JP3339777B2 - Magnetic head flying height measurement 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 head flying height measuring apparatus, and more particularly, to a thin film head.
The present invention relates to a magnetic head flying height measuring apparatus capable of measuring a flying height with high measurement accuracy in accordance with an actual state of a magnetic disk storage device (hereinafter, a magnetic disk device) in measurement of a minute flying height.

[0002]

2. Description of the Related Art FIG. 5 is a view for explaining the relationship between a magnetic disk and a floating type head (hereinafter simply referred to as a head) floating from the surface of the magnetic disk. As shown in FIG. 1 is mounted on a spindle 2 and rotates. Head 3 for reading / writing data from / to magnetic disk 1
1 is attached to the tip of the support arm 32, and the rear end of the support arm 32 is fixed to a support member 41 provided on the carriage mechanism 4. The head 31 is moved by the carriage mechanism 4 and loaded on the magnetic disk 1.

FIG. 1B shows the shape of the head 31. A slider surface 311 is formed on the bottom surface.
As shown in (c), the slider surface 311 flies above the surface by the flying height h, and data is accessed for a predetermined track. Since the flying height h is extremely important for the operation of the head, each head is measured and inspected by a head flying height measuring device.

[0004]

FIG. 6 shows an outline of a head flying height measuring apparatus using a white light interference wave method. In FIG. 1A, a quartz disk transparent disk (hereinafter simply referred to as a disk) 5 is used for a test, which is mounted on the spindle 2 and rotated, and the head 31 is mounted on the back surface 52 of the disk 5 by the carriage mechanism. The head is loaded and floated by the head loading mechanism 3 corresponding to 4. A measuring optical system 6 is provided above the disk 1,
Wavelength band (λa to λb) from light source 61 of xenon lamp
The white light L _T, is projected to the disk 5 by the objective lens 64 through a light projecting lens 62 and the half mirror 63. Although a part of the white light L _T surface 51 and rear surface 52 are reflected predominantly illuminates the slider surface 311 passes through. The head loading mechanism 3 is controlled by the data processing device 7.

Here, as shown in FIG. 1B, the reflectances of the front surface 51, the back surface 52, and the slider surface 311 are q and q, respectively.
r, s, and the reflected light are Rq, Rr, and Rs, respectively. The reflected lights Rr and Rs interfere with each other to generate an interference wave Rrs, pass through the half mirror 63, reach the concave diffraction grating 65 which is a spectrum spectroscope, and are spectrally separated. However, since white light is used and the thickness d of the disk 5 is much larger than the flying height h, the mutual interference between the reflected light Rq and the reflected lights Rr and Rs is very small and can be ignored.
The interference wave Rrs is received by the linear sensor 66, and is used as a pattern signal of a spectrum corresponding to each wavelength, as shown in FIG.
A pattern signal having a spectrum corresponding to the wavelength as shown in FIG. This pattern signal is sent to the data processing device 7
The flying height h is obtained by performing data processing in.

That is, in FIG. 1C, if the horizontal axis is the wavelength λ and the vertical axis is the interference wave intensity Irs, for example, the wavelength λ 1
The peak points p ₁ , p ₂ and p ₃ are formed at λ 2 and λ 3. Where the reflected light R
Assuming that the phase angle between r and Rs is δ, the following relational expression exists between the phase angle δ, the flying height h, and the wavelength λ. δ = 4πh / λ, (λ: λa to λb) (1) Using this equation (1), the flying height can be calculated from the wavelengths λ1, λ2, λ3 of the peak point. On the other hand, the reflectance of the interference light of the minute clearance with respect to the incident light is generally expressed by the following equation. Where δ = 4πh / λ, λ: wavelength, h: flying height, R
(Λ, h): reflectance at flying height h at wavelength λ, r
(Λ): the reflectance at the wavelength λ of the glass disk viewed from the air layer, and s (λ): the reflectance at the wavelength λ of the head viewed from the air layer. According to this equation, the flying height as a theoretical value can be obtained from the spectral distribution and the reflectance of the wavelength of the interference light.

