JP3488881B2 - Defect inspection method in magnetic transfer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect inspection method for a magnetic recording medium used in a hard disk device or a floppy (registered trademark) disk device. The present invention also relates to a magnetic recording / reproducing device.

[0002]

2. Description of the Related Art At present, a magnetic recording / reproducing apparatus tends to have a high recording density in order to realize a small size and a large capacity.

In the field of hard disk drives, which are typical magnetic recording medium devices, the areal recording density has already reached 1
Devices exceeding 0 Gbit / sqin have been commercialized, and one year later, the areal recording density is 20 Gbit / sqin.
It is recognized that the technological progress is so rapid that it is expected that the device will be put to practical use.

The technical background that enables such a high recording density is due to the magnetoresistive element type head capable of reproducing a signal having a track width of only a few μm with good SN while improving the linear recording density. Is large.

Further, as the recording density is increased, it is also required to reduce the flying height of the floating magnetic slider with respect to the magnetic recording medium, and there is an increased possibility that the disk / slider may come into contact with the flying magnetic slider for some reason during the flying. ing. Under such circumstances, the recording medium is required to have a higher smoothness.

In order for the head to scan a narrow track accurately, the head tracking servo technique plays an important role. In a current hard disk drive using such a tracking servo technique, a tracking servo signal, an address information signal, a reproduction clock signal, etc. are recorded on a magnetic recording medium at regular angular intervals. The drive device detects and corrects the position of the head based on these signals reproduced from the head at regular time intervals, thereby enabling the head to accurately scan the track.

Here, as described above, the servo signal, the address information signal, the reproduction clock signal, and the like serve as reference signals for the head to accurately scan the track, so that the writing (formatting) is not performed. High positioning accuracy is required. In the current hard disk drive, formatting is performed by positioning the recording head using a dedicated servo device (servo writer) incorporating a high-precision position detection device using optical interference.

However, there are the following problems in the formatting by the servo writer.

First, the recording by the magnetic head is basically line recording based on the relative movement between the magnetic head and the magnetic recording medium, and since it is necessary to write a signal over many tracks, the method by the servo writer is not used. In addition, it takes a lot of time to perform preformat recording, and a plurality of expensive dedicated servo writers are required to increase productivity, and preformat recording is expensive.

Secondly, a large amount of cost is required to introduce and maintain many servo writers.

These problems became more serious as the track density increased and the number of tracks increased.

Therefore, the formatting is not performed by the servo writer, but the master information carrier on which all the servo information is written and the magnetic recording medium to be formatted are superposed on each other, and transfer energy is externally applied to the master. Has been proposed to collectively transfer the servo information on the magnetic recording medium.

As an example thereof, Japanese Unexamined Patent Publication No. 10-40544
An example is the magnetic transfer device disclosed in the publication.

In this publication, a magnetic portion made of a ferromagnetic material is formed on the surface of a substrate in a pattern shape for an information signal to form a master information carrier, and the surface of this master information carrier is
Contacting the surface of a sheet-shaped or disk-shaped magnetic recording medium on which a ferromagnetic thin film or a ferromagnetic powder coating layer is formed,
A method of recording a magnetic pattern having a pattern shape corresponding to an information signal formed on a master information carrier on a disk-shaped magnetic recording medium by applying a predetermined magnetic field is disclosed.

[0015]

By the way, in the recording of an information signal using such a conventional magnetic transfer device, a disk-shaped magnetic recording medium having an array pattern corresponding to the information signal provided on the master information carrier as a magnetization pattern. However, it is important that information signals of high density are uniformly and stably recorded over the entire surface of the disk-shaped magnetic recording medium.

However, in the above-mentioned conventional magnetic transfer apparatus, when a foreign substance is present between the master information carrier and the disk-shaped magnetic recording medium at the time of magnetic transfer, they are brought into contact with each other so that the surface of the disk-shaped magnetic recording medium is contacted. A depression occurs.

In the conventional magnetic transfer method shown in FIG. 21, when foreign matter is present between the master information carrier and the disk-shaped magnetic recording medium during magnetic transfer, the disk-shaped magnetic recording medium and the master information carrier are brought into contact with each other to perform magnetic transfer. It is a figure which shows the surface shape of the disk-shaped magnetic recording medium after performing, The center circle is a depression part made by the foreign material interposed between the master information carrier and the disk-shaped magnetic recording medium. In addition, FIG.
It is the figure which measured the cross section of this depression.

In FIG. 22, 20 n is provided around the depressed portion which is recessed by about 50 nm from the surface of the disk-shaped magnetic recording medium.
It can be seen that minute protrusions of about m are present.

Here, as described above, the flying height of the floating magnetic slider from the surface of the disk-shaped magnetic recording medium is usually about 20 nm, while the floating amount on the disk-shaped magnetic recording medium is shown in FIG. 21 (22). If such a protrusion of about 20 nm exists, the magnetic head and the disk-shaped magnetic recording medium come into contact with each other during data recording / reproduction. In such a case, the magnetic head is skipped at the moment of contact, and the magnetic head and the disk-shaped The clearance of the magnetic recording medium becomes large and the signal recording / reproducing performance deteriorates, and the magnetic head physically contacts the disk-shaped magnetic recording medium,
This has been a cause of shortening the life of the magnetic head and possibly causing damage to the disk-shaped magnetic recording medium itself.

FIG. 23 shows the state of protrusions on the entire surface of the disk-shaped magnetic recording medium after magnetic transfer when foreign matter is present between the master information carrier and the disk-shaped magnetic recording medium during magnetic transfer. It is the result of optical measurement, and it can be seen that the surface of the disk-shaped magnetic recording medium has protrusions of 20 nm or more.

As described above, when a foreign substance is present between the master information carrier and the disk-shaped magnetic recording medium during magnetic transfer, the magnetic transfer is performed by bringing the disk-shaped magnetic recording medium and the master information carrier into contact with each other. Since protrusions are present on the disk-shaped magnetic recording medium after the transfer, there is a problem that the recording / reproducing performance and the life of the magnetic head are reduced. This problem becomes more and more serious as the flying height between the magnetic head and the disk becomes smaller with the future increase in recording density.

