JP2001295037A - Sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sputtering target for deposition of a seed layer, with which the size of magnetic particles in a magnetic film can be refined and simultaneously the size of the magnetic particles can be uniformized, and its manufacturing method. SOLUTION: The sputtering target contains CoO crystal grains and crystal grains of divalent to tetravalent oxides, and respective crystal grains gather densely and are uniformly mixed and dispersed. This sputtering target can be manufactured by selecting CoO powder and at least one or more kinds among powder of Si oxide, such as SiO2 and SiO, powder of Ti oxide, such as TiO2, Ti2O3 and TiO3, powder of Ca oxide, such as CaO and CaO2, and powder of zinc oxide such as ZnO and subjecting these powders to ball mill kneading, drying, compacting and sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sputter target for forming a seed layer of a magnetic recording medium and a method for manufacturing the same.

[0002]

2. Description of the Related Art To increase the recording density of a magnetic recording medium,
In addition to increasing the coercive force of the magnetic material (film), it is important to reduce the unit in which the magnetization reversal of the magnetic film occurs. In order to reduce the unit of magnetization reversal, it is important to reduce the size of the magnetic particles constituting the magnetic film and to make the particle size of the magnetic particles uniform.

US Pat. No. 4,652,499 discloses a method for controlling the size and particle size distribution of magnetic particles by using a film forming technique such as DC magnetron sputtering targeting CrV to form a seed layer of a body-centered cubic CrV alloy thin film. To be provided as an underlayer of the magnetic film.

[0004]

However, the CrV
In the conventional technology of forming a CrV seed layer using a target, there is a limit in controlling the size and particle size distribution of CrV particles, and fine particles and coarse particles coexist in the seed layer. The magnetic film formed on such a seed layer includes:
Fine magnetic particles and coarse magnetic particles are mixed depending on the size and particle size distribution of CrV particles. Therefore,
The unit of magnetization reversal could not be reduced.

An object of the present invention is to provide a sputter target for forming a seed layer capable of reducing the size of magnetic particles in a magnetic film and at the same time making the particle size of the magnetic particles uniform, and a method of manufacturing the same. It is in.

[0006]

The sputter target of the present invention comprises CoO crystal particles, CoO crystal particles, and Co ₂ Si.
O ₂ crystal particles, Co ₂ TiO ₄ crystal particles, Ca ₂ SiO ₃ crystal particles, ZnO crystal particles, and other divalent to tetravalent oxides and crystal particles, and each crystal particle is densely gathered;
And are uniformly mixed and dispersed.

The composition of the sputtering target is CoO: 6
0 to 98 wt%, and at least one or more divalent to tetravalent oxides: 40 to 2 wt%. If the proportion of CoO in the sputter target is 70 wt% or less, the formed seed layer has many amorphous portions, and the particle size of the CoO crystal particles is too small. When the ratio of CoO is 98 wt% or more, the particle size of the CoO crystal particles becomes too large.

[0008] The target of the present invention is CoO powder, Si
O ₂ , SiO ₂ or other Si oxide powder, TiO ₂ , Ti ₂ O
₃ , at least one of oxide powders of Ti such as TiO ₃ , powders of Ca such as CaO and CaO _2, and powders of zinc oxide ZnO, and kneaded with a ball mill, dried and molded. It is manufactured by sintering in a vacuum of ² Pa or less or in a non-oxidizing gas atmosphere such as Ar at a temperature of 800 to 1400 ° C., a pressure of 0.1 to 10 MPa, and a time of 0.2 to 3.0 h. The raw material powder is preferably an oxide, but a carbonate compound having a low decomposition temperature such as CoCO ₃ , CaCO ₃ , or ZnCO ₃ can also be used.

The sintering is preferably performed in a vacuum of 10 ² Pa or less or in a non-oxidizing gas atmosphere such as Ar. When CoO is heated to several hundred degrees centigrade in an atmosphere in which oxygen is present, it is easily oxidized to produce Co ₃ O ₄ . Therefore, when it is desired to obtain a Co ₃ O ₄ -based target, sintering is performed in a slightly reduced pressure atmosphere from 10 ² Pa or more. On the other hand, when it is desired to obtain a CoO-based target, a vacuum of 10 ² Pa or less is preferable.