In the measurement of the flying height of the magnetic head, when the flying height is obtained by the equation (1) which is a relational expression among the phase angle δ, the flying height h, and the wavelength λ, there is no problem when the flying height is large. However, when the flying height is 0.1 micron or less, if it is measured with high accuracy, there is a problem that a peak point may not appear and measurement cannot be performed. Therefore, it is conceivable to calculate the flying height using the value calculated from the theoretical value obtained by the latter equation (2) as a comparison reference value. An error easily occurs between the flying height of the magnetic head and the measured value. One of the reasons is
First, the reflectivity r, it is a benzalkonium mentioned that the value of s is different from that of the actual head.

Further, if data is sampled and determined at many points in accordance with the equation (2), the measurement time must be long. On the other hand, since the space between the head and the disk is becoming narrower due to the improvement in the storage capacity of the magnetic disk device, the flying height is measured for all the heads from the viewpoint of the reliability of the magnetic disk device. For this reason, there is a demand for an inspection apparatus that performs highly accurate measurement in a shorter time. However, the above measurement method cannot meet this demand. In the measurement of the flying height of the head, the values of the reflectances r and s are more accurately determined and measured.
No. application. SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic head flying height measuring device which has a small deviation from the actual head flying height in a magnetic disk device and can perform highly accurate measurement for a head having a small flying height.

[0009]

The magnetic head flying height measuring apparatus of the present invention for achieving the above object is characterized by a single-crystal sapphire transparent disk and a spindle on which the disk is mounted and rotated. A loading mechanism for loading a head onto one surface of the disk, and a photoelectric converter, irradiating light from the other surface of the disk, and reflecting light from the one surface and light from the surface of the head. A measuring optical system that receives interference light with reflected light and converts it into an electric signal by the photoelectric converter, and a processing device that receives the electric signal from the measuring optical system and calculates the flying height of the head. It is provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is based on the fact that the disk for measuring the flying height is made of a single crystal sapphire disk, so that its thickness is made thinner than that of a conventional quartz disk. Is reduced, and the amount of light reflected on the measuring optical system is increased by utilizing the fact that the refractive index is as high as about 1.76. As a result, the intensity of interference light with respect to noise increases, and the weight of the disk is reduced, so that the disk can be rotated at a higher speed than before. In addition,
The refractive index of a conventional quartz disk is 1.46. Since the single crystal sapphire disk has a high hardness, it is formed by growing a plate-like material by a crystal growth method, processing the disk into a disk, and polishing both surfaces thereof with diamond abrasive grains.

The single crystal sapphire used as a disk for measuring the flying height of a magnetic head is mainly made of aluminum oxide (Al ₂ O ₃ ), and its hardness shows a Mohs hardness of 9. On the other hand, the ceramic structure forming the slider surface of the magnetic head (thin film head) is also mainly composed of aluminum oxide, and has a hardness of 9 on the Mohs scale. Therefore, both have the same hardness, and the single crystal sapphire has an effect that the head is less likely to be scratched. On the other hand, since the hardness of quartz glass of the conventional measuring disk is about 7 on the Mohs scale, when the slider surface of the head comes into contact with the quartz glass, the surface of the disk is scratched and damaged due to the difference in hardness between the two. The scratched surface not only makes the flying of the head unstable, but also causes irregular reflection which is detrimental to measurement and causes erroneous measurement. However, by using the single crystal sapphire as described above, a measured value close to the theoretical value of the equation (2) can be obtained.

