JP2003223713A - Information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the recording resolution and SNR of an information recording medium consisting of a back lining, a non-magnetic intermediate layer, and a recording layer. <P>SOLUTION: This information recording medium is featured in that it has a back lining with its easy magnetizing axis set in its inside direction, a non- magnetic intermediate layer whose surface is finely roughened, and a recording magnetic layer easy to magnetize perpendicularly to record information in this order. Further, the non-magnetic intermediate layer consists of a dielectric layer, an agglomerated layer to form the fine asperity grains, and an enhancing layer to increase the height of the grains on the agglomerated layer in this order from the above back lining layer. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, and more particularly to a structure of a perpendicular magnetic recording type information recording medium having a backing layer made of a soft magnetic film.

[0002]

2. Description of the Related Art Conventionally, an in-plane magnetic recording type information recording medium has been proposed. This information recording medium of the in-plane magnetic recording system has at least a nonmagnetic underlayer, an in-plane magnetization recording magnetic film layer, and a protective film formed on a substrate in this order.
Japanese Patent Laid-Open No. 0-198995 proposes a non-magnetic underlayer made of a low-melting metal material and having irregularities formed on its surface. In addition, in order to meet the demand for higher density in recent years,
A perpendicular magnetic recording type information recording medium has been proposed in which the linear recording density (density in the track direction) of a disk is increased.

In this perpendicular magnetic recording system, information is recorded on a magnetic film (for example, TbFeCo) having perpendicular magnetic anisotropy. The medium structure is such that at least a nonmagnetic intermediate layer and a perpendicular magnetization recording magnetic film are formed on a substrate. , The protective film is formed in this order, and the non-magnetic intermediate layer includes, for example, a non-magnetic CoCr film containing a relatively large amount of Cr, a non-magnetic Ti film.
A system alloy film or the like is used. Further, as a base layer of a laminated perpendicular magnetization recording film composed of a Pt layer (or Pd layer) and a Co layer, a noble metal (Pt or the like) and an oxide (SiO 2
₂ etc.) or a magnetic recording medium having a layer formed of a composite material with a nitride (AlN etc.) has been proposed (Japanese Patent Laid-Open No. 2-216058).
001-155329, JP 2001-2912 A
30 publication). Further, a base layer provided with an interface layer containing carbon has also been proposed (JP-A-63-21).
1117).

Further, in the perpendicular magnetic recording system, it is proposed to provide a soft magnetic film as a backing layer between the substrate and the magnetic film in order to record and reproduce information on the magnetic film with high density and high efficiency. Has been done. FIG. 10 shows a block diagram of an example of a conventional magnetic information recording medium. The conventional medium has a structure in which a backing layer 2, a nonmagnetic underlayer 3, a recording layer 4, and a protective layer 5 are formed on a substrate 1. A magnetic material having a small coercive force is used for the backing layer 2 and is formed as a film having in-plane magnetic anisotropy. This is a magnetic interaction generated between the magnetic head and the backing layer 2. To obtain a larger magnetic field for perpendicular magnetic recording on the magnetic film (recording layer 4). For example, as the backing film 2, a FeNi-based alloy film, CoZ
r-based alloy film (CoZrNb), intermetallic compound film (FeTa
C) and the like are used. FIG. 10 shows typical materials and film thicknesses of other layers. Where the backing layer 2
And the thickness of the non-magnetic underlayer 3 equal to the distance between the recording layer and the recording layer are several tens of n
It is m or more. As shown in FIG. 11, the non-magnetic underlayer 3 has irregular particles on the surface thereof, and the average particle diameter of the particles is about 50 nm or more. Need to reduce this particle size.

Further, in Japanese Unexamined Patent Publication No. 2001-312815, a magnetic recording medium in which at least a soft magnetic film as a backing layer 2 and a base film are formed between a substrate 1 and a recording layer 4 (perpendicular magnetic film). Is proposed. The underlayer film is for improving the noise characteristics by refining the crystals of the perpendicular magnetic film laminated thereon, and is formed using a CoZrC-based material. In addition, a nonmagnetic underlayer (Ti, Zr, etc.) or a nonmagnetic intermediate layer (Co /
Those which form Cr-based alloys) have also been proposed. Further, a medium in which a carbon underlayer and a CoZr-based underlayer are directly formed on a glass substrate in order to increase nucleation sources for improving the noise characteristics of the medium by miniaturizing crystals such as a perpendicular magnetic film is also available. Proposed.

[0006]

The soft magnetic film is intended to obtain a large magnetic field due to the magnetic interaction between the soft magnetic film and the magnetic head. The distance between the soft magnetic film and the perpendicular magnetization recording magnetic film is preferably as short as possible. For example,
If the distance between the soft magnetic film and the perpendicular magnetization recording magnetic film is about 100 nm, normal recording cannot be performed and information reproduction is difficult. However, in an in-plane magnetic recording type information recording medium, the nonmagnetic underlayer generally has a film thickness of several tens of nm or more, and is quite thick. Therefore, even if this non-magnetic underlayer of the in-plane magnetic recording system is directly applied to the information recording medium of the perpendicular magnetic recording system, since the film thickness is too thick, it is impossible to record information with high density and high efficiency. .

