JP3353589B2 - Magnetic head inspection method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for inspecting a magnetic head for reproducing data from a magnetic recording medium such as a magnetic disk, and more particularly to a method and an apparatus for inspecting a magnetic head using a magnetoresistive element. About.

[0002]

2. Description of the Related Art Generally, a magnetic head using a magnetoresistive element has been put to practical use as a thin film magnetic head for a magnetic recording medium such as a magnetic disk. FIG. 22 is an enlarged perspective view of a magnetic head using a magnetoresistive element, and FIG.
3 is an enlarged perspective view of the magnetoresistive element of the magnetic head as viewed from the magnetic medium side, and FIG. 24 is a perspective view showing a block body of the magnetic head shown in FIG. The magnetic head 2 includes a slider portion 4 and a thin film laminated portion 6, and a magnetoresistive element 8 made of, for example, permalloy is embedded in a part of the thin film laminated portion 6 by a film forming process. The magnetic head 2 is formed by, for example, selectively forming a plurality of thin films as described above on the surface of an AlTiC substrate, and cutting the individual thin films into a large number at a time. Therefore, the slider portion 4 is originally a substrate portion, and the length direction of the slider portion 4 is the thickness direction of the substrate. This slider part 4
On both sides of the medium sliding surface, two rails 10 are formed, and this surface is used as a wrap surface. Specifically, as shown in FIG. 23, the magnetoresistive element 8 has both ends connected to electrode films 62, 62 as lower electrodes, and an upper magnetic pole 91 above the mid-shield 90. A coil 92 is arranged. A lower shield 94 is provided below the magnetoresistive effect element 8, and constitutes a head as a whole.

[0003] Such a magnetoresistive element 8 is provided at an end of one of the rails, and reads a magnetic field of a track while this part is slightly floated from a magnetic recording medium (not shown). Therefore, the length L1 of the magnetoresistive effect element 8 is set to a length substantially equal to the track width. This type of magnetoresistive effect element can obtain a large reproduction output because it utilizes the magnetoresistance effect of a ferromagnetic thin film such as permalloy as described above, but it is caused by a defect in the film formation process and the like. Noise, such as Barkhausen noise, the magnetoresistance change rate is not appropriate, the operating point is asymmetric, or the output amplitude varies every time a record is written and read, and the reproducibility of the operation is sufficient. It is inevitable that a defective product such as a defective product is generated. Since such a defective product cannot be expected to perform a normal reproducing operation, it is necessary to perform an inspection including the occurrence of noise at the time of manufacturing the head.

As an inspection method, a magnetic head laminated and formed on a wafer substrate is cut out from the substrate to complete it as a single unit, and then attached to a support spring and actually run on the surface of the magnetic disk to output an output waveform from the head. Was measured to check for the presence of noise, for example. However, in this inspection method, since the heads are individually cut out, fixed to the support springs, and measured while repeating attachment and detachment one by one, it takes much time and labor.

Therefore, an inspection method as disclosed in JP-A-6-150264 has been proposed for the purpose of greatly reducing the inspection time and labor. In this method, as shown in FIG. 24, a head block 12 in which a number of magnetic heads are connected in a horizontal line is cut out from a wafer, and in this state, a sliding surface (air) is formed by a Helmholtz coil arranged so as to surround the entire block. The quality of the product is determined by applying a sinusoidal magnetic field perpendicular to the bearing surface) and detecting a change in resistance of the magnetoresistive element 8 at this time.

[0006]

However, in such a measuring method in which a magnetic field is applied only in one direction, the rate of change in resistance, operating point, Barkhausen noise, etc. of a magnetoresistive element can be measured to some extent. Although possible, the test results may be insufficient, and the reproducibility of the operation during reproduction cannot be measured. Also,
Since the Helmholtz coil for applying a one-way magnetic field to the head block is configured to surround the entire head block, which is the object to be inspected, the entire device becomes very large, resulting in high cost. The present invention has been devised in view of the above problems and effectively solving them. An object of the present invention is to provide a method and an apparatus for inspecting a magnetic head, which can easily determine the quality of a magnetoresistive element with a simple configuration.

[0007]

The inventor of the present invention has conducted intensive studies on a method of inspecting a magnetic head, and found that a magnetic field in a direction different from a signal magnetic field component of a magnetic recording medium, that is, a magnetic field in a track width direction is a magnetoresistive element. The present invention has been achieved by obtaining the finding that the head having poorer characteristics has a greater fluctuation or deviation in resistance as a result of measurement. According to a first method of the present invention, in a method of inspecting a magnetic head using a magnetoresistive element, a step of applying a rotating magnetic field so as to be parallel to a surface of the magnetoresistive element while applying a predetermined bias current to the magnetoresistive element. When the steps of detecting a change in resistance of the magnetoresistive element during application of the rotating magnetic field, and a determination step of determining acceptability based on the detected the change in resistance, the determining step
Is the basic characteristic line determined by each detection resistance value.
The standard deviation of the detection resistance value and the maximum change amount of the detection resistance value
The determination is made based on the ratio .

A second method invention is a method for inspecting a magnetic head using a magnetoresistive element, wherein a first bias current is applied to a first direction in one direction so as to be parallel to a surface of each magnetoresistive element while flowing a predetermined bias current. A first detection step of detecting a change in the resistance value of the magnetoresistive element by applying the magnetic field while changing the magnetic field, a step of obtaining an approximate characteristic line based on the obtained resistance value, While applying a constant second magnetic field in a direction different from the first magnetic field in a direction different from the first magnetic field while flowing the first magnetic field while changing the first magnetic field, A second detecting step of detecting a change in the resistance value, a step of obtaining a deviation between the resistance value of the second detecting step and the approximate characteristic line, and a step of determining the deviation and the resistance change amount in the first detecting step. Based on the magnetic It is obtained by constituting the quality of resistive element to comprise a determination step.

