JPH0242899B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a target used for producing a thin film of a ferromagnetic compound having a large magneto-optical effect, and a method for producing the target.

[Conventional technology] In recent years, the importance of optical technology has been increasing to improve the performance, density, and reliability of information processing, storage, and transmission.As part of the development of optical technology, new magneto-optical materials are being developed. Research and development is underway. Magneto-optical materials are used in magneto-optical elements and photothermal magnetic recording media, and in the former, as well as improving performance,
It is important to develop thin film formation methods that are compatible with integration technology in order to incorporate them into optical integrated circuits.

In optical integrated circuits, return light is generated due to reflection at end faces of optical components and curved portions of optical paths. The returned light makes the oscillation of the laser, which is the light source, unstable. Optical isolators, which use magneto-optic effects to pass light in only one direction, are important optical circuit components that cut out returning light. Furthermore, circulators that separate input and output light, optical switches that switch optical circuits, and optical deflectors that sweep the direction of light within a certain angle range can be realized using the magneto-optic effect.

In order to reduce the element length, magneto-optic materials have large magneto-optic effects such as Faraday rotation (θ _F ; units are degrees/cm) in the wavelength band of the light used, and optical absorption is important in terms of insertion loss. It is important that the coefficient (α; unit: 1/cm) is small. The magneto-optical figure of merit is defined by the Faraday rotation angle per unit absorption (θ _F /α; units are degrees).

Currently, the only material in practical use is the rare earth iron garnet (R ₃ Fe ₅ O ₁₂ ; R represents a rare earth metal element and yttrium). Among currently known materials, YIG (Y ₃ Fe ₅ O ₁₂ ) is a material that has a high magneto-optical figure of merit at room temperature and satisfies the requirements of being optically isotropic. It is iron garnet. θ _F at a wavelength of 633 nm for YIG is +835 degrees/cm, α is 700 1/cm, and the magneto-optical figure of merit is 1.2 degrees. To create a device, the plane of polarization only needs to be rotated by 45 degrees, so the required optical path length is
It is approximately 500 μm. However, in order to treat it as a component of an optical integrated circuit, it is necessary to shorten the optical path length by about two orders of magnitude. To achieve this, it is necessary to develop a material with θ _F that is about two orders of magnitude larger. Crystals in which R in R ₃ Fe ₅ O ₁₂ is replaced with Bi are attracting attention as materials with high θ _F .

Ion beam sputter deposition (IBS), a method for producing thin films, is an inherently non-thermal equilibrium process. Sputtered particles have an energy distribution peak around several eV. This energy is suitable for deposition and little etching occurs. When converted into thermal energy, this energy corresponds to energy at tens of thousands of degrees, and promotes surface diffusion and crystallization reactions of deposited particles. As a result, it is expected that the density, smoothness and adhesion of the film will be improved and the crystallization temperature will be lowered.

The IBS method is a method in which an ion beam of an inert gas such as Ar or _N2 is irradiated onto a target containing the constituent elements of the substance to be deposited on the substrate, and the substance sputtered from the target is deposited on the substrate. . To form an oxide film, oxygen is supplied as an atmospheric gas or ions and reacts with the deposit.

The composition of a film deposited by the IBS method is determined by the sputtering yield of film composition atoms and their adhesion rate to the substrate. Both sputtering yield and deposition rate depend on the type of atoms.

Generally, the deposited film and the target have different composition ratios. In order to obtain a film with a desired composition ratio and homogeneity in thickness and composition, the composition ratio of the sputtered particle beam must be optimized and the composition ratio and intensity adjusted spatially and temporally. It has to be equalized. IBS is performed in a high vacuum of 10 ^-5 Torr, so if the distance between the target and the substrate is about 10 to 20 cm, homogenization due to collisions between atoms within the beam cannot be expected. Therefore, the above conditions require that homogenization of the beam at the point of sputtering is necessary.

[Problems to be Solved by the Invention] In order to obtain such a beam, it is necessary to optimize the composition ratio of the target and to microscopically homogenize the composition and structure of the target. However, there is a problem in that such a target is difficult to achieve by mixing or alloying single constituent metal elements.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a sputtering target and a method for manufacturing the same that can be used to manufacture thin films of ferromagnetic compounds with a large magneto-optical effect.

