JPH10214421A - Method for specifying/analyzing faulty position on magnetic recording medium and manufacture of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve yield of disk manufacture after observing a fault and analyzing an occurrence cause by writing or erasing the magnetic data in at least two parts or above on a medium surface, performing the marking and specifying its position based on two part positions when a magnetic minute fault is detected. SOLUTION: An index pattern α is written in the position of a radius r+a over a nearly whole periphery. The index pattern is written in a sector existing on the position on the same radius as the minute fault A and different from it, and the marking B is performed. When the sector that the minute fault A exists is separated by (b) sectors from the sector of the marking B, the position of the marking B becomes (r, s+b). By erasing the pattern of one pattern existing on the same sector as the minute fault A in the index pattern α, the marking C is performed, and its position (r+a, s) is obtained. The pattern of one sector existing on the same sector as the marking B in the index pattern αis erased, and the marking D (r+a, s+b) is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for specifying the location of a submicron-level minute defect generated on a magnetic recording medium used in a hard disk drive or the like, analyzing the cause of the occurrence, and analyzing the source by using this analysis method. The present invention relates to a method for manufacturing a magnetic recording medium capable of preventing the occurrence of similar defects by removing the cause of the generation of minute defects.

[0002]

2. Description of the Related Art Structural or magnetic defects may occur on the surface of a magnetic recording medium (disk) used in a hard disk device or the like due to a manufacturing process or a material component thereof. If a defect exists, data cannot be normally written, and the output of read data may be reduced. Therefore, in order to check for defects on the disk surface, for example, an abnormally high protrusion formed on the disk surface called "glide inspection" is detected, and an inspection for detecting a shape abnormality in the height direction of the disk, or a "search fire" An inspection called "inspection" is performed to detect a magnetic abnormality of a disk by reading and writing data. If the above inspection reveals a defect on the disk surface, it analyzes the cause of the defect, identifies where in the disk production process the defect occurred, and improves the process. It is necessary to plan. Conventionally, a defective disk is visually inspected to determine the position of the defect, and a differential interference microscope or 80
Using an optical microscope with a magnification of 0 or less, the shape of the defect,
The cause was determined from the size and distribution status.
However, since this determination is based on the appearance determination of the defect, there is a problem that an error occurs due to a difference in subjectivity and experience of the observer.

[0003]

In recent years, there has been a demand for a rapid increase in capacity and recording density of a disk, and the length per bit, which is the minimum basic unit at the time of data writing, has been correspondingly increased. It is getting shorter rapidly. When the recording density of the disk is low, that is, when the length per bit is large,
Defects that cause magnetic anomalies were also large (> about 5 μm), and could be adequately addressed by visual observation. In this case, the submicron-level minute defect, whose existence cannot be confirmed by the search fire inspection, was extremely small with respect to the area occupied by one bit. Did not become. However, when the length per bit is reduced to about 0.5 μm or less in accordance with the increase in recording density, submicron-level minute defects, which have not been a problem in the past, increase the area occupied per bit. It becomes relatively large and has been a problem as a defect that causes magnetic anomalies. Therefore, it has become necessary to analyze the causes of such minute defects on the submicron level. However, even if the presence of submicron-level microdefects can be confirmed by shortening the length per bit by search fire inspection, visual observation or observation using a differential interference microscope can cause defects. In addition to the analysis, it was difficult to identify its location. When a magnetic recording medium is mass-produced on a production line, if a defect cannot be sufficiently analyzed, a magnetic recording medium having a similar defect is manufactured, and the yield is greatly reduced.

Accordingly, an object of the present invention is to specify a location of a submicron level defect present on a disk surface, observe a minute defect, and present a method of analyzing the cause of the occurrence. The purpose of this method is to feed back the method to a disk manufacturing process to improve the yield of manufactured disks.

