JP2017059279A - Magnetic head inspection device and magnetic head inspection method - Google Patents

Abstract

[PROBLEMS] To correct the response characteristics of a cantilever without lowering the sensitivity of the cantilever, and even if the write track width of the magnetic head is further miniaturized, the effective speed of the magnetic head is reduced without reducing the scanning speed and increasing the tact time. Measure the track width. An excitation signal is supplied to a magnetic head, and a cantilever having a magnetic probe formed at a tip portion is scanned and moved relative to the surface of the magnetic head while vibrating at a predetermined frequency. The displacement is detected and a detection signal is output. The control unit 30 that detects the effective track width of the magnetic head from the detection signal indicates the response characteristic of the cantilever 7 and the step response of the transfer circuit whose transfer function G (s) is G (s) = 1 / (s × ｓc + 1). There are correction means (35a, 35b) that perform correction processing that approximates the characteristics and cancels the step response characteristics of the transmission circuit with respect to the detection signal. [Selection] Figure 3

Description

  The present invention relates to a magnetic head inspection apparatus and a magnetic head inspection method for inspecting a write track width of a magnetic head.

  In recent years, with the rapid increase in surface recording density of hard disk drives (HDDs), the write track width of the magnetic head is also miniaturized, and the write track width written on the magnetic disk by the magnetic head recording head is accurately inspected. The importance of technology is increasing.

  Conventionally, in the head gimbal assembly state (HGA state) where the magnetic head and suspension are integrated (HGA state) or the pseudo HGA state, the write track width is inspected by using a head disk measuring device called a spin stand. Was. However, the inspection using the spinstand is not the final stage of the magnetic head manufacturing process in the HGA state or the pseudo HGA state, so the write track width cannot be inspected. From the viewpoint of carrying out the process, it was not so preferable.

  On the other hand, in the magnetic head inspection method and the magnetic head inspection apparatus described in Patent Document 1, the magnetic head is generated by the recording head portion of the magnetic head in a state where an excitation signal (recording signal) is supplied to the magnetic head in the row bar state. The effective track width of the magnetic head is inspected by directly measuring the state of the magnetic field with a magnetic force microscope (MFM) at a position that is separated by the flying height equivalent of the magnetic head. .

JP 2009-230845 A

  When the write track width of the magnetic head is inspected with a magnetic force microscope (MFM), the cantilever with the magnetic probe formed at the tip is scanned and moved relative to the surface of the magnetic head in order to shorten the inspection time (tact time). The scanning speed at the time of making it becomes an important factor. As the surface recording density of a hard disk drive (HDD) further increases, if the write track width of the magnetic head is further reduced, it is necessary to increase the response speed of the cantilever in order to perform inspection while maintaining the scan speed. As a method for improving the response speed of the cantilever, it is conceivable to reduce the Q value which is the response characteristic of the cantilever. However, if the Q value is reduced, the sensitivity of the cantilever is lowered, and a minute magnetic field may not be detected. . For this reason, conventionally, in order to cope with further miniaturization of the write track width of the magnetic head, there has been a problem that the scan speed has to be slowed, and as a result, the tact time becomes long.

  The object of the present invention is to correct the response characteristics of the cantilever without lowering the sensitivity of the cantilever, and even if the write track width of the magnetic head is further reduced, the magnetic speed can be reduced without reducing the scan speed and increasing the tact time. It is to measure the effective track width of the head.

In the magnetic head inspection apparatus of the present invention, a magnetic probe is formed at the tip, and a cantilever that vibrates at a predetermined frequency, and the cantilever, the magnetic probe of the magnetic head is equivalent to the flying height of the magnetic head relative to the magnetic disk. An inspection stage that scans and moves relative to the surface of the magnetic head in a state separated from the surface, a detection unit that detects the displacement of the cantilever and outputs a detection signal, an excitation signal is supplied to the magnetic head, and the detection unit And a control unit for detecting the effective track width of the magnetic head from the detection signal, the control unit shows the response characteristic of the cantilever, and the transfer function G (s) is G (s) = 1 / (s × Τc + 1)
The correction means approximates the step response characteristic of the transfer circuit and corrects the detection signal of the detection unit to cancel the step response characteristic of the transfer circuit.

