Position correction method and a system for position correction in relation to four probe resistance measurements

• US 11,131,700 B2
• Filed: 01/08/2018
• Issued: 09/28/2021
• Est. Priority Date: 01/09/2017
• Status: Active Grant

• Current Assignee: CAPRES A/S (KLA Corporation)
• Original Assignee: CAPRES A/S (KLA Corporation)
• Inventors: Osterberg, Frederik Westergaard, Cagliani, Alberto, Petersen, Dirch Hjorth, Hansen, Ole
• Primary Examiner(s): Monsur, Nasima
• Application Number:
  US16/475,362
• Publication Number:
  US 20190310295A1
• Time in Patent Office: 1,359 Days
• Field of Search: None
• CPC Class Codes: G01R 1/06794 Devices for sensing when probes are in contact, or in position to contact, with measured object
• CPC Class Codes: G01R 1/073 Multiple probes
• CPC Class Codes: G01R 27/08 Measuring resistance by measuring both voltage and current
• CPC Class Codes: G01R 27/14 Measuring resistance by measuring current or voltage obtained from a reference source G01R27/16, G01R27/20, G01R27/22 take precedence

Abstract

The present invention relates to a method of establishing specific electrode positions by providing a multi-point probe and a test sample. The method comprises the measuring or determining of a distance between two of the electrodes of the multi-point probe and establishing a resistance model representative of the test sample. The method further comprises the performing of at least three different sheet resistance measurements and establishing for each of the different sheet resistance measurement a corresponding predicted sheet resistance based on the resistance model. Thereafter the method comprises the establishment of a set of differences constituting the difference between each of the predicted sheet resistance and its corresponding measured sheet resistance, and deriving the specific electrode positions of the multi-point probe on the surface of the test sample by using the distance and performing a data fit by minimizing an error function constituting the sum of the set of differences.

Claims

1. A method of establishing specific electrode positions, on a surface of a test sample, of a multi-point probe that includes more than four parallel probe arms extending from a probe body, each of the probe arms including an electrode, wherein the method comprises the steps of:

(a) positioning the multi-point probe such that each of the electrodes is in contact with the surface of the test sample;

(b) selecting two of the electrodes of the multi-point probe;

(c) determining a distance between the selected two of the electrodes;

(d) establishing a resistance model representative of the test sample, the resistance model defining specific electrode positions of the multi-point probe relative to the surface of the test sample included as unknown parameters, the resistance model representing the test sample as at least one of a finite sheet and a multi-layered sheet;

(e) performing a plurality of different resistance measurements on the test sample with the multi-point probe, each of the resistance measurements including;

(i) selecting four different electrodes of the multi-point probe;

(ii) dividing the four different electrodes into a first pair of electrodes and a second pair of electrodes;

(iii) applying a current propagating through the test sample between the first pair of electrodes;

(iv) detecting a voltage induced between the second pair of electrodes; and

(v) establishing a measured resistance based on a ratio of the voltage and the current;

(f) establishing for each of the different resistance measurements a corresponding predicted resistance based on the resistance model;

(g) establishing a set of differences constituting the difference between each of the predicted resistances and its corresponding measured resistance; and

(h) deriving the specific electrode positions of the multi-point probe on the surface of the test sample by using the distance between the selected two of the electrodes, and performing a data fit by minimizing an error function constituting the sum of the set of differences.

2. The method of claim 1, wherein the multi-point probe includes two outermost electrodes, and wherein the step of selecting two of the electrodes of the multi-point probe includes selecting the two outermost electrodes of the multi-point probe.

3. The method of claim 1, wherein the test sample is a multi-layered sheet comprising a top layer and a bottom layer, and constituting a magnetic tunnel junction, and wherein the resistance model represents a magnetic tunnel junction.

4. The method of claim 3, wherein the resistance model is defined by the equation:

5. The method of claim 1, wherein the electrodes are placed adjacent a boundary of the surface of the test sample, and wherein the resistance model represents a micro-Hall effect measurement.

6. The method of claim 5, wherein the surface of the test sample extends in any direction less than twice the distance between two outermost electrodes of the multi-point probe.

7. The method of claim 5, wherein at least one of the electrodes is located closer to the boundary than twice the distance between two outermost electrodes of the multi-point probe.

8. The method of claim 5, wherein the resistance model is defined by the equation:

9. The method of claim 1, wherein the test sample is of a semiconductor material.

10. The method of claim 1, wherein the error function is:

e=Σ

_n=1^m(ƒ

(α

, β

_n)−

R_n(β

_n))², in which α

constitutes the electrical test sample parameters, and β

_n represents the specific electrode positions.

11. The method of claim 1, further comprising the additional step of measuring at least one electrical parameter of the test sample selected from the group consisting of current, voltage, and resistance.

12. The method of claim 1, further comprising the additional step of determining a sheet resistance of the test sample.

13. A computer-based system for establishing specific electrode positions, on a surface of a test sample, of a multi-point probe, the system comprising:

a multi-point probe having a probe body and more than four parallel probe arms extending from the probe body, each of the probe arms including an electrode, the multi-point probe being positionable such that each of the electrodes is in contact with a surface of a test sample, wherein, when the multi-point probe is so positioned, a distance is defined between two outermost electrodes of the multi-point probe, the system further including a resistance model representative of the test sample, the resistance model having the specific electrode positions of the multi-point probe relative to the surface of the test sample included as unknown parameters, the resistance model representing the test sample as at least one of a finite sheet and a multilayered sheet, the system further comprising;

first means for performing a plurality of different resistance measurements, each of the resistance measurements including;

(i) selecting four different electrodes of the multi-point probe;

(ii) dividing the four different electrodes into a first pair of electrodes and a second pair of electrodes;

(iii) applying a current propagating through the test sample between the first pair of electrodes;

(iv) detecting a voltage induced between the second pair of electrodes; and

(v) establishing a measured resistance based on a ratio of the voltage and the current;

second means for establishing, for each of the different resistance measurements, a corresponding predicted resistance based on the resistance model;

third means for establishing a set of differences constituting the difference between each of the predicted resistances and its corresponding measured resistance; and

fourth means for deriving the specific electrode positions of the multi-point probe on the surface of the test sample by using the distance between the two outermost electrodes and performing a data fit by minimizing an error function constituting the sum of the set of differences.

14. The system of claim 13, wherein the test sample is a multi-layered sheet comprising a top layer and a bottom layer, and constituting a magnetic tunnel junction, and wherein the resistance model represents a magnetic tunnel junction.

15. The system of claim 13, wherein the multi-point probe is positionable such that the electrodes are placed adjacent a boundary of the surface of the test sample, and wherein the resistance model represents a micro-Hall effect measurement.

16. The system of claim 15, wherein the multi-point probe is positionable such that at least one of the electrodes is located closer to the boundary than twice the distance between two outermost electrodes of the multi-point probe.

17. The system of claim 15, wherein the resistance model is defined by the equation:

18. The system of claim 13, wherein the error function is:

e=Σ

_n=1^m(ƒ

(α

, β

_n)−

R_n(β

_n))² in which α

constitutes the electrical sample parameters, and β

_n represents the specific electrode positions.

19. The system of claim 13, further comprising fifth means for measuring at least one electrical parameter of the test sample selected from the group consisting of current, voltage, and resistance.

20. The system of claim 13, further comprising fifth means for determining a sheet resistance of the test sample.