In particular, since the flying height of a magnetic head of a recent magnetic disk drive is as low as several tens of nm,
The frequency of contact with the disc during measurement is increasing. Therefore, the disk is easily damaged and the disk must be replaced in a short time, which is uneconomical and the measurement efficiency is low. However, the frequency of disk replacement can be reduced by using a single crystal sapphire disk as described above. As a result, measurement errors are reduced, and high-precision measurement is possible.
In addition, the life of the disk is prolonged and the number of replacements can be reduced because the disk is hardly damaged. When the detection value obtained by the single crystal sapphire disk approaches the theoretical value of the above equation (2), the intensity value (measured value) of the interference light of the measuring head is obtained by expanding equation (2) into a graph. The deviation from the theoretical data of the flying height calculated for the relationship between the reflectance R with respect to the obtained wavelength and the flying height h is reduced. Therefore, when the flying height characteristics are expanded on a graph, the relationship between the flying height and the reflectance for a short wavelength has a difference in characteristics, but when the wavelength is short, the design of the optical system becomes difficult, and the cost increases. Parts must be used. In order to perform high-precision measurement with an optical system equivalent to the conventional one, the wavelength is preferably 350 nm or more from the characteristics of the graph of FIG.

That is, in the graph of FIG. 4, the shorter the wavelength, the more the characteristics change, and it is possible to distinguish even a low flying height. However, in the measurement of the flying height here, since the projected light and the reflected light pass through the disc, the shorter the wavelength is, the lower the transmittance is, and the intensity of the reflected light (detected interference light) is reduced due to attenuation in the middle. descend. Therefore, in the present invention, a single-crystal sapphire disk having a smaller thickness than the conventional one is used. However, in practice, at a short wavelength of 350 nm or more, the level of the detected interference light becomes low, and the accuracy is high. The measurement becomes unreliable.

[0014]

FIG. 4 is a graph of a magnetic head showing the relationship between the flying height, the wavelength, and the reflectance in white light obtained according to the above equation (2). The vertical axis is the reflectance R (%), and the horizontal axis is the wavelength λ. Each graph shows the relationship between the reflectance R and the wavelength λ for each flying height h. Looking at the characteristics shown in this graph, in each case, the characteristic is a simple increase or a simple decrease from 350 nm to 800 nm. Therefore, if data matching between the measured value and the theoretical value in each graph characteristic is performed based on this range, it is possible to quickly and accurately determine the flying height h up to a range of 0.1 μm or less. At the same wavelength among the characteristic values, the number of intersections between the characteristic graph of a certain floating value and the characteristic graph of another floating value is small at 400 n.
m, and at 400 nm or less, h = 0.18
There is a peak in the μm graph. Further, for the above-mentioned reason, when the wavelength is shortened, it is difficult to design an optical system for high-precision measurement, and the cost becomes high. In addition, from the viewpoint of the reliability of the measured value, measurement in the range of 350 nm or more is actually appropriate.

When the wavelength is short, it is difficult to determine with high accuracy by simple data matching, and when the amount of comparison data is increased, the efficiency of the processing for determining the flying height decreases. Also, 80
When the thickness is 0 nm or more, the characteristic values of 0.1 μm or less approach each other, and the accuracy of the detected measurement value decreases due to the influence of the complex refractive index. That is, the actual light reflects and refracts not as the surface of the substance but as if it were sunk into the substance and reflected. Therefore, the flying height h is measured to be large. The fluctuation of the detection value increases. Also, the range of the comparison standard is 800
If it is set to nm or more, the amount of comparison data increases, and the processing efficiency decreases.

In the magnetic head flying height measuring apparatus shown in FIG. 1, the disk 5 shown in FIG. 6 is changed from a quartz disk to a single crystal sapphire disk 9 having a thickness of about 1/3. As a result, as described above, the intensity of the detection light (interference light) can be detected at a value close to the theoretical value of Expression (2). In addition, since the weight of the disk 9 is reduced, even if the disk is rotated at a higher speed than in the past, there is less rotation fluctuation, and high-precision measurement is possible. As described above, in order to improve measurement accuracy and processing efficiency, FIG.
In the graph of FIG. 4, a range of wavelengths from 400 nm to 750 nm is selected, and data of about 80 to 180 points are sampled every about 2 nm to about 4 nm, and the data corresponding to this range of FIG. The flying height h of the measuring head is determined by performing data matching with data of a theoretical value data table 73 described later.