In the magnetic head inspection method of the present invention, an excitation signal is supplied to the magnetic head, and the magnetic probe is oscillated at a predetermined frequency while the cantilever having the magnetic probe formed at the tip is vibrated at a predetermined frequency. While moving away from the surface of the magnetic head by an amount equivalent to the flying height relative to the disk, scan movement is performed on the surface of the magnetic head, displacement of the cantilever is detected, a detection signal is output, and the response characteristics of the cantilever are transmitted. The function G (s) is G (s) = 1 / (s × Τc + 1)
Approximate the step response characteristics of the transfer circuit, and correct the detection signal to cancel the step response characteristics of the transfer circuit, and detect the effective track width of the magnetic head from the detected detection signal. It is.

  As a result of analysis by simulation, the inventors have found that the rise path of the amplitude signal of the cantilever when the oscillation signal for vibrating the cantilever is turned on is very similar to the waveform of the step response of the low-pass filter in the electric circuit. I discovered that. Based on this discovery, in the present invention, the response characteristic of the cantilever is approximated as the step response characteristic of the transfer circuit having the same transfer function G (s) as the transfer function of the low-pass filter, and this transfer is made to the detection signal. Correction processing for canceling the step response characteristic of the circuit is performed. As a result, the waveform of the detection signal is improved, and the effective track width of the magnetic head can be measured without reducing the scan speed and increasing the tact time even if the write track width of the magnetic head is further reduced. It becomes.

  Furthermore, the magnetic head inspection apparatus and magnetic head inspection method according to the present invention provides a response characteristic of a cantilever with a low-pass filter having a cut-off frequency that is half the frequency width when the amplitude is attenuated by 3 dB from the maximum value in the resonance characteristic of the cantilever. It approximates as step response characteristics. From the above findings, the step response characteristic of the low-pass filter is directly applied to the response characteristic of the cantilever, and the time constant Τc of the transfer function G (s) of the transfer circuit is easily determined.

  Alternatively, according to the magnetic head inspection apparatus and magnetic head inspection method of the present invention, the time constant Τc of the transfer function G (s) of the transfer circuit and the detection signal transient when the oscillation signal for vibrating the cantilever is turned on. From the characteristics, it is obtained by the fitting process. As a result, a more accurate approximation is possible than in the case described above.

  As a correction means, a transmission circuit is provided by hardware processing on a detection signal using an infinite impulse response (IIR) filter having an infinite impulse response duration and a feedback configuration in which an output is fed back to an input. Correction processing for canceling the step response characteristic may be performed. Alternatively, as a correction unit, a digital signal processing circuit that performs arithmetic processing on a signal obtained by digitizing the detection signal may be used to perform correction processing that cancels the response characteristic of the transmission circuit by software processing.

  According to the present invention, since the response characteristic of the cantilever can be corrected without lowering the sensitivity of the cantilever, even if the write track width of the magnetic head is further reduced, the scanning speed is lowered and the tact time is lengthened. Therefore, the effective track width of the magnetic head can be measured.

  Further, by approximating the response characteristic of the cantilever as a step response characteristic of a low-pass filter having a half-value of the frequency width when the amplitude is attenuated by 3 dB from the maximum value in the resonance characteristic of the cantilever, the transfer function of the transfer circuit is obtained. The time constant Τc of G (s) can be easily determined.

  Alternatively, a more accurate approximation can be obtained by obtaining the time constant Τc of the transfer function G (s) of the transfer circuit from the transient characteristics of the detection signal when the oscillation signal for vibrating the cantilever is turned on by fitting processing. Thus, the response characteristic of the cantilever can be corrected with higher accuracy.

