JP3481864B2 - Magnetic disk defect inspection method and magnetic disk defect inspection device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk defect inspection method and a magnetic disk defect inspection apparatus, and more particularly, to a magnetic disk defect inspection method capable of improving the throughput of high density recording magnetic disk defect inspection. And a defect inspection device.

[0002]

2. Description of the Related Art A hard disk device (HDD), which is one of the external storage devices of a computer, uses a hard magnetic disk as its recording medium. This magnetic disk is manufactured by applying a magnetic film on the surface of a disk made of aluminum or glass as a substrate and coating a protective film on the magnetic film. It is desirable that the surface coated with the magnetic film and the protective film be a smooth flat surface with as few irregularities as protrusions.
In addition, this is required to have good recording performance in the electrical sense. The smoothness (protrusion amount and unevenness) is inspected by a glide tester, and the recording performance is inspected by a certifier.

A high density recording magnetic disk has a high number of tracks and a high recording density, and as the recording density of the magnetic disk is improved, the inspection efficiency of the magnetic disk must be lowered. Therefore, in recent years, in order to improve the yield and the test efficiency by the glide tester, an optical surface defect inspection process is provided between the burnishing process and the glide test process. A glide test has been performed after inspecting a defect and removing a defective disk that surely causes a defect.

FIG. 8 is an outline of a conventional magnetic disk manufacturing and inspection process. First, there is a magnetic film forming step in which a magnetic film and a protective film are formed on a disk such as aluminum by coating. Next, in order to reduce the unevenness of the surface of the disk on which the magnetic film and the protective film are formed (so-called magnetic disk) as much as possible,
There is a burnish process. In this step, the projections on the surface are scraped off and the surface is made flat. Then, in the next surface defect inspection step, the defect inspection of the disk surface is performed. Here, the disk having a problematic defect above a predetermined standard is eliminated, and then the glide test process is started. In this step, the glide test head inspects the presence and number of protrusions. The glide test process is
There is a burnishing process for a mild burnishing inside.

Therefore, as a result of the inspection here, when the predetermined number or more of protrusions still remain, the inspection result is rejected (NG), and the process returns to the burnishing process in the glide test process. Burnish is performed here. Go through these two burnishes or more. Then, the magnetic disk that passed (G) in the glide test process enters the next certifying process. An invention in which the glide test and the burnish are performed in the same device in the glide test step is filed as USP 5,423,111 by the applicant.

The above-mentioned surface defect inspection step is mainly to increase the yield by the glide tester, and the magnetic disk having a defect which surely fails in the glide test step is excluded by the surface inspection. It is provided so that it will not be carried into the glide test process. As a result, it is possible to reduce the number of failed disks in the glide test process and improve the test efficiency. However, coupled with the improvement of the manufacturing accuracy of the magnetic disk, only a few of them actually fail the surface defect inspection process these days. Therefore, in the high density recording magnetic disk, even if the surface defect inspection step is provided as described above, the inspection throughput (inspection efficiency) per magnetic disk is not so much improved. An object of the present invention is to solve the above-mentioned problems of the conventional technique, and to provide a magnetic disk defect inspection method capable of improving the throughput of the magnetic disk defect inspection of high density recording. Another object of the present invention is to provide a magnetic disk defect inspection apparatus capable of improving the throughput of high density recording magnetic disk defect inspection.

[0007]

The feature of the magnetic disk defect inspection method of the present invention for achieving such an object is that the defect inspection of the magnetic disk is optically performed, and the defect size and the continuity are recorded as defect data. Characteristics, number, and defect position are detected with higher accuracy than the defect inspection by the electrical characteristic inspection in certification, and problems in electrical characteristics based on the defect data obtained in this surface defect inspection step. First, a first magnetic disk that passes the certification test, and a second magnetic disk that must be further subjected to the certification test to determine whether or not the electrical characteristics pose a problem, and the certification test. It is a classifier that classifies it as a third magnetic disk that causes a problem in electrical characteristics and does not pass the judgment without needing to make a judgment. Have bets, the first magnetic disk is as acceptable, in which a second magnetic disk to the target of certification testing. As a result, the efficiency of certification can be improved. Further, the magnetic disk defect inspection apparatus of the present invention comprises an inspection means for realizing the surface defect inspection step and a classification means for realizing the classification step.

[0008]

The major difference between the optical surface defect inspection and the certification inspection is that the former optically detects the surface shape and state of the magnetic disk, and the latter is magnetic. The point is that a defect is electrically detected using the head. Therefore, the pass / fail of the former does not always match the pass / fail of the electrical inspection. However, by increasing the accuracy of optical surface inspection and adopting a high standard for passing magnetic disks, it is not possible to select a magnetic disk that can pass electrical inspection without fail by optical inspection. it can. The selection is made in the present invention. Here, the defect size, continuity, number, and defect position are used as the reference. That is, in the magnetic disk defect inspection method and the defect inspection apparatus as described above, the magnetic disk is classified into the above-mentioned first to third types of magnetic disks. Therefore, in the surface defect inspection process, defect size, continuity, number, and defect position are obtained as defect data. In particular, the size is sampled under stricter conditions than the conventional surface defect inspection process of FIG. This invention, as mentioned above, is the first surface
Subsequent inspection according to the defect data obtained in the defect inspection process
The first magnetic disk that passes the process and the subsequent inspection process
The third magnetic disk that fails the test, and the pass / fail status is uncertain
It is classified into a fixed second magnetic disk. Improved manufacturing technology
The number of magnetic disks that passed
The higher the value, the more magnetic disks will pass. Conventional
In the inspection of the magnetic disk of
Since the target is a magnetic disk,
However, in the present invention, the subsequent inspection process does not pass or fail.
Only the definite second magnetic disk should be inspected
So inspection throughput is high even in high yield conditions
Test throughput as a whole, without degrading
Improves.