As a method of preventing this problem, a method of optically inspecting the surface defect of the disk-shaped magnetic recording medium after magnetic transfer has been devised. However, in the conventional method, when it is attempted to discriminate even a minute defect caused by magnetic transfer, the disk-shaped magnetic recording medium for performing magnetic transfer needs to be extremely smooth, which causes a problem of increasing cost. It was

This is because if the medium to be magnetically transferred is not ultra-smooth, minute defects will be present on the medium even before the magnetically transferred, so that the defects due to the magnetically transferred can be accurately determined. Because it is difficult.

When a minute defect caused by magnetic transfer occurs, especially when a minute foreign substance adheres to the surface of the master information carrier, the defect of the disk-shaped magnetic recording medium caused by this always occurs. However, even if the defect is minute, it is a serious problem.

Further, if the cause of the minute defect is dust generated from the magnetic transfer device, even if the defect is minute, it may be aggravated. Therefore, it is necessary to take immediate measures. Since it is impossible to detect minute defects, the above problems cannot be prevented.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a defect detection method by magnetic transfer and a magnetic recording / reproducing apparatus capable of surely detecting a minute defect caused by magnetic transfer. And

[0027]

[0028]

[0029]

[0030]

[0031]

[Means for Solving the Problems ] To solve the above problems
The defect inspection of the magnetic recording medium according to claim 1 of the present invention.
The method may already exist on the magnetic recording medium
Defect inspection step and magnetic recording medium that has been subjected to the defect inspection
Keep the mask information carrier in close contact with the body and
The magnetic recording pattern of the magnetic film pattern of the carrier is the above-mentioned defect inspection.
The step of transferring to the medium and the master information carrier
For the magnetic recording medium after transfer that is separated from the
The step of inspecting defects on the magnetic recording medium of
Defect inspection result of the magnetic recording medium of
Through comparison with defect inspection results for magnetic recording media
Defects in this magnetic recording medium caused by the transfer process
The step of inspecting the magnetic recording medium before transfer includes the step of measuring the rotational phase of the magnetic recording medium before transfer with respect to the defect inspection means, and the magnetic recording after transfer. The step of inspecting a defect on a medium includes an operation of measuring a rotational phase of the magnetic recording medium after the transfer to a defect inspecting means, and the step of determining a defect on the magnetic recording medium through the comparison includes It is characterized in that it includes the work of correcting the shift of the two rotation phases.

The operation according to the invention of claim 1 of the present invention is as follows. That is, the magnetic recording medium is mounted on the defect inspecting means, receives the defect inspecting means in the state before transfer, is taken out from the defect inspecting means, is transferred to the adhesion means, and is subjected to the defect transfer of the magnetic recording medium by the adhesion, and It is removed from the contact means and transferred to the defect inspection means again, and undergoes the defect inspection in the state after transfer. The defect inspection means for defect inspection in the state before transfer and the defect inspection means in the state after transfer may be the same or different, but the rotational phase of the magnetic recording medium in the state before transfer and the state after transfer The rotation phase of the magnetic recording medium in this state does not always match exactly.
Rather, it is expected that the probability of deviation will be higher. Therefore, prior to the comparison between the defect inspection result of the magnetic recording medium in the state before transfer and the defect inspection result of the magnetic recording medium in the state after transfer, rotation phase correction for matching the two rotation phases is performed. I am trying. This rotation phase correction is generally performed on the defect inspection result (data). According to the present invention, it is possible to avoid the deterioration of the accuracy of the defect inspection result due to the rotational phase shift and to improve the defect inspection accuracy.

The invention according to claim 2 of the present invention is
2. The defect inspection method for a magnetic recording medium according to 1 , wherein in the correction of the rotational phase, the rotation of the defect detected based on detection of specular reflection light from the magnetic recording medium when the magnetic recording medium is irradiated with light. It is characterized in that the phase is corrected.

The operation of the invention according to claim 2 is as follows. That is, the specularly reflected light is mainly from the depressed portion (hollow) in the magnetic recording medium. On the other hand, the scattered light is mainly from foreign matters such as particles in the magnetic recording medium. The scattered light largely varies in scattering direction and received light intensity due to subtle variations in laser irradiation position and angle. Therefore, in correcting the rotational phase of the magnetic recording medium, the correction is performed based on the rotational phase of the detection defect based on the detection of the specular reflection light whose directionality and intensity are more stable. This makes it possible to improve the defect inspection accuracy.

The invention according to claim 3 of the present invention is
In the defect inspection method for a magnetic recording medium according to 1, the rotational phase of the defect detected based on detection of scattered light from the magnetic recording medium when the magnetic recording medium is irradiated with light in the correction of the rotational phase. Is corrected.

This describes that the rotational phase correction may be performed mainly with scattered light. However, the accuracy of defect inspection tends to be inferior to that in the case of specular reflection light.

The invention according to claim 4 of the present invention is
In the defect inspection method for a magnetic recording medium according to 1 , the correction of the rotational phase is based on detection of specularly reflected light or scattered light from the magnetic recording medium when the magnetic recording medium is irradiated with light. The rotational phase of the detected defect is corrected, and the rotational phase correction of the defect in detecting the specular reflection light is prioritized.

The operation in this case should be easily understood from the above items even if the description thereof is omitted.

It should be noted that, in the above, it is merely stated that the regular reflection light or the scattered light is used in the rotational phase correction, and the use of the regular reflection light or the scattered light in the defect inspection is limited. Do not understand that The defect inspection need not be limited to the optical type. An electron microscope method or any other known method may be used.

[0040]

[0041]

According to a fifth aspect of the present invention, in the defect inspection method for a magnetic recording medium according to any one of the first to fourth aspects, a defect inspection step for the magnetic recording medium before transfer is performed. Is for extracting position information of a defect on the magnetic recording medium before the transfer, and the step of defect inspection for the magnetic recording medium after the transfer is performed by the position information of the defect on the magnetic recording medium after the transfer. To extract
The step of determining a defect on the magnetic recording medium through the comparison determines the difference between the position information of the defect on the magnetic recording medium before the transfer and the position information of the defect on the magnetic recording medium after the transfer, When they are the same, it is determined that there is no defect in the magnetic recording medium, and when they are different, it is determined that there is a defect.