1 is a diagram showing a schematic configuration of a magnetic head inspection apparatus according to an embodiment of the present invention. 2A is a front side view of a part of the row bar, FIG. 2B is a top view of a part of the row bar, and FIG. 2C is a view showing a state where the probe card is connected. It is a block diagram of the control part by one embodiment of the present invention. It is a block diagram of the control part by other embodiment of this invention. It is a figure explaining the change of the resonance characteristic of a cantilever by the presence or absence of a magnetic field. It is a figure which shows the relationship between the strength of a magnetic field, and a phase difference signal. It is a figure which shows the transient characteristic of an amplitude signal when the oscillation signal for vibrating a cantilever is turned on. It is a figure which shows the resonance characteristic of a cantilever. It is a figure which shows the frequency characteristic of a low-pass filter.

  FIG. 1 is a diagram showing a schematic configuration of a magnetic head inspection apparatus according to an embodiment of the present invention. The magnetic head inspection apparatus according to the present embodiment measures the effective track width of the magnetic head in the state of the row bar (block in which the slider is arranged) before cutting out the single slider (chip). The magnetic head inspection apparatus 100 includes a cantilever 7, an inspection stage 10, a mounting unit 121, a piezo driver 20, a control unit 30, a displacement detection unit 40, a differential amplifier 50, a DC converter 60, a feedback controller 70, and an oscillator 80. It consists of

  Usually, the row bar 1 is cut out from a wafer as an elongated block of about 3 cm to 5 cm, and about 40 to 60 sliders are arranged. The magnetic head inspection apparatus 100 according to the present embodiment is configured to perform a predetermined inspection using the row bar 1 as a workpiece. Usually, about 30 to 30 row bars 1 are stored in a tray (not shown) at a predetermined interval in the minor axis direction. A handling robot (not shown) takes out the row bar 1 from a tray (not shown) one by one and conveys it to the inspection stage 10.

  The inspection stage 10 includes an X stage 11 that moves the row bar 1 in the X direction, a Y stage 12 that moves the row bar 1 in the Y direction, and a Z stage 13. On the upper surface of the Y stage 12, a mounting portion 121 for positioning the row bar 1 is provided. A stepped portion that substantially matches the shape of the row bar 1 is provided on the upper surface side edge of the mounting portion 121. The row bar 1 is installed at a predetermined position by being in contact with the bottom and side surfaces of the stepped portion. The side surface of the stepped portion is in contact with the rear surface of the row bar 1 (the surface opposite to the surface having the connection terminals of the magnetic head). Above the Y stage 12, a camera for measuring a positional deviation amount (not shown) is provided. When the predetermined positioning is completed, the row bar 1 is attracted to and held by the placement unit 121.

  2A is a front side view of a part of the row bar, and FIG. 2B is a top view of a part of the row bar. In FIG. 2B, a plurality of sliders 2 are arranged on the row bar 1, and a head portion 3 including a recording head and a reading head is formed on the upper surface of each slider 2 (the surface facing the magnetic disk). ing. FIG. 2A is a front side view of the row bar 1 viewed in the direction indicated by the arrow A in FIG. A plurality of connection terminals 4 connected to the recording head and the reading head of the head unit 3 are provided on the front side surface of the row bar 1 for each slider 2.

  In FIG. 2A, the head portion 3 of each slider 2 is mounted with one recording head and three sets of magnetic detection elements constituting a read head, and a total of eight connection terminals connected thereto. Shows an example provided in each slider 2. However, the number of recording heads, the number of magnetic detection elements of the read head, and the number of connection terminals 4 are not limited to this.

  By connecting the probe pin of the probe card 6 to the connection terminal 4 connected to the recording head among the connection terminals 4 of each slider 2, the recording head of the head portion 3 of each slider 2 can be inspected. Become. FIG. 2C is a diagram showing a state in which the probe card is connected. The probe card 6 has a plurality of probe pins that come into contact with the connection terminals 4 and supplies excitation signals (recording signals) from the probe pins to the coils of the recording head under the control of the control unit 30.