In the surface defect inspection step, the magnetic disks to be inspected are classified into three as described above, so that the magnetic disks that pass without the glide test or certify are determined at this stage. As described above, in view of the current situation that most of the magnetic disks that pass the defective magnetic disk pass, the highly accurate surface defect inspection as described above is performed, and the defective data also passes the electrical characteristics. It is possible to obtain a passing magnetic disk having a defect of about 30% or more as a magnetic disk having a defect obtained by such an optical inspection. As a result, the magnetic disk to be inspected for the glide test or certifying can be reduced to 70% or less. As a result, the target of defect inspection of the conventional magnetic disk becomes 70% or less, and the efficiency of the magnetic disk defect inspection can be improved as a whole.

According to another aspect of the invention, there is provided a surface defect inspection method in which, in addition to the above-mentioned structure, a second defect classified by a classification step is further included.
The defect data output step of outputting at least the defect position data of the magnetic disk and the identification information for identifying the second magnetic disk as defect information for use in the subsequent inspection step. Similarly,
The inspection apparatus of the present invention comprises a defect data output means for implementing the above defect data output step. In this way, by outputting the defect data of the second magnetic disk for the subsequent inspection process, the defects output during the subsequent inspection process, for example, the defect inspection in the glide test or the certify process. Is inspected centering on a certain position, and is not inspected for the remaining positions,
Even if it is inspected, it can be done roughly. As a result, the inspection throughput for one magnetic disk can be further improved.

By the way, the magnetic disk actually used can be used in many cases by an alternative track, an alternative sector, 1-bit error correction, etc., even if it has some defects. Therefore, it is important to classify the second magnetic disk among the above three classifications. It is difficult to separate the second magnetic disk from the third magnetic disk and classify them accurately with only the size and position of the defect and the number of defects. As the number of the third magnetic disks increases, the yield decreases and the number of wasted magnetic disks increases. Even if the inspection efficiency is improved, it is a problem that the yield is reduced. Therefore, in order to improve the classification accuracy of the second magnetic disk and the third magnetic disk, the continuity of the defects and the types of the defects are further inspected here.

Explaining the reason therefor, in the optical defect inspection, the surface state of the magnetic disk as shown in FIGS. 7A and 7B as a partial sectional view is detected as a defect. FIG. 7A shows a disk substrate (a substrate including a plating layer) itself having a shallow depression usually called a dimple, on which a magnetic film is formed. When a magnetic film having such a shallow depression is detected as a defect, the data output level is somewhat lowered, but there are many cases where data read / write can be guaranteed. On the other hand, (b)
Is a defect when a deep hole, usually called a pit, is present in the disk substrate itself, and a magnetic film is formed thereon. In the case of such a deep hole, the formation layer of the magnetic film itself becomes thin, or the magnetic film is almost not formed on the surface. In this case, data read / write is often not guaranteed.

Therefore, the accuracy in the optical defect inspection process is increased, and in addition to the relationship between the size and the number of defect data, the continuity of defects and the type data are collected.
That is, in order to more accurately classify the second and third discs from the discs that failed the optical defect inspection,
The former magnetic disk having a shallow dent defect called a dimple as shown in FIG. 7A is excluded from the acceptance / rejection criterion. Therefore, the continuity and type of defects are referred to. In the optical defect inspection, the dimples are relatively short in length and often appear as defects having a certain area. Such a defect is excluded from the defect data for classifying the second disc and the third disc, and it is determined whether or not the defect is a problem in the certification in the subsequent process. Therefore, this type of defect becomes an undetermined defect described later.

On the other hand, pits are not continuous and appear as short single defects. Read data from this pit
A disk having a deep hole defect whose writing is not guaranteed is equal to or larger than a reference number is classified as a third disk. Of course, in terms of continuity and type, a disc having a predetermined number of long defects that are usually rejected is also extracted as the third disc. In addition, defects that would make the alternative track and the alternative sector impossible are also classified and extracted in the third disk. For these third classified disks, classification conditions are determined by repeating certification on an actual magnetic disk having this type of defect. Specifically, as a defect in which data read / write is not guaranteed, the number of pit defects that cannot be corrected in 1 bit, the position of the defect, and the continuity of the pit defect make it impossible to find a substitute track or a substitute sector. The number of pit defects exceeds the number of normal alternative tracks or alternative sectors, and the length of continuity defects is greater than the standard value, or is longer than a specified length. A certain amount of continuity defects. A disc having these is determined to be the third disc. The rest is the second disc. Note that long continuous defects include groove-shaped scratches and the like.

By the way, when the inspection accuracy is increased in the optical surface inspection, the number of the second and third magnetic disks that necessarily fail the first pass magnetic disk increases, and It becomes difficult to distinguish between the second magnetic disk and the third magnetic disk, but here, in addition to the defect of the condition that normally fails in certification, as described above, due to the pit defect, The three discs are further classified. Depending on the number, size, and continuity of the pits, by extracting the third failing magnetic disk from the failing disks in the optical defect inspection, it is possible to improve the classification accuracy with the rest as the second disk.
By subjecting the disc classified into the second disc to the certification test, it is possible to improve the inspection efficiency as a whole. In addition, in FIG. 7, 11 is
A disk substrate, 12 is a plated layer of nickel alloy or the like, 13 is a magnetic film sputtering layer, and 14 is a lubricating layer.

