comparison.