JP2003123242A - Magnetic recording medium and magnetic memory device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make magnetic crystal grain sizes sufficiently fine and to make the signal-to-noise ratio higher without making the tact time longer relating to a magnetic recording medium and a magnetic memory device. SOLUTION: A B-containing adhesion property improving layer 2 containing boron is disposed between a nonmagnetic substrate 1 and an NiP based layer 3 essentially consisting of Ni and P.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium and a magnetic storage device, and in particular, in a magnetic recording medium suitable for high density recording, fine crystal grains are formed to obtain high output with low noise. The present invention relates to a magnetic recording medium and a magnetic storage device, which are characterized by the structure of the adhesion improving layer.

[0002]

2. Description of the Related Art In recent years, the recording density of a horizontal magnetic recording medium such as a magnetic disk has remarkably increased due to the reduction of medium noise and the development of a magnetoresistive head and a spin valve head. The substrate, the underlayer, the intermediate layer, the magnetic layer, and the protective layer are laminated in this order.

Of these, the underlayer is made of a non-magnetic Cr or Cr alloy having a bcc structure, the intermediate layer is made of a non-magnetic or ferromagnetic Co alloy having an hcp structure, and the magnetic layer is made of a ferromagnetic Co alloy having an hcp structure. Has been done.

In such a magnetic recording medium, a non-magnetic glass substrate or an Al--Mg alloy substrate is used as the substrate. When glass is used as the non-magnetic substrate,
In order to orient the c-axis of the hcp magnetic layer in the plane, C
A seed layer is provided between the r-based underlayer and the non-magnetic substrate,
The orientation of the system underlayer is changed from (110) to (100).

NiP is a typical seed layer,
Since NiP cannot obtain sufficient adhesion when it is directly formed on a glass substrate, a Cr layer is interposed as an adhesion layer between the glass substrate and the Cr-based underlayer.

Further, in the conventional magnetic recording medium, various attempts have been made to increase the S / N ratio.
Numerous methods such as controlling the crystal orientation of the underlayer, lattice matching between the underlayer and the magnetic layer, and improving the crystal orientation of the magnetic layer by adopting an intermediate layer, or increasing the coercive force by adjusting the composition of the magnetic layer. These methods are just examples, and there are various other methods.

Further, in order to increase the S / N ratio, it is also important to make the magnetic crystal grain size finer. Therefore, the material composition of the magnetic layer is adjusted, or Ta, B, etc. are added to these material compositions. The constituent elements are adjusted by the additive elements for adding the trace elements of.

An example of a conventional magnetic recording medium will be described with reference to FIG. See FIG. 7. FIG. 7 is a structural explanatory view of a conventional magnetic recording medium. First, a glass substrate 31 whose surface is chemically strengthened is thoroughly washed, and then heated to 220 ° C. using a magnetron sputtering device. Cr adhesion layer 32 having a thickness of 25 nm and NiP having a thickness of 25 nm
The seed layer 33 is sequentially formed, and the glass substrate 31 on which the NiP seed layer 33 is formed is exposed to the atmosphere so that the (100) plane of the Cr first underlayer 35 to be formed next is preferentially oriented.
The surface of the P seed layer 33 is subjected to oxygen adsorption and oxidation treatment to form an oxidation treatment layer 34.

Then, again using the magnetron sputtering apparatus, the Cr first underlayer 35 having a thickness of 4 nm, the CrMo second underlayer 36 having a thickness of 2 nm, and the thickness of 1 nm are heated to 220 ° C. The CoCrTa intermediate layer 37, the CoCrPtBCu stabilizing layer 38 having a thickness of 5 nm, the Ru coupling layer 39 having a thickness of 0.7 nm, and the CoCrPtBCu magnetic layer 40 having a thickness of 12 nm are sequentially formed.

Next, after the glass substrate 31 having the CoCrPtBCu magnetic layer 40 formed thereon is carried into the adjacent chamber via a gate valve, the thickness is, for example, 5 n.
m DLC (Diamond Like Carbon) protective layer 41
Then, although not shown, a fluorine-based lubricant is applied on the DLC protective layer 41 and dried to complete the basic structure of the high-density magnetic recording medium.
The composition ratio of each layer is atomic%. For example, the NiP seed layer 33 is NiP ₁₉ , that is, Ni ₈₁ P ₁₉ , and CrMo is
The second underlayer 36 is CrMo ₂₅ , the CoCrTa intermediate layer 37 is CoCr ₁₃ Ta ₅ , and CoCrPtBCu.
The stabilizing layer 38 and the CoCrPtBCu magnetic layer 40 are made of Co.
Cr ₁₈ Pt ₁₁ is a B ₇ Cu _5.

