Evaluating a property of a multilayered structure

• US 20050088188A1
• Filed: 10/29/2004
• Published: 04/28/2005
• Est. Priority Date: 03/08/2000
• Status: Active Grant

• Current Assignee: Applied Materials Incorporated
• Original Assignee: Applied Materials Incorporated
• Inventors: Li, Jiping, Borden, Peter G.
• Granted Patent: US 7,465,591 B2
• Time in Patent Office: Days
• US Class Current: 356/237.500
• 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 traces passing through said region;

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

repeating the acts of “

illuminating” and

“

generating”

in another region having another plurality of traces, 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.

2. The method of claim 1 wherein:

the attribute being measured is the optical phase.

3. The method of claim 1 wherein:

at least two of the traces 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 distance between center lines of the two traces.

4. The method of claim 3 wherein:

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

said portion is reflected by the two traces.

5. The method of claim 4 wherein:

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

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

6. The method of claim 4 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 traces.

7. The method of claim 4 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.

8. The method of claim 7 wherein:

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

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

one of the two traces.”

9. The method of claim 3 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 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 substantially parallel to said one of the two traces.

10. The method of claim 3 wherein:

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

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

said portion is reflected by the layer.

11. The method of claim 10 wherein:

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

12. The method of claim 10 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.

13. 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 traces in at least said region.

14. The method of claim 13 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.

15. 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.

16. 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.

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

illuminating a region of the structure using a beam of electromagnetic radiation, the structure having a plurality of traces in said region, the beam having a wavelength greater than or equal to a pitch between at least two traces in the plurality, said two traces 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.

18. The method of claim 17 wherein:

the traces 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.

19. The method of claim 17 further comprising:

repeating the acts of “

illuminating” and

“

generating”

in another region having another plurality of traces, 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.

20. The method of claim 17 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 traces.

21. The method of claim 20 wherein:

the acts of generating are performed contemporaneously.

24. The method of claim 21 wherein:

the traces 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.

22. A method for evaluating a structure having at least a plurality of traces and a layer in contact with said traces, at least two traces 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 traces, and a second component is substantially perpendicular to the two traces;

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

23. The method of claim 22 wherein:

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

25. An apparatus for evaluating a wafer having a plurality of traces, said apparatus comprising:

a source of a beam of electromagnetic radiation having a wavelength greater than or equal to a pitch between at least two traces in said wafer, said two traces being each at least substantially parallel to and adjacent to the other;

a photosensitive element located in a path of a portion of the beam, the portion being reflected from said region;

a memory; and

a comparator coupled to each of said memory and said photosensitive element.

26. The apparatus of claim 25 further comprising:

a polarizer located in a path of said beam between said source and said wafer.

27. The apparatus of claim 26 further comprising:

a stage supporting said wafer, the stage holding the wafer to orient the traces in a predetermined direction;

wherein the polarizer is aligned to orient polarization of the beam in said predetermined direction.

28. The apparatus of claim 26 further comprising:

a stage supporting said wafer, the stage holding the wafer to orient the traces in a predetermined direction;

wherein the polarizer is aligned to orient polarization of the beam perpendicular to said predetermined direction.

29. The apparatus of claim 25 wherein:

said memory is coupled to the photosensitive element; and

during operation, said memory stores a first signal generated by the photosensitive element at a first time, the first signal being related to a first region in the wafer and said comparator compares the first signal with a second signal generated by the photosensitive element at a second time, the second signal being related to a second region.

30. A method for evaluating a structure having at least a plurality of traces and a layer in contact with said traces, at least two traces 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.

31. The method of claim 30 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.

32. The method of claim 30 wherein:

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

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

33. The method of claim 30 wherein:

the traces 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.

34. An apparatus for evaluating a wafer having a plurality of traces, said apparatus comprising:

a source of a beam of electromagnetic radiation having a wavelength greater than or equal to a pitch between at least two traces in said wafer, said two traces being each at least substantially parallel to and adjacent to the other;

a polarizing beam splitter located in a path of said beam between said source and said wafer; and

a polarizer located in a path of said beam between the polarizing beam splitter and the wafer.

35. The apparatus of claim 34 wherein:

the polarizing beam splitter is a Wollaston prism.

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

polarizing a beam of white light to obtain a beam of polarized white light;

illuminating a region of the structure with said beam of polarized white light; and

measuring a color of a portion of said beam of polarized white light reflected from the region.

37. The method of claim 36 wherein said region is a first region and said color is a first color, the method further comprising:

illuminating a second region of the structure with said beam of polarized white light;

measuring a second color of a portion of said beam of polarized white light reflected from the second region; and

using a difference in said first color and said second color to indicate a corresponding change in thickness of said layer.