Method and apparatus for accurate calibration of a reflectometer by using a relative reflectance measurement

• US 20070181794A1
• Filed: 05/05/2006
• Published: 08/09/2007
• Est. Priority Date: 08/11/2004
• Status: Active Grant

• Current Assignee: Bruker Technologies Ltd. (Bruker Corporation)
• Original Assignee: Metrosol Inc. (Bruker Corporation)
• Inventors: Walsh, Phillip, Harrison, Dale
• Granted Patent: US 7,282,703 B2
• Time in Patent Office: Days
• US Class Current: 250/252.100
• CPC Class Codes: G01D 5/00 Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable G01D3/00 takes precedence; specially adapted for apparatus giving results other than momentary value of variable G01D1/00
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction
• CPC Class Codes: G01N 21/33 using ultraviolet light G01N21/39 takes precedence
• CPC Class Codes: G01N 21/55 Specular reflectivity

Abstract

A reflectometer calibration technique is provided that may include the use of two calibration samples in the calibration process. Further, the technique allows for calibration even in the presence of variations between the actual and assumed properties of at least one or more of the calibration samples. In addition, the technique utilizes a ratio of the measurements from the first and second calibration samples to determine the actual properties of at least one of the calibration samples. The ratio may be a ratio of the intensity reflected from the first and second calibration samples. The samples may exhibit relatively different reflective properties at the desired wavelengths. In such a technique the reflectance data of each sample may then be considered relatively decoupled from the other and actual properties of one or more of the calibration samples may be calculated. The determined actual properties may then be utilized to assist calibration of the reflectometer.

Claims

1. A method of calibrating a system that obtains reflectance data, comprising:

obtaining reflectance data from a first calibration sample;

obtaining reflectance data from a second calibration sample, wherein exact properties of the at least one of the first and second calibration samples may vary from assumed properties of the calibration samples and wherein the reflective properties of the first and second calibration samples differ; and

utilizing a ratio based upon the data obtained from the first calibration sample and the data obtained from the second calibration sample in order to assist in calibrating the system.

2. The method of claim 1, wherein a first set of reflectance data is collected from the first calibration sample, the first calibration sample having a calibration error function in a first wavelength region in which calibration is desired and a second set of reflectance data is collected from the second calibration samples, the second calibration sample having less spectral features as compared to the standard sample in the first wavelength region.

3. The method of claim 2, wherein the first calibration sample has a thicker oxide as compared to a thinner oxide on the second calibration sample.

4. The method of claim 3, wherein the first calibration sample comprises an SiO2/Si structure and the second calibration sample comprises an SiO2/Si structure.

6. The method of claim 1, wherein the reflectance data from the first calibration sample is decoupled from the reflectance data from the second calibration sample.

7. The method of claim 6, wherein the first calibration sample has a thicker oxide as compared to a thinner oxide on the second calibration sample.

10. The method of claim 1, wherein the first calibration sample has a thicker oxide as compared to a thinner oxide on the second calibration sample.

11. The method of claim 10, wherein the first calibration sample comprises an SiO2/Si structure and the second calibration sample comprises an SiO2/Si structure.

13. The method of claim 10, wherein the reflectance properties of the first and second calibration samples are decoupled from each other such that actual physical properties of at least one of the first and second calibration samples may be calculated based upon the obtained reflectance intensity data of the first and second calibration samples.

16. The method of claim 1, wherein the data obtained from the first calibration sample is intensity data and the data obtained from the second calibration sample is intensity data.

5. A method of calibrating a system that obtains reflectance data, comprising:

obtaining reflectance data from a first calibration sample;

obtaining reflectance data from a second calibration sample, wherein exact properties of the at least one of the first and second calibration samples may vary from assumed properties of the calibration samples and wherein the reflective properties of the first and second calibration samples differ; and

utilizing a ratio based upon the data obtained from the first calibration sample and the data obtained from the second calibration sample in order to assist in calibrating the system,

wherein a first set of reflectance data is collected from the first calibration sample, the first calibration sample having a calibration error function in a first wavelength region in which calibration is desired and a second set of reflectance data is collected from the second calibration sample, the second calibration sample having less spectral features as compared to the standard sample in the first wavelength region,

wherein the first calibration sample has a thicker oxide as compared to a thinner oxide on the second calibration sample,

wherein the first calibration sample comprises an SiO2/Si structure and the second calibration sample comprises an SiO2/Si structure, and

wherein the thinner oxide on the second calibration sample is a native oxide film.

8. A method of calibrating a system that obtains reflectance data, comprising:

obtaining reflectance data from a first calibration sample;

obtaining reflectance data from a second calibration sample, wherein exact properties of the at least one of the first and second calibration samples may vary from assumed properties of the calibration samples and wherein the reflective properties of the first and second calibration samples differ; and

utilizing a ratio based upon the data obtained from the first calibration sample and the data obtained from the second calibration sample in order to assist in calibrating the system,

wherein the reflectance data from the first calibration sample is decoupled from the reflectance data from the second calibration sample,

wherein the first calibration sample has a thicker oxide as compared to a thinner oxide on the second calibration sample, and

wherein the thinner oxide on the second calibration sample is a native oxide.

9. The method of claim 8, wherein the first calibration sample comprises an SiO2/Si structure and the second calibration sample comprises an SiO2/Si structure.

12. A method of calibrating a system that obtains reflectance data, comprising:

obtaining reflectance data from a first calibration sample;

obtaining reflectance data from a second calibration sample, wherein exact properties of the at least one of the first and second calibration samples may vary from assumed properties of the calibration samples and wherein the reflective properties of the first and second calibration samples differ; and

utilizing a ratio based upon the data obtained from the first calibration sample and the data obtained from the second calibration sample in order to assist in calibrating the system,

wherein the first calibration sample has a thicker oxide as compared to a thinner oxide on the second calibration sample,

wherein the first calibration sample comprises an SiO2/Si structure and the second calibration sample comprises an SiO2/Si structure, and

wherein the second calibration sample is a spectrally featureless reference sample.

14. (canceled)

15. A method of calibrating a system that obtains reflectance data, comprising:

obtaining reflectance data from a first calibration sample;

obtaining reflectance data from a second calibration sample, wherein exact properties of the at least one of the first and second calibration samples may vary from assumed properties of the calibration samples and wherein the reflective properties of the first and second calibration samples differ; and

utilizing a ratio based upon the data obtained from the first calibration sample and the data obtained from the second calibration sample in order to assist in calibrating the system,

wherein the utilizing step further comprises;

configuring a calibration routine to utilize a first set of reflectance data from the first calibration sample and to provide a first calibration of the system based at least in part upon the first set of reflectance data; and

configuring the calibration routine to utilize a second set of reflectance data from the second calibration sample, the second set of reflectance data having less features than the first set of reflectance data.

17. A method of calibrating a system that obtains reflectance data comprising:

obtaining reflectance data from a first calibration sample;

obtaining reflectance data from a second calibration sample, wherein exact properties of the at least one of the first and second calibration samples may vary from assumed properties of the calibration samples and wherein the reflective properties of the first and second calibration samples differ; and

utilizing a ratio based upon the data obtained from the first calibration sample and the data obtained from the second calibration sample in order to assist in calibrating the system

wherein the data obtained from the first calibration sample is intensity data and the data obtained from the second calibration sample is intensity data, and

wherein a reflectance ratio is obtained from the intensity data of the first and second calibration samples.

18. The method of claim 17, wherein a source intensity profile is obtained through use of the reflectance ratio and the reflectance of a unknown sample is calibrated by use of the source intensity profile.