Patent Application
20140092717
The present invention relates to a method for inspecting a thermal assist type magnetic head which inspects thermal assist type magnetic head, and an apparatus for inspecting a thermal assist type magnetic head, and in particular to, in the techniques such as optical microscopes, a method and apparatus for inspecting thermal assist type magnetic head which is capable of inspecting the state of generation of near-field light generated by a thermal assist type magnetic head which cannot be inspected.
As apparatuses which non-destructively inspect magnetic heads, a method using an optical microscope, a method using a scanning electron microscope (SEM), a method using an atomic force microscope (AFM), and a method using a magnetic force microscope (MFM), among others, have been employed.
Each of the methods mentioned above has its merits and demerits. Since a magnetic field generated by a magnetic head for writing on a hard disk can be non-destructively inspected, the method using a magnetic force microscope (MFM) is advantageous over the methods using observation means by other systems.
Using this magnetic force microscope (MFM), measuring the effective track width of a write track in a state of a row bar in which a plurality of magnetic head elements are placed side by side before the magnetic head elements formed on a wafer are separated individually, for example, is described in Japanese Unexamined Patent Publication No. 2010-175534 (patent document 1). That is, patent document 1 describes generating a magnetic field by applying a current to a magnetic head circuit pattern of a sample, i.e., a row bar, and a magnetic probe attached to a cantilever is approached to this magnetic field generating by performing two-dimensional measurement of the magnetic field generated by the sample by two-dimensionally scanning the cantilever to detect the displacement magnitude of the probe of the cantilever.
Moreover, Japanese Unexamined Patent Publication No. 2009-230845 (patent documents 2) describes a conventional magnetic head inspection as follows: in a magnetic head inspection, a record signal (signal for magnetization) is inputted into a thin film magnetic head in a magnetic head row bar state from a bonding pad. The situation of the magnetic field generated from the recording head (element) contained in the thin film magnetic head is observed while the thin film magnetic head is scanned and moved in the position corresponding to the floating height of the magnetic head. The situation of this magnetic field is directly observed under a magnetic force microscope (MFM), a scanning hall probe microscope (SHPM), or a scanning magneto-resistive effect microscope (SMRM). This allows measurement of not physical forms but the magnetic field configuration generated, and non-destructive inspection of magnetic effective track widths. Japanese Unexamined Patent Publication No. 2009-230845 (patent documents 2) describes achieving measurement of the effective track widths in the state of a row bar by using a magnetic force microscope, which has been only possible in the state of HGA or pseudo-HGA using a spin stand.
In contrast, as new techniques for next-generation hard disks for which dramatically higher capacities are demanded, magnetic recording methods by thermal assist have been drawing attention and are increasingly developed in many companies. Increasing densities and capacities of hard disks requires reduction in their track widths, which are said to have almost reached their limits in magnetic heads of conventional systems, but employing a magnetic head of the thermal assist method using near-field light as a heat source allows realization of a track width of about 20 nm.
In this thermal assist magnetic recording head, near-field light is generated using a conductive structure having such a cross sectional shape that the width in the direction perpendicular to the polarization direction of incident light propagating through a waveguide gradually decreases towards the vertex where the near-field light is generated, and, its width decreases gradually or stepwise towards the vertex where the near-field light is generated in the direction of travel of the incident light. A configuration in which the waveguide is disposed next to a structure having conductivity, and near-field light is generated via surface plasmon generated on the side face the structure having conductivity is described in Japanese Unexamined Patent Publication No. 2011-146097 (patent document 3).
However, the effective intensity distribution and size of the near-field light which serve as significant factors for this track width cannot be measured from surface shapes observed with optical microscopes and SEMs. Therefore, inspection methods are important issued which are left unsolved.
In contrast, as a technique for detecting this near-field light, patent document 4 discloses “Near-field optical microscope (also referred to as SNOM: Scanning Near-field Optical Microscopy, NSOM: Near-field Scanning Optical Microscopy, NOM: Near-field Optical Microscopy)”, which can detect near-field light and determine its configuration by approaching a scanning type probe to the near-field light, and scattering the near-field light.
Patent document 1 describes measurement of the two-dimensional magnetic field distribution formed by individual magnetic head elements in a row bar of a magnetic head by performing two-dimensional scanning with a cantilever having a probe, but the document does not refer to the configuration for measuring the near-field light and magnetic field generated by a thermal assist type magnetic head, and a method for the same.
In conventional magnetic recording, the size of a magnetic field generation part is the track width, and therefore the track width of the head can be inspected by measuring a magnetic field according to the method in patent document 1. However, it is difficult for such a method to inspect a thermal assist head, in which the size of near-field light generated is the track width.
Moreover, in the magnetic head inspection apparatus which inspects the magnetic effective track width by measuring the shape of the magnetic field generated in the state of the row bar described in patent document 2, the constitution and method for measuring near-field light and magnetic field generated by a thermal assist type magnetic head are not mentioned.
In contrast, patent document 3 describes the structure of a thermal assist magnetic recording head and a magnetic recording apparatus incorporating this head, but the document does not refer to inspecting near-field light and magnetic field generated by the thermal assist magnetic recording head.
Furthermore, patent document 4 describes detecting the near-field light and the other light while distinguishing both from each other in the vicinity of a near-field light emitting element, but does not refer to inspecting the near-field light and magnetic field generated by a thermal assist magnetic recording head.