The above is a description of the depressions and holes, but the same applies to the protrusions. For the gentle protrusions called mounds, since the magnetic film is formed relatively thick along the mounds, the data There are many cases in which reading / writing can be guaranteed, but with the protrusions called bumps, the magnetic layer itself is hardly broken by the protrusions.
It is thin. Therefore, in many cases, data read / write is not guaranteed. In the same way of thinking as the case of the above-mentioned pit based on the latter in which the reading / writing of data is not guaranteed, according to the number, size, and continuity of the bumps, as in the case described above, the second test subject to the certification test is performed. The magnetic disk and the third rejected magnetic disk can be accurately classified. The mound also becomes an undetermined defect described later. In the current surface defect inspection, it is possible to detect the types of defects such as the aforementioned dimples and pits, the mounds and bumps, and the scratches on the magnetic disk. By adding such defect types, the third magnetic disk is accurately classified from the second magnetic disk except for undetermined defects before the electrical characteristic inspection in relation to the size, continuity, and type. It will be possible. This makes it possible to determine the second magnetic disk to be the conventional inspection target.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, A is a surface defect inspection process, which corresponds to the surface defect inspection process in FIG. 8. This process includes an inspection process A-1 and a defect data division process A-. 2, and includes a pass disk determination step A-3 and a pass magnetic disk sorting step A-4 for classifying the inspected magnetic disks as first, second, and third magnetic disks. The inspection step A-1 is a step of obtaining defect size, continuity, number, type, and defect position as defect data. Defect data classification process A-2
It is highly possible that the read / write of data is electrically guaranteed from the obtained defect data, which is an undetermined defect as a defect from the viewpoint of electrical characteristic inspection in certification (hereinafter, an undetermined defect. Data) and the definite defect data, which is regarded as a reliable defect in electrical characteristics.

Definite defects and undetermined defects are guaranteed to read / write data in the types and positions of defects such as dimples and pits, mounds and bumps, and scratches, and the continuous length, or a combination thereof. It is determined by whether or not the defect is not made. Among the defects, a defect in which data reading / writing is not guaranteed is a definite defect. Defects other than this become undetermined defects. Definite defects are, specifically,
Regardless of the position of the defect or defect, which is not related to the pit or dimple, the size of the pit or dimple whose size cannot be corrected by 1 bit, and the data read / write is not guaranteed due to the relationship between the defect position and its length. , Continuous defects of a certain length or more. Read such data /
Defects for which writing is not guaranteed (confirmed defects) are as follows. For each defect that has actually occurred, data is actually written by a certifier and electrically read out many times.
As a result of confirming whether the reading / writing of data is guaranteed, the selection condition of the definite defect is determined.

In the pass disk judging step A-3, a magnetic disk which does not cause a problem in terms of electric characteristics and which is acceptable in the certification inspection is judged based on the defect data firstly collected, and no electric characteristic inspection is carried out. The first magnetic disk that passes is determined. This disk has, for example, a number of defects equal to or less than a predetermined number, the defects are not concentrated on a specific track or sector more than a predetermined number, and the defects guarantee data read / write. This is the case when it is a defect. Regarding the defects that guarantee the reading / writing of data,
Actually write the data with each certifier,
As a result of checking whether or not data reading / writing is guaranteed by conducting an electrically reading test many times, the selection condition for this is determined. The next failing magnetic disk partitioning step A-4 is a defective data partitioning step A-2 for the magnetic disk that failed in the passing disk judging step A-3.
The third magnetic disk whose quality cannot be guaranteed based on the confirmed defect data of No. 3 is extracted as a certain fail disk, and the remaining one is the second of the certification test target (further quality inspection target). A magnetic disk is separated from a rejected magnetic disk and is classified as a re-inspection disk.

Here, the surely rejected disc is determined by the definite defect, its position, occurrence and the like. In particular, the position in this case depends on how many definite defects are present in the same track or sector and how consecutive they are. Further, when the number of confirmed defects exceeds a certain number, the alternative track or the alternative sector becomes impossible. Therefore, it is determined whether or not the number is a predetermined number or more. Further, it is also determined by how many continuous defects have a length larger than the reference value, and the position thereof is such that an alternative track or an alternative sector is impossible. Further, it is determined by the degree of concentration of a continuous defect having a predetermined length or more on a specific track or sector. Now, in the figure, B is a glide test step, which corresponds to the glide test step in FIG. 8, and is the second magnetic disk (re-inspection disk) described above.
Glide test is performed on all tracks (entire surface).
C is a certifying step, which corresponds to the certifying step in FIG. 8, and which has passed in the glide test step B, all tracks (entire surface) of the second magnetic disk (re-inspection disk). ) About the certification test.

FIG. 2 shows an embodiment in which the defect data output step is added last in the surface inspection step of the embodiment of FIG. This last added step will be described. In the surface defect inspection step A of FIG. 1, after the failed magnetic disk sorting step A-4, the identification number and the defect of the second magnetic disk (re-inspected disk) are further added. Data (defect data before extracting fixed defect data) and F
A defect data output step A-5 for outputting to a recording medium such as D (floppy disk) is provided. In the defect data output step A-5, the defect data including the undetermined defect data before being separated by the defect data dividing step A-2 and the confirmed data is stored in the FD as the defect data to be used in the subsequent inspection step. It is output together with the identification number of the second magnetic disk. In this case, the undetermined defect data and the confirmed data may be stored separately in the FD.

