Method of determining an electrical property of a test sample

• US 8,907,690 B2
• Filed: 09/03/2008
• Issued: 12/09/2014
• Est. Priority Date: 09/03/2007
• Status: Active Grant

• Current Assignee: CAPRES A/S (KLA Corporation)
• Original Assignee: CAPRES A/S (KLA Corporation)
• Inventors: Petersen, Dirch H., Hansen, Ole
• Primary Examiner(s): Hollington, Jermele M
• Assistant Examiner(s): MCANDREW, CHRISTOPHER P
• Application Number:
  US12/676,124
• Publication Number:
  US 20100271059A1
• Time in Patent Office: 2,288 Days
• Field of Search: 324/750.03, 324/750.09, 324/750.19, 324/765, 324/251, 324/261, 324/715, 324/719, 324/754.23, 324/754.01, 324/754.03
• US Class Current: 324/754.03
• CPC Class Codes: G01R 31/2648 Characterising semiconductor materials testing of materials or semi-finished products G01R31/2831; testing during manufacture H01L22/00
• CPC Class Codes: H01L 22/14 for electrical parameters, e.g. resistance, deep-levels, CV, diffusions by electrical means
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A method of obtaining an electrical property of a test sample, comprising a non-conductive area and a conductive or semi-conductive test area, by performing multiple measurements using a multi-point probe. The method comprising the steps of providing a magnetic field having field lines passing perpendicularly through the test area, bringing the probe into a first position on the test area, the conductive tips of the probe being in contact with the test area, determining a position for each tip relative to the boundary between the non-conductive area and the test area, determining distances between each tip, selecting one tip to be a current source positioned between conductive tips being used for determining a voltage in the test sample, performing a first measurement, moving the probe and performing a second measurement, calculating on the basis of the first and second measurement the electrical property of the test area.

Claims

1. A method of determining an electrical property of a test sample using the so-called Hall effect, the test sample comprising a non-conductive area and a conductive or semi-conductive test area separated by a boundary, wherein the method comprises:

providing a test probe comprising a probe body having a planar probe surface, a multitude of probe arms extending from the probe body parallel to the planar probe surface, and a multitude of electrically conductive tips separated by predetermined separation distances, wherein each of the tips is supported by a respective probe arm and is configured to establish electrical contact with the test area, and wherein one of the tips is a current source tip positioned between a first one of the tips and a second one of the tips;

providing a magnetic field having field lines passing perpendicularly through the test area;

positioning the test probe so as to place the electrically conductive tips in contact with the test area in a first position;

determining the shortest distance between the current source tip and the boundary, and between each of the first and second ones of the tips and the boundary;

applying a first current to the test sample through the current source tip;

measuring a first voltage between the first and second ones of the electrically conductive tips;

moving the test probe so as to place the electrically conductive tips in contact with the test area in a second position that changes the ratio of (a) the shortest distance between the current source tip and the boundary to (b) the separation distance between the first and second ones of the electrically conductive tips;

applying a second current to the test sample through the current source tip;

measuring a second voltage between the first and second ones of the electrically conductive tips; and

calculating, on the basis of the first and second measured voltages, an electrical property of the test area.

2. The method according to claim 1, wherein the boundary has a shape selected from the group consisting of one or more of linear, rectangular, box-shaped, square, triangular, round, polygonal, arbitrarily shaped, and any combination hereof.

3. The method according to claim 1, wherein the magnetic field is stationary.

4. The method according to claim 3, wherein the magnetic field has a field strength in the order of 200 mT-700 mT.

5. The method according to claim 1, wherein the electrically conductive tips in the multitude of electrically conductive tips are arranged linearly.

6. The method according to claim 5, wherein during the steps of measuring, the test probe is oriented so that the electrically conductive tips are positioned parallel to at least a part of the boundary.

7. The method according to claim 1, wherein the step of moving the test probe is performed while maintaining the electrically conductive tips in contact with the test area.

