TWI542704B - A high purity lanthanum, a high purity lanthanum, a sputtering target composed of a high purity lanthanum, and a metal gate film having a high purity lanthanum as a main component - Google Patents

Description

High-purity ruthenium production method, high-purity ruthenium, a sputtering target composed of high-purity ruthenium, and a metal gate film containing high-purity ruthenium as a main component

The present invention relates to a method for producing high-purity germanium, a high-purity germanium, a sputtering target composed of high-purity germanium, and a metal gate film containing high-purity germanium as a main component.

The rare earth element contains lanthanum (La), but is contained in the earth's crust as a mixed resource in the form of a mixed composite oxide. Since rare earth elements are separated from the presence of relatively rare minerals, they are given the name, but in terms of the earth's crust as a whole, it is never rare.

It is a white metal with an atomic number of 57 and an atomic weight of 138.9. It has a complex hexagonal structure at room temperature. The melting point is 921 ° C, the boiling point is 3500 ° C, the density is 6.15 g / cm ³ , the surface will be oxidized in the air, and will slowly dissolve in water. Soluble in hot water, acid. No ductility, but slightly malleable. The resistivity was 5.70 × 10 ^-6 Ωcm. It burns to oxide (La ₂ O ₃ ) at 445 ° C or higher (refer to the Physical Chemistry Dictionary).

The rare earth element is generally stable in the form of a compound having an oxidation number of 3, and is also trivalent. Recently, we are researching and developing electronic materials such as metal gate materials and high-k materials (High-k), which are highly regarded metals.

Since the base metal has a problem of being easily oxidized during purification, it is a material which is difficult to be highly purified, so that a high-purity product does not exist. Further, since the base metal is placed in the air, it is oxidized to black in a short time, so that it is difficult to handle.

Recently, as a gate insulating film in a next-generation MOSFET, thin film is required, but SiO ₂ used as a gate insulating film has been increased in leakage current due to a tunnel effect. It is difficult to operate normally.

Therefore, as an alternative thereto, the industry has proposed HfO ₂ , ZrO ₂ , Al ₂ O ₃ , and La ₂ O ₃ having a high dielectric constant, high thermal stability, and high energy barriers with respect to holes and electrons in the crucible. In particular, among these materials, the evaluation of La ₂ O ₃ is high, and studies have been conducted to study the electrical characteristics thereof as a gate insulating film in a next-generation MOSFET (see Non-Patent Document 1). However, in the case of this non-patent document, the subject to be studied is a La ₂ O ₃ film, and the characteristics and behavior of the La element are not specifically mentioned.

Further, as a method of purifying a rare earth metal, a technique of reducing a rare earth metal halide by using calcium or calcium hydride has been proposed about 20 years ago. In the case of the rare earths, the slag separation jig is used as a means for separating the slag, and the problem of the presence of the ruthenium metal element and the purification means are hardly disclosed (see Patent Document 1). .

Thus, for yttrium (yttria), it is still in the research stage. When studying the properties of yttrium oxide (yttrium oxide), if the ruthenium metal itself exists in the form of a sputtering target, it has the following advantages: A tantalum film can be formed on the substrate, and the behavior of the interface with the tantalum substrate can be easily studied, and the characteristics of the high dielectric constant gate insulating film can be easily studied after further formation of the germanium compound, and the degree of freedom as a product is increased.

However, even if a ruthenium sputtering target is produced, oxidation occurs in the air for a short time (about 10 minutes) as described above. If an oxide film is formed on the target, A decrease in conductivity occurs, resulting in poor sputtering. Further, if it is left in the air for a long period of time, it will react with the moisture in the air to be covered with the white powder of the hydroxide, and may cause a problem that normal sputtering cannot be performed.

Therefore, after the target is produced, it is necessary to immediately perform vacuum packaging or take anti-oxidation measures covered with grease, but this is a very complicated operation. Due to such problems, the target of bismuth elements has not yet been put into practical use.

Further, a problem in the case where a film is formed by sputtering using a ruthenium target is a generation of a nodule on the surface of the target. This protrusion induces an abnormal discharge and generates particles caused by cracking of a nodule or the like.

The generation of particles may cause deterioration of the defect rate of the metal gate film or the semiconductor element and the device. Since carbon (graphite) contained in bismuth is a solid matter, it is a problem of large size, and since carbon (graphite) has electrical conductivity, it is difficult to detect and it is required to reduce it.

