Metrology system calibration refinement

Patent metadata

Field	Value
Publication number	US-9857291-B2
Application number	US-201414277898-A
Country	US
Kind code	B2
Filing date	May 15, 2014
Priority date	May 16, 2013
Publication date	Jan 2, 2018
Grant date	Jan 2, 2018

Abstract

Methods and systems for matching measurement spectra across one or more optical metrology systems are presented. The values of one or more system parameters used to determine the spectral response of a specimen to a measurement performed by a target metrology system are optimized. The system parameter values are optimized such that differences between measurement spectra generated by a reference system and the target system are minimized for measurements of the same metrology targets. Methods and systems for matching spectral errors across one or more optical metrology systems are also presented. A trusted metrology system measures the value of at least one specimen parameter to minimize model errors introduced by differing measurement conditions present at the time of measurement by the reference and target metrology systems. Methods and systems for parameter optimization based on low-order response surfaces are presented to reduce the compute time required to refine system calibration parameters.

First claim

What is claimed is:

1. A method comprising:
providing a first amount of illumination light to one or more structures disposed on a semiconductor wafer, the one or more structures having an unknown spectral response, the first amount of illumination light provided by an illuminator of a reference metrology system;
detecting a first plurality of intensities of light from the one or more structures in response to the first amount of illumination light provided to the semiconductor wafer, the detected first plurality of intensities comprising a first amount of raw measurement data, the first plurality of intensities of light detected by a spectrometer of the reference metrology system;
determining a first spectral response measurement of the one or more structures based at least in part on the first amount of raw measurement data and one or more system parameter values associated with the reference metrology system that provides the first amount of illumination light and detects the first amount of raw measurement data;
providing a second amount of illumination light to the one or more structures disposed on the semiconductor wafer, the second amount of illumination light provided by an illuminator of a target metrology system;
detecting a second plurality of intensities of light from the one or more structures in response to the second amount of illumination light provided to the semiconductor wafer, the detected second plurality of intensities comprising a second amount of raw measurement data, the second plurality of intensities of light detected by a spectrometer of the target metrology system;
determining values of one or more system parameters associated with the target metrology system that provides the second amount of illumination light and detects the second amount of raw measurement data such that an error function that includes a difference between the first spectral response measurement and a second spectral response measurement of the one or more structures measured by the target metrology system is minimized, wherein the second spectral response measurement is determined based at least in part on the second amount of raw measurement data detected by the target metrology system and the values of the one or more system parameters associated with the target metrology system, wherein at least one value of at least one of the one or more system parameter values associated with the target metrology system is different from at least one value of at least one of the one or more system parameter values associated with the reference metrology system; and
storing the values of the one or more system parameters of the target metrology system in a memory.

2. The method of claim 1 , wherein the target metrology system and the reference metrology system are spectroscopic ellipsometers.

3. The method of claim 1 , wherein the reference metrology system is a metrology system that performs the first spectral measurement of the one or more structures at a first time and the target metrology system is the metrology system that performs the second spectral measurement of the one or more structures at a second time after the first time.

4. The method of claim 1 , wherein the determining of the values of one or more system parameters associated with the target metrology system involves a regression analysis.

5. The method of claim 1 , further comprising:
determining an estimate of a structural parameter of the one or more structures based on a regression of a reference system measurement model on the first spectral measurement; and
determining an estimate of the structural parameter of the one or more structures based on a regression of a target system measurement model on the second spectral measurement, the target system measurement model including the values of the one or more system parameters of the target metrology system.

6. The method of claim 1 , wherein the first spectral measurement of the one or more structures includes spectral measurement data associated with any of multiple measurement sites, multiple measurement samples, multiple illumination wavelengths, and multiple measurement modalities.

7. The method of claim 1 , wherein the error function includes a weighted difference function including the first spectral measurement and a second spectral measurement of the one or more structures.

8. The method of claim 7 , wherein the weighted difference function is based on a measurement sensitivity to any of multiple measurement sites, multiple measurement samples, multiple illumination wavelengths, and multiple measurement modalities.

9. The method of claim 7 , wherein the weighted difference function is based on a measurement noise associated with any of multiple measurement sites, multiple measurement samples, multiple illumination wavelengths, and multiple measurement modalities.

10. The method of claim 1 , wherein the determining the values of the one or more system parameters associated with the target metrology system involves a response surface based optimization.

11. A metrology system comprising:
a first illuminator that provides a first amount of illumination light to one or more structures disposed on a semiconductor wafer, the one or more structures having an unknown spectral response;
a first spectrometer that detects a first plurality of intensities of light from the one or more structures in response to the first amount of illumination light provided to the semiconductor wafer, the detected first plurality of intensities comprising a first amount of raw measurement data;
a second illuminator that provides a second amount of illumination light to the one or more structures disposed on the semiconductor wafer;
a second spectrometer that detects a second plurality of intensities of light from the one or more structures in response to the second amount of illumination light provided to the semiconductor wafer, the detected second plurality of intensities comprising a second amount of raw measurement data; and
one or more computer systems configured to:
determine a first spectral response measurement of the one or more structures based at least in part on the first amount of raw measurement data and one or more system parameter values associated with a reference metrology system that includes the first illuminator and the first spectrometer;
determine values of one or more system parameters associated with a target metrology system that includes the second illuminator and the second spectrometer such that an error function that includes a difference between the first spectral response measurement and a second spectral response measurement of the one or more structures measured by the target metrology system is minimized, wherein the second spectral response measurement is determined based at least in part on the second amount of raw measurement data detected by the target metrology system and the values of the one or more system parameters associated with the target metrology system, wherein at least one value of at least one of the one or more system parameter values associated with the target metrology system is different from at least one value of at least one of the one or more system parameter values associated with the reference metrology system; and
store the values of the one or more system parameters of the target metrology system in a memory.

12. The metrology system of claim 11 , wherein the first spectral measurement of the one or more structures includes spectral measurement data associated with any of multiple measurement sites, multiple measurement samples, multiple illumination wavelengths, and multiple measurement modalities.

13.

Assignees

• Kla Tencor Corp

Inventors

• Kwak Hidong
• Lesoine John
• Sadiq Malik
• Wei Lanhua
• Krishnan Shankar
• Poslavsky Leonid
• Sushchik Mikhail M

Classifications

• G01N2021/213

  Spectrometric ellipsometry · CPC title

• G01N21/211 Primary

  Ellipsometry (optical thickness measurement G01B11/06) · CPC title

• G01N21/274

  Calibration, base line adjustment, drift correction · CPC title

• G01B2210/56

  Measuring geometric parameters of semiconductor structures, e.g. profile, critical dimensions or trench depth · CPC title

• G01N21/9501

  Semiconductor wafers (manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20) · CPC title