The operation of the invention according to claim 5 of the present invention is as follows. When the defect position information on the magnetic recording medium before transfer is the same as the defect position information on the magnetic recording medium after transfer, it is determined that the magnetic recording medium has no defect. However, since such a determination method is based on defect position information, it is necessary to perform a detailed inspection or defect analysis of the magnetic recording medium after it is determined that the magnetic recording medium has a defect. In addition, it is advantageous to obtain detailed data of what kind of defect exists at what coordinate. That is, whether the defect is an abnormal protrusion or a foreign substance,
Furthermore, it becomes easy to judge what kind of distribution is present. This is an effective technique for cleaning and reusing a magnetic recording medium.

The invention according to claim 6 of the present invention is
In the defect inspection method for a magnetic recording medium as described in 5 , when defects are continuously identified over a plurality of minute unit areas that divide the entire area of the magnetic recording medium into a large number,
Considering the continuous unit areas as one area,
It is characterized in that the center of gravity of the deemed region or its vicinity is used as the position information of one defect.

The operation of the invention according to claim 6 of the present invention is as follows. That is, it is empirically known that, when a plurality of unit areas that are determined to have defects are continuous, it is highly possible that they are individually discriminating different portions of a single defect. It is possible to improve the accuracy of defect inspection by regarding a linear defect having a length longer than a certain amount and a defect having a spread larger than a certain amount as one defect.

[0046]

[0047]

[0048]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of a magnetic disk defect inspection method according to the present invention will be described below with reference to the drawings.

(Embodiment 1) The contents of magnetic transfer in Embodiment 1 of the present invention will be described with reference to FIGS.

In this embodiment, in order to eliminate defects caused by the master information carrier 2 at the time of transfer, the master information carrier determined to have no defect as a result of the defect inspection. 2 is used.

FIG. 1 is a sectional view of a magnetic transfer apparatus according to this embodiment, showing a state in which a master information carrier 2 for magnetic transfer and a magnetic disk 1 as a magnetic disk are separated from each other. FIG. 2 shows a master information carrier 2 and a magnetic disk 1.
Shows the state when is in close contact. FIG. 3 is a view showing the contact surface 3 of the master information carrier 2 with the magnetic disk 1, and the grooves 4 extend radially from the center of the master information carrier 2. In the present embodiment, the groove depth is set to about 5 μm.

In FIG. 1, 1 is a magnetic disk, and 2 is a magnetic transfer master for magnetic transfer. Reference numeral 3 denotes a contact surface of the master information carrier 2 with the magnetic disk 1, and the contact surface 3 is provided with a groove 4 radially extending from the center of the master information carrier 2. Reference numeral 5 denotes a boss fixed to the central portion of the master information carrier 2, 6 denotes a support base for supporting the magnetic disk 1, and a ventilation hole 7 for flowing gas is provided in the central portion. Reference numeral 8 is a passage for discharging gas between the master information carrier 2 and the magnetic disk 1 and for sending gas under pressure to the groove 4 which is a space between them, and 9 is a gas discharge port for discharging gas from the passage 8. Reference numeral 10 is a suction pump connected to the gas discharge port 9, and 11 is an exhaust valve for controlling the discharge of gas. Also,
12 is an air supply pump for pumping gas to the passage 8, 13
Is an air supply valve for controlling air supply.

Here, the air supply pump 12 has 0.01 μm.
m air filter is provided (not shown),
It is configured so that foreign matter of 0.01 μm or more does not enter the passage 8. Reference numeral 14 is a holding arm for holding the master information carrier 2, which is fixed to the master information carrier 2.

As a fixing method, there is a method such as adhesion, but as shown in FIG. 1, the master information carrier 2 may be adsorbed by sucking gas from a through hole provided in the holding arm 14.

The holding arm 14 is vertically slidably positioned by a guide member 16 via an upper boss portion.

However, the method of positioning the master information carrier 2 is not limited to the method of using the holding arm 14, and may be carried out by fitting the outer periphery of the boss 5 into the inner peripheral hole of the magnetic disk 1. . In such a case, the shape of the boss 5 is configured as shown in FIG. 4, and the gas between the master information carrier 2 and the magnetic disk 1 is discharged and pumped through the notch 51 provided on the outer peripheral portion of the boss 5. To be done.

Next, the steps of suction / pressure feeding will be described in detail with reference to FIGS.

First, the step of separating by pressure feeding will be described with reference to FIG. Exhaust valve 11 is closed and air supply valve 13
The gas is caused to flow into the passage 8 by operating the air supply pump 12 in a state in which is opened. Then, as shown by the arrow A in FIG. 1, air is pumped upward in the vent hole 7. As a result, the air pressure-fed to the ventilation hole 7 pushes the boss 5 upward, and as shown by the arrow B,
Air is pumped into the groove 4. The air pressure-fed to the groove 4 spreads radially from the center of the master information carrier 2 to the outer periphery through the groove 4. Then, it further escapes from the groove 4 to the atmosphere through the gap between the master information carrier 2 and the magnetic disk 1.

The time elapsed at this time and the master information carrier 2
FIG. 5 shows the relationship between the atmospheric pressure of the space sandwiched between the magnetic disk 1 and the magnetic disk 1 (hereinafter referred to as space S). In FIG. 5, the air pressure in the space S is 101.3 kp after the passage of time of 3 seconds.
Momentary rise from a, then 130 kp for about 1 second
The period in which the atmospheric pressure of about a is maintained corresponds to the state in which the master information carrier 2 and the magnetic disk 1 described above are separated from each other.

In the present embodiment, the upper surface of the holding arm 14 is guided by the guide member when the master information carrier 2 rises 0.5 mm integrally with the holding arm 14 from the state where the magnetic disk 1 and the master information carrier 2 are in close contact with each other. By making contact with the lower surface of 16, the distance between the magnetic disk 1 and the master information carrier 2 is controlled.

Next, the process of adhesion by suction is shown in FIG.
Will be explained.

The air supply pump 12 is stopped and the air supply valve 13 is closed. Then, the holding arm 14 to which the magnetic disk 1 is fixed moves downward due to its own weight, and the boss 5 moves the magnetic disk 1 to the boss 5.
Is mounted on the magnetic disk 1 in a state of being fitted with the inner peripheral hole of the magnetic disk 1. Then, the exhaust valve 11 is opened and the suction pump 10 is operated. Then, the vent hole 7 as indicated by the arrow C in FIG. 2
Since the gas is discharged downward, the gas inside the groove 4, that is, the gas in the space S is also discharged through the gap between the inner peripheral hole of the magnetic disk 1 and the boss 5.

