METHOD AND APPARATUS FOR INSPECTING THERMAL ASSIST TYPE MAGNETIC HEAD DEVICE

In order to enable inspection of the physical shape of a near-field light emitting portion of a thermal assist type magnetic head, a thermal assist type magnetic head device is placed on a table movable in a plane, a probe fixed to a cantilever scans a plane apart at a constant distance from the surface of the sample placed on the table while moving the table in a plane, the displacement of the cantilever is detected by applying light to the scanning cantilever and detecting reflected light from the cantilever, an atomic force microscope (AFM) image of the thermal assist type magnetic head device is formed using information about the detected displacement of the cantilever and positional information about the table, and the quality of a physical shape including the size or typical dimensions of the near-field light emitting portion is determined by processing the formed AFM image.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

For a method of inspecting the physical shape of a near-field light generating region (the size or typical dimensions of a near-field light generating region) of a thermal assist type magnetic head device, there are a method of inspecting a state of generating a near-field light generated in a near-field light emitting portion and a method of inspecting the physical shape of a near-field light generating region. In the present invention, it is made possible to detect the physical shape of a near-field light generating region of a thermal assist type magnetic head device using a scanning probe microscope.

In the following, embodiments of the present invention will be described in detail with reference to the drawings.

First Embodiment

FIG. 1is a block diagram of a basic configuration of a first embodiment of a thermal assist type magnetic head inspection apparatus according to the present invention. A thermal assist type magnetic head inspection apparatus inFIG. 1can inspect the physical shape of a near-field light generating region of each of thermal assist type magnetic head devices4in a state of a row bar (a block of the thermal assist type magnetic head devices4arrayed) before the process step of cutting a single head slider (the thermal assist type magnetic head device4). Generally, a row bar is cut out of a wafer as an elongated block in a length of about 3 to 5 cm, and is configured in which about 40 to 90 of the thermal assist type magnetic head devices4(head sliders) are arrayed. The thermal assist type magnetic head inspection apparatus according to the embodiment is configured to perform a predetermined inspection on the row bar1as a work. Generally, about 20 to 30 of the row bars1are arrayed and accommodated in a tray, not illustrated, in the direction of a minor axis at a predetermined gap. A handling robot, not illustrated, takes the row bar1out of the tray, not illustrated, one by one, and carries the row bar1to an inspection stage101. The row bar1carried and placed on the inspection stage101is inspected as described later.

The inspection stage101includes an X stage106and a Y stage105that can move the row bar1in X- and Y-directions. The row bar1is positioned by bumping one side face of the row bar1in the direction of the major axis against the reference plane of the Y stage105. A mounting unit114for positioning the row bar1is provided on the top face of the Y stage105. A step (not illustrated) nearly matched with the shape of the row bar1is provided on the side edge of the top face of the mounting unit114. The row bar1is disposed at a predetermined position by contacting the bottom face and side face of the step. The rear side face of the row bar1(a face opposite to a face on which the joining terminals of the thermal assist type magnetic head device4are provided) contacts the back face of the step. Since the contact surfaces each include a reference plane in the position relationship in which the contact surfaces are in parallel with and orthogonal to the moving direction (the X-axis) of the X stage106and the moving direction (the Z-axis) of a Z stage104, the row bar1contacts the bottom face and side face of the step of the Y stage105for positioning the row bar1in the X- and Z-directions.

A camera103for measuring a position displacement amount is provided above the Y stage105. The Z stage104moves a cantilever unit100of an atomic force microscope (AFM) in the Z-direction. The X stage106, the Y stage105, and the Z stage104of the inspection stage101are each configured of a piezo stage driven by a piezoelectric element. After finishing the positioning of the row bar1at a predetermined position, the row bar1is attached and held on the mounting unit114.

A piezo driver107drives and controls the X stage106, the Y stage105, and the Z stage104(the piezo stages) of the inspection stage101. A control unit PC30is configured of a control computer in the basic configuration of a personal computer (PC) including a monitor. As illustrated inFIG. 1, at a location opposite to the upper area of the row bar1placed on the mounting unit114on the Y stage105of the inspection stage101, the cantilever unit100is disposed on which a probe120with a pointed tip end is formed and the end of the cantilever unit100is a free end. The cantilever unit100is mounted on an oscillating unit122provided on the lower side of the Z stage104. The oscillating unit122is configured of a piezoelectric element, to which an alternating current voltage is applied at a frequency near a mechanical resonance frequency of the cantilever unit100caused by an excitation voltage from the piezo driver107, and the probe120is vertically oscillated. Moreover, in the case where the excitation voltage from the piezo driver107is constant, the probe120is not oscillated, and stops at a certain position.

A displacement detecting unit is configured of a semiconductor laser device109and a displacement sensor110formed of a four divided optical detector device. A beam emitted from the semiconductor laser device109is applied on the cantilever unit100, and a beam reflected off the cantilever unit100is guided to the displacement sensor110. A differential amplifier111applies a predetermined arithmetic operation process to differential signals of four signals outputted from the displacement sensor110, and outputs the signals to the DC converter112. Namely, the differential amplifier111outputs displacement signals corresponding to differences between four signals outputted from the displacement sensor110to the DC converter112. Therefore, in the state in which the cantilever unit100is not oscillated by the oscillating unit122, the output from the differential amplifier111is zero. The DC converter112is configured of an RMS-DC converter (Root Mean Squared value to Direct Current Converter) that converts the displacement signal outputted from the differential amplifier111into a direct current signal of an effective value.

