JP2003121114A - Apparatus for measuring track width of magnetic head by measured image of optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for measuring the track width of a magnetic head by a measured image of an optical system and capable of measuring the width of a track from luminance data obtained from the image of the measuring optical system, even at a magnifying level close to the limit of its resolution or below it. SOLUTION: The apparatus for measuring the track width of the magnetic head is provided with both a converting means for obtaining the width of the track from a luminance level, when the luminance level of a peak for obtaining the width of the track is equal to a measurable level or less determined by the resolution of the measured image of the optical system; and a determining means for determining whether the luminance level of the peak is higher than the measurable level or lower. When the luminance level of the peak is equal to the measurable level or less at the determination of the determining means, the width of the track is computed by performing conversion by the converting means.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a track width measuring device for a magnetic head by means of an optical system measurement image, and more specifically, a track width of an inductive head of an MR composite head is photographed by a CCD camera through a measuring optical system. In a measuring device for measuring the track width from the obtained image, a magnetic head capable of measuring the track width from the luminance data obtained from the image even when the resolution of the measurement image of the measurement optical system is close to or below the limit. Track width measuring device.

[0002]

2. Description of the Related Art At present, as a magnetic head of a hard disk drive, an inductive head (thin film head) is used as a write side head, and an MR head, a GMR head, a TMR head (hereinafter referred to as MR) as a read side head.
A so-called composite magnetic head in which a read head or the like) is attached to one slider is used.
A composite magnetic head (hereinafter referred to as an MR composite head) having this type of MR read head, etc.
The track width of read heads such as GMR heads and TMR heads has become extremely narrow at 0.3 μm or less. Along with this, the width of the inductive head (thin film head) has also become very narrow, 0.3 μm or less. As a conventional technique for measuring the track width of such a narrow head, Japanese Patent Laid-Open No. 9-250
No. 910, “Thin film MR head track width measuring method”, and Japanese Patent Laid-Open No. 2001-153614, “Thin film magnetic head manufacturing method, inspecting apparatus, and inspecting method”. These use a measurement optical system and a two-dimensional CCD camera to collect an image of the magnetic head portion seen from the slider surface (floating surface) of the MR composite head in an image memory (frame memory), and then use the MR composite head from the image. This is a technique for obtaining the track width from the brightness difference (contrast) in the head gap part.

FIG. 4 shows an example of the apparatus configuration. An image of the magnetic head portion shown in FIG. 5 seen from the slider surface of the MR composite head obtained by the measurement optical system 1 is A / D converted by an A / D converter 26. The data is D-converted and recorded in the frame memory in the computer by the computer 27, and the data on the line 5-5 in FIG. 5 is read out as the data of the head gap portion of the MR composite head, particularly the inductive head, recorded here. By inverting it, the data of the luminance signal 6 as shown in FIG. 6A (the data represented as an analog signal, the same applies hereinafter) is obtained. The luminance signal 6 is
Image data is inverted, and by inverting it,
The level of the head gap part of the MR composite head having a low brightness level is set to a high value with reference to the level of the metal electrode part having a high brightness level. Next, this brightness data (brightness signal 6) is further differentiated to obtain the differential data (differential analog signal 6a) of FIG. 6B, and the zero-cross point h1,
The distance TWW between h2 is obtained and used as the track width of the inductive head on the writing side of the MR composite head. In FIG. 5, 41 is a core portion of the inductive head of the MR composite head 40, 42 is a gap portion thereof, and 4 is a gap portion thereof.
3 is a shield part (high brightness level part), 44
Is a laminated film portion of the magnetoresistive element that constitutes the MR head (the portion that constitutes the gap).

The track width measuring apparatus 100 of FIG. 4 for performing such a measurement comprises a measuring optical system 1, an autofocus system 2, an image signal processing / control system 3, and a stage system 4. The row bar 2, which is a strip-shaped substrate of the MR composite magnetic head cut out from the wafer, is placed on the Z stage 16 of the XYZθ stage, and the track width of each MR composite magnetic head is measured here. The measurement optical system 1 includes a light source 7, a relay lens 9, and a polarizing plate 10 on an optical axis 8 as an illumination optical system, and the optical axis 8 is a beam splitter 11.
Is bent toward the stage system 4.
A dichroic mirror 12 and an objective lens 13 are arranged on the optical axis 8 between the beam splitter 11 and the stage system 4. On the optical axis 81 separated from the optical axis 8 by the beam splitter 11, a polarizing plate 23, an image forming lens 24, and a CCD solid-state image sensor 25 are arranged. The dichroic mirror 12 is used for the autofocus system 2.
It is arranged so that the light from is incident on the objective lens 13. Here, the light source 7 is DUV light having a wavelength of 248 nm.
It is a light source that emits (far infrared rays). Specifically, the light source 7
As a mercury-xenon lamp with a transmission center wavelength of 248
A combination with an nm interference filter is used to transmit a vector having a central wavelength of 248 nm in the light emitted from the lamp. Further, the relay lens 9, the objective lens 13, and the imaging lens 24 are all D
A UV light compatible lens is used.

