JPS58511B2 - Manufacturing method of target material for sputtering - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a target for a sputtering apparatus suitable for forming an alloy thin film or an intermetallic compound thin film containing two or more elements, particularly Nb and Ge, on a substrate.

In recent years, there has been an increasing demand for producing thin films of alloys and intermetallic compounds made of two or more constituent elements by sputtering on substrates as semiconductor materials, superconducting materials, electronic component materials, and the like.

In this case, the requirements for sputtering target production are: ■ The composition of the component elements must be accurately and easily controllable;
■It is easy to mold into a predetermined shape, and ■It is less likely to contain impurities.

However, the conventional manufacturing methods include (1) a method of producing an alloy plate with a composition approximately equal to the composition of the thin film to be obtained by a melting method, (2) a method by sintering, and (3) a method of producing an alloy plate consisting of component elements. There was a method of sputtering two metal plates at the same time, either by setting them on the same cathode target or by using them for individual cathodes.

However, in method 1), when the two elements of the material to be sputtered do not dissolve into each other, large segregation occurs, especially when attempting to form an intermetallic compound.

Furthermore, when two elements with greatly different melting points and vapor pressures at the melting temperature are melted in vacuum to avoid contamination by impurities, it is difficult to create an alloy with the desired composition ratio because the component composition changes due to evaporation. However, this method was not suitable for satisfying the manufacturing requirements mentioned above, as it involved adding an extra material that easily evaporates and controlling the dissolution time, which resulted in a large amount of material loss.

Next, method (2) includes (A) a method of sintering the material without applying pressure near the melting temperature of the constituent elements, and (B) a method of mechanically unidirectionally unidirectionally sintering the material in a carbon die in a predetermined temperature atmosphere. There is a method of pressurizing the material, but it has the following disadvantages and is not suitable as a target manufacturing method that satisfies the initial requirements.

Method (A) involves high temperature and evaporation during sintering, making it difficult to precisely control the composition.

In method (B), (a) a large amount of constituent elements of the carbon die enter the sintered body from the surface of the die.

Therefore, it is not suitable for producing target materials for producing high-purity superconducting materials.

(b) Since pressure is applied only in one direction, the pressure distribution is not uniform, and the low melting point metal particles are pushed in the direction of lower pressure, causing segregation and making it impossible to obtain a sintered body with a uniform composition.

Therefore, it is unsuitable as a target material for producing superconducting materials that require a uniform composition ratio.

(c) Constituent elements of the sintered body enter the inside of the die during sintering, and it is necessary to replace the die with a new one every time sintering is performed, increasing sintering costs.

Therefore, this method is not suitable for manufacturing targets in large quantities.

When attempting to form an alloy thin film with a desired composition ratio using method (3), the composition of the thin film is determined by considering the sputtering rate so that the surface area ratio of the component element metals on the target surface is In this case, it is necessary to disperse the component metals on the surface of the target so that the thin film formed on the substrate does not have a non-uniform composition depending on the location. There were limitations, and unless done well, a thin film with a uniform composition could not be obtained, resulting in inconveniences.

The present invention provides a manufacturing method for eliminating such conventional drawbacks and providing a target that satisfies the three requirements mentioned at the beginning.

Metal powders with controlled purity of the elements constituting the alloy or compound desired to be made into a thin film are prepared and mixed uniformly by a conventionally well-known powder metallurgy method.

Thereafter, it is inserted into a glass container having a structure suitable for obtaining the desired target shape, and vacuum sealed.

Since it is necessary to vacuum-seal the powder after removing moisture and gas adsorbed on the surface of the powder, consideration must be given to evacuation while heating at an appropriate temperature of 70°C to 500°C.

Subsequently, by applying pressure while heating the entire glass container, the metal powder in the glass container is compressed and integrated, and a target having sufficient strength as a target can be prepared.

According to this method, since the component powders are mixed in a predetermined amount, the ratio of the components can be accurately controlled, and since the work is carried out by sealing the powder in a glass container, there is no need to worry about evaporation loss during heating and pressurization.

In addition, as long as the purity is properly controlled at the stage of preparing the initial powder, there is no risk of contamination with impurities since the powder is stored in a glass container.