The present invention provides a method and an apparatus for inspecting a thermal assist type magnetic head element which allows measurement of a magnetic field generated by a thermal assist type magnetic head and a near-field light generation region efficiently and highly accurately.
In order to solve the problems described above, in the present invention, the apparatus for inspecting a thermal assist type magnetic head is configured to include a scanning probe microscope unit having X and Y tables for mounting a thermal assist type magnetic head element thereon and being movable in an XY plane, and a cantilever having a probe formed at a tip portion and a surface of the probe a magnetic film is formed, a prober unit which supplies an alternating current to a terminal formed on the thermal assist type magnetic head element mounted on the X and Y tables, and applies a drive current or drive voltage to a near-field light emitting part formed on the thermal assist type magnetic head element, a scattered light detection unit which scans the surface of the thermal assist type magnetic head element with the probe of the cantilever, and detects scattered light generated from the probe when the probe is in the vicinity of a generation region of near-field light generated from the near-field light emitting part while the X and Y tables are moving and applying the drive current or drive voltage to the near-field light emitting part formed on the thermal assist type magnetic head element from the prober unit, an imaging unit which images the thermal assist type magnetic head element including the near-field light emitting part, and a signal processing unit which inspects the thermal assist type magnetic head element by processing an output signal outputted from the scattered light detection unit and an output signal outputted from the scanning probe microscope unit by scanning the surface of the thermal assist type magnetic head element with the probe while moving the X and Y tables and supplying an alternating current to the terminal formed on the thermal assist type magnetic head element from the probe unit.
Moreover, in order to solve the problems described above, in the present invention, the method for inspecting a thermal assist type magnetic head includes mounting a thermal assist type magnetic head element on X and Y tables of a scanning probe microscope, the scanning probe microscope comprising a cantilever and the X and Y tables, the cantilever having a probe in a tip portion thereof, the probe having a magnetic film formed on the surface thereof, the X and Y table being movable in an XY plane; providing an alternating current to a terminal formed on the thermal assist type magnetic head element mounted on the X and Y tables to generate a magnetic field in the thermal assist type magnetic head element; in a state that the magnetic field is generated in the thermal assist type magnetic head element, determining the distribution of the magnetic field generated by scanning the surface of the thermal assist type magnetic head element with the probe of the cantilever of the scanning probe microscope; applying a drive current or drive voltage to a near-field light emitting part formed on the thermal assist type magnetic head element mounted on the X and Y tables to generate near-field light from the near-field light emitting part; in a state that near-field light is generated from the near-field light emitting part, scanning the surface of the thermal assist type magnetic head element with the probe of the cantilever of the scanning probe microscope to determine a light emission region of the near-field light generated from the near field light emitting part and its distribution; and judging a quality of the thermal assist type magnetic head based on information of the distribution of the magnetic field and the determined light emission region and distribution of the near-field light.
Furthermore, in order to solve the problems described above, in the present invention, the method for inspecting a thermal assist type magnetic head includes mounting a thermal assist type magnetic head element on X and Y tables of a scanning probe microscope, the scanning probe microscope comprising a cantilever and the X and Y tables, a cantilever having a probe in a tip portion thereof, the probe having a magnetic film formed on the surface thereof, the X and Y table being movable in an XY plane; in a state that an alternating current is provided to a terminal formed on the thermal assist type magnetic head element mounted on the X and Y tables to generate a magnetic field in the thermal assist type magnetic head element; scanning the surface of the thermal assist type magnetic head element with the probe of the cantilever of the scanning probe microscope in a first direction to detect a generation region of the magnetic field; in a state that a drive current or drive voltage is applied to a near-field light emitting part formed on the thermal assist type magnetic head element mounted on the X and Y tables to generate a near-field light from the near-field light emitting part, scanning the surface of the thermal assist type magnetic head element with the probe of the cantilever of the scanning probe microscope in a second direction which is opposite to the first direction to determine a light emission region of the near-field light; and judging a quality of the thermal assist type magnetic head based on information of the detected generation region of the magnetic field and the determined light emission region of the near-field light.
According to the present invention, by scanning the inspection region for the magnetic field and near-field light generated from the thermal assist type magnetic head element with the scanning probe microscope once, the magnetic field and near-field light generated from the thermal assist type magnetic head element can be inspected highly accurately, and therefore an increase in the inspection efficiency of the thermal assist type magnetic head element is achieved.
These features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.
The present invention relates to a method and apparatus for inspecting a magnetic head element using, in a state of a row bar before the thermal assist type magnetic head element is individually separated, or in a state of a head assembly that the thermal assist type magnetic head elements are cut from the row bar and separated individually and mounted on a gimbal, an apparatus which inspects light emission state of near-field light generated by the thermal assist type magnetic head element and the distribution of a magnetic field applying a scanning probe microscope.
The mode for carrying out the invention (embodiment) will be described below with reference to drawings as for the case of inspecting a row bar before thermal assist type magnetic head elements are individually separated.
The inspection unit 100, the monitor unit 200 and the transfer unit 300 are covered by a sound-proof box 600 to provide sound insulation so that sound from outside does not affect the inspection.
The magnetic head element inspection apparatus 1000 is configured by disposing the inspection unit 100 and the transfer unit 300 on a vibration isolating table 500 covered with the sound-proof box 600.
The transfer unit 300 includes a handling robot 310 and a guide rail 320 which guides the movement of the handling robot 310 in the X direction, a supply tray 331 on which a row bar 40 is mounted before being inspected and a non-defective product collection tray 332 on which the row bar is mounted after being inspected, and the tray rest 330 having a defective product collecting tray 333 mounted thereon.