  In FIG. 1, a Z stage 13 moves a cantilever 7 of a magnetic force microscope (MFM) in the Z direction. The X stage 11, the Y stage 12, and the Z stage 13 of the inspection stage 10 are each constituted by a piezo stage. The piezo driver 20 drives and controls the X stage 11, the Y stage 12, and the Z stage 13 of the inspection stage 10 based on the control of the control unit 30.

  A cantilever 7 having a magnetic probe with a sharp tip as a free end is arranged at an opposing position above the row bar 1 placed on the placement unit 121. A thin film (magnetic film) made of a magnetic material is formed on the surface of the magnetic probe of the cantilever 7. The fixed end of the cantilever 7 is attached to an excitation member provided on the lower side of the Z stage 13. The excitation member is composed of a piezo element, and an AC voltage having a frequency near the mechanical resonance frequency is applied by the excitation voltage from the piezo driver 20 to vibrate the magnetic probe in the vertical direction. When the magnetic probe of the cantilever 7 receives a magnetic field from the recording head of the magnetic head, an attractive or repulsive magnetic force is generated in the magnetic probe, and the displacement amount of the cantilever 7 in the Z direction changes.

  The displacement detection unit 40 includes a semiconductor laser element 41, reflection mirrors 42 and 43, and a displacement sensor 44. The light emitted from the semiconductor laser element 41 is reflected by the reflection mirror 42 and irradiated onto the cantilever 7. The reflected light reflected by the cantilever 7 is further reflected by the reflecting mirror 43 and irradiated to the displacement sensor 44. The displacement sensor 44 is composed of a two-divided photodetector element, and outputs two signals corresponding to the intensity of light received by each photodetector element.

  The differential amplifier 50 performs a predetermined calculation process on the difference signal between the two signals output from the displacement sensor 44, and generates a displacement signal corresponding to the difference between the two signals output from the displacement sensor 44. And supplied to the DC converter 60. The displacement signal output from the differential amplifier 50 is a signal corresponding to the displacement of the cantilever 7 and is an AC signal because the cantilever 7 vibrates.

  The DC converter 60 includes an RMS-DC converter (Root Mean Squared to Direct Current converter), and converts the displacement signal output from the differential amplifier 50 into an effective DC signal. The displacement signal output from the DC converter 60 is supplied to the feedback controller 70. The feedback controller 70 supplies the displacement signal output from the DC converter 60 to the control unit 30 and the piezo driver 20.

  The control unit 30 is configured by a control computer having a basic configuration of a personal computer (PC) including a monitor. The control unit 30 monitors the magnitude of vibration of the cantilever 7 from the displacement signal supplied from the feedback controller 70 and sends a control signal for the Z stage 13 to the piezo driver 20. The piezo driver 20 adjusts the position of the cantilever 7 in the Z direction at the time of inspection by controlling the Z stage 13 in accordance with this control signal. In the present embodiment, the head flying height of the hard disk drive (HDD) is set as the position of the cantilever 7 in the Z direction.

  The oscillator 80 supplies an oscillation signal for vibrating the cantilever 7 to the piezo driver 20. Based on the oscillation signal from the oscillator 80, the piezo driver 20 vibrates the excitation member provided on the lower side of the Z stage 13 and vibrates the cantilever 7 at a predetermined frequency. Then, the mounting portion 121 on which the row bar 1 is mounted is moved in the X direction and the Y direction by the X stage 11 and the Y stage 12 of the inspection stage 10 so that the cantilever 7 scans with respect to the surface of the row bar 1. Then, the recording head of the magnetic head is inspected.

  At the time of inspection, the control unit 30 detects the effective track width of the magnetic head from the displacement signal supplied from the differential amplifier 50. FIG. 3 is a block diagram of a control unit according to an embodiment of the present invention. The control unit 30 of the present embodiment includes an analog-digital converter 31, a lock-in amplifier 32, an image data memory 33, a monitor 34, an infinite impulse response (IIR) filter 35a, a corrected image memory 36, and an arithmetic circuit 37. It is configured.

