KR101290941B1 - Method for storing target comprising rare earth metal or oxide thereof - Google Patents

Abstract

As a storage method of the target which consists of a rare earth metal or its oxide, The rare earth metal or the oxide of the rare earth metal same as the oxide target stored in this container is introduce | transduced as a drying agent in the container for storage or the film-shaped seal | sticker of the said target, and the said container for storage Or the sealing method of the target which consists of a rare earth metal or its oxide characterized by sealing and storing a film-shaped seal | sticker. It is an object of the present invention to study a method for storing a target made of a rare earth metal or an oxide thereof, to suppress oxidation of the target due to air intrusion and differentiation by hydroxylation, and to provide a technique that enables long-term storage.

Description

METHODS FOR STORING TARGET COMPRISING RARE EARTH METAL OR OXIDE THEREOF

The present invention relates to a method for storing a target composed of rare earth metals or oxides thereof which are easily powdered by oxidation or hydroxide.

Rare earth metals are contained in the earth's crust as mixed composite oxides. Rare earth metals are given this name because they are separated from relatively rare minerals, but they are by no means rare from the entire crust. In recent years, rare earth metals have been attracting attention as electronic materials and are being researched and developed.

Among these rare earth metals, lanthanum (La) is drawing attention in particular. Briefly introducing this lanthanum, the lanthanum has an atomic number of 57 and a white metal having an atomic weight of 138.9, and has a close hexagonal structure at room temperature. Melting | fusing point is 921 degreeC, boiling point 3500 degreeC, and density 6.15 g / cm <3>, The surface is oxidized in air, and it melt | dissolves in water gradually.

Hot water, soluble in acid. There is no ductility, but there is a little malleability. The resistivity is 5.70 x 10 &lt; ^-6 &gt; Oxide (La ₂ O ₃ ) is burned above 445 ℃ (See physicochemical dictionary). Rare earth metals generally have a stable compound of oxidized water 3 but are lanthanum trivalent.

This lanthanum is a metal attracting attention as an electronic material, such as a metal gate material and a high dielectric constant material (High-k). Rare earth metals other than lanthanum have similar properties to lanthanum.

Rare earth metals such as lanthanum are materials that are difficult to be highly purified because of the problem of being easily oxidized during purification. Moreover, when rare earth metals, such as lanthanum, are left to air, since it oxidizes and discolors in a short time, there exists a problem that handling is not easy.

In recent years, a thin film is required as a gate insulating film in a next-generation MOSFET. However, in SiO _{2 which} has been used as a gate insulating film so far, the leakage current due to the tunnel effect has been increased, making it difficult to operate normally.

For this reason, HfO ₂ , ZrO ₂ , Al ₂ O ₃ having a high dielectric constant, high thermal stability, and a high energy barrier to holes and electrons in silicon are replaced. , La ₂ O ₃ Is being proposed. In particular, among these materials, evaluation of La ₂ O ₃ is high, electrical properties are investigated, and research reports as gate insulating films in next-generation MOSFETs have been made (see Non-Patent Document 1). However, and in the case of the Patent Document, it is included in this study La ₂ O ₃ film, and is not specifically mention about the characteristics and behavior of the La metal.

As mentioned above, the rare earth metal and its oxide, such as lanthanum, are still in the research stage. However, when investigating the properties of such rare earth metal and its oxide, the rare earth metal and its oxide are present as sputtering target materials. When the thin film of the rare earth metal and its oxide is formed on the substrate, the interface behavior with the silicon substrate, and the rare earth metal compound can be formed, and the characteristics of the high-k gate insulating film can be easily investigated. Moreover, it has a big advantage that the freedom as a product increases.

However, even if a lanthanum sputtering target is produced, it will be oxidized in air for a short time as mentioned above. In general, a stable oxide film is formed on the surface of the metal target. However, since it is usually very thin, it is not peeled off at the initial stage of sputtering and thus does not significantly affect the sputtering characteristics. However, in the lanthanum sputtering target, an oxide film becomes thick and a fall of electrical conductivity arises and it causes the sputtering defect.