In
The inspection unit 100 of the thermal assist type magnetic head according to this embodiment is configured to perform predetermined inspection on this row bar 40 as a workpiece. About 20 to 30 pieces of the row bar 40 are arranged and accommodated on the supply tray 331 shown in
The inspection unit 100 of the magnetic head element inspection apparatus 1000 according to this embodiment is based on a scanning probe microscope. The inspection unit 100 is capable of moving between the sample delivery station H and the sample inspection station M along the guide rail 150, and includes an inspection stage 101 which is capable of moving in the X-Y direction, and an X stage 106 and a Y stage 105 which are mounted on the inspection stage 101, capable of moving the row bar 40 in the X and Y directions for a minute distance, and are driven by a piezo element (not shown).
The row bar 40 is positioned in the X direction as a side face thereof in the longitudinal direction is pressed against a reference face 1141 provided on a step portion 1142 of a rest 114 for positioning the row bar 40 provided on the top face of on the Y stage. The row bar 40, as shown in
In the inspection unit 100, as shown in
The inspection unit 100 further includes the cantilever 10, a vibrator 122, a near-field light detection optical system 115, a displacement detecting element 130, a probe unit 140, an oscillator 102, a piezo driver 107, a differential amplifier 111, DC converter 112, a feedback controller 113, and a control unit 30. Moreover, the control unit 30 includes a near-field light detection control system 530 which controls the near-field light detection optical system 115.
The position of the cantilever 10 in the Z direction is controlled by the Z stage, and is vibrated at a predetermined frequency and predetermined amplitude by the vibrator 122 fixed to the Z stage 104.
The displacement detecting element 130 detects the state of vibration of the cantilever 10. The displacement detecting element 130 includes a laser light source 109 and a displacement sensor 110, and irradiates the cantilever 10 with a laser emitted from the laser light source 109, and detects the light regularly reflected at the cantilever 10 by a displacement sensor 110. A signal outputted from the displacement sensor 110 is transferred to the control unit 30 via the differential amplifier 111, the DC converter 112, and the feedback controller 113 and processed.
The probe unit 140 receives a signal 301 from the control unit 30, applies power and laser to an element which is a target of inspection of the row bar 40 mounted on the rest 114, and generates a magnetic field and near-field light on the element which is a target of inspection.
The near-field light detection optical system 115 detects the near-field light generated from the element which is a target of inspection of the row bar 40, and outputs detected signal 302 to the control unit 30a.
The piezo driver 107 oscillates a piezo driving signal in response to a signal of the oscillator 102, and drives the X stage 106, the Y stage 105, and the Z stage 104.
In the above-described constitution, the control unit 30 controls the X stage 106, the Y stage 105, and the Z stage 104 via piezo driver 107 based on an image of the row bar 40 taken by the camera 103 to perform positioning adjustment so that the row bar 40 is in a predetermined position. When the positioning adjustment of the row bar 40 is completed, the probe unit 140 is driven based on an instruction from the control unit 30, and a tip portion of a probe 141 comes into contact with the magnetic head element electrodes 41 and 42 formed on the row bar 40.
The probe unit 140 as its side view is shown in
In such a state, the X stage 106 and the Y stage 105 are driven so that a scanning region 401 including the magnetic field generating part 502 is scanned with the cantilever 10, and a signal obtained by detecting changes in the amplitude of the cantilever 10 by the displacement detecting element 130 is processed by the control unit 30, whereby the distribution of the magnetic field generated from the write magnetic field generating part 502 of the row bar 40 can be measured at a high speed, and the width of the track to be written can be measured. The row bar 40 is sucked by a suction means (not shown) provided at the rest 114.
The probe card 141 is so configured to be movable in the X direction by a drive unit 143, and drives to perform the operation of sequentially contact and detachment of the tip portions 1421 and 1422 of the probe 142 and a number of magnetic head element electrodes 41 and 42 formed on the row bar 40.
In
The cantilever 10 which vibrates by being driven by the vibrator 122 is, at the lowest end of vibration, positioned by the Z stage 104 so that a tip portion 5 of a probe 4 formed near the tip portion of the cantilever 10 is positioned at a height corresponding to a head floating height Hf from the surface of the thermal assist type magnetic head element portion 501 formed on the row bar 40. On the surface of the probe 4, a thin magnetic film 2 (for example, Co, Ni, Fe, NiFe, CoFe, NiCo, etc.) and minute particles or a thin film 3 of precious metals (for example, gold, silver, platinum, etc.) or alloys containing precious metals are formed.
In the thermal assist type magnetic head element portion 501, the write magnetic field generating part 502 and a near-field light generating part 504 are formed.
The near-field light detection optical system 115 is configured to include an objective lens 511, a half mirror 512, an LED light source 513, an imaging lens system 510 including an imaging lens 514, a mirror with a pin hole 522 having a pin hole 521 formed at the center, a light detector 523 which detects the light which has passed through the pin hole 521 of the mirror with a pin hole 522, a relay lens system 524 which causes an optical image formed in the imaging lens system 510 and reflected at the mirror with a pin hole 522 to be formed, and a CCD camera 525 which detects an optical image formed in the relay lens system 524.