Here, as shown in FIG. 3, since the groove 4 does not have a shape that extends to the outermost periphery of the master information carrier 2, the master information carrier 2 and the magnetic disk 1 are completely formed in the outermost donut-shaped portion. It is in a state of being in close contact with the circumference, the space S is in a sealed state, and its pressure is lower than atmospheric pressure. Therefore, the magnetic disk 1 is pressed against the master information carrier 2 by the atmospheric pressure 15.

In FIG. 5, the section where the air pressure in the space S is about 30 kpa corresponds to the above-mentioned close contact state.

Next, as shown in FIG. 2, the magnet 17 is moved in the direction of arrow D to approach the master information carrier 2,
When the distance becomes about 1 mm, the movement in the direction of arrow D is stopped, and then the magnet 17 is rotated one or more revolutions in the circumferential direction of the magnetic disk 1, that is, around the guide member 16 in the direction of arrow E. By doing so, a magnetic field (external magnetic field) necessary for transfer is applied.

As described above, in magnetic transfer, the operation of the magnetic disk 1 is only close contact / pneumatic pressure, so that the rotational phase of the magnetic disk 1 does not significantly shift before and after magnetic transfer.

Here, the master information carrier 2 will be described with reference to FIGS.
This will be described in detail with reference to FIG.

As shown in FIG. 6 which is a schematic plan view of an example of the master information carrier 2, one main surface of the master information carrier 2, that is, the surface of the magnetic disk 1 which is in contact with the surface of the ferromagnetic thin film, is substantially formed. The signal regions 2a are radially formed. Figure 3
6 and FIG. 6 are schematic diagrams, and in reality, FIG.
The signal area 2a in FIG. 3 is formed on the contact surface in FIG.

An enlarged view of a portion F surrounded by a dotted line in FIG. 6 is schematically shown in FIG. As shown in FIG. 7, a pattern of a digital information signal to be recorded on the magnetic disk is formed in the signal area 2a. For example, a master information pattern is formed at a position corresponding to preformat recording by a magnetic portion formed of a ferromagnetic thin film in a pattern shape corresponding to the digital information signal.

In FIG. 7, the hatched portion is a magnetic portion formed of a ferromagnetic thin film. This Figure 7
The master information pattern shown in (1) is obtained by sequentially arranging areas of the clock signal, the tracking servo signal, the address information signal, etc. in the track length direction. Note that the master information pattern shown in FIG. 7 is an example, and the configuration, arrangement, etc. of the master information pattern will be appropriately determined according to the digital information signal recorded on the magnetic disk.

For example, when a reference signal is first recorded on a magnetic film of a hard disk like a hard disk drive, and preformat recording such as a tracking servo signal is performed based on the reference signal, the master information carrier according to the present invention. Pre-format recording such as tracking servo signals is performed on the magnetic head of the hard disk drive by pre-recording only the reference signal used for pre-format recording on the magnetic film of the hard disk by using the May be used.

A partial cross section of the region shown in FIGS. 6 and 7 is shown in FIG.
Shown in.

As shown in FIG. 8, the master information carrier 2 is
A plurality of minute array patterns corresponding to information signals are formed on one main surface of the disk-shaped substrate 2b made of a non-magnetic material such as a Si substrate, a glass substrate, a plastic substrate, that is, the surface on the side where the surface of the magnetic disk 1 contacts. The recess 2c is formed in a shape, and the ferromagnetic thin film 2d, which is a magnetic part, is embedded in the recess 2c of the base 2b.

Here, as the ferromagnetic thin film 2d, many kinds of magnetic materials can be used regardless of hard magnetic material, semi-hard magnetic material, and soft magnetic material, and a digital information signal is transferred and recorded on the magnetic disk. Anything can be used. For example, Fe, Co, an Fe-Co alloy, or the like can be used.

In order to generate a sufficient recording magnetic field regardless of the type of the magnetic disk on which the master information is recorded, it is preferable that the saturation flux density of the magnetic material is large. In particular,
For a magnetic disk having a high coercive force exceeding 2000 Oersted and a flexible disk having a large magnetic layer thickness, sufficient recording may not be performed when the saturation magnetic flux density is 0.8 Tesla or less, and therefore, in general, it is generally impossible. Is
A magnetic material having a saturation magnetic flux density of 0.8 Tesla or more, preferably 1.0 Tesla or more is used.

The thickness of the ferromagnetic thin film 2d depends on the bit length, the saturation magnetization of the magnetic disk and the film thickness of the magnetic layer. For example, the bit length is about 1 μm and the saturation magnetization of the magnetic disk is about 50.
0 emu / cc, the thickness of the magnetic layer of the magnetic disk is about 20
In the case of nm, it may be about 50 nm to 500 nm.

Here, in such a recording method, in order to obtain good recording signal quality, the pre-recording is performed based on the arrangement pattern of the soft magnetic thin film or the semi-hard magnetic thin film as the ferromagnetic thin film provided on the master information carrier. During format recording, it is desirable to excite it and magnetize it uniformly.
Further, it is desirable that the magnetic disk such as a hard disk is uniformly DC-erased before the signal recording using the master information carrier.

Next, a method for manufacturing the master information carrier 2 will be described.

That is, as the master information carrier used in the recording method of the present invention, a resist film is formed on the surface of a Si substrate, and the resist film is formed by a lithography technique using a laser beam or an electron beam such as a photolithography method. After exposure, development, and patterning, etching is performed by dry etching or the like to form a fine concavo-convex shape corresponding to an information signal, and then a ferromagnetic thin film made of Co or the like is sputtered, vacuum deposited, or ion plated. Method, CVD method, plating method, etc., it is possible to obtain a master information carrier in which a ferromagnetic thin film is embedded in a recess and which has a magnetic portion corresponding to an information signal.

The method of forming the uneven shape on the surface of the master information carrier 2 is not limited to the above-mentioned method, and for example, a fine uneven shape is directly formed by using a laser beam, an electron beam or an ion beam. Alternatively, the fine concavo-convex shape may be directly formed by machining.