According to a third aspect of the present invention, there is provided a method of inspecting a magnetic head using a magnetoresistive element, wherein a predetermined bias current is applied to the magnetic head in two different directions so as to be parallel on the surface of the magnetoresistive element. While applying a first magnetic field and a second magnetic field, and changing the magnitude of the first magnetic field by a predetermined amount, at each change point, the second magnetic field is changed to a different value including zero, and A measuring step of measuring a resistance value of the magnetoresistive element, a step of determining a swing of the measured resistance value when the second magnetic field is applied, and a resistance change amount caused by a change of the first magnetic field. And a determination step of determining the quality of the magnetoresistive element based on the maximum swing width among the swing widths.

The device invention implements the above-described first to third method inventions. That is, in a magnetic head inspection device using a magnetoresistive element, an electric pad is provided on each pad of the magnetoresistive element. Probe means made to be able to contact each other, magnetic field applying means for applying a first magnetic field and a second magnetic field in at least two different directions parallel to the plane of the magnetoresistive element, and applying the magnetic field Resistance detecting means for detecting the resistance value of the magnetoresistive effect element, and determining means for determining the acceptability based on the detected resistance value, the determining means, the detected resistance value
A characteristic line calculation unit for obtaining a characteristic line based on the characteristic line;
Deviation calculation for finding a standard deviation from each of the detected resistance values
, The sum of the deviations and the resistance value of the magnetoresistive element
And a comparison unit for calculating a ratio of the change amount to the discrimination value.
And a judgment unit for judging whether or not the number has reached .

According to the first method of the present invention, a predetermined magnetic field is applied one turn so as to be parallel to this surface in a state where a bias current is applied to the magnetoresistive element, and the resistance of the magnetoresistive element is rotated during the rotation. Detect changes. That is, in the case of a defective product, the state of the resistance change is considerably disturbed. In this case, the determination method determines the basic characteristic curve determined by the test <br/> out resistance values, a standard deviation of each detection resistance value for the characteristic line of the maximum change in this value and the detected resistance value The ratio is determined, and pass / fail is determined based on the value of the ratio. The second method invention obtains a deviation between the approximate characteristic line obtained from the measurement result in the first detection step and the measured resistance value obtained in the second detection step, and determines the quality of the element based on the deviation. judge.

According to the third aspect of the invention, the maximum swing width when applying and measuring the second magnetic field is determined from the measured value obtained in the measuring step, and the maximum swing width and the first magnetic field are compared with each other. The ratio with the amount of resistance change due to the change is determined, and the quality of the element is determined based on this value. In this case, for example, the first and second
Are parallel to the plane of the magnetoresistive element and orthogonal to each other. The first magnetic field is, for example, perpendicular to the medium facing surface and in the same direction as the signal component of the magnetic recording medium. At this time, the resistance of the element is measured when the second magnetic field is zero and when the absolute value is the same and the direction is set to the opposite direction.

The apparatus invention implements each of the above method inventions. The method of applying a magnetic field by the magnetic field applying means is such that when a rotating magnetic field is generated and applied in accordance with each of the above methods, one magnetic field is applied. When the other magnetic field is changed to a predetermined value of zero or plus or minus while sweeping, one magnetic field may be swept while the other magnetic field is fixed to zero or a predetermined value. Each of the obtained measurement values is processed by the procedure according to each method invention described above.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic head inspection method and apparatus according to the present invention will be described below. FIG. 1 is a block diagram showing a magnetic head inspection apparatus according to the present invention, and FIG.
3 is a plan view of the magnetic field applying means, FIG. 3 is a sectional view showing the magnetic field applying means, FIG. 4 is a perspective view showing the inside of the magnetic field applying means, FIG. 5 is a diagram showing a circuit configuration of the inspection apparatus, and FIG. FIG. 7 is an enlarged view showing the magnetoresistance effect element.
FIG. 3 is a sectional view taken along line AA in FIG.

First, an overall configuration of a magnetic head inspection apparatus will be described with reference to FIG. As shown in the drawing, the inspection apparatus 14 for a magnetic head holds a substrate W, and
Stage 16 that can be moved with high precision in the Z and θ directions
The movement of the stage 16 in the above four directions is controlled by the stage controller 18. Here, X and Y indicate plane directions, Z indicates a direction perpendicular to the plane, and θ indicates a rotation direction of the Z axis. A large number of magnetoresistive elements (hereinafter referred to as MR elements) are laminated on the substrate W by a thin film forming technique, and are cut out to form a magnetic head or head block as shown in FIG. 22 or FIG. Is formed. Here, the inspection of the MR element is performed in the state of the substrate before cutting.

At a position slightly distant from the upper surface of the stage 16, a probe card 20 as probe means is fixedly provided independently of the stage 16, and the center of the card 20 is directed obliquely downward. Thus, a plurality of probe needles 22 are provided. The probe needle 22 is electrically connected to a pad (not shown) of each MR element so that a bias current or the like can flow. Above and below the center of the probe card 20, magnetic field applying means 24, 24, which are features of the present invention, are provided with a substrate W interposed therebetween. A magnetic field of an arbitrary magnitude can be applied in an arbitrary direction. At the center of the probe card 20, a viewing hole 26 is formed.
Is arranged so that the contact state of the probe needle 22 can be monitored by the monitor 32.