Further, in order to form fine unevenness on the non-magnetic underlayer (unevenness forming layer), Japanese Patent Laid-Open No. 10-19895
In the publication 7, the thickness of the unevenness forming layer is set to 2 nm to 20 nm, but since there is an underlayer other than the unevenness forming layer and the surface roughness is small, the thickness of the entire underlayer including this layer is It is difficult to reduce the thickness. That is, in order to improve the recording resolution, it is necessary to reduce the grain size of the unevenness, but just by forming a conventional underlayer on the substrate, it is possible to reduce the thickness of the underlayer and reduce its surface. It is difficult to reduce the grain size of the uneven shape that can be obtained.

Further, there is no information recording medium of in-plane magnetic recording type in which a backing layer made of a soft magnetic film is formed between a substrate and a non-magnetic underlayer. Further, as an information recording medium of the perpendicular magnetic recording system, as shown in FIG. 10, a backing layer 2 and a non-magnetic underlayer 3 are formed on a substrate, which are both under non-magnetic layer. The ground layer 3 has a film thickness of several tens of nm or more, and the distance between the backing layer 2 and the recording layer 4 is about several tens of nm to several hundreds of nm, and an effect of achieving high density in a medium provided with the backing layer is obtained. Is difficult.

Further, in the medium disclosed in Japanese Patent Laid-Open No. 2001-312815, the total layer (multilayer film including an underlayer film) formed between the soft magnetic film (backing layer) and the perpendicular magnetic layer is formed. Since the film thickness increases to several tens of nm or more,
Similarly to the above, since the distance between the backing layer and the perpendicular magnetic layer is too large, the effect of providing the backing layer cannot be sufficiently obtained. Further, the structure in which the carbon underlayer or the like is directly formed on the substrate such as glass was effective for increasing the number of nucleation sources, but in the case where the backing layer (soft magnetic film) is formed on the substrate, Even if a carbon underlayer is formed on the backing layer, the effect of increasing nucleation sources is small, and especially when the carbon underlayer is formed on the backing layer without interposing a layer such as a dielectric layer, noise characteristics It is difficult to form a nuclear source that contributes to the improvement of

The present invention has been made in view of the above circumstances, and in a perpendicular magnetic recording type information recording medium having a backing layer, a non-magnetic layer formed of at least a dielectric thin film on the backing layer. By providing the intermediate layer,
An object is to improve recording resolution and SNR.

[0011]

The present invention has a backing layer having an easy axis of magnetization in the in-plane direction, a non-magnetic intermediate layer having fine irregularities formed on the surface, and an easy axis of magnetization in the vertical direction. A recording magnetic layer for recording information is formed in this order,
The non-magnetic intermediate layer is, in order from at least the side closer to the backing layer, a dielectric film layer, an agglomerating layer for forming fine irregularity-shaped particles, and an unevenness enhancing layer for increasing the height of the particles in the aggregating layer The present invention provides an information recording medium characterized by the following. According to this invention, since the non-magnetic intermediate layer including the dielectric film layer and the like is provided, the backing layer and the recording layer are made closer to each other, and the fine irregularities are formed on the surface of the layer formed below the recording layer. Particles can be formed, and the recording resolution and the SNR can be improved.

Here, in order to improve the recording resolution, it is preferable to use a material in which the surface tension of the aggregation layer is larger than the surface tension of the dielectric layer. Further, the aggregation layer may be a thin film made of a metal film or an alloy film. Furthermore, the unevenness enhancement layer may be formed of a material containing an element having an atomic radius smaller than that of the material of the other layers. Further, a base point forming layer for forming a core serving as a base point of particles formed in the aggregation layer may be further provided between the dielectric film layer and the aggregation layer.

Furthermore, the present invention is a method for forming an information recording medium, in which a backing layer, a non-magnetic intermediate layer, and a perpendicular magnetization recording magnetic layer are formed in this order on a substrate, and the backing layer is made of a soft magnetic material. Formed by sputtering,
The non-magnetic intermediate layer is formed by sputtering a non-magnetic material and a reactive gas to form a dielectric layer, and after a predetermined heat treatment, a metal or alloy material is sputtered thereon to form an agglomeration layer, The present invention provides a method for forming an information recording medium, which is formed by forming an unevenness enhancing layer by sputtering an element having an atomic radius smaller than that of a metal thereon. Further, a step of forming a base point forming layer may be introduced between the heat treatment and the aggregation layer forming step.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below based on the embodiments shown in the drawings. The present invention is not limited to this. <Embodiment 1> FIG. 1 is a block diagram of an information recording medium according to Embodiment 1 of the present invention. The medium of Example 1 has a backing layer 2, a dielectric layer 30, an aggregating layer 32, an unevenness enhancing layer 33, a recording layer 4 and a protective layer 5 formed in this order on a substrate 1.

