Scanning probe microscope and measurement method using the same

Patent metadata

Field	Value
Publication number	US-10345336-B2
Application number	US-201615252993-A
Country	US
Kind code	B2
Filing date	Aug 31, 2016
Priority date	Mar 15, 2016
Publication date	Jul 9, 2019
Grant date	Jul 9, 2019

Abstract

A scanning probe microscope that includes a probe, a positioning unit configured to position a probe on a measurement sample, an excitation unit configured to excite the measurement sample at a predetermined frequency, a resonance unit configured to output a frequency modulation signal by converting a change of a capacitance of the measurement sample, a lock-in amplifier configured to output a differential capacitance signal obtained by extracting a predetermined frequency component and a harmonic component of the predetermined frequency of the demodulated signal, a conversion unit configured to output data indicative of a relationship between a voltage applied to the measurement sample and the capacitance, a detecting unit that detects a voltage value corresponding to a feature point of the relationship data, and a main measurement control unit that measures electrical characteristics of the measurement sample subjected to a DC bias voltage substantially equal to the feature point voltage.

First claim

What is claimed is:

1. A scanning probe microscope comprising:
a probe;
a positioning unit configured to position the probe on a measurement sample or a standard sample;
an excitation unit configured to excite the measurement sample, the standard sample, or the probe at an excitation frequency;
a resonance unit configured to output a frequency modulation signal obtained by converting a change of a capacitance of the measurement sample or the standard sample into a change of a resonant frequency;
a frequency demodulator configured to output a demodulated signal obtained by demodulating the frequency modulation signal;
a lock-in amplifier configured to output a differential capacitance signal obtained by extracting a frequency component and a harmonic component of the excitation frequency included in the demodulated signal;
a conversion unit configured to output relationship data indicative of a relationship between a voltage applied to the measurement sample or the standard sample and the capacitance, based on the differential capacitance signal;
a feature point voltage detecting unit configured to determine a feature point of the relationship data; and
a main measurement control unit configured to (i) select a DC bias voltage based on the determined feature point of the relationship data, and (ii) operate the excitation unit, the resonance unit, the frequency demodulator, and the lock-in amplifier to measure electrical characteristics of the measurement sample in a state where the selected DC bias voltage is applied to the measurement sample.

2. The scanning probe microscope according to claim 1 ,
wherein the conversion unit is configured to output the relationship data as monotonically increasing or decreasing relationship data, and the feature point voltage detecting unit is configured to determine the feature point as a point between a maximum point and a minimum point of values obtained by second order differentiating the monotonically increasing or decreasing relationship data with respect to voltage.

3. The scanning probe microscope according to claim 1 ,
wherein the conversion unit is configured to output the relationship data as monotonically increasing or decreasing relationship data, and the feature point voltage detecting unit is configured to determine the feature point as a point at which a maximum value or a minimum value is obtained by first order differentiating the monotonically increasing or decreasing relationship data with respect to voltage and is zero by second order differentiating the monotonically increasing or decreasing relationship data with respect to voltage.

4. The scanning probe microscope according to claim 1 ,
wherein the conversion unit is configured to output the relationship data as relationship data having a peak, and the feature point voltage detecting unit is configured to determine the feature point as a point between a maximum point and a minimum point of values obtained by first order differentiating the relationship data having a peak with respect to voltage.

5. The scanning probe microscope according to claim 1 ,
wherein the conversion unit is configured to output the relationship data as relationship data having a peak, and the feature point voltage detecting unit is configured to determine the feature point as a point at which a value obtained by first order differentiating the relationship data having a peak with respect to voltage is zero and a value obtained by second order differentiating the relationship data having a peak with respect to voltage becomes a maximum value or a minimum value.

6. A measurement method using a scanning probe microscope, comprising:
exciting a measurement sample, a standard sample, or a probe, in a state where the probe is positioned on the measurement sample or the standard sample;
generating a frequency modulation signal obtained by converting a change of a capacitance of the measurement sample or the standard sample into a change of a resonant frequency;
generating a demodulated signal obtained by demodulating the frequency modulation signal;
generating a differential capacitance signal obtained by extracting a frequency component and a harmonic component included in the demodulated signal;
generating relationship data indicative of a relationship between a voltage applied to the measurement sample or the standard sample and a capacitance, based on the differential capacitance signal;
determining a feature point of the relationship data;
selecting a DC bias voltage based on the determined feature point of the relationship data;
applying the selected DC bias voltage to the measurement sample; and
measuring electrical characteristics of the measurement sample, based on the differential capacitance signal, by sequentially performing excitation of the measurement sample or the probe, generation of the frequency modulation signal, and generation of the differential capacitance signal, while the selected DC bias voltage is applied to the measurement sample.

7. The method according to claim 6 ,
wherein generating the relationship data comprises generating monotonically increasing or decreasing relationship data, and the feature point is a point between a maximum point and a minimum point of values obtained by second order differentiating the monotonically increasing or decreasing relationship data with respect to voltage.

8. The method according to claim 6 ,
wherein generating the relationship data comprises generating monotonically increasing or decreasing relationship data, and the feature point is a point at which a maximum value or a minimum value is obtained by first order differentiating the monotonically increasing or decreasing relationship data with respect to voltage and is zero by second order differentiating the monotonically increasing or decreasing relationship data with respect to voltage.

9. The method according to claim 6 ,
wherein the measurement sample and the standard sample includes a p-type semiconductor region or an n-type semiconductor region on which the probe is placed, and
wherein the feature point is a point at which an absolute value of a slope of a curve of the relationship data is maximized, or is an inflection point of the curve.

10. The method according to claim 6 ,
wherein generating the relationship data comprises generating relationship data having a peak, and the feature point is a point between a maximum point and a minimum point of values obtained by first order differentiating the relationship data having a peak with respect to voltage.

11. The method according to claim 6 ,
wherein generating the relationship data comprises generating relationship data having a peak, and the feature point is a point at which a value obtained by first order differentiating the relationship data having a peak with respect to voltage is zero and a value obtained by second order differentiating the relationship data having a peak with respect to voltage becomes a maximum value or a minimum value.

12. The method according to claim 6 ,
wherein the measurement sample and the standard sample include a depletion layer on which the probe is placed, and
wherein the feature point is a point at which a slope of a curve corresponding to the relationship data is minimized, or a minimum point of the curve.

Assignees

• Toshiba Memory Corp

Inventors

• Hirota Jun
• Nakai Tsukasa
• Akutsu Haruko

Classifications

• G01Q60/30 Primary

  Scanning potential microscopy · CPC title