JP2003091809A - Substrate for information carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for an information carrier by which the deformation of the information carrier is lessened and the reliability of transfer is improved when the information carrier and a hard disk closely stuck to each other by superposition. SOLUTION: The substrate for the information carrier for forming a ferromagnetic body on the surface thereof for the purpose of transferring and recording a magnetization pattern of an information signal onto a magnetic recording medium consists of ceramics consisting essentially of silicon carbide and having <=0.1 mass% sum total content of iron, chromium and nickel expressed in terms of metal, <=0.1% porosity, <=1 μm of maximum pore size and >=350 GPa Young's modulus. The ceramics preferably has <=1 nT of magnetic susceptibility.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an information carrier substrate suitably used as a master information carrier for recording a predetermined information signal on a magnetic recording medium.

[0002]

2. Description of the Related Art In recent years, a magnetic recording / reproducing apparatus is required to have a small size and a large capacity, so that high density recording is performed. In order to perform this high density recording, it is necessary to accurately write the position information (servo pattern) necessary for controlling the movement of the recording / reproducing head to the disk.

Generally, a servo track writer device gradually moves a recording / reproducing head to write a servo pattern corresponding to each track on a disk. However, this method has a drawback that the accuracy of the writing position cannot be sufficiently obtained because the head is moved in a sequential manner to write the servo pattern.

Therefore, a magnetic portion made of a ferromagnetic material is formed on the surface of the base body in a pattern shape corresponding to the information signal to form a master information carrier, and the surface of this master information gallbladder is formed into a ferromagnetic thin film or a ferromagnetic thin film. A magnetic pattern having a pattern corresponding to the information signal formed on the information carrier formed on the master information carrier by contacting the surface of the sheet-shaped or disk-shaped magnetic recording medium on which the powder coating layer is formed and applying a predetermined magnetic field. There has been proposed a method of recording the data on a magnetic recording medium.

In the recording of information symbols using such a magnetic transfer technique, magnetic recording is a method in which an array pattern for an information signal provided on a master information carrier is transferred and recorded as a magnetization pattern onto a magnetic recording medium at once. It is important that a high density information signal is uniformly and stably recorded over the entire medium.

For example, a non-magnetic material such as a Si substrate, a glass substrate, or a plastic substrate is used as a master information carrier, and a ferromagnetic thin film is formed on this substrate by a method conforming to the semiconductor manufacturing process. JP-A-13-34938 discloses that the surface of a ferromagnetic thin film is made substantially flat in order to improve the adhesion between the carrier and the magnetic recording medium.

[0007]

However, according to the method disclosed in Japanese Patent Laid-Open No. 13-34938, this information carrier is superposed on a hard disk made of aluminum or a glass substrate, and the space between the information carrier and the hard disk is evacuated to make a close contact. Since the transfer is performed after improving the transferability, the master information carrier is deformed when the vacuum is exhausted, and as a result, the reliability of the transfer recording is low.

Therefore, an object of the present invention is to provide an information carrier substrate in which the deformation of the information carrier is reduced when the information carrier and the hard disk are superposed and brought into close contact with each other, and the reliability of transfer is improved.

[0009]

According to the present invention, by using a material mainly composed of silicon carbide, the characteristics and texture of which are controlled, as a base material for an information carrier, deformation of a master information carrier at the time of transfer is suppressed, and transfer recording is performed. It is based on the finding that the reliability of can be significantly improved.

That is, the information carrier substrate of the present invention is an information carrier substrate for forming a ferromagnetic material on the surface for transferring and recording a magnetization pattern of an information signal on a magnetic recording medium, and is a silicon carbide crystal. And ceramics whose total content of iron, chromium and nickel is 0.1% by mass or less in terms of metal, porosity is 0.1% or less, maximum pore diameter is 1 μm or less, and Young's modulus is 350 GPa or more. It is characterized by that.

In particular, the magnetic susceptibility of the ceramic is 1 nT.
The following is preferable. As a result, the disturbance of the external magnetic field at the time of transfer can be reduced and highly reliable transfer can be performed.

The average minor axis of the silicon carbide crystals is 10
It is preferable that the average major axis is 150 μm or less. This increases the strength of the information carrier substrate,
Highly reliable transfer can be performed.

