JPH0268716A - Production of magnetic disk medium - Google Patents

Abstract

PURPOSE:To realize high coercive force and low noise by forming Cr or Cr-alloy base layer by sputtering essentially with perpendicular incidence and a Co-alloy magnetic layer by sputtering with oblique incidence using targets having areas to be eroded. CONSTITUTION:In the method of forming the Cr or Cr-alloy base layer on a substrate 1, and then the Co-alloy magnetic layer thereon, the substrate 1 and a sputtering target 2 are disposed in a still state concentrical and parallel to each other with a distance of 30 - 150mm. In the process of forming the Cr or Cr-alloy base layer, the target 2 is used for sputtering under the conditions that the ring-like eroding region 8 occupies >=80% of the surface area and that the inner diameter of the region 8 is less than 40% of the substrate diameter and the outer diameter is larger than that of the substrate. In the process of forming the Co-alloy magnetic layer, the target 2 has a circular eroding region 9 which occupies <=60% of the surface area and has the tinner diameter more than 80% of the substrate diameter and the outer diameter larger than that of the substrate. Thereby, high coercive force is obtained and noises on recording/reproducing can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a magnetic disk medium, and in particular to a method for manufacturing a magnetic disk medium.
High coercive force (≧11000e) in a magnetic recording medium consisting of a ferromagnetic thin film based on a ferromagnetic alloy and an underlying thin film mainly composed of Cr.
The present invention relates to a method of manufacturing a magnetic disk medium having a high linear recording density and excellent recording and reproducing characteristics with little noise during recording and reproducing.

[Conventional technology]

Recording media for magnetic disks were first put into practical use by coating T iron oxide particles on an Aj' substrate, and a considerable number of them are still in use today, but in recent years, films have been formed by plating and sputtering methods. Continuous media made of ferromagnetic alloys are now being developed. Particularly in the field of small-diameter magnetic disks with a diameter of 5.25 inches or less, the above-mentioned continuous media now account for more than half of the total usage. This trend is becoming more and more popular, and the design policy for small drive devices that use small-diameter magnetic disks is becoming lighter, thinner, and smaller. At the same time, high recording capacity is required, and the linear recording density of magnetic disk media is increasing. is required. The coercive force of conventional mass-produced magnetic disk media is 600 to 7000 for coated media.
800 to 9500e is the mainstream for e, plating and sputtering media, and those in the development stage of 1000 to 15000e are media that can reach the practical level as the output of magnetic heads progresses in the future. Numerous cases have been reported.

Co alloy proposed as a high coercivity magnetic recording medium/
In the Cr sputtering medium, the surface of the NiP/A1 substrate is polished in the circumferential direction with a polishing tape to form a circumferential texture (groove structure), and a Cr layer is first formed thereon. By interposing the Cr layer between the substrate and the Co alloy layer, C
This is because the coercive force of the o alloy layer is improved and the squareness ratio is increased.

In this sputtering of the Cr underlayer, sputtered particles are incident obliquely and the shadowing effect of the texture in the circumferential direction is used to form a thin Cr layer (underlying layer) in a shape along the groove direction, that is, the circumferential direction. Make it grow. Then, particles or particle groups of a Co-based alloy ferromagnetic thin film are deposited on the upper layer using a method that also gives the oblique incidence effect so as to be oriented in the elongated direction along the circumferential direction, thereby creating shape anisotropy in the circumferential direction. Magnetic disk media with strong uniaxial magnetic anisotropy based on the above are in practical use. The texture in the circumferential direction is formed to minimize wear and damage on the media surface due to contact between the head slider and the disk media, and this texture is used to create shape anisotropy in the magnetic layer as described above. This gives high magnetic anisotropy in the circumferential direction.

[Problem to be solved by the invention]

In magnetic disks such as those described above, high coercive force and high angularity are achieved by forming a circumferential texture and a Cr underlayer. A ferromagnetic thin film having strong uniaxial magnetic anisotropy in the circumferential direction is formed. An example of magnetic history curves in the circumferential direction and the radial direction of such a magnetic disk is shown in FIG.

In such a medium, the intrusion of the magnetic domain structure in the magnetization transition region during magnetic recording becomes complicated, which may cause noise generation during reproduction.

Furthermore, in the conventional structure, in order to obtain a high coercive force (≧11000e), it is necessary to increase the aspect ratio of the magnetic thin film in order to further strengthen the shape anisotropy, and therefore the groove spacing on the substrate must be narrowed. However, this is undesirable because it causes a decrease in the C3S (contact start/stop) performance of the magnetic disk and impairs mass production efficiency.