Moreover, the near-field light detection control system 530 constituting a part of the control unit 30 in order to generate a near-field light 505 from the near-field light generating part 504 of the thermal assist type magnetic head element portion 501, a laser driver 531 which applies a pulse drive current or a pulse drive voltage 5311 to the near-field light generating part 504 via a waveguide which is not shown, a pulse modulator 532 which adjusts an oscillating frequency of a pulse drive current or the pulse drive voltage 5311 oscillating from the laser driver 531, a control substrate 533 which controls the laser driver 531 and the pulse modulator 532, a bias power source 534 which applies a bias voltage applied to the light detector 523, a lock-in amplifier 535 which draws a signal in synchronization with the vibration of the cantilever 10 from a signal detected by the light detector 523, a control PC 536 which receives an output signal from the light detector 523 detected by the lock-in amplifier 535 and the output signal from the CCD camera 525. The output from the control PC 536 is indicated on a monitor screen 31 of the control unit 30.
In the constitution of the near-field light detection optical system 115 and the near-field light detection control system 530 as described above, the pulse drive current or pulse drive voltage 5311 controlled by a pulse modulation signal from the pulse modulator 532 controlled by the control substrate 533 from the laser driver 531 applies a pulse drive current or pulse drive voltage to the near-field light generating part 504 of the thermal assist type magnetic head element portion 501 via a waveguide which is not shown, so that the near-field light 505 is generated on the surface of the thermal assist type magnetic head element portion 501.
Although the near-field light 505 itself is generated only in a limited region of the upper face of the near-field light generating part 504, if minute particles of precious metals or alloys containing precious metals or the thin film 3 formed on the magnetic film 2 on the surface of the probe 4 of the cantilever 10 get into the generation region of the near-field light 505, scattered light is generated by the near-field light 505 from minute particles of precious metals or alloys containing precious metals or the thin film 3. A scattered light image is formed on the surface of the probe 4 of the cantilever 10 on an image plane of the imaging lens 514 by the scattered light, of this scattered light generated, which has passed through the half mirror 512 which is incident in the objective lens 511 of the imaging lens system 510.
The mirror with a pin hole 522 is placed so that the pin hole 521 is positioned at a place where the scattered light image is formed on the surface of the probe 4 on this image plane. Since the size of the probe 4 is sufficiently smaller than the size of the pin hole 521, the scattered light image on the surface of the probe 4 passes through the pin hole 521 and is detected by the light detector 523. In contrast, the light which becomes noise coming from a position other than the surface of the probe 4 reaches a position shifted from the pin hole 521 on the image plane and thus cannot pass through the pin hole 521, and is blocked against the light detector 523. By employing such a constitution, the emission intensity of the scattered light generated on the surface of the probe 4 by the near-field light generated from the near-field light generating part 504 of the thermal assist type magnetic head element portion 501 can be detected by the light detector 523 with a reduced influence of the light which serves as noise.
In contrast, of the light emitted from the LED light source 513, the light reflected from the half mirror 512 to the side of the objective lens 511 passes through the objective lens 511 and illuminates the probe 4 of the cantilever 10 and the thermal assist type magnetic head element portion 501. The image in the region irradiated with this illumination light is formed in the vicinity of the face on which the mirror with a pin hole 522 is placed by the imaging lens system 510 and, the image reflected on the mirror with a pin hole 522 is incident in the relay lens 524 and is imaged again on the outgoing side of the relay lens 524. By installing the detector face of the CCD camera 525 so that it coincides with the image plane on the exit side of this relay lens 524, the images of the probe 4 of the cantilever 10 and the thermal assist type magnetic head element portion 501 are imaged with a CCD camera 525. Imaging by this CCD camera 525 is performed before the initiation of the inspection of the thermal assist type magnetic head element portion 501, that is, in a state that a near-field light 503 is not generated from the near-field light generating part 504.
Moreover, since the image taken by the CCD camera 525 is such that the image of the portion of the pin hole 521 of the mirror with a pin hole 522 is missed, as shown in
The imaging lens system 510 is provided with the drive unit 5121 for removing the half mirror 512 from the optical axis of the imaging lens system 510. First, in a state that the half mirror 512 is installed on the optical axis of the imaging lens system 510, the image taken with the CCD camera 525 is displayed on the monitor screen 31 to check and adjust the position of the pinhole 521. Second, after checking and adjusting the position of the pinhole 521 are completed, the half mirror 512 is removed from the optical axis of the imaging lens system 510 by the drive unit which is not illustrated, and a number of thermal assist type magnetic head elements formed on the row bar 40 is inspected sequentially. That is, the half mirror 512 is positioned on the optical axis of the imaging lens system 510 in confirmation and adjustment of the position of the pin hole 521, while when a number of thermal assist type magnetic head elements formed on the row bar 40 are sequentially inspected, the half mirror 512 is retreated to a position which is off the optical axis of the imaging lens system 510. Thus, by retreating the half mirror 512 to a position which is off from the optical axis of the imaging lens system 510 when the thermal assist type magnetic head elements are sequentially inspected, the light detector 523 can detect during the inspection of thermal assist type magnetic head elements without reducing the quantity of light of the scattered light generated at the probe 4 of the cantilever 10. As a result, the scattered light generated at the probe 4 can be detected in high sensitivity.
In a state of being set as mentioned above, the near-field-light detection optical system 115 is controlled by the control part 30, the probe 141 of the probe unit 140 is driven by the drive unit 143, the tip portions 1421 and 1422 of the probe 141 come into contact with the magnetic head element electrodes 41 and 42, respectively, formed on the row bar 40. Moreover, the waveguide from the laser driver 531 and the near-field-light generating part 504 of the thermal assist type magnetic head element 501, which are not illustrated, are brought into connection.
