JPH0822616A - Magnetic disk using nonmetallic substrate - Google Patents

Abstract

PURPOSE:To obtain a magnetic disk reducing noise generated from a magnetic film and is suitable to an MR type magnetic head. CONSTITUTION:A multilayered precoating film consisting of a nonmagnetic metallic precoating film 2 and a precoating film 3 formed by plasma CVD is formed on a nonmetallic substrate 1 for a magnetic disk, and a Cr under film 4, a Co-based magnetic film 5 and a protective film 6 are further formed. Since the surface roughness Rp of the magnetic film is reduced, e.g. to <=10nm, disk noise can be reduced and high density recording at >=600Mb/in<2> surface recording density is enabled by combining the resultant magnetic disk with an MR type head. The diffusion of elements included in the nonmetallic substrate to the surface of the disk can be prevented by coating with the precoating film formed by CVD film and the corrosion resistance of the disk is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic disk using a non-metal substrate such as a glass substrate, and more particularly to a magnetic disk using a non-metal substrate for reducing noise from a magnetic film.

[0002]

2. Description of the Related Art Generally, a substrate of a magnetic disk used in a magnetic disk device is roughly classified into a NiP (nickel-based) substrate or a non-metallic glass substrate. The NiP
A magnetic disk using a substrate is a disc-shaped Al (aluminum) alloy substrate with a thickness of several microns to several tens of microns.
It is general that NiP plating is performed, both sides of the plated surface are polished to form a magnetic disk substrate, and an underlayer, a magnetic film, and a protective film are laminated on the substrate. Magnetic disks using a glass substrate are generally classified into tempered glass type and crystallized glass type depending on the glass material. The magnetic disk using the crystallized glass is formed by laminating the magnetic layer and the like, and a glass base material in which fine crystal grains of glass are bonded by an amorphous glass material is cut into a disk shape, and the surface is formed. Is polished to obtain a magnetic disk substrate, and a magnetic layer and the like are laminated on the substrate as described above.

Further, generally, the functions required of a magnetic disk are that the recording characteristics as a recording film are high, the reliability is high with respect to a low flying height of the magnetic head, and the magnetic head is stationary on the disk surface. Is not adsorbed on the disk surface due to moisture in the air. A magnetic disk using a NiP substrate to achieve the function, by performing a texture processing to form fine processing marks in the circumferential direction on the NiP substrate surface, to form a minute protrusions on the NiP substrate surface. It is known to avoid the adsorption phenomenon between the disk and the head. In the case of a magnetic disk using the glass substrate, the glass substrate itself has excellent smoothness, so that a protrusion having a height of several tens nm is provided on the substrate, or a height of several tens nm after forming the magnetic film. The attraction phenomenon between the disk and the head is avoided by providing a protective film having a roughness of 1 or by providing irregularities directly on the formed protective film. Incidentally, as the non-metal substrate, there is a carbon type substrate in addition to these glass type substrates.

These non-metal substrates have a characteristic that even if a magnetic film is formed by the same process as that of forming a magnetic film on a NiP substrate, the same excellent magnetic properties as the NiP substrate cannot be obtained. It is known that it is difficult to obtain a magnetic film having a particularly high coercive force. It is considered that this is because the heat absorption and heat conductivity of the glass substrate are extremely lower than that of the NiP substrate, and that gas is released from the glass substrate surface by heating. In order to manufacture a high-performance magnetic disk using this glass substrate, first, a non-magnetic metal layer is formed on the glass substrate to improve the heat absorption and heat conductivity of the glass substrate and to release gas from the substrate. Has been proposed, and thereafter a magnetic film is formed by a normal magnetic film forming process. In the specification of the present invention, the nonmagnetic metal layer previously formed on the surface of the glass substrate is called "precoat". Further, as a document in which a magnetic disk using a non-metal substrate is described, there is, for example, Japanese Patent Laid-Open No. 5-151569.

Further, in recent magnetic disk devices, MR (magnetoresistive effect) dedicated to data reproduction is used for high density recording / reproduction.
Type magnetic head tends to be used, and this MR type magnetic head uses a magnetoresistive effect element whose electric resistance value changes according to a change in magnetic field, and is more sensitive than an inductive head in which a coil is formed by a semiconductor forming technique. Is known to be high. The magnetic film of the magnetic disk corresponding to this MR type magnetic head has a residual magnetic flux density Br of the magnetic film and a film thickness.
The product Br · tm of tm can be smaller than that for inductive heads, and the magnetic film can be made thin, which is suitable for high-density recording.

[0006]

Although the magnetic film of the non-metal magnetic disk manufactured by the above-mentioned prior art has the same magnetostatic characteristics as those of the magnetic disk using the NiP substrate, these magnetic disks can be obtained. On the other hand, when the data reproducing characteristic using the MR (magnetoresistive effect) type magnetic head was measured, it was found that the noise generated from the magnetic film was large and there was a problem in combination with the MR type magnetic head.

It is an object of the present invention to eliminate the above-mentioned problems caused by the prior art, and to provide a magnetic disk using a non-metal substrate in which noise generated from a magnetic film is reduced. Another object of the present invention is to provide a magnetic disk using a non-metal substrate in which noise from a magnetic film is reduced, even in a non-metal disc substrate in which a protrusion for avoiding head adhesion is provided on the disc substrate. Is to provide.

[0008]

In order to achieve the above object, a magnetic disk using a non-metal substrate according to the present invention comprises a non-metal magnetic disk substrate and a non-metal magnetic disk substrate. A first precoat layer made of a magnetic metal film, a CVD precoat layer that absorbs irregularities of the first precoat layer on the first precoat layer, and a magnetic layer and a protective film formed on the precoat layer. It is characterized by including.

[0009]

In the magnetic disk using the non-metal substrate according to the above feature, the unevenness of the first pre-coat layer is absorbed on the first pre-coat layer made of the non-magnetic metal film on the non-metal magnetic disk substrate. By providing the CVD precoat layer, it is possible to smooth the surface of the disk and reduce noise from the magnetic film.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic disk according to an embodiment of the present invention will be described below in detail with reference to the drawings. First, the principle of the present invention will be described for easy understanding. First, the reason why the noise generated from the magnetic film becomes large when the data reproducing characteristic of an MR (magnetoresistive effect) type magnetic head is measured for a non-metal magnetic disk will be described. In this specification, the roughness of the magnetic film and the roughness of the substrate surface are expressed as Rp (unit: nm). The roughness Rp is the maximum value of the peaks appearing on the positive side of the center line of the roughness curve measured by STM or AFM.

First, FIG. 4 shows that the roughness Rp of the substrate surface is related to the disk noise. FIG. 4 is an experimental result of the relationship between the substrate noise Rp and the disk noise (unit: μVrms) of a plurality of magnetic disks using tempered glass or various crystallized glasses as a substrate. As is clear from the above, it can be understood that the rougher the substrate surface, the more the disk noise is affected by the influence on the magnetic film surface. Next, the reason why the disk noise increases due to the roughness of the magnetic film surface will be described. Generally, it is considered that the noise of the magnetic film of the magnetic disk is generated from the inverted portion of the magnetization reversal signal recorded at the time of data writing, and the magnetic flux does not leak out of the film after the direct current erasing without the magnetization reversal. Although it is supposed to be noise, the inventors of the present invention have found that the magnetic film formed on the non-metal substrate has larger noise after DC erasing than the magnetic film formed on the conventional NiP substrate.
Particularly in the combination with the MR head, the rougher the film surface of the magnetic film is, the larger the noise becomes, and the magnetic pole is generated on the surface of the film, and the noise after DC erasing and the noise from the magnetization reversal portion are superimposed to generate a large noise. It is supposed to do.

Moreover, it has been found that the noise after the DC erasure of the magnetic film formed on the non-metal substrate is several times to ten times larger than that of the NiP substrate. According to a study made by the present inventors, it has been found that this cause is closely related to the roughness of the magnetic film surface. Therefore, in a magnetic disk using a non-magnetic substrate, the noise after DC erasing increases as the roughness of the magnetic film surface increases, and there is a problem that the MR type magnetic head has high noise characteristics in terms of recording and reproducing characteristics. It has been found that there is a problem with the combination with a magnetic head.