[0005]

In order to solve the above-mentioned problems, the present invention carries out a search fire inspection for writing and reading a recording pattern on a manufactured magnetic recording medium, and performs a magnetic recording medium magnetic recording. Detect small minute defects. When a magnetic minute defect is detected in the magnetic recording medium, magnetic data is written or erased in at least two places on the surface of the magnetic recording medium in order to identify the position of the minute defect on the surface of the magnetic recording medium. Apply marking. Next, the position of the minute defect is specified based on the marked position on the surface of the magnetic recording medium. When the position of the minute defect is specified, the minute defect is observed using an inspection means, and the cause of the minute defect is analyzed. The reason why the marking is performed in the present invention is that the analysis of the defect of the magnetic recording medium in which the minute defect is detected by the search fire inspection is performed by the inspection means at a stage different from that of the search fire inspection device. This is because it is necessary to move the magnetic recording medium from the inspection device to the inspection means, and during the movement, it becomes impossible to determine the position of the minute defect that cannot be seen.

[0006] It is desirable that marking is applied to at least three or more places. In addition, in order to easily identify the position of the minute defect, it is more preferable that the marking is performed on the remaining vertex positions of the virtual polygon having the minute defect as one vertex. Examples of virtual polygons include regular polygons such as squares and rectangles. In addition, the marked position on the surface of the magnetic recording medium can be visually confirmed by applying light.However, if a magnetic fluid is applied to the marking position, the marking position can be easily specified. Positioning at the time of observation is also easy.

An atomic force microscope is used as an inspection means for analyzing the cause of a minute defect whose position has been confirmed by the above method.
(AFM), a magnetic force microscope (MFM), an Auger electron spectrometer (AES), and a cross-sectional transmission electron microscope (cross-sectional TEM). A multifaceted analysis may be performed by combining these inspection means. Each of the above-mentioned inspection means is an instrument used for observation and analysis in a minute range. For example, it takes tens of minutes to several hours to observe a range of about several mm ² . Therefore, it takes a lot of time to observe the entire surface of the magnetic recording medium without specifying the position of the minute defect, identify the cause of the minute defect, and improve or change the manufacturing process or material of the magnetic recording medium. Can take days to weeks. Improvement of processes, etc.
If the manufacture of the magnetic recording medium is continued without making any changes, a magnetic recording medium having the same minute defect is manufactured, so that the yield decreases. Further, if the manufacture is interrupted, the production efficiency decreases. That is, it is very important to analyze the cause of the minute defect as soon as possible, and to remove the cause as soon as possible by improving or changing the process or the material. According to the present invention, by specifying the position of the minute defect, the observation time by various inspection means can be significantly reduced, and the cause of the occurrence can be analyzed.

Using the AFM and the MFM, the surface shape and magnetic force of a minute defect can be observed, and the cause of the defect can be analyzed. In this case, first, the surface morphology of the minute defect of the magnetic recording medium whose position is specified is observed by scanning the minute probe of the AFM. Next, the magnetic recording medium immediately above the magnetic recording medium observed by the AFM is scanned at a constant height along the surface shape of the magnetic recording medium using a magnetic probe of the MFM,
Observe the magnetic state of the microdefects, and from the observations obtained,
The cause of the defect may be analyzed. In addition, by using AES, it is possible to observe component defects of minute defects and analyze the cause of the defects. In this case, the minute defect of the magnetic recording medium whose position is specified is analyzed in the depth direction by AES, and the component configuration of the defective portion is observed. The obtained observation result can be used for analyzing the cause of the defect as described later. Further, it is possible to observe the structural defect of the minute defect using the cross-sectional TEM and analyze the cause of the defect. In this case, the minute defect of the magnetic recording medium whose position is specified can be analyzed in the cross-sectional direction by the cross-sectional TEM, and the structural cause of the defect can be analyzed.