In addition, when left in the air for a long time, it reacts with moisture in the air to be covered with a white powder of a hydroxide, and eventually to a state that becomes powdered, a problem arises that normal sputtering is impossible. For this reason, it is necessary to take a vacuum pack immediately after covering a target, or to cover it with fats and oils, and to take measures to prevent oxidation and hydroxide.

As a storage method of the rare earth metal, storage in mineral oil is common in order to avoid contact with the atmosphere, but when used as a sputtering target, it is necessary to clean the mineral oil before use to remove it. However, there is a problem that cleaning itself is difficult due to the reactivity with oxygen, moisture, carbon dioxide as described above.

Therefore, storage and packing by a vacuum pack are normally required. By the way, even in the state which vacuum-packed, even the slight moisture which permeate | transmits the film to be used, since powdering by oxidation and hydroxide advances, long-term storage in the state which can be used as a sputtering target was difficult.

According to the known art, a method of covering a holocathode sputtering target with a resin bag (see Patent Document 1), a method of applying a protective film of a plastic film to the target (see Patent Document 2), and no detachable particles exist The method of packing a target using the film of the non-surface (refer patent document 3), the manufacturing method of a storage container of a target using the top cover of a transparent acrylic resin, the method of screw fixing (refer patent document 4), and a sputtering target There is a method (see Patent Document 5) for encapsulating in a bag-shaped article. However, these enclose a target using the cover of resin or a resinous film, and are not enough as the storage method of the target which consists of a rare earth metal or its oxide.

International publication WO2005 / 037649 publication Japanese Laid-Open Patent Publication 2002-212718 Japanese Laid-Open Patent Publication 2001-240959 Japanese Patent Laid-Open No. 8-246135 Japanese Patent Laid-Open No. 4-231461

 Esuke Tokumitsu and two others, "Study of Oxide Materials for High-k Gate Insulators", The Institute of Electrical and Electronics Engineers Materials, Vol.6-13, Page.37-41, issued September 21, 2001

The present invention studies a method for storing a target made of rare earth metal or an oxide thereof, suppresses oxidation and hydroxylation of the target due to air retention and invasion, and enables long-term storage in a state capable of being used as a sputtering target. It is an object to provide a technique for termination.

According to the present invention,

1) A method for storing a sputtering target made of a rare earth metal or an oxide thereof, wherein the oxide of the rare earth metal that is the same as the target made of the rare earth metal or an oxide thereof stored in a container for storage of the target or a film-like sealant is used as a drying agent. A method of storing a target made of a rare earth metal or an oxide thereof, which is introduced and sealed by sealing the container or film-shaped seal for storage.

2) A storage method of a target made of a rare earth metal or an oxide thereof, wherein the rare earth metal oxide having a higher hygroscopicity than the rare earth metal or these oxide target materials to be stored is stored as a desiccant in a container or film-shaped seal for the target. The present invention provides a method for storing a target made of a rare earth metal or an oxide thereof, wherein the storage container or film-shaped seal is sealed and stored.

Further, according to the present invention,

3) In the case of the target which consists of two or more rare earth metals or these oxides, the rare earth metal oxide with the largest hygroscopicity is used as a desiccant, The storage method of the target which consists of the rare earth metals or these oxides of 2) characterized by the above-mentioned.

4) The storage method of the target which consists of the rare earth metal in any one of said 1) -3) or these oxides characterized by the vacuum sealing method.

5) The means for sealing storage is a vacuum seal using a flexible film, and the method for storing a target made of the rare earth metal or oxides thereof according to any one of 1) to 4) above is provided.

Further, according to the present invention,

6) Encapsulation of the target comprising the rare earth metals or oxides thereof according to any one of 1) to 5) above, wherein the storage method encapsulates and seals a dew point-an inert gas of 80 ° C. or less. How to save

7) Storing or filling the rare earth metal oxide to be used as a drying agent in a space generated when encapsulated, to store a target made of the rare earth metal or oxides thereof according to any one of 1) to 6) above. Way

8) The rare earth metal which comprises the said target contains La or La, The storage method of the target which consists of the rare earth metal in any one of said 1) -7) or these oxides.

9) The rare earth metal oxide used as a drying agent is La oxide, The storage method of the target which consists of the rare earth metal in any one of said 1) -8) or these oxides characterized by the above-mentioned.