Accordingly, the signal 301 (alternating current 1431, and pulse drive currentor pulse drive voltage 5311) outputted from the control unit 30 is brought into such a state that it can be provided to the thermal assist type magnetic head elements formed on the row bar 40. In this state, the thermal assist type magnetic head element 501 of the target of inspection on the row bar 40 sucked by a suction means (not shown) provided at the rest 114 becomes capable of generating a magnetic field from the write magnetic field generating part 502 and generating near-field light from the near-field light emitting part 504.
As shown in
As shown in
That is, the thin magnetic film 2 formed on the surface of the probe 4 determines the sensitivity and resolution in measuring the magnetic field, and picks up the magnetic field of the measured object in measuring the magnetic field 503 generated in the magnetic field generating part 502. Moreover, minute particles of precious metals (for example, gold, silver, etc.) or alloys containing precious metals or the thin film 3 formed on the surface of the probe 4 amplifies the scattered light 506 generated from the minute particles or the thin film 3 by the localized surface plasmon enhancing effect when the probe 4 enters the generation region of the near-field light 505, and to attain a degree of amount of light which can be detected by the near-field light detection optical system 115. However, the minute particles or thin film 3 of precious metals or alloys containing precious metals is not always necessary, and if the magnetic film 2 is sufficiently thin, the scattered light generated from the surface of the probe 4 can be amplified to a degree of amount of light which can be detected by the near-field light detection optical system 115 by the near-field light by the localized surface plasmon enhancing effect when the near-field light falls on the magnetic film 2.
As shown in
Herein, the displacement sensor 110 has a light receiving surface divided into four divisions, and when the laser is radiated from the semiconductor laser element 109 in a state that the cantilever 10 is not vibrated by the vibrator 122, that is, in a static state, placed in such a position that the reflected light from the cantilever 10 is equally incident into the four divisions of the light receiving surface. The differential amplifier 111 performs a predetermined arithmetic processing on differential signals of the four electrical signals outputted from the displacement sensor 110 and outputs to the DC converter 112.
That is, the differential amplifier 111 outputs displacement signals corresponding to differences between the four electrical signals outputted from the displacement sensor 110 to the DC converter 112. Therefore, in a state that the cantilever 10 is not vibrated by the vibrator 122, the output from the differential amplifier ill becomes zero. The DC converter 112 is constituted by an RMS-DC converter (Root Mean Squared value to Direct Current converter) which converts the displacement signals outputted from the differential amplifier 111 into direct current signals of the root mean square values.
The displacement signals outputted from the differential amplifier 111 are signals which are corresponding to displacement of the cantilever 10, and become alternating signals since the cantilever 10 is vibrating during the inspection. The signal outputted from the DC converter 112 is output to the feedback controller 113. The feedback controller 113 outputs the signals outputted from DC converter 112 to the control part 30 as signals for monitoring the magnitude of the present vibration of the cantilever 10, while it outputs the signals outputted to the piezo driver 107 from the DC converter 112 through the control unit 30 as a control signal of the Z stage 104 for adjusting the magnitude of excitation of the cantilever 10. This signal is monitored by the control unit 30, and depending on the value, the initial position of the cantilever 10 is adjusted before the initiation of measurement by controlling a piezo element (not shown) which drives the Z stage 104 by the piezo driver 107.
Near-field light is generated from the near-field light generating part 504 by the pulse drive current or pulse drive voltage 5311 oscillating from the laser driver 531. Herein, the luminous efficiency of the near-field light in the near-field light generating part 504 is about a few percent of laser incidence energy. The rest is converted into thermal energy, and the near-field light generating part 504 and vicinity generate head. When a thermal assist type magnetic head element is incorporated in a magnetic disk and writes data in the magnetic disk, the magnetic disk is rotating at a speed of thousands of rpm, and the near-field-light generating part of the thermal assist type magnetic head element is air-cooled by the air trapped between the magnetic disk and the thermal assist type magnetic head element, whereby a rise in the temperature is suppressed. However, since there is no air cooling mechanism in inspecting a thermal assist type magnetic head element, when inspecting by generating near-field light, the temperature of the near-field-light generating part rises. For example, in the case where continuous wave laser generated by applying power of 50 W to the laser diver 531 is incident in the near-field light generating part 504, the temperature of the near-field light generating part is increased to about to 200 to 300° C. in the near-field light generating part 504 and its vicinity.
To reduce the influence of this heat generation, in this Example the detection of the near-field light generated in the thermal assist type magnetic head element portion 501 and the detection of the magnetic field are performed alternately, so that the time of continuously generating the near-field light is shortened as much as possible. Moreover, the laser generated by the near-field light generating part 504 to generate the near-field light is set to be a pulse drive current or pulse drive voltage, and the laser driver 531 is controlled to keep the duty of 25% or lower to suppress heat generation of the near-field light generating part 504.
