Method for monitoring the rate of etching of a semiconductor

• US 6,687,014 B2
• Filed: 01/16/2002
• Issued: 02/03/2004
• Est. Priority Date: 01/16/2002
• Status: Expired due to Term

• Current Assignee: Polaris Innovations Limited (Wi-LAN Inc.)
• Original Assignee: Infineon Technologies AG
• Inventors: Zaidi, Shoaib Hasan, Mathad, Gangadhara S.
• Primary Examiner(s): Turner, Samuel A.
• Assistant Examiner(s): Lyons, Michael A.
• Application Number:
  US10/050,737
• Publication Number:
  US 20030133127A1
• Time in Patent Office: 748 Days
• Field of Search: 356/503, 356/504
• US Class Current: 356/504
• CPC Class Codes: G01B 11/0675 using interferometry
• CPC Class Codes: G01B 11/0683 measurement during deposition or removal of the layer

Abstract

A method of measuring the rate of etching of trenches on a substrate using interferometry is provided. The method comprises transmitting onto the substrate incident electromagnetic radiation having a wavelength above the wavelength at which the trenches act as waveguides for the radiation; collecting reflected electromagnetic radiation from the substrate; detecting a repetitive pattern of maximum intensities and minimum intensities of the reflected electromagnetic radiation during the etching; and determining the rate of etching based upon the wavelength of the incident electromagnetic radiation and the time period of the pattern.

Claims

1. A method of measuring the rate of etching of trenches on a substrate using interferometry comprising:

transmitting onto the substrate incident electromagnetic radiation having a wavelength above the wavelength at which the trenches act as waveguides for the radiation;

collecting reflected electromagnetic radiation from the substrate;

detecting a repetitive pattern of maximum intensities and minimum intensities of the reflected electromagnetic radiation during the etching; and

determining the rate of etching based upon the wavelength of the incident electromagnetic radiation and the time period of the pattern.

2. A method as in claim 1, wherein the trenches are circular and the wavelength of the incident electromagnetic radiation is greater than 1.71 times the diameter of the trenches.

3. A method as in claim 1, wherein the trenches are rectangular and the wavelength of the incident electromagnetic radiation is greater than 2.00 times the length of the long edge of the rectangle.

4. A method as in claim 1, wherein the critical dimension of the trenches is 70 nm or less.

5. A method as in claim 1, wherein the critical dimension of the trenches is 100 nm or less.

6. A method as in claim 1, wherein the critical dimension of the trenches is 200 nm or less.

7. A method as in claim 6, wherein the wavelength of the incident electromagnetic radiation is 470 nm or greater.

8. A method as in claim 1, wherein the substrate is a semiconductor wafer.

9. A method as in claim 8, wherein the semiconductor wafer is selected from the group consisting of silicon, germanium and the compound semiconductors.

10. A method as in claim 9, wherein the compound semiconductors are selected from the group consisting of gallium arsenide (GaAs), gallium nitride (GaN), indium phosphide (InP) and gallium indium phosphide (GaInP).

11. A method as in claim 1, wherein the substrate is housed within an etching chamber and the incident electromagnetic radiation and the reflected electromagnetic radiation are transmitted through a window in the etching chamber.

12. A method as in claim 1, wherein the incident electromagnetic radiation is transmitted from a source of radiation selected from the group consisting of a diode laser, a tungsten/halogen lamp and a helium/neon light.

13. A method as in claim 1, wherein the transmitting comprises transmitting the incident electromagnetic radiation through a focusing lens onto the substrate.

14. A method as in claim 1, wherein the collecting comprises collecting the reflected electromagnetic radiation from a collecting lens.

15. A method as in claim 1, wherein the detecting comprises detecting the repetitive pattern using a photodetector.

16. A method as in claim 1, wherein the rate of etching is proportional to λ

/2T, where λ

is the wavelength of the incident light and T is the time period between consecutive maximum intensities of the reflected light or consecutive minimum intensities of the reflected light.

17. A method of determining the depth of trenches on a substrate using interferometry comprising:

transmitting onto the substrate incident electromagnetic radiation having a wavelength greater than the cutoff wavelength for the trenches to act as waveguides for the radiation;

collecting reflected electromagnetic radiation from the substrate;

detecting a repetitive pattern of maximum intensities and minimum intensities of the reflected electromagnetic radiation; and

determining the depth of the trenches based upon the wavelength of the incident electromagnetic radiation and the time period of the pattern.

18. A method as in claim 17, wherein the trenches are circular and the cutoff wavelength is approximately 1.71 times the diameter of the trenches.

19. A method as in claim 17, wherein the trenches are rectangular and the cutoff wavelength is approximately 2.00 times the length of the long edge of the rectangle.

20. A method as in claim 17, wherein the critical dimension of the trenches is 70 nm or less.

21. A method as in claim 17, wherein the critical dimension of the trenches is 100 nm or less.

22. A method as in claim 17, wherein the critical dimension of the trenches is 200 nm or less.

23. A method as in claim 22, wherein the wavelength of the incident electromagnetic radiation is 470 nm or greater.

24. A method as in claim 17, wherein the substrate is a semiconductor wafer.

25. A method as in claim 24, wherein the semiconductor is selected from the group consisting of silicon, germanium and the compound semiconductors.

26. A method as in claim 25, wherein the compound semiconductors are selected from the group consisting of gallium arsenide (GaAs), gallium nitride (GaN), indium phosphide (InP) and gallium indium phosphide (GaInP).

27. A method as in claim 17, wherein the substrate is housed within an etching chamber and the incident electromagnetic radiation and the reflected electromagnetic radiation are transmitted through a window in the etching chamber.

28. A method as in claim 17, wherein the incident electromagnetic radiation is transmitted from a source of radiation selected from the group consisting of a diode laser, a tungsten/halogen lamp and a helium/neon light.

29. A method as in claim 17, wherein the transmitting comprises transmitting the incident electromagnetic radiation through a focusing lens onto the substrate.

30. A method as in claim 17, wherein the collecting comprises collecting the reflected electromagnetic radiation from a collecting lens.

31. A method as in claim 17, wherein the detecting comprises detecting the repetitive pattern using a photodetector.

32. A method as in claim 17, wherein the determining of the depth comprises determining the rate at which the depth is increasing based upon the formula λ

/2T, where λ

is the wavelength of the incident light and T is the time period between consecutive maximum intensities of the reflected light or consecutive minimum intensities of the reflected light.