  The analog-digital converter 31 converts the analog displacement signal output from the differential amplifier 50 into a digital signal. The lock-in amplifier 32 converts the displacement signal converted into a digital signal into an amplitude signal indicating the amplitude of vibration of the cantilever 7 and a phase difference signal indicating the phase difference of vibration of the cantilever 7 and outputs the converted signal. The image data memory 33 samples and stores the amplitude signal and phase difference signal output from the lock-in amplifier 32 as image data.

  The infinite impulse response (IIR) filter 35a receives the signal output from the lock-in amplifier 32 and performs a correction process described later by hardware processing. The corrected image memory 36 samples and stores the signal corrected by the infinite impulse response (IIR) filter 35a as image data. The arithmetic circuit 37 calculates the effective track width of the magnetic head from the image data stored in the corrected image memory 36. The monitor 34 displays the image data stored in the image data memory 33, the image data stored in the corrected image memory 36, and the calculation result of the calculation circuit 37.

  FIG. 4 is a block diagram of a control unit according to another embodiment of the present invention. The control unit 30 of the present embodiment includes a digital signal processing circuit 35b instead of the infinite impulse response (IIR) filter 35a shown in FIG. Other components are the same as those of the embodiment shown in FIG. The digital signal processing circuit 35b performs arithmetic processing on the image data stored in the image data memory 33, and performs correction processing described later by software processing.

  FIG. 5 is a diagram for explaining changes in the resonance characteristics of the cantilever depending on the presence or absence of a magnetic field. FIG. 5A shows the relationship between the frequency and amplitude of vibration of the cantilever 7. When there is no magnetic field having a strength that affects the vibration of the cantilever 7, it is assumed that the cantilever 7 has a resonance characteristic that maximizes the amplitude at the frequency f0, as in the waveform B indicated by the solid line. The cantilever 7 is vibrated at a frequency f0 at which the amplitude is maximum. When the cantilever 7 is moved to a region where a magnetic field having a strength that affects the vibration of the cantilever 7 is generated, the resonance characteristic of the cantilever 7 is affected by the magnetic field and changes to, for example, a waveform C indicated by a broken line. . Therefore, the resonance characteristic of the cantilever 7 is such that the frequency at which the amplitude is maximum deviates from f0, and the amplitude is attenuated at the frequency f0 at which the cantilever 7 is vibrated.

  FIG. 5B shows the relationship between the frequency and phase of the cantilever vibration. When there is no magnetic field having a strength that affects the vibration of the cantilever 7, it is assumed that the cantilever 7 has a phase characteristic of a waveform D indicated by a solid line. When the cantilever 7 is moved to a region where a magnetic field having a strength that affects the vibration of the cantilever 7 is generated, the phase characteristic of the cantilever 7 is affected by the magnetic field and changes, for example, to a waveform E indicated by a broken line. To do. Accordingly, at the frequency f0 at which the cantilever 7 is vibrated, the phase is shifted and a phase difference is generated depending on the presence or absence of a magnetic field.

  FIG. 6 is a diagram showing the relationship between the magnetic field strength and the phase difference signal. 6A shows the phase difference signal when the magnetic probe of the cantilever 7 moves in the region where the magnetic field shown in FIG. 6B is generated by the recording head of the magnetic head, and the horizontal axis indicates time. Replaced and shown. In FIG. 6A, the phase difference signal ideally changes like a waveform F indicated by a solid line. However, when the response speed of the cantilever 7 is slow, the phase difference signal changes like a waveform G indicated by a broken line, for example. In the present embodiment, correction processing is performed to approximate the waveform of the phase difference signal from the waveform G to the waveform F.

  FIG. 7 is a diagram showing the transient characteristics of the amplitude signal when the oscillation signal for vibrating the cantilever is turned on. FIG. 7A shows an oscillation signal for oscillating the cantilever, and FIG. 7B shows on / off of the oscillation signal as a step signal. FIG. 7C shows changes in the amplitude signal at this time, and FIG. 7D shows a rising locus indicated by a broken line in FIG. 7C.

