Dynamic determination of metal film thickness from sheet resistance and TCR value

Patent metadata

Field	Value
Publication number	US-10663279-B2
Application number	US-201715441805-A
Country	US
Kind code	B2
Filing date	Feb 24, 2017
Priority date	Feb 4, 2016
Publication date	May 26, 2020
Grant date	May 26, 2020

Abstract

Metal film thickness can be determined using the sheet resistance, resistivity, and temperature coefficient of resistivity for the metal film. Variation in film thickness measurements caused by resistivity can be reduced or eliminated. A probe head may be used for some of the measurements of the metal film. The probe head can include a temperature sensor used during sheet resistance measurements. A wafer on a chuck is heated, such as using the chuck or the probe head, for the measurements.

First claim

What is claimed is:

1. A method comprising:
measuring sheet resistance of a film on a wafer using at least twelve probes, wherein the probes are whiskers of a material coated with a metal, wherein the probes are each spaced apart by a distance that is 1 mm or less, and wherein the material is silicon, silicon oxide, or a combination thereof;
receiving, at a controller, the sheet resistance and a temperature coefficient of resistivity of the film on the wafer;
determining, using the controller, a resistivity of the film based on the temperature coefficient of resistivity of the film using a correlation between the resistivity of the film and the temperature coefficient of resistivity of the film; and
determining, using the controller, a thickness of the film with the equation

THK
=

(

1
Rs

)

⁢

(

γ
TCR

)

wherein THK is a thickness, Rs is sheet resistance, TCR is temperature coefficient of resistivity, and γ is a correction factor related to a slope of a linear part of a correlation curve between TCR and resistivity.

2. The method of claim 1 , wherein the correlation between the resistivity of the film and the temperature coefficient of resistivity of the film is linear.

3. The method of claim 1 , wherein the correlation between the resistivity of the film and the temperature coefficient of resistivity of the film is non-linear.

4. The method of claim 1 , wherein the thickness divided by a mean free path is greater than 10.

5. A non-transitory computer-readable storage medium, comprising one or more programs for executing the following steps on one or more computing devices:
receive a sheet resistance and a temperature coefficient of resistivity of a film on a wafer, wherein the sheet resistance is measured by at least twelve probes, wherein the probes are whiskers of a material coated with a metal, wherein the probes are each spaced apart by a distance that is 1 mm or less, and wherein the material is silicon, silicon oxide, or a combination thereof;
determine a resistivity of the film based on the temperature coefficient of resistivity of the film using a correlation between the resistivity of the film and the temperature coefficient of resistivity of the film; and
determine a thickness of the film with the equation

THK
=

(

1
Rs

)

⁢

(

γ
TCR

)

wherein THK is a thickness, Rs is sheet resistance, TCR is temperature coefficient of resistivity, and γ is a correction factor related to a slope of a linear part of a correlation curve between TCR and resistivity.

6. The non-transitory computer-readable storage medium of claim 5 , wherein the correlation between the resistivity of the film and the temperature coefficient of resistivity of the film is linear.

7. The non-transitory computer-readable storage medium of claim 5 , wherein the correlation between the resistivity of the film and the temperature coefficient of resistivity of the film is non-linear.

8. The non-transitory computer-readable storage medium of claim 5 , wherein the thickness divided by a mean free path is greater than 10.

9. A system comprising:
a probe head including:
a plurality of stop pads;
at least twelve probes configured to measure a sheet resistance of a wafer, wherein the probes are whiskers of a material coated with a metal, wherein the probes are each spaced apart by a distance that is 1 mm or less, and wherein the material is silicon, silicon oxide, or a combination thereof; and
a temperature sensor disposed on the probe head, wherein the temperature sensor is configured to measure a temperature of a wafer surface during the sheet resistance measurement; and

a controller in electronic communication with the probe head, wherein the controller includes a processor and an electronic data storage unit in electronic communication with the processor, and wherein the controller is configured to:
receive the sheet resistance measurement and a temperature coefficient of resistivity of a film on the wafer from the probe head;
determine a resistivity of the film based on the temperature coefficient of resistivity of the film using a correlation between the resistivity of the film and the temperature coefficient of resistivity of the film; and
determine a thickness of the film with the equation

THK
=

(

1
Rs

)

⁢

(

γ
TCR

)

wherein THK is a thickness, Rs is sheet resistance, TCR is temperature coefficient of resistivity, and γ is a correction factor related to a slope of a linear part of a correlation curve between TCR and resistivity.

10. The system of claim 9 , further comprising a chuck configured to hold the wafer and a heating element configured to heat the chuck.

11. The system of claim 9 , further comprising an actuator connected to the probe head, wherein the actuator is configured to move the probe head relative to the wafer.

12. The system of claim 9 , wherein the probe head further includes a heat source disposed on the probe head.

13. The system of claim 12 , wherein the heat source is a flash lamp or a laser.

14. The system of claim 12 , further comprising a chuck configured to hold the wafer, wherein the chuck includes a cooling element configured to cool at least part of a surface of the chuck.

15. The system of claim 9 , wherein the temperature sensor is disposed on one of the stop pads, and wherein the temperature sensor is configured to contact the wafer surface during the sheet resistance measurement.

16. The system of claim 9 , wherein the distance is less than 1 μm.

Assignees

• Kla Tencor Corp

Inventors

• Liu Xianghua
• Johnson Walter
• Cui Jianli
• Yu Lu
• Zhu Nanchang
• Cheng Juli
• Li Huanglin
• Liu Liming

Classifications

• G01B7/06 Primary

  for measuring thickness {(measuring during the manufacture of coatings C23C14/54)} · CPC title