JP2640892B2 - Measurement method of flying height of magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a flying height of a magnetic head, and more particularly to a method for measuring a small flying height of a thin film head.

[0002]

2. Description of the Related Art FIG. 3A illustrates the operation of a floating head (hereinafter simply referred to as a head) for a magnetic disk. A magnetic disk 1 is mounted on a spindle 2 and rotates. Is attached to the tip of the support arm 32 to form the head assembly 3. The rear end of the support arm 32 is a support member provided on the carriage mechanism 4.
The head 31 is fixed to 41 and moved by the carriage mechanism 4 to be loaded on the magnetic disk 1. (b) shows the shape of the head 31, a slider surface 311 is formed on the bottom surface, and the slider surface 311 flies above the surface by the air flow generated by the rotation of the magnetic disk 1, as shown in (c), Data is accessed for a predetermined track. Since the flying height h is extremely important for the operation of the head, it is measured and inspected by a head flying height measuring device.

FIG. 4 shows an outline of a head flying height measuring apparatus based on a white light interference wave method. In FIG. 4A, a transparent disk (hereinafter simply referred to as a disk) 5 made of quartz glass or the like is used for testing. This is mounted on the spindle 2 and rotated, and the head 31 is loaded on the back surface 52 of the disk 5 and floats. Measuring optical system 6 above disc 1
And a wavelength band (λ _a) from the light source 61 of the xenon lamp.
White light L _T of to [lambda] _b), the light projecting lens 62 and the half mirror 6
The light is projected on the disk 5 by the objective lens 64 via the third lens 3.
Although white light L _T some by surface 51 and rear surface 52 are reflected predominantly illuminates the slider surface 311 passes through. Here, as shown in (b), the reflectances of the front surface 51, the back surface 52 and the slider surface 311 are respectively q, r, s, and the reflected light is R _q , R _r , R _s , respectively. The reflected light R _r and R _s interference to cause interference wave R _rs each other, are spectroscopy reached concave diffraction grating 65 is transmitted through the half mirror 63. However,
The use of white light and the thickness d of the disc 5
By being much larger, the reflected light _Rq and the reflected light R
The mutual interference of _r and R _s is very small and negligible. The above-mentioned interference wave _Rrs is received by the linear sensor 66, and a pattern signal of the spectrum exemplified in (c) is output. In (c), assuming that the horizontal axis is the wavelength λ and the vertical axis is the intensity I _{rs of the} interference wave,
For example, peak points p ₁ , p ₂ and p ₃ are formed at wavelengths λ ₁ , λ ₂ and λ ₃ . Here, _{assuming that} the phase angle between the reflected lights R _r and R _s is δ, there is the following relational expression among the phase angle δ, the flying height h, and the wavelength λ. δ = 4πh / λ, (λ : λ a ~λ b) ......... (2) Equation (1) forms a strength I _rs is a peak point at the wavelength lambda of the phase angle [delta] is an odd multiple of [pi. Now, assuming that the phase angles δ of the respective peak points with respect to the wavelengths λ ₁ , λ ₂ ... Are δ ₁ , δ _2, ..., Δ ₁ = 4πh / λ ₁ ,. ₂ = 4πh / λ ₂ (4) Since δ ₁ −δ ₂ = 2π, the following equation is obtained. _{h = λ 1 λ 2/2} (λ 2 -λ 1) ......... (5) at least by the. above, the wavelengths lambda ₁ for two peak points p _1, p _2, as long sought lambda ₂ is of the formula The flying height h can be calculated by (5).