Further, as described above, in the case of a material which is difficult to be highly purified, in addition to the above carbon (graphite), it is preferable to reduce the contents of Al, Fe, and Cu in order to exhibit the characteristics of ruthenium. Further, since alkali metals, alkaline earth metals, transition metal elements, high melting point metal elements, and radioactive elements also affect semiconductor characteristics, it is expected to reduce the content thereof. Based on this situation, it is expected that the purity of ruthenium is 4N or more.

However, there is a problem that it is extremely difficult to remove the lanthanide elements other than ruthenium. Generally, since the properties of the lanthanoid elements other than lanthanum are similar, a slight mixing does not become a problem. But of course, I hope that it will also belong to rare earths (including The elements of the lanthanide element are reduced.

Moreover, it is not a big problem that the gas components are slightly mixed. Further, since the gas component is usually difficult to remove, the purity is usually not included in the gas component.

Previously, the characteristics of niobium, the manufacture of high-purity niobium, and the behavior of impurities in the target were not fully known. Therefore, it is expected to solve the above problems as soon as possible.

Patent Document 1: Japanese Patent Laid-Open Publication No. 63-11628

Non-Patent Document 1: Deguang Yongsuke and two others, "Study on Oxide Materials for High-k Gate Insulation Films", Electronic Materials Research Society, Institute of Electrical Materials, Vol.6-13, Page.37-41, 2001 Published on September 21st.

An object of the present invention is to provide a method for stably providing high-purity germanium, a high-purity germanium, a sputtering target obtained by using the high-purity germanium, a metal gate film formed using the sputtering target, and the metal-containing film The technology of semiconductor components and devices for gate films.

The invention provides: 1) a method for producing a high-purity lanthanum having a purity of 4N or more, excluding rare earth elements and gas components other than ruthenium, which is a rare earth element and a gas other than ruthenium by using distilled calcium The ruthenium trifluoride raw material having a purity of 4N or more is reduced to produce ruthenium having a purity of 4N or more, and the reduced ruthenium is subjected to electron beam melting to remove volatile substances.

Further, the present invention provides: 2) a method for producing high-purity lanthanum having a purity of 4 N or more excluding a gas component, which is calculated by distillation of calcium The gas component and the ruthenium trifluoride raw material having a purity of 4 N or more are reduced to produce a ruthenium having a purity of 4 N or more, and the reduced ruthenium is subjected to electron beam melting to remove the volatile matter.

Further, the present invention provides: 3) A method for producing a high-purity lanthanum according to the above 1) or 2), wherein Al, Fe, and Cu are each 10 wtppm or less. 4) The method for producing high purity niobium according to the above 1) or 2), wherein Al and Fe are each 5 wtppm or less, and Cu is 1 wtppm or less.

Further, the present invention provides: 5) The method for producing high purity ruthenium according to the above 1) or 2), wherein the ruthenium has a purity of 4N5 or more. 6) The method for producing high purity ruthenium according to any one of the above 1) to 5), wherein C is 200 wtppm or less. The method for producing high-purity lanthanum according to any one of the above 1) to 6), wherein the total amount of the gas component is 1000 wtppm or less. 8) The method for producing high-purity lanthanum according to any one of the above 1) to 7), wherein the total amount of the rare earth element other than cerium is 10 wtppm or less.

Further, the present invention provides: 9) A high-purity lanthanum, which does not include rare earth elements and gas components other than cerium, has a purity of 4 N or more, and Al, Fe, and Cu are each 10 wtppm or less.

Further, the present invention provides: 10) The high-purity lanthanum according to the above 9), which has a purity of 4 N5 or more, a purity of 5 wtppm or less, and a Cu content of 1 wtppm or less, excluding a gas component. 11) A high purity hydrazine according to the above 9) or 10), wherein C is 200 wtppm or less. 12) The high purity hydrazine according to any one of the above 9), wherein the total gas component is 1000 wtppm or less. 13) The high purity cerium according to any one of the above 9) to 12), wherein the total amount of the rare earth element other than cerium is 10 wtppm or less.

Further, the present invention provides: 14) A sputtering target which is obtained by using the high purity hydrazine of any one of the above 9) to 13). 15) A metal gate film formed using the sputtering target of the above 14). 16) A semiconductor device and device comprising the metal gate film of the above 15).

The above-mentioned high-purity oxime is a novel substance, and the invention of the present invention is included. In the case of application as a gate insulating film in a MOSFET, a LaOx film is mainly formed, and in the case of forming such a film, in order to increase the degree of film formation freedom of forming an arbitrary film, a high purity germanium metal is required. . The invention of the present invention can provide materials that meet this requirement.

