JPS62256962A - Sputtering target material for forming magneto-optical recording media - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention is directed to the production of thin films mainly composed of rare earth elements and iron group elements, which have recently been attracting attention as magneto-optical recording materials, by slicing. This relates to the target material used in this process.

[Conventional technology]

Magneto-optical recording media, which are mainly composed of rare earth elements and iron group elements, to which are added elements such as Ti to improve corrosion resistance, are currently attracting attention as rewritable, high-density dual-purpose media. As a target material or target used when manufacturing such a recording medium by sputtering, (1) a predetermined proportion of rare earth metals, iron group metals, and additive elements are already mixed in vacuum or in an inert gas atmosphere. (2) An alloy target material prepared by cutting, grinding, etc. an alloy ingot that has been completely solidified by arc melting, and (2) placing a rare earth metal chip and an additive element chip on an iron group metal plate; A composite target combining three types of tarded materials has been proposed by placing iron group metal chips and additive metal chips on a metal plate.

[Problem that the invention seeks to solve]

However, in the alloy target material of (1), 1
) Since the dimensions of the target obtained from it depend on the size of the melting furnace, a large diameter target cannot be obtained; 11) Because the oxygen content in the target material is as high as 0.5 to 3.0% by weight. 11) The strut ring film obtained from this alloy target material is difficult to form a perpendicularly magnetized film required for magneto-optical recording, and is prone to cracking due to its low toughness (less than 2 bends/mm'). 1) It has poor thermal shock resistance, so it often cracks due to thermal shock during sputtering, and V) In general, the proportion of rare earth elements in the film obtained by sputtering the alloy target material is It changes significantly from just above the target center to the periphery and is not uniform, especially when a relatively small amount of an additive element such as Ti is mixed in the alloy target material. As a result of segregation without being uniformly distributed in the sputtering film, the composition of the additive elements becomes uneven in the sputtered film.In addition, with the composite target of (2) above, 1) it cannot be rotated or reversed, and the chips cannot be distributed uniformly. In addition, the rare earth metals, iron group metals, and additive elements are originally distributed in large clumps, and the rate at which these rare earth metals, iron group metals, and additive elements stagnate is extremely low. Because of the difference in the distribution of each component on the sputtered film, abnormal discharge is likely to occur between the plate and the chip. It becomes easier for the magnetic field to enter the surface of the plate, but it is difficult for the magnetic field to reach the surface of the plate, and as a result, the magnetic field becomes uneven.
There were problems in that sputtering efficiency decreased and the target was more likely to be partially consumed.

[Findings based on research]

Therefore, the present inventors conducted various studies to solve the above-mentioned problems regarding sputtering target materials or targets for forming magneto-optical recording media, and as a result, (11Tb, Cd, Dy, Ho, Tr)
One or more rare earth elements selected from the group consisting of n and Er, 1:15-35, Ti: 0.01-5 Ti, iron group element selected from the group consisting of Fe, Co and Ni 1 A composition (at least atomic %) consisting of two or more types of seeds and unavoidable impurities: the remainder, and single metal particles and alloy particles consisting of one or more of the rare earth elements, iron group elements, and titanium. In a target material, two or more types of particles are combined by sintering and have a fine mixed structure in which a reaction-diffusion phase generated by a reaction between the particles is present at the interface of these particles. The amount of oxygen contained as an unavoidable impurity in the target material is significantly reduced to less than 0.3% by weight compared to conventional alloy target materials, and as a result, the amount of oxygen contained in the target material
(2) The target material should contain Ti alone and T.
One or both of the i-alloys are mixed among other particles in the form of fine particles, and a reaction-diffusion phase containing residual Ti other than Ti is present between the interfaces of each particle. Since Ti intervenes to further average the distribution of Ti, the segregation of Ti is suppressed, and as a result, even if the amount of Ti added in the target material is small as mentioned above, it is uniformly distributed in the target material. (3) In the target material, the proportion of the reaction-diffusion phase, that is, the proportion of Ti in any cross section or surface, (4) The ratio of the area of the reaction-diffusion phase to the entire sputtered film determines the uniformity of the film composition over the entire sputtered film; (4) The ratio of the area of the reaction-diffusion phase to the entire sputtered film (5) In the target material, the reaction diffusion phase is It has been found that when the area ratio falls within the above range, the target material has relatively high toughness and thermal shock resistance and becomes difficult to crack.

