Thin film metrology

Patent metadata

Field	Value
Publication number	US-11397078-B2
Application number	US-202117194934-A
Country	US
Kind code	B2
Filing date	Mar 8, 2021
Priority date	May 19, 2020
Publication date	Jul 26, 2022
Grant date	Jul 26, 2022

Abstract

A method of evaluating a thickness of a film on a substrate includes detecting atomic force responses of the film to exposure of electromagnetic radiation in the infrared portion of the electromagnetic spectrum. The use of atomic force microscopy to evaluate thicknesses of thin films avoids underlayer noise commonly encountered when optical metrology techniques are utilized to evaluate film thicknesses. Such underlayer noise adversely impacts the accuracy of the thickness evaluation.

First claim

The invention claimed is:

1. A method for evaluating thickness of a film on a substrate, comprising:
exposing the film to non-visible electromagnetic radiation;
detecting a force response of the film to the exposing the film to non-visible electromagnetic radiation;
using the force response of the film from the detecting step to determine a thickness of the film.

2. The method of claim 1 , wherein the exposing the film to non-visible electromagnetic radiation includes exposing the film to electromagnetic radiation in a near infrared portion of the electromagnetic spectrum.

3. The method of claim 1 , wherein the detecting a response of the film includes determining a force response of the film using atomic force microscopy.

4. The method of claim 3 , wherein the atomic force microscopy is conducted in a non-contact mode.

5. The method of claim 3 , wherein the atomic force microscopy is conducted in a contact mode.

6. The method of claim 5 , further comprising:
exposing a first underlying film, below the film, to the non-visible electromagnetic radiation; and
detecting a force response of the first underlying film to the exposing the first underlying film to the non-visible electromagnetic radiation; and
using the response of the first underlying film from the detecting step for the first underlying film in combination with the response of the film from the detecting step for the film to determine a thickness of the film.

7. The method of claim 6 , further comprising:
exposing a second underlying film, below the film and the first underlying film, to the non-visible electromagnetic radiation; and
detecting a response of the second underlying film to the exposing an underlying film and first underlying film to the non-visible electromagnetic radiation; and
using the response of the second underlying film from the detecting step for the underlying film in combination with the response of the film from the detecting step for the film to determine a thickness of the film.

8. The method of claim 7 , wherein the force response of the film occurs at a first wavelength of electromagnetic radiation and the force response of the underlying film occurs at a second wavelength of electromagnetic radiation different from the first wavelength.

9. The method of claim 1 , wherein the using the force response of the film from the detecting step to determine a thickness of the film includes identifying a thickness correlated with a force response in a look up table of force responses and film thicknesses for a material making up the film.

10. A method for determining thickness of a film on a substrate, comprising:
exposing the film to infrared electromagnetic radiation;
while exposing the film to the infrared electromagnetic radiation, performing a force measurement on the film using atomic force microscopy;
determining a thickness of the film using the results of the force measurement on the film.

11. The method of claim 10 , wherein the force measurement using atomic force microscopy utilizes changes in resonance frequency of a force probe used in the atomic force microscopy.

12. The method of claim 10 , wherein the force measurement using atomic force microscopy utilizes changes in amplitude of oscillations of a force probe used in the atomic force microscopy.

13. The method of claim 10 , wherein the force measurement using atomic force microscopy utilizes changes in deflection of a force probe used in the atomic force microscopy.

14. The method of claim 10 , wherein the infrared electromagnetic radiation is near infrared electromagnetic radiation.

15. The method of claim 10 , where the force measurement is carried out in a non-contact mode.

16. A method for evaluating thickness of a film on a substrate, comprising:
exposing a plurality of films on the substrate to electromagnetic radiation in the infrared portion of the electromagnetic spectrum;
while exposing the plurality of films to the electromagnetic radiation in the infrared portion of the electromagnetic spectrum, performing a force measurement on the plurality of films using atomic force microscopy operating in a non-contact mode;
detecting a force response of the plurality of films at a first wavelength of the electromagnetic radiation in the infrared portion of the electromagnetic spectrum;
detecting a force response of the plurality of films at a second wavelength of the electromagnetic radiation in the infrared portion of the electromagnetic spectrum;
using the detected force response at the first wavelength and the detected force response at the second wavelength to evaluate a thickness of one of the plurality of films.

17. The method of claim 16 , wherein the using the detected force response at the first wavelength and the detected force response at the second wavelength to determine a thickness of one of the plurality of films includes identifying a thickness correlated with a combination of the force response at the first wavelength and a force response at the second wavelength in a look up table of force responses at the first wavelength and force responses at the second wavelength for a material making up the one of the plurality of films.

18. The method of claim 16 , wherein the plurality of films have a combined thickness of less than 40 nanometers.

19. The method of claim 16 , wherein the one of the plurality of films is the uppermost film.

20. The method of claim 16 , wherein the one of the plurality of films is not an uppermost film.

Assignees

• Taiwan Semiconductor Mfg Co Ltd

Inventors

• Chen Chih Hung
• Chen Kei-Wei
• Kung Te-Ming

Classifications

• G01B11/0616 Primary

  of coating · CPC title

• G01Q60/32 Primary

  AC mode · CPC title

• G01Q60/34

  Tapping mode · CPC title

• G01Q60/24

  AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes · CPC title