The surface of the heated and pressurized material is covered with a glass material, so after the integration is completed, the glass material is removed, and in order to achieve the dimensional accuracy of the target shape, it is cut using an appropriate method known in the past. It can be polished and used as a target material.

The vacuum level of the container sealed in the glass container is 1 to prevent oxidation.
A high vacuum of O-3 Torr or higher is desirable.

The heating temperature T and the pressurizing condition P are related to each other, but as a result of experiments, the temperature is Tm, p, l, the melting point of the material with the lowest melting point among the constituent elements, and the melting point of the material with the higher melting point. Let Tm, p, h be 00-5T, p, l≦T≦
The range of Tm, p, and h is good.

If it is less than 0.5 Tm, p, l, an integrated target with sufficient strength cannot be obtained, and there is a problem that it will be destroyed during subsequent cutting and polishing.

The pressure P is preferably within a range determined by the following equation.

In the case of Nb and Ge of the present invention, C1=3.31°C
2=2.30, and below this range a target with sufficient strength cannot be obtained.

Further, the upper limit of the pressure P is self-limited by the upper limit of the pressurizing device used.

The present invention will be explained in detail below.

As target materials, Nb powder (purity 99.9, melting point 2468°C) and Ge powder (purity 99.999%, melting point 936°C) were used.
.degree. C.) with a particle size of 140 microns, and the powders are uniformly mixed so that the Nb/Ge composition ratio of the sputtered thin film to be obtained is 3/1.

This mixed powder was prepared using Pyrex glass (softening temperature: 750
degree of vacuum 10-5 Torr (temperature 400
℃) for 20 minutes to remove moisture and impurities that are resistant to adhesion to the powder, and then heat to remove gas, and then vacuum sealing is performed.

This container was heat-treated at 850℃ for 3 hours to soften the glass, and in that state, it was heated to 200kg/cm using argon gas.
Compression sintering is performed for 1 hour at step 2.

P in the Nb-Ge system conducted to set this condition
The relationship between T and T is as shown in FIG.

Thereafter, heat treatment is performed at 850° C. for 3 hours with the pressure removed.

The sintered body thus obtained had the shape and dimensions shown in FIG. 2, and was found to be shrunk and integrated.

By grinding the surface of this sintered body with a surface grinder, the glass adhesion on the surface layer could be easily removed.

When impurities were analyzed using a microanalyzer, Si
, Al, B, and other glass components were kept on the order of several ppm.

When sputtering was performed using this ground sintered body as a target material, it was confirmed from the microanalyzer measurement results that the composition ratio of the sputtered thin film obtained varied within ±2 coefficient within a diameter of at least 50 mm. is.

Furthermore, when the critical temperature of the obtained thin film was measured, a value of 20.5 was observed, indicating that the predetermined Nb/Ge composition ratio was 3/3.
It is determined that the value is 1.

In addition, in Fig. 1, a is 2 mm, b is 8 mm, and e is 10
0mmφ, d is 10m, e is 6mm, f in Figure 2
is 80mmφ.

In FIG. 3, it was determined by experiment that sintering was possible in the shaded area, and a sample of the example was prepared at point (■).

In the figure, ○ marks indicate that sintering is possible, and X marks indicate that sintering is not possible.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams showing the shape of a glass container and the shape of a sintered body in an example of the present invention, and FIG. 3 is a chart explaining the relationship between pressure and temperature in the present invention.

Claims (1)

[Claims] In a method for manufacturing a target material used in sputtering to form a thin film of an alloy or an intermetallic compound consisting of 1Nb and Ge on a substrate, granular or powdered constituent elements with a grain size of 100 nm or less are uniformly distributed in a predetermined manner. A glass material that softens enough to be deformed when pressure is applied at heating temperature, but maintains strength enough to protect the constituent elements in the container from contact with the outside world. The process consists of a step of vacuum sealing the container in a container made of the same material, and a step of compression molding it by isotropically applying a pressure P in an inert gas while heating it. The heating temperature T is set in the range of ≧0.5Tm, P-1, and the pressure P is determined by C1 and C2 depending on the material. As a constant, constant C1=3.31. C2=2
．． 30, and is set within the range shown by the formula: