Optical measuring methods and system

Patent metadata

Field	Value
Publication number	US-9417180-B2
Application number	US-201514601407-A
Country	US
Kind code	B2
Filing date	Jan 21, 2015
Priority date	Jun 13, 2014
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

In an optical measuring method, a reflected light from a structure on a substrate is detected by a measuring tool to obtain a raw spectrum. The raw spectrum in a wavelength range having spectrum sensitivity to process variation is analyzed to determine a process variation of an actual process performed on the substrate. The raw spectrum is corrected according to a spectrum offset for the measuring tool which is determined based on the process variation.

First claim

What is claimed is:

1. An optical measuring method, comprising:
detecting a reflected light from a structure on a substrate by a measuring tool to obtain a raw spectrum;
analyzing the raw spectrum to determine a wavelength range having spectrum sensitivity to process variation that is greater than spectrum sensitivity to tool variation;
analyzing the raw spectrum in the wavelength range to determine a process variation of an actual process performed on the substrate; and
correcting the raw spectrum according to a spectrum offset for the measuring tool which is determined based on the process variation.

2. The method of claim 1 , wherein obtaining the raw spectrum comprises obtaining an amplitude ratio (tan(Ψ)) or phase difference (Δ) spectrum of the reflected light using spectroscopic ellipsometry.

3. The method of claim 1 , wherein the raw spectrum in the wavelength range represents the process variation between the actual process and a reference process.

4. The method of claim 1 , wherein the spectrum offset for the measuring tool is determined as a difference of a spectrum of the measuring tool with reference to a spectrum of a reference tool or a difference of the spectrum of the measuring tool with reference to an average spectrum for a plurality of measuring tools.

5. The method of claim 1 , further comprising calculating a profile of the structure from the corrected spectrum using a modeling technique.

6. The method of claim 5 , further comprising using the calculated profile of the structure to perform a process control.

7. The method of claim 5 , wherein the profile of the structure comprises a thickness of the structure.

8. The method of claim 1 , wherein the structure comprises a periodic grating.

9. An optical measuring method, comprising:
obtaining raw spectrums from a plurality of substrates by respective measuring tools;
analyzing the raw spectrums to determine a wavelength range having spectrum sensitivity to process variation that is greater than spectrum sensitivity to tool variation;
analyzing the raw spectrums in the wavelength range to determine process variations between processes performed on the substrates;
determining a spectrum offset for each of the measuring tools based on the process variations; and
correcting the raw spectrums according to the respective spectrum offsets.

10. The method of claim 9 , wherein obtaining each raw spectrum comprises obtaining an amplitude ratio (tan(Ψ)) or phase difference (Δ) spectrum of a reflected light from a structure on the substrate using spectroscopic ellipsometry.

11. The method of claim 9 , further comprising analyzing the spectrums representing the process variations to determine a spectrum of a reference process, after determining the process variations between the processes performed on the substrates.

12. The method of claim 11 , further comprising analyzing the spectrums for the measuring tools in the reference process to determine a spectrum of a reference tool.

13. The method of claim 12 , wherein determining the spectrum offset for the measuring tool comprises determining a difference of the spectrum of the measuring tool with reference to the spectrum of the reference tool or a difference of the spectrum of the measuring tool with reference to an average spectrum for all of the measuring tools as the spectrum offset.

14. The method of claim 9 , further comprising calculating a profile of a structure on one of the substrates from the respective corrected spectrum using a modeling technique.

15. The method of claim 14 , further comprising using the calculated profile of the structure to perform a process control.

16. An optical measuring system, comprising:
an optical measuring tool configured to detect reflected light from a structure on a substrate to obtain a raw spectrum; and
a control module configured to analyze the raw spectrum to determine a wavelength range having spectrum sensitivity to process variation that is greater than spectrum sensitivity to tool variation, to analyze the raw spectrum in the wavelength range to determine a process variation of an actual process performed on the substrate, and to produce a corrected spectrum according to a spectrum offset for the measuring tool which is determined based on the process variation.

17. The system of claim 16 , wherein the optical measuring tool comprises a spectroscopic ellipsometer that is configured to generate a reflection ratio spectrum of components into which light incident upon the substrate is decomposed.

18. The system of claim 16 , wherein the control module comprises a calculator configured to calculate a profile of the structure from the corrected spectrum using a modeling technique.

19. The system of claim 18 , wherein the modeling technique comprises a rigorous coupled wave analysis (RCWA).

20. The system of claim 18 , wherein the control module is configured to utilize the profile of the structure for process control.

Assignees

• Samsung Electronics Co Ltd

Inventors

• Seo Dong-Min
• Park Jang-Ik

Classifications

• G01N21/211 Primary

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

• G01N2021/213

  Spectrometric ellipsometry · CPC title