Generally, the cause of the roughening of the magnetic film surface of the magnetic disk is that the surface of the substrate itself is large, or that the film itself becomes rough due to the process of forming the magnetic film. In the process of manufacturing a magnetic disk using a non-magnetic metal substrate,
When a precoat layer for improving the heat absorption and thermal conductivity of a non-metal substrate is formed by sputtering, this precoat layer (metal film) forms a crystal structure, and the crystal grains grow to a large extent to cause roughening of the substrate surface itself. And the surface of the magnetic film provided on the precoat layer becomes rough, and if the film is formed so that the precoat layer does not have a crystalline structure, the denseness of the film may deteriorate. . In the present invention, a nonmagnetic metal precoat film is formed on a nonmetal substrate by a sputtering method, and a precoat film formed by plasma vapor deposition (hereinafter referred to as plasma CVD) is further formed on the nonmagnetic metal precoat film. Plasma CVD with precoat layer
The precoat film according to (1) absorbs irregularities due to roughness of the precoat film formed by the sputtering method and smoothes the surface, thereby smoothing the magnetic film and reducing noise from the magnetic film.

When a protrusion called a filler is formed on the surface of the non-metal substrate in order to prevent adsorption of the magnetic head, the magnetic film formed on the protrusion has a magnetic film surface that reflects the shape of the substrate. It causes rough. In the present invention, the size of the protrusions /
The noise of the magnetic disk is reduced by setting the shape / density to a predetermined value described below or less.

<Embodiment 1> A magnetic disk according to an embodiment of the present invention will be specifically described below. First, the magnetic film of a magnetic disk using a non-metallic substrate in consideration of the MR head, which is the object of the present invention, has a film thickness of 10 nm to 40 nm, the product of the film thickness tm of the magnetic film and the residual magnetic flux density Br Br · tm. Is 50 to 180 Gμm
Hereinafter, the coercive force Hc is set to 2000 Oe or more, and it is preferable to form the film on the non-metal substrate so as to obtain such magnetic characteristics. As the non-metallic substrate, a tempered glass-based / crystallized glass-based / carbon-based substrate can be used, and the sputtering device is a single-wafer type device that heats and forms a film on each substrate. An independent vacuum chamber is desirable for the process vacuum chamber for heating and film formation.

As shown in FIG. 1, the magnetic disk according to this embodiment is formed by a non-magnetic metal precoat film 2 formed on a nonmetal substrate 1 by a sputtering method or the like, and by plasma CVD on the metal precoat film 2. The CVD precoat film 3 and the Cr underlayer 4, the Co alloy magnetic film 5, and the protective film 6 are formed on the precoat film 3. That is, the magnetic disk according to this example is characterized in that two precoat layers including the CVD precoat film 3 formed by plasma CVD are provided and smoothed by this plasma CVD.

The plasma CVD coating of the CVD precoat film 3 is a silane-based gas (SiH4) or a methane-based gas (CH4).
It is preferable to decompose / generate radicals by high-frequency power in a reduced pressure atmosphere to form a film, and since the plasma CVD method generally has a better film coverage than the sputtering method, the sputter growth of the non-metal precoat film 2 is performed. It has a function of absorbing unevenness due to and smoothing the surface.

In this state, as shown in FIG. 2 showing a cross section of the SEM image in which FIG. 1 is enlarged, the roughness (irregularities) of the substrate 1 having the surface roughness Rmax of several tens nm to several hundreds nm and the nonmagnetic metal. It can be seen that the roughness (irregularities) of the precoat film 2 makes the film surface flat due to the surrounding property of the film by the plasma CVD method. 2 like this
By forming the Cr underlayer film 4 and the Co alloy magnetic film 5 on the precoat layers 2 and 3 of the layer, the roughness of the magnetic film surface can be suppressed and the noise can be reduced.