The displacement signal outputted from the differential amplifier111is a signal in response to the displacement of the cantilever unit100. In the case where the cantilever unit100is oscillated, the signal is an alternating current signal, whereas in the case where the oscillations of the cantilever unit100are stopped, the signal is a direct current signal. The signal outputted from the DC converter112is inputted to a feedback controller113. The feedback controller113outputs the signal inputted from the DC converter112to the control unit PC30as a signal to monitor the size of the present displacement amount of the cantilever unit100. The signal is monitored at the control unit PC30, and the piezoelectric element (not illustrated) to drive the Z stage104using the piezo driver107is controlled according to the value, so that the initial position of the cantilever unit100is adjusted before starting measurement. In the embodiment, the floating height of the head of a hard disk drive is set as the initial position of the cantilever unit100.

An oscillator102is a device that supplies an oscillation signal to excite the cantilever unit100to the piezo driver107. The piezo driver107drives the oscillating unit122based on the oscillation signal from the oscillator102to oscillate the cantilever unit100at a predetermined frequency. In the case where the probe120is not oscillated, the oscillator102does not output the oscillation signal to the piezo driver107.

FIG. 2is an enlarged diagram of the configuration of a magnetic field generating region3and a thermal assist light (a near-field light) generating region2of the thermal assist type magnetic head device4formed in the row bar1together with the cantilever unit100.

As illustrated inFIG. 2, the cantilever unit100is positioned by the Z stage104in such a way that a constant gap d is maintained at the lowest point between the tip end portion of the probe120of the cantilever unit100and the surface of a sample on the surface of the thermal assist type magnetic head device4formed in the row bar1when the probe120is oscillated at a constant amplitude Hf. The cantilever unit100is oscillated by the piezo driver107receiving the oscillation signal from the oscillator102at the resonance frequency of the cantilever unit100or a frequency near the resonance frequency, and scans a plane in parallel with the recording surface of the thermal assist type magnetic head device4formed in the row bar1within a range of a few hundreds nm to a few μm. In the embodiment, the X stage106and the Y stage107move the row bar1.

Here, in the case where the material of the row bar1, which is a sample, is uniform in the range in which the probe120scans the row bar1, as illustrated inFIG. 3A, a phase difference321between an oscillation waveform310of the cantilever unit100driven by the piezo driver107and a displacement signal waveform311is constant. The displacement signal waveform311is detected at the displacement sensor110by scanning the probe120over the plane in parallel with the recording surface of the thermal assist type magnetic head device4.

However, when the scan range includes a portion having a material different from the materials of the other portions like the near-field light generating region2or the magnetic field generating region3, force (van der Waals force) acting between the probe120and the portion having a different material is changed. As a result, as illustrated inFIG. 3B, even though the surface of the near-field light generating region2and the surface of the other portion are on the same plane in the scan range, the oscillation waveform of the cantilever unit100is changed, and a phase difference322between the oscillation waveform310of the cantilever unit100driven by the piezo driver107and a displacement signal waveform312detected at the displacement sensor110by scanning the probe120over the row bar1is changed with respect to the state inFIG. 3A.

In the change, although the amplitude Hf of the probe120is also fluctuated, the fluctuation is detected at the DC converter112, and inputted to the control unit PC30through the feedback controller113, and the control unit PC30controls the drive of the Z stage104by the piezo driver107, so that the fluctuation of the amplitude Hf is suppressed.

The changed phase difference is imaged, so that the portion of the changed phase difference can be detected as a region of a different material. Positional information and size information about the region in which the detected phase difference is changed are compared with preset reference values using design information, and it is determined whether a difference from the reference value is in an acceptable range for inspecting whether the near-field light generating region2is correctly formed.

FIG. 4Ais a diagram of the configuration of the control unit PC30. A signal is inputted from the differential amplifier111in response to the displacement of the cantilever unit100(the signal311inFIG. 3Aand the signal312inFIG. 3B), and the signal is inputted to a phase comparison unit302. Moreover, the phase comparison unit302receives the signal transmitted from the oscillator102(the signal310inFIGS. 3A and 3B), and detects the phase difference between the signal from the oscillator102and the signal inputted from the differential amplifier111. Subsequently, information about the detected phase difference is sent to a phase difference image forming unit303together with positional information about the Y stage105and the X stage106sent from the inspection stage101, and a phase difference image401is formed as illustrated inFIG. 4B.

The formed phase difference image401is sent to a region determining unit304, a gap L between the center of an image402of the near-field light generating region2and the center of an image403of the magnetic field generating region3and a size D of the image402of the near-field light generating region2are measured from the phase difference image401, and the gap L and the size D are compared with preset reference values for calculating displacement amounts from the reference values. The calculated displacement amounts from the reference values are compared with preset thresholds. It is checked whether the displacement amounts are in acceptable ranges, and the quality of the position and shape of the near-field light generating region2is determined with reference to the magnetic field generating region3. The determined result of quality is sent to an input/output unit31, and displayed on a screen, not illustrated.

FIG. 5is a flowchart of the operation procedures of the thermal assist type magnetic head inspection apparatus described above.

First, a row bar1is taken out of a plurality of the row bars1one by one and carried on the inspection stage101(S501), the row bar1is aligned using the camera103(S502), and the thermal assist type magnetic head device unit4(a measurement head) formed in the row bar1is moved at the measurement position for positioning the measurement head (the thermal assist type magnetic head device4) (S503). Subsequently, the piezo driver107controls the Z stage104, and the probe120of the cantilever unit100is approached to the recording surface of the measurement head (S504).