The above is a case where the flying height h is relatively large, and there are a plurality of peak points in the pattern signal. However, in a high-density recording head, the flying height h is on the order of submicron and is 0.1 μm. It is necessary to measure a micrometer or less with high accuracy, and a peak point may not appear at such a small flying height h. For example, the flying height h
It was a 0.05 .mu.m, 0 the minimum wavelength lambda _a white light L _T.
Assuming 4 μm, h <λ _a / 4 and therefore δ <π, and
As shown in FIG. 4D, no peak point appears in the wavelength band (λ _{a to} λ _b ), and the wavelength λ _s smaller than the wavelength λ _a gradually falls as a virtual peak point p ′. Therefore, the measurement method using the peak point described above cannot be applied to a low flying head. On the other hand, an effective flying height measuring method has been devised by the inventor of the present invention, and a patent application for "Japanese Patent Application No. 4-072439, Flying amount measuring method of magnetic head" has been filed. Less than,
The outline will be described. The intensity I _rs of the interference wave R _rs is represented by the following theoretical formula. I _rs = (r ² + s ² -2rs · cos δ) / (1 + r ² s ² -2rs · cos δ) (1) Here, the reflectances r and s are separately measured and are known. In advance, an appropriate step interval Δh with respect to the flying height h is used as a parameter, and the phase difference δ with respect to these is expressed by the above equation
(2), and this and the reflectances r and s are put into equation (1), and the intensity I _rs for the parameter Δh is calculated in the wavelength band (λ
_a to [lambda] _b) is calculated with an appropriate plurality of wavelengths λ in, creating a large number of comparison patterns. On the other hand, the measured patterns are compared, and the flying height h is obtained from the parameter Δh when they are matched.

[0005]

The reflectance r of the transparent disk is always the same at the time of measurement, so that a correct value can be obtained by published data or a separate measurement. Is different depending on the material of the measuring head, it is necessary to register the reflectance s for each measuring head. Further, the reflectivity differs depending on the angle of the incident light and the like, and the actual value in the flying height measuring device may be different. Therefore, such a reflectance s is given by the following equation.
It is inevitable that the comparison pattern calculated by substituting (1) is uncertain, and a correct flying height cannot be obtained. On the other hand, it is necessary to obtain a proper, so-called true reflectance s for the levitation measuring device by some method, and thereby accurately measure the levitation amount. The present invention has been made in view of the above, and has as its object to provide a method for determining the true reflectance s of the slider surface 311 and thereby accurately measuring the minute flying height h of the low flying head. .

[0006]

SUMMARY OF THE INVENTION The present invention relates to a method for measuring the flying height of a magnetic head. In the above-described head flying height measuring apparatus, a transparent disk is rotated at two appropriate different rotational speeds by preliminary measurement. , A spectrum pattern for _a wavelength band (λ _{a to} λ _b ) at each rotation speed is detected. For the theoretical expressions (1) and (2), the intensity I _{rs of the} spectral pattern detected as described above, the disk reflectance r measured by a separate reflectance measuring device, and the temporary slider reflectance (fixed) Value) s, and provisional flying heights h _F1 and h _F2 for the two types of rotation speeds are calculated. Note that h _F1 and h _F2 obtained here have a measurement error because the slider reflectance s is not a true value. Further, the intensity I _rs , the disk reflectivity r, and the temporary flying height h _F1 ± measurement error range, h
The flying height in the range of _F2 ± measurement error is given to the theoretical formula, and a slider reflectance curve with respect to the wavelength is obtained for each flying height. The reflectance curves for the two flying heights h _F1 group and h _F2 group are compared, a reflectance curve showing the same reflectance is selected between the groups, and the reflectance is calculated as the true reflectance s of the slider surface.
_r . In this measurement of the flying height, the transparent disk is rotated at a specified rotation speed to detect a spectral pattern, and its intensity I _rs and true reflectance s _r are substituted into a theoretical formula to correctly calculate the flying height at the measured rotation speed. The quantity h _r is calculated.