8. The method according to claim 1, wherein the step of moving the test probe is performed by moving the electrically conductive tips out of contact with the test area, moving the test probe, and bringing electrically conductive tips into contact with the test area at the second position.

9. The method according to claim 1, wherein the electrical property is selected from the group consisting of one or more of sheet resistance, active implant dose, and carrier mobility.

10. The method according to claim 1, wherein the first and second measured voltages are fitted into a data model.

11. The method according to claim 1, wherein the method further comprises calculating at least one of a correction factor and a correction function so as to fit the first and second measured voltages to theoretical data.

12. The method according to claim 1, wherein the test area defines a size allowing the measuring steps and the calculating step to be performed using equations for infinite sheet calculations.

13. The method according to claim 1, wherein the method comprises using a numerical method.

14. The method according to claim 1, wherein the magnetic field is a varying magnetic field.

15. The method according to claim 13, wherein the numerical method is a finite element method.

16. A system for determining an electrical property of a test sample using the so-called Hall effect, the test sample comprising a non-conductive area and a conductive or semi-conductive test area separated by a boundary, the system including:

a test probe, comprising;

(a) a probe body having a planar probe surface and a plurality of probe arms extending from the probe body parallel to the planar probe surface; and

(b) a plurality of electrically conductive tips separated from each other by predetermined separation distances, each of the tips being supported by a respective probe arm and configured to establish electrical contact with the test area;

a test probe holder that receives the test probe, and a test sample holder that receives and holds the test sample, the test probe holder and the test sample holder being movable relative to each other so as to bring the plurality of electrically conductive tips into contact with the test area in a first position and in a second position displaced from the first position;

a magnet configured for providing a magnetic field having field lines passing perpendicularly through the test area;

a current source configured for applying a current to the test sample through a current source tip in the plurality of the electrically conductive tips when the electrically conductive tips are in contact with the test area, the current source tip being one of the electrically conductive tips positioned between first and second tips in the plurality of electrically conductive tips; and

a microprocessor system configured to implement a method comprising the steps of;

(a) determining the shortest distance between the current source tip and the boundary and between each of the first and second tips and the boundary when the electrically conductive tips are in the first position;

(b) measuring a first voltage between the first and second tips of the plurality of electrically conductive tips when the electrically conductive tips are in the first position and a first current is applied to the test sample through the current source tip;

(c) measuring a second voltage between the first and second tips of the plurality of electrically conductive tips when the electrically conductive tips are in the second position and a second current is applied to the test sample through the current source tip, wherein a ratio of (i) the shortest distance between the current source tip and the boundary to (ii) the separation distance between the first and second tips of the plurality of electrically conductive tips when the plurality of electrically conductive tips are in the second position is different from the ratio when the plurality of electrically conductive tips are in the first position; and

(d) calculating, on the basis of the first and second measured voltages, an electrical property of the test area.

17. The system according to claim 16, wherein the magnetic field has a field strength on the order of 200 mT-700 mT.

18. The system according to claim 16, wherein the electrically conductive tips in the plurality of electrically conductive tips are arranged linearly.

19. The system according to claim 18, wherein the electrically conductive tips are positioned parallel to at least a part of the boundary in the first and second positions.

20. The system according to claim 16, wherein the test probe is movable from the first position to the second position while the electrically conductive tips are maintained in contact with the test area.

21. The system according to claim 16, wherein the test probe is movable from the first position to the second position with the electrically conductive tips out of contact with the test area.

22. The system according to claim 16, wherein the electrical property is selected from the group consisting of one or more of sheet resistance, active implant dose, and carrier mobility.

23. The system according to claim 16, wherein the method further comprises fitting the first and second measured voltages into a data model.

24. The system according to claim 16, wherein the method further comprises calculating at least one of a correction factor and a correction function for fitting the first and second measured voltages to theoretical data.

25. The system according to claim 16, wherein the test area defines a size allowing the measuring steps and the calculating step of the method to be performed using equations for infinite sheet calculations.

26. The system according to claim 16, wherein the method comprises using a numerical method.

27. The system according to claim 26, wherein the numerical method is a finite element method.