Measurement of overlay offset in semiconductor processing

• US RE45,943 E1
• Filed: 05/14/2014
• Issued: 03/22/2016
• Est. Priority Date: 03/14/2007
• Status: Active Grant

• Current Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: Huang, Te-Chih, Ke, Chih-Ming, Gau, Tsai-Sheng
• Primary Examiner(s): MENEFEE, JAMES A
• Application Number:
  US14/120,303
• Time in Patent Office: 678 Days
• Field of Search: 356/614, 356/615, 356/620
• US Class Current: 1/1
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• 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 system for overlay offset measurement in semiconductor manufacturing including a radiation source, a detector, and a calculation unit. The radiation source is operable to irradiate an overlay offset measurement target. The detector is operable to detect a first reflectivity and a second reflectivity of the irradiated overlay offset measurement target. The calculation unit is operable to determine an overlay offset using the detected first and second reflectivity by determining a predetermined overlay offset amount which provides an actual offset of zero.

Claims

1. A system for overlay offset measurement in semiconductor manufacturing, comprising:

a radiation source, wherein the radiation source is operable to irradiate an overlay offset measurement target;

a detector, wherein the detector is operable to detect a first reflectivity and a second reflectivity of the irradiated overlay offset measurement target; and

a calculation unit, wherein the calculation unit is operable to determine an overlay offset using the detected first and second reflectivity by determining a predetermined overlay offset amount which provides an actual offset of zero.

2. The system of claim 1, wherein the first reflectivity is associated with a first and a second feature of a wafer irradiated at a single wavelength.

3. The system of claim 2, wherein the second reflectivity is associated with a third and a fourth feature of the wafer irradiated at the single wavelength.

4. The system of claim 1, wherein the calculation unit is operable to generate a reflectivity profile which has a first axis including reflectivity at a single wavelength and a second axis including predetermined overlay offset.

5. The system of claim 4, wherein the generating the reflectivity profile includes:

plotting the first reflectivity;

generating a first line fitted to the plotted first reflectivity;

plotting the second reflectivity; and

generating a second line fitted to the plotted second reflectivity.

6. The system of claim 5, wherein determining the actual overlay offset of zero includes determining a value on the second axis where the first line and the second line intersect, wherein the value provides the predetermined overlay offset that corresponds to the actual overlay offset of zero.

7. The system of claim 1, wherein the radiation source and the detector are in-situ with a lithography system.

8. The system of claim 1, wherein the radiation source, the detector, and the calculation unit are in-situ with a lithography system.

21. The system of claim 1, wherein:

the detector is operable to detect a third reflectivity of the irradiated overlay offset measurement target; and

the calculation unit is operable to determine the overlay offset using the detected first, second, and third reflectivity by determining a predetermined overlay offset amount which provides an actual offset of zero.

9. An apparatus comprising a non-transitory computer-readable medium encoded with a computer program that, when executed performs the steps of:

receiving a first reflectivity measurement at a single irradiated wavelength;

receiving a second reflectivity measurement at the single irradiated wavelength;

generating a reflectivity profile which has a first axis of reflectivity at the single wavelength and a second axis of predetermined overlay offset, wherein the generating the reflectivity profile includes;

plotting the first reflectivity measurement;

generating a first line fitted to the plotted first reflectivity measurement;

plotting the second reflectivity measurement; and

generating a second line fitted to the plotted second reflectivity measurement; and

calculating an overlay offset for a first layer of a semiconductor wafer and a second layer of a semiconductor wafer from the reflectivity profile.

10. The apparatus of claim 9, wherein the calculating the overlay offset includes determining a value on the second axis where the first line and the second line intersect, wherein the value provides a predetermined overlay offset that corresponds to an actual overlay offset of zero.

11. The apparatus of claim 9, wherein the first reflectivity measurement is associated with a first feature on the first layer of the semiconductor wafer and a second feature on the second layer of the semiconductor wafer.

12. The apparatus of claim 11, wherein the second reflectivity measurement is associated with a third feature on the first layer of the semiconductor wafer and fourth feature on the second layer of the semiconductor wafer.

13. The apparatus of claim 9, further comprising:

receiving a third reflectivity measurement, wherein the third reflectivity measurement is associated with a fifth feature located on the first layer and a sixth feature located on the second layer, wherein the generating the reflectivity profile further includes plotting the third reflectivity measurement, and wherein the generating the first line includes fitting the first line to the plotted third reflectivity measurement.

14. The apparatus of claim 9, wherein the first reflectivity measurement is associated with a first feature on the first layer of the semiconductor wafer and a second feature on the second layer of the semiconductor wafer, the first and second feature having a first predetermined overlay offset, and wherein the second reflectivity measurement is associated with a third feature on the first layer of the semiconductor wafer and fourth feature on the second layer of the semiconductor wafer, the third and fourth feature having a second predetermined overlay offset different than the first predetermined overlay offset.

15. The apparatus of claim 14, wherein the second predetermined overlay offset is different in value and in direction than the first predetermined overlay offset.

16. The apparatus of claim 9, wherein the calculating the predetermined overlay offset provides an actual overlay offset of approximately zero and includes selecting a predetermined overlay offset that provides for greatest reflectivity.

22. The apparatus of claim 9, wherein generating the reflectivity profile further includes:

plotting the first reflectivity measurement;

plotting the second reflectivity measurement; and

wherein the first line is fitted to the plotted first reflectivity measurement and the second line is fitted to the plotted second reflectivity measurement.

17. A computer readable medium comprising non-transitory computer-readable instructions to determine an overlay offset measurement in semiconductor manufacturing, the computer-readable instructions comprising instructions to perform the steps to:

receive a first reflectivity measurement;

receive a second reflectivity measurement;

receive a third reflectivity measurement, wherein each of the first, second and third reflectivity measurements are measurements taken at a single wavelength of radiation of features on a first and second layer of a semiconductor substrate having different predetermined offsets; and

calculate an overlay offset for the first layer and the second layer by determining a greatest reflectivity.

18. The non-transitory computer readable medium of claim 17, further comprising instructions to perform the steps to:

generate a reflectivity profile which has a first axis including reflectivity at the single wavelength and a second axis including predetermined overlay offset, wherein the generating the reflectivity profile includes;

plotting the first reflectivity measurement;

plotting the third reflectivity measurement;

generating a first line fitted to the plotted first reflectivity measurement and the third reflectivity measurement;

and

plotting the second reflectivity measurement; and

generating a second line fitted to the plotted second reflectivity measurement.

19. The non-transitory computer readable medium of claim 18, wherein the calculating the overlay offset-includes using the reflectivity profile to determine the greatest reflectivity.

20. The non-transitory computer readable medium of claim 18, wherein the calculating the overlay offset includes determining a value on the second axis where the first line and the second intersect, wherein the value provides a predetermined overlay offset that corresponds to an actual overlay offset of zero.

23. The non-transitory computer readable medium of claim 18, wherein generating the reflectivity profile further includes:

plotting the first reflectivity measurement;

plotting the third reflectivity measurement;

plotting the second reflectivity measurement; and

wherein the first line is fitted to the plotted first reflectivity measurement and third reflective measurement; and

wherein the second line is fitted to the plotted second reflectivity measurement.