Subsequently, the piezo driver107drives the oscillating unit122based on the oscillation signal from the oscillator102to oscillate the cantilever unit100at a predetermined frequency. The piezo driver107drives the Y stage105and the X stage106to move the row bar1in the XY-plane in this state, and the cantilever unit100scans the plane in parallel with the recording surface of the head within a range of a few hundreds nm to a few μm (S505).

In the scanning, the oscillations of the cantilever100are detected as a signal waveform of a laser that is emitted from the semiconductor laser device109, reflected off the cantilever100, and detected at the displacement sensor110. The detected signal waveform is compared with the drive signal waveform transmitted from the oscillator102to measure the phase difference (S506).

Subsequently, the cantilever is raised, and it is checked whether there is a head to be subsequently measured in the row bar1(S507). When there is a subsequent head, the head to be subsequently measured is moved on the lower part of the cantilever (S508), and manipulation from S504is performed. In the case where there is no head to be subsequently measured in the row bar1, the row bar1that measurement is finished is taken out using a handling unit, not illustrated, in the state in which the cantilever unit100is raised by the Z stage104, and the row bar1is accommodated in a restoring tray (S509). Subsequently, it is checked whether there is an uninspected row bar40in a supply tray, not illustrated (S510). In the case where there is an uninspected row bar40, the process is returned to S501, the uninspected row bar40is taken out from the supply tray (not illustrated) (S511), and the uninspected row bar40is carried to the inspection stage101for performing steps from S501. On the other hand, in the case where there is no uninspected row bar40in the supply tray, measurement is finished (S512).

It is noted that in the embodiment described above, it is described in which inspection is performed in the state of the row bar1. However, the embodiment is not limited thereto. Such a configuration may be possible in which a single thermal assist type magnetic head device4cut out from the row bar1is placed on the mounting unit114for similar inspection as described above.

In the embodiment described above, a scheme is described in which the probe120is scanned in such a way that the probe120is avoided to directly contact the surface of the row bar1, which is a sample. In this case, the lowest point for oscillations is a position at a constant distance apart from the surface of the row bar1. However, such a scheme may be possible in which the lowest point of the oscillations of the probe120is matched with the surface of the row bar1for scanning while contacting the row bar1at the lowest point for oscillations.

Moreover, in the embodiment described above, a method is described in which the phase difference image between the region including the near-field light generating region2and the region including the magnetic field generating region3of the thermal assist type magnetic head device4is formed, and the gap L between the center of the image402of the near-field light generating region2and the center of the image403of the magnetic field generating region3and the size D of the image402of the near-field light generating region2are found to determine the quality of the position and shape of the near-field light generating region2. However, such a configuration may be possible in which the region including the magnetic field generating region3is not scanned with the probe120, only the scan region including the near-field light generating region2is scanned with the probe120using design information about the thermal assist type magnetic head device4, the phase difference image of the region including the near-field light generating region2is formed, dimensions D1 and D2 in two directions orthogonal to each other are found from the phase difference image402of the near-field light generating region2as illustrated inFIG. 4C, and the dimensions D1 and D2 are compared with preset reference values for determining the quality of the shape of the near-field light generating region2.

According to the embodiment, the near-field light generating region of the thermal assist type magnetic head device can be inspected without emitting a near-field light in a relatively early stage of the manufacturing process steps of the thermal assist type magnetic head device, in a row bar state, for example. Moreover, it is unnecessary to equip a mechanism to emit a near-field light on the inspection apparatus, so that the configuration of the inspection apparatus can be relatively simplified.

In the embodiment described above, as illustrated inFIG. 2, the configuration is described in which the probe120scans the surface of the row bar1, which is a sample. However, such a configuration may be possible in which as illustrated inFIG. 6, a small-gage wire1201of a relatively hard material is fixed to the tip end portion of the probe120and the surface of the row bar1is scanned using the small-gage wire1201. For a material forming the small-gage wire1201, any one of carbon nanofiber (CNF), a carbon nanotube (CNT), a high density carbon (HDC:DLC), and tungsten (W) may be used. With this configuration, the small-gage wire1201of a relatively hard material contacts the thermal assist type magnetic head device4formed in the row bar1, and the lifetime of the cantilever100can be prolonged more than in the case where the probe120is directly contacted.

Exemplary Modification

In the first embodiment, it is described in which the control unit PC30creates a phase difference image using the output of the differential amplifier111. In this exemplary modification, an amplitude control signal from the feedback controller113for the Z stage104is also used.

The feedback controller113receives the output from the differential amplifier111to detect the fluctuation of the amplitude of the cantilever100, and outputs a signal to suppress the fluctuation of oscillations.

The fluctuation of oscillations is generated because the material of the thermal assist type magnetic head device4is changed in scanning the probe120to cause a change in the amplitude of the oscillations of the cantilever100. The fluctuation of oscillations includes positional information about the boundary of the material of the thermal assist type magnetic head device4.

In the exemplary modification, as illustrated inFIG. 7, the control unit PC30described in the first embodiment is replaced by a control unit PC130. In the control unit PC130, a piezo driver control unit305receives an output signal including the information from the differential amplifier111, branches a signal outputted to the piezo driver107to control the Z stage104, and inputs the signal to a region determining unit3041.