[0011]

However, if a process for increasing the layer thickness under the magnetic layer such as using a seed layer is entered, the grain size of the magnetic layer tends to be enlarged and the medium noise tends to increase. There's a problem.

For example, when the DLC protective layer is formed on the magnetic layer by the plasma CVD method, it is necessary to apply a bias voltage at the time of forming the film. When an insulating glass is used for the substrate, Cr is used to ensure conductivity. Both the adhesion layer 32 and the NiP seed layer 33 require a very thick layer having a thickness of 25 nm, that is, a total thickness of 50 nm, and the above-mentioned enlargement of the grain size becomes a problem.

Of these, since NiP forming the seed layer is amorphous, it is difficult to increase the grain size even with a thick film.
Since the thickening of the Cr adhesion layer provided under the P seed layer causes the grain size to increase, this situation will be described with reference to FIG.

See FIG. 8. FIG. 8 is an explanatory view of the thickness dependence of the crystal grain size of the Cr-based layer. As is clear from the figure, in the case of the Cr layer indicated by ◯, the CrMo ₂₀ layer indicated by Δ is also formed. Also in this case, it is understood that the average grain size increases as the film thickness increases. For example, in a film thickness of 25 nm, the crystal grain size is 13
It becomes as large as about nm.

In order to suppress the increase in crystal grain size due to such an increase in film thickness, it is sufficient to reduce the film thickness of the adhesion layer and increase the thickness of the NiP seed layer. Then, the NiP seed layer is formed. Since the takt time is defined by time,
There is a problem that the tact time becomes long and the productivity decreases. That is, in a mass production device, because of the short takt time,
The maximum film thickness that can be deposited in one chamber is 30 nm,
There is a limit to thickening only the NiP seed layer.

Therefore, according to the present invention, the magnetic crystal grain size is sufficiently reduced without increasing the tact time, and the S / N ratio is reduced.
The purpose is to increase the ratio.

[0017]

FIG. 1 is an explanatory view of the principle configuration of the present invention, and means for solving the problems in the present invention will be described with reference to FIG. In order to solve the above problems, according to the present invention, a NiP-based layer 3 containing Ni and P as main components is formed on a non-magnetic substrate 1 such as tempered glass whose surface is chemically treated or crystallized glass.
In a magnetic recording medium including a non-magnetic substrate 1 and NiP
The B-containing adhesion improving layer 2 containing boron is provided between the system layers 3.

As described above, by doping the adhesion improving layer 2 with B, the crystal grain size of the adhesion improving layer 2 can be reduced, and thus the magnetic crystal grain size can be reduced. The S / N ratio can be increased.

In this case, the B composition ratio in the B-containing adhesion improving layer 2 is 0.5 to 10 atom%, more preferably 1 to 6
It is desirable that the content is atomic%, and if it is less than 0.5 atomic%, the effect of addition is small, and if it exceeds 10 atomic%, the adhesion may deteriorate.

Further, the thicknesses of the B-containing adhesion improving layer 2 and the NiP-based layer 3 are preferably 30 nm or less, respectively, so that when the surface protective film 10 is formed without increasing the tact time. The conductivity can be ensured and the increase in crystal grain size can be suppressed.

Further, it is desirable that the surface of the NiP-based layer 3 be subjected to an oxidation treatment, whereby an oxygen-treated layer 4 which is adsorbed with oxygen and is naturally oxidized is formed on the surface, and the Cr-based underlayer 5 is formed. The crystal orientation of is improved.

As a typical structure of a magnetic recording medium, a Cr-based underlayer 5, a CoCr-based intermediate layer 6, a CoCr-based stabilizing layer 7, a Ru coupling layer 8 and a NiP-based layer 3 are provided on a NiP-based layer 3.
It is desirable that the CoCr-based magnetic layer 9 is formed in this order, in particular, a structure formed by a sputtering method.

The magnetic recording medium described above, a drive section for driving the magnetic recording medium in the recording direction, a magnetic head using a giant magnetoresistive effect element including a recording section and a reproducing section, and a magnetic head as a magnetic recording medium. A high-density magnetic recording device can be realized by configuring the magnetic recording device by means of relative movement with respect to each other and signal processing means for reproducing a signal input from the magnetic head and reproducing an output signal from the magnetic head.

