Rapid and accurate thin film measurement of individual layers in a multi-layered or patterned sample

• US 6,204,922 B1
• Filed: 12/11/1998
• Issued: 03/20/2001
• Est. Priority Date: 12/11/1998
• Status: Expired due to Term

• Current Assignee: Filmetrics, Inc. (KLA Corporation)
• Original Assignee: Filmetrics, Inc. (KLA Corporation)
• Inventors: Chalmers, Scott A.
• Primary Examiner(s): PHAM, HOA Q
• Application Number:
  US09/209,357
• Time in Patent Office: 830 Days
• Field of Search: 356/381, 356/382, 356/318, 356/326, 356/328, 451/5, 451/6
• US Class Current: 356/630
• CPC Class Codes: G01B 11/0616 of coating

Abstract

Methods and apparatus for measuring the thickness of at least one individual film added to, removed from, or within a sample, characterized by the use of a shift in a selected peak of thickness spectral data to estimate the thickness of the individual film.

Claims

1. A film measurement apparatus comprising:

a white light source configured to generate a light signal;

a first fiber optic cable connected to said light source to receive said light signal and further configured to direct said light signal onto a sample to obtain a reflected light signal having a plurality of wavelength components, each having an intensity;

a second fiber optic cable positioned to receive said reflected light signal;

a spectrometer configured to receive said reflected light signal from said second fiber optic cable, and derive therefrom a plurality of electrical signals, each representative of the intensity of a wavelength component of the reflected light;

a computer programmed to receive from said spectrometer said plurality of electrical signals, and determine therefrom the thickness of at least one film added to or removed from said sample, the film comprising a material having a refractive index, by;

obtaining data representative of the intensity of at least some of said wavelength components;

arranging said data so that it is a function of a variable equal to the refractive index of the material divided by wavelength;

determining the Power Spectral Density of the arranged data as a function of potential layer thickness;

detecting at least one peak in the Power Spectral Density, including a selected peak;

determining a shift in a selected peak upon, during, or after the addition of the layer to or the removal of the layer from the sample, the shift occurring in response to the addition or removal of the layer; and

providing as an estimate of the thickness of the layer in at least one region sampled by the illumination light a value derived from the shift in the selected peak of the Power Spectral Density, the estimate being derived without requiring details of any structure underlying or adjacent to the region.

6. The apparatus of any of claims 1, 2, or 5 in which the sample is a patterned sample.

7. The apparatus of any of claims 1, 2, or 5 in which the sample is a multi-layer sample.

2. A film measurement apparatus comprising:

a light source configured to generate a light signal;

a first optical director configured to receive said light signal and direct said light signal onto a sample to obtain a reflected light signal having a plurality of wavelength components, each having an intensity;

a second optical director configured to direct said reflected light signal;

an optical device configured to receive said reflected light signal from said second director, and derive therefrom a plurality of electrical signals, each representative of the intensity of a wavelength component of the reflected light;

an electronic device part of or distinct from the optical device configured to receive said plurality of electrical signals and convert them to numeric representations of the intensity of each detected wavelength component;

a computer programmed to receive said numeric representations, and determine therefrom the thickness of at least one film added to or removed from said sample by;

obtaining data representative of the intensity of at least some of said wavelength components;

performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness;

detecting at least one peak in the thickness spectral data, including a selected peak;

determining a shift in the selected peak upon, during, or after the addition of the layer to or removal of the layer from the sample, the shift occurring responsive to the addition or removal of the layer; and

providing as an estimate of the thickness of the layer in at least one region sampled by the illumination light a value derived from the shift of the selected peak of the thickness spectral data, the estimate being derived without requiring details of any structure underlying or adjacent to the region.

3. The apparatus of claim 2 in which the computer is configured to derive the Fourier Transform of the intensity data.

4. The apparatus of claim 2 in which the computer is programmed to derive the Power Spectral Density of the intensity data.

5. A film measurement apparatus comprising:

first means for directing a light signal onto a sample to obtain a reflected light signal having a plurality of wavelength components, each having an intensity;

second means for receiving said reflected light signal and deriving therefrom data representative of the intensity of at least some of the wavelength components of the reflected light;

third means for performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness; and

fourth means for detecting a shift in a selected peak of the thickness spectral data upon, during, or after the addition of a layer to or removal of the layer from the sample, the shift occurring responsive to the addition or removal of the layer, and directly estimating therefrom the thickness of the layer in at least one region thereof illuminated by the light without requiring details of any structure underlying or adjacent to the region.

8. A film measurement apparatus comprising:

a light source configured to generate a light signal;

a first optical director configured to receive said light signal and direct said light signal onto a sample to obtain a reflected light signal having a plurality of wavelength components, each having an intensity;

a second optical director configured to direct said reflected light signal;

an optical device configured to receive said reflected light signal from said second director, and derive therefrom a plurality of electrical signals, each representative of the intensity of a wavelength component of the reflected light;

an electronic device part of or distinct from the optical device configured to receive said plurality of electrical signals and convert them to numeric representations of the intensity of each detected wavelength component;

a transfer station having a window interfaced to a vacuum station for depositing new layers; and

a computer programmed to receive said numeric representations, and determine therefrom the thickness of at least one film added to or removed from said sample by;

obtaining data representative of the intensity of at least some of said wavelength components;

performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness;

detecting at least one peak in the thickness spectral data, including a selected peak;

determining a shift in the selected peak upon, during, or after the addition of the layer to or removal of the layer from the sample; and

providing as an estimate of the thickness of the layer in at least one region sampled by the illumination light a value derived from the shift of the selected peak of the thickness spectral data.

9. A computer program medium embodying a program of instructions executable by computer to perform a method for measuring at least one film added to or removed from a sample from light reflected from the sample having a plurality of wavelength components, each having an intensity, and the film comprising a material having a refractive index, the method comprising the following steps:

obtaining data representative of the intensity of at least some of said wavelength components;

arranging said data so that it is a function of a variable equal to the refractive index of the material divided by wavelength;

determining the Power Spectral Density of the arranged data as a function of potential layer thickness;

detecting at least one peak in the Power Spectral Density, including a selected peak;

determining a shift in the selected peak upon, during, or after the addition of the film to or removal of the film from the sample, the shift occurring responsive to the addition or removal of the layer; and

providing as an estimated thickness of the film in at least one region sampled by the illumination light a value derived from the shift of the selected peak in the Power Spectral Density, the estimated thickness being derived without requiring details of any structure underlying or adjacent to the region.

10. A computer program medium embodying a program of instructions executable by a computer to perform a method for measuring at least one film added to or removed from a sample from light reflected from the sample having a plurality of wavelength components, each having an intensity, the method comprising the following steps:

obtaining data representative of the intensity of at least some of said wavelength components;

performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness;

detecting a shift in a selected peak in the thickness spectral data upon, during, or after the addition of the film to or removal of the film from the sample, the shift occurring responsive to the addition or removal of the layer; and

providing as an estimate of the thickness of the film in at least one region sampled by the illumination light a value derived from the shift in the selected peak of the thickness spectral data, the estimate being derived without requiring details of any structure underlying or adjacent to the region.

12. The computer program medium of any of claims 9, 10, or 11 in which the sample is a patterned sample.

13. The computer program medium of any of claims 9, 10, or 11 in which the sample is a multi-layer sample.

11. A computer program medium embodying a program of instructions executable by a computer to perform a method for measuring at least one film added to or removed from a sample from light reflected from the film having a plurality of wavelength components, each having an intensity, the method comprising the following steps:

obtaining data representative of the intensity of at least some of the wavelength components of the reflected light;

performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness; and

detecting at least one peak in the thickness spectral data, including a selected peak, and directly determining from a shift in the selected peak upon, during, or after the addition of the film to or removal of the film from the sample, the shift occurring responsive to the addition or removal of the film, an estimate of the thickness of the film in at least one region sampled by the illumination light, the estimate being derived without requiring details of any structure underlying or adjacent to the region.

14. A method for measuring at least one film added to or removal from a sample from light reflected from the sample having a plurality of wavelength components, each having an intensity, and the film comprising a material having a refractive index, the method comprising the following steps:

obtaining data representative of the intensity of at least some of said wavelength components;

arranging said data so that it is a function of a variable equal to the refractive index of the material divided by wavelength;

determining the Power Spectral Density of the arranged data as a function of potential layer thickness;

detecting at least one peak in the Power Spectral Density, including a selected peak;

determining a shift in the selected peak upon, during, or after the addition of the film to or removal of the film from the sample, the shift occurring responsive to the addition or removal of the film; and

providing as an estimate of the thickness of the film in at least one region sampled by the illumination light a value derived from the shift in the selected peak of the Power Spectral Density, the estimate being derived without requiring details of any structure underlying or adjacent to the region.

20. The method of any of claims 14, 15, or 19 in which the sample is a patterned sample.

21. The method of any of claims 14, 15, or 19 in which the sample is a multi-layer sample.

15. A method for measuring at least one film added to a sample from light reflected from the sample having a plurality of wavelength components, each having an intensity, the method comprising the following steps:

obtaining data representative of the intensity of at least some of said wavelength components;

performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness;

detecting at least one peak in the thickness spectral data, including a selected peak;

determining a shift in the selected peak upon, during, or after the addition of the film to or removal of the film from the sample, the shift occurring responsive to the additional or removal of the film; and

providing as an estimate of the thickness of the film in at least one region sampled by the illumination light a value derived from the shift in the selected peak of the thickness spectral data, the estimate being derived requiring details of any structure underlying or adjacent to the region.

16. The method of claim 15 in which the performing step includes deriving the Fourier Transform of the intensity data.

17. The method of claim 15 in which the performing step includes deriving the Power Spectral Density of the intensity data.

18. The method of claim 15 further comprising the step of adding the film to the sample or removing the film from the sample concurrently or simultaneously with the foregoing steps.

19. A method for measuring at least one film added to a sample from light reflected from the sample having a plurality of wavelength components, each having an intensity, the method comprising the following steps:

obtaining data representative of the intensity of at least some of said wavelength components;

performing analysis of said intensity data to obtain thickness spectral data as a function of potential layer thickness;

detecting at least one peak in the thickness spectral data, including a selected peak;

determining a shift in the selected peak upon, during, or after the addition of the film to or removal of the film from the sample, the shift occurring responsive to the addition or removal of the film; and

providing as an estimate of the thickness of the film in at least one region sampled by the illumination light a value derived from the shift in the selected peak of the thickness spectral data, the estimate being derived without requiring details of any structure underlying or adjacent to the region.