The defect data output to the recording medium may include at least defect position data on the disk, or may be only this position data. The identification number of the magnetic disk is a management number managed by the manufacturing lot number of the magnetic disk, the disk cassette number of the cassette in which this magnetic disk is loaded, and the numerical value of the loading position of the disk cassette (for example, the number from the front). Is. The lot number and the disc cassette number are specified and determined by attaching a barcode label or the like on the side surface of the disc cassette. This bar code label can be obtained by optically reading it by the magnetic disk defect inspection device. Further, the magnetic disk loading position of the disk cassette is controlled by this number because the order in which it is sequentially loaded by the handling arm is managed.

The glide test step B of FIG. 2 receives the re-inspection disk (second magnetic disk) obtained after the failing magnetic disk sorting step A-4 as in the embodiment of FIG. The method of inspecting the disc is different from that of the embodiment shown in FIG. The defect inspection of the entire surface of the disk to be inspected as described in the embodiment of FIG. 1 is not performed.
Here, the position at which the defect data output in the defect data output step A-5 is received and a defect is detected based on this defect data, or the position before or after the defect position around the position or the defective sector, Or just do a glide test on the defective track. This enables efficient inspection. Further, the defect data obtained as a result of the test here is output to the FD for use in the subsequent inspection process. This point is different from that of FIG.

Specifically, in the glide test process B,
The FD obtained in the defect data output step A-5
To read the defect inspection data for the second magnetic disk, and further read the identification number of the disk to be inspected from the bar code of the disk cassette and the ejection position from the cassette. Then, according to the position data in the defect data, a detailed glide test is performed at any of the position, the position before and after the position, the track including the defect position, and the sector including the position. Rejected magnetic disks are burnished in the glide test process and re-inspected.
Then, when the passed magnetic disk is loaded into the disc cassette, the bar code label on the side of the disc cassette is read, an identification number is generated from the cassette loading position, and the first identification number is changed to a new identification number. Rewrite and write in the FD. At this time, the lot numbers of the disc cassettes are the same unless there are special circumstances.

In the next certifying step C, as in the case of the glide test step B, the defect data detected in the previous glide test step B is read from the FD,
The certification inspection is performed on the position where a defect is detected based on this defect data, before and after the position around this position, on the defective sector, or on the defective track. Specifically, in the certifying step C, the defect inspection data is read from the FD of the defect data output in the glide test step B, and the identification number of the disc to be inspected is determined from the barcode of the disc cassette and the ejection position from the cassette. In accordance with the position data in the read data, the detailed certify test is performed at the front and rear positions or in the sectors and tracks as described above. As a result, magnetic disks that fail this inspection are discarded.

FIG. 3 shows a flowchart of the processing of the surface defect inspection step in the embodiment of FIGS. To explain from the processing flow of the embodiment of FIG. 1, for a magnetic disk that has undergone the burnishing process, the bar code is read from the bar code label of the disk cassette and stored in the memory (step 101), and the magnetic disk to be inspected is selected. It is set on the inspection table (actually, the magnetic disk is chucked on the spindle, step 102), and the surface defect inspection is started (step 103). Then, the signal level of the detected defect and its position on the disk are sampled (step 104), and the level data and position data of the defect signal are stored in the memory (step 105). Then, the size and continuity of the defect are determined based on the signal level data and the position data of the defect, and these data are generated and stored in the memory (step 106). Further, the type of the defect is determined based on the continuity and the difference between the two types of light receiving detectors described later in the embodiment of FIG. 6 (step 107). Then, undetermined defects are excluded from the defect size, continuity, and type to determine the deterministic defect data and store it in the memory (step 108). The undetermined defects at this time are, for example, the dimple and the mound as described above, but the rest of the undetermined defects may be stored in another storage area of the memory as undetermined defect data.

From the magnitude, continuity, number and defect position (not including defect type) of the defect signal in the defect data before the definite defect data classification, the first magnetic disk (pass disk) It is determined whether or not (step 1
09). In the case of the first magnetic disk, the result is passed here, and the inspection of the glide test process B and the certify process C is not performed in principle. As a general rule, an inspection is performed in the glide test process B and the certify process C or in the certify process C by a sampling inspection as needed to confirm the certainty of the determination of the magnetic disk that has passed the optical inspection. According to this result, the judgment condition is changed so that the judgment is more reliable. With respect to the magnetic disk that has failed in step 109, it is determined whether it is the third magnetic disk (fail disk) that surely fails with reference to the definite defect data generated in step 108, and the rest is left. The second magnetic disk (re-inspection disk) is used (step 110). Then, the first magnetic disk that passed in the determination in step 109 is stored in a disk cassette, and an identification number (lot number + cassette number + storage position) is generated by acquiring the storage position data. The identification number is stored in the memory as pass data (step 111). Regarding the third magnetic disk which has failed in the judgment of the above step 110, the failed one is stored in another disk cassette for rejection and the failure processing is performed (step 11).
2).

With respect to the second magnetic disk that passed in the judgment in step 110, the identification number (lot number + cassette number + storage position) of the magnetic disk and its defect data (determined defect data are re-inspected disks). The defect data before separation) are stored in the memory (step 113). Then, it is determined whether or not the surface defect inspection is completed by determining the presence or absence of the stored magnetic disk in a predetermined cassette (step 114). If not completed, the process returns to step 102. When finished, the pass data of step 111 and step 1
The 12 defect data and the identification number are tabulated and output to a floppy disk (FD) (step 11).
5). When the first or second magnetic disk that has passed the original disk cassette is not stored, the bar code of the storage disk cassette that stores the passed magnetic disk is read and new identification information is generated.