The image signal processing / control system 3 performs A / D conversion on the analog image signal from the CCD solid-state image pickup device 25.
It has a / D converter 26, a calculator 27, memories 29 and 30 connected to the calculator 27, and a display 28. The calculator 27 measures the XY stages 14x, 1 at the time of aligning and measuring the measurement position of the row bar 2 (the strip-shaped substrate of the MR composite magnetic head cut out from the wafer).
4y, θ stage (rotary stage) 15, Z stage 1
In order to control the driving of No. 6, it is connected to the stage driver 17 and drives this driver. In addition, the calculator 27
Receives an image picked up by the CCD solid-state image pickup device 25 (corresponding to a measurement image of the measurement optical system converted into an electric signal, and the resolution of the measurement image of the measurement optical system is reflected), and the image is processed. CCD solid-state image sensor 25 through the A / D converter 26 to measure the track width and the like.
It is connected to the. Further, the calculator 27 is connected to a difference circuit 21 for knowing the focus state, and receives a signal for focus control from this circuit. The automatic focusing system 2 includes a semiconductor laser light source 18 having a wavelength of 750 nm for focusing, its laser light 19, light receiving elements 20a, 2
It is provided with a two-divided light receiving element 20 composed of 0b and a difference circuit 21. On the other hand, in Japanese Patent Laid-Open No. 9-250910, MR
As for the track width of the head, the luminance at the position corresponding to the level of the metal electrode portion is referred to the reference level (the luminance level of the portion corresponding to the shield portion 43 having the high luminance level) from the luminance data before inversion in FIG. 6A. Assuming that this is 100%, the width of the position of the luminance level of 30% is obtained and measured as the track width of the MR head.

[0006]

However, in such a method for measuring the head track width, the measurement track width depends on the resolution of the measurement image of the measurement optical system, and the measurement track width is the limit of the resolution of the measurement optical system. If the distance is close, the track width cannot be measured with sufficient accuracy because the brightness data 6 cannot be sufficiently contrasted. As the resolution of a measurement image of a normal measurement optical system, there is JP-A-2001-153614.
As described in the prior art, the center wavelength is 0.
When using visible light of about 5 μm, the numerical aperture NA is set to 0.
Even with 8, the resolution is around 0.4 μm. Therefore, the track width of 0.3 μm or less becomes the resolution limit, and it is difficult to measure the track width with high accuracy. Japanese Patent Laid-Open No. 2001-153614 discloses a DUV having a wavelength of 248 nm in order to solve such a problem.
Although the above-mentioned configuration is adopted by using the light source, the limit is about 0.2 μm due to the limit of resolution of the measurement optical system, and there is a problem that accurate measurement cannot be performed when the track width is less than that. . Such track width is
It is possible to make measurements with scanning electronic measurement optics (SEM), but this would require the use of expensive measuring equipment. An object of the present invention is to solve the above-mentioned problems of the prior art. Even if the resolution of the measurement optical system is near or below the limit, the track width of the track width is determined from the luminance data obtained from the image. It is an object of the present invention to provide a track width measuring device for a magnetic head by means of an optical system measurement image that can be measured.

[0007]

