Electricity: measuring and testing – Magnetic – Magnetometers
Reexamination Certificate
2001-08-30
2004-04-06
Le, N. (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetometers
C324S244000
Reexamination Certificate
active
06717402
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a probe for measuring a leakage magnetic field, comprising at least one magneto resistive element. The probe according to the present invention is applied to a microscope, an IC or the like.
BACKGROUND OF INVENTION
A microscope measuring a magnetic structure of a surface of a magnetic substance is known as a magnetic force microscope (MFM), a scanning near-field optical microscope (SNOM) or a scanning magneto-resistive microscope (SMRM), for example.
As the MFM measures a gradient of a leakage magnetic field from a sample, it is difficult to obtain a distribution of a leakage magnetic field and a magnetic structure of the sample from a value measured by the MFM. The SNOM makes use of a magneto-optical effect near a magnetic field; however, it is difficult to analyze data measured by the SNOM quantitatively because a physical phenomenon about the magneto-optical effect near the magnetic field is not clear and there is difficulty in controlling polarization at the proximity field.
The SMRM measures the leakage magnetic field from the sample directly with a magneto resistive (MR) element; therefore, the quantitative measurement in the SMRM is easier than that in the MFM and the SNOM. As to the SMRM, a basic experiment is reported in IEEE. Trans. Mag. 33(1) 891 (1997). Such a SMRM is also disclosed in JP-A-6-59004 and JP-A-10-19907.
However, a conventional probe as described in JP-A-6-59004 and JP-A-10-19907 has the MR element with a relatively large width at the order of several um, so that it is difficult to obtain a magnetic information at a relatively high resolution with the conventional probe. In order to improve the resolution of the conventional probe, it is necessary to design the conventional probe specially by junction of a magnetic probe onto a surface of the MR element or the like. As a result, a method of manufacturing the probe is complex and it is difficult to mass-produce the probes with a relatively high resolution at a relatively high yield.
DISCLOSURE OF INVENTION
It is an object of the present invention to provide a probe with a relatively high resolution capable of being mass-produced at a relatively high yield.
According to the present invention, there is provided a probe for measuring a leakage magnetic field, comprising: a substrate; a flexible cantilever having one end fixed to the substrate and a free end; and at least one magneto resistive element arranged on the free end of the cantilever. The magneto resistive element has a width within a range from 10 nm to 1 &mgr;m as measured in a direction perpendicular to a longitudinal direction of the cantilever and in a direction in which the cantilever can be deflected.
The probe according to the present invention makes use of a property that the resolution of the MR element improves as the width of the MR element becomes small in a direction perpendicular to the longitudinal direction of the cantilever and in a direction in which the cantilever can be deflected (magneto-sensitive direction). According to the present invention, by having the width of the MR element not more than 1 &mgr;m at the magneto-sensitive direction, it is possible to detect the leakage magnetic field with a wavelength of not more than 10 &mgr;m without junction of the magnetic probe onto the surface of the MR element. As a result, it is possible to mass-produce the probes with a relatively high resolution at a relatively high yield. It is possible to form the MR element having the width not more than 1 &mgr;m at the magneto-sensitive direction with a lithographic technique such as an electron beam lithography.
The smaller the width of the MR element at the magneto-sensitive direction, the shorter the wavelength in the leakage magnetic field that can be detected. If, however, the width of the MR element is smaller than 10 nm at the magneto-sensitive direction, the MR element may not have the above-mentioned property because a magnetization in a magnetic substance film composing the MR element fluctuates as a result of a thermal oscillation of the magnetization. As a result, it is necessary to have the width of the MR element be not less than 10 nm at the magneto-sensitive direction.
The MR element may be, for example, an anisotropic magneto resistive (AMR) element comprising at least one magnetic substance film, a giant magneto resistive (GMR) element comprising a multilayer structure composed of at least one magnetic substance film and at least one non-magnetic substance film or a tunneling magneto resistive (TMR) element comprising a tunnel junction of magnetic substance-insulator-magnetic substance.
Preferably, the probe according to the present invention further comprises a resistor-bridge circuit electrically connected to the magneto resistive element. Thereby, it is possible to reduce noise resulting from wiring external to the cantilever. As a result, it is possible to further improve the accuracy of a measurement by the probe that is capable of being mass-produced at a relatively high yield.
Preferably, the probe according to the present invention further comprises a stylus connected to the MR element. Thereby, it is possible to maintain a good tracking property for the position control on the face of the sample even if the sample having relatively large unevenness is measured. As a result, it is possible to further improve the accuracy of the measurement by the probe capable of being mass-produced at a relatively high yield. It is not necessary to apply a complex process of the conventional method of manufacturing the probe when the stylus is connected to the MR element. The stylus may be a carbon nanotube or a whisker composed of a magnetic substance.
According to the present invention, there is provided a probe measuring a leakage magnetic field, comprising: a substrate; a flexible cantilever having one end fixed to the substrate and a free end; at least two magneto resistive elements each arranged on the free end of the cantilever; and means for determining the leakage magnetic field in relation to a dependency along with a direction with which the magneto resistive elements are provided. The magneto resistive elements each have a width within a range from 10 nm to 1 &mgr;m as measured in a direction perpendicular to a longitudinal direction of the cantilever and in a direction in which the cantilever can be deflected.
Thereby, it is possible to measure the leakage magnetic field in relation to a dependency along with a direction with which the MR elements are provided continuously, for example, a direction parallel to a height of the probe, and it is also possible to measure a distribution of a height in the magnetic field at a relatively high resolution.
There is provided a method of manufacturing a probe comprising steps of: providing a layer composed of a flexible material on one face of a substrate; forming by a lithographic technique at least one MR element on the layer; and removing a part of the substrate to form a cantilever having one end fixed to the substrate and the free end arranged with the at least one MR element.
According to the method, as the at least one MR element is formed with the lithography, it is possible to form the MR element having a width not more than 1 &mgr;m at the magneto-sensitive direction. As a result, it is possible to mass-produce the probes with a relatively high resolution at a relatively high yield. The lithography is an electron beam lithography and so on.
Preferably, the magneto resistive element has a width within a range from 10 nm to 1 &mgr;m as measured in a direction perpendicular to a longitudinal direction of the cantilever and in a direction in which the cantilever can be deflected.
Preferably, the method further comprises a step of forming a resistor-bridge circuit on the cantilever, the resistor-bridge circuit being electrically connected to the MR element. Thereby, it is possible to mass-produce the probes with an improved accuracy of the measurement at a relatively high yield.
Preferably, the method further comprises a s
Hosoi Hirotaka
Kimura Michiya
Mukasa Koichi
Sawamura Makoto
Sueoka Kazuhisa
Aurora Reena
Hokkaido University
Le N.
Stoel Rives LLP
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