10) The rare earth metal according to any one of 1) to 9) above, wherein the moisture permeation amount of the flexible film used for bag storage or the moisture penetration amount from the outside of the container is 0.1 g / m 2 · 24 h or less. A storage method for a target made of these oxides is provided.

When a target made of a conventional rare earth metal or an oxide thereof is encapsulated and stored in a sealed container or a plastic film, when left for a long time, it reacts with oxygen and moisture to be covered with a white powder of a hydroxide. Although the problem that sputtering becomes impossible arises, the target stored in the container for storage or the film-shaped seal of this invention has a big effect that such a problem does not generate | occur | produce.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows the example at the time of laminating a La oxide powder thinly to the surface and side surface of a La target, and vacuum-packing this.
It is a figure which shows the example which vacuum-packed the La oxide powder in the space of the step | step of a La target and BP.
FIG. 3 is a diagram showing an example in which a La target is placed in a metal container, a La oxide powder is filled around the La target, and the surrounding air is once vacuum-sealed after replacing the surrounding air with argon at a dew point of 80 ° C. or lower. .
Fig. 4 shows a metal alloy target composed of La and Er in a metal container, and next, a La oxide block sintered at a step between the target and BP, and the air in the container is replaced with argon gas, followed by vacuumization. It is a figure which shows an example.
It is a figure which shows the example in the case of vacuum sealing a La target with a film.
It is a figure which shows the example at the time of vacuum-sealing a La target with a film and putting silica gel as a drying agent.
7 is a diagram showing an example in a vacuum bag for La ₂ O ₃ as a target film.

Rare earths, in particular lanthanum and oxides of lanthanum, are known to be extremely hygroscopic (reactive with moisture). Therefore, until now, it has been a problem whether lanthanum and lanthanum oxide are absorbed in the following or stored in an environment with few moisture.

However, when lanthanum oxide is more hygroscopic than lanthanum, the lanthanum oxide (sintered body such as powder, plate or block) is buried, placed or placed on the target surface when the lanthanum target is stored. This is to prevent oxidation and hydroxylation of the body.

In the case of storing the lanthanum oxide target, moisture can be absorbed and removed more effectively by encapsulating powder and granular lanthanum oxide having a larger surface area, so that deterioration due to hydroxylation of the target can be prevented.

That is, the storage method of the target which consists of the rare earth metal or these oxides of this invention introduce | transduces the oxide of the rare earth metal or these oxide targets and the same rare earth metal as a desiccant in the storage container or film-shaped seal | sticker. will be.

At this time, even if the lanthanum oxide reacts with water to be hydrated, powdered, and adhered to the target surface, since it is a compound of the same metal and is powder, it is not a cause of contamination since it is easy to remove. This point is a remarkable advantage compared with the case of using the drying agent which consists of another metal.

In addition, when contamination by other rare earth metals is not particularly a problem, an oxide of a rare earth metal having greater hygroscopicity than a rare earth metal or its oxide target material to be stored is introduced as a desiccant into a container for storing a target or a film-shaped sealant. The sealing container or the film-shaped seal can be sealed and stored.

In the case of the target which consists of two or more rare earth metals or these oxides, the rare earth metal oxide with the largest hygroscopicity can also be used as a desiccant.

As for the method of sealing and storing, it is more preferable not to let an external air enter as much as possible, and it can be set as a vacuum sealing as one of the methods. Moreover, when vacuum-sealing and storing, it is preferable to vacuum-sealed after replacing the container or film-shaped seal with the inert gas of dew point -80 degrees C or less once. A flexible film is used as a means for sealing storage, and this can be vacuum-sealed as a sealed bag.

Although the vacuum sealing was demonstrated above, as a method of storage, it can also seal by sealing an inert gas of dew point -80 degrees C or less. All are to prevent the intrusion of outside air.

In this way, the outside air is blocked and moisture invasion of the outside air is suppressed as much as possible, but even if there is a slight invasion, the rare earth oxide used as a drying agent is restrained or filled in the space generated when encapsulating to suppress the oxidation of the target body. It becomes possible.