Here, the portions of the dielectric layer 30, the aggregation layer 32, and the unevenness enhancing layer 33 correspond to the non-magnetic intermediate layer 3, which has a large number of fine uneven particles, and the recording resolution and SNR of the recording layer 4. The present invention is provided for the purpose of improving the above, and is a feature that characterizes the present invention. By setting the thickness of the non-magnetic intermediate layer 3 to about 3 nm or less, the distance between the backing layer and the recording layer and the distance between the backing layer and the recording head can be reduced, so that the recording magnetic field is reduced. The magnetic field distribution becomes steep, and the recording resolution and SNR can be improved.

[Structure of Medium of First Embodiment] FIG. 3 shows typical materials and film thicknesses of the medium of the first embodiment of the present invention. [Substrate 1] As the substrate 1, a Si substrate, an Al alloy substrate, or the like can be used in addition to the glass substrate. Further, a medium having a thickness of about 0.635 mm, which is similar to that of a conventional medium, may be used.

[Backing Layer 2] As the backing layer 2, a soft magnetic film having an easy axis of magnetization in the in-plane direction is used. As the material, a material containing a metal such as Fe, Co, or Ni as a main component,
For example, FeC, FeNi, CoZrNb can be used. Further, the thickness of the backing layer 2 needs to be about 300 nm in order to obtain effective magnetic interaction.

[Dielectric Layer 30] The dielectric layer 30 is formed on the backing layer 2 closest to the substrate in the non-magnetic intermediate layer 3, and has a fine uneven shape formed thereon. Is a layer necessary to make as small as possible.
If a thin film having a surface tension smaller than the surface tension of the aggregating layer 32 is formed between the backing layer 2 and the aggregating layer 32, the aggregating layer 3 is formed due to the difference in surface tension between the thin film and the aggregating layer 32.
In 2, fine island-shaped particles having an uneven shape can be formed.

By forming a thin film having a relatively small surface tension on the backing layer as described above, it is possible to improve the recording resolution of the information recording medium. Specifically, this thin film is made of a dielectric material. Use a membrane. As the dielectric film 30, a film having a surface tension of about 300 mN / m can be used. For example, SiOx, SiNx, ZnO.
An oxide or nitride such as x, AlOx, or AlNx can be used.

The dielectric film 30 as described above has a film thickness of about 0.5 nm and can be formed as a thin film having a considerably smooth surface. The surface tension of the backing layer 2 (FeC or the like) is about 2000 to 3000 mN / m, and the surface tension of the aggregation layer 32 described later is 1000 to 2000 mN / m.
It is a degree.

As will be described later, the presence or absence of this dielectric layer 30 causes a large difference in recording resolution (D50) and SNR, and the presence of the dielectric layer 30 determines the recording resolution and SN.
It contributes to the improvement of R. Furthermore, since such a layer having a relatively small surface tension is formed on the backing layer, there is more room for selection of the material used for the aggregation layer 32 formed thereon.

[Aggregating Layer 32] The aggregating layer 32 is a layer composed of fine irregular-shaped particles, and the smaller the particle size of the particles in this layer, the higher the recording resolution can be improved. As the aggregation layer 32, a metal such as Al, Pt, Pd, Au, or Cu in addition to Ag, or an alloy containing these metals as a main component (FePt, CoPt, WAg, or the like) can be used. The film thickness is about 0.5 nm. In addition, the aggregation layer 32
It is preferable to use a metal or alloy material having a low melting point in order to minimize the particle size of the uneven particles formed on the surface.

This is because the low-melting-point material generally easily diffuses on the surface at a relatively low temperature, and thus easily aggregates even at a low temperature to form a fine uneven shape having a small grain size. Therefore, silver having a low melting point (surface diffusion starting temperature of 97 ° C.) is preferable to metal having a high melting point, for example, tungsten W having a high surface diffusion starting temperature of 822 ° C.

In particular, in the film forming process of a general magnetic recording medium, the heating temperature is 250 ° C. or lower, so that the aggregation layer 3
The diffusion temperature when forming 2 is required to be 300 ° C. or lower at most, and from this point as well, it is desirable to use a low melting point material.

[Concavo-convex enhancement layer 33] The concavo-convex enhance layer 33 is a layer for increasing (enhancing) the height of the concavo-convex shape of the surface formed on the aggregation layer 32,
By forming the unevenness enhancing layer 33, it is possible to further reduce the particle size near the top of each unevenness,
The storage resolution can be further improved. As a material for the unevenness enhancement layer 33, a material containing an element having an atomic radius smaller than that of the metal used for the aggregation layer 32 can be used. For example, the unevenness enhancement layer 33 may be formed as a layer made of C, B, or P, or a layer made of a compound containing these elements (SiC or the like). The thickness of the unevenness enhancement layer 33 is about 1 nm.