The region determining unit3041receives the output from the differential amplifier111and the signal from the oscillator102to identify the boundary between the image402of the near-field light generating region2and the image403of the magnetic field generating region3from the phase difference image401illustrated inFIG. 4B, using a phase difference image formed at the phase difference image forming unit303with phase difference information extracted at the phase comparison unit302and the control signal for the Z stage104including positional information about the boundary of the material of the thermal assist type magnetic head device4outputted from the piezo driver control unit305. The center and width of the image402corresponding to the near-field light generating region2and the center of the image403corresponding to the magnetic field generating region3are then found from information about the identified boundary, and the gap L between the center of the image402and the center of the image403and a width D of the image402are calculated. The gap L and the width D are compared with preset reference values, and displacement amounts from the reference values are calculated. The calculated displacement amounts from the reference values are then compared with preset thresholds, and it is checked whether the displacement amounts are in acceptable ranges. The quality of the position and size of the near-field light generating region2with reference to the magnetic field generating region3is determined based on the result. The determined result of the quality is sent to the input/output unit31, and displayed on a screen, not illustrated.

According to the exemplary modification, the region of the image402corresponding to the near-field light generating region2and the region of the image403corresponding to the magnetic field generating region3can be determined using a plurality of items of information, so that the quality of the position and size of the near-field light generating region2can be determined at higher accuracy.

Second Embodiment

FIG. 8is a diagram of the configuration of a thermal assist type magnetic head inspection apparatus8000according to the embodiment. A basic configuration of the thermal assist type magnetic head inspection apparatus8000according to the embodiment is basically similar to the configuration of the apparatus according to the first embodiment illustrated inFIG. 1. As expressed by a thick line of a cantilever100inFIG. 9, the embodiment is different in that a magnetic film121is formed on the surface of a probe120of the cantilever100. Moreover, the embodiment is different in that an excitation signal output unit1007is provided on a control unit PC35and a signal line301is additionally provided to send a signal to a thermal assist type magnetic head device unit4formed in a row bar1. The signal is outputted from the excitation signal output unit1007, and generates a magnetic field on a magnetic field generating region3of the thermal assist type magnetic head device unit4.

FIG. 10is a diagram of the configuration of the control unit PC35according to the embodiment. The control unit PC35is different from the control unit PC30according to the first embodiment in that the control unit PC35includes a signal switching circuit unit1001that switches a signal outputted from a differential amplifier111between an MFM image generating unit1002and a phase comparison unit1003and the MFM image generating unit1002that processes the signal outputted from the differential amplifier111and creates an MFM (Magnetic Force Microscope) image when a region including the magnetic field generating region3is scanned while oscillating the probe120of the cantilever100formed with the magnetic film121on the surface.

The signal switching circuit unit1001outputs the signal outputted from the differential amplifier111to the MFM image generating unit1002side together with positional information about an X stage106and a Y stage105outputted from an inspection stage101based on positional information about the X stage106and the Y stage105outputted from the inspection stage101when the probe120is scanning a region including the magnetic field generating region3of the thermal assist type magnetic head device unit4. The MFM image generating unit1002forms an MFM image using the signal from the differential amplifier111and positional information about the X stage106and the Y stage105outputted from the inspection stage101.

On the other hand, the signal switching circuit unit1001outputs the signal outputted from the differential amplifier111to the phase comparison unit1003side together with positional information about the X stage106and the Y stage105outputted from the inspection stage101when the probe120is scanning a region including the near-field light generating region2of the thermal assist type magnetic head device unit4. Since signal processing in the phase comparison unit1003and a phase difference image forming unit1004is similar to processing in the control unit PC30described in the first embodiment, the description is omitted.

The region determining unit1005receives the MFM image formed at the MFM image generating unit1002and a phase difference image formed at the phase difference image forming unit1004, and determines the quality of the position and size of the optical near field generating region2with reference to the magnetic field generating region3.

The excitation signal output unit1007sends a magnetic field generating signal to the magnetic field generating region3through the signal line301based on positional information about the X stage106and the Y stage105outputted from the inspection stage101when the probe120scans the region including the magnetic field generating region3of the thermal assist type magnetic head device unit4.

A piezo driver control unit1006receives the output signal from the differential amplifier111, and outputs a signal to control a Z stage104to a piezo driver107.

The operation procedures of the thermal assist type magnetic head inspection apparatus8000according to the present embodiment are the same as the operation procedures described in the first embodiment with reference toFIG. 5except S506and S507. Portions different from the portions of the flowchart of the first embodiment illustrated inFIG. 5will be described with reference toFIG. 11.

After completion in S504, the excitation signal output unit1007receives positional information about the X stage106and the Y stage105output from the inspection stage101, outputs a signal to generate a magnetic field on the magnetic field generating region3of the thermal assist type magnetic head device unit4formed in the row bar1through the signal line301, and generates a magnetic field on the magnetic field generating region3(S5051). Subsequently, the region including the magnetic field generating region3on which a magnetic field is generated is scanned while vertically oscillating the probe120of the cantilever100formed with the magnetic film121on the surface (S5052), and an MFM image of the magnetic field generating region3is created at the MFM image forming unit1002(S5053).

Subsequently, the signal to generate a magnetic field on the magnetic field generating region3of the thermal assist type magnetic head device unit4formed in the row bar1from the signal line301is interrupted, the probe120scans the region including the near-field light generating region2while vertically oscillating the cantilever100as similar to the case of the first embodiment (S5054), and a phase difference image of the region including the near-field light generating region2is formed at the phase difference image forming unit1004(S5055). Moreover, the phase difference image and the MFM image created in S5052are used to identify the positions of the magnetic field generating region3and the near-field light generating region2, a distance from the magnetic field generating region3to the near-field light generating region2is calculated as positional information about the near-field light generating region2, and the size of the near-field light generating region2is calculated from the phase difference image (S5061). Lastly, the calculated values are compared with preset reference values to determine the quality of the position and size of the near-field light generating region2(S5062), and the result is outputted to an input/output unit31together with the MFM image and the phase difference image (S5063).