In this Example, by driving the X stage 106 and Y stage 105 by the piezo driver 107 in a state that the cantilever 10 is vibrated at a predetermined frequency by the vibrator 122, the inspection region 401 of the thermal assist type magnetic head element portion 501 as shown in
In the case where the X stage 106 is scanned while the cantilever 10 is vibrated up and down, this inspection region is scanned from the left side to the right side of the figure along a dotted line 402 in the X direction (the heat assist type head element 501 is moved in the +X direction in
In contrast, when the X stage 106 is scanned in the X direction to the left side from the right side in the figure along a dotted line 403 (when heat assist type head element 501 is moved in the −X direction in
Accordingly, the mode is switched between the MFM mode inspection and AFM mode inspection depending on the direction of the scanning of the thermal assist type magnetic head element portion 501 in the X direction relative to the cantilever 10 during the inspection, and application of the pulse drive current or pulse drive voltage 5311 to the near-field light emitting part 504 is stopped while inspection is performed on the MFM mode, whereby a rise in the temperature of the thermal assist type magnetic head element portion 501 by the heat generation from the near-field light emitting part 504 can be suppressed, and occurrence of damage in the thermal assist type magnetic head element portion 501 can be avoided.
The height of the probe 4 of the cantilever 10 relative to the surface of the inspection region 401 of the thermal assist type magnetic head element portion 501 is switched by the MFM mode and the AFM mode. That is, when inspection is performed on the AFM mode, the height of the probe 4 of the cantilever 10 relative to the surface of the inspection region 401 of the thermal assist type magnetic head element portion 501 is set to a height corresponding to the head floating height Hf for writing in a magnetic disk. While on the other hand, in the case of the MFM mode, the height of the probe 4 becomes greater than Hf (the gap between the surface of the inspection region 401 and the tip portion of the vibrating probe 4 at its lowest is set to be greater than Hf). This switching of height is performed by driving the Z stage 104 by the piezo driver 107.
It should be noted that in the example shown in
Next, a method for detecting the magnetic field generated from the thermal assist type magnetic head element portion 501 during the MFM mode inspection will be described.
First, the Z stage 104 is controlled by the piezo driver 107 so that the probe 4 is at the height position (gap) relative to the thermal assist type magnetic head element portion 501 during the MFM mode inspection. In contrast, when an alternating current 1431 is applied in a state that the tip portions 1421 and 1422 of the probe 142 is driven by the drive unit 143 of the probe unit 140 and are in contact with the electrodes 41 and 42 formed on the row bar 40, respectively, the write magnetic field 503 occurs from the write magnetic field generating part 502 of the write circuit portion 43. At this time, the output of the laser from the laser driver 531 to the near-field-light generating part 504 is shut off. Next, in a state that the cantilever 10 is vibrated by the vibrator 122, the X stage 106 on which the row bar 40 is mounted is moved in the +X direction in
If the probe 4 of the cantilever 10 enters into the write magnetic field 503 generated by the write magnetic field generating part 502, a magnetic substance 2 of the thin film formed on the surface of the probe 4 is magnetized, and the probe 4 receives magnetic force, whereby the oscillating state of the cantilever 10 changes. Changes in this vibration are detected by the displacement sensor 110 in
By detecting the output of this displacement sensor 110 by the differential amplifier 111, changes in the oscillating state of the cantilever 10 depending on the position to be scanned can be detected. By processing this detected signal in the control part 30, it is possible to detect the intensity distribution of the write magnetic field 503 generated by the magnetic field generating part 502 of the thermal assist type magnetic head element portion 501. By comparing the intensity distribution of this detected write magnetic field with the reference value set in advance, the quality of the write magnetic field generating part 502 can be judged.
After the probe 4 is moved by driving the X stage 106 by a distance of the X direction of the inspection region 401, the driving of the X stage 106 is stopped to stop the inspection in the MFM mode. The mode is then switched to the AMF mode, and the X stage 106 is moved in the opposite direction.
Next, a method for detecting the state of generation of the near-field light from the thermal assist type magnetic head element portion 501 during the AFM mode inspection will be described. During the AFM mode inspection, in a state that the cantilever 10 is driven and vibrated by the vibrator 122, the inspection region 401 is scanned by the probe 4 along the dotted line 403 in the −X direction, changes in amplitude of the cantilever 10 during scanning is detected by the displacement detecting element 130 to obtain the information of unevenness on the surface of the inspection region 401, and at the same time, the scattered light generated from the probe 4 while scanning the upper face of the near-field light generating part 504 is detected by the near-field light detection optical system 115. To perform the AFM mode inspection, first, the Z stage 104 is controlled by the piezo driver 107 so that the probe 4 is in a height position (gap) relative to the thermal assist type magnetic head element portion 501 during the AFM mode. Second, the pulse drive current or pulse drive voltage 5311 outputted from the laser driver 531 is applied to the near-field light generating part 504 of the thermal assist type magnetic head element portion 501 from the probe unit 140.
In such a state, as shown in
After the X stage 106 is driven and scanned in the direction opposite to that in the MFM mode by a distance of the X direction of the inspection region 401 by the probe 4, driving of the X stage 106 is stopped to stop the inspection in the AFM mode. Next, driving the Y stage 107 in the Y direction by a pitch, and then driving the X stage 106 in the same direction as that in the MFM mode of the previous time and scanning the same in the X direction of the inspection region 401 by the probe 4 is repeated, to scan the entire surface of the inspection region 401 by the probe 4.
By scanning the entire surface of the inspection region 401 once with the probe 4 in such a manner, the detection of the magnetic field generation region generated from the magnetic field generating part 502 of the thermal assist type magnetic head element portion 501 and the detection of the scattered light generation region from the probe 4 by the near-field light generated from the near-field light generating part 504 are enabled.