The above non-magnetic intermediate layer 3 is composed of the three layers of the dielectric layer 30, the aggregation layer 32, and the unevenness enhancement layer 33. The total thickness of these three layers is about 2 nm. Since the distance between the backing layer 2 and the recording layer 4 can be made considerably short, the recording resolution and the SNR can be improved also from this point.

[Recording Layer 4] The recording layer 4 has a magnetization easy axis in the perpendicular direction and records information. This layer is made of the same material (TbFeCo film, Pd / Co multilayer film) as conventional materials.
FePt film, CoCrPt-based alloy film, etc.) can be used. The film thickness of this layer 4 may be about 13 nm.

[Protective Layer 5] The protective layer 5 is a layer for preventing the recording layer 4 from being scratched, and is made of, for example, SiN.
Film, multilayer film of SiN and C, C film, Y-SiO ₂ film, A
An IN film or the like can be used. The film thickness is 1 nm
Approximately 3 nm. FIG. 3 shows a multilayer film including a SiN film (2 nm) and a C film (1 nm).

[Cross-Sectional Structure of Medium] FIG. 4 is a schematic cross-sectional view of a medium according to Example 1 of the present invention. FIG. 4 shows the aggregation layer 32.
The portions up to the unevenness enhancement layer 33 are shown in order to show the appearance of the unevenness such as. As shown in the figure, the surface of the dielectric layer 30 is almost flat, but the agglomeration layer 32 is formed of fine particles, and the height of the uneven shape of the fine particles is increased on the aggregation layer 32. Concavo-convex enhancement layer 3
3 is formed. When the recording layer 4 is formed on the uneven shape of the uneven enhancement layer 33, each uneven shape can be used as a recording unit of magnetization. Since the unit shape of the unevenness is much smaller than the unevenness formed on the surface of the intermediate layer of the conventional medium (see FIG. 21), the recording resolution can be made higher than the conventional one.

[Medium Manufacturing Method] Next, a medium manufacturing method according to the first embodiment of the present invention will be described. As the manufacturing device, almost the same as the conventional one can be used,
For example, a DC magnetron sputtering device can be used. For the film formation of each layer, this device is set to a predetermined vacuum degree, the target of the material to be formed and the substrate are put in the device, and while the substrate is revolving, the reaction gas is allowed to flow at room temperature in principle. It was performed by sputtering.

(1) Formation of Backing Layer 2 First, a soft magnetic film to be the backing layer 2 is formed on a substrate. For example, a FeC film which is a soft magnetic film is formed on a substrate by separately arranging an Fe target and a C target in a sputtering apparatus and simultaneously performing co-sputtering. As the film forming conditions, the gas pressure of the sputtering gas Ar is 0.
16 Pa, Fe input power 370 W, C input power 330
W, sputter rate 19.3 nm / min. As a result, a FeC film having a thickness of about 300 nm is formed.

(2) Formation of Dielectric Layer 30 Next, the dielectric layer 30 is formed on the soft magnetic film 2. For example, in the case of a SiN film, Si is used as a target, Ar gas and N ₂ gas are used as a sputtering gas, the sputtering rate is 14 nm / min, the gas pressure is 0.32 Pa, the flow rate ratio of Ar and N ₂ is 2: 1, and the input power is 500 W. A film is formed by sputtering under the following conditions. This gives a thickness of 0.5 nm
A SiN film of about a certain degree is formed.

In the case of an AlN film, Al is used as a target, Ar gas and N ₂ gas are used as a sputtering gas,
Other conditions are the same as for the SiN film, and sputtering is performed. Further, in the case of a SiOx film, sputtering is performed using a Si target, Ar gas and O ₂ gas at a flow rate ratio of Ar and O ₂ of 2: 1. Here, when changing the oxygen content, the flow rate ratio may be changed.

(3) Formation of Aggregation Layer 32 Next, the aggregation layer 32 is formed on the dielectric layer 30. Here, after forming the dielectric layer 30 and before forming the aggregation layer 32, in order to promote aggregation, the medium is heated to about 200 ° C. and exposed to oxygen. After that, for example, using an Ag target and Ar gas, the sputtering rate is 7.5 nm / min, the Ar gas pressure is 1.5 Pa, and the input power is 35.
When sputtering is performed under the condition of W, the thickness is 0.5n
An agglomeration layer having a fine concavo-convex shape with a height of about m and a height of about 0.5 nm is formed.

(4) Formation of Concavo-convex Enhancement Layer 33 Next, the concavo-convex enhancement layer 33 is formed on the aggregation layer 32. For example, using a C target having a relatively small atomic radius and Ar gas, a sputtering rate of 5.0 nm / min,
Sputtering is performed under the conditions of Ar gas pressure of 0.5 Pa and input power of 1000 W. Thereby, carbon C is laminated so as to increase the height of the uneven shape of the aggregation layer 32,
The unevenness enhancing layer 33 having a thickness of about 1 nm is formed.