The magnetic disk according to this embodiment is preferably manufactured by the following steps, for example. First, the non-metallic substrates 1 are loaded into the vacuum chamber one by one from the outside of the vacuum chamber and heated. This heating is especially performed on the glass substrate F.
Since the emissivity is low (ε = about 0.1) and the thermal conductivity is low, it cannot be heated to a high temperature, for example, heating at around 100 ° C. Next, a nonmagnetic metal layer corresponding to the nonmagnetic metal precoat film 2 is formed with a thickness of 40 nm. This non-magnetic metal layer is
A refractory metal such as Cr, Ti, V, Mo, Nb, Ta, W, or an alloy thereof is desirable, and a Cr film is formed by sputtering in this embodiment.

Thereafter, a nonmagnetic metal precoat film 3 of a carbon film corresponding to the CVD precoat film 3 formed by plasma CVD.
Is formed with a film thickness of 15 nm using methane as a source gas. The process up to the above steps is the process of forming the precoat film, and normally, the Cr underlayer film 4 and the magnetic film 5 are continuously sputtered as they are. The base film and the magnetic film may be formed by another film forming apparatus.

To form the magnetic film 5, the precoated substrate is reheated. The heating before forming the magnetic film improves the emissivity and thermal conductivity due to the precoat layer,
Heating above 300 ° C. is possible, and in this embodiment, the substrate was heated to 300 ° C. in consideration of the warp of the substrate. After that, a Cr underlayer film 4 of 50 nm, a Co alloy magnetic film of 25 nm, and a C protective film of 30 nm were successively formed. For this Co alloy magnetic film, a magnetic metal of CoCr (16 atom%) Ta (4 atom%) was used. If the specific resistance of the CVD precoat film is large (10 ⁶ Ωcm or more), the CVD precoat film may be subject to dielectric breakdown when radio frequency (RF) sputtering is used to form the underlying film and magnetic film formed on it. In the example, all films were formed by direct current (DC) sputtering. After the above film forming process, a magnetic disk can be manufactured by forming a protrusion for avoiding head adsorption on the surface of the C protective film and further applying a lubricant.

In order to explain the effect of reducing the roughness of the film surface by the precoat layer in this embodiment, the Cr precoat film 2 and the CVD-C precoat film 3 and the Cr undercoat film of the magnetic disk produced by the above method are described. 4, and changes in the roughness of the Co alloy magnetic film 5 are shown in FIG. In this example, the substrate 1 is a disk substrate having a flat surface (Rp = 3.6 nm) made of a tempered glass material. For the roughness, a stylus-type roughness meter or AFM is used. With these roughness measurements, it is possible to observe minute surface roughness on the glass substrate surface with a pitch of several tens nm to several hundreds nm. First, when the Cr precoat film 2 which is a non-magnetic metal is formed with a film thickness of 40 nm, its surface is roughened to Rp = 6 nm as shown in FIG. Next, by coating the CVD-C precoat film 3, the roughness becomes flat to about Rp = 2 nm. After this, Cr underlayer 4,
The Co alloy magnetic film 5 is formed to have a slight film surface, but the CVD-C precoat film can reduce the roughness of the magnetic film surface.

FIG. 5 shows the relationship between the roughness of the magnetic film surface, the disk noise, and the noise after DC erasing. This magnetic film surface roughness is the roughness obtained by changing the precoating process (including the two-layer precoat layer). As shown in FIG. 5, the smaller the magnetic film surface roughness Rp, the more the disk noise. It can be seen that it will decrease. Further, it is also found that the noise after the DC erasure is also reduced, and from this fact, it is found that the smaller the roughness of the magnetic film surface is, the lower the noise after the DC erasure and the disk noise are.

As described above, the magnetic disk according to the present embodiment is
The flatness of the magnetic film 5 can be improved and noise can be reduced by absorbing the roughness (unevenness) of the substrate 1 and the precoat film 2 on the Cr precoat film 2 by the CVD precoat film 3.

