Optical measuring system and method of measuring critical size

Patent metadata

Field	Value
Publication number	US-9322640-B2
Application number	US-201313961305-A
Country	US
Kind code	B2
Filing date	Aug 7, 2013
Priority date	Aug 7, 2012
Publication date	Apr 26, 2016
Grant date	Apr 26, 2016

Abstract

Optical measuring systems for measuring geometrical parameters of nano-objects and methods of measuring a critical size (CS) are provided. The optical method of measuring the CS includes selecting parameters of an optic scheme and an illumination condition; recording a set of nanostructure images corresponding to various wavelengths with various defocusing levels of scattered radiation; calculating a plurality of sets of images of a nanostructure with various defocusing levels, corresponding to various wavelengths of the scattered radiation with CS values within a known range; and comparing a set of measured images of the nanostructure with the sets of the calculated images and determining a best approximate value of the CS values.

First claim

What is claimed is:

1. An optical measuring system for measuring a critical size of a nanostructure, the optical measuring system comprising:
an illumination module configured to illuminate a sample with the nanostructure that is an examined object;
an optical image generating module configured to generate an optical image of the nanostructure;
a defocusing module configured to defocus the optical image;
a calculation module configured to calculate a set of images with various defocusing levels;
an adjusting and monitoring module configured to adjust and monitor parameters of an optic scheme and illumination conditions with respect to the set of images with various defocusing levels, and transmit, to the calculation module, the parameters of the optic scheme and the illumination conditions;
a recording module configured to record the set of images with various defocusing levels; and
a comparison module configured to compare the recorded and defocused images with pre-calculated and defocused images.

2. The optical measuring system of claim 1 , wherein a defocusing level A of the defocusing module depends on a wavelength and the defocusing module defocuses the optical image to comply with a condition 0<Δ<5*λ/(NA) 2 , where λ denotes an average wavelength of illuminating radiation and NA denotes a numerical aperture of a lens.

3. The optical measuring system of claim 1 , wherein the illumination module comprises a light source with an adjustable wavelength, an optical illumination system, and a lens.

4. The optical measuring system of claim 3 , wherein the adjustable wavelength of the light source is adjustable within a wavelength range of about 300 nm to about 800 nm.

5. The optical measuring system of claim 4 , wherein the recording module comprises a detector and the light source with the adjustable wavelength, and is configured to continuously record defocused images of the nanostructure while adjusting the wavelength of the light source.

6. The optical measuring system of claim 4 , wherein the recording module comprises a detector, a disperse device, and a wideband light source, and is configured to simultaneously record defocused images of the nanostructure by using spatial spectral resolution within the wavelength range of the light source.

7. The optical measuring system of claim 1 , wherein the illumination module comprises a light source with a spectrum range of wavelengths of about 300 nm to about 800 nm, an illumination optical system, and a lens.

8. The optical measuring system of claim 1 , wherein the optical image generating module comprises a microscope optical system.

9. The optical measuring system of claim 8 , wherein the optical image generating module comprises a lens, a beam splitter, and a pipe lens.

10. The optical measuring system of claim 9 , wherein a function of the defocusing module depending on a wavelength is performed by the pipe lens of the optical image generating module by using a chromatic aberration phenomenon.

11. The optical measuring system of claim 9 , wherein a function of the defocusing module depending on a wavelength is performed by the lens of the optical image generating module by using the chromatic aberration phenomenon.

12. The optical measuring system of claim 1 , wherein the defocusing module comprises two identical parallel diffraction gratings and a mirror, wherein the two diffraction gratings and the mirror allow setting an optical propagation difference depending on a wavelength.

13. The optical measuring system of claim 1 , wherein the adjusting and monitoring module performs at least one of adjusting, measuring, and monitoring the parameters of the optic scheme and the illumination conditions.

14. A method of measuring a critical size, the method comprising:
selecting parameters of an optic scheme and an illumination condition;
recording a set of nanostructure images corresponding to various wavelengths with various defocusing levels of scattered radiation;
calculating a plurality of sets of images of a nanostructure with various defocusing levels, corresponding to various wavelengths of the scattered radiation with critical size (CS) values within a known range; and
comparing a set of measured images of the nanostructure with the sets of the calculated images and determining a best approximate value of the CS values.

15. The method of claim 14 , wherein at least one of the parameters of the optic scheme and the illumination condition is selected from the group consisting of a spatial frequency spectrum of illumination, a temporal illumination spectrum, a direction of a polarization vector, a numerical aperture of a lens, a defocusing level, a dependence of the defocusing level on the wavelength.

16. The method of claim 14 , wherein the recording comprises sequentially recording defocused images of the nanostructure \while adjusting a wavelength of a light source.

17. The method of claim 14 , wherein the recording comprises simultaneously recording defocused images of the nanostructure by using spatial spectral resolution within a wavelength range of a light source with a wideband spectrum.

18. The method of claim 14 , wherein the determining the best approximate value of the CS values comprises determining the best approximate value of the CS values by calculating a library of images and comparing the set of the measured images of the nanostructure with corresponding sets of the calculated images from the library.

19. The method of claim 14 , wherein the comparing the set of measured images of the nanostructure with the corresponding sets of the calculated images comprises calculating curves of a focus-metric depending on a wavelength when images generated at various wavelengths of the scattered radiation and having different levels of defocusing are identical to parameters depending on the defocusing level, the wavelength and a topology of the nanostructure.

20. The method of claim 14 , wherein the comparing the set of measured images of the nanostructure with the corresponding sets of the calculated images comprises calculating curves of a focus-metric depending on a wavelength.

Assignees

• Samsung Electronics Co Ltd
• Samsing Electronics Co Ltd

Inventors

• Koptyaev Sergey Nikolaevich
• Ryabko Maxim Vladimirovich
• Shcherbakov Alexander Vyacheslavovich
• Lantsov Alexey Dmitrievich

Classifications

• G01B2210/56

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

• G01B11/02 Primary

  for measuring length, width or thickness (G01B11/08 takes precedence) · CPC title