(5) Formation of Recording Layer 4 Next, the recording layer 4 is formed on the unevenness enhancing layer 33. For example, using a TbFeCo target and Ar gas, the sputter rate is 30.9 nm / min, the Ar gas pressure is 0.
Sputtering is performed under the conditions of 5 Pa and an input power of 440 W. As a result, TbFeCo having a thickness of about 13 nm is obtained.
The film 4 is formed.

(6) Formation of Protective Layer 5 Finally, the protective layer 5 is formed on the recording layer 4. For example, a SiN film having a thickness of about 2 nm is first formed by sputtering using Si as a target, and a C film having a thickness of about 1 nm is formed thereon by sputtering using C as a target. Here, Ar gas is used as the sputtering gas, and the sputtering rate is 5.0 n.
m / min, Ar gas pressure 0.5 Pa, input power 1000 W.

The medium of Example 1 is formed by the above steps (1) to (6). Here, the total thickness of the non-magnetic intermediate layer 3 is about 2 nm, and the distance between the backing layer 2 and the recording layer 4 can be considerably close to that of the conventional medium (about several tens of nm). Since the distance between the backing layer 2 and the recording layer 4 is short, a larger reproduction signal can be obtained, and
Since the distance between the backing layer 2 and the recording head can be reduced, the magnetic field distribution of the recording magnetic field becomes steep, and information can be recorded without disturbing the edge of the reproduction signal, which leads to an improvement in SNR. Further, as shown in FIG. 4, the surface of the non-magnetic intermediate layer 3 can be made into a fine uneven shape. Example 1
Since the medium (1) has such a structure, it is possible to improve recording resolution and SNR as described later.

[Recording resolution and SNR of medium of Example 1]
Next, the recording resolution and SNR for the medium of Example 1 of the present invention will be described. FIG. 6 shows a comparison diagram of characteristic values of various information recording media. SNR (Signal to Noise Ra
tio) represents the ratio of the reproduced signal (S) and the medium noise (N). Generally, the larger the SNR, the smaller the medium noise and the better the reproduced signal can be reproduced. Where SN
The unit dB of R means quality and corresponds to the recording mark density. SNR can be measured using a hard disk tester.

D50 is a parameter indicating the recording resolution. The larger this value, the higher the resolution and the higher the recording density. The unit (kFCI) of D50 means the 50% value of the maximum amplitude, and corresponds to the linear recording density. The surface roughness Ra is a parameter indicating the roughness of the surface of a predetermined layer of each medium, and the larger this value, the more uneven the surface. The surface roughness Ra can be measured using an AFM (atomic force microscope). In the media of Example 1 and Example 2 of FIG. 6, the surface roughness on the surface of the unevenness enhancement layer is shown. In addition, Comparative Examples 7 to 12
Indicates the surface roughness on the surface before forming the recording layer (TFC).

The unevenness height (P-V: Peak to Valley maximum height difference) is a parameter indicating the height of uneven particles formed on the surface after forming the unevenness enhancing layer in Examples 1 and 2. Yes, the larger this value, the higher the height of the particles. The uneven height can be measured using an AFM (atomic force microscope).

The average particle diameter indicates the average diameter of the irregularly shaped particles in the vicinity of the apex, and the smaller this value is, the smaller the particles are and the finer the irregularly shaped particles are formed. The average particle size can be measured using an AFM (atomic force microscope). Further, σ is a parameter that represents the uniformity of the surface, that is, the degree of unevenness of the uneven shape formed on the surface, and the smaller this value, the less uneven the unevenness of the position of the uneven particles, and the more uniform the formed. Means that. σ is AFM (atomic force microscope)
Can be used for measurement. In addition, Comparative Example 7 of FIG.
The uneven heights (P-V), the average particle diameters, and σ in the items 12 to 12 are numerical values for the uneven shape of the surface before forming the recording layer (TFC).

Here, in order to increase the density of the medium, the recording resolution D50 is large, the signal ratio SNR is large, the surface roughness Ra is not extremely small, and the unevenness height (PV) is high. It must be large, the average particle size small, and σ small. In particular, it is desirable that the completed information recording medium has a large recording resolution D50 and a large SNR. Note that the gap length was 0.08 μm and the core width was 0.27 μm for the measurement of these parameters.
Read head, gap length 0.17 μm, core width 0.
A 45 μm write head was used.