[0029] Now, the determination of the acceptability of the magnetic disk in the above, the size of the defect, continuity of the defect, and, for example, but Ru determined by such as the number of defects present in one track or sector, in particular, Step 10 above
The determination of the undetermined defect 8 is based on the defect type and continuity. The size of the defect is determined by the signal level. By the way, although this flowchart is for the embodiment of FIG. 1, in the processing of the embodiment of FIG. 2, the processing step of the above step 115 is step 115 indicated by a dotted line.
Replaces a. That is, instead of the processing of step 115, the defective data of step 112 collected for the re-inspection disk (second magnetic disk) is tabulated together with the identification number of the second magnetic disk and output to the FD as step 115a. As a result, in the next glide test step B, the defect data is read from the FD,
The inspection is performed mainly on the position of the defect obtained from the defect data. Also in the glide test step B, similarly, a table is created together with the identification number of the magnetic disk and the defective data is output to the FD. As a result, in the next certifying step C, the defect data is read from the FD, and the inspection is performed mainly on the position of the defect obtained from this defect data.

The process of the glide test process B in the case of the embodiment of FIG. 2 will be described with reference to FIG. First, the defect inspection data is read from the FD in step 115a and stored in the memory (step 20).
1) The bar code is read from the bar code label of the disk cassette and stored in the memory (step 202), the magnetic disk to be inspected is set on the inspection table (step 203), and the identification number ( A lot number + cassette number + take-out position) is generated and stored in the memory (step 204). Then, the glide test is started (step 205).

Next, the glide test head is sought to the track corresponding to the position of the read defective data,
Defect inspection is performed on the defect position, before and after the defect position, the sector including the defect position, or the track including the defect position (step 206), and inspection data is collected (step 207). Then, it is determined whether or not the inspection track has ended (step 208), and if there is further defect data, the process returns to step 206, the glide test head is sought to the next defective track, and the inspection data is collected. , Inspect until all defective tracks are finished. When the collection of glide test data for all defective tracks is completed, a pass / fail judgment is made from the test results (step 209). Here, store the accepted magnetic disks in a disk cassette,
An identification number (lot number + cassette number + storage position) is generated by acquiring the storage position data (step 21).
0). Then, it is determined whether or not the inspection is completed (step 211). If there is a next magnetic disk to be inspected in the cassette, the process returns to step 203 and the same test is continued.

When the inspection of all the magnetic disks housed in the cassette is completed, it is judged in step 211 that the inspection is completed, and the identification number of the magnetic disk to be inspected previously stored in the memory is rewritten to the identification number generated in step 210. Then, the identification number of the FD storing the defective data is updated (step 212), and when the result is acceptable, the magnetic disk is sent to the next certifying step C together with the disk cassette. On the other hand, when a failure is found in the previous step 206 and step 209, the failed one is stored in another failing disk cassette and the failing process is performed. Burning in the glide test process is performed by this failing process, and step 203 is performed again.
Enter from and start the glide test. When the result of failure is obtained several times, the magnetic disk is discarded. When returning to the burnish in the glide test process when the result of step 209 is unsuccessful, another identification number associated with the first identification number is added and the above process is performed. Further, as described above, when the passed magnetic disk is not housed in the original disk cassette, the bar code of the disk cassette in step 202 is read by reading the bar code of the new disk cassette that houses the passed magnetic disk. become.

Next, the processing of the certifying step C of the embodiment shown in FIG. 2 will be described in detail with reference to FIG. First,
F whose identification information was updated in step 212 above
The defect inspection data from D is read and stored in the memory (step 301), and the barcode is read from the barcode label of the disc cassette and stored in the memory (step 3).
02), the magnetic disk to be inspected is set in the inspection table (step 303), the identification number (lot number + cassette number + eject position) is generated by acquiring the ejection position data of the cassette, and stored in the memory (step 304). .
Then, the certification test is started (step 3)
05) Next, the magnetic head is sought to the track corresponding to the position of the read defect data, and the defect inspection is performed on the defect position, before and after the defect position, the sector including the defect position, or the track including the defect position. Then (Step 30
6), collecting inspection data (step 307). Then, it is judged whether or not the inspection track is finished (step 30).
8) If there is more defect data, step 30
Returning to step 6, the magnetic head is sought to the next defective track to collect the inspection data. This will inspect until all defective tracks have been completed.

When all the certification test data has been collected for the defective track, a pass / fail judgment is made from the test results (step 309). Here, the passed magnetic disk is stored in a disk cassette, and an identification number (lot number + cassette number + storage position) is generated by acquiring the storage position data (step 310). Then, it is judged whether or not the inspection is completed (step 311), and when there is a next magnetic disk to be inspected in the cassette, the process returns to step 303,
Continue the same test. When the inspection of all the magnetic disks housed in the cassette is completed, it is judged in step 311 that the inspection is completed and the certification test is completed. The accepted magnetic disk is sent to the next appearance inspection step together with the disk cassette. On the other hand, when the result of the above-mentioned step 310 is unacceptable, the unacceptable one is stored in another unacceptable disk cassette and an unacceptable process such as discarding is performed.