In the manufacturing process of the magnetic recording medium, when a minute defect is detected, the inspection is performed by the above-mentioned method, and the cause of the minute defect is analyzed. The analyzed result is fed back to the manufacturing process of the magnetic recording medium, and the process or the material is improved or changed to eliminate the cause of the occurrence, and then the magnetic recording medium is manufactured. As a result, it is possible to prevent similar minute defects from occurring in the magnetic recording medium manufactured thereafter.

[0010]

According to the method for analyzing microdefects of a magnetic recording medium of the present invention, it is conventionally difficult to specify the position and / or analyze the cause. The cause can be specified efficiently in a short time. Further, by feeding back the microdefect analysis method of the present invention to the manufacturing process of the magnetic recording medium and removing its cause, the occurrence of the same microdefect can be prevented beforehand, and the yield can be improved.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A magnetic recording medium is generally manufactured by forming a NiP layer on a non-magnetic substrate as needed to form a medium substrate, and forming an underlayer, It is manufactured by sequentially laminating a magnetic layer, a carbon protective film, and a lubricating film. The underlayer and the like are not limited to those having a single-layer structure,
It also includes those having a multilayer structure.

It is desirable to perform a glide test on the obtained magnetic recording medium in advance, remove a magnetic recording medium having abnormally high protrusions, and then perform a search fire test. As a search fire inspection method, there is a method of writing and reading a signal for each track, measuring the output of a read signal, and then erasing the signal. Less than,
An example of a method for positioning a minute defect when a submicron-level minute defect is detected in the search fire inspection will be described. When a minute defect is detected, the position of the track where the minute defect exists is stored in the search fire inspector, and a search fire inspection is performed over the entire circumference of the magnetic recording medium to determine whether there is another minute defect. , It is desirable to perform positioning of the minute defect. When the output abnormality of the read signal is detected by the search fire inspection and the presence of the minute defect A is recognized, it is desirable to first erase the entire surface of the magnetic recording medium in order to remove the measurement noise. Next, one track is divided into a plurality of sectors, for example, 1024 sectors, and the recording pattern is written only in the sector including the minute defect A. When the position of the minute defect A is located at the position of the radius r and the sector s with the rotation center of the magnetic recording medium in the search fire inspection device as the origin, the position is defined as A (r, s).

In order to specify the position of the minute defect A, a plurality of markings are made on the magnetic recording medium in the following manner. In the following, an embodiment in which marking 3 is performed on a magnetic recording medium will be described. First, the minute defect A
Radius r + a of the magnetic recording medium
The index pattern α is written almost all around the position (see FIG. 1). Next, an index pattern is written in one sector at a different position on the same radius as the minute defect A, and marking B is performed (see FIG. 1). Small defect A
And the sector with marking B is b
Assuming that the sectors are apart, the position of marking B is
It is indicated by (r, s + b). Next, marking C is performed by erasing the pattern of one sector on the same sector as the minute defect A in the index pattern α (see FIG. 1). The position of the marking C is indicated by (r + a, s). Further, marking D is performed by deleting the pattern of one sector on the same sector as marking B in the index pattern α (see FIG. 1). The position of the marking D is indicated by (r + a, s + b).

The magnetic recording medium having the markings B, C, and D is taken out of the search fire inspector, and the positions of the markings B, C, and D are visualized. When light is applied to the magnetic recording medium, the reflection position of the marking portion differs from that of other portions. Therefore, by applying a magnetic fluid to that portion, the marking position can be sufficiently confirmed visually. It is a suspension in which ferromagnetic solid fine particles are stabilized as a magnetic fluid in a base liquid using a surfactant. When the magnetic fluid is applied, the magnetic material selectively aggregates only at the location of the large leakage magnetic field on the surface of the magnetic recording medium, that is, only at the recording reversal portion, so that the visualization becomes easy. From the positions of the visualized markings B, C and D, the minute defect A
Identify the location of Note that the specified position may deviate from the position of the micro defect A by a maximum of about 200 μm because the length of the sector changes by a maximum of about 200 μm depending on the radius.
Since it is 8 μm, even if the position is displaced, the microdefect A can be reliably observed by performing scanning several times.