[0007]

In the above flying height measuring method, first, preliminary measurement is performed, and the transparent disk is rotated at two different rotation speeds, and respective spectral patterns are detected. formula
Given the intensity I _rs , the disk reflectivity r and the temporary slider reflectivity s measured separately,
The temporary flying heights h _F1 and h _F2 are calculated based on (1). In addition,
The reason why both the flying heights h _F1 and h _F2 are provisional is that the reflectance s given in Expression (1) is incorrect. Next, the intensity I _rs , h _F1 −n to h _F1 + n, h _F2 −n to h _F2 + n (n is a measurement error range) centered on the respective temporary flying heights, and separately measured. The reflectance r is given to a theoretical formula, and a plurality of reflectance curves with respect to the wavelength of the reflectance s of the slider surface are obtained. The reflectance curves for the two flying height groups h _F1 and h _F2 are compared, and a reflectance curve showing the same value is selected. Originally, the reflectance s is independent of the flying height h. Therefore, regardless of the two flying heights h _F1 and h _F2 , the reflectance curve showing the same reflectance is the true reflectance s _r.
Is shown. In this measurement, the transparent disk was rotated at a specified number of rotations to detect a spectral pattern, and its intensity _Irs
And the true reflectivity s _r are substituted into a theoretical equation to calculate a correct flying height h _r at a specified rotation speed.

[0008]

FIG. 1 is a schematic block diagram of a flying height measuring apparatus according to an embodiment of the present invention. FIG. 2 is a schematic flowchart of data processing.
It consists of the preliminary measurement of (a) and the main measurement of (b). In FIG. 1, the transparent disk 5, the thin film head 31, and the measuring optical system 6 are the same as those in FIG. 4 (a), and the spindle 2 has a variable rotation speed. Data processing unit 7
Are the spectrum pattern generator 71, the memory A721, and the memory B
721, C771, D772, temporary flying height calculation unit 73, changeover switches 741, 742, reflectance calculation unit 75, reflectance curve creation unit 76, curve comparison selection unit 78, and true flying height calculation unit 79
Are connected as shown in the figure. Although some of the above-described units can be configured by a hardware circuit, here, each unit is configured by a program of a microprocessor.

A method of measuring the flying height of the low flying head will be described with reference to FIGS. In the measurement, the above-mentioned theoretical formulas (1) and (2) are used, but these are not described again here.
In FIG. 1, the disk 5 is mounted on the spindle 2,
This head 31 is loaded against the white light L _T than the light source 61 wavelength band (λ _a ~λ _b) is irradiated. In the preliminary measurement, first, the disk 5 is rotated at an appropriate first speed different from the specified speed (step [1] in FIG. 2A).
). As described above, the interference wave R _rs is spectrally separated by the concave diffraction grating 65 and received by the linear sensor 66.
Thus, a pattern signal is output. The pattern signal is input to the spectrum pattern generation unit 71 and the wavelength band (λ _{a to} λ
_b ) a spectral pattern P ₁ (λ) is generated
[2], and temporarily stored in the memory A721 [3]. The temporary flying height calculation unit 73 gives the intensity I _rs of the pattern P ₁ , the correct reflectance r obtained by a separate measurement, and the uncertain reflectance s to the equation (1). (the n range of measurement error) flying height h _F1 -n~h _F1 + n of the plurality of temporary ₁ is calculated [4]. Calculated h _F1 and intensity I _{rs of} pattern P ₁
Is input to the reflectance calculation unit 75 via the switch 741 and the expression (2)
H _F1 -n~h _F1 + plurality of phase angle with respect to n [delta] is calculated, a plurality of reflectance s ₁ (lambda) is calculated for h _F1 by followed Equation (1) [5] by. In yet reflectance curves creation unit 761, s ₁ (λ) from the family of curves Q ₁ is created comprising a plurality of reflectivity curve for the lambda variable [6], is stored in the memory C771 through the switch 742. Next, the disk 5 is rotated at a second speed different from the first speed [7],
Switches 741 and 742 are switched, and steps [8] to [12]
Performs the same processing as described above to obtain the reflectance s ₂ (λ)
, A reflectivity curve group Q ₂ for
772. Both memory C, curves Q _1, Q ₂ to which is stored in the D are compared in the curve comparison and selection unit 78, reflectance curves showing the same reflectance is chosen [13], pursuant to the above, the reflectance Is the true reflectance s _r (λ). Thus, the preliminary measurement is completed, and a proper reflectance of the slider surface 311 is obtained. In this measurement, the disk 5 is rotated at a specified number of revolutions [15], and a spectrum pattern P _r (λ) is generated by the pattern generator 71 in the same manner as described above.
[16]. And intensity I _rs of the pattern P _r, enter the true reflectance s _r which is example by pre-measuring the (lambda) in the correct flying height calculation unit 78, I _rs of the theoretical formula, s _r, giving r performs arithmetic processing, the correct flying height h _r is calculated with respect to the specified speed [17]. The arithmetic processing in this case is performed by the measuring method according to the above-mentioned patent application.