Therefore, an object of the present invention is to provide a high-performance magnetic recording medium with high coercive force (≧11000e) and low noise in response to the increasing density of magnetic recording media.

[Means to solve the problem]

In order to achieve the above object, the present invention forms a Cr or Cr alloy underlayer on a substrate, forms a CO alloy magnetic layer thereon, and further forms a nonmagnetic layer thereon as necessary. A method of manufacturing a magnetic disk medium by forming a carbon film or the like is provided. In this method, a Cr or Cr alloy underlayer and a Co
The base material of the alloy magnetic layer and the spaft target material are 30 to 15
The film is formed by sputtering by arranging them in a stationary state in parallel in concentric circles at an interval of preferably 40 to 110 mm, and forming the film by sputtering.
When forming an r or Cr alloy base layer, the target has an annular eroded area that is 80% or more of the surface area, and the inner diameter of the annular eroded area is 40% or less of the substrate diameter and the outer diameter is the substrate diameter. The above C
o When forming the alloy magnetic layer, the target must have an annular eroded region of 60% or less of the surface area, and the inner diameter of the annular eroded region is 80% or more of the substrate diameter and the outer diameter is larger than the substrate diameter. Sputter film deposition under these conditions.

The feature of this method is that using a target with the above-mentioned corroded area, the Cr or Cr alloy underlayer is mainly formed by vertical incidence sputtering, and the Co alloy magnetic layer is formed by sputtering at an angle. The purpose of this method is to perform sputtering film formation using incident radiation.

By depositing the Cr or Cr alloy base layer by vertical incidence sputtering, the Cr or Cr alloy base layer develops into a columnar shape.
and a body-centered cubic lattice (BCC) of Cr particles in the gerontological plane.
The (110) plane of the crystalline phase develops.

When a Co alloy magnetic layer is epitaxially grown on a well-grown Cr or Cr alloy underlayer in this manner, the Co alloy grows in such a way that it is further layered on top of the well-grown Cr or Cr alloy particles, and the film surface is The curved or open portions of the crystals grow as independent crystals that are more accentuated. The magnetic layer thus obtained has a high coercive force and no anisotropy (shape and magnetic anisotropy), making it suitable as a high-density recording medium as it has a high coercive force and reduces noise during recording and reproduction. .

Incidentally, C of the magnetic disk medium obtained by the method of the present invention
o The structure of the alloy magnetic layer is not limited, but the structure observed from the direction perpendicular to the film surface has an average grain size of 1100 nm.
It is an aggregate of the following particles, and the average size of the unevenness in the direction perpendicular to the germinating surface formed by the individual particles is less than or equal to the above average particle size, and the particles are adjacent to each other. It can be said that the structure is separated from the particles by a distance of at least 0.5 nm. And coercive force Hc
It is possible to manufacture a magnetic disk having an anisotropy of 11000e or more and a ratio between the circumferential squareness ratio and the radial squareness ratio within the range of 0.8 to 1.1.

Further, as for noise characteristics, a ratio (-dB) of noise to signal output at a recording/reproducing frequency of 5 MHz can be achieved at 35 or more.

A typical manufacturing method of the magnetic disk medium of the present invention will be described. Figure 1 is a schematic diagram of a sputtering apparatus, Figures 2 and 3 are diagrams explaining the conditions for sputtering a Cr or Cr alloy layer and a Co alloy layer, respectively, and Figure 4 is a schematic diagram of a typical magnetic disk. It is a diagram.

In FIG. 1, a substrate 1 and a target 2 are connected to a sputtering chamber 3.
They are arranged in parallel inside each other so that high frequency power or DC power 4 can be applied thereto. In the case of a magnetron sputtering device, the cathode 5 below the target 2 is configured as a high-speed magnetron electrode.

A magnetron sputtering device is most suitable for the method of the present invention in order to define the annular eroded region as described above. The sputtering chamber 3 is evacuated 6, and a shutter 7 is provided between the substrate 1 and the target 2.

The substrate 11 is made of A1 alloy or pure A! is typical, but it may also be made of hard plastics such as polycarbonate and polyethylamide. Although the dimensions of the substrate are not particularly limited, the present invention is particularly advantageously applied to small disks such as 5 inches and 3.5 inches. The thickness is usually 1.2 to 1.
It has about 9 fins and has a mirror-finished surface.

Preferably, a base plating layer 12 such as Ni-P is formed on the surface of the substrate 11 by electroless plating to a thickness of 10 to 2.
Form about 0 side. Furthermore, on this base plated substrate, a tape polishing method or the like is applied to form a substantially concentric circle (or a spiral shape).
A texture (a structure) is formed. This is necessary to give buoyancy to the head when the disk rotates, and expressed in terms of surface roughness, preferably a maximum surface roughness R- of 400 to 550 and an average surface roughness R of 160 to 80. If the surface roughness is too large, the flying ability of the head will be poor, while if the surface roughness is too small, the media and head will be subject to severe wear and damage due to contact with the head.