Furthermore, the surface roughness Ra of the main surface of the ceramic is preferably 1 nm or less. As a result, an array pattern of highly reliable ferromagnetic material can be formed on the carrier.

Furthermore, the flatness of the main surface of the ceramic is preferably 10 μm or less. As a result, a highly reliable array pattern of ferromagnetic materials can be formed on the information carrier substrate, and highly reliable transfer can be performed.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The ferromagnetic substance-forming substrate of the present invention comprises:
It is used as a substrate for forming a ferromagnetic material of a master information carrier for transferring and recording a magnetization pattern of an information signal on a magnetic recording medium, and is characterized by being a ceramic mainly composed of silicon carbide crystals.

Further, according to the present invention, it is important that the total content of iron, chromium and nickel in the ceramic mainly composed of silicon carbide crystal is 0.1% by mass or less in terms of metal. . This is because if a large amount of these elements (iron, chromium and nickel) is contained, the magnetic susceptibility of the silicon carbide body is increased, so that incorrect information is recorded when magnetic information is transferred, and this error is reduced. Therefore, the total content of the above elements is preferably 0.01% by mass or less, and more preferably 0.001% by mass or less.

It is also important that the porosity is 0.1% or less. When the porosity exceeds 0.1%, the maximum pore diameter becomes large and the surface roughness also becomes large. When used as a master information carrier, when it is brought into contact with the surface of the disk-shaped magnetic recording medium, the portion actually contacted And the reliability of the transfer of the array pattern by the ferromagnetic material is reduced. In order to improve this reliability, the porosity is particularly preferably 0.05% or less.

Further, the maximum pore diameter of ceramics is 1 μm.
It is also important that it is m or less. The line width of the ferromagnetic material formed on the substrate varies depending on the signal pattern at the time of writing, but is as fine as several tens nm to 0.5 μm. Therefore, by reducing the maximum pore diameter, it is possible to reduce the defects of the signal pattern formed on the carrier and to enhance the reliability as the master information carrier. In order to improve reliability, the maximum porosity is particularly preferably 0.5 μm or less.

Furthermore, the Young's modulus of the ceramic is 3
It is also important that it is 50 GPa or more. The Young's modulus of conventional Si is approximately 150 GPa, and that of glass substrates is 1
It is as small as 00 GPa or less. Therefore, Young's modulus is 350G
By making Pa about 2.3 to 3.5 times, the amount of deformation when the same stress is applied can be reduced to 1/2 or less,
The deformation of the substrate can be reduced, and as a result, the reliability of transfer can be improved. In order to improve reliability, the Young's modulus is particularly preferably 400 GPa or more, further preferably 450 GPa or more.

Further, according to the present invention, the magnetic susceptibility of the above ceramics used as the information carrier substrate has a magnetic susceptibility of 1 nT.
(Tesla) or less, particularly 0.5 nT or less, and further 0.1 n
It is preferably T or less. That is, for example, a ferromagnetic material such as Fe, Co, or Fe—Co alloy is formed on the information carrier substrate, but in order to generate a sufficient recording magnetic field,
The higher the magnetic susceptibility of the magnetic material, the better, and a magnetic material of 1T or more is used. Therefore, by suppressing the magnetic susceptibility of the information carrier substrate to 10 ⁻⁹ or less of that of the magnetic material, it is possible to reduce the disturbance of the leakage magnetic field with respect to the external magnetic field at the time of transfer and further improve the reliability of transfer.

Furthermore, the silicon carbide crystal, which is the main crystal of the ceramics constituting the information carrier substrate of the present invention, has an average minor axis of 10 μm or less, particularly 5 μm or less, and an average major axis of 150 μm.
It is preferably m or less, and particularly preferably 50 μm or less. The particle size of silicon carbide crystals is related to strength, and the average minor axis is 10 μm.
If it exceeds, the crack may occur due to a slight deformation when the information carrier substrate is sucked. Furthermore, the average major axis is 150
If it exceeds μm, a crack may occur due to a slight deformation when the information carrier substrate is sucked. Therefore, in order to increase the strength of the information carrier substrate and transfer with high reliability, it is desirable that the particle diameter be within the above range.