The two media of Example 1 (N
o. 1, No. 2) is on the dielectric layer 30 (SiN),
The figure shows that the aggregate layer made of Ag, which is a low melting point material, and the aggregate layer made of W, which is a high melting point material, are formed. Comparative Example 7 shows a conventional medium having a backing layer. When comparing this with two Example 1, the recording resolution (D50 = 387, 315) and SNR of Example 1 are compared.
(= 16.39, 14.11) are both Comparative Example 7
Greater than (D50 = 289, SNR = 13.5),
You can see that it has been improved. Also, two examples 1
And Comparative Examples 9 and 10 having the aggregation layer 32 but not the unevenness enhancing layer 33, the medium of Example 1 is
It can be seen that both 50 and SNR are improved.

As described above, in Example 1 of the present invention, both the D50 and the SNR are greatly improved because the dielectric layer 30, the aggregation layer 32 and the unevenness enhancing layer 33 are present. Conceivable. Therefore, when a medium (Comparative Example 8) in which only the dielectric layer 30 is added on the backing layer 2 is prepared as compared with Comparative Example 7 which is a conventional medium, as shown in FIG. It has been found that both SNR are improved. Here, the film thickness of the NiP film was set to 5 nm.

Further, comparing the average particle size of the particles formed on the surface of the NiP film of Comparative Examples 7 and 8 with σ, the dielectric film 30
In Comparative Example 8 with (SiN), both the average particle size and σ are smaller, and it can be seen that fine irregularities are formed on the surface of the NiP film. That is, it can be said that since the dielectric film 30 (SiN) is present, a fine uneven shape can be formed above it. This is because the surface tension of the dielectric layer 30 is the NiP formed on the backing layer 2 and the dielectric layer.
It is thought that this is due to the fact that it is smaller than the surface tension of the film.

This can be seen by comparing the characteristic values of the media shown in FIG. The characteristic values in FIG. 7 are characteristic values in the surface structure before the recording film and the protective film are formed. N in FIG.
o. 21 and No. 21. No. 22, comparison with No. 22. 23 and No. Two
According to comparison with No. 4, the average grain size and σ of the samples with the dielectric layer 30 added (No. 22, No. 24) are smaller. In addition, No. 1 in FIG. 23, No.
Reference numeral 24 is a medium in which Cr is formed instead of NiP as the intermediate layer.

FIG. 8 is a graph showing changes in the average particle diameter of the medium of Comparative Example 8 when the film thickness of the dielectric layer 30 (SiN) is changed. FIG. 9 shows the surface roughness R of the medium of Comparative Example 8 when the film thickness of the dielectric layer 30 (SiN) was changed.
The graph of a and the change of the uneven | corrugated height (PV) are shown. Figure 8
According to the above, when the film thickness of SiN is 0.4 to 1 nm, the average particle diameter is almost constant (about 45 nm).

According to FIG. 9, the film thickness of SiN is 0.5 nm.
At ~ 1 nm, surface roughness (Ra), unevenness height (P-V)
In both cases, the rate of change (rate of decrease) is small. Therefore, if the dielectric layer 30 is too thin, the average particle size becomes large, which is not preferable, and if it is too thick, Ra and P-V gradually decrease, and in either case, the resolution cannot be improved. Therefore, it is considered from FIG. 8 and FIG. 9 that the dielectric layer 30 preferably has a film thickness of about 0.4 nm to 1 nm.

Further, in FIG. 6, when two Examples 1 are compared, one using a low dielectric material (Ag) (No.
No. 1) uses a high melting point material (W) (NO.
Recording resolution D50 and SNR are both larger than 2),
It shows good characteristics.

In FIG. 7, No. The medium of No. 25 (high melting point material) is No. 25 in FIG. 1 corresponds to the medium of Example 1,
No. No. 26 medium (low melting point material) is No. 26 in FIG. 2 corresponds to the medium of Example 1, but this No. 25 and No. Two
No. 6 medium is compared. The surface roughness Ra, the unevenness height (P-V), and the average particle diameter of the medium of No. 26 are all smaller, and the use of the low melting point material as the aggregation layer 32 leads to the formation of fine unevenness. It can be said to be advantageous.

As described above, although the low melting point material is preferable for the aggregation layer 32, a low melting point alloy other than a metal such as Ag can be used. For example, if an alloy having a diffusion temperature of the aggregation layer 32 of 300 ° C. or lower is selected,
FexPt (1-x), CoxPt (1-x): where x
> 0.8, or WxAg (1-x): where x <
0.7 can be used. Even if these alloys are used, the average particle diameter and σ can be reduced, and fine irregularities can be formed on the surface, as in Comparative Example 26 in FIG. 7.

Next, it will be explained that by forming the unevenness enhancing layer 33, the height of the fine unevenness formed on the surface of the aggregation layer 32 can be increased. In Comparative Examples 27 to 30 of FIG. 7, the unevenness enhancing layer 3 is formed on the aggregation layer 32.
3 shows the respective characteristic values when the C film is formed.
Here, as the aggregation layer 32, W, AlTiSi, Ag7
0Pd20Cu10, Ag is used.