A Cr or Cr alloy underlayer 13 is formed as an intermediate layer for epitaxially growing the CO alloy magnetic layer 14 on the underplating layer 12 having a concentric texture. It is known that in the sputtering method, crystals grow with the (110) plane oriented parallel to the substrate surface, resulting in a column-shaped cross-sectional structure. In the present invention, when forming this Cr or Cr alloy base layer 13 by sputtering, the incidence is mainly perpendicular to the substrate 11. To this end, referring to FIG. 2, a Cr or Cr alloy target 1 is placed in a sputtering chamber 3 facing a substrate 2 that has undergone undercoat plating and texture formation, and is placed in a sputtering chamber 3 for 30-150 mm, preferably 40 mm, depending on the dimensions of the substrate. ~
Annular erosion areas of the target 1 (areas of the target that are eroded because target constituent materials fly out when the target is sputtered) 8 are arranged at intervals of about 110 fl.
The film is formed under sputtering conditions that satisfy the following conditions.

That is, the inner periphery of the eroded region 8 is within 40% of the radius from the center of the substrate 2, the outer periphery of the eroded region 8 is outside the outer periphery of the substrate 2, and the entire area of the target (the surface facing the substrate) is The area of the eroded region 8 is 80% or more of the area (area). This causes the Cr or Cr alloy to be incident substantially perpendicularly to the substrate, allowing the (110) plane of the Cr or Cr alloy to grow more completely. The sputtering conditions may be within the commonly used range, such as an argon pressure of 1 to 1 liters.
Q flTorr, the electric power is good for about 2 to 10 km. C
The thickness of the r or Cr alloy base layer 13 is 1000 to 3000
A range of people is preferred. The coercive force of the Co alloy magnetic layer 14 tends to increase as the thickness of the Cr or Cr alloy underlayer 13 increases, but it eventually reaches saturation, so the thickness within the above range is required to obtain the desired effect. suitable.

After forming the Cr or Cr alloy underlayer 13, the CO alloy magnetic layer 14 is formed. A typical Co alloy magnetic material is Co −
Consisting of Ni-Cr, Ni 10-30 atm%, Cr
It is 5 to 10 atm%. It is known that a Co alloy magnetic layer formed on a Cr or Cr alloy underlayer has a high coercive force and a high recording density. After forming a film by sputtering with C, a film was formed by sputtering with oblique incidence using a narrow erosion target as shown below.

The alloy is grown as a stand-alone product corresponding to the Cr or Cr alloy substrate. Referring to FIG. 3, the term "narrow erosion target" means that at a distance between target 1 and substrate 2 of 40 to 110 μl, the inner periphery of the annular erosion area 9 of target 15 is 80 mm in radius from the center of substrate 2. % and inside the outer periphery of the substrate 2, the outer periphery of the erosion region 9 is outside the outer periphery of the substrate 2, and the area of the erosion region 9 with respect to the total area of the target 1 is 60% or less. The sputtering conditions may be the same as those for Cr.

By combining such oblique incidence with the above-mentioned perpendicular incidence C or Cr alloy underlayer, a magnetic disk medium with high coercive force, high density recording characteristics, and low noise characteristics can be realized. , C by a combination of such film-forming methods.

This is thought to be because the alloy layer grows well as an independent crystal, and a Co alloy magnetic layer without magnetic anisotropy is formed. As described above, this Co alloy magnetic layer 14 has an average particle diameter of 1100 nm or less in the Nariko plane, an average of the unevenness perpendicular to the Nariko plane is smaller than the average particle diameter, and individual particles in the Nariko plane. This results in a structure in which the particles are separated by at least 0.5 nm. This is because the Co alloy magnetic layer 4 deteriorates even more.

A protective film 5 is formed on the Co11 layer 4, if necessary. As this protective film, a carbon vapor deposited film (3QO~
400 people) and a perfluoropolyether film (2
0 to 40 people) etc. are usually used.

〔Example〕

Examples of the present invention will be described in detail below.