In a vacuum of 10 ² Pa or less or in a non-oxidizing gas atmosphere, CoO is not oxidized, but is reduced to produce metal Co. However, metallic Co is generated only in the surface layer of about 0.1 to 0.5 mm of the sintered body, and the internal Co is formed.
The present inventors have found that O is not reduced.
This is because the metal Co layer is a very dense film,
This is because O ₂ generated by decomposition of O cannot escape outside. After sintering, if the Co layer on the surface is scraped off, a target containing CoO crystal particles containing no metal Co can be manufactured.

As the non-oxidizing gas, Ar, He, and N ₂ are used, but Ar and N _{2 are} good in terms of cost, and Ar is most suitable because no nitriding reaction occurs. Sintering occurs from about 800 ° C., but takes about 3 hours. Sintering temperature 1400 ° C
Then sintering proceeds for about 15 minutes. However, sintering at a high temperature for a long time is not preferable because the metal Co layer becomes thick. In addition, since the melting point of metal Co is 1492 ° C., at a temperature higher than that, O ₂ generated by decomposition of CoO easily escapes and is reduced to the inside. The preferred sintering temperature is 90
0-1200 ° C.

When a target is produced from CoO powder and at least one powder selected from divalent to tetravalent oxides such as Co ₂ SiO ₄ , Co ₂ TiO ₄ and CaSiO ₄ , 10 ^In a vacuum of ² Pa or less or in a non-oxidizing gas atmosphere, at a temperature of 900 to 1400 ° C and a pressure of 0.1 to 1
It can also be produced by sintering at 0 MPa for 0.2 to 3.0 hours. However, since sintering starts at about 900 ° C., 1000 to 1200 ° C. for 1 to 2 hours is preferable.

For sintering, a normal pressure or gas pressure sintering method can be used as long as the target has a diameter of 100 mm or less. The sintering time in normal pressure or gas pressure sintering depends on the sintering temperature,
The sintering temperature is 1 to 2 hours at 1000 to 1200 ° C. When manufacturing a target with a large diameter, in a normal pressure or gas pressure sintering method, a friction force is generated due to shrinkage of the molded body in the sintering process and cracks are easily generated, so it is manufactured by a hot press or a hip. Is good.

[0014]

(Embodiment 1) A sputter target according to a first embodiment of the present invention will be described.

475 g of CoO powder, 25 g of SiO ₂ powder
Was placed in a 2 liter polyethylene pot, 5 g of PVB (polyvinyl butyrate) was added as a binder, and 400 ml of ethanol was added as a dispersion medium, followed by ball mill kneading for 20 hours. 10mm diameter for ball mill ball
Using the Si ₃ N ₄ balls.

The slurry obtained by kneading with a ball mill was placed on a stainless steel pad, air-dried in a fume hood, and then pressed at 30 MPa using a uniaxial press having a diameter of 120 mm to produce a compact.

The compact was placed in a graphite jig and hot-pressed at 950 ° C. for 1 hour under a vacuum of 10 ⁻¹ Pa and a pressure of 10 MPa to obtain a sintered body. The sintered body was covered with a metal Co layer. The sintered body was cut using a diamond cutter and its cross section was observed.
The thickness was 3 to 0.5 mm, and the inside was brownish black of CoO.
When the brownish black portion was analyzed by X-ray diffraction, only diffraction peaks based on CoO and Co ₂ SiO ₄ were detected as shown in FIG. FIG. 2 shows an SEM photograph of the brown-black portion. CoO crystal particles and Co ₂ SiO ₄ crystal particles were observed in the brownish black portion. The particle size of these crystal particles is several μm (2 to 10 μm).
m) and were almost uniformly dispersed. The relative density of this brown-black portion was about 94%, which was very dense.

By removing the coating of the metal Co layer of the sintered body, a target having CoO as a main component and Co ₂ SiO ₄ as a sub-component was produced.

Next, instead of 25 g of SiO ₂ powder, 25 g of TiO ₂ powder, which is the same divalent oxide, and CaSiO ₃
Powder 25 g, ZnO powder 25 g, or TiO ₂ is 14.
Using 25 g of a mixed powder of 3 g and 10.7 g of SiO ₂ (molar ratio: 1: 1), a sintered body was produced in the same manner as in the case of the above-mentioned SiO ₂ powder. Each sintered body has a surface of 0.2 to 0.2.
It was covered with a 7 mm thick metal Co layer, but the insides were CoO crystal particles, Co ₂ TiO ₄ crystal particles, and CoO
Crystal particles and CaSiO ₃ crystal particles, CoO crystal particles and Z
It was identified by X-ray diffraction that the particles were nO crystal particles, CoO crystal particles, Co ₂ SiO ₄ crystal particles, and Co ₂ TiO ₄ crystal particles. In addition, it was confirmed by SEM observation of the inside that the structure was dense and uniform.

By removing the coating of the metal Co layer of the sintered body, the main component is CoO, Co ₂ TiO ₄ , CaSi
O ₃ , ZnO, or Co ₂ SiO ₄ and Co ₂ TiO ₄
Was produced as a sub-component.

Further, 50 g of Co ₂ SiO ₄ powder, which is a trivalent or tetravalent oxide, and 450 g of Co ₂ Ti
50 g of O ₄ powder, 50 g of Ca ₂ SiO ₃ powder, or Co ₂
Using each of 25 g of SiO ₄ powder and 25 g of Co ₂ TiO ₄ powder, a compact was prepared in the same manner as described above, and 10 ^-1 P
When a sintered body was prepared by hot pressing at 1000 ° C. for 1 hour under a pressure of 10 MPa in the vacuum of a, a sputter target similar to that described above could be prepared. (Embodiment 2) A sputter target according to a second embodiment of the present invention will be described. In this embodiment, a sputter target is prepared by normal pressure sintering.

95 g of CoO powder and 5 g of SiO ₂ powder were placed in a 500 ml polyethylene pot, 1 g of PVB (polyvinyl butyrate) was added as a binder, and 100 ml of ethanol was added as a dispersion medium, followed by ball mill kneading for 20 hours. Ball mill balls have a diameter of 1
A 0 mm Si ₃ N ₄ ball was used. The slurry obtained by ball mill kneading was placed in a stainless steel pad, air-dried in a fume hood, and then pressed at 30 MPa using a uniaxial press having a diameter of 60 mm to produce a compact.

[0023] Al ₂ O ₃ next molded body was lined with Al ₂ O ₃ powder
It was placed on a plate and sintered at 1000 ° C. for 2 hours in Ar gas of 0.2 MPa to obtain a sintered body.

Next, instead of 5 g of SiO ₂ powder, TiO ₂
Using 5 g of powder, 5 g of CaSiO ₃ powder, 5 g of ZnO powder, or 5 g of a mixed powder of 2.86 g of TiO ₂ and 2.14 g of SiO ₂ (molar ratio 1: 1), as in the case of the above-mentioned SiO ₂ powder A sintered body was produced.

The surface of each sintered body was covered with a metal Co layer having a thickness of 0.4 to 0.6 mm as in the case of the hot press of Example 1, but the inside was Co
O crystal particles and CaSiO ₃ crystal particles, CoO crystal particles and Co ₂ TiO ₄ crystal particles, CoO crystal particles and CaSiO ₃ crystal particles, CoO crystal particles and ZnO crystal particles, CoO crystal particles and Co ₂ SiO ₄ crystal particles and Co ₂ It was TiO ₄ crystal particles, and it was confirmed that the internal structure was dense and uniform. The relative density was 90-95%.

By removing the coating of the metal Co layer of these sintered bodies, the same sputter target as in Example 1 could be produced by normal pressure sintering. (Embodiment 3) FIG. 3 shows a sectional structure of an embodiment of a magnetic recording medium formed by using the sputter target of the present invention. For example, a 2.5 ″ glass substrate is used as the substrate 1. On this substrate, 475 g of the CoO powder of Example 1 and S
A seed layer was formed using a sputter target prepared using 25 g of iO ₂ powder. Transmission electron microscope image
From (TEM), the seed layer has a particle size distribution of 8 to 30 nm,
Average particle size 15 nm or less, standard deviation of particle size distribution 25%
The following CoO 2 crystal particles and 0.1 to 2 n around the particles
It consists of a m-thick amorphous part.

On top of this, Co-Cr having a thickness of 10 to 15 nm is formed.
A magnetic layer made of -Pt is formed, and the particle size of the magnetic layer reflects the particle size of the seed layer.
-30 nm, the average particle diameter is 15 nm or less, and the standard deviation of the particle diameter distribution is about 25%, so that a high recording density is achieved. A carbon protective film having a thickness of about 5 nm is formed on the magnetic film, and a magnetic recording medium is manufactured.

CoO: 95 wt%, and CoSiO ₄
And Co ₂ TiO _4: mixture of (1 1 molar ratio): If the target A produced in the same manner as in Example 2 using 5 wt%, an average particle diameter of CoO particles in the seed layer was 4 nm.
CoO: 95 wt%, and CoSiO ₄ and Co ₂ TiO
Example 2 using 5 wt% of a mixture with ₄ (1: 1 molar ratio)
Target A prepared in the same manner as above, amount of CoO: 60 wt
% And a mixture of CoSiO ₄ and Co ₂ TiO ₄ (1: 1 molar ratio): 40 wt%, the average particle diameter of the CoO particles in the seed layer is 10 wt.
nm. Co ₆₉ Cr ₁₉ P is deposited on these seed layers.
DC sputtering using a t ₁₂ (atomic%) target (sputtering conditions: discharge gas: pure Ar, gas pressure: 0.4 Pa,
Substrate temperature: about 200 ° C, DC power: 300W, time: 8
sec. ), A magnetic film having a thickness of about 10 nm was formed.

When the magnetic film was observed with a TEM, the magnetic particles had diameters of 4 nm and 10 nm, respectively.
The average particle diameter was almost the same. The standard deviation of the particle size distribution was 20% or less. In such a magnetic film, the unit of magnetization reversal is small, and a high recording density exceeding ²⁰ Gb / in ² is possible. (Example 4) The amount of CoO was set to 50 to 100 wt%,
₂ SiO ₄ amount, CaSiO ₃ amount, CoSiO ₄ + Co ₂ Ti
The O ₄ (1: 1 molar ratio) amount was changed to 50 to 0 wt%, and the diameter was 75 mm in the same manner as in the hot press of Example 1.
Was prepared. The obtained target was attached to an RF sputtering apparatus, and a film (seed layer) having a thickness of about 15 nm was formed on a 2.5 ″ diameter glass substrate. The sputtering conditions were discharge gas: pure Ar, gas pressure: 0.5 Pa. , Substrate temperature: about 200 ° C., high frequency power: 500 W, time: 10 se
c.

FIG. 4 shows the amount of CoO in each target and C in the film.
The relation with the average particle diameter of oO crystal particles is shown. The area of each of about 200 particles in the TEM observation photograph was determined, and the average particle diameter was determined by approximating the shape of the particles to a circle. As can be seen from the figure, the particle size of the CoO particles in the seed layer increases as the amount of CoO in the target increases. C in seed layer
The amount of CoO in the target corresponding to the preferred particle size of the oO crystal particles of 8 to 20 nm is about 70 to 98 wt%, and the standard deviation of the particle size distribution can be reduced to 20% or less.
The effect on the particle size by the type of oxide used as the target material is small. In addition, 90-98 wt% of CoO,
And a mixture of Co ₂ SiO ₄ and CoTiO ₄ for 10 to 2 w
At t%, the molar ratio of Co ₂ SiO ₄ to CoTiO ₄ in the range of 0.5 to 2.0 is suitable for obtaining fine and uniform CoO crystal particles.

[0031]

According to the sputter target of the present invention, the particle size of the CoO particles in the seed layer can be reduced and the particle size can be made uniform, and the size of the magnetic particles in the magnetic film can be reduced. Can be made uniform in particle size.

[Brief description of the drawings]

FIG. 1 is a diagram showing an X-ray analysis result of a sputter target.

FIG. 2 is a diagram showing the results of SEM observation of a sputter target.

FIG. 3 is a diagram showing a cross-sectional structure of a magnetic recording medium manufactured using a sputter target.

FIG. 4 is a view showing the relationship between the amount of CoO in a sputter target and the particle size of CoO particles in a seed layer.

[Explanation of symbols]

1. Glass substrate, 2. Seed layer, 3. Magnetic film, 4. Protective film.

Continued on the front page (72) Inventor Takashi Naito 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Yasutaka Suzuki 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Hitachi, Ltd.Hitachi Laboratory (72) Inventor Tetsuo Nakazawa 1-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Inside Hitachi, Ltd.Hitachi Laboratory (72) Inventor Hiroki Yamamoto 7-chome, Omikamachi, Hitachi City, Ibaraki Prefecture No. 1-1 Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Mitsutoshi Honda 1-1-1, Omika-cho, Hitachi City, Hitachi, Ibaraki Prefecture Inside Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Yuzo Kozono Hitachi, Ibaraki Prefecture 7-1-1, Omika-cho, Hitachi-shi, Ltd. Hitachi, Ltd., Hitachi Research Laboratory (72) Inventor Tatsumi Hirano 7-1-1, Omika-cho, Hitachi, Ibaraki, Japan F-term in Hitachi, Ltd. Hitachi Research Laboratory 4G048 AA03 AB01 AB05 AC08 AD02 AD03 AE05 4G073 BA11 BA20 BA 40 BA63 BD12 BD18 BD20 CC08 CD01 FD01 FD23 FD25 FD27 UB11 4K029 BA50 BC06 BD11 DC05 DC09 5D112 AA03 BD01 FA04 FB02

Claims (11)

[Claims] 1. A sputter target comprising CoO and a divalent / tetravalent oxide. 2. The method according to claim 1, wherein the CoO content is 60 to 98 wt%,
The sputter target according to claim 1, wherein the valence-4 valence oxide contains 40 to 2 wt%. 3. The divalent to tetravalent oxide is Co ₂ Si.
_2. The sputter target according to claim 1, wherein the target is O ₄ , Co ₂ TiO ₄ , Ca ₂ SiO ₃ or ZnO. 4. The method according to claim 1, wherein said CoO is 60-98 wt% and said C
o ₂ SiO ₄ and the above-mentioned Co ₂ TiO ₄ in total of ₄₀ to ₂
wt%, the Co ₂ SiO ₄ and the Co ₂ Ti
2. The sputter target according to claim 1, wherein the mixing ratio of O ₄ is in the range of 0.5 to 2.0 in molar ratio. 5. The sputter target according to claim 1, wherein the average particle diameter of the CoO crystal particles and the crystal particles of the divalent / tetravalent oxide is 2 to 10 μm. 6. A sputter target characterized in that a CoO powder and a divalent to tetravalent oxide powder are mixed, the mixed powder is pressed, and the pressed compact is sintered. Production method. 7. The divalent to tetravalent oxide is Co ₂ Si.
7. The method according to claim 6, wherein the sputtering target is O ₄ , Co ₂ TiO ₄ , Ca ₂ SiO ₃ or ZnO. 8. The method for manufacturing a sputter target according to claim 6, wherein the CoO powder is mixed with 60 to 98 wt% and the divalent / tetravalent oxide powder is mixed with 40 to 2 wt%. 9. The method according to claim 1, wherein said CoO powder is contained in an amount of 60 to 98 wt%.
iO ₂ and the combined powder of TiO ₂ were mixed and 40~2wt%, the mixing ratio of SiO ₂ and TiO ₂ powder is characterized in that in the range of from 0.5 molar ratio 2.0 claimed Item 6. The method for producing a sputter target according to item 6. 10. The method according to claim 10, wherein said CoO powder is 60 to 98 wt%.
The powders of SiO ₂ and TiO ₂ are combined in a total amount of 40 to ₂ % by weight, and pressed, and the pressed body is heated to a temperature of 800 to less than 10 ² Pa in a vacuum or a non-oxidizing gas atmosphere.
1400 ° C, pressure 0.1 ~ 10MPa, time 0.2 ~ 3.
The method for manufacturing a sputter target according to claim 6, wherein the sintering is performed for 0h. 11. The pressure-formed body is heated to a temperature of 900 to 1400 in a vacuum of 10 ² Pa or less or in a non-oxidizing gas atmosphere.
7. The method for producing a sputter target according to claim 6, wherein the sintering is performed at a temperature of 0.1 to 10 MPa for 0.1 to 3.0 hours.