Method for determining local resistivity and carrier concentration using scanning spreading resistance measurement set-up

Patent metadata

Field	Value
Publication number	US-9588137-B2
Application number	US-201314019576-A
Country	US
Kind code	B2
Filing date	Sep 6, 2013
Priority date	Sep 6, 2012
Publication date	Mar 7, 2017
Grant date	Mar 7, 2017

Abstract

The disclosure is related to an SSRM method for measuring the local resistivity and carrier concentration of a conductive sample. The method includes contacting the conductive sample at one side with an AFM probe and at another side with a contact electrode, modulating, at a modulation frequency, the force applied to maintain physical contact between the AFM probe and the sample while preserving the physical contact between the AFM probe and the sample, thereby modulating at the modulation frequency the spreading resistance of the sample; measuring the current flowing through the sample between the AFM probe and the contact electrode; and deriving from the measured current the modulated spreading resistance. Deriving the modulated spreading resistance includes measuring the spreading current using a current-to-voltage amplifier, converting the voltage signal into a resistance signal, and filtering out from the resistance signal, the resistance amplitude at the modulation frequency.

First claim

The invention claimed is:

1. A method for determining local resistivity and carrier concentration of a sample using a scanning spreading resistance measurement set-up, the method comprising:
contacting a sample at one side with an atomic force microscope (AFM) probe thereby applying a contact force to the sample at a particular position;
contacting the sample at another side with a contact electrode;
while maintaining contact with the sample by the AFM probe and the contact electrode, varying the contact force at the particular position;
measuring, in response to varying the contact force at the particular position, a corresponding variation in resistance of the sample; and
deriving from the variation in resistance a resistivity decoupled from a spreading resistance of the sample and a carrier concentration of the sample.

2. The method of claim 1 , wherein varying the contact force comprises modulating an amplitude of the contact force with a modulation frequency while maintaining contact, and wherein measuring the sample resistance variation comprises deriving from the corresponding modulated sample resistance a resistance amplitude at the modulation frequency.

3. The method of claim 2 , wherein the resistance amplitude is derived using Fast Fourier Transformation.

4. The method of claim 2 , wherein measuring the sample resistance variation comprises measuring a current through the sample and converting the measured current to a resistance using a current-to-voltage amplifier.

5. The method of claim 1 , further comprising:
modulating, at a modulation frequency, the contact force applied to maintain physical contact between the AFM probe and the sample, while preserving the physical contact, thereby modulating at the modulation frequency the spreading resistance of the sample;
measuring the current flowing through the sample between the AFM probe and the contact electrode; and
deriving from the measured current the modulated spreading resistance.

6. The method of claim 5 , wherein deriving the modulated spreading resistance further comprises:
measuring spreading current using a current-to-voltage amplifier thereby converting a current signal into a resistance signal; and
filtering out from the resistance signal a resistance amplitude at the modulation frequency.

7. The method of claim 6 , wherein filtering out from the resistance signal the resistance amplitude comprises using a lock-in amplifier tuned to the modulation frequency.

8. The method of claim 6 , wherein filtering out from the resistance signal the resistance amplitude comprises:
using Fast Fourier Transformation; and
selecting a signal at the modulation frequency.

Assignees

• Imec

Inventors

• Eyben Pierre
• Vandervorst Wilfried
• Cao Ruping
• Schulze Andreas

Classifications

• H10P74/207

  Electrical properties, e.g. testing or measuring of resistance, deep levels or capacitance-voltage characteristics · CPC title

• H10P74/00 Primary

  Testing or measuring during manufacture or treatment of wafers, substrates or devices · CPC title

• H01L22/14

  Electricity · mapped topic

• B82Y35/00

  Methods or apparatus for measurement or analysis of nanostructures · CPC title

• G01Q60/30 Primary

  Scanning potential microscopy · CPC title