Next, the procedure for transferring and recording the information signal corresponding to the pattern shape formed on the master information carrier 2 onto the magnetic disk will be described in more detail with reference to FIGS. 9 to 11.

First, in the state where the magnet is brought close to the magnetic disk 1, the magnet is rotated parallel to the magnetic disk 1 with the central axis of the magnetic disk 1 as the rotation axis, so that the magnetic disk 1 as shown by the arrow in FIG. Is magnetized in one direction in advance (initialization).

Next, as described above, with the master information carrier 2 positioned and superposed on the magnetic disk 1,
The master information carrier 2 and the magnetic disk 1 are brought into close contact with each other uniformly, and then a magnetic field is applied in the direction opposite to the initialization as shown by an arrow E in FIG. The magnetic thin film 2d is magnetized, and the predetermined area 1 of the magnetic disk 1 superposed on the master information carrier 2
In b, an information signal corresponding to the pattern shape of the magnetic portion 2d is recorded as shown in FIG. The arrow shown in FIG. 10 indicates the direction of the magnetic field of the magnetization pattern transferred and recorded on the magnetic disk 1 at this time.

FIG. 11 shows the state during the magnetization process. As shown in FIG. 11, a magnetic field is applied to the master information carrier 2 from the outside while the master information carrier 2 is in close contact with the magnetic disk 1. By magnetizing the magnetic portion 2d by
Information signals can be recorded on the ferromagnetic layer 1c of the magnetic disk 1. That is, by using the master information carrier 2 formed by forming the magnetic portion 2d made of a ferromagnetic thin film in the array pattern shape corresponding to a predetermined information signal on the non-magnetic substrate 2b, the magnetization pattern corresponding to the information signal is used. Can be magnetically transferred and recorded on the magnetic disk 1.

As a method for transferring and recording the pattern of the master information carrier 2 on the magnetic disk 1, other than the method of applying the external magnetic field with the master information carrier 2 in contact with the magnetic disk 1 as described above. There is also a method in which the magnetic portion 2d of the master information carrier 2 is magnetized in advance and the master information carrier 2 is brought into close contact with the magnetic disk 1 in that state. Even with this method, the information signal is transferred and recorded. be able to.

After that, the separating means shown in FIG. 1 is implemented again. That is, the exhaust valve 11 is closed, the air supply valve 13 is opened, and the air supply pump 12 is operated. Then, arrows A and B
As shown in FIG. 3, the gas is pumped, the master information carrier 2 moves integrally with the holding arm 14 by the force of the gas pumping, and stops when the upper surface of the holding arm 14 contacts the guide member 16. At this time, as shown by the arrow B, the gas is kept in a state of being radially pumped from the center of the master information carrier 2 to the outer peripheral side through the groove 4.

Here, if an abnormal protrusion or a foreign substance is present on the contact surface 3 of the master information carrier 2, the magnetic transfer will cause a defect in the magnetic disk 1.

A defect inspection method for a magnetic disk and a magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described with reference to FIGS.

FIG. 12 is a flow chart showing the steps of this embodiment. In FIG. 12, first, in the magnetic disk manufacturing process which is the process of ST1, a magnetic layer is formed on the surface by a known method. The formation of the magnetic layer includes a step of providing the magnetic layer on a substrate made of aluminum, for example, by dry plating means such as vapor deposition or sputtering means. In addition, a method of protecting the magnetic layer is usually adopted by performing a step of providing a protective film on the magnetic layer by dry plating means such as vapor deposition or sputtering means or by dipping or spin coating.

First, the step of inspecting defects on the surface of the magnetic disk, which is the step of ST1 and ST4 of FIG. 12, will be described. The steps ST1 and ST4 are performed by using a defect inspection device which is a well-known means. Optical irradiation is performed by irradiating the surface of the disk with a laser and detecting the shape and size of each defect differently. A property is used, that is, a method of detecting a defect by receiving specular reflection light or scattered light of laser light is used. The outline of the defect inspection apparatus used in this embodiment will be briefly described below.

FIG. 13 is a diagram showing the defect inspection apparatus used in the steps ST1 and ST4 of FIG.
In FIG. 13, 1 is a magnetic disk, 101 is a laser light transmitting system, 102 is a regular reflection light receiving system, 103 is a scattered light receiving system, and 104 is a data processing device. The surface of the magnetic disk 1 is projected by a laser light-transmitting system 101 so as to form a laser spot on the surface of the magnetic disk 1, and a rotary motor for mounting the magnetic disk 1 and a linear drive unit (not shown) are used. The laser spot is spirally scanned.
When there is a defect on the surface of the magnetic disk 1, the laser spot is scattered, so the scattered light is received by the scattered light receiving system 10
3 receives light to obtain a defect data signal. The regular reflection light is received by the regular reflection light receiving system 102. In this way, each light receiving system is provided so as to correspond to the specular reflection light and the scattered light having different light intensities depending on the type of defect. Further, optical elements such as filters and lenses are provided in order to efficiently receive desired light (that is, specularly reflected light and scattered light). The light received by each light receiving system is converted into defect data via a predetermined circuit and input to the data processing device 104.

The defect data signal obtained by receiving light by each light receiving system is a predetermined unit cell on the surface of the disk (in the present embodiment, a minute distance Δ in the radial direction of the disk).
It is stored in the address of the memory corresponding to a unit area which is a minute rectangular cell formed by r and a minute distance Δθ in the circumferential direction. The unit area of the defect inspection apparatus used in this embodiment is Δr = 10 μm and Δθ = 0.125 °.

However, in this state, when a defect having a predetermined length or width such as one dent, scratch, or particle is one defect, but exists in a plurality of continuous unit areas, Instead of being recognized as one defect, many defects are recognized. Therefore, if there is defective data in any of a predetermined number of addresses adjacent to the address storing the defective data, the continuity of each address is identified as being continuous, and the addresses determined to be continuous by this identification. Is evaluated as one defect. As a result, the number of groups of various defects is shown regardless of the size and shape. The position coordinates of a defect are defined as the center of gravity of a group of addresses that are considered to be continuous.

In the defect inspection apparatus used in this embodiment, the surface of the magnetic disk 1 is spirally shaped during the inspection so that the rotational phase of the magnetic disk 1 does not greatly shift when the magnetic disk 1 is loaded and unloaded. A rotary motor (not shown) for scanning is returned to the origin with respect to the rotation phase before and after the defect inspection.

In the step ST1, the magnetic disk before transfer is inspected for defects that may originally exist in the magnetic disk 1 before transfer.

Next, in step ST2, it is confirmed whether or not foreign matter is present on the surface of the magnetic disk 1 before transfer. As a confirmation method, a foreign substance on the magnetic disk 1 before transfer is inspected by using an optical defect inspection method which is a known means. In the present embodiment, an optical inspection apparatus equivalent to ST1 which is different from the defect inspection apparatus of ST1 is used to set the detection slice level of the foreign matter to 1 μm, and the foreign matter of 1 μm or more is present on the surface of the magnetic disk. Inspected for adhesion. After the inspection, if there is a foreign matter of 1 μm or more, it is determined to be NG (defective product), and if it is not present, it is determined to be OK (good product). In the case of OK, the following step ST3 is performed. In the case of NG, the magnetic disk is cleaned and reproduced. If the reproduction is also defective, discard it.

As described above, the foreign matter on the surface of the magnetic disk 1 before transfer is inspected before the adhesion step of ST3, so that the foreign matter on the surface of the magnetic disk 1 before transfer adheres to the master information carrier 2 in reverse. It is possible to prevent the master information carrier 2 from being damaged.

Further, in the step of ST2 as well as in the step of ST1, the rotational phase of the magnetic disk 1 before transfer is not largely shifted at the time of loading and unloading the magnetic disk 1 before transfer so that the rotational phase before transfer is not increased during inspection. Magnetic disk 1
A rotation motor (not shown) for spirally scanning the surface is used to return the origin to the rotation phase before and after the defect inspection.

The step ST3 is a step of bringing the master information carrier 2 into close contact with the defect-inspected magnetic disk 1 before transfer, and is the same as the content described with reference to FIGS.
That is, the magnetic disk 1 in FIGS. 1 and 2 may be replaced with the magnetic disk 1 before transfer, and the other configurations are exactly the same.

After that, the defects on the surface of the magnetic disk 1 after the transfer are inspected. That is, the process of ST4 is performed. The step ST4 is a step for inspecting whether or not a defect has occurred in the magnetic disk 1 by bringing the master information carrier 2 into close contact with the magnetic disk 1 before transfer. The magnetic disk in which the defects on the master information carrier 2 are transferred by the close contact is the magnetic disk after transfer.

14 and 15 show examples of results of defect measurement performed in the step of inspecting defects on the surface of the magnetic disk 1 shown in FIG. FIG. 14 shows a defect inspection result of the magnetic disk 1 performed in the step ST2, and FIG.
The results of the defect inspection carried out in the above step, that is, the results of the defect inspection of the magnetic disk 1 after magnetic transfer are shown. 14
15, the mark ● indicates the center of gravity (center) of the defect received by the specular reflection light receiving element R, and the mark Δ indicates the scattered light received by the first light receiving element L and the second light receiving element D. The center of gravity (center) position of the result is shown.

[0102]

Next, the step of ST5 of FIG. 12, which is a step of discriminating a defect caused by magnetic transfer will be described with reference to FIG. FIG. 16 is a flowchart showing the process of ST5. In FIG. 16, ST6 and ST7
Are the defect inspection results of the steps ST1 and ST4, respectively, and correspond to FIGS. 14 and 15, respectively, in the present embodiment. Step ST8 is a step of detecting the rotational phase shift of the magnetic disk in the defect inspection results of the steps ST1 and ST4. First, as shown in ST9, with respect to the defect inspection result on the surface of the magnetic disk 1 before and after the transfer performed in the step ST1 and the step ST4, the rotational phase and the position at the time of measurement of both can be deviated. Specify a range that has a certain nature. In the present embodiment,
In order to prevent the rotational phase of the magnetic disk from being significantly deviated in the steps ST1, ST2 and ST4,
A return-to-origin function is added to the rotary motor. Also, ST
Since the magnetic disk 1 before transfer is not rotated in the step of contacting No. 3, the rotational phase of the disk does not significantly shift. However, there is a possibility that the rotational phase may be slightly shifted due to the transportation process of the magnetic disk 1 and variations in returning to the origin. It is preferable to specify the maximum value of the variation in the setting range of the rotational phase shift and the positional shift at this time. In the present embodiment, the range of rotational phase shift is set to 10 ° and the range of positional shift is set to 0.5 mm.

Next, step ST10 is carried out. That is, the defect inspection results of the process of ST1 and the process of ST4 are compared, and in the same defect type, the rotational phase shift amount is 10
Defects that are within ° and the amount of displacement is within 0.5 mm are listed. Among them, it is determined whether or not there is a defect detected by the light receiving element of the regular reflection light receiving system 102. If there is a defect detected by the light receiving element of the regular reflection light receiving system 102, as shown in ST11, the phase shift amount between these defects is determined by the magnetic disk 1 and the S before the transfer in the step of ST1.
It is determined as the amount of deviation from the magnetic disk 1 after transfer in the process of T4. If there is no defect detected by the specular reflection light receiving element R, the detection result of scattered light is recognized as a phase shift. As described above, it is preferable to give priority to the result detected by the specular reflection light rather than the result detected by the scattered light of the defect used as the defect for the rotational phase correction. For this reason, see FIG.
Will be explained.

FIG. 17 shows the defect measurement results of the defect inspection apparatus for the magnetic disk 1 used in the steps ST1 and ST4. The origin return is performed for each measurement on the same magnetic disk 1 and the rotary motor is turned on. 20 in succession without removing
It is the result which showed the gravity center (center) position of various defects when the time measurement was performed. In FIG. 17, (a) and (b) are foreign substances, that is, defects detected by the light receiving element of the scattered light receiving system 103, and (c) and (d) are recesses, that is, the light receiving element of the specular reflection light receiving system 102. Each of the defects detected in 1. is shown. Further, the vertical direction in the drawing indicates the radial direction r of the magnetic disk 1, and the horizontal direction indicates the circumferential direction θ of the magnetic disk 1. The unit cell of the defect inspection apparatus used in this embodiment has Δr = 10 μm and Δθ = 0.125 °. The number in each cell indicates the number of times the defect center was detected in that cell. As is clear from the measurement results of FIG. 17, (a) and (b), that is, the variation of the defect position detected by the light receiving element of the scattered light receiving system 103 is (c),
In comparison with (d), that is, the variation in the defect position detected by the light receiving element of the regular reflection light receiving system 102, it can be seen that it is larger. Since the light receiving element of the scattered light receiving system 103 detects the scattered portion of the light from the laser spot,
This is because even if the same defect is detected, if the position or angle of laser irradiation is slightly deviated, it is more likely to cause the position deviation of the detection portion as compared with regular reflection. Therefore, it is preferable to give priority to the result detected by the specular reflection light receiving element over the result detected by the scattered light of the defect used as the defect for which the rotational phase correction is performed.

As is clear from the above, it is possible to perform a more accurate defect inspection by giving priority to the result of detecting the defect used for the defect for rotating phase correction by the regular reflection light receiving element. Become.

Comparing the defect inspection results of the steps ST2 and ST4, the defects detected by the specular reflection light receiving element R have a rotational phase shift amount of 10 ° or less and a positional shift amount of 0.5 mm or less. FIG. 18 shows the result of listing the above. In FIG. 18, ΔR is the radial difference between the defect inspection result of the ST2 process and the defect inspection result of the ST4 process, Δ
θ represents the circumferential difference between the defect inspection result of the step ST2 and the defect inspection result of the step ST4. From FIG. 18, S
In the defect inspection result in the process of T2 and the process of ST4, the magnetic disk rotation phase shift at the time of defect inspection is 8.62.
It can be determined that it is 5 °.

Next, the phase correction shown in ST13 of FIG. 16 is performed. As shown in FIG. 18, ST2 process and S
The phase shift at the time of defect inspection measurement in the T4 process is 8.6.
25 °. Based on this result, the defect inspection result data of the step ST2 is changed to 8.6 in the direction in which the phase shift is corrected.
Rotate 25 °.

Comparing the defect inspection results of the steps ST2 and ST4, the defects detected by the specular reflection light receiving element R have a rotational phase shift amount of 10 ° or less and a positional shift amount of 0.5 mm or less. FIG. 18 shows the result of listing the above. In FIG. 18, ΔR is the radial difference between the defect inspection result of the ST2 process and the defect inspection result of the ST4 process, Δ
θ represents the circumferential difference between the defect inspection result of the step ST2 and the defect inspection result of the step ST4. From FIG. 18, S
In the defect inspection result in the process of T2 and the process of ST4, the magnetic disk rotation phase shift at the time of defect inspection is 8.62.
It can be determined that it is 5 °.

Next, the phase correction shown in ST13 of FIG. 16 is performed. As shown in FIG. 18, ST2 process and S
The phase shift at the time of defect inspection measurement in the T4 process is 8.6.
25 °. Based on this result, the defect inspection result data of the step ST2 is changed to 8.6 in the direction in which the phase shift is corrected.
Rotate 25 °.

Next, the subtraction processing shown in ST14 of FIG. 16 is carried out. That is, the defect inspection result of the step ST2 is subtracted from the defect inspection result of the step ST2 and the step ST4 in which the phase correction is performed in ST13. When performing the subtraction, it is necessary to set the range in which the subtraction is performed by regarding it as the same defect. However, in the present embodiment, the difference in the radial direction r with respect to the defect of the same type is taken into consideration in consideration of the deviation of the positional deviation. 0.0
Defects of 5 mm or less and a difference in the circumferential direction θ of 1 ° or less were regarded as the same defect and subtraction was performed. The result of the subtraction is shown in FIG. FIG. 19 shows defect display data after the subtraction process which is the process of ST14 is performed by the above method. From the results of FIG. 19, one defect was detected by the specular reflection light receiving element R, and two defects were detected by the scattered light reception element R.
It turns out that there are four. As a result of confirming the defective portion with a microscope, the defect detected by the specular reflection light receiving element R is shown in FIG.
It was found that the depressions and defects detected by the light receiving element for scattered light as shown in (4) are fine particles.

By adopting the method as described above, it becomes possible to detect, with high sensitivity and accuracy, a defect on the surface of the magnetic disk, which is generated by magnetic transfer, among the defects existing on the surface of the magnetic disk. Next, the output V of the pit defect detected by the light receiving element of the regular reflection light receiving system 102,
With respect to the position of the defect, the flying height of the head is gradually reduced by a known means such as a glide height test, and the distance d between the magnetic disk 1 and the head when the AE sensor attached to the head starts to hit. Figure 2
It shows in 0.

It can be seen from FIG. 20 that there is a correlation between the output of the defect in the recess detected by the light receiving element of the regular reflection light receiving system 102 and the magnetic disk / head distance. Here, for example, if the flying distance between the magnetic disk / magnetic head of a certain magnetic recording / reproducing apparatus is 20 nm, the detection slice level of the output of the defect of the recess detected by the light receiving element of the regular reflection light receiving system 102, that is, The defect detectable output level is set to a predetermined value lower than Va in FIG. 20,
In the process of ST5, if the detection of the light receiving element of the specular reflection light receiving system 102 is 0, it may be judged as OK, and if it is one or more, it may be judged as NG. When the NG occurs, the defective NG is caused by the abnormal protrusion or the adhering foreign matter of the master information carrier 2. Therefore, the same defect may occur in all the magnetic disks during the magnetic transfer. Therefore, it becomes necessary to observe and remove the defect on the surface of the master information carrier 2 corresponding to the defect position. Regular reflection light receiving system 1 in step ST5
If the detection of the light receiving element 02 is 0, magnetic transfer is performed using the master information carrier 2 that has become OK, and the magnetic disk 1 after magnetic transfer may be incorporated in the drive of the magnetic recording / reproducing apparatus.

By reliably detecting defects in the magnetic disk caused by magnetic transfer by the above method, it is possible to provide a highly reliable magnetic recording / reproducing apparatus.

[0115]

According to the present invention, in the defect inspection of the magnetic recording medium, the defect detection by the magnetic transfer which can surely detect the minute defect caused by the magnetic transfer can be performed with high accuracy. As a result, it is possible to realize a highly reliable magnetic recording / reproducing device.

[Brief description of drawings]

FIG. 1 is a diagram showing a state in which a magnetic transfer master 2 and a magnetic recording medium 1 according to the present embodiment are separated from each other.

FIG. 2 is a diagram showing a state in which a magnetic transfer master 2 and a magnetic recording medium 1 according to the present embodiment are in close contact with each other.

FIG. 3 is a diagram showing a contact surface 3 with a magnetic recording medium 1 in a magnetic transfer master 2 according to the present embodiment.

FIG. 4 is a diagram showing a shape of a boss in the present embodiment.

FIG. 5 is a diagram showing a relationship between time and pressure in space A according to the present embodiment.

FIG. 6 is a diagram schematically showing a plane of an example of a magnetic transfer master according to the present embodiment.

FIG. 7 is an enlarged view of part A of FIG. 7 in the present embodiment.

FIG. 8 is a partial cross section of the region shown in FIGS. 7 and 8 in the present embodiment.

FIG. 9 is a diagram showing initialization in this embodiment.

FIG. 10 is a diagram showing magnetic transfer in the present embodiment.

FIG. 11 is a diagram showing a state during magnetization processing in the present embodiment.

FIG. 12 is a diagram showing a flowchart of a magnetic recording medium manufacturing process in the present embodiment.

FIG. 13 is a diagram showing a defect inspection device according to the present embodiment.

FIG. 14 is a diagram showing a defect inspection result in a step ST2 in the present embodiment.

FIG. 15 is a diagram showing a defect inspection result in the process of ST4 in the present embodiment.

FIG. 16 is a diagram showing a flowchart of a process of discriminating a defect caused by magnetic transfer in the present embodiment.

FIG. 17 is a diagram showing barycentric positions of various defects when 20 measurements are continuously performed on the same magnetic recording medium according to the present embodiment.

FIG. 18 is a result of listing defects having a rotational phase shift amount of 10 ° or less and a positional shift amount of 0.5 mm or less among the defects detected by the specular reflection light receiving element R in the present embodiment.

FIG. 19 is a diagram showing a result of subtraction according to the present embodiment.

FIG. 20 is a diagram showing a relationship between an output V of a dent defect detected by a specular reflection light receiving element R and a distance d between the magnetic recording medium 1 and a head in the present embodiment.

FIG. 21 is a diagram showing the results of observing the surface of a magnetic recording medium after conventional magnetic transfer.

FIG. 22 is a sectional view of a depressed portion of a conventional magnetic recording medium.

FIG. 23 is a diagram showing a result of optically measuring the state of protrusions on the surface of the entire magnetic recording medium after magnetic transfer is performed by a conventional magnetic transfer method.

[Explanation of symbols]

ST1 Magnetic recording medium manufacturing process ST2 Step of inspecting defects on the surface of the magnetic recording medium ST3 Magnetic transfer process ST4 Step of inspecting defects on the surface of the magnetic recording medium ST5 Step of discriminating defects caused by magnetic transfer

Continuation of the front page (56) Reference JP 2001-351231 (JP, A) JP 2002-269739 (JP, A) JP 2002-25054 (JP, A) JP 2001-184636 (JP, A) Open 2002-334430 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 5/84 G11B 5/86

Claims (6)

(57) [Claims] Against claim 1. A process for checking the possible defects originally present on the magnetic recording medium, the defect inspected magnetic recording medium, it is brought into close contact with the mask information carrier, the master information carrier A step of transferring a magnetic film pattern to the magnetic recording medium which has been subjected to the defect inspection, and a step of inspecting the magnetic recording medium after the transfer separated from the master information carrier for defects on the magnetic recording medium after the transfer. Determining the defect of the magnetic recording medium caused by the transferring step by comparing the defect inspection result of the magnetic recording medium after the transfer and the defect inspection result of the magnetic recording medium before the transfer. Only the defect inspection process for the magnetic recording medium before the transfer
Of the magnetic recording medium before transfer to the defect inspection means.
Defect inspection step for the magnetic recording medium after the transfer , including the operation of measuring the rotational phase
Of the magnetic recording medium after the transfer to the defect inspection means.
A process of determining a defect on the magnetic recording medium through the comparison , including a work of measuring a rotation phase
Is the deviation of the two rotational phases before the comparison work.
A defect inspection method for a magnetic recording medium, characterized in that it includes a work of correcting the defect. 2. The defect inspection method for a magnetic recording medium according to claim 1 , wherein light is applied to the magnetic recording medium in the correction of the rotational phase.
Detection of specular reflection light from the magnetic recording medium when irradiated
A defect inspection method for a magnetic recording medium, comprising : correcting a rotational phase of a defect detected based on the above . 3. The defect inspection method for a magnetic recording medium according to claim 1 , wherein light is applied to the magnetic recording medium in the correction of the rotational phase.
For detection of scattered light from the magnetic recording medium when irradiated
A defect inspection method for a magnetic recording medium, characterized in that the rotational phase of a defect detected based on the correction is performed . 4. The defect inspection method for a magnetic recording medium according to claim 1 , wherein light is applied to the magnetic recording medium in the correction of the rotational phase.
Detection of specularly reflected light from the magnetic recording medium when irradiated
Or the rotational phase of a defect detected based on the detection of scattered light
Correction is performed and the specular reflection light is detected.
A defect inspection method for a magnetic recording medium, characterized by giving priority to rotational phase correction of a known defect. 5. The defect inspection method for a magnetic recording medium according to claim 1, wherein the defect inspection step for the magnetic recording medium before transfer is the magnetic recording medium before transfer. Extract the location information of the above defect
In the defect inspection process for the magnetic recording medium after transfer, the position information of the defect on the magnetic recording medium after transfer is extracted.
Is intended to output a defect determination process on the magnetic recording medium through the comparison, the position information of the defect with a magnetic recording medium before the transfer
And position information of defects on the magnetic recording medium after the transfer
If it is the same, the magnetic recording medium is
If there is a defect, it is determined that there is no defect.
Defect inspection of magnetic recording medium characterized by
Method. 6. The defect inspection method for a magnetic recording medium according to claim 5, wherein the entire area of the magnetic recording medium is divided into a large number of minute units.
When defects are continuously identified over multiple areas
Treats the continuous unit areas as one area.
The center of gravity of the deemed region or its vicinity as a defect.
Of magnetic recording medium characterized by using position information of
Inspection method.