FIG. 6 shows the structure of this type of magnetic disk defect inspection apparatus. The detection process will be mainly described, and details of the scanning will be omitted. A magnetic disk defect inspection apparatus for detecting this kind of defect is described in, for example, Japanese Patent Laid-Open No. 3-273141, "Defect detection method and detection optical system for magnetic disk magnetic film". The magnetic disk defect inspection apparatus 10 has two detection optical systems as detection optical systems. Reference numeral 1 denotes a magnetic disk to be inspected, which is rotated by a spindle motor 2 and spirally scanned by a laser beam. 3 is
The projection optical system has a first laser projection light source 3a and a second laser projection light source 3b. The projection angles of the first laser projection light sources 3a and 3b are both around 70 °, but these projection systems are arranged at right angles in the horizontal plane. For convenience of illustration, the angle is only changed. In contrast to these light projecting systems, 4 is a light receiving system,
First light receiving system 4a for receiving the specularly reflected light from the magnetic disk 1 from the laser projecting light source 3a, and the second light receiving system 4a for receiving the specularly reflected light from the magnetic disk 1 from the second laser projecting light source 3b. Light receiving system 4b. In both cases, the light receiving angle is about 70 °, which is the same as the light projecting side.

The difference between the first light projecting system 3a and the second light projecting system 3b is the thickness of the laser beam. The beam of the first light projecting system is a thin beam that is narrowed down as much as possible. In this respect, the beam of the second light projecting system is a wide beam. As a result, the first light receiving system 4a detects pits, and the second light receiving system 4b detects dimples, bumps, and mounds. A defect detection circuit 5 is provided with a first defect detection circuit 51 and a second detection circuit 52 corresponding to the light receiving systems of the first and second light receiving systems 4a and 4b, respectively. The first defect detection circuit 51 includes a filter circuit 51a that receives a detection signal from the first light receiving system 4a, an amplifier 51b that amplifies and outputs a signal from this filter, and this amplifier 51b.
Of the differential amplifier 51c for one-sided amplification for amplifying the signal portion exceeding the threshold value by comparing with the predetermined threshold value VTH1, the peak hold circuit 51d, and the A / D conversion circuit (A /
D) 51e.

The second detection circuit 52 includes a second light receiving system 4b.
Filter circuit 52a for receiving the detection signal of (1), an amplifier 52b for amplifying and outputting the signal from this filter, and one side for receiving the output of this amplifier 52b and comparing with a predetermined threshold value VTH2 to amplify the signal portion exceeding the threshold value. It comprises an amplification differential amplifier 52c, a peak hold circuit 52d, and an A / D conversion circuit (A / D) 52e. The threshold value V
TH1 and VTH2 are adjustable and are set to appropriate values according to the state of the detection signal of each light receiving system. As a result, the two types of defects detected in response to the spiral scanning of the magnetic disk 1 are respectively held by the peak hold circuit 5.
1d, held by the peak hold circuit 52d. Each hold value is converted into a digital value by the A / Ds 51e and 52e according to the control signal of the data processing device 53, and is taken into the data processing device 53. The hold values of the peak hold circuits 51d and 52d are A / D
They are reset by the signals from 51e and 52e, respectively, and the peak values of the next detection signals are held by them.

The data processing device 53 includes a microprocessor (MPU) 53a, a memory 53b, and a display 53.
c, a printer 53d, an interface 53e, etc., which are mutually connected via a bus 53f. The memory 53b has a defect detection program 54a and a defect size / continuity determination program 54.
b, a defect type determination program 54c, a definite defect classification program 54d, a pass / fail judgment program 54e, and the like are provided, and a defect data area 54f and a definite defect data area 54g are further provided. The MPU 53a drives the spindle motor 2 via the interface 53e by executing the defect detection program 54a, and
The spiral scanning is started by controlling the movement in the X direction (or the Y direction is also possible). The control amount is stored in a predetermined area of the memory 53b as scanning position information. And A / D51
Data of e and 52e are fetched through the interface 53e at a predetermined timing, and a processing of storing the detection level in the memory 53b together with the scanning position data corresponding to the detectors of the first and second light receiving systems is performed. .

Defect size / continuity determination program 54
b, the defect data in the first and second light receiving systems of the memory 53b that has been sampled is read out, and the size is ranked according to the value, and the defect data in the first and second light receiving systems is read. Is set in a continuous range, the size information (data indicating the size) is added, and the data is stored in the defect data area 54f together with the defect detection position data. The defect type determination program 54c selects the A / D5 from the data stored in the defect data area 54f.
1e has defect data in a level range of a predetermined value, and it has continuity, and when there is no defect data in the A / D 52e (or, the level is defect data of a predetermined value or less). , And flag it as a dimple or mound. This is defect data in which defects are detected only in the first light receiving system 4a for detecting dimples, mounds, and bumps, and the defects are continuous and have a low detection level. Therefore, the condition is that no defect is detected in the second light receiving system 4b that detects pits. Here, the level in the range of the predetermined value for the A / D 51e is to exclude the bump, and in the case of the bump, the level of the detection signal is high. Also, most of them are not continuous.

The definite defect classification program 54d extracts from the data in the defect data area 54f the defects other than the defects judged to be dimples or mounds by the defect type judgment program 54c as definite defects, including their size and continuity. Then, the defect position data is stored in the confirmed defect data area 54g. In this case, the definite defect data may be deleted from the data in the defect data area 54f, and the data in this area may be set as the undetermined defect data. In this case, when the entire defective data is needed, the data in both areas will be referred to. Further, a fine single bit defect capable of 1-bit correction may be excluded from the deterministic defect. The pass / fail judgment program 54e is used for the defect data area 5
From the data of 4f, the first magnetic disk is judged according to the criteria of size, continuity, number of defects, and its position. Further, the third magnetic disk is similarly judged from the data of the definite defect data area 54g according to the judgment criteria of the size, the continuity, the number of defects, and the position thereof.