The probe card 20 is connected to a bias current source 34 for supplying a predetermined bias current to the MR element via a probe needle 22 and detects a voltage applied between the MR elements. A resistance detecting means 36 for detecting a resistance value of the lever, for example, a digital voltmeter or the like is connected. The control computer 38
At the same time as controlling the operation of the entire device, a function as a judging means for judging the quality of the MR element by performing a predetermined process, which will be described later, by software on the detected resistance value obtained by the resistance detecting means 36. Have. Also, from this computer 38, two D / A converters 40A,
40B and two amplifiers 42A. A current for generating a magnetic field is caused to flow through the two magnetic field applying means 24 via 42B. In this case, two D / A converters 40
A and 40B are both connected to both magnetic field applying means 24, 24, and one D / A converter 40A is connected to the first
And the other D / A converter 40B
Are used for generating a second magnetic field.

The magnetic field applying means 24 will now be described with reference to FIGS. As shown in FIG. 1, the two magnetic field applying means 24, 24 arranged above and below the substrate W are arranged in exactly the same manner so as to face each other. 24 will be described. The magnetic field applying means 24 has four leg cores 44 made of, for example, ferrite arranged in a cross shape.
Each leg core has an electromagnetic coil 46A, 46A, 46B, 46
B is provided, and the opposed coils 46A, 46A or 46B, 46B form an electromagnetic coil pair. The lower end of each leg core 44 is bent inward in an L-shape, and the distance L2 between the distal ends is set to, for example, about 10 mm. The upper ends of the leg cores are joined by a quadrangular ring-shaped connecting yoke 48, for example, also made of ferrite, and form a magnetic path connecting the yokes.
The shape of the connecting yoke 48 is not limited to a quadrangle, and may be, for example, a circular ring shape. In any case, the visual field of the microscope is not obstructed. When a microscope is not provided, the shape of the connecting yoke does not need to be ring-shaped, and it is a matter of course that there is no problem with a circular flat plate.

Further, a protective cover 50 made of, for example, aluminum is provided so as to cover the upper and side portions of the core 44 and the yoke 48, and an observing hole 52 is provided at the center of the protective cover 50 so that the visual field of the microscope can be improved. It does not hinder. FIG. 4 is a perspective view with the protective cover 50 removed. Here, the electromagnetic coil pairs 46A, 46A and 46B, 46B are connected in series, and are wound around their cores such that lower ends thereof have opposite polarities. FIG. 3 shows the polarities N and S at a certain point in time. Therefore, by appropriately selecting the magnitude and direction of the current flowing through each electromagnetic coil pair, a rotating magnetic field or a magnetic field of any direction or magnitude can be generated in a plane parallel to the connecting yoke 48. . Here, for convenience, the magnetic field generated by the electromagnetic coils 46A, 46A arranged vertically in FIG. 3 is a first magnetic field M1 (X direction), and the magnetic field generated by the other electromagnetic coils 46B, 46B is a second magnetic field. M
2 (Y direction).

FIG. 5 shows a connection state between the above-mentioned electromagnetic coils and the MR element 8. One of the amplifiers 42A is provided with a pair of electromagnetic coils 46A for generating a first magnetic field of the upper and lower magnetic field applying means 24, 24. 46A is connected to the other amplifier 42B.
Include a pair of electromagnetic coils 46B, 46B for generating a second magnetic field.
Is connected. That is, the upper and lower magnetic field applying means 24, 2
4 synchronously generates a magnetic field in the same direction and of the same magnitude. The strength of the magnetic field applied to the MR element 8 depends on the distance between the magnetic field applying means 24 and the element 8, and decreases exponentially as the distance increases. For this reason, in order to always keep the magnetic field strength constant at each measurement, it is necessary to set the distance accurately to a constant value. However, if the magnetic field applying means 24 is provided so as to sandwich the substrate W from both sides, current is applied so that both generate a magnetic field in the same direction, and the substrate is placed substantially in the middle between the two, the magnetic field strength at the substrate position will be The sum of the magnetic fields from the applying means 24, 24 becomes very small, and the distance dependency becomes very small.
The reason for using the two magnetic field applying means is to maintain high reproducibility of the magnetic field strength on the MR element surface. If a certain degree of reproducibility of the magnetic field can be ensured, one of the two magnetic field applying means is used. Only means may be provided.

FIG. 6 is a block diagram of a process of processing using a soft wafer in the judgment means 38. The characteristic line calculating section 54 calculates a characteristic line based on the detected resistance value. The calculation unit 56 calculates a deviation between the characteristic line and each detection resistance value and sums the deviation. The comparing unit 58 calculates the ratio between the sum of the deviations and the amount of change in the resistance value of the MR element.
Is to determine whether or not this ratio has reached a predetermined determination value, thereby determining the quality of the MR element.

Next, the method of the present invention performed using the magnetic head inspection apparatus having the above-described structure will be described. First, prior to the description, the direction of the magnetic field is defined with reference to FIG. FIG. 7 shows an enlarged view of the MR element 8,
Electrode films 62, 62 are formed on both sides of the stripe-shaped MR element 8.
(See FIG. 23). As shown in the figure, on the plane parallel to the element plane,
And a magnetic field in the left-right direction orthogonal to the first magnetic field is referred to as a second magnetic field M2. As mentioned above,
The magnetic field M1 is generated by a pair of electromagnetic coils 46A, 46A arranged vertically opposite in FIG. 3, and the second magnetic field M2 is generated by a pair of electromagnetic coils 46B, 46B arranged right and left in FIG. Is done.

First, the operation of the entire apparatus will be described. In response to a command from the control computer 38, a coil current flows through the upper and lower magnetic field applying means 24, 24, and a predetermined horizontal magnetic field is applied to the substrate W. At the same time, a bias current flows from the bias current source 34 to the MR element via the probe needle 22 connected to the pad of the MR element.
Then, by sequentially changing the magnetic field according to a predetermined procedure, the resistance value of the MR element is detected by the resistance detecting means 36 each time, and the detected resistance value is controlled by the control computer 3.
8 and perform a determination operation. Thus one M
When the determination of the R element is completed, the stage 16 is moved to the head 1 position.
It is shifted by the amount of the chip, and the next MR element is similarly determined. Similarly, all the MR elements on the substrate surface are determined by intermittently moving the stage.

Next, the first invention method will be described.
In this first invention method, two electromagnetic coil pairs 46A,
A rotating magnetic field is applied to the MR element surface by flowing a sinusoidal current having a phase shift of 90 ° in electrical angle to 46A, 46B, 46B for one cycle, and the resistance value at that time is intermittently detected. In other words, a rotating magnetic field is intermittently applied one rotation so as to be parallel to the surface of the MR element while flowing a bias current through the MR element. In this case, the magnetic field strength is, for example, 40
It is preferable to set a uniform magnetic field of about Oe and to set the same as the magnetic field intensity from an actual magnetic recording medium. Then, the resistance value of the MR element is detected every time the angle changes during the rotation. The quality of the MR element is determined based on the detected resistance value.

In this determination method, a basic characteristic line determined by each detection resistance value is obtained using, for example, a Fourier series, and the ratio of the standard deviation of each detection resistance value to the basic characteristic line and the maximum change amount of the detection resistance value is determined. Is determined, and the value of this ratio is determined based on the determination value. More specifically, FIG. 8 shows the detected resistance value of the MR element when the rotating magnetic field is intermittently rotated once (360 °), and the black circles in the figure show the detected resistance values. In the illustrated example, the resistance values at the time of rotation at 17 locations at equal intervals are plotted. The resistance value changes substantially sinusoidally as the rotating magnetic field rotates. In actual measurement, a large number, for example, about 200 points are detected.
Here, for simplicity of description, the number of measurement points is reduced. In the illustrated example, the resistance of the MR element is approximately 28.2.
It changes in the range from 6Ω to 28.36Ω.

When the detected value changes smoothly as described above, the stability in the reproducing operation is good, and when the detected value changes like a sharp jump on the way, the stability is improved. The inventor of the present invention has found that the degree of stability is not good. However, the degree of the stability is not so clear visually in the graph shown in FIG. Try converting the graph to polar coordinates. The minimum value of the detection resistance Ri is defined as Rmin and dR
= Ri−Rmin, and the rotation direction of the magnetic field is θ, R
Take i = dR (θi). FIG. 9 shows the polar coordinates represented in this manner. The curve of the graph has a so-called inverted heart shape, and FIG. 10 shows a polar coordinate graph when a large number of detected resistance values are actually plotted.

FIG. 11A shows a polar coordinate graph when an MR element having good characteristics is actually measured, and shows a substantially heart-shaped curve which changes relatively smoothly. FIG. 11B shows a polar coordinate graph when an MR element having poor characteristics is actually measured, and FIG.
The measured value jumps greatly as compared with, and the heart shape is also greatly collapsed. Generally, a magnetoresistive effect element utilizes a phenomenon caused by rotation of a single magnetization.
The measurement result shown in FIG. However, when the magnetization in the element is not uniform and has a plurality of magnetic domains, it always has a domain wall, and in response to a change in an externally applied magnetic field, discontinuous movement of the domain wall or The occurrence and disappearance of new magnetic domains occurs. Accordingly, a discontinuous change occurs in the electric resistance value, and a jump shown in FIG. 11B appears. This is called Barkhausen noise.

Returning to FIG. 8, in order to measure the degree of the jump in the detected resistance value numerically, not visually, in the present invention, the measured data is approximated using a Fourier series. , And obtain a basic characteristic line. That is, the first term of the Fourier series is changed to Ro +
A basic characteristic line is obtained by setting ΔR and the second term as ΔR · sin (θ + φ). In FIG. 8, the basic characteristic line 64 thus obtained is shown by a solid line. Next, the deviation calculation unit 56
The standard deviation σ of each detection resistance value and the above-mentioned basic characteristic line is obtained from the following equation (1).

[0029]

(Equation 1)

Next, the ratio between the standard deviation and the maximum change amount of the detected resistance value is defined as a stability index M in the comparing section 58, and the ratio is obtained by Expression 2. M = σ / (2 · ΔR) (2) Then, the judgment unit 60 judges the quality of the MR element based on whether the stability index M is larger than a predetermined judgment value. As the discrimination value, for example, a range of 0.02 or less can be used.

The above flow will be described with reference to the flowchart shown in FIG. First, the substrate W is placed on the stage 16.
And the alignment is performed (S1), and a bias current is supplied to the MR element (S2). Next, the direction of the rotating magnetic field is set to θ = 0 (S3), and the corresponding sin θ
And the current value of cos θ are obtained and output to the D / A converter to apply a magnetic field (S4). Next, the voltage of the RM element at this time is measured (S5). And this S4
Steps S5 to S5 are performed by increasing θ by Δθ (S7) until θ becomes 2π (S6). Next, the resistance value of the MR element at each time is measured from each of the detected voltages and the bias currents (S8), and the above-described Fourier coefficient calculation is performed based on the detected resistance values to obtain a basic characteristic line (S8).
9). Next, a standard deviation is calculated from the basic characteristic line and each detected resistance value (S10), and a stability index M is calculated (S11). Then, it is determined whether or not the stability index M is equal to or less than the discrimination value (S12), and the result is stored in a storage unit (not shown) of the computer or the monitor 3
2 to display an image.

FIG. 13 shows the relationship between the degree of the defective characteristics measured by the conventional method and the reproduction instability measured by the method of the present invention. What was judged as a non-defective product was also judged to be substantially defective in the inspection method according to the method of the present invention, and it was found that according to the inspection method of the present invention, the quality of the head can be accurately determined. In addition, a wire having a wire diameter of 0.35 mm was used as each of the electromagnetic coils 46A and 46B of the magnetic field applying means.
It was manufactured by winding 00T (turn). S for York
When a ferrite material made of B-7C material (manufactured by Hitachi Metals, Ltd.) was used, the resistance of each coil was 2Ω and 13 m
H inductance. When a current of 1 amp was passed through this coil, a magnetic field of 150 Oe was obtained at the center,
A magnetic field of 100 Oe was obtained at a distance of 5 mm, and a magnetic field applying means that could be used practically was obtained.

As described above, by measuring the electric resistance while applying the rotating magnetic field to the surface of the MR element, it is possible to easily judge the quality of the product based on the measurement result. Accordingly, it is possible to obtain a magnetic field strength sufficient for evaluating an MR element without using a large and expensive Helmholtz coil as used in the prior art.
There is no need to omit the shield layer as disclosed in Japanese Patent No. 105286. Moreover, since the inspection can be performed with a device having a simple structure, not only can the equipment cost be reduced,
Inspection work can also be performed quickly. Furthermore, reproduction instability and the like that cannot be measured by the conventional inspection method can be measured, so that a more reliable inspection can be performed. Further, in this embodiment, in the state of the substrate, the MR
Although the element was inspected, it is needless to say that the element can be inspected in the state of the head block or the head alone.

In the above-described embodiment, in order to generate a rotating magnetic field, the four electromagnetic coils 46A and 46B are arranged in a cross shape, and an alternating current having a phase difference of 90 ° is caused to flow therethrough. Without limitation, for example, as shown in FIG.
One coil 100A, 100B, 100C may be used. These three coils 100A, 100B, 100
C is a projection 1 of an annular soft magnetic material having projections.
02A, 102B, and 102C, and each coil has a sine wave signal source whose three phases are different from each other by 120 °, that is, balanced three-phase AC power supplies e1, e2, and e3.
It is connected to the. According to this, the magnetic field H rotates at the predetermined angular velocity ω at the center. The present invention is not limited to this structure. Further, for example, as shown in FIG. 15, a pair of permanent magnetic fields 66 are provided on a cylindrical yoke 68 with the N-pole side and the S-pole side facing each other. Reducer 7
The permanent magnet 66 may be rotated by transmitting the yoke 68 to the yoke 68 via the second member 2 to form a rotating magnetic field at the end of the magnet. In this case, a ferrite magnet having a thickness of 3 mm and a width of about 8 mm is used as the permanent magnet 66,
The diameter of the yoke 68 is set to about 11 mm. And
The magnetic field at the end of the magnet is about 50 Oe. As shown in FIG. 16, two large and small Helmholtz coils 74 and 76 having a cylindrical shape are arranged so that their central axes are orthogonal to each other.
A rotating magnetic field may be formed inside by flowing a current shifted by 0 °. In this case, the horizontal coil 74
Generates a second magnetic field, and the vertical coil 76 generates a first magnetic field.

In the above-described first invention method, the resistance value when a rotating magnetic field is applied to the MR element to be inspected is measured. However, the present invention is not limited to this. The inspection may be performed by combining the measurement value obtained by the magnetic field application method according to the conventional method with the measurement value measured by applying the magnetic field according to the conventional method while applying a constant magnetic field in a direction orthogonal to the magnetic field application method. That is, in this inspection method, in the inspection method of the magnetic head using the magneto-resistance effect element, the first bias is applied in one direction so as to be parallel to the surface of each magneto-resistance effect element while flowing a predetermined bias current.
A first detection step of detecting a change in the resistance value of the magnetoresistive element by applying while changing the magnetic field of
A step of obtaining an approximate characteristic line based on the obtained resistance value, and a state in which a predetermined second magnetic field is applied in a direction different from the first magnetic field in parallel to the element surface while flowing a predetermined bias current. A second detection step of detecting a change in the resistance value of the magnetoresistive element by applying the first magnetic field while changing the resistance value; and a resistance value of the second detection step and the approximate characteristic line. And a judging step of judging the quality of the magnetoresistive element based on the deviation and the resistance change amount in the first detecting step.

Here, the first magnetic field and the second magnetic field are set in directions orthogonal to each other on the MR element surface as shown in FIG. 7, and the first magnetic field M1 is magnetic recording. The setting is made so as to coincide with the fluctuation direction of the signal magnetic field from the medium. In the first step, similarly to the conventional method, the magnetic field is gradually changed in the same direction (Y direction in FIG. 7) as the signal magnetic field from the magnetic recording medium, for example, from -40 Oe to +40 Oe. The resistance value of the MR element is measured. In FIG. 17, black circles indicate the measured values obtained as described above. Next, using the resistance value (measured value) obtained as described above, an approximate characteristic line 78 is obtained by, for example, the least square method.

Next, as a second detection step, a predetermined magnitude, for example, 40, is set in a direction orthogonal to the first magnetic field M1.
In the state where the second magnetic field M2 of about Oe is applied, the first magnetic field M1 is set to −40 in the same manner as in the first detection step.
The resistance value of the MR element is measured while gradually changing it from Oe to +40 Oe. The measurement values thus obtained are represented by white circles in FIG. Next, a standard deviation of each measurement value obtained in the second step with respect to the approximate characteristic line is obtained. Then, the quality of the MR element is determined based on the obtained standard deviation. In this case, if the MR element is good, the standard deviation is small, and if it is defective, it is large. The method of applying a magnetic field as described above can be performed by using the magnetic field applying means shown in FIGS. Further, the above-described processing on the measured values is processed by software using the blocks shown in FIG.

Next, the above steps will be described in detail with reference to the flowchart shown in FIG. First, the substrate W is placed on the stage 16 to perform this alignment (S2).
1) A bias current having a predetermined magnitude is supplied to the MR element (S22). Next, the magnitude Hx of the second magnetic field M2 is set to zero, and the magnitude Hy of the first magnetic field M1 is set to -40 Oe (S23). In this state, the magnetic field is output to the D / A converter to apply the magnetic field (S24), and the resistance value R at this time is applied.
(Hy, 0) is measured (S25). Such a measuring operation is performed while increasing the first magnetic field M1 by a small amount ΔHy (S27), and the magnitude of the first magnetic field M1 is increased by +4.
The process is performed until the value reaches 0 Oe (S26). The measurement values thus obtained correspond to the black circles in FIG.

Next, a number of obtained measured resistance values R (H
y, 0) by applying the least squares method to change these resistance values to Hy
And an approximate characteristic line 78 as shown in the following equation is obtained (S28). R (Hy, 0) ≒ A · Hy + B where A and B are constants. Next, the magnitude of the second magnetic field M2 is maintained from zero to ΔHx, and the magnitude Hy of the first magnetic field M1 is again reduced to −Hx as described above.
It is set to 40 Oe (S29). Note that ΔHx is set to, for example, about 40 Oe. Then, the signal is output to the D / A converter to apply a magnetic field to the MR element (S30),
The resistance value R (Hy, ΔHx) of the MR element at that time is measured (S31). Then, the first magnetic field is changed to +40 Oe.
(S32, S33), and each time the resistance value is measured. The resistance value thus obtained is shown in FIG.
7 are represented as open circles. Next, the standard deviation σ of the difference between the resistance value R (Hy, ΔHx) thus obtained and the approximate characteristic line 78 is determined (S34).
Note that the measured resistance value R (H
y, 0) may be used.

Then, a ratio M 'between the obtained standard deviation σ and the resistance change of the first magnetic field is obtained (S35), and whether this ratio M' is within a predetermined discrimination value, for example, 0.02 or not. Then, the quality of the MR element is determined (S36). The obtained determination result is displayed on the display as an image or stored in the storage unit as data (S39).
Although 0.02 is used here as the discrimination value, this is merely an example, and this value naturally varies depending on the finally obtained MR element characteristics. As described above, the measured resistance value when the first magnetic field is changed little by little with the second magnetic field set to zero, and the first resistance with the second magnetic field set to a small magnitude ΔHx. The quality of the MR element can also be determined by using the measured resistance value when the magnetic field is slightly changed.

In the second method invention, the characteristic line is mainly obtained from the measured resistance value, and the quality of the MR element is determined by referring to the deviation from the characteristic line. Alternatively, the characteristic line may not be obtained. That is, in the method of the present invention, the first magnetic field and the second magnetic field are applied in two different directions so as to be parallel on the surface of the magnetoresistive element while flowing a predetermined bias current, and the first magnetic field is applied. While changing the size of the
A measuring step of changing the second magnetic field to a different value including zero at each change point, and measuring a resistance value of the magnetoresistive element each time, and a measurement when the second magnetic field is applied A step of determining a swing of the resistance value; and a determining step of determining the quality of the magnetoresistive element based on the amount of resistance change caused by the change in the first magnetic field and the maximum swing of the swing. Prepare.

In order to realize each of the steps, the judgment means of the computer obtains the maximum amplitude of the measured resistance value when the second magnetic field is applied based on the detected resistance value as shown in FIG. A maximum swing calculating section, a resistance change calculating section for calculating a resistance change caused by a change in the first magnetic field, and judging the quality of the magnetoresistive element based on the obtained resistance change and the maximum swing. A determination unit. In FIG. 20, the measured value represented by a black circle indicates a value when the magnitude of the second magnetic field is zero, and the measured value represented by a white circle indicates that the magnitude of the second magnetic field is For example, when + ΔHx is indicated,
The measurement value represented by a white triangle indicates when the magnitude of the second magnetic field is, for example, −ΔHx.

Here, the above-mentioned steps will be described in detail with reference to the flowchart shown in FIG. First, the substrate W is placed on the stage 16 to perform this alignment (S51), and the MR
A bias current of a predetermined magnitude is applied to the element (S52).
Next, the magnitude of the first magnetic field M1 is set to −40 Oe,
The magnitude Hy of the magnetic field M2 is set to zero (S53), this is output to a D / A converter to apply the set magnetic field to the MR element (S54), and the resistance value at this time is measured (S5).
5). The measured resistance value at this time is R (Hy = −40, Hx =
0).