A characteristic of the track width measuring apparatus for a magnetic head by an optical system measurement image of the present invention for achieving such an object is that the brightness level of the image of the head portion in the optical system measurement image is In a track width measuring device for a magnetic head using an optical system measurement image that calculates the track width from the width of the peak portion, the luminance level of the peak portion that obtains the track width is below a measurable level determined by the resolution of the optical system measurement image. It is equipped with a converting means for obtaining the track width from the brightness level and a judging means for judging whether or not the brightness level of the peak portion is below a measurable level, and the brightness level of the peak portion is measured in the judgment of the judging means. The track width is calculated by converting by the converting means when the level is below the possible level.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, when the luminance level of the peak portion for calculating the track width is equal to or lower than the measurable level, the conversion means for obtaining the track width from the luminance level is provided so that the peak of the luminance signal is Even if the track width cannot be calculated from the width of the portion, the track width can be obtained by the conversion means, and the resolution is close to the resolution limit of the optical system measurement image.
The track width of the magnetic head can be measured up to that level. As a result, even with a head with a track width close to or less than the resolution limit of the measurement image of the measurement optical system,
The track width can be measured from the brightness data obtained from the measurement image, and 0.3 even without using an expensive device such as an SEM.
A track width measuring device for a head having a narrow track width of about μm or less can be easily realized.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an MR according to an embodiment to which the present invention is applied.
FIG. 2 is a block diagram centering on a data processing device of a track width measuring device of a composite head, FIG. 2 is an explanatory diagram of a measurement line width data conversion characteristic graph, and FIG. 3 is a flowchart of the track width detecting process. It should be noted that constituent elements equivalent to those in FIGS. 4 to 6 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 1, reference numeral 50 denotes image signal processing of the track width measuring device 101. The data processing device in the control system corresponds to a device including the computer 27 of FIG. 4, memories 29 and 30 connected to the computer 27, and the display 28. Another configuration of the track width measuring device 101 is composed of the measuring optical system 1, the autofocus system 2 and the stage system 4 of FIG. The data processing device 50 is an MP
The U51, a memory 52, a frame memory 53, a CRT display 54, an interface 55, a keyboard 56, etc. are connected to each other by a bus 57. Here, the optical system measurement image obtained by the measurement optical system 1 is the CCD solid-state image sensor 25 (see FIG.
The image is captured by the A / D converter 26 and converted into a digital value. The image data for one frame obtained from the A / D converter 26 is temporarily stored in the frame memory 53. One frame of measurement data obtained from the frame memory 53 is MP-processed via the bus 57.
It is read by U51 and it is recorded 52 via bus 57.
Are transferred to and stored in.

The memory 52 stores a measured image data collection program 52a, a peak brightness detection program 52b, a track width calculation program 52c, and various programs such as a focusing program. Also, the brightness / line width conversion table 52
d, a work area 52e, a parameter area 52f for storing control data for measurement, and the like are provided. further,
Various data files are stored in an external storage device 58 such as an HDD (hard disk device) connected via the interface 54. The measurement image data collection program 52a is executed by the MPU 51 and
In the frame memory 53, one frame of the image of the measurement data is sampled and stored. Then, the peak brightness detection program 52b is called. The peak brightness detection program 52b is executed by the MPU 51 to
Is the data (data on the line 5-5 in FIG. 5) of the inductive head of the MR composite head extracted from the data stored in the frame memory 53, and the data (luminance in FIG. 6A) is extracted. The average value Pa of the luminance of the peak portion is calculated from (corresponding to the signal 6). The average value Pa of the brightness of the peak part is calculated as a peak part by extracting a plurality of data in the range from the maximum peak value to 10% below. The average value Pa is determined whether the brightness is 45% or less when the brightness of the shield portion 43 is 100%, and the flag of the determination result of the average brightness value Pa is stored in the memory 5.
It is stored in the second work area 52e and the track width calculation program 52d is called. The determination flag is the average value P
If a exceeds 45% in brightness, it is set to "10", and if not, it is set to "01". By the way, the level of the shield part 43 of the inductive head is used as a reference (100
%), The brightness level of the peak value of the brightness signal 6 as shown in FIG. 6A is about 50%. At this time, as described in the related art, the zero-cross point h
The TWW can be calculated by the distance between 1 and h2, but when the average value Pa becomes 45% or less of the brightness, the zero cross points h1 and h2
It becomes difficult to find the TWW at the distance between them.

The track width calculation program 52c uses MP
The UPU 51 executes the work area 52.
With reference to the determination flag of e, the average brightness value Pa is 45
When the value exceeds 10% (when the flag value is "10"), the luminance signal 6 as shown in FIG. 6A is further differentiated to obtain the differential data of FIG. Then, the distance TWW between h1 and h2 at the zero-cross point is obtained and is set as the track width of the inductive head of the MR composite head. The track width calculated here is stored in the work area 52e of the memory as the track width TWW of the inductive head of the MR composite head. On the other hand, when the average brightness value Pa is 45% or less, the track width is converted from the average brightness value Pa calculated by referring to the brightness / line width conversion table 52e, and the work area 52e is converted into the inductive head of the MR composite head. It is stored as the track width TWW.