By the way, first, by increasing the accuracy of the optical surface inspection and adopting a high standard for the passed magnetic disk, the magnetic disk which is surely passed by the electrical inspection can be optically tested. He said that he can choose by inspection.
However, in reality, due to the difference in characteristics between the optical surface inspection and the electrical inspection, the optical surface inspection cannot be a sufficient guarantee for the certification inspection for all defects. There is some deviation between them.
The reason for this is that the optical inspection conditions and the inspection environment influence and change a little. Also, there are some defects in which the electrical characteristic inspection and the optical characteristic inspection do not match. Therefore, as described above in the embodiments, is it possible to reliably determine a magnetic disk that has passed the optical inspection by performing a certification inspection by sampling the first magnetic disk that has passed the optical surface inspection? It is necessary to confirm whether or not, or to change the inspection condition according to the state of the inspection so that more reliable determination can be made.

However, the problem in this case is the quality of the magnetic disk inspected until the more reliable condition is set. Therefore, in order to deal with such a problem with the first magnetic disk, a sampling certification test, a certification test at a coarse pitch, a certification test only at a defect location and its periphery, and a combination test of these are performed. It is possible to prevent the quality of the manufactured magnetic disk from deteriorating. The sampling inspection does not bring about a reduction in the overall inspection efficiency even if the sampling amount increases a little, as long as it does not reach all the first magnetic disks that have passed the optical inspection.
The inspection only around the defect is performed on the second magnetic disk described in the embodiment. This is performed on the first magnetic disk that has passed the optical surface inspection. That is, the defect data of the first magnetic disk is output, and the defect point and the periphery of the defect point are inspected based on this defect data. In addition, it is more efficient than the conventional full-face inspection to take a rough track pitch for the certification inspection. The above is important in terms of quality assurance of the magnetic disk, and does not particularly lower the inspection efficiency. This is because the conventional certification inspection is a full-face inspection.

As described above, in the embodiment, the type data is used as the defect data, and the defect data is classified into the undetermined defect and the confirmed defect. Alternatively, only fixed defects may be extracted from the size, number, and position data in consideration of defect continuity. In addition, as described above, the definite defect data is deleted from the data in the defect data area 54f, the data in this area is made into the unconfirmed defect data, and only the position data of this unconfirmed defect data is output. It is also possible to carry out the test of 1) or the test of the certifying step C only for the position of this undetermined defect, and to judge the pass / fail together with the confirmed defect.

In the embodiment, in order to improve the classification accuracy of the second magnetic disk and the third magnetic disk, the continuity of defects and the types of defects are included in the inspection target. Even if no consideration is given, the number of the second magnetic disks is increased, and even so, the inspection efficiency can be improved because the first magnetic disks are not inspected. Therefore, the type of defect is not necessarily a requirement for the invention. In the embodiment, the defect data is managed by the FD (floppy disk), but it may be managed by another storage medium, and the defect data may be transmitted to the subsequent process by using the online network. Good.

[0045]

As can be understood from the above description, according to the present invention, in the surface defect inspection step, the magnetic disk to be inspected is classified into three to perform the glide test and certify. At this stage, a magnetic disk that passes without any decision is determined. From the fact that most magnetic disks pass the bad magnetic disks, most of the defects are obtained by an optical inspection in which a highly accurate surface defect inspection is performed and the electrical characteristics also pass from the defect data. For example, it is possible to obtain a passing magnetic disk having a magnetic field of about 30% or more. As a result, it is possible to reduce the number of magnetic disks to be inspected that undergo the glide test or certify. As a result, the number of targets of the defect inspection of the conventional magnetic disk can be reduced, and the efficiency of the defect inspection of the magnetic disk can be improved as a whole.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an overall processing procedure to which a magnetic disk defect inspection method according to an embodiment of the present invention is applied.

FIG. 2 is an explanatory diagram of an overall processing procedure to which a magnetic disk defect inspection method according to another embodiment of the present invention is applied.

FIG. 3 is a flowchart of surface defect inspection in the magnetic disk defect inspection method of the present invention.

FIG. 4 is a flow chart of a glide test in the magnetic disk defect inspection method of the present invention.

FIG. 5 is a flowchart of certification in the magnetic disk defect inspection method of the present invention.

FIG. 6 is a block diagram of a magnetic disk defect inspection apparatus to which the defect inspection method according to the present invention is applied.

7A and 7B are partial cross-sectional views of a typical surface defect in a magnetic disk, FIG. 7A is an explanatory diagram of a dimple defect, and FIG. 7B is an explanatory diagram of a pit defect.

FIG. 8 is an explanatory diagram of a conventional process of manufacturing and inspecting a magnetic disk.

[Explanation of symbols]