Also in the embodiment, as similar to the description in the first embodiment, such a configuration may be possible in which as illustrated inFIG. 6, the tip end portion of the probe120includes a small-gage wire of a relatively hard material formed with a magnetic film on the surface and the surface of the row bar1is scanned using the small-gage wire formed with the magnetic film on the surface. For a material forming the small-gage wire1201, any one of carbon nanofiber (CNF), a carbon nanotube (CNT), a high density carbon (HDC:DLC), and tungsten (W) may be used. With this configuration, the small-gage wire1201of a relatively hard material contacts the thermal assist type magnetic head device4formed in the row bar1, and the lifetime of the cantilever100can be prolonged more than in the case where the probe120is directly contacted.

Third Embodiment

This embodiment relates to a method of inspecting a thermal assist type magnetic head device formed with a near-field light emitting portion by scanning a cantilever in a plane at a constant distance apart from the surface of a sample without contacting the cantilever with the sample and an apparatus therefor.

Since the configuration of the thermal assist type magnetic head inspection apparatus according to the embodiment is similar to the configuration described in the first embodiment inFIG. 1, the detailed descriptions are omitted.

FIG. 12is an enlarged diagram of the configuration of a thermal assist light (a near-field light) generating region2of a thermal assist type magnetic head device4formed in a row bar1together with a cantilever unit100.

In the embodiment, as illustrated inFIG. 12, the cantilever unit100is controlled by a Z stage104, and stationary with respect to the surface of the thermal assist type magnetic head device4formed in the row bar1in such a way that a constant gap d is maintained between the tip end portion of a probe120of the cantilever unit100and the surface of the thermal assist type magnetic head device4. In this state, a piezo driver107receives an oscillation signal from an oscillator102, and controls an X stage106and a Y stage105to move the row bar1in a plane, so that the probe120mounted at the tip end portion of the cantilever unit100scans a desired region of the row bar1in a range of a few hundreds nm to a few μm.

Here, in the case where the probe120scans a location where a material is uniform in the scan range on the surface of the thermal assist type magnetic head device4formed in the row bar1, which is a sample, the output of a differential amplifier is zero as illustrated in an output waveform1310of the differential amplifier inFIG. 13A. Namely, the probe120is in an attitude in which the probe120scans a plane apart at a constant distance from the surface of the thermal assist type magnetic head device4. In contrast to this, when the scan range includes a portion having a material different from the materials of the other portions like the near-field light generating region2, force (van der Waals force) acting between the probe120and the portion having a different material is changed. As a result, the cantilever unit100is displaced to change the position of reflected light from the cantilever unit100, the light enters a displacement sensor110, and the displacement signal waveform1310outputted from the displacement sensor110is changed as a signal level1311illustrated inFIG. 13A.

The changed displacement signal waveform1310is imaged using positional information about the X stage106and the Y stage105, so that a portion in which the cantilever unit100is displaced can be detected as a region of a different material. From the detected image, information about the position and size of the region in which the cantilever unit100is displaced can be obtained. This information is then compared with a preset reference value using design information to determine whether a difference from the reference value is in an acceptable range, so that it can be inspected whether the optical near field generating region2is correctly formed.

Since the position of the near-field light generating region2from the end surface of the row bar1can be estimated from design information for the near-field light generating region2the thermal assist type magnetic head device4formed in the row bar1, which is an inspection target, information about a region including the near-field light generating region2can be surely acquired by an AFM when the region including the near-field light generating region2is set to the scan region of the probe120in consideration of errors.

FIG. 14Ais a diagram of the configuration of a control unit PC30. The control unit PC30receives a signal from a feedback controller113. The signal from the feedback controller113is a signal in which an AC output from a differential amplifier111received with a signal from the displacement sensor110is converted into a DC signal at a DC converter112.

The control unit PC30according to the embodiment includes a binarization processing unit1301, an AFM image forming unit1302, an image feature value calculating unit1303, and a quality determining unit1304. A determined result at the quality determining unit1304is outputted to an input/output unit31. The control unit PC30further includes a piezo driver control unit1305that receives the signal from the feedback controller113to control the piezo driver107.

The signal inputted from the feedback controller113to the control unit PC30is formed into a binarized signal waveform at the binarization processing unit1301as illustrated inFIG. 13Bwith reference to a preset threshold.

The binarized signal is received at the AFM image forming unit1302, and stored across the region scanned by the probe120for processing, so that a binarized AFM image1401including a region1402corresponding to the near-field light generating region2on the surface of the thermal assist type magnetic head device4can be obtained.

Subsequently, the binarized AFM image1401is sent to the image feature value calculating unit1304, and an image feature value is calculated. In the example inFIG. 14B, dimensions D11 and D21 are calculated. The dimensions D11 and D21 are in two directions orthogonal to each other in the region1402, which is the feature region of the binarized image1401.

The items of information about the calculated dimensions D11 and D21 are sent to the quality determining unit1304for comparison with preset quality determining reference values, and the quality of the size of the near-field light generating region2corresponding to the region1402on the AFM image1401is determined.