As a result of analysis by simulation, the inventor has found that the rising trajectory of the amplitude signal of the cantilever shown in FIG. 7D is very similar to the waveform of the step response of the low-pass filter in the electric circuit. Based on this discovery, the response characteristic of the cantilever 7 is the same as the transfer function of the low-pass filter.
G (s) = 1 / (s × Τc + 1)
Is approximated as a step response characteristic of the transfer circuit. And the correction process which cancels the step response characteristic of this transmission circuit is performed with respect to the detected signal. Once the transfer function of the transfer circuit is determined, the design of a filter that cancels the step response characteristic of the transfer circuit and the arithmetic processing that cancels the step response characteristic of the transfer circuit can be easily performed using conventional techniques. .

  An example in which the step response characteristic of the low-pass filter is applied as it is as the response characteristic of the cantilever 7 will be described. FIG. 8 is a diagram showing the resonance characteristics of the cantilever. In the resonance characteristics of the cantilever 7, the frequency width when the amplitude is attenuated by 3 dB with respect to the maximum amplitude when the frequency is f0 is fw.

  FIG. 9 is a diagram illustrating frequency characteristics of the low-pass filter. In the frequency characteristics of the low-pass filter shown in FIG. 9A, the frequency fc when the amplitude is attenuated by 3 dB is the cutoff frequency. In the present embodiment, the response characteristic of the cantilever 7 is defined as a cut-off frequency fc (half value of the frequency width fw when the amplitude is attenuated by 3 dB from the maximum value in the resonance characteristic of the cantilever 7) (fc = fw / 2). Approximate the step response characteristics of the filter. This means that in the above transfer function G (s), the time constant Τc is set to Τc = 1 / (π × fw).

The infinite impulse response (IIR) filter 35a in FIG. 3 and the digital signal processing circuit 35b in FIG. 4 perform a correction process that cancels the step response characteristic of the low-pass filter. At the same time, the infinite impulse response (IIR) filter 35a and the digital signal processing circuit 35b have the frequency characteristics of the waveform H indicated by the broken line in the frequency band of the signal detected by the cutoff frequency fh in FIG. 9B. A process of applying a response of the low-pass filter is performed. The transfer function Gh (s) as the transfer circuit of the infinite impulse response (IIR) filter 35a and the digital signal processing circuit 35b is
Gh (s) = (s × Τc + 1) / {s / (2π × fh) +1}
It becomes.

  The time constant Τc of the transfer function G (s) can also be obtained by fitting processing from the transient characteristics of the amplitude signal when the oscillation signal for vibrating the cantilever 7 is turned on. A time constant Τc in which the above transfer function G (s) is most suitable for the rising locus of the amplitude signal shown in FIG. This allows a more accurate approximation.

  According to the embodiment described above, the response characteristic of the cantilever 7 can be corrected without lowering the sensitivity of the cantilever 7. Therefore, even if the write track width of the magnetic head is further reduced, the scan speed is reduced. The effective track width of the magnetic head can be measured without increasing the tact time.

  Further, by approximating the response characteristic of the cantilever 7 as a step response characteristic of a low-pass filter in which the half value of the frequency width fw when the amplitude is attenuated by 3 dB from the maximum value in the resonance characteristic of the cantilever 7 is cut off, The time constant Τc of the circuit transfer function G (s) can be easily determined.

  Alternatively, the time constant Τc of the transfer function G (s) of the transfer circuit is obtained by fitting processing from the transient characteristics of the amplitude signal when the oscillation signal for vibrating the cantilever 7 is turned on. Approximation is possible, and the response characteristic of the cantilever 7 can be corrected with higher accuracy.

  In the above-described embodiment, when the cantilever is scanned and moved with respect to the surface of the magnetic head, the magnetic head is moved in the X direction and the Y direction by the inspection stage. May be moved in the X and Y directions.