NiP plating (18 to 20 m thick) was applied to an A1 substrate having an outer diameter of 13011φ, an inner diameter of 40u+φ, and a thickness of 1.90m, and the NiP plating layer was mechanically polished in about 3 directions to give a mirror finish. [Texture processing has an average roughness (R,) of 20~
30 people, and the maximum roughness (R□) is about 100 to 200 people] On such a magnetic disk substrate, a base layer (Cr metal thin film) is coated to a thickness of 1000 to 1000 by sputtering.
A film is formed to a thickness of 3000 nm. The film forming conditions are Ar gas pressure of 3 to 10 mTorr (preferably 6 mTorr).
), a DC power of 2.5 to 6 KW, a distance of 70 mm between the target and the substrate (T/S), and the circular target and the substrate are stationary and facing each other in a concentric position.

The cathode of this target (diameter 200nφ) has an annular eroded area of 85% and its inner diameter is 30% of the center diameter of the substrate surface, and it appears that the majority of the components are flying perpendicularly toward the substrate surface. A cathode designed in this way was used.

Next, Co 30 atm%Ni -7,5 was applied on the base layer.
An atm% Cr alloy magnetic layer is formed by sputtering. In forming this alloy magnetic layer, the film forming conditions are Ar gas pressure of 3 to 10 mTorr (preferably 6 mTorr).
r), DC power is 2.5 to 6 KW, T/S distance is 50 Yen, and the circular target and the substrate are stationary and facing each other in concentric positions. The cathode of the target (diameter 20 (bmφ)) was designed so that the annular eroded area was 40% and the center diameter was 80% or more of the substrate diameter.

In this way, films were formed while changing the substrate temperature and each film thickness as shown in Table 1, and a magnetic disk was manufactured.

FIG. 5 shows a backscattered electron image of the surface structure of the magnetic disk obtained by such a method, which was observed using a scanning electron microscope (Model S-900, manufactured by Hitachi, Ltd.). It can be seen that the Co alloy particles are growing independently.

The average particle size of Co alloy particles is 20 nm, and the average particle gap is 1
It was distributed in 0.5-5nI11 in nm. The unevenness in the direction perpendicular to the film surface of the Co alloy particles was investigated by the cross-sectional structure, and
It was 10 nm.

For comparison, a magnetic disk similar to that of the above example was fabricated, except that the Cr underlayer and Co alloy magnetic layer were formed under conventional film formation conditions (both oblique incidence) to create anisotropy in the circumferential direction. Granted.

FIG. 6 is a photograph similar to FIG. 5 showing the surface structure of the magnetic disk of this comparative example. Co alloy particles are not independent,
It is somewhat small, and it can be seen that the spaces between the particles are also densely filled with Co alloy.

The magnetostatic force characteristics, recording/reproducing characteristics, frequency characteristics, and noise characteristics of the magnetic disks of these Examples and Comparative Examples were evaluated. The magnetostatic force characteristics were measured using a VSM (vibrating sample magnetometer), and the recording and reproducing characteristics were measured using a spectrum analyzer.

The measurement conditions include a frequency range of 0 to 10 MHz.
up to z; resolution frequency is 30Kt (z, noise ratio measurement input signal 5MHz; measurement head is monolithic metal-in-gap (MIG) head, track width TW = 1.6m
+, gap width GL = 0.7 feet; measurement position is 30.4 mm from the disk center, disk rotation speed is 360
0 rpm; write current was 35m8.

Table 1 shows the results.

Explanations of l) to 14) in Table 1 are given below.

1) Coercive force Hc (Oe): Shows the value measured in the circumferential direction of the disk. 10000e
The above is the goal, and the higher this value is, the higher the recording density can be.

2) Residual magnetic flux density Br·δ (G·μ): Here, the residual magnetic flux density Br was evaluated by multiplying the film thickness δ, so it has a unit of (Gauss)×(micrometer). The larger this value is, the greater the output is, which is preferable.

3) Magnetic anisotropy (Br/Bs/(Br/Bs)
': Measure the residual magnetic flux density Br/saturation magnetic flux density BsO ratio (square ratio) in the circumferential direction and the radial direction, respectively,
Magnetic anisotropy was evaluated based on the ratio. The closer this value is to 1, the more isotropic it is. As will be described later, it has been confirmed that the more isotropic the material is, the less noise it produces, which is preferable.

4) Outer periphery OR: The position 60.91 m from the center of the disk with an outer diameter of 130 φ was defined as the outer periphery (0 (1j6rradius)).

5) Inner radius ■R: The position 30.4 ml from the center of the disk with an outer diameter of 130 nφ was defined as the inner radius.

6) Track average output TAA LFI (mV): 1
．． 25M1! Trunk average power of the signal (LFI) of z.

7) Track average output TAA HFI (mV): 2
．． Track average output of 50M1lz signal (HFI).

8) Resolution RES (%): Displays TAA HF + / TAA LF I as a percentage. The larger this value is, the closer it is to 100%)
It can be said that the smaller the TAAO difference between , LF, and IIF, the better the resolution.