The magnetic recording medium in which the position of the minute defect A is specified is transferred to the inspection means, the inspection means is aligned so that the minute defect A can be observed, the observation is executed, and the cause is analyzed from the result. The observation by the inspection means and the analysis of the cause thereof will be described in Examples.

[0016] By analyzing the above observation results and identifying the cause of the occurrence of the microdefect, the manufacturing process, manufacturing equipment, material, atmosphere, cleaning method, temperature, etc., which caused the defect, are improved or changed. What is necessary is just to remove the cause of occurrence.

[0017]

EXAMPLE A magnetic recording medium having a minute defect was observed by each inspection means, and a typical cause of occurrence was analyzed.

Small defect A positioned by the above method
Was measured by AFM / MFM. First, the measurement principle will be described with reference to FIG. The arrows in the figure are
The direction of magnetization is shown. First, AFM probe (10)
Is scanned on the position where the minute defect A exists on the positioned magnetic recording medium (12), and the surface shape of the minute defect A portion is measured. Next, the magnetic recording medium measured by AFM
The MFM probe (14) is used to scan the surface immediately above the surface shape of (12) at a constant height, measure the distribution of magnetic force, and analyze the observation result.

FIG. 3A is an image obtained by observing the surface shape of a magnetic recording medium including a minute defect A by AFM.
(b) is an image obtained by observing the magnetic force of the same portion by MFM. It can be seen that there is a portion having a different surface shape of about 2 μm × 1 μm substantially at the center of FIG. This is the minute defect A. Referring to FIG. 3B in which this part is observed by MFM, it can be confirmed that there is a missing part (indicated by an arrow in the figure) where writing has not been performed normally over several bits.

FIG. 3C shows a sectional profile of the small defect A portion. According to this profile, the shape of this defect is a vertically steep shape, a height of about 18 nm,
It was found that the width was about 2 μm.

Next, as a result of analyzing the micro defect A in the depth direction by AES, elements such as iron, nickel and chromium constituting stainless steel were detected from the surface of the defect portion. In addition, a base layer and a NiP layer were detected from beneath the foreign substance mainly composed of stainless steel. That is,
From the results of the AES analysis, it was found that the minute defect A was caused by adhesion of stainless steel in the vacuum chamber as a foreign substance when the magnetic layer was formed. The cause of this problem can be solved by replacing the stainless steel in the vacuum chamber where the magnetic layer is formed, or by shielding the stainless steel without exposing the stainless steel to the inside of the chamber. it can.

Next, an embodiment in which a minute defect smaller than 1 μm is analyzed will be described. In this embodiment, AFM, three-dimensional AFM and MFM are used for observation of minute defects. FIGS. 4A, 4B, and 4C show images analyzed by the respective inspection means in order. As can be seen from FIG. 4B, the minute defect has a projection shape with a height of about 20 nm and a width of 0.5 μm. Such a minute defect of 1 μm or less cannot be observed with a differential interference microscope as described above. The position of such a minute defect of 1 μm or less is first specified by performing the marking. When the minute defect portion was analyzed in the depth direction by using AES, a normal film configuration including a carbon protective film, a magnetic layer, and a Cr underlayer was observed in order from the surface. It was found that carbon that should not exist originally exists at the interface with the layer.
FIG. 5A shows an AES image of a normal portion having no defect, FIG.
(b) is an AES image of a minute defect portion. Referring to FIG. 5 (a), only Cr, Ni and P are present in the normal part, whereas carbon, chlorine,
Oxygen has been detected. For reference, mapping measurement by AES analysis of carbon present in the minute defect portion was performed. As a result, as shown in FIG. 6, the shape corresponds to the shape of the AFM image in FIG. 4A, and it is clear that a large amount of carbon is present in the minute defect.