Generally, the target is bonded to a backing plate, for example, in the case of using a flexible film and vacuum sealing it as an airtight bag, the target may have a step between the backing plates so that voids may occur. Easy to occur Outside air tends to be stored in such a space. And the powder shape of a target will advance easily from there. It is preferable to fill a rare earth oxide as a desiccant with such a step or gap.

It will be understood that the rare earth oxide serving as the desiccant has a good powder or granule state with a large surface area in this sense. However, it is effective only to place a small mass of rare earth oxides in a place where outside air is likely to be stored.

In addition, although it is most effective to let the rare earth oxide and the target directly contact, the adhesion of the powder to the target surface may cause particle generation during sputtering. In such a case, even if it encloses in the state packed into the moisture-permeable film like a general desiccant, it is fully effective.

In the storage method of the target of the present invention, the rare earth metal constituting the target is particularly effective for a lanthanum target or a target containing lanthanum. Moreover, the said rare earth oxide used as a drying agent is lanthanum oxide. Although this is a superficial expression, as a method for storing a target made of a rare earth metal or an oxide thereof, the lanthanum oxide that is most likely to be hydroxy has a high inhibitory effect on the oxidation of the target made of the rare earth metal or an oxide thereof.

The moisture permeation amount of the flexible film used for bag storage or the moisture penetration amount from the outside of the container is 0.1 g / m 2 · 24 h or less, and the prevention of moisture intrusion is as much as possible. It is important as a storage method.

Table 1 shows a preferable example of the flexible film used for sealing storage and an example other than that. In this Table 1, it is effective to have the characteristic of GX barrier (brand name) or more. As shown in Table 1, GX barrier (brand name) and Al foil accommodation bag are preferable. Table 1 shows a representative example, not to mention that other flexible films can be used as long as the above conditions are satisfied.

Next, the example at the time of implementing this invention is demonstrated. In addition, this example is for ease of understanding, and does not limit the present invention. That is, other examples and modifications within the scope of the technical idea of the present invention are included in the present invention.

(Example 1)

It is an example when a La target is vacuum-packed and La oxide powder is thinly filled in the surface and side surfaces. This specific example is shown in FIG.

As shown in FIG. 1, the lanthanum oxide layer exists between the film and La target of a vacuum pack, and the moisture which remain | survives inside a vacuum pack and the water which permeate | transmits a film are absorbed by the lanthanum oxide powder, and it is mentioned as lanthanum hydroxide. Since it is fixed, the La target surface is effective for preventing the phenomenon that the surface of the La target reacts with water to form a hydroxide.

(Example 2)

The La target is vacuum-packed and La oxide powder is placed in the step space of BP (like an envelope of silica gel). This specific example is shown in FIG.

As shown in Fig. 2, in the vacuum pack, since the La oxide is absorbed and fixed as lanthanum hydroxide, the moisture remaining in the remaining space is effective for preventing the phenomenon in which the La target reacts with water to become a hydroxide and powdered. Do.

(Example 3)

After installing the La oxide target in the metal container, and filling it with La oxide powder around the target, the specific example of the example which replaced the surrounding air with argon of dew point -80 degrees C or less once, and further vacuum-sealed it 3 is shown.

As shown in Fig. 3, since lanthanum oxide absorbs the moisture remaining after the vacuum and is fixed as lanthanum hydroxide, it is effective for preventing the phenomenon that La reacts with water to become a hydroxide and powder.

(Example 4)

A metal alloy target composed of La and Er is placed in a metal container, and then a La oxide block sintered at the step between the target and BP is placed, and the air in the container is replaced with argon gas having a dew point of -80 ° C. or lower, followed by vacuum. It is an angry example.

As shown in Fig. 4, since lanthanum oxide absorbs the moisture remaining after the vacuum and is fixed as lanthanum hydroxide, it is effective for preventing the phenomenon that La reacts with water to become a hydroxide and powder.

(Comparative Example 1)

This is the case where the La target is vacuum sealed with a film. This specific example is shown in FIG. As shown in FIG. 5, the water and La target remaining slightly in the space formed between the vacuum pack film and the target reacted to form lanthanum hydroxide to be powdered.