Next, the inventors compared the tempered glass substrate, the crystallized glass substrate, and the carbon substrate with the metal precoat film alone / metal precoat film and the CVD carbon for comparison. In case of two-layer precoat layer / metal precoat film and CV
A two-layer precoat layer of the D-Si film and a magnetic disk on which a magnetic film was formed after forming three types of precoat layers were prepared and noise was measured by an MR head. The track width of the MR head is 3 μm. The measurement conditions are noise and magnetization reversal density after DC erasure for all magnetic disks.
The noise when 90 kFCI (Flux Change / Inch) was recorded was measured. This magnetization reversal density has a track density of 5 kTPI.
(Track / Inch), when 1-7RLLC is set as the modulation method,
The areal recording density is equivalent to 600 Mb / in ² . The flying height of the MR head was 100 nm from the magnetic film surface.

With respect to the magnetostatic characteristics of the above-mentioned three types of magnetic disks, it has been found that almost the same magnetostatic characteristics can be obtained for the magnetic disks of various substrates / precoats as shown in Table 1.

[0027]

[Table 1]

Further, a magnetic disk of a NiP substrate was prepared in order to compare the NiP substrate which has been conventionally used with the above non-metallic substrate. This static magnetic property is shown in Table 2.

[0029]

[Table 2]

The magnetic disk of NiP substrate does not have a precoat layer. This NiP substrate has a magnetic film having no magnetic anisotropy like the above-mentioned non-metal substrate. A substrate was used. FIG. 7 shows a comparison of the sizes of the disk noises of the various disks shown in Tables 1 and 2. From Table 1, the roughness of the magnetic film surface is CVD-C film or CVD
-The two-layer precoated disc coated with Si film is small,
It became Rp3nm or less. The noise on these discs is about 1/2
And the noise after DC erasing was also reduced. Moreover, the noise value was almost the same as that of the NiP substrate disk.

Further, the Cr underlayer film described in the above embodiment is
In addition to Cr, Cr alloys such as CrTi and CrV are known, and in any of these alloys, the crystal grains of the underlayer are made finer and the roughness of the magnetic film surface can be reduced. Further, these alloy underlayer films were effective in reducing noise even when formed on the precoat layer as shown in this example. Further, Co alloy magnetic film, CoCrPt, CoNiCr, etc., roughly classified, CoCr-based alloy, CoNi-based alloy is known, but any Co alloy, as shown in the present embodiment, can reduce the roughness of the magnetic film surface, low. A noisy magnetic disk was obtained.

<Embodiment 2> Next, an embodiment in which the present invention is applied to a magnetic disk in which a protrusion called a filler is formed on the surface of a non-metal substrate in order to prevent adsorption to a magnetic head will be described below. As described above, in this magnetic disk, the magnetic film also reflects the shape of the substrate due to the protrusions and causes the surface of the magnetic film to become rough, and is greatly concerned with noise.

The magnetic disk according to this embodiment uses a crystallized glass substrate 10 in which a crystal grain 11 is mixed in an amorphous portion 12 as shown in FIG. A metal precoat film 2, a CVD precoat film 3, a Cr underlayer film, a Co alloy magnetic film 5 and a protective film 6 are laminated, and the crystal grains 11 are formed on the surface of the protective film 6.
The projection 7 is formed so as to project.

The crystallized glass substrate 10 needs to be polished so that the surface of the crystallized glass substrate 10 other than the protrusions 7 formed on the substrate surface for avoiding sticking of the head is flat. Due to the difference in polishing efficiency between the crystal grains 11 and the amorphous portion 12 of the substrate, when crystallized glass substrate is polished, fine crystal grains appear as convex on the substrate surface. This serves as the protruding portion 7 for avoiding the above-described head adhesion.

Since the protrusion 7 also affects the magnitude of noise, the size / shape / density of the protrusion must be controlled, and the diameter of the protrusion 7 is 5 minutes of the recorded magnetization reversal length. 1 or less, height 130 nm or less, shape polygonal pyramid, density 10 ³
The number of pieces / cm ² to 10 ⁹ pieces / cm ² is preferable. Also in the magnetic disk according to this embodiment, the effect of low noise described in the above embodiments with reference to the tables and drawings is obtained.