The determined result is outputted to the input/output unit31, and the binarized image1401including the region1402corresponding to the near-field light generating region2is displayed on an image display region1311of a display screen1310of the input/output unit31. Moreover, a sample number display portion1312on which a sample number displayed on the image display region1311is displayed. A dimension D11 and a dimension D21 for the region1402calculated at the image feature value calculating unit1304are displayed on a portion1313and a portion1314, respectively, on the screen1310. A result determined at the quality determining unit1304is displayed on a determined result display portion1315.

FIG. 16is a flowchart of the operation procedures of the thermal assist type magnetic head inspection apparatus described above.

First, the row bar1is taken out of a plurality of the row bars1one by one and carried on the inspection stage (S1601), the row bar1is aligned using a camera103(S1602), and the thermal assist type magnetic head device unit4(the measurement head) formed in the row bar1is moved at the measurement position for positioning the measurement head (the thermal assist type magnetic head device4) (S1603). Subsequently, the piezo driver107controls the Z stage104to approach the probe120of the cantilever unit100to the recording surface of the measurement head (S1604). Subsequently, in the state in which the cantilever unit100is fixed, the piezo driver107drives the Y stage105and the X stage106to move the row bar1in the XY-plane, and the cantilever unit100scans the plane in parallel with the recording surface of the head within a range of a few hundreds nm to a few μm (S1605).

In the scanning, the displacement of the cantilever100is detected as position displacement of a laser on four divided detection surfaces of the displacement sensor110. The laser is emitted from a semiconductor laser device109and reflected off the cantilever100. The differential amplifier111converts the detection signal from the displacement sensor110, which detects the laser, into signals on the four divided detection surfaces of the displacement sensor110according to quantities of light received, and the signals are converted into digital signals at the DC converter112, and inputted to the control unit PC30through the feedback controller113. The signals inputted to the control unit PC30are processed according to the procedures described with reference toFIG. 14Apreviously, and the quality of the physical shape of the near-field light generating region2is determined (S1606).

Subsequently, when finishing the scanning of the probe120over a predetermined region of the thermal assist type magnetic head device unit4, the cantilever is raised, and it is checked whether there is a head to be subsequently measured in the row bar1(S1607). When there is a subsequent head, the head to be subsequently measured is moved on the lower part of the cantilever (S1608), and manipulations from S1604are performed. In the case where there is no head to be subsequently measured in the row bar1, in the state in which the cantilever unit100is raised by the Z stage104, the row bar1that measurement is finished is taken out using a handling unit, not illustrated, and the row bar1is accommodated in a restore tray (S1609). Subsequently, it is checked whether there is an uninspected row bar40on a supply tray, not illustrated (S1610). In the case where there is an uninspected row bar40, the process is returned to S1601, the uninspected row bar40is taken out of the supply tray (not illustrated) (S1611), and the uninspected row bar40is carried to the inspection stage101for performing steps from S1601. On the other hand, in the case where there is no uninspected row bar40in the supply tray, measurement is finished (S1612).

It is noted that in the embodiment described above, it is described in which inspection is performed in the state of the row bar1. However, the embodiment is not limited thereto. Such a configuration may be possible in which a single slider (the thermal assist type magnetic head device4) cut out from the row bar1is placed on a mounting unit114for similar inspection as described above.

According to the embodiment, the near-field light generating region of the thermal assist type magnetic head device can be inspected without emitting an near-field light in a relatively early stage of the manufacturing process steps of the thermal assist type magnetic head device, in a row bar state, for example. Moreover, it is unnecessary to equip a mechanism to emit a near-field light on the inspection apparatus, so that the configuration of the inspection apparatus can be relatively simplified.

In the embodiment described above, as illustrated inFIG. 12, the configuration is described in which the probe120scans the surface of the row bar1, which is a sample. However, such a configuration may be possible in which as illustrated inFIG. 17, a small-gage wire1201of a relatively hard material is fixed to the tip end portion of the probe120and the surface of the row bar1is scanned using the small-gage wire. For a material forming the small-gage wire1201, any one of carbon nanofiber (CNF), a carbon nanotube (CNT), a high density carbon (HDC:DLC), and tungsten (W) may be used. With this configuration, the small-gage wire1201of a relatively hard material contacts the thermal assist type magnetic head device4formed in the row bar1, and the lifetime of the cantilever100can be prolonged more than in the case where the probe120is directly contacted.

Fourth Embodiment

A fourth embodiment of the present invention will be described with reference to the drawings.

The embodiment is different from the third embodiment in that before acquiring an AFM image of a region including a near-field light generating region2of a thermal assist type magnetic head device unit4, a magnetic field is generated on a magnetic field generating region3, and an MFM image of the region including the magnetic field generating region3is acquired. The position of the magnetic field generating region3is identified from the acquired MFM image of the region including the magnetic field generating region3, design information is used to locate a position on the near-field light generating region2with reference to the position of the magnetic field generating region3, and the region including the near-field light generating region2can be reliably scanned by a probe120.

Since the configuration of a thermal assist type magnetic head inspection apparatus according to the embodiment is the same as the configuration of the thermal assist type magnetic head inspection apparatus8000according to the second embodiment described with reference toFIG. 8, except that the control unit PC35is replaced by a control unit PC435illustrated inFIG. 20, the description of the same part is omitted.

A basic configuration of a thermal assist type magnetic head inspection apparatus8000according to the present embodiment is basically similar to the configurations of the apparatuses according to the first embodiment inFIG. 1and the third embodiment. However, as illustrated inFIG. 18, the configuration is different in that a magnetic film1121expressed by a thick line is formed on the surface of a probe1120of a cantilever100. Moreover, the configuration according to the present embodiment is different from the configurations according to the first embodiment and the third embodiment in that the control unit PC435includes an excitation signal output unit4105as similar to the second embodiment and that a signal line301is additionally provided to send a signal, which is outputted from the excitation signal output unit4105and generates a magnetic field on the magnetic field generating region3of the thermal assist type magnetic head device unit4, to the thermal assist type magnetic head device unit4formed in a row bar1as similar to the case of the second embodiment.

In the embodiment, first, the cantilever100is oscillated in the state in which a magnetic field is generated on the magnetic field generating region3of the thermal assist type magnetic head device unit4, an MFM image is acquired by scanning the region including the magnetic field generating region3with the probe1120, and the magnetic field generating region3is identified from the MFM image. Subsequently, the position of the near-field light generating region2is found from design information with reference to the position of the identified magnetic field generating region3. Subsequently, the probe1120scans the region including the found near-field light generating region2while maintaining a constant gap d′ between the tip end portion of the probe1120and the surface of the thermal assist type magnetic head device unit4in the state in which the oscillations of the cantilever100are stopped, and then an AFM image of the region including the near-field light generating region2is acquired. The near-field light generating region2is then identified from the AFM image, and the quality of the physical shape including the size or typical dimensions of the near-field light generating region2is determined.

In the embodiment, in the case where the region including the magnetic field generating region3is scanned, a Z stage104controls the position in the Z-direction of the cantilever100oscillated by an oscillating unit122. Namely, the probe1120is oscillated in such a way that the constant gap d′ is maintained at the lowest end between the tip end portion of the probe1120formed with the magnetic film1121on the surface of the cantilever100and the surface of the thermal assist type magnetic head device4formed in the row bar1. In this state, a piezo driver107receives an oscillation signal from an oscillator102, and controls an X stage106and a Y stage105to move the row bar1in a plane, so that the probe1120mounted on the tip end portion of the cantilever100scans a desired region of the row bar1in a range of a few hundreds nm to a few μm.

Here, in the case where the probe1120scans a location where a material is uniform in the scan range and no magnetic field is generated on the surface of the thermal assist type magnetic head device4formed in the row bar1, which is a sample, the output of a differential amplifier is a waveform oscillated around zero as illustrated in an output waveform1010of a differential amplifier111inFIG. 19. In contrast to this, when a magnetic field is generated from the magnetic field generating region3in the scan range, the magnetic film1121formed on the surface of the probe1120is affected by the effect of the magnetic field, and attracted to the magnetic field generating region3. As a result, the center of the oscillations of the cantilever100is displaced, the center position of the oscillations of light incident to the displacement sensor110which is reflected from the cantilever100is changed, and the output waveform from the differential amplifier111is changed as illustrated in a displacement signal waveform1011.

The displacement signal waveform1010thus changed is imaged using positional information about the X stage106and the Y stage105at the control unit PC435, so that a portion in which the center of the oscillations of the cantilever100is changed from a zero output of the differential amplifier can be detected as the magnetic field generating region3. Positional information about the detected magnetic field generating region3is then compared with design information stored in advance, so that the position of the near-field light generating region2on the X stage106and the Y stage105can be calculated. Thus, it is made possible that the X stage106and the Y stage105are controlled to reliably capture the near-field light generating region2in the visual field of an AFM.

FIG. 20is a diagram of the configuration of the control unit PC435according to the embodiment. The control unit PC435according to the embodiment includes a signal switching circuit unit4101that switches a signal outputted from a DC converter112through a feedback controller113between an MFM image generating unit4102and a binarization circuit unit4301. Moreover, the control unit PC435further controls the probe1120of the cantilever100in such a way that the lowest point for oscillations is at the constant height with respect to the surface of the thermal assist type magnetic head device unit4in the state in which the probe1120of the cantilever100is oscillated. The probe1120is formed with the magnetic film1121on the surface. The control unit PC435includes the MFM image generating unit4102that processes the signal outputted from the differential amplifier111to create an MFM (Magnetic Force Microscope) image when the region including the magnetic field generating region3is scanned in this state. These points are different from the control unit PC30according to the first embodiment and the third embodiment.

The control unit PC435according to the embodiment further includes an AFM image generating unit4302, an image feature value calculating unit4303, a quality determining unit4304, a magnetic field generating position detecting unit4103, a near-field light generating region calculating unit4104, an excitation signal output unit4105, and a piezo driver control unit4106. Here, the components designated with the same numbers as the numbers in the third embodiment inFIG. 14Ahave the same functions described in the third embodiment.

In the configuration described above, the signal switching circuit unit4101switches the destination of the signal outputted from the feedback controller113based on positional information about the X stage106and the Y stage105outputted from the inspection stage101. Namely, when the probe120is scanning the region including the magnetic field generating region3of the thermal assist type magnetic head device unit4, the signal outputted from the feedback controller113is outputted to the MFM image generating unit4102side together with positional information about the X stage106and the Y stage105outputted from the inspection stage101.

On the other hand, when an AFM image of the region including the near-field light generating region2is acquired, the probe1120scans the region including the near-field light generating region2of the thermal assist type magnetic head device unit4in the state in which the oscillations of the cantilever100are stopped and the constant gap d′ is maintained between the probe1120and the surface of the thermal assist type magnetic head device unit4. In this case, the signal outputted from the feedback controller113is outputted to the binarization circuit unit4301side together with positional information about the X stage106and the Y stage105outputted from the inspection stage101. Since signal processing from the binarization circuit unit4301to the quality determining unit4304is the same as processing in the control unit PC30described in the third embodiment, the description is omitted.

The MFM image generating unit4102receives the signal outputted from the DC converter112through the feedback controller113, and forms an MFM image using the signal outputted from the feedback controller113and positional information about the X stage106and the Y stage105outputted from the inspection stage101.

The formed MFM image is sent to the magnetic field generating position detecting unit4103for image processing, and the position of the magnetic field generating region3is identified on the MFM image. Subsequently, positional information about the identified magnetic field generating region3is sent to the near-field light generating region calculating unit4104, and positional information about the near-field light generating region2is obtained from positional information about the magnetic field generating region3based on design information about the thermal assist type magnetic head device unit4. The positional information about the near-field light generating region2is sent to the piezo driver control unit4106. The piezo driver control unit4106controls the piezo driver107to drive the X stage106and the Y stage105based on the positional information about the near-field light generating region2, and positions the near-field light generating region2in the range of the scan region of the probe120formed with the magnetic film1121on the surface.

Since the procedures of scanning the region including the near-field light generating region2with the probe1120to acquire an AFM image and evaluating the physical shape of the near-field light generating region2are the same as the procedures described in the third embodiment, the description is omitted.

The operation procedures of the thermal assist type magnetic head inspection apparatus8000according to the embodiment are the same as the operation procedures described in the third embodiment with reference toFIG. 16, except S1605and S1606. The portions different from the flowchart of the third embodiment inFIG. 16will be described with reference toFIG. 21.

After completion in S1604, the excitation signal output unit4105receives positional information about the X stage106and the Y stage105outputted from the inspection stage101, outputs a signal to generate a magnetic field on the magnetic field generating region3of the thermal assist type magnetic head device unit4formed in the row bar1through the signal line301, and generates a magnetic field on the magnetic field generating region3(S16051). Subsequently, the oscillating unit122drives the cantilever100formed with the magnetic film121on the surface to oscillate the cantilever100at a constant amplitude. In the oscillation, the position of the cantilever100in the Z-direction is adjusted by the Z stage104. Thus, the probe1120fixed near the tip end portion of the cantilever100scans the region including the magnetic field generating region3on which a magnetic field is generated in the state in which the constant gap d′ is maintained at the lowest point for oscillations with respect to the thermal assist type magnetic head device unit4(S16052), and an MFM image of the magnetic field generating region3is created at the MFM image forming unit4102(S16053).

Subsequently, the position of the magnetic field generating region3is identified on the created MFM image, and the position of the near-field light generating region2(the amount of movement to the near-field light generating region2) on the X stage106and the Y stage105is calculated from the position relationship between the identified positional information and the positions of the magnetic field generating region3and the near-field light generating region2on design data stored in advance. The X stage106and the Y stage105are then driven by the piezo driver107based on the calculated amount of movement, and the near-field light generating region2is moved into the scan range of the probe1120. Subsequently, the signal to generate a magnetic field on the magnetic field generating region3of the thermal assist type magnetic head device unit4formed in the row bar1from the signal line301is interrupted, and the output of the oscillating unit122is stopped to halt the oscillations of the cantilever100. Subsequently, as similar to the case of the first embodiment, the probe1120scans the region including the near-field light generating region2in the state in which the constant gap d′ is maintained between the cantilever100and the thermal assist type magnetic head device unit4(S16054), and an AFM image of the region including the near-field light generating region2is formed at the AFM image forming unit4302(S16055).

Moreover, the AFM image is processed to calculate image feature values D1 and D2 of the near-field light generating region2(S6061), and the feature values D1 and D2 are compared with preset reference values to evaluate the physical shape of the near-field light generating region2for determining the quality (S6062). Lastly, the found results are outputted to an input/output unit31together with the MFM image and the phase difference image (S6063).

It is noted that in the embodiment described above, it is described in which inspection is performed in the state of the row bar1. However, the embodiment is not limited thereto. Such a configuration may be possible in which a single slider (the thermal assist type magnetic head device4) cut out from the row bar1is placed on a mounting unit114for similar inspection as described above.

According to the embodiment, the near-field light generating region of the thermal assist type magnetic head device can be inspected without emitting a near-field light in a relatively early stage of the manufacturing process steps of the thermal assist type magnetic head device, in a row bar state, for example. Moreover, it is unnecessary to equip a mechanism to emit a near-field light on the inspection apparatus, so that the configuration of the inspection apparatus can be relatively simplified.

Also in the embodiment, as similar to the description in the third embodiment with reference toFIG. 17, such a configuration may be possible in which the tip end portion of the probe1120includes a small-gage wire formed of a relatively hard material (corresponding to the small-gage wire1201inFIG. 17), a magnetic film is formed on the surface of the small-gage wire, and the surface of the row bar1is scanned using the small-gage wire formed with the magnetic film on the surface. For a material of forming the small-gage wire, any one of carbon nanofiber (CNF), a carbon nanotube (CNT), a high density carbon (HDC:DLC), and tungsten (W) may be used. With this configuration, the small-gage wire1201of a relatively hard material contacts the thermal assist type magnetic head device4formed in the row bar1, and the lifetime of the cantilever100can be prolonged more than in the case where the probe1120is directly contacted.

As described above, the invention made by the present inventor is described specifically based on the embodiments. However, it is without saying that the present invention is not limited to the embodiments, and can be modified and altered variously within the scope not deviating from the teachings.