FIG. 2 shows a track width 200 to be measured.
In a range including nm to 80 nm (corresponding to a range close to or less than the resolution limit of the measurement image of the measurement optical system), an explanatory diagram of a characteristic graph of data of the luminance / line width conversion table 52d of the inductive head of the MR composite head is there. The vertical axis represents the relative luminance% and the horizontal axis represents the line width (track width) [nm] at the data position (head gap portion) on the line 5-5 in FIG. 5 of the inductive head of the MR composite head.
The relative brightness% is a ratio of the brightness of the core part 41 of the inductive head 41 when the brightness obtained by the reflected light of the shield part 43 of FIG. 5 is used as a reference (= 100%). As shown, the track width is 200 nm to 80 nm
In the inductive head of the MR compound head, the average luminance value Pa is around 45% or less, and the relationship between the luminance and the line width of the inductive head having these track widths has a substantially linear inclination characteristic. Then, from the point where the average luminance value Pa exceeds 45% of the luminance, the inclination becomes gentle in the horizontal direction. Then, where the average brightness value Pa where the slope is blunt exceeds 45% of the brightness, there is a large amount of data of the peak portion, and the width of the peak portion corresponds to the line width. On the other hand, when the average luminance value Pa is 45% or less, the peak has a luminance signal waveform 6c as shown by the dotted line graph in FIG. 6A, and when the track width is calculated from the width of the peak portion, there is a large error. As a result, accurate measurement cannot be performed. However, the brightness / line width conversion table 52d
By converting in, it becomes possible to measure with higher accuracy. That is, the brightness / line width conversion table 52d is a conversion table of brightness and line width that obtains a line width from a brightness of 45% or less. Note that the characteristics of FIG. 2 have a track width of 200 nm to 80 nm of a measurement target corresponding to a range near or below the resolution limit of the measurement image of the measurement optical system.
Brightness of inductive head of MR composite head including /
It is an explanatory view of a line width conversion table. Such a characteristic shows that the track width data actually measured by the SEM or the like and the average brightness Pa data in the track width measuring device of FIG. This is the result of measuring the track width of the inductive head and statistically processing it, and it was discovered that such a result is obtained.

FIG. 3 is a flowchart of the track width detection processing. In FIG. 3, the measurement image data collection program 52
a is executed by the MPU 51, and one frame of the image of the measurement data is stored in the frame memory 53 (step 1
01). Next, the peak brightness detection program 52b
This is executed by the PU 51 to read the data of the position of the line 5-5 of the inductive head of the MR composite head (the head gap portion of the inductive head of the MR composite head) (step 102), and then the peak brightness detection program 52b. Is executed by the MPU 51 to calculate the average luminance Pa of the peak portion (step 103).
Then, it is determined whether or not the average luminance Pa exceeds 45% (step 104), and if it exceeds Y, Y
ES, the luminance data of the peak portion is differentiated, and the line width of the inductive head of the MR composite head on the line 5-5 at that time, that is, the track width TWW is calculated from the positions of the two zero cross points h1 and h2. It is calculated (step 105). On the other hand, the brightness of 4 is determined in step 104.
When it becomes 5% or less, the average brightness Pa is calculated by referring to the brightness / line width conversion table 52d to calculate the line width of the inductive head of the MR composite head on the line 5-5, that is, the track width TWW (step 106). The measured MR
Track width TWW of inductive head of compound head
Is stored as a measurement result in a predetermined area transferred to the HDD 58 after the measurement.

As described above, in the embodiments, the description has been centered on the measurement example of the track width Tww of the inductive head of the MR composite head having the track width of 200 nm to 80 nm, but the present invention is not limited to the MR head and the GMR. head,
It is needless to say that it can be applied to the measurement of the track width Twr of the TMR head or the like. Further, in the luminance vs. line width characteristic shown in FIG. 2, the reflection characteristic also changes if the material and the head structure change. Therefore, the value of the relative luminance of 45% depends on the reflection characteristic at that time and the place where the reference level is taken. , For example, 30
%, Which is a value selected depending on the characteristics at that time, and is not a fixed value. Further, the reference level may be determined not at the relative luminance but at a position lower than the peak level of the luminance vs. line width characteristic by a certain value. Further, in the embodiment, the line width is obtained as the track width by the brightness / line width conversion table when the average brightness of the peak value is equal to or less than the predetermined value with the seal portion of the head as a reference. The conversion function is not limited, and may be a conversion function corresponding to the above characteristics. Further, the reference level is not the seal portion of the head, but Japanese Patent Laid-Open No. 9-2509.
Needless to say, it may be a metal electrode portion as in No. 10, and other portions having high reflection luminance may be used as a reference.