For this purpose, FIG. 1 shows a concave diffraction grating 65 for dispersing the analysis range of the concave diffraction grating 65 of FIG. 6 in a larger range including a wavelength range of 400 nm to 750 nm.
a, the number of pixels to be detected by the linear sensor 66 is 256
It is replaced by a one-dimensional CCD sensor 67 bits. Then, these 256 pixels have wavelengths of 400 nm to 750 n.
Light in the range of m is received. CCD sensor 67
Read drive circuit 68 for reading the output of A / D conversion circuit (A / D) 6 for converting the read output to a digital value
9 to the data processing device 70. Here, components similar to those in FIG. 6 are denoted by the same reference numerals. The head loading mechanism 3 is controlled by the data processing device 70.

A data processing device 70 receives data from a microprocessor (MPU) 71 via a bus 75 from an A / D conversion circuit 69 and temporarily stores the data in a memory 72.
Among them, 128 data are sequentially collected at every other pixel from the data corresponding to 400 nm. Data corresponding to the floating value at each wavelength is sequentially matched for each wavelength with respect to data for 128 wavelengths provided from 400 nm to about 2.7 nm in the theoretical value data table 73. The matched data becomes the flying value at that wavelength value. As shown in FIG. 3, the theoretical value data table 73 is a table in which the theoretical values of the respective flying heights are arranged corresponding to each wavelength.

The basic processing of the data matching is to determine which of the theoretical value data table 73 the detected value received at the data of the same wavelength is closest to, and determine the closest flying value to each of them. It is determined for each wavelength. As a result, the most common flying value is obtained as the detected flying value. In addition, when the most levitation value is about 90% or less of the whole, in other words, when it is 115 or less, the retest is performed. As a processing program, a memory 72 is provided with a data matching program 74. Since this processing program is a simple process of simply performing a subtraction operation using the absolute value of data and reading the flying value corresponding to the smallest one, the details are omitted. Further, each data value of the theoretical value data table 73 is:
The theoretical value may be corrected by an actually measured value or an experimental value in consideration of the fluctuation on the measured value side. Alternatively, as a data in a predetermined range, the data may be changed to the closest one, and it may be determined whether or not the value falls within this range, and the flying value within the range may be obtained.

As shown in FIG. 2, the single-crystal sapphire disk 9 is made of a colorless and transparent single-crystal sapphire as a raw material. For the donut-shaped processing, the diameter φd ≒ 30 ~ 1
The disk is a disk having a diameter of 20 mm and a thickness of d ≒ 1.5 to 4 mm, a center hole 9a having a diameter φc of 5 to 20 mm is formed at the center thereof, and both surfaces are formed by polishing diamond abrasive grains with high precision. The numerical examples of the diameters φd and φc and the thickness d are described below.
The optimum values for a 5-inch magnetic disk are φd = 105 mm, φc = 5 mm, and d = 2 mm.

[0021]

As described above, according to the present invention, a single crystal sapphire disk is used as a disk for measuring the flying height, thereby reducing the thickness of the disk from that of a conventional quartz disk. This reduces weight and thickness,
In addition, since the amount of light reflected on the measuring optical system can be increased by utilizing the fact that the refractive index is as high as about 1.76, the intensity of interference light with respect to noise is increased, and the intensity of interference light with a single crystal sapphire disk is obtained. The detected value approaches the theoretical value of equation (2). As a result, the value (measured value) of the intensity of the interference light of the measuring head is calculated from the relationship between the reflectance R with respect to the wavelength and the flying height h obtained by expanding the equation (2) into a graph. And the head flying height can be measured with high accuracy by comparing the data with the logical value.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of a measuring apparatus according to an embodiment to which a magnetic head flying height measuring apparatus according to the present invention is applied.