Next, the magnitude Hx of the second magnetic field M2 is output to the D / A converter as Hx = 0 (S56), and the resistance value R (0) at this time is measured (S57). Next, Hx = −Δ
It is output to the D / A converter as Hx (S58), and the resistance value R (−ΔHx) at this time is measured (S59). Next, Hx = + ΔHx is output to the D / A converter (S60), and the resistance value R (+ ΔHx) at that time is measured (S61). That is, the resistance value is measured at three points when Hx is 0, −ΔHx, and + ΔHx while Hy = −40 Oe is maintained. Then, the maximum value and the minimum value among the above three points are obtained to obtain the swing width dRx (S62). Then, the first magnetic field M1 is increased by + ΔHy in increments of +40
The above steps S56 to S62 are repeated each time until Oe is reached (S63, S64). When the first magnetic field M1 reaches +40 Oe, the magnitude Hx of the second magnetic field M2 is set to zero and output to the D / A converter (S65), and the resistance value R (Hy = 40 at this time) , Hx
= 0) is measured (S66).

Next, the ratio M ″ between the maximum deflection width (maximum resistance change) among the above-described deflection widths and the resistance change with respect to the first magnetic field.
(S67). Then, the quality of the MR element is determined based on whether the ratio M ″ is smaller than a predetermined determination value, for example, 0.1 (S68), and the result is displayed on a screen or displayed in a storage unit as data. As described above, while increasing Hy by ΔHy, Hx is measured at each of three points of 0, + ΔHx, and −ΔHx, and the swing width at that time is defined as dRx, and the obtained maximum d is obtained.
Rx is divided by the first resistance change in the magnetic field direction obtained also from the conventional measuring method, and when the ratio M ″ is 1/10 or less, it can be determined as a non-defective product. It is needless to say that the magnetic field other than the above-described rotating magnetic field can be appropriately changed according to the required MR element characteristics.
6 can be performed by the magnetic field applying means shown in FIG. 6, and it is not limited to these devices.

[0046]

As described above, according to the magnetic head inspection method and apparatus of the present invention, the following excellent operational effects can be obtained. In the first invention, the quality of the magnetoresistive element can be easily determined by performing a predetermined process on the resistance value obtained by applying a rotating magnetic field to the magnetoresistive element and measuring the resistance value. Further, in the second invention, for example, the first element having the same direction as the magnetic signal component from the magnetic recording medium is provided to the magnetoresistive element.
The resistance value is measured by applying while changing the magnetic field of
In a state where a second magnetic field orthogonal to this is applied while being maintained at a constant value, the resistance is measured by applying the first magnetic field while changing it, and a predetermined process is performed on these resistance values.
The quality of the magnetoresistive element can be easily determined.

In the third aspect of the present invention, the first magnetic field in the same direction as the magnetic signal component from the magnetic recording medium is gradually increased in the magnetoresistive element, and the second magnetic field orthogonal to the first magnetic field is increased each time. Is shaken at three points to measure the resistance,
By performing a predetermined process on these resistance values, the quality of the magnetoresistive element can be easily determined. Further, since the structure of the magnetic field applying means for applying a rotating magnetic field or a linear magnetic field as described above is very simple, not only can the apparatus cost be significantly reduced, but also the case where the magnetic head to be inspected is a single unit. Inspection can be performed at any stage, even in the case of a block body connected in a straight line, or in a case where the block body is arranged on a substrate before cutting.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a magnetic head inspection apparatus according to the present invention.

FIG. 2 is a plan view of a magnetic field applying unit.

FIG. 3 is a sectional view showing a magnetic field applying unit.

FIG. 4 is a perspective view showing the inside of a magnetic field applying unit.

FIG. 5 is a diagram showing a circuit configuration of the inspection device.

FIG. 6 is a diagram showing a processing block.

FIG. 7 is an enlarged view showing a magnetoresistive element.

FIG. 8 is a graph showing a change in resistance of an MR element when a rotating magnetic field is applied.

FIG. 9 is a graph obtained by converting the graph shown in FIG. 8 by polar coordinates.

FIG. 10 is a graph showing actual measured resistance values in polar coordinates.

FIG. 11 is a graph showing an example of polar coordinates of the resistance value of a good RM element and the resistance value of a bad MR element.

FIG. 12 is a flowchart showing the steps of the first method invention.

FIG. 13 is a graph showing a correlation between a conventional inspection method and an inspection method according to the method of the present invention.

FIG. 14 is a perspective view showing another example of the magnetic field applying means.

FIG. 15 is a perspective view showing still another example of the magnetic field applying means.

FIG. 16 is a perspective view showing still another example of the magnetic field applying means.

FIG. 17 is a graph showing an example of a measured resistance value according to the third method invention.

FIG. 18 is a flowchart of the steps of the third method invention.

FIG. 19 is a block diagram of a determining means according to the second invention.

FIG. 20 is a graph showing an example of a measured resistance value according to the second method invention.

FIG. 21 is a flowchart of the steps of the second method invention.

FIG. 22 is a perspective view showing a general magnetic head using an MR element.

FIG. 23 is an enlarged perspective view of a magnetoresistive element of a magnetic head as viewed from a magnetic medium side.