The rare earth elements contained in cerium include Sc, Y, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, in addition to lanthanum (La). The properties are similar, so it is difficult to separate and purify from La. In particular, Ce is similar to La, so it is not easy to reduce Ce.

Generally, a certain amount of rare earth elements are allowed to be contained. However, in order to utilize the characteristics of the lanthanum element, the content of the rare earth element is 100 wtppm or less, and further, it may be 10 wtppm or less. The invention of the present invention can achieve this goal.

The central object of the present invention is to solve the problem by making the purity of rare earth elements and gas components other than ruthenium 4N or more. Further, the object of the invention is to obtain high purity germanium in which aluminum (Al), iron (Fe) and copper (Cu) in the crucible are each 10 wtppm or less.

Generally, C, N, O, S, and H exist in the form of a gas component. Although these may exist in the form of a single element, they may exist in the form of a compound (CO, CO ₂ , SO _{2 ,} etc.) or a compound of a constituent element. Since these gas component elements have a small atomic weight and an atomic radius, if they are not contained in a large amount, even if they exist in the form of impurities, the material properties are not greatly affected. Therefore, in the case of purity, it is common that the purity does not include the gas component. Because of this meaning, the purity of the crucible of the present invention does not include the gas component.

However, since a large amount of gas components are not preferable, the total amount of gas components such as oxygen, nitrogen, and hydrogen can be made 1000 MPa or less as described later.

Prior to the invention of the present invention, it was proposed to produce a high purity crucible having a 4N grade or higher and further 4N5 or more.

The present invention can provide a sputtering target obtained by using the above-described high-purity germanium, a metal gate film formed using the sputtering target, and a semiconductor element and device including the metal gate film.

In the case of application as a gate insulating film in a MOSFET, as described above, a LaOx film is mainly formed. In the case of forming such a film, in order to increase the degree of freedom in forming a film forming an arbitrary film, a base metal having a high purity is required.

The invention of the present invention can provide materials that meet this requirement. Therefore, the high purity of the invention of the present invention is intended to include any combination with other substances when the target is produced.

The high purity crucible obtained by the above method was subjected to electron beam (EB) melting in a vacuum, and then solidified to form an ingot. By electron beam melting, the gas component can be greatly reduced, and the total amount of gas components such as carbon, oxygen, nitrogen, sulfur, and hydrogen can be made 1000 MPa or less. Further, although the gas component is removed during the electron beam melting, the number of tens to ppm of Ca remaining in the Ca reduction is reacted with the gas component, and Ca is also removed.

The ingot obtained in the above manner can be further cut into a prescribed size, and then subjected to a grinding step to form a sputtering target. Thereby, it is possible to produce a high-purity ruthenium target having a purity of 4N or more and a rare earth element and a gas component other than ruthenium, and having Al, Fe, and Cu of 10 wtppm or less, respectively.

Further, by using the above target to perform sputtering, a metal gate film of the same composition can be obtained. Such sputtering targets, metal gate films, and semiconductor devices and devices using the same are novel materials, and the present invention encompasses them.

The present invention has an excellent effect of stably providing a high-purity ruthenium production method, a high-purity ruthenium, a sputtering target obtained by using the high-purity ruthenium, a metal gate film formed using the sputtering target, and having The semiconductor device and device of the metal gate film.

In the present invention, a rare earth element other than cerium and a gas component can be used, and a cerium trifluoride raw material having a purity of 4 N or more can be used as a cerium raw material for high purity. The main impurities contained in these raw materials are Li, Na, K, Ca, Mg, Al, Si, Ti, Fe, Cr, Ni, Mn, Mo, Ce, Pr, Nd, Sm, Ta, W, and gas components. (N, O, C, H), etc. Commercially available ruthenium trifluoride raw materials have a purity of 4 N or more and generally have few impurities, but contain a large amount of gas components, and thus cannot be directly used.

The aluminum (Al) and copper (Cu) contained in bismuth are mostly used as alloy materials for substrates, sources, and drain electrodes in semiconductors, and even if they are contained in a small amount in the gate material, they may cause failure. . Further, since iron (Fe) contained in the crucible is easily oxidized, it may cause sputtering failure when used as a target, and even if it is not oxidized in the target, if it is oxidized after sputtering, If the volume expands, it is likely to cause a problem such as poor insulation, which may cause malfunction. For the above reasons, it is particularly problematic, so it is necessary to reduce it.