[Means for solving the problems] In order to achieve such an object, the present invention has the following features:
A target for producing a Bi ₃ Fe 5 O ₁₂ thin film characterized by using a mixed powder of Bi oxide and Fe oxide as a raw material, and a target for producing a Bi 3 Fe ₅ O 12 thin film, which is characterized by using a mixed powder of Bi oxide and Fe oxide, respectively.
Bi ₂ O ₃ and α-Fe ₂ O ₃ with a molar ratio of 3:
5-3.5:4.5.

[Function] In the present invention, fine powders of Bi oxide and Fe oxide, which are the constituent metal elements of the target thin film, are mixed at a molar ratio of 3:5 to 3.5:4.5, so that the composition and structure are fine. A visually homogenized target for sputtering can be obtained.

[Example] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a flowchart of the target manufacturing process. The target is obtained by sintering a fine powder mixture of metal element oxides of the desired thin film composition at a low temperature. The manufacturing process of the target used to manufacture the Bi ₃ Fe ₅ O ₁₂ thin film is described in the first step.
This will be explained along the diagram.

Bi ₂ O ₃ and α-Fe ₂ O ₃ powder with a purity of 99.999%
The molar ratio of Bi ₂ O ₃ and α-Fe ₂ O ₃ is 3:5 to 3.5:4.5
Weigh each and mix them.

The mixture is compression molded into a disk shape at a pressure of 600 kg/cm ² or more.

The compression molded product is fired at a temperature of 800 to 840° C. for 6 hours in the atmosphere at normal pressure.

This fired product is crushed to a fine powder as much as possible.

Repeat steps and.

The sintered body obtained in the process is processed into parallel flat plates and bonded to a 99.99% pure oxygen-free copper plate using silver paste.

In the process, if Bi ₂ O ₃ and α-Fe ₂ O ₃ are weighed so that the total weight is 40 to 50 g, a target with a diameter of 50 mm and a thickness of 4 mm can be produced.

This process is intended to refine and homogenize the ceramic structure.

This process is essential as a heat dissipation measure to prevent the energy supplied to the target by ion irradiation from converting into heat and increasing the target temperature.

The reason why the firing temperature was chosen to be 800 to 840°C is that a sintered body with the highest possible density and homogeneous microstructure can be obtained within this temperature range. Above this temperature, coarse grains of compounds of Bi ₂ O ₃ and Fe ₂ O ₃ in various ratios grow, making spatial homogenization difficult. Further, at a temperature lower than this temperature, sintering does not proceed, and therefore only a low-density sintered body can be obtained.

The composition range of the target in which a garnet layer can be obtained in the deposited film when manufacturing a thin film using the IBS method is as follows:
Bi ₂ O ₃ /Fe ₂ O ₃ (mole unit) was 3/5 to 3.5/4.5. In addition, in this example, Bi ₂ O ₃ and α-
Although Fe ₂ O ₃ was used, the present invention is not limited to this as long as a predetermined Bi/Fe ratio can be achieved.

[Effects of the Invention] As explained above, in the present invention, the compositional metal elements of the target thin film are Bi oxide and Fe.
By mixing fine oxide powders at a molar ratio of 3:5 to 3.5, a sputtering target whose composition and structure are microscopically homogenized can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a flowchart of the target manufacturing process.

Claims (1)

[Claims] 1. In a target for producing a Bi ₃ Fe ₅ O ₁₂ thin film formed by sintering a mixed powder of Bi oxide and Fe oxide, the powder of Bi oxide and Fe oxide is Bi ₂ O ₃ and α-Fe ₂ O ₃ with a molar ratio of 3:5 to 3.5:
4.5 Bi ₃ Fe ₅ O ₁₂ thin film production target. 2 In a method for producing a target for producing a Bi ₃ Fe ₅ O ₁₂ thin film, which is obtained by sintering a mixed powder of Bi oxide and Fe oxide, the mixed powder of Bi oxide and Fe oxide is sintered at 800 to 840°C. oxide, Bi oxide and
The Fe oxide is characterized by being Bi ₂ O ₃ and α-Fe ₂ O ₃ and having a molar ratio of 3:5 to 3.5:4.5.
A method for producing a target for producing a Bi ₃ Fe ₅ O ₁₂ thin film.