DESCRIPTION OF SYMBOLS 100 Magnetic head inspection apparatus 1 Rover 2 Slider 3 Head part 4 Connection terminal 6 Probe card 7 Cantilever 10 Inspection stage 11 X stage 12 Y stage 121 Mounting part 13 Z stage 20 Piezo driver 30 Control part 31 Analog-digital converter 32 Lock-in Amplifier 33 Image data memory 34 Monitor 35a Infinite impulse response (IIR) filter 35b Digital signal processing circuit 36 Correction image memory 37 Arithmetic circuit 40 Displacement detector 41 Semiconductor laser element 42, 43 Reflection mirror 44 Displacement sensor 50 Differential amplifier 60 DC converter 70 Feedback controller 80 Oscillator

Claims (10)

A magnetic probe is formed at the tip, and a cantilever that vibrates at a predetermined frequency;
An inspection stage that scans and moves the cantilever with respect to the surface of the magnetic head in a state where the magnetic probe is separated from the surface of the magnetic head by an amount corresponding to the flying height of the magnetic head relative to the magnetic disk;
A detector that detects the displacement of the cantilever and outputs a detection signal;
A control unit for supplying an excitation signal to the magnetic head and detecting an effective track width of the magnetic head from a detection signal of the detection unit;
The control unit has a response characteristic of the cantilever, and a transfer function G (s) is G (s) = 1 / (s × Τc + 1)
A magnetic head inspection apparatus, comprising: a correction unit that approximates the step response characteristic of the transfer circuit and corrects the detection signal of the detection unit to cancel the step response characteristic of the transfer circuit.   The correction means approximates the response characteristic of the cantilever as a step response characteristic of a low-pass filter having a cutoff frequency of half the frequency width when the amplitude is attenuated by 3 dB from the maximum value in the resonance characteristic of the cantilever. The magnetic head inspection apparatus according to claim 1.   The time constant Τc of the transfer function G (s) of the transfer circuit is obtained by fitting processing from the transient characteristics of the detection signal of the detection unit when the oscillation signal for vibrating the cantilever is turned on. 2. A magnetic head inspection apparatus according to claim 1, wherein   The said correction | amendment means is an infinite impulse response filter which has a feedback structure which feeds back an output to an input in which the duration of an impulse response is infinite. Magnetic head inspection device.   2. The digital signal processing circuit according to claim 1, wherein the correction means is a digital signal processing circuit that performs arithmetic processing for canceling a response characteristic of the transmission circuit on a signal obtained by digitizing the detection signal of the detection unit. 4. The magnetic head inspection apparatus according to any one of 3 above. Supply excitation signal to magnetic head,
While the cantilever having a magnetic probe formed at the tip portion is vibrated at a predetermined frequency, the magnetic probe is separated from the surface of the magnetic head by an amount corresponding to the flying height of the magnetic head with respect to the magnetic disk. Scanning and moving the surface of the magnetic head;
Detecting the displacement of the cantilever and outputting a detection signal;
As for the response characteristics of the cantilever, the transfer function G (s) is G (s) = 1 / (s × Τc + 1)
Is approximated as a step response characteristic of the transfer circuit, and a correction process is performed on the detection signal to cancel the step response characteristic of the transfer circuit,
A magnetic head inspection method, wherein an effective track width of the magnetic head is detected from a detection signal subjected to correction processing.   7. The response characteristic of the cantilever is approximated as a step response characteristic of a low-pass filter having a cut-off frequency at half the frequency width when the amplitude is attenuated by 3 dB from the maximum value in the resonance characteristic of the cantilever. 2. A magnetic head inspection method according to 1.   The time constant Τc of the transfer function G (s) of the transfer circuit is obtained by a fitting process from the transient characteristics of the detection signal when an oscillation signal for vibrating the cantilever is turned on. Item 7. A magnetic head inspection method according to Item 6.   7. The correction process for canceling the step response characteristic of the transfer circuit is performed using an infinite impulse response filter having a feedback structure in which the duration of the impulse response is infinite and the output is fed back to the input. The magnetic head inspection method according to claim 8.   9. The correction process for canceling the response characteristic of the transfer circuit is performed using a digital signal processing circuit that performs arithmetic processing on a signal obtained by digitizing the detection signal. The magnetic head inspection method according to one item.

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