[Means for solving problems]

This invention was invented based on the above-mentioned knowledge, and titanium added to improve corrosion resistance is uniformly dispersed in iron group elements together with rare earth elements, and rare earth elements used as magneto-optical recording media. When producing a thin film made of iron group elements and titanium, the aim is to provide a target material that can produce the recording medium having a uniform composition over a wide area, and a thin film made of Tb, Gd, Dy, Ho, Tm and Er. One type of rare earth element selected from the group, or two or more types =
15-35%, Ti: 0.01-5%, one or more iron group elements selected from the group consisting of Fe, Co and Ni, and unavoidable impurities: the remainder (atomic %), And two or more particles selected from the single metal particles and alloy particles made of any one or more of the rare earth elements, iron group elements, and titanium are combined by sintering, and at the interface of these particles, It has a fine mixed structure in which a reaction-diffusion phase generated by a reaction between the particles exists, and furthermore, the proportion of the area occupied by the reaction-diffusion phase in any cross section or surface is the area of the entire cross section or surface. 15~
The present invention relates to a base stumbling target material for forming a magneto-optical recording medium, which is characterized by having a diameter of 50 mm.

[Detailed description of the invention]

Hereinafter, the configuration and incidental matters of the present invention will be specifically explained.

1. Composition Tbr which is one of the main components constituting the target material
The content of rare earth elements consisting of one or more of Gd, Dyl Ho, 'I'm and Er is 15
at, less than % (atom) or 35 at
, %, the target material will no longer produce a film with magnetic properties suitable for use as a magneto-optical recording medium. Therefore, in the present invention, the amount of rare earth elements contained in the target material is set to 15 to 35%. It is defined as at,%.

The content of Ti added in the cut material is 0.01 at,
If it is less than 5 at.%, the desired effect of improving corrosion resistance cannot be obtained, while if it exceeds 5 at.%, the Kerr rotation angle as a magneto-optic effect is small in the sputtered film, and the necessary magneto-optical properties cannot be obtained. Therefore, the content of Ti was determined to be 0.01 to 5 at.%.

The target material of the present invention contains rare earth elements and Ti within the above range, and the residue is composed of iron group elements and unavoidable impurities. Impurities that were unavoidably accompanied, such as Si+ AA' + Cat C+ P
It is permissible for t S + Ta, Mn, O, etc. to be added in small amounts within a range that does not adversely affect the properties of the target material.

2. Structure The target material of the present invention consists essentially of single metal particles consisting of any one of rare earth elements, iron group elements, and titanium, such as Tb, Co, and Ti metal particles, and these metals. Alloy mackerel, 7
Two or more types of alloy particles are bonded together by sintering, and these particles are present at the interface of these particles. A reaction-diffusion phase generated by a reaction between particles is present, and a fine mixed structure in which this reaction-diffusion phase and the various particles are uniformly mixed is formed.

3. Area ratio of reaction-diffusion phase Target materials consisting of rare earth elements, iron group elements, and titanium, and in which the reaction-diffusion phase is present in various area ratios in any cross section or surface, are each sputtered. Various thin films to be used as magneto-optical recording media are deposited on a substrate, and the rare earth element and Tl contents of these thin films are examined at several locations from just above the tarded center to just above the outer periphery of the target. When the relationship between the area ratio of the reaction-diffusion phase in the cross section or surface of this type of target material and the content of rare earth elements and Ti in the radial direction of the thin film was determined by experiment, it was found that if the area ratio is small, , the rare earth element content in the thin film is highest right above the center of the target, and decreases toward the edges.
The Ti content decreases near the center of the target and increases at the edges, but when this area ratio reaches a factor of 15, both the rare earth element and Ti become uniformly distributed over almost the entire surface of the thin film. Therefore, the area ratio is 5.
When the area ratio is maintained at 0% and further exceeds 50%, the rare earth element content is small at the center of the target surface and increases as it approaches the edges, and the Ti content is
It has been found that the amount increases in the middle and directly above the target, and decreases at the edges. Therefore, in the present invention, the proportion of the area of the reaction-diffusion phase in any cross section or surface of the target material is determined by 1 of the entire surface area
It was set at 5-50%.

Furthermore, when the area ratio of the reaction-diffusion phase is within the above range, the target material of the present invention has high toughness and thermal shock resistance because it contains an appropriate amount of intermetallic compounds that constitute the reaction-diffusion phase. However, this also has the advantage of preventing damage during handling or processing and the occurrence of cracks due to thermal shock during slugging.

4. Method for manufacturing target material The target material as described above is manufactured, for example, through a series of steps as described below.

a) First of all, finely divided, e.g. powder, pellets or flakes Tb, Gd, Dy, Ho
, an elemental metal consisting of one type of Trn and pr, and an alloy consisting of two or more of the same, an elemental metal consisting of one of Fe, Co and Ni, and an alloy consisting of two or more of the same, Ti, Alternatively, prepare an alloy consisting of a combination of two or more of the above-mentioned rare earth metals, iron group metals, and Ti, and mix these in a predetermined ratio in an inert atmosphere, for example, in a ball mill. Rare earth elements = 15-35%, Ti
: 0.01 to 5, and iron group element Jufucho impurities:
b) forming a mixture having a composition (atomic ratio) consisting of the residue υ;
．． In a vacuum of 0.01 to 10 -6 Torr or in an inert gas atmosphere such as argon gas, the temperature below the liquid phase manifestation of the metal component system present in the mixture, i.e. the eutectic point of the metal component system, is also maintained, for example. By performing hot open forming by hot pack rolling, hot pressing, hot isostatic pressing (HIP), hot forging, etc. at a low temperature of 300 to 50'C,
Plastic deformation of each particle in the mixture, partial solid-state diffusion between each particle, and consequent formation of a reaction-diffusion phase at the particle interface and bonding of the particles results in a high density, i.e. C) forming a dense and strong molded body generally having a relative density of 95 to 100%; C) then, also in vacuum or in an inert gas atmosphere, the liquid phase development temperature of the component system present in the molded body; Each particle interface in the molded body is heat-treated by heating the molded body for a long time (for example, several tens of hours) at a temperature below, for example, just below the eutectic point of the component system or even 200°C lower. By generating and growing a reaction-diffusion phase consisting of an intermetallic compound, and adjusting the temperature and time of this heat treatment appropriately, the area ratio of the reaction-diffusion phase in any cross section or surface became a predetermined value. Target material is obtained.

[Examples and effects based on the examples]

Next, the present invention will be explained using examples and in comparison with comparative examples and conventional examples.

Example a) A Tb powder with a purity of 99.8 and an average particle size of 100 μm, a Fe74 CO26 (by weight) alloy powder with a purity of 99.9 and a purity of 100 μm, and a Tb powder with a purity of 99.9 and a purity of 80 μm.
Purity: 99.8% Fe94,56
Tie, 44 (weight) alloy powder, Tb:Fe7
4-CO24” Fe94,56-Ti5.44 blending ratio is 41.50:11.80:46.67 (wt%)
A predetermined amount was weighed and mixed using a ball mill in an argon gas atmosphere for 2 hours to obtain a total weight of 270y.
A mixed powder was prepared.

b) Then, in the center of a stainless steel can with a wall thickness of 1,218 mm and a disc-shaped space with a diameter of 120 g and a thickness of 4.0 IEI inside, an outer diameter of 12.7 m and a length of 5 mm is placed.
QQglX thickness: 1. After vertically attaching a stainless steel tube of 0.0 m and filling the mixed powder into the disc-shaped space, the interior of the stainless steel can is evacuated to obtain a vacuum level of l.
After evacuation to X IQ Torr, the base of the stainless steel can was heated and pressed with a gas burner to seal the mixed powder inside the stainless steel can. The mixed powder thus vacuum-seced in a stainless steel can is then rolled into a regular rolling mill at a temperature of 600°C and a rolling reduction rate of 600°C.
At 10%, hot and deep rolling was performed until the total thickness of the can was compressed to about 4.5 M to form a rolled molded body inside the can.

C) The heptagonal body thus confined in the can is charged into a heat treatment furnace, and heated from room temperature at a heating rate of 700°C/hr under a high vacuum of pressure crab I x 10-5 Torr or less. Heat treatment is performed by heating to 650°C and maintaining this temperature for 50 hours, then cooling to room temperature, removing the outer stainless steel can on a lathe, and removing Tb1 from the inside.
A target material having a composition of 9,9Fe72,09CO3,97Tt4,04 (atomic %) was taken out.

When the structure of the target material obtained in this way was observed using a microscope, it was found that the target material had a micrograph (400x magnification) in Figure 1 and a schematic diagram to make the metal structure easier to see. The first explanatory diagram
As shown in figure a, some Tb (white part) and Fe-Co alloy (black part) remain with the composition of the raw material powder.
and l;'e -'l'i alloy (black part),
Tb5gF produced by diffusion reaction between raw material powders
'e3Sco14Til I 'rb5□Fe41)T
17.

A fine mixed structure in which intermetallic compounds (gray areas) such as Fe, oC06Ti4, and Tb98CO2 were uniformly distributed was formed, and the area ratio of this diffusion reaction phase was 20%.

Next, in order to evaluate the performance of this target material, it was processed into a disc-shaped target with a diameter of 127 m x a thickness of 21 CI, and based on this, the argon partial pressure:
After applying grease batter for 1 hour at 5 x 10-2 Torr, bias voltage: 0■, Sunogutatsuta Electric Crab 20
As shown in Figure 2, 11 glass slides were placed at a constant 0W and spaced 70 mm apart from the sputtering surface of the target, and arranged in a straight line at 208 mm intervals in the radial direction from just above the center of the target. was used as a substrate, and a film was attached to the surface of this substrate by magnetron sputtering.

T in the film on each slide glass produced in this way
The amount of i and the amount of Tb (at, shown in %) are determined by analysis,
FIG. 3 shows the changes in the Ti and Tb amounts along the diameter direction passing directly above the target center.

Next, in order to evaluate the corrosion resistance of the above films, these films were stored in a constant temperature and humidity chamber maintained at a temperature of 40 °C and a relative humidity of 280 °C for a long period of time. When a corrosion resistance test was conducted to observe changes in the film, there was no change in the film even after 10 days.For comparison, a film produced by the same method as above except that no Ti was added Tb2□Fe74Co4(,
When the same corrosion resistance test as above was carried out on a sputtered film formed by the same method as above from a target material having a composition of Ta.

Conventional Example 1 A mixed powder obtained by mixing the same raw material powder as the raw material powder used in the example in the same proportion as the example, that is, a mixed powder similar to the mixed powder prepared in the example, was completely melted in an arc melting furnace. An alloy target material having the same composition as the target material in the example was manufactured by melting and mixing with the target material, and after processing this into a target of a predetermined size, a sputtering experiment similar to that in the previous example was conducted using this target material. carried out,
The change in Ti content in the film thus obtained is shown in FIG. 4 in comparison with the change in Ti content in the film obtained in the above example.

Conventional example 2 Fe75 with dimensions of diameter: 127mm x thickness: 21B
- On a CO25 (atomic ratio) alloy plate, a total of 12 Ti chips having dimensions of 3 hexagons x thickness: 2 gm are arranged 409 apart in the diameter direction, and 5 gm square x thickness =
By uniformly arranging 100 Tb chips having dimensions of 21u&, a composite target having the same composition as the target material in the previous example was prepared, and using this composite target, the same method as above was prepared. Figure 4 shows the change in the Ti content in the film obtained by carrying out the Nasu-stuttering experiment.

As is clear from the results shown in FIG. 4, the target material of the example provides a film in which the Ti content is extremely uniformly distributed over a wide range, as described above, whereas the conventional example For target materials 1 and 2, Ti
It can be seen that films with significantly varying contents are produced.

Comparative Example 1 The target material and the target material of the example were treated in the same manner as in the example except that the heat treatment was held at 650°C for 3 hours and the area ratio of the reaction diffusion phase was 10.3%. A target material with the same composition was manufactured, and the target obtained by processing this target material was subjected to the same starch ringing experiment as described above, and the changes in the concentration of Ti and Tb in the resulting film were measured in the fifth experiment. Shown in the figure.

Comparative Example 2 In the heat treatment, the target material of the previous example and the target material of the previous example were used, except that the heat treatment was held at 650°C for 110 hours and the area ratio of the reaction diffusion phase was set to 61.7%. A sputtering experiment similar to that described above was carried out on a target obtained by manufacturing a target material having the same composition and processing this target material, and the changes in the concentrations of Ti and Tb in the resulting film were measured in the 6th experiment. Shown in the figure.

As is clear from the results shown in FIGS. 5 and 6, when the area ratio of the reaction-diffusion phase in the target material is out of the range of the present invention, Ti and T
It can be seen that the distribution of b tends to be non-uniform in all cases, and as a result, a film having a stable composition within a wide range cannot be obtained.

[Overall effect of the invention]

As is clear from the above description, according to the present invention, it is possible to form a magneto-optical recording medium that has a uniform composition over a wide area and also has excellent corrosion resistance.
It is possible to provide a highly strong snowcutter target material.

[Brief explanation of drawings]

Fig. 1 is a microscopic photograph showing the metallographic structure of the target material of the present invention, a is a schematic explanatory drawing for making the metallographic structure shown in Fig. 1 easier to understand, and Fig. 2 Figures 3 to 6 show the arrangement of the 11 substrates relative to the target adopted in the S-Guttering experiments of the Example, Conventional Example, and Comparative Example, and Figs. It is a graph showing a change in Ti or Tbm content in a vine film.

Claims (1)

[Claims] One or more rare earth elements selected from the group consisting of Tb, Gd, Dy, Ho, Tm and Er: 15-3
5%, Ti: 0.01 to 5%, one or more iron group elements selected from the group consisting of Fe, Co and Ni, and unavoidable impurities: the remainder (atomic %), and the above Two or more types of particles selected from single metal particles and alloy particles made of one or more of rare earth elements, iron group elements, and titanium are combined by sintering, and a bond between the particles is formed at the interface of these particles. It has a fine mixed structure in which a reaction-diffusion phase generated by the reaction of 15~
50% sputtering target material for forming a magneto-optical recording medium.