JPH0471754A - Target casting mold for sputtering - 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 [Industrial Application Field] The present invention relates to a casting mold for a casting target for sputtering for forming a thin film.

[Prior Art] In recent years, rare earth transition metals have been mainly used as magneto-optical recording media. These recording media are formed into thin films by a sputtering method, and a sputtering target is used as the raw material.

Methods for producing sputtering targets can be broadly classified into casting methods and sintering methods, and cast targets are attracting attention because of their low oxygen concentration and low cost.

When rare earth transition metals used in magneto-optical recording media are melted and cast, they form extremely brittle eutectic alloys.

Therefore, for casting targets, for example, JP-A-62-29
7464 and JP-A No. 01-11968, it has conventionally been manufactured by casting a molten metal of a rare earth transition metal in a preheated mold in an inert atmosphere.

[Problems to be Solved by the Invention] However, targets cast using conventional molds do not have large racks, but many microscopic cracks with a length of 1 to 2 cm and a width of about 0° to 1 mm are observed.

If there are many racks like this, the target will be thickened during sputtering, causing abnormal discharge, or the racks will be filled with impurities during processing, causing impurities to be mixed into the film.

Therefore, the present invention aims to solve these problems.
The purpose is to provide a good target with few microcracks.

[Means for Solving the Problems] Therefore, the sputtering target casting mold of the present invention has the following features: (1) In the casting preparation mold for a sputtering casting target whose main composition is a rare earth transition metal, the mold has two parts.
(2) The melting point of at least one of the metals used in the mold is below the melting point of pouring and above the temperature of the mold at the time of installation. It is characterized by

[Effect] As a result of various experiments, we have found that there is a close relationship between the probability of crack appearance during casting of rare earth transition metal alloys and the cooling curve of the cast ingot. In particular, it was found that slow cooling near the crystallization temperature of the eutectic metal is effective in eliminating microcracks.

When the mold of the present invention is used, a portion of the metal in the mold is melted by preheating the mold or by the heat of the molten metal. After pouring the metal, the mold cools down together with the ingot. When the temperature of the mold reaches a certain temperature, the metal in the mold solidifies and generates latent heat. This latent heat slows down the cooling rate of the mold and the flange block.

Therefore, by appropriately selecting the mold metal material and appropriately setting its melting point, it is possible to slow down the cooling rate in a certain temperature range of the cooling curve of the mold. In other words, the latent heat of the mold can be used to slow down the cooling rate in a certain temperature range near the crystallization temperature of the eutectic metal.

As a result, microcracks in the cast ingot are reduced.

[Example] The present invention will be explained below based on Examples.

As an example, a TbFeCo alloy is cast and used as a sputtering target. First, the raw materials are Tb, Fe, and Co.
The atomic ratio of each pure metal is 23% Tb and 6% Fe.
Prepare 7% and 10% Co.

Next, prepare the mold. The mold has a shape for casting a disc-shaped target, and its cross-sectional view is shown in Fig. 1. 101 is a casting sprue, 102 is an upper part of the mold made of refractory bricks, 104.1
05.106 forms the lower part of the mold, and the molten metal is poured into the space surrounded by 102.104 and cooled. 104 and 106 are made of iron, and 105 is a Pr (praseodymium) plate. The lower mold 106 is tightly fitted to prevent 105 from flowing out when the temperature exceeds its melting point and to maintain sufficient thermal contact with 105 and 106.

Next, the raw materials are melted in a vacuum melting furnace and poured into the preheated mold. The temperature was 1600°C.

After casting, TbF is heated due to the latent heat effect of Pr incorporated in the mold.
The cooling rate became slow near 1200°C, which is near the crystallization temperature of the eCo alloy.

After casting and cooling, the ingot was ground into a circular target with a diameter of 4 inches, and when visually inspected, no fine cracks were observed.

[Comparative Example] In order to confirm the effects of this example, a comparative example was conducted using a casting method using a conventional mold.

The raw materials are the same as in the above example. A cross-sectional view of a conventional mold is shown in FIG. 201 is hot water 0.202 is the upper part of the firebrick mold, 204 is the lower part of the iron mold, 203 is 201.2
A space surrounded by 04 into which molten metal is poured.

Next, the raw materials are melted in a vacuum melting furnace and poured into the preheated mold. The temperature was 1600°C.

When the melting temperature was measured after pouring, the cooling rate was not as slow as in the above example even at around 1200° C., which is near the crystallization temperature of the TbFeC0 alloy.

After casting and cooling, the ingot was ground into a circular target with a diameter of 4 inches, and when visually confirmed, 20 fine cracks were observed.

In the above embodiment, the composition of the target is TbFeCo.
Although the explanation was given only for systems, DyFeCo, NdDyFe
Co, NdTbDyFeCo, and GdFeCo systems have similar effects. A similar effect can be obtained even if a small amount of additives are included.

Various combinations of metals used in the mold are also possible. However, the mold that comes into contact with the poured metal needs to be made of a metal with a higher melting point than the poured metal. In addition, for metals (Pr in Example 1) whose melting point is below the melting point of pouring and above the temperature of the mold at the time of installation, it is necessary to change the element depending on the composition system of the target and the thermal design of the mold. Various elements such as Cu, Sn, and Pb can be used.

A sectional view of the mold in the casting method.

Applicant Seiko Epson Co., Ltd. Agent Patent Attorney Kizobe Suzuki et al. - Natori [Effects of the Invention] By using the method for manufacturing a sputtering target of the present invention, a good sputtering target without microcracks can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a mold in an embodiment of the present invention.

Claims (2)

[Claims] (1) A target casting mold for sputtering, which is characterized in that the mold is formed from two or more types of metals, in a casting preparation mold for a sputtering casting target whose main composition is a rare earth transition metal. (2) The sputtering target according to claim 1, characterized in that the melting point of at least one metal used in the mold is below the melting point of pouring and above the temperature of the collar mold when installed. Casting mold.