Method of Assessing a Model of a Substrate, an Inspection Apparatus and a Lithographic Apparatus

• US 20110026032A1
• Filed: 03/30/2009
• Published: 02/03/2011
• Est. Priority Date: 04/09/2008
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Ebert, Martin, Den Boef, Arie Jeffrey, Cramer, Hugo Augustinus Joseph, Van De Kerkhof, Marcus Adrianus, Pellemans, Henricus Petrus Maria
• Granted Patent: US 8,830,472 B2
• Time in Patent Office: Days
• US Class Current: 356/446
• CPC Class Codes: G01N 2021/8845 Multiple wavelengths of illumination or detection
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/95607 using a comparative method
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness

Abstract

A method of assessing a model of a substrate is presented. A scatterometry measurement is taken using radiation at a first wavelength. The wavelength of the radiation is then changed and a further scatterometry measurement taken. If the scatterometry measurements are consistent across a range of wavelengths then the model is sufficiently accurate. However, if the scatterometry measurements change as the wavelength changes then the model of the substrate is not sufficiently accurate.

Claims

1. A method comprising:

taking a first scatterometry measurement of a substrate using radiation having known characteristics, the radiation having a first characteristic value;

determining a value of a characteristic of a feature of the substrate or a first residual using the first scatterometry measurement;

taking a second scatterometry measurement using the radiation having a second characteristic value;

determining a second value of the characteristic of the feature or a second residual using the second scatterometry measurement; and

comparing the first value and the second value of the characteristic of the feature or the first residual and the second residual to determine an accuracy of a model.

2. The method according to claim 1, further comprising changing a characteristic of the radiation to a third value.

3. The method according to claim 1, further comprising:

taking a third scatterometry measurement using the radiation having a third characteristic value; and

determining a third value of the characteristic of the feature using the third scatterometry measurement;

wherein the comparing compares the first, second and third values of the characteristic of the feature.

4. The method according to claim 3, further comprising changing the characteristic of the radiation to a fourth value.

5. The method according to claim 1 any one of the preceding claims, wherein the radiation characteristic to be changed is a wavelength of the radiation.

6. The method according to claim 1, wherein the radiation characteristic to be changed is a polarization of the radiation.

7. The method according to claim 1, wherein the radiation characteristic to be changed is an angle of incidence on the substrate.

8. The method according to claim 1, wherein the radiation characteristic to be changed is an illumination mode of the radiation.

9. The method according to claim 1, wherein the comparing comprises determining whether the second value of the characteristic of the feature is within a predetermined range of the first value.

10. (canceled)

11. An inspection apparatus comprising:

a radiation projector configured to project radiation onto a substrate, the radiation having a characteristic with a plurality of values;

a high numerical aperture lens; and

a detector configured to detect the radiation reflected from a surface of the substrate,

wherein the detector is configured to separate the detected radiation into a plurality of sub-divisions, the radiation of each sub-division having a different value for the characteristic.

12. The inspection apparatus according to claim 11, wherein the characteristic which differs between the sub-divisions is a wavelength.

13. The inspection apparatus according to claim 11, further comprising:

an imaging spectrometer configured to separate the detected radiation into a plurality of sub-divisions, the radiation of each sub-division having a different value for the characteristic.

14. (canceled)

15. (canceled)

16. A lithographic apparatus comprising:

an illumination system arranged to illuminate a pattern;

a projection system arranged to project an image of the pattern on to a substrate; and

an inspection apparatus configured to measure a target on the substrate, the inspection apparatus comprising,

a radiation projector configured to project radiation onto the substrate, the radiation having a characteristic with a plurality of valuesl

a high numerical aperture lensl and

a detector configured to detect the radiation reflected from a surface of the substratel

wherein the detector is configured to separate the detected radiation into a plurality of sub-divisions, the radiation of each sub-division having a different value for the characteristic.

17. The inspection apparatus according to claim 16, wherein the characteristic which differs between the sub-divisions is a wavelength.

18. The inspection apparatus according to claim 16, further comprising:

an imaging spectrometer configured to separate the detected radiation into a plurality of subdivisions, the radiation of each sub-division having a different value for the characteristic.

19. (canceled)

20. (canceled)

21. (canceled)