[0024]

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG.
The manufacturing process of the magnetic recording medium of the embodiment will be described.
The figure is a schematic diagram of the magnetic recording medium.
A structure in which recording layers, etc., which are magnetic layers are symmetrically provided on both sides of the plate
It is built. See Figure 2 (a) First, for example, on the glass substrate 11 having a diameter of 65 mm,
Ultimate vacuum is 3 × 10^-6Multiple chambers are gated at Pa
Single-wafer stationary opposed type DC mag separated by a valve
Using a netron sputtering device, the Ar gas pressure is set to, for example,
Film forming conditions of 0.7 Pa and heating to 220 ° C., for example
And the B composition ratio is 0.5 to 10 atomic%, for example, 5 atomic%.
Cr₉₅B_FiveIt has a thickness of 30 nm or less, for example
For example, the CrB adhesion layer 12 having a thickness of 25 nm and the thickness of 30
nm or less, for example, 25 nm Ni ₈₁P₁₉Consisting of Ni
The P seed layer 13 is sequentially formed.

See FIGS. 3A and 3B. FIG. 3A is an AFM (atomic force microscope) image of the surface of the NiP seed layer 13 at this stage, and FIG.
Conventional NiP using the 25 nm Cr adhesion layer shown in
It was confirmed that the mottled pattern was finer than that of the AFM image on the surface of the seed layer, and the crystal grain size of the adhesion layer was reduced by the addition of B.

See FIG. 4. FIG. 4 is an explanatory diagram of the B composition ratio dependency of the crystal grain size of the CrB adhesion layer when the thickness of the CrB adhesion layer is 100 nm, and shows an average as the B composition ratio increases. It is confirmed that the particle size is small, and it is confirmed that the same effect is obtained in the embodiment of the present invention. The particle size is a calculation result using the Sherrer's formula.

Referring again to FIG. 2B, then, the glass substrate 11 on which the NiP seed layer 13 is formed.
Is exposed to the atmosphere to perform oxygen adsorption and natural oxidation on the surface of the NiP seed layer 13 to form an oxidation treatment layer 14, and the preferential crystal orientation planes of the Cr first underlayer and CrMo second underlayer to be deposited thereafter are set. Change from (110) to (100).

Refer to FIG. 2 (c). Then, again, the stationary facing type DC magnetron sputtering equipment is used.
Set the glass substrate 11 on which the oxidation treatment layer 14 is formed
After heating to 220 ℃, the thickness is, for example, 4 nm
Cr first underlayer 15 having a thickness of, for example, 2 nm of Cr
₇₅Mo_{twenty five}CrMo second underlayer 16 consisting of
For example, 1 nm Co₈₂Cr₁₃Ta_FiveCoCrT consisting of
a Intermediate layer 17, Co having a thickness of 5 nm, for example₅₉Cr₁₈
Pt₁₁B ₇Cu_FiveCoCrPtBCu stabilizing layer composed of
18, a Ru coupling layer 19 having a thickness of 0.7 nm,
And, for example, Co having a thickness of 12 nm₅₉Cr₁₈Pt₁₁
B ₇Cu_FiveCoCrPtBCu magnetic layer 20 consisting of
Next, deposit.

Next, using a plasma CVD apparatus, Co
On the CrPtBCu magnetic layer 20, the thickness is, for example, 5 n.
Although not shown, a fluorine-based lubricant is applied to the DLC protective layer 21 after the m-thick DLC protective layer 21 is deposited, and the DLC protective layer 21 is dried to complete the basic structure of the high-density magnetic recording medium.

See FIG. FIG. 5 shows the thickness on the Al substrate with the NiP seed layer interposed.
Is 6 nm of Cr₇₅Mo _{twenty five}Layer, 3 nm thick Co₆₃Cr
₃₇Layer and Co with a thickness of 15 nm_67-xCr_{twenty two}Pt₁₁B
_xGrain size of the magnetic layer in the reference sample in which the layers were sequentially formed
3 is an explanatory diagram of the B composition ratio dependency of the magnetic layer of FIG.
It decreases as the B composition ratio x of the adhesion layer increases,
Therefore, in the embodiment of the present invention, the magnetic layer
The average particle size becomes smaller as the B composition ratio of the adhesion layer increases.
It is inferred that

See FIG. 6. FIG. 6 is an explanatory diagram of the electromagnetic conversion characteristics of the magnetic recording medium according to the embodiment of the present invention. For comparison, the electromagnetic conversion characteristics of a conventional example using a Cr adhesion layer are also shown. ing. In this case, the calculation formula (1) below is used to calculate the SNR (S / N ratio) per 1 μm of the lead width, and 82.8 kFCI (Fl
The ratio between the reproduction output at ux Change per Inch) and the medium noise at 331.0 kFCI is displayed in dB. SNR (dB) = 20 × log (S / N) (1) However, the unit of S and N is mVrms.