Comparing the four comparative examples 27 to 30 with the comparative examples 25 and 26 in which the unevenness enhancing layer 33 is not formed, the comparative examples 27 to 30 have the surface roughness Ra and the unevenness height ( Both P-V) are large. That is, the surface roughness Ra is 0.51 to 0.59 nm, and the unevenness height (P-V) is about 4.0 nm. Further, according to the comparison between Comparative Examples 25 and 27 having the same aggregation layer W and the comparison between Comparative Examples 26 and 30 having the same aggregation layer Ag, Comparative Examples 27 and 30 in which the unevenness enhancing layer 33 is formed are more preferable. , The average particle size was reduced from 34 to 24 and 22 to 17, respectively, and σ was changed from 3.6 to 2.7,
It has decreased from 3.1 to 2.5.

That is, C which is the unevenness enhancing layer 33.
By forming the film, the average particle size can be reduced and the height of the unevenness of the particles can be increased. Therefore, the height of the structure can be maintained while maintaining the structure of the fine unevenness formed in the aggregation layer 32. You can see that you can only raise Further, since the average particle size is small, it can be said that the recording resolution can be improved. It is considered that this is because carbon C, which is an element having an atomic radius smaller than that of the Ag particles forming the aggregation layer 32, is laminated. In Example 1 and the comparative example, C is used as the material of the unevenness enhancement layer 33, but even if the element B or P having a small atomic radius as described above is used, the characteristic values shown in FIG. A similar trend was obtained.

In the medium of Example 1 of the present invention, the non-magnetic intermediate layer 3 is formed as a thin multi-layered film consisting of three layers of the dielectric layer 30, the aggregation layer 32, and the unevenness enhancement layer 33. Of the recording layer (D
50) and SNR can be improved.

<Second Embodiment> FIG. 2 shows a second embodiment of the present invention.
3 is a block diagram of the information recording medium of FIG. Here, the non-magnetic intermediate layer 3 is composed of four multilayer films, and the base point forming layer 31 is formed on the dielectric layer 30, which is different from the first embodiment. [Structure of Medium of Example 2] The base point forming layer 31 is a layer in which minute nuclei are formed as base points of uneven particles formed in the aggregation layer 32. In order to improve the recording resolution, it is preferable that the concavo-convex shape formed on the aggregation layer 32 be made as fine as possible and formed uniformly and in large numbers.

By the way, Ag used for forming the aggregation layer 32
Low melting point materials such as
The period of the uneven shape is not so short, and it cannot be said that a large number of uneven particles are formed. Therefore,
Before forming the aggregation layer 32, it is preferable to improve the recording resolution by forming as many nuclei as the nuclei on which the uneven particles grow, on the dielectric layer 30.

From this point of view, therefore, in Example 2 of the present invention, a thin film (that is, the base point forming layer 31) having a slow sputter rate, being easy to react with oxygen or nitrogen, and having a larger surface tension than oxides and nitrides. , Nuclei that are formed on the dielectric layer 30 and serve as the basis for forming the uneven particles of the aggregation layer 32. As a material for forming the base point forming layer 31, for example, Ti, V, Cr, Nb, Ta, Mn or the like can be used. In particular, as a material that easily reacts with oxygen or nitrogen, a material having a low electronegativity is preferable, and a material having an electronegativity of less than 1.8 is preferable from the viewpoint of forming many nuclei. The above-mentioned six metals from Ti to Mn are all materials having an electronegativity of less than 1.8 and a relatively large surface tension.

[Method of Forming Base Point Forming Layer 31] The base point forming layer 31 is formed by the same method as that of the first embodiment.
To increase the agglomeration of base points,
C.) and oxygen, and then sputtering is performed thereon. For example, using a Cr target and Ar gas, the sputter rate is 2.8 nm.
If the sputtering is carried out under the conditions of / min and an input power of 40 W, the base point forming layer 31 (Cr film) having a film thickness of about 0.5 nm.
Can be formed.

[Cross-sectional Structure of Medium of Second Embodiment] FIG. 5 is a schematic cross-sectional view of a medium of a second embodiment of the present invention. This shows a schematic shape from the soft magnetic film 2 to the concave-convex enhance layer. In the base point forming layer 31, fine particles serving as base points are formed on the dielectric layer 30. This Example 2
Then, on the base point forming layer 31, the aggregation layer 32, the unevenness enhancing layer 33, the recording layer 4, and the like as in the first embodiment.
The protective layer 5 is formed to complete the medium.

FIG. 3 shows typical materials of the medium of Example 2 and the film thickness of each layer. In the second embodiment, the non-magnetic intermediate layer 3 is composed of four layers (30 to 33), and the film thickness is about 2.5 nm in total. Therefore the backing layer 2
Since the distance between the recording layer 4 and the recording layer 4 is as thin as about 2.5 nm, the magnetic effect due to the presence of the backing layer can be sufficiently exerted.
It is possible to improve SNR and the like.

