Automated process control using optical metrology and photoresist parameters

• US 7,567,353 B2
• Filed: 03/28/2007
• Issued: 07/28/2009
• Est. Priority Date: 03/28/2007
• Status: Active Grant

• Current Assignee: Tokyo Electron Limited
• Original Assignee: Tokyo Electron Limited
• Inventors: Bischoff, Joerg, Hetzer, David, Madriaga, Manuel
• Primary Examiner(s): Pham; Hoa Q
• Application Number:
  US11/729,700
• Publication Number:
  US 20080241975A1
• Time in Patent Office: 853 Days
• Field of Search: 3562371-2375, 356/601, 356/625, 356/636
• US Class Current: 356/636
• CPC Class Codes: G01N 21/4788 Diffraction for sizing particles G01N15/0205
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• 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

To control a photolithography cluster using optical metrology, a structure is fabricated on a wafer using the photolithography cluster. A measured diffraction signal off the structure is obtained. The measured diffraction signal is compared to a simulated diffraction signal. The simulated diffraction signal is associated with one or more values of one or more photoresist parameters. The one or more photoresist parameters characterize behavior of photoresist when the photoresist undergoes processing steps in the photolithography cluster. The simulated diffraction signal was generated using one or more values of one or more profile parameters. The one or more values of the one or more profile parameters used to generate the simulated diffraction signal were derived from the one or more values of the one or more photoresist parameters associated with the simulated diffraction signal. If the measured diffraction signal and the simulated diffraction signal match, then one or more values of one or more photoresist parameters used in the photolithography cluster are determined to be the one or more values of the one or more photoresist parameters associated with the matching simulated diffraction signal. One or more process parameters or equipment settings of the photolithography cluster are adjusted based on the one or more values of the one or more photoresist parameters.

Claims

1. A method of controlling a photolithography cluster using optical metrology, the method comprising:

a) fabricating a structure on a wafer using a photolithography cluster;

b) obtaining a measured diffraction signal off the structure;

c) comparing the measured diffraction signal to a simulated diffraction signal, wherein the simulated diffraction signal is associated with one or more values of one or more photoresist parameters, wherein the one or more photoresist parameters characterize behavior of photoresist when the photoresist undergoes processing steps in the photolithography cluster, wherein the simulated diffraction signal was generated using one or more values of one or more profile parameters, and wherein the one or more values of the one or more profile parameters used to generate the simulated diffraction signal were derived from the one or more values of the one or more photoresist parameters associated with the simulated diffraction signal;

d) if the measured diffraction signal and the simulated diffraction signal match, then determining one or more values of one or more photoresist parameters used in the photolithography cluster to be the one or more values of the one or more photoresist parameters associated with the matching simulated diffraction signal; and

e) adjusting one or more process parameters or equipment settings of the photolithography cluster based on the one or more values of the one or more photoresist parameters determined in d).

2. The method of claim 1, further comprising:

if the measured diffraction signal and the simulated diffraction signal compared in c) do not match, comparing the measured diffraction signal to another simulated diffraction signal associated with one or more values of one or more photoresist parameters that are different than the one or more values of the one or more photoresist parameters of the simulated diffraction signal that did not match the measured diffraction signal.

3. The method of claim 2, wherein the simulated diffraction signal and the another simulated diffraction signal are stored in a library having a plurality of simulated diffraction signals and a plurality of values of one or more photoresist parameters associated with the plurality of simulated diffraction signals.

4. The method of claim 2, wherein the another simulated diffraction signal was generated after the measured diffraction signal and the simulated diffraction signal compared in c) are determined not to match.

5. The method of claim 1, wherein the one or more photoresist parameters comprise change of inhibitor concentration, surface inhibition, diffusion during the photoresist baking process, development rate parameters, labile absorptivity, non-labile absorptivity, and/or intrinsic sensitivity of photoresist.

6. The method of claim 1, further comprises:

prior to c)-e), determining a correlation between the one or more photoresist parameters and the one or more profile parameters;

prior to c)-e), obtaining one or more values for the one or more photoresist parameters; and

prior to c)-e), converting the one or more values for the one or more photoresist parameters to one or more values for the one or more profile parameters using the determined correlation, wherein the simulated diffraction signal is generated using the one or more values for the one or more profile parameters.

7. The method of claim 1, further comprises:

prior to c)-e), selecting a first set of one or more values for the one or more photoresist parameters;

prior to c)-e), fabricating one or more photoresist structures utilizing the one or more values for the one or more photoresist parameters;

prior to c)-e), obtaining a first set of one or more values for the one or more profile parameters from the one or more photoresist structures;

prior to c)-e), training a machine learning system using the first set of one or more values for the one or more photoresist parameters as inputs to the machine learning system and the first set of one or more values for the one or more profile parameters as the expected outputs of the machine learning system; and

prior to c)-e), after training the machine learning system, inputting a second set of one or more values for the one or more photoresist parameters into the machine learning system to obtain a second set of one or more values for the one or more profile parameters as outputs of the machine learning system, wherein the simulated diffraction signal is generated using the second set of one or more values for the one or more profile parameters.

