Scanning magnetic microscope having improved magnetic sensor

• US 7,145,330 B2
• Filed: 08/14/2003
• Issued: 12/05/2006
• Est. Priority Date: 08/16/2002
• Status: Active Grant

• Current Assignee: Brown University
• Original Assignee: Brown University
• Inventors: Xiao, Gang
• Primary Examiner(s): Vanore, David A.
• Application Number:
  US10/493,831
• Publication Number:
  US 20040207396A1
• Time in Patent Office: 1,209 Days
• Field of Search: 324/244, 324/247
• US Class Current: 324/244
• CPC Class Codes: G01Q 10/04 Fine scanning or positioning
• CPC Class Codes: G01Q 30/04 Display or data processing devices
• CPC Class Codes: G01Q 60/54 Probes, their manufacture, or their related instrumentation, e.g. holders
• CPC Class Codes: G01R 33/0385 in relation with magnetic force measurements magnetic force microscopes G01Q60/50

Abstract

A scanning magnetic microscope SMM (20) includes a sensor (10) for sensing a magnetic field generated by a specimen (78), the sensor including one of a MTJ, a GMR, or an EHE sensor; translation apparatus (22A–C, 52) for translating the sensor relative to a surface of sad specimen; and a data processor (50), having an input coupled to an output of said sensor, for constructing an image of said magnetic field. The sensor preferably includes one to three sensing units each defining a sensing axis for sensing a component of a magnetic field from a specimen, the sensing units disposed such that the sensing axes are orthogonal to one another. Pluralities of such sensors can be disposed in two or three dimensional arrays. The SMM can be used for examining the current flow in ICs, electromigration, magnetic data storage media, biomagnetic systems and magnetic ink used to print currency.

Claims

1. A scanning magnetic microscope, comprising:

a magnetic sensor for sensing a magnetic field generated by a specimen;

said magnetic sensor comprising at least two magnetic sensing units each defining a sensing axis, said sensing axes being disposed orthogonally to one another; and

translation means for translating at least one of said magnetic sensor and said specimen relative to one another along a measurement axis that is not parallel to the sensing axis;

further comprising means for maintaining said magnetic sensor in contact with a surface of said specimen during measurement.

2. A microscope according to claim 1, further comprising a set of N magnetic sensors disposed transversely with respect to said measurement axis, wherein N is an integer greater than one.

3. A microscope according to claim 2, in which said set of N magnetic sensors are disposed at about equal distances from one another along a transverse axis that is perpendicular to said measurement axis.

4. A microscope according to claim 1, further comprising a height control apparatus for actively maintaining said magnetic sensor at a measurement offset distance from a surface of said specimen during measurement.

5. A microscope according to claim 1, further comprising a wear-resistant coating on a contact surface of said sensors.

6. A microscope according to claim 5, in which said wear-resistant coating is selected from the group comprising amorphous carbon film and synthetic diamond film.

7. A microscope according to claim 1, further comprising a coating of lubricant between said sensor and said sample.

8. A microscope according to claim 1 further comprising a data processor, having an input coupled to an output of said magnetic sensor, for constructing an image of said magnetic field.

9. A scanning magnetic microscope, comprising:

a magnetic sensor for sensing a magnetic field generated by a specimen;

said magnetic sensor comprising at least two magnetic sensing units each defining a sensing axis, said sensing axes being disposed orthogonally to one another; and

translation means for translating at least one of said magnetic sensor and said specimen relative to one another along a measurement axis that is not parallel to the sensing axis;

further comprising a lubricant reservoir that is translated with said magnetic sensor.

10. A scanning magnetic microscope, comprising:

a plurality of N magnetic sensors for sensing a magnetic field generated by a specimen;

said N magnetic sensors disposed transversely with respect to a measurement axis, whereby said magnetic field may be sensed at N locations simultaneously, N being an integer greater than one; and

translation means for translating at least one of said magnetic sensor and said specimen along a measurement axis relative to a surface of said specimen,

wherein each of the N magnetic sensors comprise at least two magnetic sensing units each defining a sensing axis, said sensing axes of each magnetic sensor being disposed orthogonally, to one another;

further comprising means for maintaining at least one of said magnetic sensors in contact with a surface of said specimen during measurement.

11. The scanning magnetic microscope of claim 10 wherein each of the N magnetic sensors comprise three magnetic sensing units each defining a sensing axis, said sensing axes of each magnetic sensor being disposed orthogonally to one another.

12. A microscope according to claim 10, in which said set of N magnetic sensors are disposed at about equal distances from one another along a transverse axis that is perpendicular to said measurement axis, and wherein the translation means further comprises means for stepping one of said specimen and at least one of said sensors transversely with respect to said measurement axis.

13. A microscope according to claim 10, further comprising a height control apparatus for actively maintaining at least one of said magnetic sensors at a measurement offset distance from a surface of said specimen during measurement.

14. A microscope according to claim 10, further comprising a wear-resistant coating on a contact surface of said sensors.

15. A microscope according to claim 14, in which said wear-resistant coating is selected from the group comprising amorphous carbon and synthetic diamond.

16. A microscope according to claim 10, further comprising a coating of lubricant between said sensor and said sample.

17. A microscope according to claim 10 further comprising a data processor, having an input coupled to an output of said magnetic sensor, for constructing an image of said magnetic field.

18. A scanning magnetic microscope, comprising:

a plurality of N magnetic sensors for sensing a magnetic field generated by a specimen;

said N magnetic sensors disposed transversely with respect to a measurement axis, whereby said magnetic field may be sensed at N locations simultaneously, N being an integer greater than one; and

translation means for translating at least one of said magnetic sensor and said specimen along a measurement axis relative to a surface of said specimen,

wherein each of the N magnetic sensors comprise at least two magnetic sensing units each defining a sensing axis, said sensing axes of each magnetic sensor being disposed orthogonally to one another;

further comprising a lubricant reservoir that is translated with said magnetic sensor.

19. A method of measuring a magnetic field comprising:

providing a scanning magnetic microscope comprising at least one magnetic sensor, said sensor comprising at least two magnetic sensing units each defining a sensing axis, said sensing axes being disposed orthogonally to one another;

applying a sense current to the magnetic sensor;

translating the at least one sensor relative to a surface of a specimen along a measurement axis; and

maintaining at least one of said magnetic sensors in contact with a surface of said specimen during measurement.

20. The method of claim 19 wherein the scanning magnetic microscope comprises at least two magnetic sensors disposed along a line that is transverse to the measurement axis, and wherein translating comprises translating the at least two sensors simultaneously.

21. The method of claim 20 wherein translating the at least two sensors comprises operating means for independently translating said at least two sensors such that movement of one of said sensors in a height direction is independent of movement of at least one other of said sensors in the height direction, said height direction being perpendicular to said measurement axis.