[Recording resolution and SNR of the medium of Example 2]
FIG. 6 shows the film structure and respective characteristic values of the medium of Example 2 of the present invention. No. 6 in FIG. 3 and No. No. 5 is an example in which the low melting point material Ag is used for the aggregation layer 32, No. 4 and No. No. 6 is an example in which the high melting point material W is used for the aggregation layer 32, No. 5 and No. 6
Shows an example in which SiC is used for the unevenness enhancement layer 33. Each of these four Examples 2 has a higher recording resolution and SNR as compared with Comparative Example 7 which is a conventional medium. In particular, an example using a low melting point material for the aggregation layer 32 (N
o. 3, No. 5) has a recording resolution D50 of 410,
The SNR is as high as 408 and the SNR is as high as 17.63 and 17.52, and the improvement effect is remarkable.

FIG. 7 shows four comparative examples 31 to 34 in which a Cr film is formed as the base point forming layer 31. Compared with comparative examples 27 to 30 having no base point forming layer 31, the surface roughness Ra, All the characteristic values of the height of unevenness (P-V), the average particle diameter, and σ are small. In particular, since the average particle size and σ are small, it can be seen that the unevenness shape of the surface of the unevenness enhancement layer 33 is small and can be formed uniformly. That is, by forming the base point formation layer 31, finer uneven shapes can be uniformly formed, so that high resolution and SNR are achieved.
Can be improved. As described above, also in Example 2 of the present invention, since the nonmagnetic intermediate layer composed of four layers is formed as a thin film on the backing layer, the recording resolution and the SNR can be improved.

[0065]

According to the present invention, since the non-magnetic intermediate layer composed of the multilayer film including the dielectric layer is formed between the backing layer and the recording film, the recording resolution and SNR of the recording layer are improved. Can be made.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an information recording medium according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of an information recording medium according to a second embodiment of the present invention.

FIG. 3 shows representative examples of materials and film thicknesses of media of Examples 1 and 2 of the present invention.

FIG. 4 is a sectional configuration diagram of a part of the medium according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional configuration diagram of a part of the medium of Example 2 of the present invention.

FIG. 6 is a comparison diagram of characteristic values of various information recording media including Examples 1 and 2 of the present invention.

FIG. 7 is a comparison diagram of characteristic values of media prepared as comparative examples in the present invention.

FIG. 8 is a graph of average particle diameter when the film thickness of the dielectric layer is changed in one example of the present invention.

FIG. 9 is a view showing an example of the present invention in which the surface roughness Ra and the unevenness height (PV) when the film thickness of the dielectric layer is changed.
Is a graph of.

FIG. 10 is a block diagram of a conventional magnetic information recording medium.

FIG. 11 is a sectional configuration diagram of a part of a conventional magnetic information recording medium.

[Explanation of symbols]

1 substrate 2 backing layer 3 Non-magnetic intermediate layer 4 recording layers 5 protective layer 30 Dielectric layer 31 Base point forming layer 32 Aggregation layer 33 Concavo-convex enhancement layer

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Claims (7)

[Claims] 1. A backing layer having an easy axis of magnetization in the in-plane direction, a non-magnetic intermediate layer having fine irregularities formed on the surface, and a recording magnetic layer for recording information having an easy axis of magnetization in the vertical direction. Are formed in this order, and the non-magnetic intermediate layer, in order from at least the side closer to the backing layer, the dielectric film layer, the aggregating layer for forming fine irregularity-shaped particles, and the particle height of the aggregating layer. An information recording medium, comprising an unevenness enhancing layer for increasing the height. 2. The information recording medium according to claim 1, wherein the surface tension of the aggregation layer is larger than the surface tension of the dielectric layer. 3. The information recording medium according to claim 2, wherein the aggregation layer is made of a metal film or an alloy film. 4. The information recording medium according to claim 1, 2 or 3, wherein the unevenness enhancing layer is formed of a material containing an element having an atomic radius smaller than that of the material of the other layers. 5. A base point forming layer for forming a nucleus serving as a base point of particles formed in the aggregation layer is further provided between the dielectric film layer and the aggregation layer. Item 1. The information recording medium according to item 1, 2, 3 or 4. 6. A method of forming an information recording medium comprising a backing layer, a non-magnetic intermediate layer, and a perpendicular magnetization recording magnetic layer formed in this order on a substrate, wherein the backing layer is formed by co-sputtering a soft magnetic material. The non-magnetic intermediate layer is formed by forming a dielectric layer by sputtering a non-magnetic material and a reactive gas, performing a predetermined heat treatment, and then forming a cohesive layer on the metal or alloy material by sputtering. A method for forming an information recording medium, which comprises forming a concavo-convex enhancement layer by forming a film and sputtering an element having an atomic radius smaller than that of a metal on the film. 7. The method for forming an information recording medium according to claim 6, wherein a step of forming a base point forming layer is introduced between the heat treatment and the aggregation layer forming step.