[0015]

As described above, in the present invention, when the luminance level of the peak portion for calculating the track width is below the measurable level, the converting means for obtaining the track width from the luminance level is provided. Thus, even if the track width cannot be calculated by the width of the peak portion of the luminance signal, the track width can be obtained by the conversion means, and the track width of the magnetic head can be adjusted to near the resolution limit of the optical system measurement image or below it. Can be measured. As a result, even with a head having a track width close to or less than the resolution limit of the measurement image of the measurement optical system, the track width can be measured from the luminance data obtained from the measurement image, and an expensive device such as SEM is used. It is possible to easily realize a track width measuring device for a head having a narrow track width of about 0.3 μm or less without using.

[Brief description of drawings]

FIG. 1 is a block diagram centering on a data processing device of a track width measuring device for an MR head according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a measurement line width data conversion characteristic graph.

FIG. 3 is a flowchart of the track width detection processing.

FIG. 4 is a configuration diagram of a conventional track width measuring device for an MR head.

FIG. 5 is an explanatory diagram of a measurement image of the MR head.

FIG. 6 is an explanatory diagram of the luminance signal.

[Explanation of symbols]

1 ... Measuring optical system, 2 ... Automatic focusing system, 3 ... Image signal processing
Control system, 4 Stage system 5 Line of MR head gap on image, 6 Luminance signal, 7 Light source, 8 Optical axis, 9
... relay lens, 10 ... polarizing plate, 11 ... beam splitter, 12 ... dichroic mirror, 13 ... objective lens,
14x, 14y ... X, Y stages, 15 ... θ stage (rotating stage) ... Z stage, 17 ... Stage driver, 18 ... Semiconductor laser light source, 19 ... Laser light, 20
2 split light receiving element, 21 differential circuit, 23 polarizing plate, 2
4 ... Imaging lens, 25 ... CCD solid-state image sensor, 26 ... A
/ D converter, 27 ... Calculator, 28 ... CRT display, 29, 30, 52 ... Memory, 40 ... MR composite head, 41 ... Inductive head core portion, 42 ... Gap portion, 43 ... Shield portion, 44 ... MR head ,
50 ... Data processing device, 51 ... MPU, 52a ... Measurement image data collection program, 52b ... Peak brightness detection program, 52c ... Track width calculation program, 52d
... Brightness / line width conversion table, 52e ... Work area, 53 ...
Frame memory, 54 ... CRT display, 55 ... Interface, 57 ... Bus, 58 ... External storage device 100, 101 ... Track width measuring device.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nao Toyoda             Hitachi Electronics, 3-16-3 Higashi, Shibuya-ku, Tokyo             Engineering Co., Ltd. F term (reference) 2F065 AA22 CC37 DD03 FF04 FF10                       GG03 GG06 GG22 JJ03 JJ26                       KK01 LL04 LL20 LL22 LL33                       LL46 PP01 PP03 PP12 PP22                       PP24 QQ03 QQ13 QQ24 QQ29                       QQ30 QQ42 UU05 UU07

Claims (4)

[Claims] 1. A track width measuring apparatus for a magnetic head using an optical system measurement image, wherein a track width is calculated from a width of a peak portion of a brightness level of an image of a head portion in an optical system measurement image. Conversion means for obtaining a track width from the brightness level when the brightness level is below a measurable level determined by the resolution of the optical system measurement image, and whether or not the brightness level of the peak portion is below the measurable level And a determination unit that determines the track width by converting by the conversion unit when the luminance level of the peak portion is equal to or lower than the measurable level in the determination by the determination unit. System for measuring track width of magnetic head using system measurement image. 2. The optical system measurement according to claim 1, wherein the luminance level of the peak portion is calculated as an average value of the luminance obtained with reference to the level of the portion having a high luminance level, and the converting means is a conversion table. Track width measuring device of magnetic head by image. 3. The track width measuring device for a magnetic head according to claim 2, wherein the level of the reference high luminance part is the shield part of the head. 4. A track width measuring device for a magnetic head according to an optical system measurement image according to claim 2, wherein the level of the reference high brightness level is a metal electrode part.