FIGS. 2A and 2B show the single-crystal sapphire disk, wherein FIG. 2A is a plan view and FIG. 2B is a cross-sectional view.

FIG. 3 is an explanatory diagram of a theoretical value data table.

FIG. 4 is a graph showing the relationship between the flying height, the wavelength, and the reflectance in white light.

FIGS. 5A and 5B are explanatory diagrams illustrating a relationship between a magnetic disk and a head floating from a surface of the magnetic disk. FIG. 5A illustrates a relationship between the magnetic disk and the head, and FIG. FIG. 3C is an explanatory diagram of the structure of the main body, and FIG. 4C is an explanatory diagram of a flying state of the head.

FIGS. 6A and 6B are explanatory views of a conventional magnetic head flying height measuring device, in which FIG. 6A is a basic configuration diagram of the flying height measuring device, and FIG. 6B is a diagram illustrating a method of measuring the flying height h. FIG. 3C is an explanatory diagram of a spectrum pattern with respect to the wavelength of the interference wave.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 2 ... Spindle, 3 ... Head loading mechanism, 4 ... Carriage mechanism, 5 ... Quartz disk,
Reference numeral 6: measuring optical system, 7, 70: data processor, 9: sapphire disk, 31: head, 32: support arm, 3
11: Slider surface, 41: Support member, 61: Xenon lamp light source, 62: Projection lens, 63: Half mirror, 64: Objective lens, 65, 65a: Concave diffraction grating,
66: linear sensor, 67: one-dimensional CCD sensor, 68
... read drive circuit, 69 ... A / D conversion circuit (A / D), 7
1 ... Microprocessor (MPU), 72 ... Memory, 7
3. Theoretical value data table.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-3-291506 (JP, A) JP-A-59-223966 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G11B 21/21

Claims (4)

(57) [Claims] 1. A transparent disk of single crystal sapphire, a spindle on which the disk is mounted and which rotates the disk,
A loading mechanism for loading a magnetic head onto one surface of the disk, and a photoelectric converter, which irradiates light from the other surface of the disk and reflects light from the one surface and the light from the surface of the magnetic head; A measuring optical system that receives interference light with reflected light and converts it into an electric signal by the photoelectric converter, and a processing device that receives the electric signal from the measuring optical system and calculates the flying height of the magnetic head. Magnetic head flying height measuring device comprising: 2. The disk has a thickness of 1.5 mm to 4 m.
The magnetic head flying height measuring apparatus according to claim 1, wherein the magnetic head is a thin film head in a range of m. 3. The measuring optical system according to claim 1, wherein
white light containing a wavelength of 300 nm through the disk.
A projection optical system for irradiating the film head and the thin film head
Of reflected light of 350 nm from the disk
Spectrum component to be dispersed in the range including the wavelength of 800 nm
An optical device, wherein the photoelectric converter has a large number of detected pixels of 1.
Photoelectric conversion elements arranged in a line,
Receiving the light dispersed by the tram spectroscope, the detection pixel
The intensity of light of each wavelength correspondingly split into electric signals
The processor converts the signal from the photoelectric conversion element into a digital value by A / D conversion and converts the digital value corresponding to the detection pixel to a wavelength corresponding to the detection pixel. The magnetic head flying height measuring device according to claim 2, wherein the flying height is calculated by comparing the flying height with a predetermined theoretical value provided. 4. The theoretical value is: In the relationship between the reflectance R and the wavelength λ for each flying height h determined by
m, where δ = 4h /
λ, λ: wavelength, h: flying height, R (λ, h): reflectance at flying height h at wavelength λ, r (λ): reflectance at wavelength λ of glass disk viewed from the air layer, s (λ) 4. The magnetic head flying height measuring apparatus according to claim 3, wherein: the reflectance at a wavelength λ of the thin film head viewed from the air layer.