(Comparative Example 2)

It is a case where a La target is vacuum-sealed with a film and silica gel was put as a drying agent. This specific example is shown in FIG.

As shown in FIG. 6, when silica gel was provided, it powdered faster than a case without silica gel. This is considered to be the lanthanum hydroxide because the moisture adsorbed on the silica gel is released and released into the vacuum pack film, thereby promoting the reaction between water and La. From this, it is understood that silica gel, which is generally used as a drying agent, is not helpful for preventing the pulverization phenomenon of the rare earth metal or the rare earth metal oxide, and is rather undesirable.

(Comparative Example 3)

This example is a case where the La ₂ O ₃ target is vacuum sealed in a film. This specific example is shown in FIG. As shown in FIG. 7, since La oxide (La ₂ O ₃ ) absorbs moisture remaining in the remaining space in the vacuum pack and is fixed as lanthanum hydroxide, the La ₂ O ₃ target reacts with moisture to form a hydroxide. And powdered.

As is clear from the above examples and comparative examples, in storage of a target made of rare earth metals or oxides thereof, an oxide of a rare earth metal identical to a target made of rare earth metals or oxides thereof stored in a sealed container or sealant is dried. It can be seen that introducing as is very effective. This makes it possible to effectively suppress differentiation by oxidation and hydroxylation of the target due to air retention and intrusion.

Industrial availability

Conventionally, when the oxide sputtering targets of rare earth metals and rare earth metals are left in air for a long time, a problem arises that normal sputtering is impossible due to reaction with moisture in the air and being covered with white powder of hydroxide. The storage method of the target which consists of rare earth metal or its oxide does not produce such a problem.

The storage method of the target which consists of the rare earth metal or its oxide of this invention introduce | transduces the oxide of the rare earth metal same as the target which consists of the rare earth metal or its oxide to be stored as a desiccant in the container of container or film form. Thereby, the state which reacts with the moisture in air and is covered with the white powder of hydroxide can be suppressed effectively.

This enables stable supply of the target as an electronic material such as a metal gate material and a high dielectric constant material (High-k), which is very useful industrially.

Claims (10)

As a storage method of the target which consists of a rare earth metal or these oxides, The oxide of the rare earth metal same as the target which consists of the rare earth metal or these oxides stored are introduce | transduced as a drying agent in the container or film-shaped seal | sticker of the said target, The storage method of the target which consists of rare earth metals or these oxides characterized by sealing and storing the said storage container or film-shaped seal | sticker. As a method for storing a target made of a rare earth metal or an oxide thereof, a rare earth metal oxide having a higher hygroscopicity than a rare earth metal or an oxide target material to be stored is introduced as a drying agent in a container or film-shaped seal for storage of the target. And a rare earth metal or a target consisting of oxides thereof, characterized in that the sealing container or film-shaped seal is sealed and stored. The method for storing a rare earth metal or an oxide target thereof according to claim 2, wherein in the case of a target composed of two or more rare earth metals or oxides thereof, an oxide of a rare earth metal having the highest hygroscopicity is used as a drying agent. The method for storing a target according to any one of claims 1 to 3, wherein the method of encapsulating and storing is a vacuum encapsulation. The method for storing a target according to any one of claims 1 to 3, wherein the means for encapsulation is a vacuum seal using a flexible film. 4. The method for storing a target according to any one of claims 1 to 3, wherein the method for encapsulating and encapsulating and encapsulating an inert gas having a dew point of -80 deg. C or lower is carried out. 4. The storage according to any one of claims 1 to 3, wherein the rare earth metal oxide to be used as a desiccant is placed or filled in a space generated when encapsulating the rare earth metal or an oxide thereof. Way. The method of storing a target according to any one of claims 1 to 3, wherein the rare earth metal constituting the target contains La or La. The said rare earth metal oxide used as a drying agent is La oxide, The storage method of the target which consists of rare earth metals or these oxides of any one of Claims 1-3 characterized by the above-mentioned. The rare earth metal according to any one of claims 1 to 3, wherein the moisture permeation amount of the flexible film used for bag storage or the moisture penetration amount from the outside of the container is 0.1 g / m 2 · 24 h or less. The storage method of the target which consists of these oxides.

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