9) O/W (-dB) for overwriting characteristics: When reproducing the output when recording an LFI signal and then recording an HFI signal on top of it, the ratio of the later signal to the previous signal. Evaluate as. The larger the absolute value of this value is, the better the overwriting characteristics are.

10) 70% attenuation frequency. : Frequency at which the output is 70% of the output of a solitary wave (0.75 MHz) (see Figure 1O).

11) D? . Linear recording density LD (KFCPI) :D
Linear recording density for a frequency of 7°. The unit is the number of magnetic flux reversals per inch (Kilo Flux Change).
PerInch).

12) 50% attenuation frequency. : Frequency at which the output is 50% of the output of a solitary wave (0.75 MHz) (see Figure 10).

13) Ds. Linear recording density LD (KFCPI) :D
Linear recording density for a frequency of 5°.

14) Noise ratio 5NR15,0Mtlz (-dB)
:5, QMHz is a logarithmic representation of the signal-to-noise ratio at the output of the signal; the larger the value, the smaller the noise.

FIG. 7 shows magnetization history curves in the circumferential direction and the radial direction of the magnetic disk of Example (Sample 2). When compared with the corresponding magnetization hysteresis curve of the comparative example (sample 1) shown in FIG. 8, it can be seen that the magnetic disk of the present invention does not have anisotropy but has a large coercive force.

Figure 9 shows the output in terms of frequency when a 5 MHz signal is not input to the magnetic disk of the example (sample 2) and when it is input, and Figure 9 is a corresponding diagram of the comparative example (sample 1). It is. Comparing these figures, it can be seen that with a conventional anisotropic magnetic disk, when a signal is input, the medium noise component increases significantly in the low frequency region, but with the isotropic magnetic disk of the example, when a signal is input Sometimes, the increase in media noise components is small.

FIG. 11 shows the frequency characteristics of the output of the magnetic disks of the embodiment (sample 2) and the conventional example (sample 1). From the figure, it is recognized that the output of the comparative example decreases more quickly as the frequency increases than the example.

〔Effect of the invention〕

According to the method of the present invention, there is provided a magnetic disk medium in which a Co alloy magnetic layer is formed on a Cr or Cr alloy underlayer on a substrate, which has a high coercive force (11000e or more) and suppresses noise during recording and reproduction. A magnetic disk medium useful for increasing recording density can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a sputtering apparatus for carrying out the method of the present invention, FIG. 2 is a diagram illustrating the deposition conditions for a Cr or Cr alloy underlayer, and FIG. 3 is a diagram explaining the deposition conditions for a Co alloy magnetic layer. 4 is a schematic diagram showing the structure of a magnetic disk according to an example of the present invention, and FIGS. 5 and 6 are electron micrographs of the metal structure of the Co alloy magnetic layer of the magnetic disk of the example and comparative example. The photographs, Figures 7 and 8 are circumferential and radial magnetization antinode curves of the magnetic disks of the example and comparative example, and Figures 9 and 10 are the noise characteristics of the magnetic disks of the example and comparative example. FIG. 11 is a diagram showing the frequency characteristics of the output of the magnetic disks of the example and the comparative example. ■...Substrate, 2...Target, 3
...Annular erosion area, 4.High frequency power source, 5.
... Cathode, 6... Vacuum system, 7... Shutter 11... Substrate, 12... Base plating layer, 13... Cr or Cr alloy base layer, 14... Co alloy magnetic layer, 15...Protective film.

Claims (1)

[Claims] 1. Form a Cr or Cr alloy underlayer on a substrate, form a Co alloy magnetic layer on top of it, and further form a nonmagnetic layer, carbon film, etc. on top of it as necessary to form a magnetic disk. In the method for manufacturing a medium, the Cr or Cr alloy underlayer and the Co alloy magnetic layer are separated from the substrate and the sputtering target by 30 to 30°C.
When forming the Cr or Cr alloy base layer by sputtering the film by placing it stationary in parallel at concentric circles with an interval of 150 mm, the target has a surface area of 80% of the surface area.
The Co alloy magnetic layer is formed by sputtering under the conditions that the annular eroded area has the above-mentioned annular eroded area, and the inner diameter of the annular eroded area is 40% or less of the substrate diameter, and the outer diameter is larger than the substrate diameter. In this case, the sputtering film must be formed under the conditions that the target has an annular eroded area of 60% or less of the surface area, the inner diameter of the annular eroded area is 80% or more of the substrate diameter, and the outer diameter is larger than the substrate diameter. A method of manufacturing a magnetic disk medium characterized by: