JP5295537B2 - Manufacturing method of Ni-WB sputtering target material for manufacturing intermediate layer film in perpendicular magnetic recording medium - Google Patents

Abstract

Disclosed is an alloy for an Ni-W-B intermediate layer film which enables to obtain extremely good recording characteristics due to miniaturization of crystal grains when used as an intermediate layer of a perpendicular magnetic recording medium. Also disclosed is a sputtering target member for producing a thin film. This sputtering target member is composed of, in at%, 1-20% of W, 0.1-10% of B and the balance of Ni and unavoidable impurities. This sputtering target member can be produced by solidifying and molding a raw material powder, which is prepared by gas atomization and composed of, in at%, 1-20% of W, 0.1-10% of B and the balance of Ni and unavoidable impurities.

Description

The present invention relates to the production how the Ni-W-B-based sputtering target material used as the intermediate layer film in a perpendicular magnetic recording medium.

  In recent years, the progress of magnetic recording technology has been remarkable, and the recording density of magnetic recording media has been increased to increase the capacity of drives. However, in the magnetic recording medium of the in-plane magnetic recording system that is currently widely used in the world, when trying to achieve a high recording density, the recording bit becomes finer, and a high coercive force that cannot be recorded by the recording bit is required. . Therefore, as a means for solving these problems and improving the recording density, a perpendicular magnetic recording method has been studied.

This perpendicular magnetic recording system is formed so that the easy axis of magnetization is oriented perpendicularly to the medium surface in the magnetic film of the perpendicular magnetic recording medium, and is a method suitable for high recording density. In this perpendicular magnetic recording system, a multilayer recording medium having a magnetic recording film layer, a soft magnetic film layer, and an intermediate layer with improved recording sensitivity has been developed. A CoCrPt—SiO ₂ alloy is generally used for the magnetic recording film layer, and a Co—Zr—Nb alloy or the like is used for the soft magnetic film layer. The term “intermediate layer” as used herein refers to a nonmagnetic layer that is generally provided for the purpose of making crystal grains finer and providing anisotropy in crystal orientation of a magnetic recording film layer.

Various Ni-based alloys, Ta-based alloys, Pd-based alloys, Ru-based alloys, and the like have been proposed for the intermediate layer, and in recent years, Ni-W-based alloys have also been used. One of the roles of these intermediate layers is to control the structure of the magnetic recording film layer. To that end, it is important to make the crystal grains of the intermediate layer finer. For example, Fuji Times, Vol. 77, no. 2, 2004, page 121 (Non-Patent Document 1) entitled “Structure Control of Perpendicular Magnetic Recording Film”, medium characteristics strongly influence the crystal grain size and surface shape of the underlayer. receive. In the CoPtCr—SiO ₂ medium using Ru as the underlayer, an example is disclosed in which the grain size and magnetic separation structure of the magnetic crystal grains are controlled by controlling the Ru grain size and surface structure. In addition, it is considered that the Ni-W alloy is good when the lattice constant of the thin film is in the range of about 3.53 to 3.61 angstrom (× 10 ⁻¹⁰ m).
Fuji Times, Vol. 77, no. 2, 2004, p. 121

  However, when a perpendicular magnetic recording medium is manufactured as a Ni—W-based thin film intermediate layer, good recording characteristics can be obtained. However, in order to achieve a higher recording density, the Ni—W-based intermediate layer must be made finer. Necessary. However, there is no known knowledge of additive elements that contribute to the refinement of crystal grains in Ni—W thin films.

As a result of diligent development, the inventors have found that the addition of B to Ni-W can dramatically reduce the crystal grains of the thin film, leading to the invention. It is a thing. The gist of the invention is that
(1) At 1%, W: 1 to 20%, B: 0.1 to 10%, a raw material powder made of a sputtering target material made of the balance Ni and unavoidable impurities by the gas atomization method is 900 to 1150 ° C. A method for producing a Ni-WB sputtering target material for producing an intermediate layer film in a perpendicular magnetic recording medium, wherein the material is solidified at a temperature .

  As described above, when a perpendicular magnetic recording medium is manufactured using a Ni—W—B thin film added with B, which is an additive element that contributes to refinement of the crystal grain size of the Ni—W thin film according to the present invention, as an intermediate layer. Provided are an alloy for Ni—WB system interlayer film and a sputtering target material for producing a thin film, which can obtain extremely good recording characteristics.

Hereinafter, the present invention will be described in detail.
The reason why the component composition according to the present invention is limited to at% and W: 1 to 20% is that if less than 1%, the lattice constant of the sputtered thin film is less than 3.53 angstroms (× 10 ⁻¹⁰ m), If it exceeds 20%, the lattice constant exceeds 3.61 angstroms (× 10 ⁻¹⁰ m), so the range was made 1 to 20%. Preferably it is 5 to 15%.

  The reason for limiting to B: 0.1 to 10.0 at% is that if it is less than 0.1%, there is no effect of crystal grain refinement of the sputtered thin film, and if it exceeds 10.0%, the effect of crystal grain refinement is obtained. Since a large amount of Ni-based boride which is considered to be saturated and adversely affect the structure control of the magnetic recording film layer is generated, the range is set to 0.1 to 10.0%. Preferably it is 0.3 to 5%.

  The reason why the gas atomized powder is preferable as the raw material powder is that B is not dissolved in Ni at all by a melting method having a low cooling rate such as a casting method, and a coarse boride is crystallized. If this coarse boride is present in the sputtering target material, the sputtering causes abnormal discharge, resulting in problems such as generation of many particles. On the other hand, when the raw material powder is produced by the gas atomization method, a coarse boride does not crystallize because it is rapidly cooled and solidified, and the sputtering target material solidified and formed using this does not generate particles.

  The reason why 900 to 1150 ° C. is preferable as the solidification molding temperature is that the relative density of the sputtering target material becomes low in the solidification molding at less than 900 ° C., and the billet expands by molding at 1150 ° C. or less. However, when solidification molding was performed at a temperature exceeding 1150 ° C., the billet expanded during heating and stable production was difficult, so the range was set to 900 to 1150 ° C.

Hereinafter, the present invention will be specifically described with reference to examples.
The Ni-W-B alloy powder shown in Table 1 was produced by gas atomization, and this was used as the raw material powder, and the powder-filled billet deaerated and sealed in the SC can was solidified at 850 to 1200 ° C. by the HIP method and the upset method. It shape | molded and produced the sputtering target material of the Ni-WB system alloy by machining. For comparison, a sputtering target material of a Ni—WB alloy was produced by a casting method. Details of each step are as follows.

First, 25 kg of a molten base material was induction-melted in an argon crucible in argon, discharged from a hot water nozzle having a diameter of 5 mm at the bottom of the crucible at 1700 ° C., and powder was produced by Ar gas atomization with a spray pressure of 0.7 MPa. The produced Ni—W alloy powder was deaerated and sealed in an SC can having an outer diameter of 205 mm, an inner diameter of 190 mm, and a length of 300 mm. The degree of vacuum at the time of deaeration was about 1.3 × 10 ⁻² Pa (about 1 × 10 ⁻⁴ Torr).

  The above powder-filled billet was HIP (hot isostatic press) molded at 850 to 1200 ° C. and 147 MPa. Moreover, in the case of upset, after heating said powder filling billet to 1000-1100 degreeC, it inserted in the restraint type | mold container of diameter 215mm, and shape | molded with the pressure of 500 MPa. The solidified molded body produced by the above method was processed into a diameter of 76.2 mm and a thickness of 3 mm by wire cutting, lathe processing, and planar polishing, and a copper backing plate was brazed to obtain a sputtering target material.