Further, although calcium reduction is carried out using ruthenium trifluoride as a ruthenium raw material, since Fe, Al, and Cu are mixed with calcium of the reduced material in the form of impurities, there is a possibility that impurities are mixed from the calcium reducing material. Therefore, reduction was carried out using distilled calcium having less than 20 ppm of Cu (further than 2 ppm of Cu).

Table 1 shows the comparison of the analytical values of commercially available Ca and distilled Ca (distillation once, distillation twice). The commercially available Ca and Cu in Table 1 are as high as 95 wtppm, and the risk of mixing Cu is increased when this commercially available Ca is used.

(calcium reduction)

The melting crucible used in the reduction is made of tantalum (Ta). Powdered LaF ₃ and bulk Ca were mixed into the crucible. Usually, the amount of Ca added as the reducing material is about 10% more than the calculated amount.

Slowly add the filler in the crucible that is placed in the reduction device Heat to 600 ° C, during which time the inside of the reduction device is sucked to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further heating, if the filler is heated to 800 ° C ~ 1000 ° C, will start the reaction. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is a rapid reaction and therefore ends quickly. In order to smoothly separate the purified metal from the slag, it can be kept at a temperature of about 50 ° C higher than the melting point of the La metal for several minutes.

The yield of metal La is about 97%. The main impurities are unreacted reducing materials and slag. Further, since the Ta which is a coffin may be mixed in the form of impurities, the reduction reaction should be carried out at a low temperature as much as possible. In this way, the metal La is obtained.

(electron beam melting)

When electron beam melting is performed on the tantalum molded body obtained in the above manner, it is carried out by irradiating a low-output electron beam to a crucible melting raw material in a furnace in a wide range. Usually, it is carried out at 9 kW to 32 kW. This electron beam melting can be repeated several times (2 to 4 times). If the number of times of electron beam melting is increased, high vapor pressure elements such as Ca, Mg, Mn, and Pb are removed. Moreover, the gas components such as oxygen, nitrogen, and hydrogen can be greatly reduced, and the total amount thereof can be less than 1000 wtppm.

Further, when the electron beam melting is performed, the gas component is removed as described above, but the number of cad to tens of ppm of Ca remaining during the Ca reduction is reacted with the gas component, and Ca is also removed.

Increasing the output of the electron beam has the effect that residual oxygen reacts with C, and the carbon mixed with helium becomes CO or CO ₂ gas, which is more removed. However, if the output is excessively increased, since the portion in contact with La in the furnace is made of water-cooled Cu, Cu contamination may occur, and therefore it must be stopped to a certain extent.

In the above, the rare earth element is excluded from the high purity lanthanum because the other rare earths themselves are technically very difficult to remove due to their chemical properties similar to ruthenium in the production of high purity ruthenium. In terms of the approximation of characteristics, even if it is mixed in the form of impurities, it does not cause significant characteristic changes.

Due to the above, it is acquiesced to allow other rare earths to mix to a certain extent, but it is of course less preferred when it is desired to improve the characteristics of the crucible itself.

According to the invention of the present invention, the total of the rare earth elements other than cerium may be 10 wtppm or less. This is one of the salient features of the invention of the present invention.

Further, the purity of the gas component is not more than 4N, and furthermore than 4N5, because it is difficult to remove the gas component, if it is calculated, it cannot be a standard for improving purity. Also, because of the general presence compared to other impurity elements, some of the existence is mostly harmless.

When forming a thin film of an electronic material such as a gate insulating film or a film for a metal gate, it is often performed by sputtering, and is an excellent method as a film forming means. Therefore, it is effective to use the above-described niobium ingot to produce a high-purity tantalum sputtering target.

The production of the target can be carried out by usual processing such as forging, rolling, cutting, finishing (grinding). In particular, the manufacturing steps are not limited and can be arbitrarily selected.

From the above manner, rare earth elements and gases other than ruthenium can be obtained. The component has a purity of 4 N or more, and Al, Fe, and Cu each have a purity of 10 wtppm or less.

Further, a high-purity tantalum ingot having a purity of 4 N5 or more, C of 200 wtppm or less, Al and Fe of 5 wtppm or less, and Cu of 1 wtppm or less can be obtained. Further, the carbon (C) is a gas component, but means that the gas component of C is limited to 200 wtppm or less, whereby the characteristics of the crucible can be further improved.

When the target is produced, the high-purity bismuth ingot is cut into a predetermined size, and then cut and polished.