Carbon, from between the NiP layer and the Cr underlayer,
It is considered that the cause of the minute defects due to the detection of chlorine and oxygen is that the detergent is not sufficiently washed away in the cleaning step of the medium substrate having the NiP layer laminated on the substrate. To solve this cause, the components of the detergent, the cleaning intensity, the time, the method, etc. may be changed.

Next, FIG. 7A shows a search fire inspection.
The cause of the defect of the magnetic recording medium in which the defect shown in FIG. Referring to FIG. 7A, it can be seen that the signal intensity of only one bit indicated by the arrow in the drawing in the reproduced output waveform of the search fire test is greatly reduced (a so-called missing pulse). After DC erasing of this portion, the signal intensity of the reproduced output waveform was measured in the same manner. As shown in FIG. 7B, the portion indicated by the arrow in the figure was not sufficiently erased. , A signal is detected (so-called extra pulse). This portion was similarly located by marking, and then observed using AFM and MFM. FIG. 8 shows the results. 8A shows an AFM image, FIG. 8B shows a cross-sectional profile of the AFM image, and FIG. 8C shows an MFM image. According to AFM observation (FIGS. 8 (a) and 8 (b)), the minute defect has a height of about 12 nm and a width of about 0.8 μm.
It can be seen that the bulge of the line exists linearly. This linear defect also appears in the MFM image similarly, and it is clear that the magnetic state is different from that of the surrounding part. This result is the result of the above-described search fire inspection analysis (FIG. 7).
(a) and (b)), which revealed that this linear defect was a combination of shape abnormality and magnetic abnormality. The reason that such a shape abnormality and a magnetic abnormality can be simultaneously observed on the same tool is that a defect can be inspected using the AFM and the MFM after the position is specified by the marking. Next, the cause of the linear defect was analyzed. In the MFM image of the magnetization reversal portion shown in FIG. 8C, the magnetization reversal image of the defect portion is observed with substantially the same contrast as the magnetization reversal images before and after the defect portion. It is not considered to be caused by the lack. Therefore, this defective portion is cross-sectioned by TEM.
Observed using. FIG. 9 shows a cross-sectional TEM image including the linear defect portion. Referring to FIG. 9, this linear defect is Ni Ni
It can be seen that the P layer is partially swollen. This N
When the cause of the linear swelling of the iP layer is considered from FIG. 9, it is considered that the cause of the linear defect occurring in the substrate itself is inherent, and this is caused by the linear swelling during each subsequent film forming process. Can be In other words, in the mirror finishing process of the surface performed in the substrate manufacturing process, a morphologically flat but linear distortion is formed inside, and this internal distortion is caused by the substrate heating in the film forming process. When released during the process, it is considered to have swelled linearly. The fact that the direction of the linear defect coincides with the processing direction at the time of mirror finishing in the substrate manufacturing process also indicates that this analysis is correct.

In order to prevent the generation of this minute linear defect,
It can be seen that the cleaning strength, the type of detergent, the cleaning time, the cleaning direction, and the like should be improved in the mirror finishing process of the substrate.

In the above embodiment, the observation by each inspection means and the analysis of the cause were performed.
Not limited to M / MFM, AES, section TES, TXR
F (total reflection X-ray fluorescence spectrometer), FT-IR (Fourier transform infrared spectroscopy), XPS (X-ray photoelectron spectroscopy), or a combination of these inspection means Observation may be performed to analyze the cause of occurrence. Also in these cases, when the cause of occurrence is specified, the manufacturing process or the material is improved to eliminate the cause of occurrence and suppress the occurrence of the same minute defect.

[Brief description of the drawings]

FIG. 1 shows markings B, C and D for identifying a micro defect A
It is a figure explaining the state where it performed.

FIG. 2 is a diagram illustrating an observation state by AFM / MFM.

FIGS. 3A and 3B are observation diagrams of minute defects existing on a magnetic recording medium, wherein FIG. 3A is an AFM image, FIG. 3B is an MFM image, and FIG.