  On the other hand, as a casting method, 100 kg of melted base material is vacuum-melted, cast into a refractory having a diameter of 200 mm, and then machined to a diameter of 200 mm and a length of 100 mm with a lathe and hot forged up to a height of 50 mm at 1100 ° C. did. The subsequent sputtering target material was produced by the same method as the above HIP and upset material.

With respect to the expansion of the billet at the time of solidification molding, which is an evaluation item shown in Table 1, the HIP material was evaluated by the appearance of the billet after HIP. Moreover, about the upset material, it evaluated by the external appearance at the time of billet heating. As a result, the evaluation was made with no expansion: ○ and with expansion: x.
The relative density of the sputtering target material is measured by the volume-weight method from a disk having a diameter of 76.2 mm and a thickness of 3 mm produced by the above method, and the ratio with the calculated density calculated from the composition is the relative density. It was.

  As for the number of particles of the sputtered film, the produced sputtering target material was sputtered onto a Si substrate having a diameter of 376.2 mm. The sputtering conditions were Ar pressure: 0.5 Pa, DC power: 500 W, and film thickness: 500 nm. The number of particles generated at this time was measured. The number of particles in Table 1 is No. 1 sample was expressed as a relative value.

  Further, the lattice constant of the sputtered film and the Ni boride were obtained by X-ray diffracting the sputtered film and calculating the lattice constant from the diffraction peak. In addition, the formation of Ni-based borides was also confirmed. No Ni-based boride: ◯, small amount produced: Δ, large amount produced: x. Furthermore, the crystal grain size of the sputtered film was obtained by observing the cross section of the sputtered film with a TEM and by analyzing the image, the diameter of the equivalent area circle was determined as the crystal grain size. The crystal grain size in Table 1 is No. The crystal grain size of 1 is expressed as a relative value with respect to 100, and the smaller the numerical value, the finer the crystal grain size.

表１に示すように、Ｎｏ．１〜９は本発明例であり、Ｎｏ．１０〜１７は比較例である。

As shown in Table 1, no. 1 to 9 are examples of the present invention. 10 to 17 are comparative examples.

  Comparative Example No. Since 10 does not contain W as an alloy component, the lattice constant is small. Comparative Example No. No. 11 has a high lattice constant because of its high W content as an alloy component. Comparative Example No. No. 12 does not contain B as an alloy component, so the relative density is large and the crystal grain size is large. Comparative Example No. No. 13 has a low relative density and a large crystal grain size due to the low content of B as an alloy component. Comparative Example No. No. 14 had a high content of B as an alloy component, so the number of particles was large and a large amount of Ni-based boride was generated.

  Comparative Example No. 15 has a large number of particles because of the casting method. Comparative Example No. No. 16 has a large number of particles because the solidification molding temperature is low. Comparative Example No. Since No. 17 had a high solidification molding temperature, the billet after HIP was expanded, and it was difficult to process the sputtering target material. On the other hand, No. which is an example of the present invention. Since 1-9 satisfy | fill the conditions of this invention, it turns out that it is excellent in the characteristic as a sputtering target material for thin film manufacture.

As described above, in the Ni—W—B-based intermediate sputtering target material used as the intermediate layer film in the perpendicular magnetic recording medium, by adding B to the Ni—W-based alloy, the crystal grains of the thin film are dramatically reduced. This makes it possible to provide a stable and high-density Ni—W—B-based interlayer film alloy and a sputtering target material for manufacturing a thin film without the expansion of billets.


Patent Applicant Sanyo Special Steel Co., Ltd.
Attorney: Attorney Shiina

Claims (1)

The raw material powder which produced the sputtering target material which consists of remainder Ni and an unavoidable impurity by gas atomizing method is solidified at the temperature of 900-1150 degreeC including W: 1-20% and B: 0.1-10% by at%. A method for producing a Ni-WB sputtering target material for producing an intermediate layer film in a perpendicular magnetic recording medium, wherein the perpendicular magnetic recording medium is molded.