1 ... Magnetic disk, 2 ... Spindle motor, 3a, 3b
... Laser projection light source, 4a, 4b ... Light receiving system, 5, 51,
52 ... Defect detection circuit, 10 ... Surface defect inspection apparatus, 11 ...
Disk substrate, 12 ... Plating layer, 13 ... Magnetic film sputtering layer, 14 ... Lubrication layer, 51a, 52a ... Filter circuit, 51b, 52b ... Amplifier, 51c, 52c ... Differential amplifier, 51d, 52d ... Peak hold circuit, 51e ，
52e ... A / D conversion circuit (A / D), 53 ... Data processing device, 53a ... Microprocessor (MPU), 53b
... memory, 53c ... display, 53d ... printer,
53e ... Interface, A-1 ... Inspection process, A-2 ...
Defect data sorting step, A-3 ... Passed disk determination step, A-4 ... Failed magnetic disk sorting step, A-5 ...
Defect data output process.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-63-317748 (JP, A) JP-A-63-302384 (JP, A) JP-A-62-267651 (JP, A) JP-A 61- 80009 (JP, A) JP 10-221272 (JP, A) JP 9-167789 (JP, A) JP 9-113463 (JP, A) JP 9-79991 (JP, A) JP-A-9-72722 (JP, A) JP-A-8-220003 (JP, A) JP-A-8-159898 (JP, A) JP-A-8-68674 (JP, A) JP-A-8-22619 (JP, A) JP 7-229839 (JP, A) JP 7-92106 (JP, A) JP 6-281590 (JP, A) JP 6-162496 (JP, A) Kaihei 6-148088 (JP, A) JP-A-6-118015 (JP, A) JP-A-5-332754 (JP, A) JP-A-4-95861 JP, A) JP flat 3-230320 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) G01B 5/84 G01B 19/02 G01N 21/88 G01N 21/95

Claims (13)

(57) [Claims] 1. A magnetic disk is optically inspected for defects,
Based on the defect data obtained in the surface defect inspection process, which detects defect size, continuity, number, and defect position as defect data with higher accuracy than defect inspection by a later inspection. A first magnetic disk that does not cause a problem in the subsequent inspection step, a second magnetic disk that has to be further inspected in the subsequent inspection step to determine whether or not it causes a problem, and Magnetic disk defect inspection method including a classification step of classifying the magnetic disk into a third magnetic disk that does not need to be judged in the inspection step. 2. A magnetic disk is optically inspected for defects,
A surface defect inspection step of detecting defect size, continuity, number, and defect position as defect data with higher accuracy than a defect inspection by electrical characteristics in a certification inspection, and defects obtained in this surface defect inspection step Based on the data, a first magnetic disk that does not cause a problem in electrical characteristics and that passes the certification test, and a certification test must be further performed to determine whether or not there is a problem in electrical characteristics. A magnetic disk defect inspection method comprising: a second magnetic disk that does not become a failure; and a third magnetic disk that is classified as a third magnetic disk that fails in terms of electrical characteristics without having to make a determination in the certification inspection. 3. The defect data further includes a defect type, and a certification inspection is performed as the subsequent inspection process, and a glide test process for performing a glide test on the second magnetic disk is provided in front of it. 2. The magnetic disk defect inspection method according to claim 1, wherein the second magnetic disk that has passed the glide test step is inspected in the certify step. 4. Further, the data of at least the defect position of the second magnetic disk and the identification information for identifying the second magnetic disk from other magnetic disks are used for the inspection in the subsequent inspection step. 5. A magnetic disk defect inspection method according to claim 3, further comprising a defect data output step of outputting defect information for performing the inspection, and inspecting according to the defect information in the subsequent inspection step. 5. The type of defect includes a type of defect for which reading / writing of data is not substantially guaranteed.
In the classification step, the first magnetic disk is extracted from the magnetic disks subjected to inspection, and the third magnetic disk is extracted from the remaining magnetic disks excluding the first magnetic disk. 4. The magnetic disk defect inspection according to claim 3, wherein the rest is used as the second magnetic disk, and a defect in which the reading / writing of the data is not guaranteed when extracting the third magnetic disk is referred to. Method. 6. The magnetic disk defect inspection method according to claim 5, wherein the defect in which the reading / writing of data is not guaranteed is a pit defect. 7. A magnetic disk defect inspecting apparatus for optically inspecting a magnetic disk for defects, the defect data including defect size, continuity, number, and defect position from defect inspection based on electrical characteristics in a certification inspection. A detection means for detecting with high accuracy, a first magnetic disk which is acceptable in the certification inspection without causing a problem in electrical characteristics based on the defect data obtained by the detection means, and a certification inspection. Further, the second magnetic disk for which it is necessary to determine whether or not the electrical characteristic does not pose a problem, and the third magnetic disk for which the electrical characteristic is rejected without the necessity of performing the determination in the certification test. magnetic disk inspection apparatus to obtain Bei and classification means for classifying into a disk. 8. The magnetic disk defect inspection apparatus according to claim 7, wherein the defect data further includes a defect type, and the certify inspection inspects the second magnetic disk that has passed a glide test. . 9. In order to utilize at least the defect position data of the second magnetic disk and identification information for identifying the second magnetic disk from other magnetic disks in the subsequent inspection step. Defect data output means for outputting as defect information to the defect information, the defect information is read in the glide test, based on the data of the defect position obtained from the defect information, the defect position, before and after the defect position 9. The magnetic disk defect inspection apparatus according to claim 8, wherein the glide test is performed on any one of the sector including the defect position and the track including the defect position. 10. The defect data further includes a defect type, and the first magnetic disk is inspected in the certifying step, and the classification condition in the classifying step is determined according to the inspection result. The magnetic disk defect inspection method according to claim 2, which is set. Wherein said defect data is one further including the type of defect, performing the first magnetic disk sampling certify inspection and the defect number office certify inspection of its periphery to rough track pitch inspection 3. The inspection according to any one of the certification inspections.
The magnetic disk defect inspection method described. 12. The defect data further includes the type of defect, and the first magnetic disk is inspected in the certifying step, and the classification condition in the classifying step is determined according to the inspection result. The magnetic disk defect inspection device according to claim 7, which is set. Wherein said defect data is one further including the type of defect, performing the first magnetic disk sampling certify inspection and the defect number office certify inspection of its periphery to rough track pitch inspection 8. Any one of the certification inspections is performed.
The magnetic disk defect inspection device described.