4A and 4B are observation diagrams of a minute defect existing on a magnetic recording medium, wherein FIG. 4A is an AFM image, FIG. 4B is a three-dimensional AFM image, and FIG. 4C is an MFM image.

FIG. 5A is an AES image of a normal portion having no defect,
(b) is a diagram showing an AES image of a minute defect portion.

FIG. 6 is a diagram showing a result of mapping measurement of carbon present in a minute defect portion by AES analysis.

7A is a diagram showing a reproduction output waveform of a search fire inspection of a minute defect portion, and FIG. 7B is a diagram showing a reproduction output waveform after DC erasure.

FIGS. 8A and 8B are observation diagrams of minute linear defects existing on a magnetic recording medium, wherein FIG. 8A is an AFM image, FIG. 8B is a cross-sectional profile image, and FIG. 8C is an MFM image.

FIG. 9 is a cross-sectional TEM image of a linear defect portion.

[Explanation of symbols]

 (10) AFM probe (12) Magnetic recording medium (14) MFM probe

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiko Yasui 1-47, Shikitsuhigashi, Namiwa-ku, Osaka-shi, Osaka Prefecture Inside Kubota Corporation (72) Inventor Makoto Maeda 1 Shikitsuhigashi, Namiwa-ku, Osaka-shi, Osaka No. 2-47 Kubota Corporation

Claims (7)

[Claims] 1. A recording pattern is written and read to detect a magnetic minute defect existing on a magnetic recording medium, and when the minute defect is detected, a position of the minute defect is specified on the magnetic recording medium. For this purpose, marking is performed by writing or erasing magnetic data on at least two places on the surface of the magnetic recording medium, and the position of the minute defect is specified based on the marked position on the surface of the magnetic recording medium. Method for identifying the position of a defect in a magnetic recording medium. 2. A recording pattern is written and read to detect a magnetic minute defect existing on a magnetic recording medium, and when the minute defect is detected, a position of the minute defect is specified on the magnetic recording medium. For this purpose, marking is performed by writing or erasing magnetic data on at least two places on the surface of the magnetic recording medium, specifying the position of the minute defect with reference to the marked position on the surface of the magnetic recording medium, and checking the inspection means. A defect analysis method for a magnetic recording medium in which micro defects are observed by using the method and the cause of the micro defects is analyzed. 3. The defect analysis method for a magnetic recording medium according to claim 2, wherein the marking is performed on at least three or more locations on the magnetic recording medium. 4. When a minute defect is detected, one track is divided into a plurality of sectors, a recording pattern is written only in a sector including the minute defect A, and at a position radially away from the minute defect A by a predetermined distance a. , An index pattern is written over substantially the entire circumference, and an index pattern is written in one sector located at a position separated by a predetermined sector b on the same radius as the minute defect A to perform marking B. The marking C is performed by erasing a pattern of one sector on the same sector as A, and the marking D is performed by erasing a pattern of one sector on the same sector as the marking B in the index pattern α. 3. The defect analysis method for a magnetic recording medium according to item 3. 5. The defect analysis method for a magnetic recording medium according to claim 2, wherein the marking is performed at a position of a remaining vertex of the virtual polygon having a minute defect as one vertex. 6. The defect analysis method for a magnetic recording medium according to claim 2, wherein a magnetic fluid is applied to a position on the surface of the magnetic recording medium where the marking is made, and the marking position is visualized. . 7. A medium substrate is formed by forming a NiP layer on a non-magnetic substrate as required, and an underlayer, a magnetic layer, a protective film, and a lubricating film are sequentially laminated on the medium substrate. 3. A method of manufacturing a magnetic recording medium formed by a step of: detecting a minute defect from the manufactured magnetic recording medium.
7. A magnetic recording method for manufacturing a magnetic recording medium, comprising analyzing a cause of occurrence of a minute defect in a magnetic recording medium by using the defect analysis method according to claim 6 and removing the cause of the generation during a manufacturing process. The method of manufacturing the medium.