The surface roughness Ra of the information carrier substrate of the present invention is preferably 1 nm or less, more preferably 0.5 nm or less. Since the thickness (d) of the ferromagnetic film formed on the information carrier substrate is about several tens nm, the surface roughness Ra of the information carrier substrate is controlled to be d / 10 or less, so that the information carrier substrate The reliability of the formation of the array pattern can be improved.

Furthermore, it is preferable that the flatness of the main surface of the above-mentioned ceramics is 10 μm or less, particularly 5 μm or less. When an information signal is transferred and recorded from the information carrier to the magnetic recording medium, the magnetic recording medium is brought into contact with the surface of the information carrier (hereinafter referred to as the contact surface). Contact condition in the part deteriorates,
Information may be erroneously transferred, and in order to avoid this, the flatness is preferably 10 μm or less. Therefore, it is preferable that the major surface of the information carrier substrate, which is the main body of the information carrier, be 10 μm or less. As a result, a highly reliable array pattern of ferromagnetic materials can be formed on the information carrier substrate, and highly reliable transfer can be performed.

Thus, the information carrier substrate of the present invention is
It is made of ceramics mainly composed of silicon carbide crystals, has high purity and high Young's modulus, has low porosity and excellent surface smoothness, and can be processed using semiconductor manufacturing processes. It can be preferably used as a substrate of a master information carrier for transferring and recording the magnetization pattern of (1) on a magnetic recording medium.

Next, a method of manufacturing the information carrier substrate of the present invention will be described.

According to the present invention, the ceramics which constitutes the information carrier substrate and has silicon carbide crystals as main crystals is iron,
The total content of chromium and nickel is 0.1 in terms of metal
Mass% or less, porosity 0.1% or less, maximum pore size 1μ
If the Young's modulus is m or less and the Young's modulus is 350 GPa or more, the manufacturing method thereof should not be limited.

For example, a high-purity sintered body using a fine silicon carbide raw material produced by a method such as a hot pressing method or a pulse energization sintering method in which pressure sintering is performed while energizing, carbon and boron, alumina or A sintered body using a rare earth oxide or the like as a sintering aid, a sintered body produced by impregnating silicon with silicon carbide, or the like can be manufactured.

Further, it is also possible to manufacture ceramics mainly composed of silicon carbide crystals by a vapor phase synthesis method such as a CVD method (chemical vapor deposition method).

Since the information carrier substrate of the present invention has a uniform structure, it is easy to obtain a smooth surface in ion irradiation processing such as ion milling and reactive ion etching and machining, and it is also highly pure. It is particularly preferable to use the CVD method because the nickel content can be easily reduced and the pores can be easily removed.

The ceramics produced by the CVD method are formed on a substrate, but the substrate can be removed after the formation and used as the above ceramics. Note that C
The VD method includes a thermal CVD method, a plasma CVD method, which are classified according to a supply form of energy supplied for a chemical reaction,
There are various methods such as a photo CVD method and a laser CVD method, but any method may be used.

Of these, the thermal CVD method, which is capable of high-speed film formation represented by thermal CVD, is preferable because the substrate is removed to form a self-stereoscopic body of 1 mm or more. This gives 1
Ceramics having a thickness of mm or more can be manufactured in a short time. Further, in consideration of the efficiency of raw materials, a cold wall type CVD apparatus is preferable for cost reduction, and a hot wall type CVD apparatus capable of forming a uniform film on a relatively large product is also preferable.

The method of manufacturing the information carrier substrate of the present invention will be described below using the thermal CVD method.

First, a disk-shaped carbon substrate is prepared as a film forming substrate. This carbon substrate is suitable because it can be easily removed, but a metal such as Mo or W, a metal compound, or the like may be used as the film formation substrate.

Next, the carbon substrate is placed in a reaction furnace of a CVD apparatus, and a silicon-containing gas is used as a reaction gas.
A carbon-containing gas and a carrier gas are prepared.

As the silicon-containing gas, SiCl ₄ , Si
H ₄ , SiHCl ₃ or the like may be used. As the carbon-containing gas, CH ₄ , C ₂ H ₂ , C ₂ H ₄ , C ₂ H ₆ , C ₃ H ₈ or the like may be used. The silicon-containing gas may also contain carbon, for example, CH ₃ SiCl ₃ , (CH ₃ ) ₂ SiC.
L ₂ , (CH ₃ ) ₄ Si or the like may be used together with a carrier gas. As the carrier gas, hydrogen, nitrogen, argon (Ar), helium (He) or the like can be used.

Methyltrichlorosilane (CH ₃ SiCl ₃ : as a gas containing carbon and silicon: hereinafter, MTS
The case of using hydrogen (H ₂ ) as a carrier gas will be described.

In the case of CVD, the inside of the device is
After evacuation to a or less, the temperature is raised to the CVD temperature while flowing H ₂ . Since the CVD temperature controls the orientation, 120
0 ° C. to 1800 ° C., particularly 1300 to 1600 ° C. are preferable. Next, the reaction furnace is kept at the CVD temperature, MTS is introduced into the furnace, and the furnace pressure is 0.5 to 40 kPa, especially 1 to 15
kPa is preferable in terms of high speed film formation.

The CVD conditions for producing the information carrier substrate of the present invention depend on the apparatus type and the substrate size, but M
It can be manufactured by controlling the conditions within a range of TS flow rate of 0.5 to 5 l / min and MTS / H ₂ flow rate ratio of 0.1 to 1. Under these conditions, the CVD reaction proceeds, and silicon carbide crystals can be efficiently deposited on the film formation substrate.
Note that the obtained sample can be subjected to heat treatment at a temperature higher than the CVD temperature, if desired, in order to reduce the residual stress.

Further, after the silicon carbide is formed on the film-forming substrate as described above, the film-forming substrate is removed to remove silicon carbide existing in a region of at least 0.1 mm or more from the interface with the film-forming substrate. The ceramic substrate is manufactured by removing it by machining or oxidation. By removing the silicon carbide crystal near the interface as described above, the internal stress can be further reduced by removing the so-called pre-steady-state structure formed at the initial stage of film formation. As a result, the surface of the information carrier substrate of the present invention can be easily processed, and a flatness of 10 μm can be easily obtained.

Although the CVD apparatus used in the present invention is not particularly limited, in order to form a film at a high speed, a high frequency induction heating system is adopted, and a jig or a substrate support which does not easily absorb a high frequency is used. It is preferable to use a mold in which only the substrate and its vicinity are maintained at a high temperature to supply the raw material.

The silicon carbide film produced by the CVD method is preferably oriented because the surface is likely to be smooth. In particular, it is preferably oriented in (111) or (220).

[0042]

[Example] Example 1 Average crystal grain size 0.7μm, purity 90% and purity 9
For two kinds of silicon carbide powder of 9.9%, if desired
As a sintering aid, B having an average crystal grain size of 0.8 μm _FourC and F
Enol resin (B, C), Al with an average particle size of 0.2 μm
Mina and 0.9 μm yttrium oxide (Al) are added,
After the molding by the known molding method, the atmospheric pressure sintering method (NS),
Hot press method (HP) and electric heating method (PAS)
And was fired under the conditions of Table 1.

The amounts of metallic impurities of iron, chromium and nickel in the obtained sintered body were measured by ICP emission spectroscopic analysis, and the total amount was calculated to obtain the metal content.

The porosity was measured by the Archimedes method, and the maximum pore diameter was determined by observing 10 areas of 320 μm ² by SEM observation.

Further, a test piece based on JIS R1601 was cut out from a flat plate, processed, the bulk density was determined by the Archimedes method, and the Young's modulus at room temperature was determined by the ultrasonic pulse method based on JIS R1602.

Furthermore, for the surface roughness, Ra was measured using an atomic force microscope (AFM).

For the evaluation of flatness, the sample is placed on a suction port having a diameter of 30 mm, and the sample is fixed to the apparatus by evacuation. While evacuating, with a three-dimensional measuring device,
The amount of deflection of the substrate was measured.

Next, the magnetic susceptibility was measured with a vibrating sample magnetometer (VSM), and the bending strength was determined by a four-point bending test at room temperature based on JIS R1601.

The major axis and minor axis of the crystal particles can be measured by
Polish each surface until it becomes a super smooth surface,
This surface was etched in a NaOH + KNO ₃ mixed melt, and a photograph was taken with a scanning electron microscope (SEM). From the photograph, the minimum diameter of one particle was taken as the minor axis and the maximum diameter was taken as the major axis. The measurement was carried out on 30 particles, and the average value was calculated to be the values of the major axis and the minor axis, respectively.

Further, the crystal orientation was determined by X-ray diffraction to be Si.
The C peak was determined by comparison with powder X-ray. The results are shown in Table 1.
It was shown to.

[0051]

[Table 1]

Sample No. of the present invention. 1-4 and 8,10
Has a metal content of 0.09 mass% or less and a porosity of 0.1.
% Or less, maximum pore diameter is 0.9 μm or less, Young's modulus is 45
The surface roughness was 2 GPa or more, the surface roughness was 0.98 nm or less, the magnetic susceptibility was 0.8 nT or less, and the deflection amount was 67 μm or less.

On the other hand, sample No. outside the range of the present invention. 5 is
Deflection was small at 69 μm, but porosity was 0.41
%, Maximum pore size 1.2 μm, surface roughness 1.27 n
m, the metal content is 0.12% by mass, and the magnetic susceptibility is 1.1 n.
Since it is large as T, and an error is likely to occur, it was unsuitable as a substrate for an information carrier.

Further, sample No. outside the range of the present invention. 6, 7
Has a small deflection amount of 80 μm or less, but has a porosity of 0.14% or more, a maximum pore diameter of 1.1 μm or more, and a surface roughness of 1.12 nm or more, which easily causes an error and is a substrate for an information carrier. Was unsuitable as

Further, sample No. outside the range of the present invention. 9
The deflection amount was as small as 66 μm or less, but the porosity was 0.15% or more and the flatness was 22 μm, so that an error was likely to occur, and the strength was low at 230 MPa, so that the substrate for information carrier was easily cracked. Was unsuitable as Example 2 A carbon square plate having a purity of 99.99% is prepared as a film formation substrate. Then, these samples were placed in a reaction chamber in a CVD furnace, using MTS and H ₂ as reaction gases,
Under the conditions shown in Table 2, a silicon carbide film having a thickness of about 2 mm is formed on the film formation substrate. After completion of the film formation, carbon was removed from the silicon carbide by machining, and both main surfaces were polished with a diamond grindstone and a buff.

Sample No. Reference numeral 17 is a silicon substrate obtained by cutting a disk having a diameter of 50 mm and a thickness of 1 mm from a silicon ingot.

Evaluation was carried out in the same manner as in Example 1. The results are shown in Table 2.

[0058]

[Table 2]

Samples 11 to 16 of the present invention are all (1
11) and / or (220) oriented, metal content of 0.05 mass% or less, porosity of 0.05% or less, maximum porosity of 0.1 μm or less, Young's modulus of 461 GPa or more The amount was as small as 65 μm or less.

On the other hand, the sample No. consisting of a silicon crystal and outside the scope of the present invention. The sample No. 17 had a small Young's modulus of 150 GPa and a large amount of deflection of 200 μm or more.

[0061]

As a ceramic substrate for forming a ferromagnetic material of a master information carrier for transferring and recording a magnetization pattern of an information signal on a magnetic recording medium, the amount of impurities, the porosity, the maximum pore diameter and the Young's modulus are controlled. By doing so, the deformation of the substrate can be reduced and the reliability of the transfer of the magnetic pattern can be improved.

Claims (5)

[Claims] 1. An information carrier substrate for forming a ferromagnetic material on a surface thereof for transferring and recording a magnetization pattern of an information signal on a magnetic recording medium, which is mainly composed of silicon carbide crystals, and iron,
The total content of chromium and nickel is 0.1 in terms of metal
Mass% or less, porosity 0.1% or less, maximum pore size 1μ
An information carrier substrate, which is made of a ceramic having a Young's modulus of 350 GPa or more and a m or less. 2. The information carrier substrate according to claim 1, wherein the magnetic susceptibility of the ceramics is 1 nT or less. 3. The information carrier substrate according to claim 1, wherein the silicon carbide crystal has an average minor axis of 10 μm or less and an average major axis of 150 μm or less. 4. The information carrier substrate according to claim 1, wherein the main surface of the ceramic has a surface roughness Ra of 1 nm or less. 5. The flatness of the main surface of the ceramic is 10 μm.
The information carrier substrate according to any one of claims 1 to 4, wherein the substrate is m or less.