Evaluating sidewall coverage in a semiconductor wafer

• US 6,911,349 B2
• Filed: 02/16/2001
• Issued: 06/28/2005
• Est. Priority Date: 02/16/2001
• 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): Fourson, George
• Assistant Examiner(s): MANDALA, MICHELLE
• Application Number:
  US09/788,273
• Publication Number:
  US 20020151092A1
• Time in Patent Office: 1,593 Days
• Field of Search: 438/7, 438/14, 438/16, 438/FOR.142
• US Class Current: 438/16
• CPC Class Codes: G01N 21/55 Specular reflectivity
• CPC Class Codes: G01R 31/307 of integrated circuits

Abstract

A sidewall or other feature in a semiconductor wafer is evaluated by illuminating the wafer with at least one beam of electromagnetic radiation, and measuring intensity of a portion of the beam reflected by the wafer. Change in reflectance between measurements provides a measure of a property of the feature. The change may be either a decrease in reflectance or an increase in reflectance, depending on the embodiment. A single beam may be used if it is polarized in a direction substantially perpendicular to a longitudinal direction of the sidewall. A portion of the energy of the beam is absorbed by the sidewall, thereby to cause a decrease in reflectance when compared to reflectance by a flat region. Alternatively, two beams may be used, of which a first beam applies heat to the feature itself or to a region adjacent to the feature, and a second beam is used to measure an increase in reflectance caused by an elevation in temperature due to heat transfer through the feature. The elevation in temperature that is measured can be either of the feature itself, or of a region adjacent to the feature.

Claims

1. A method of evaluating a feature in a semiconductor wafer, the method comprising:

illuminating the wafer with a beam of electromagnetic radiation having a majority of energy polarized in a selected direction, said selected direction being other than parallel to a longitudinal direction of the feature, wherein the wafer comprises a layer located between a source of the beam and the feature, the layer is at least partially transmissive, so that a portion of the beam passes through the layer, and the layer is thermally conductive; and

measuring a change in reflectance of the feature due to heat transfer therethrough caused by illumination with the beam.

2. The method of claim 1 wherein:

the feature includes a sidewall of a groove; and

the act of measuring is performed repeatedly at a plurality of locations transverse to the longitudinal direction of the groove.

3. The method of claim 2 wherein:

the beam has a wavelength greater than thickness of the sidewall.

4. The method of claim 1 wherein:

the beam has a wavelength greater than a dimension of the feature; and

the beam forms on the wafer a spot of a diameter greater than the dimension.

5. The method of claim 1 wherein:

the feature includes a trace of reflective material.

6. The method of claim 1 wherein:

the selected direction is at least substantially perpendicular to the longitudinal direction.

7. The method of claim 1 wherein:

the beam has a predetermined wavelength; and

the method further comprises filtering light of a wavelength other than the predetermined wavelength.

8. The method of claim 1 wherein the wafer has a plurality of features including the feature, and the method further comprises:

performing the act of measuring for each feature of the plurality; and

comparing measurements of multiple features.

9. The method of claim 8 wherein:

each feature is a sidewall; and

the act of comparing includes comparing measurements of two sidewalls located opposite to one another in a groove.

10. The method of claim 1 further comprising:

forming the feature of conductive material in the wafer by using at least one process parameter;

repeatedly performing said measuring intensity; and

changing the process parameter depending on measurements obtained from the act of repeatedly measuring.

27. The method of claim 1 wherein:

said layer is metallic.

28. The method of claim 1 wherein:

said layer comprises copper.

29. The method of claim 1 wherein:

said layer comprises tantalum.

30. The method of claim 1 wherein:

said layer comprises a barrier layer.

31. The method of claim 1 wherein:

said layer comprises a seed layer.

11. A method of evaluating wafers during fabrication, the method comprising:

forming a feature of conductive material in a wafer by using at least one process parameter;

illuminating the wafer with a beam of electromagnetic radiation having a majority of energy polarized in a direction other than parallel to a longitudinal direction of the feature; and

repeatedly measuring intensity of a portion of the beam reflected by the wafer at a plurality of locations transverse to the longitudinal direction;

changing the process parameter depending on measurements obtained from the act of repeatedly measuring;

determining a coefficient of a function that fits the measurements;

comparing the coefficient against a predetermined limit and performing the changing based on an outcome of the comparing.

12. The method of claim 11 wherein:

the feature includes a sidewall of a groove.

13. The method of claim 12 wherein

the beam has a wavelength greater than thickness of the sidewall.

14. The method of claim 11 wherein:

the beam has a wavelength greater than a dimension of the feature; and

the beam forms on the wafer a spot of a diameter greater than the dimension.

15. The method of claim 11 wherein:

the feature includes a trace of reflective material.

16. The method of claim 11 wherein:

the wafer includes a layer located between a source of the beam and the feature; and

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

17. The method of claim 11 wherein:

the beam has a predetermined wavelength; and

the method further comprises filtering light of a wavelength other than the predetermined wavelength.

18. The method of claim 11 wherein the wafer has a plurality of features including the feature, and the method further comprises:

performing the act of measuring for each feature of the plurality; and

comparing measurements of multiple features.

19. The method of claim 11 wherein the beam is a first beam, and the method further comprises:

illuminating the wafer with a second beam of electromagnetic radiation.

20. The method of claim 19 wherein:

the first beam forms a first spot on the wafer, the second beam forms a second spot;

the act of measuring includes measuring with the first spot and the second spots located on opposite sides of the feature; and

the method further comprises measuring with the first spot and the second spots located on the same side of the feature.

21. The method of claim 20 wherein:

the second spot at least partially overlaps the first spot.

32. The method of claim 11 wherein:

said conductive material comprises copper.

33. The method of claim 11 wherein:

said conductive material comprises tantalum.

34. The method of claim 11 wherein:

said conductive material forms a barrier layer during wafer fabrication.

35. The method of claim 11 wherein:

said conductive material forms a seed layer during wafer fabrication.

36. The method of claim 11 wherein:

said conductive material is metallic.

22. A method of evaluating a groove in a semiconductor wafer, the method comprising:

illuminating the wafer with a beam of light polarized in a direction P, said direction P forming an angle θ

with a longitudinal direction of the groove, with angle θ

>

45°

;

wherein the beam has a wavelength larger than a width of the groove, the groove is formed of a highly reflective material, and the groove has a first sidewall, a second sidewall and a floor between the first sidewall and the second sidewall;

heating of the groove by a portion of the light polarized perpendicular to the groove, heat from said heating being transmitted into a substrate of the semiconductor wafer; and

measuring intensity of light reflected by the wafer, wherein light absorbed in the groove measurably reduces the reflected light.

23. The method of claim 22 wherein:

using a measurement obtained from said measuring as an indication of a thickness of the sidewall.

24. The method of claim 22 wherein:

with angle θ

is approximately 90°

.

25. The method of claim 24 wherein:

said light reflected by the wafer is part of said beam.

26. The method of claim 24 wherein:

said light reflected by the wafer is part of another beam.

37. A method of evaluating a feature in a semiconductor wafer, the method comprising:

illuminating the wafer with a beam of electromagnetic radiation having a majority of energy polarized in a selected direction, said selected direction being substantially perpendicular to a longitudinal direction of the feature, wherein the wafer comprises a thermally conductive layer located between a source of the beam and the feature; and

measuring intensity of a portion of the beam reflected at least by the thermally conductive layer.

38. The method of claim 37 wherein:

said thermally conductive layer comprises a barrier layer.

39. The method of claim 37 wherein:

said thermally conductive layer comprises a seed layer.