[0010]

As the above description, in the flying height measurement method according to the invention, the preliminary measurement, determine the true reflectance s _r of the slider surface of the measuring head, in this measurement, the true reflectance s _r Is applied to the theoretical formula to calculate the correct flying height h _r at the specified number of rotations, and one of the factors that contributes to the measurement of the minute flying height of the measuring head is large.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a flying height measuring apparatus according to an embodiment of the present invention.

FIG. 2 shows a schematic flowchart of data processing with respect to FIG. 1, wherein (a) is a part for preliminary measurement and (b) is a part for main measurement.

3A is an explanatory diagram of an operation of the thin film head with respect to a magnetic disk, FIG. 3B is an external view of the thin film head, and FIG. 3C is an explanatory diagram of a flying height of the thin film head.

4A and 4B are explanatory diagrams of a head flying height measuring device using a white light interference wave method, wherein FIG. 4A is a schematic configuration diagram, FIG.
FIG. 3C is a curve diagram illustrating a change in the spectrum pattern of the interference wave, and FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Magnetic disk, 2 ... Spindle, 3 ... Head assembly, 31 ... Thin film head, 311 ... Slider surface, 32 ... Support arm, 4 ... Carriage mechanism, 41 ... Support member, 5 ... Transparent disk, Simply disk, 51 ... Surface , 52 ... back, 6 ...
Measurement optical system, 61: light source, 62: light projection lens, 63: half mirror, 64: objective lens, 65: concave diffraction grating, 66: linear sensor, 7: data processing unit, 71: spectrum pattern generation unit, 721 ... Memory A, 722 Memory B, 73 Temporary flying height calculator 741,742 Changeover switch 75 Reflectance calculator 76 Reflectance curve group generator 771 Memory C 772
... Memory D, 78 ... Curve comparison / selection unit, 79 ... Correct flying height calculation unit, [1] to [14] ... Step numbers of the preliminary measurement flowchart, [15] to [17] ... Step numbers of the main measurement flowchart .

Claims (1)

(57) [Claims] 1. A white light L of _a wavelength band (λ _{a to} λ _b ) transmitted through the transparent disk and applied to a slider surface of a magnetic head which is loaded on the back surface of the transparent disk and floats by the rotation of the transparent disk. projecting the _T, and the reflected light R _r of the rear surface of the transparent disk, the reflected light R of the slider surface
_In a head flying height measuring device for measuring the flying height h of the magnetic head based on a spectral pattern detected by spectrally dispersing the interference wave R _rs with _s using a concave diffraction grating, Rotate at appropriate two or more rotation speeds, detect the spectrum pattern at each of the rotation speeds, and determine the intensity I _{rs of the} spectrum pattern for the detected two or more rotation speeds and the known back surface of the transparent disk. The reflectivity s of the slider surface is derived from the reflectivity r. In this measurement of the flying height, the intensity I of the spectral pattern detected by rotating the transparent disk at a specified number of rotations is used.
_rs and, and calculates the correct flying height h _r of the measurement rotational speed by a reflectance s obtained in the preliminary measurement, the flying height measurement method of the magnetic head.