FIG. 24 is a perspective view showing a block body of the magnetic head shown in FIG. 21;

[Explanation of symbols]

 2 Magnetic Head 8 Magnetoresistive Element 14 Magnetic Head Inspection Device 16 Stage 20 Probe Card (Probe Means) 22 Probe Needle 24 Magnetic Field Applying Means 34 Bias Current Source 36 Resistance Detecting Means 38 Judgment Means (Control Computer) 44 Leg Core 46A, 46B Electromagnetic coil 48 Connecting yoke 52 Viewing hole 54 Characteristic line calculation unit 56 Deviation calculation unit 58 Comparison unit 60 Judgment unit 64 Basic characteristic line 74, 76 Helmholtz coil 78 Approximate characteristic line 80 Maximum deflection width calculation unit 82 Resistance change calculation Unit 84 control unit

Continuation of front page (56) References JP-A-5-347013 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G11B 5/39 G11B 5/455

Claims (11)

(57) [Claims] 1. A method for inspecting a magnetic head using a magnetoresistive element, wherein a predetermined bias current is applied to the magnetoresistive element while applying a rotating magnetic field so as to be parallel to a surface of the element. Detecting a resistance change of the magnetoresistive element at the time of applying the rotating magnetic field, and determining whether the resistance is good or bad based on the detected resistance change , wherein the determination step is based on each detected resistance value. Basic characteristics determined
The standard deviation of each detection resistance value with respect to the line and the detection resistance value
A method for inspecting a magnetic head, wherein the determination is performed based on a ratio of a maximum change amount . 2. A method for inspecting a magnetic head using a magnetoresistive element, wherein a first magnetic field is changed in one direction so as to be parallel to a surface of each of the magnetoresistive elements while flowing a predetermined bias current. A first detection step of detecting a change in the resistance value of the magnetoresistive element by applying the voltage while applying a bias voltage; a step of obtaining an approximate characteristic line based on the obtained resistance value; In a state in which a constant second magnetic field is applied in a direction different from the first magnetic field in a direction parallel to the plane, the first magnetic field is applied while being changed, thereby changing the resistance value of the magnetoresistive element. A second detection step of detecting the magnetic field, a step of calculating a deviation between the resistance value of the second detection step and the approximate characteristic line, and a step of detecting the magnetic field based on the deviation and the resistance change amount in the first detection step. Good resistance effect element A method of inspecting a magnetic head, comprising: 3. A method for inspecting a magnetic head using a magnetoresistive element, wherein a first magnetic field is applied in two different directions so as to be parallel to a surface of the magnetoresistive element while flowing a predetermined bias current. Applying a second magnetic field, the first
A measuring step of changing the second magnetic field at each change point to a different value including zero while each time changing the magnitude of the magnetic field by a predetermined amount, and measuring a resistance value of the magnetoresistive element each time; Determining the amplitude of the measured resistance value when the second magnetic field is applied; and determining the magnetic field based on the amount of resistance change caused by the change in the first magnetic field and the maximum amplitude of the amplitude. A determining step of determining the quality of the resistance effect element. Wherein said second magnetic field, the inspection method of a magnetic head according to claim 2, wherein the zero and the absolute value is changed to a magnetic field different same direction. 5. The inspection method of the first magnetic field and said second magnetic head of any to <br/> of claims 2 to 4 magnetic field, characterized in that are orthogonal. 6. An apparatus for inspecting a magnetic head using a magnetoresistive element, comprising: a probe means electrically connected to each pad of the magnetoresistive element; and a probe parallel to a surface of the magnetoresistive element. Magnetic field applying means for applying a first magnetic field and a second magnetic field in at least two different directions; resistance detecting means for detecting a resistance value of the magnetoresistive element at the time of applying the magnetic field; Determining means for determining acceptability based on the resistance value , wherein the determining means determines a characteristic based on the detected resistance value.
A characteristic line calculating unit for obtaining a line, the characteristic line and the detected
A deviation calculator for calculating a standard deviation from each resistance value.
Between the sum of the differences and the change in the resistance of the magnetoresistive element
A comparison unit for determining a ratio, and whether the value of the ratio has reached a discrimination value
Testing apparatus of the magnetic head, characterized in that it comprises a determination section for determining whether. 7. An inspection apparatus for a magnetic head using a magnetoresistive element, wherein a probe means electrically connected to each pad of the magnetoresistive element and a probe parallel to a surface of the magnetoresistive element. Magnetic field applying means for applying a first magnetic field and a second magnetic field in at least two different directions; resistance detecting means for detecting a resistance value of the magnetoresistive element at the time of applying the magnetic field; Determining means for determining acceptability based on the resistance value , wherein the determining means performs a second determination based on the detected resistance value.
The maximum deflection of the measured resistance value when applying a magnetic field of
Maximum swing width calculator and change caused by first magnetic field
A resistance change amount calculating section for calculating the resistance change amount, and the obtained resistance change amount.
Of the magnetoresistive effect element based on the amount of
An inspection apparatus for a magnetic head, comprising: a determination unit for determining pass / fail . 8. The magnetic field applying means includes a pair of two electromagnetic coil pairs, which are separated from each other so that their ends have opposite polarities by flowing a current, so as to be orthogonal to each other. testing apparatus of the magnetic head according to claim 6, wherein being configured by arranging. 9. The magnetic head inspection apparatus according to claim 6 , wherein said magnetic field applying means comprises two sets of Helmholtz coils for forming magnetic fields so as to be orthogonal to each other . 10. The apparatus according to claim 6, wherein said magnetic field applying means is arranged on both sides of the object to be inspected .
An inspection device for a magnetic head according to any one of the above. The method according to claim 11 wherein said magnetic field applying means, by passing a current 90 ° phase shifted from each other by an electrical angle, more of claims 6 to 10, characterized by being configured so as to generate a rotating magnetic field testing apparatus of the magnetic head crab according.