As is apparent from the figure, the S / N ratio of the magnetic storage medium according to the embodiment of the present invention is improved by about 0.6 dB as compared with the conventional magnetic recording medium. ,
Considering together with FIG. 5, it is considered that this is an effect due to the refinement of the crystal grain size of the magnetic layer. The B composition ratio is 10 atom%.
In the following, the phenomenon that the adhesiveness was lowered by adding B to the adhesive layer was not confirmed.

As described above, in the embodiment of the present invention, since B is added to the adhesion layer to reduce the crystal grain size of the adhesion layer, the adhesion layer is thinned to reduce the thickness of the NiP seed layer. Therefore, the crystal grain size of the magnetic layer can be reduced without increasing the thickness and without increasing the tact time, whereby a high density magnetic recording medium having excellent magnetic characteristics can be realized.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations and conditions described in the above embodiments, and various modifications can be made. For example, although a tempered glass substrate whose surface has been chemically treated to enhance its mechanical strength is used as the non-magnetic substrate, it is not limited to such a tempered glass substrate, and various glass substrates can be used. Alternatively, a quartz glass substrate or another crystallized glass substrate similar to the quartz substrate may be used.

Further, in the above embodiment, the CrB layer is used as the B-containing adhesion layer, but it is not limited to the CrB layer, and the TiB layer, the VB layer, the CuB layer, the Z layer.
The rB layer, the NbB layer, the MoB layer, the HfB layer, the TaB layer, or the WB layer may be used. In any case, a layer containing B is used in order to reduce the crystal grain size. It becomes mandatory.

Further, in the embodiment, Cr ₇₅ Mo ₂₅ is used as the second underlayer, but CrM having another composition is used.
o, and CrW or CrMoW may be used.

Although Co ₅₉ Cr ₁₈ Pt ₁₁ B ₇ Cu ₅ is used as the magnetic layer in the above-mentioned embodiment, other composition ratios such as Co ₅₆ Cr ₂₁ Pt ₁₂ B ₆ Cu ₅ are used. C
oCrPtBCu alloy may be used, or Co ₅₈ Cr ₂₄ P
CoCrPtB alloy such as _{t 10 B 8, Co 69 Cr} 21 Pt 8
Co ₂ Cr alloy such as Ta ₂ or Co ₇₄ Cr
CoCrPtTaNb alloy such as ₁₅ Pt ₄ Ta ₄ Nb ₃ may be used, and in any case, Co and C
Any CoCr alloy containing r as a main component and at least Pt may be used. This is because the Co alloy has a hexagonal close-packed structure (hc
This is because p) has uniaxial anisotropy and an appropriately high coercive force can be obtained by adding Pt.

Although Co ₈₂ Cr ₁₃ Ta ₅ is used as the intermediate layer in the above embodiment, a CoCrTa alloy having another composition ratio may be used, and further, C
Other alloys such as oCr and CoCrPtTa may be used.

Further, in the above embodiment, Ni
Although the oxidation treatment of the P seed layer is performed by exposing it to the atmosphere, it is also possible to introduce O ₂ into the chamber and perform the oxidation treatment.

Further, in the above embodiment, the underlayer has a two-layer structure, but a single underlayer may be used, or an intermediate layer may be used. It is not always necessary, and a magnetic layer having a multilayer structure with exchange coupling is used as the magnetic layer, but a single magnetic layer may be used.

Here, the detailed features of the present invention will be described again with reference to FIG. See FIG. 1 (Appendix 1) In a magnetic recording medium including a NiP-based layer 3 containing Ni and P as main components on a non-magnetic substrate 1, boron is contained between the non-magnetic substrate 1 and the NiP-based layer 3. A magnetic recording medium comprising a B-containing adhesion improving layer 2. (Supplementary Note 2) The magnetic recording medium according to Supplementary Note 1, wherein the B composition ratio in the B-containing adhesion improving layer 2 is 0.5 to 10 atom%. (Supplementary Note 3) The magnetic recording medium according to Supplementary Note 1 or 2, wherein the B-containing adhesion improving layer 2 and the NiP-based layer 3 each have a thickness of 30 nm or less. (Supplementary Note 4) The magnetic recording medium according to any one of Supplementary Notes 1 to 3, wherein the non-magnetic substrate 1 is either tempered glass whose surface is chemically treated or crystallized glass. (Supplementary Note 5) Any one of Supplementary Notes 1 to 4, wherein the surface of the NiP-based layer 3 is subjected to an oxidation treatment.
The magnetic recording medium according to 1. (Supplementary Note 6) On the NiP-based layer 3, a Cr-based underlayer 5,
6. The CoCr-based intermediate layer 6, the CoCr-based stabilizing layer 7, the Ru coupling layer 8, and the CoCr-based magnetic layer 9 are formed in this order, and the magnetic field according to any one of appendices 1 to 5. recoding media. (Supplementary Note 7) The B-containing adhesion improving layer 2, NiP-based layer 3, Cr-based underlayer 5, CoCr-based intermediate layer 6, CoCr-based stabilizing layer 7, Ru coupling layer 8, and CoCr magnetic layer 9
The magnetic recording medium according to any one of appendices 1 to 6, wherein the magnetic recording medium is a sputtered film. (Supplementary Note 8) The magnetic recording medium according to any one of Supplementary Notes 1 to 7, wherein a carbon-based surface protective film 10 made of a plasma chemical vapor deposition film is provided on the CoCr-based magnetic layer 9. . (Supplementary Note 9) Magnetic using the magnetic recording medium according to any one of Supplementary Notes 1 to 8, a drive unit that drives the magnetic recording medium in the recording direction, and a giant magnetoresistive effect element including a recording unit and a reproducing unit. At least a head, means for moving the magnetic head relative to the magnetic recording medium, and signal processing means for inputting a signal to the magnetic head and reproducing an output signal from the magnetic head. Magnetic recording device.

[0042]

According to the present invention, since B is added to the adhesion improving layer provided between the non-magnetic substrate and the NiP-based seed layer, the crystal grain size of the magnetic layer can be reduced. As a result, the S / N ratio of the magnetic recording medium can be improved, which in turn contributes to a large capacity and high density magnetic recording of a magnetic disk recording device such as a hard disk device.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a principle configuration of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process of the magnetic recording medium according to the embodiment of the invention.

FIG. 3 shows C in the magnetic recording medium according to the embodiment of the present invention.
It is explanatory drawing of the crystal grain size of a rB adhesion layer.

FIG. 4 is an explanatory diagram of the B composition ratio dependency of the crystal grain size of the CrB layer.

FIG. 5 is an explanatory diagram of B composition ratio dependency of a crystal grain size of a magnetic layer in a reference sample.

FIG. 6 is an explanatory diagram of electromagnetic conversion characteristics of the magnetic recording medium according to the embodiment of the present invention.

FIG. 7 is a structural explanatory view of a conventional magnetic recording medium.

FIG. 8 is an explanatory diagram of film thickness dependence of crystal grain size of a Cr-based layer.

[Explanation of symbols]

1 Non-magnetic substrate 2 B-containing adhesion improving layer 3 NiP-based layer 4 Oxidation treatment layer 5 Cr-based underlayer 6 CoCr-based intermediate layer 7 CoCr-based stabilizing layer 8 Ru coupling layer 9 CoCr magnetic layer 10 Surface protection film 11 glass substrate 12 CrB adhesion layer 13 NiP seed layer 14 Oxidized layer 15 Cr first underlayer 16 CrMo second underlayer 17 CoCrTa intermediate layer 18 CoCrPtBCu stabilizing layer 19 Ru coupling layer 20 CoCrPtBCu magnetic layer 21 DLC protective layer 31 glass substrate 32 Cr adhesion layer 33 NiP seed layer 34 Oxidized layer 35 Cr first underlayer 36 CrMo Second Underlayer 37 CoCrTa intermediate layer 38 CoCrPtBCu stabilizing layer 39 Ru coupling layer 40 CoCrPtBCu magnetic layer 41 DLC protective layer

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Claims (5)

[Claims] 1. A magnetic recording medium comprising a NiP-based layer containing Ni and P as main components on a non-magnetic substrate, and a B-containing adhesion improving layer containing boron between the non-magnetic substrate and the NiP-based layer. A magnetic recording medium comprising: 2. The magnetic recording medium according to claim 1, wherein the B composition ratio in the B-containing adhesion improving layer 2 is 0.5 to 10 atomic%. 3. The magnetic recording medium according to claim 1, wherein the B-containing adhesion improving layer and the NiP-based layer each have a thickness of 30 nm or less. 4. A Cr-based underlayer and C on the NiP-based layer.
4. The magnetic recording medium according to claim 1, wherein an oCr based intermediate layer, a CoCr based stabilizing layer, a Ru coupling layer, and a CoCr based magnetic layer are formed in this order. . 5. The magnetic recording medium according to claim 1, a drive unit for driving the magnetic recording medium in a recording direction, and a giant magnetoresistive element including a recording unit and a reproducing unit. A magnetic head used, at least means for moving the magnetic head relative to the magnetic recording medium, and signal processing means for inputting a signal to the magnetic head and reproducing an output signal from the magnetic head. Characteristic magnetic recording device.