8. The method of claim 1, further comprising:

adjusting one or more process parameters or equipment settings of a fabrication cluster based on the one or more values of the one or more photoresist parameters determined in d).

9. The method of claim 8, wherein the fabrication cluster processes wafers prior to the photolithography cluster.

10. The method of claim 8, wherein the fabrication cluster processes wafers subsequent to the photolithography cluster.

11. A computer-readable storage medium containing computer-executable instructions to control a photolithography cluster using optical metrology, comprising instructions for:

a) obtaining a measured diffraction signal off a structure fabricated on a wafer using a photolithography cluster;

b) comparing the measured diffraction signal to a simulated diffraction signal, wherein the simulated diffraction signal is associated with one or more values of one or more photoresist parameters, wherein the one or more photoresist parameters characterize behavior of photoresist when the photoresist undergoes processing steps in the photolithography cluster, wherein the simulated diffraction signal was generated using one or more values of one or more profile parameters, and wherein the one or more values of the one or more profile parameters used to generate the simulated diffraction signal were derived from the one or more values of the one or more photoresist parameters associated with the simulated diffraction signal;

c) if the measured diffraction signal and the simulated diffraction signal match, then determining one or more values of one or more photoresist parameters used in the photolithography cluster to be the one or more values of the one or more photoresist parameters associated with the matching simulated diffraction signal; and

d) adjusting one or more process parameters or equipment settings of the photolithography cluster based on the one or more values of the one or more photoresist parameters determined c).

12. The computer-readable storage medium of claim 11, further comprising instructions for:

if the measured diffraction signal and the simulated diffraction signal compared in b) do not match, comparing the measured diffraction signal to another simulated diffraction signal associated with one or more values of one or more photoresist parameters that are different than the one or more values of the one or more photoresist parameters of the simulated diffraction signal that did not match the measured diffraction signal.

13. The computer-readable storage medium of claim 12, wherein the simulated diffraction signal and the another simulated diffraction signal are stored in a library having a plurality of simulated diffraction signals and a plurality of values of one or more photoresist parameters associated with the plurality of simulated diffraction signals.

14. The computer-readable storage medium of claim 12, wherein the another simulated diffraction signal was generated after the measured diffraction signal and the simulated diffraction signal compared in b) are determined not to match.

15. The computer-readable storage medium of claim 11, wherein the one or more photoresist parameters comprise change of inhibitor concentration, surface inhibition, diffusion during the photoresist baking process, development rate parameters, labile absorptivity, non-labile absorptivity, and/or intrinsic sensitivity of the photoresist.

16. The computer-readable storage medium of claim 11, further comprising:

adjusting one or more process parameters or equipment settings of a fabrication cluster based on the one or more values of the one or more photoresist parameters determined in c).

17. The computer-readable storage medium of claim 16, wherein the fabrication cluster processes wafers prior to the photolithography cluster.

18. The computer-readable storage medium of claim 16, wherein the fabrication cluster processes wafers subsequent to the photolithography cluster.

19. A system to control a photolithography cluster using optical metrology, the system comprising:

a photolithography cluster configured to perform a photolithographic process to fabricate a structure on a wafer;

an optical metrology system comprising;

a beam source and detector configured to measure a diffraction signal off the structure;

a processor connected to the beam source and detector, wherein the processor is configured to compare the measured diffraction signal to a simulated diffraction signal, wherein the simulated diffraction signal is associated with one or more values of one or more photoresist parameters, wherein the one or more photoresist parameters characterize behavior of photoresist when the photoresist undergoes processing steps in the photolithography cluster, wherein the simulated diffraction signal was generated using one or more values of one or more profile parameters, and wherein the one or more values of the one or more profile parameters used to generate the simulated diffraction signal were derived from the one or more values of the one or more photoresist parameters associated with the simulated diffraction signal; and

a metrology processor coupled to the optical metrology system and the photolithography cluster, wherein the metrology processor is configured to adjust one or more process parameters or equipment settings of the photolithography cluster based on the one or more values of the one or more photoresist parameters determined by the processor of the optical metrology system.

20. The system of claim 19, further comprising:

a library having a plurality of simulated diffraction signals and a plurality of values of one or more photoresist parameters associated with the plurality of simulated diffraction signals.

21. The system of claim 19, wherein the one or more photoresist parameters comprise change of inhibitor concentration, surface inhibition, diffusion during the photoresist baking process, development rate parameters, labile absorptivity, non-labile absorptivity, and/or intrinsic sensitivity of the photoresist.

22. The system of claim 19, further comprising:

a fabrication cluster connected to the metrology processor, wherein the metrology processor is configured to adjust one or more process parameters or equipment settings of the fabrication cluster based on the determined one or more values of the one or more photoresist parameters.

23. The system of claim 22, wherein the fabrication cluster processes wafers prior to the photolithography cluster.

24. The system of claim 22, wherein the fabrication cluster processes wafers subsequent to the photolithography cluster.