By processing this detection signal in the control unit 30, the distribution of the magnetic field generated from the magnetic field generating part 502 and the distribution of the intensity of the near-field light generated from the near-field light generating part 504 can be determined. By comparing the distribution of this determined magnetic field and the distribution of intensity of the near-field light with the reference data set in advance, the quality of the state of the magnetic field generated from the magnetic field generating part 502 and the emission of the near-field light from the near-field light generating part 504 (the intensity of magnetic field, distribution of magnetic field, the shape and position of the magnetic field generation region, intensity of near-field light, distribution of near-field light, the shape and position of the near-field light generation region, etc.) can be judged.
Furthermore, the spatial relationship between the write magnetic field (alternating magnetic field) 503 generated by the magnetic field generating part 502 of the thermal assist type magnetic head element portion 501 and the heat assist type light (near-field light) 505 generated from the near-field light generating part 504 can be also measured. Accordingly, the inspection of the write magnetic field of the thermal assist type magnetic head element and the intensity distribution of the near-field light and the spatial relationship of both can be measured in the earliest possible stage during the manufacturing process.
The procedure of inspecting the row bar 40 using the magnetic-head-element inspection equipment 1000 which has the inspection unit 100 of the thermal assist type magnetic head mentioned above will be described based on the flowchart shown in
First, one row bar 40 is taken from the supply tray 331 of the tray rest 330 by the handling unit 310, and in a state that the row bar 40 is pressed against the reference face 1141 of the rest 114 of the inspection unit 100 of the thermal assist type magnetic head element which is standing by at the sample delivery station H, the row bar 40 is mounted on the rest 114 (S801). Next, the inspection stage 101 moves along the guide rail 150, and reaches the sample inspection station M (S802).
In the sample inspection station M, the row bar 40 mounted on the rest 114 is imaged with the camera 103 of the inspection unit 100 of the thermal assist type magnetic head to obtain the position information of the row bar 40, and the piezo driver 107 is controlled by the control unit 30 based on this obtained position information to drive the X stage 106 or the Y stage 105, whereby alignment for adjusting the position of the row bar 40 is performed (S803), and the row bar 40 is moved to a measurement position to position the thermal assist type magnetic head element portion 501 to be measured (S804).
Next, by controlling a piezo element (not shown) which drives the Z stage 104 by the piezo driver 107 controlled by the control unit 30, the cantilever 10 is approached to a position for inspecting the inspection region 401 of the recording surface 510 of the thermal assist type magnetic head element portion 501 in the MFM mode (S805), and the inspection as described in above is executed (S806). After the inspection is completed, the drive unit 141 of the probe unit 140 is operated to retreat the probe 141, and the cantilever 10 is elevated by the Z stage 104. Next, whether or not there is any head to be inspected is determined (S807), and when there is any, the Y stage is driven to move the next head to a measurement position (S808), and the step S805 and step S806 are performed.
In contrast, when it is judged that there is no head which to be inspected next in S807, the inspection stage 101 moves along the guide rail 150, and the inspection unit 100 moves to the sample delivery station H (S809), and the row bar which has been inspected is contained in either the non-defective product collection tray 332 or the defective product collecting tray 333 depending on the results of the inspection with the handling robot 310 (S810). Next, a signal process control unit 400 determines whether or not uninspected row bar 40 is present in the supply tray 331 (S811), and when uninspected row bar 40 is present in the supply tray 331 (in the case of NO in S811), the steps from S801 are repeated. In contrast, when uninspected row bar 40 is not present in the supply tray 331 (in the case of YES in S811), the inspection is terminated (S812).
The row bar which has finished undergoing the measurement and is contained in the non-defective product collection tray 332 and judged to be a non-defective product is transferred to the next step in the magnetic head production and is processed. In contrast, the row bar 1 judged as defective and contained in the defective product collecting tray 333 is either not transferred to the next step and wasted, or is transferred to a defectiveness analysis step for investigation causes of defects.
Next, the detailed steps of the inspection step S806 will be described using
First, in performing the inspection step S806, as explained above, an image taken with the CCD camera 525 of the near-field-light detection optical system 115 displayed on the monitor screen 31 is monitored. At the same time, the positions of the probe 4 during the inspection in the AFM mode, the pinhole 521 of the mirror with a pin hole 522, and the light detector 523 are adjusted in advance.
The near-field-light detection optical system 115 is adjusted in such a manner. In this state, in S805, the cantilever 10 approaches the position for inspection in the MFM mode to the inspecting region 401 of the recording surface 510 of the thermal assist type magnetic head element portion 501. In this state, the drive unit 143 of the probe unit 140 is operated to advance the probe 141. The tip portions 1411 and 1412 of the probe 141 are brought into contact with the magnetic-head-element electrodes 41 and 42 of the thermal assist type magnetic head element portion 501 formed on the row bar 40 (S901). The signal 301 is provided to the thermal assist type magnetic head element portion 501, and the write magnetic field (alternating current magnetic field) 503 is generated from the magnetic field generating part 502 (S902).
Next, a piezo-electric element (not shown) is driven by the piezo driver 107, while vibrating the cantilever 10 by the vibrator 122. The inspection region 401 is scanned with the cantilever 10 in the MFM mode, while moving the X stage 106 in the X direction at a constant speed (S903). When the probe 4 of the cantilever 10 reaches the end in the X direction of the inspecting region 401, driving of the X stage 106 is stopped (S904). Next, the Z stage is driven to adjust the position of the cantilever 10 so that the interval between the recording surface 510 of the thermal assist type magnetic head element portion 501 and the probe 4 is an interval employed during the AFM mode (S905). The pulse drive current or pulse drive voltage 5311 is applied to the near-field-light generating part 504 from the probe unit 140, and a near-field light is generated in the vicinity of the near-field-light generating part 504 inside the inspection region 401 (S906).
Next, while vibrating the cantilever 10 by the vibrator 122, a piezo-electric element (not shown) is driven by the piezo driver 107, and to move the X stage 106 in the −X direction at a constant speed. Simultaneously, the inspecting region 401 is scanned with the cantilever 10 in the AMF mode (S907). When the probe 4 of the cantilever 10 reaches the end of the side opposite to the X direction of the inspecting region 401, driving of X stage 106 is stopped (S908).
Next, whether or not the entire surface of the inspecting region 402 is inspected (S909) is checked, and in the case where the entire inspection has not been inspected (in the case of NO in S909), a piezo-electric element (not shown) is driven by the piezo driver 107 to move the Y stage 105 in the Y direction by a pitch (S910), and the steps from S901 to S909 are performed.
When the inspection of the entire surface is completed (YES in S909), the process proceeds to S807.
By executing the process from the step S901 to S909, the distribution of the write magnetic field 503 generated from the magnetic field generating part 502 of the thermal assist type magnetic head element portion 501 and the shape of the generation region of the near-field light 505 generated from the near-field light emitting part 504 can be detected only by scanning the inspection region 401 with the probe 4 once. By processing this detected signal by the control PC 536, the position information of the near-field light emitting part 504 and the distribution information of the magnetic field generated by the magnetic field generating part 502, and the position information of the near-field light emitting part 502 from the intensity distribution of the light assisted light (near-field light) 505, and the information on the shape of the surface of the inspecting region 401 can be obtained. Furthermore, the spatial relationship between the magnetic generating part 502 and the near-field light emitting part 504 from the position information of the magnetic field generating part 502 and the position information of the near-field light emitting part 504 can be determined. This allows checking whether the magnetic field generating part 502 and the near-field light emitting part 504 are formed at a predetermined interval.
According to this embodiment, the write magnetic field (alternating current magnetic field) generated from the thermal assist type magnetic head element 501 formed on the row bar 40 by the inspection unit 100 of the thermal assist type magnetic head and the heat assist light (near-field light) can be detected only by scanning the entire surface of inspection region once with the cantilever 10, and inspection can be performed upstream of the manufacturing process and relatively in a short period of time.
It should be noted that in the above-mentioned example, the case where the thermal assist type magnetic head element 501 formed on the row bar 40 is inspected, but inspection can be similarly performed even in the state of the head assembly in which the thermal assist type magnetic head element 501 is attached to the gimbal, which is not shown. In this case the shape of the rest 114 may be changed into one that is suitable for mounting the head assembly.
Moreover, according to this Example, since the detection position by the light detector through a pinhole can be checked by the image displayed on the monitor screen, adjustment of the position of the probe and the pinhole are facilitated, which can greatly shorten the time for positioning than in the case where no monitor image is used. Moreover, the detection position is indicated and adjusted on the monitor screen, whereby sufficiently high accuracy of positioning can be ensured.
Next, another embodiment different from that mentioned above will be described. This embodiment is different from the embodiment described above in the following respect: in the embodiment described above, as shown in
When the cantilever is caused to vibrate in the up and down direction and move over the Y stage 105 in the inspection region 401, when the probe 4 is caused to scan in the Y direction from top to bottom of the figure along the dotted line 602 (the heat assist type head element 501 is moved downwardly in the vertical direction in
In contrast, when the Y stage 105 is scanned (the heat assist type head element 501 is moved upward in the vertical direction in
Thus, during the inspection, switching between the MFM mode inspection and the AFM mode inspection depending on the direction of scanning in the Y direction of the thermal assist type magnetic head element portion 501 relative to the cantilever 10 and stopping the application of the pulse drive current or pulse drive voltage 5311 to the near-field light emitting part 504 while inspecting in the MFM mode allows suppressing a rise in the temperature of the thermal assist type magnetic head element portion 501 by the heat generation from the near-field light emitting part 504, and avoiding the occurrence of damage in the thermal assist type magnetic head element portion 501.
In this MFM mode and the AFM mode, the height of the probe 4 of the cantilever 10 is switched relative to the surface of the inspection region 401 of the thermal assist type magnetic head element portion 501. That is, when inspection is performed on the AFM mode, the height of the probe 4 of the cantilever 10 relative to the surface of the inspection region 401 of the thermal assist type magnetic head element portion 501 is set to a height corresponding to the head floating height Hf for writing in a magnetic disk. While on the other hand, in the case of the MFM mode, the height of the probe 4 is set to be greater than Hf (the gap between the surface of the inspection region 401 and the tip portion of the probe 4 is greater than Hf). This switching of height is performed by driving the Z stage 104 by the piezo driver 107.
It should be noted that in the examples shown in
Moreover, in the laser driver 531, not a pulse drive current or pulse drive voltage but a constant current or voltage may be applied to generate the near-field light 505 from the near-field light generating part 504 of the thermal assist type magnetic head element portion 501.
Although the invention made by the inventors of the present invention above has been described with reference to Examples, the present invention is not limited to the above Examples, and various modifications may be made unless a gist of the present invention is deviated. The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-216338 | Sep 2012 | JP | national |