As described above, in the magnetic disk according to each of the above-mentioned embodiments, the film surface roughness of the magnetic film formed on the non-metal substrate is Rp10 nm.
The disk noise could be reduced by the following. This makes it possible to achieve high density recording with an areal recording density of 600 Mb / in ² or more when combined with an MR head. Furthermore,
When a corrosion resistance test was performed in an environment of a temperature of 60 ° C and a humidity of 90% or more, it was possible to prevent the elements contained in the non-metallic substrate from diffusing to the surface by applying a precoat by CVD,
The corrosion resistance of the magnetic disk is improved.

The magnetic disk according to the present invention can be expressed as follows in another form. In a magnetic disk comprising a non-metal magnetic disk substrate, one or more non-magnetic metal films formed on the substrate, a magnetic film containing Co as a main component, and a protective film, the surface of the magnetic film A magnetic disk comprising a magnetic film having a roughness Rp of 10 nm or less. In the magnetic disk of the above aspect, the diameter of the portion of the magnetic film surface protruding from the magnetic film is 1/5 or less of the recorded magnetization reversal length, the height is 3 nm to 30 nm, and the presence of the protruding portion The surface roughness of the magnetic film surface other than the protrusion is 10 ³ pieces / cm ² to 10 ⁹ pieces / cm ^2.
A magnetic disk characterized by being less than or equal to nm.

[0038]

As described above, the magnetic disk using the non-metal substrate according to the present invention has the first precoat layer formed of the non-magnetic metal film on the non-metal magnetic disk substrate. By providing the CVD precoat layer that absorbs the unevenness of the precoat layer, it is possible to smooth the surface of the disk and reduce noise from the magnetic film.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a magnetic disk using a non-metal substrate with a CVD precoat according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a two-layer precoat portion coated with the CVD precoat in FIG.

FIG. 3 is a partial cross-sectional view of a magnetic disk using a crystallized glass substrate according to another embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between surface roughness of a non-metallic substrate and noise.

FIG. 5 is a diagram showing a relationship between surface roughness of a magnetic film and noise.

FIG. 6 is a diagram showing a relationship between a film forming process and film surface roughness.

FIG. 7 is a diagram showing a relationship between a precoat layer and disc noise.

[Explanation of symbols]

1 --- non-metal substrate, 2 --- non-magnetic metal precoat film, 3 --- CV
D precoat film, 4 --- Cr underlayer film, 5 --- Co alloy magnetic film, 6--
-Protective film, 11 --- Crystal grains, 12 --- Amorphous part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Mitsuhiro Masada 2880 Kozu, Odawara-shi, Kanagawa Hitachi Storage Systems Division (72) Inventor Yu Inagaki 2880 Kozu, Odawara, Kanagawa Hitachi Storage Co., Ltd. System Division (72) Inventor Yasuo Yaku 2880, Kozu, Odawara-shi, Kanagawa Stock Company Hitachi Storage Systems Division (72) Inventor Rinka Goda 2880, Kozu, Odawara, Kanagawa Hitachi Storage Systems Business Inside (72) Inventor Atsushi Takagaki 2880 Kozu, Odawara, Kanagawa Stock Company Hitachi Storage Systems Division (72) Inventor Kiyoshi Akamatsu 2880 Kozu, Odawara, Kanagawa Hitachi Stray Co., Ltd. Within the Systems Division (72) inventor Fujita salt land Odawara, Kanagawa Prefecture Kozu 2880 address stock company Hitachi storage system within the business unit

Claims (1)

[Claims] 1. A non-metal magnetic disk substrate, a first precoat layer made of a non-magnetic metal film provided on the non-metal magnetic disk substrate, and a first precoat layer formed on the first precoat layer. CV provided to absorb the unevenness of the precoat layer of No. 1
A magnetic disk using a non-metal substrate, comprising a D precoat layer and a magnetic layer and a protective film formed on the precoat layer.