Further, by using this high-purity target for sputtering, high-purity ruthenium can be formed on the substrate. Thereby, a rare earth element and a gas component other than ruthenium can be formed on the substrate, the purity is 4N or more, and the Al, Fe, and Cu are each 10 wtppm or less of a metal film having a high purity ruthenium as a main component, and can be on the substrate. No gas component is formed, the purity is 4N5 or more, C is 200wtppm or less, aluminum (Al) and iron (Fe) are respectively 5wtppm or less, copper (Cu) is 1wtppm or less, and the total of rare earth elements other than cerium is 10wtppm or less. It is a metal gate film with high purity bismuth as the main component. The film on the substrate reflects the composition of the target and forms a high purity tantalum film.

The use of the metal gate film can be used in the form of the above-mentioned high-purity ruthenium composition, but it can also be mixed with other gate materials or formed in the form of an alloy or a compound. In this case, it can be achieved by sputtering at the same time with other gate targets or by using a mosaic target for sputtering. The invention of the present invention includes such. Although the content of impurities varies depending on the amount of impurities contained in the raw materials, by using the above method, the respective impurities can be adjusted to the above values. The scope.

The present invention provides a technique for efficiently and stably providing a high-purity germanium obtained by the above-described method, a sputtering target composed of high-purity germanium, and a thin film for a metal gate containing high-purity germanium as a main component.

Example

Next, examples and comparative examples will be described. In addition, the embodiments and the comparative examples are for ease of understanding and are not intended to limit the present invention. That is, other embodiments and modifications within the scope of the technical idea of the present invention are also included in the present invention.

(Example 1)

A 4N purity ruthenium trifluoride raw material was used as a raw material for the treatment. Although metal ruthenium has recently been a material of great interest, the commercial product of metal ruthenium has a problem of low purity and quality.

On the other hand, ruthenium trifluoride is a commercially available product, and a high-purity material can be obtained. However, since the ruthenium trifluoride is not directly usable, it is necessary and important to efficiently and stably produce a high-purity metal ruthenium using the 4N-purinated ruthenium trifluoride raw material.

The analytical values of the antimony trifluoride raw material are shown in Table 2. Among them, examples of the impurities having a large content include the following elements. Na: 33 wtppm, Al: 3.5 wtppm, Si: 8.5 wtppm, S: 63 wtppm, Cl: 17 wtppm, Cu: 1.4 wtppm, Zn: 5.1 wtppm, C: 61 wtppm, N: 200 wtppm, O: 5600 wtppm, H: 1200 wtppm, containing many The gas composition.

On the other hand, the rare earth element has Ce: 63 wtppm, Pr: 14 wtppm, Nd: 9.2 wtppm, Sm: < 0.1 wtppm, etc., and relatively many impurities.

(calcium reduction of raw materials)

The melting crucible used in the reduction is made of crucible (Ta) of × 250 × H400. Powdered LaF ₃ : 14.1 kg and block Ca: 6 kg were mixed into the crucible. As Ca of the reducing material, Ca which was distilled once using the analysis values shown in Table 1 above was used, and the amount of addition was about 10% more than the calculated amount.

The filler in the crucible placed in the reduction device was slowly heated to 600 ° C, during which time the inside of the reduction device was suctioned to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further increase the heating temperature. If the filler is heated to 800 ° C ~ 1000 ° C, the reaction will start. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is an exothermic reaction and will end quickly. In order to smoothly separate the purified metal from the slag, it is maintained at a temperature about 50 ° C higher than the melting point of the La metal. Further, since the melting point of La is 950 ° C, the heating temperature is adjusted to +50 ° C, that is, 1000 ° C. In this way, the metal La is obtained.

The analytical values of the metal La are shown in Table 3. As shown in Table 3, Al: 8.1 wtppm, Si: 4.4 wtppm, Ca: 3.9 wtppm, Fe: 8.3 wtppm, Cu: 4.3 wtppm, Mo < 0.05 wtppm, Ta < 5 wtppm, W: 0.12 wtppm, C: 100 wtppm, N: 93 wtppm, O: 1400 wtppm, S < 10 wtppm, H: 12 wtppm.

Although it is a result of Ca reduction, Ca is abundant and the oxygen (O) content is also high.

(electron beam melting)

Next, the obtained tantalum molded body was subjected to electron beam melting. This is carried out by irradiating a low-output electron beam to a cerium melting raw material in a furnace in a wide range. Irradiation was carried out at a vacuum of 6.0 × 10 ^-5 to 7.0 × 10 ^-4 mbar and a melting output of 32 kW. This electron beam melting was repeated twice. The respective melting time is 30 minutes. Thereby, an EB melting ingot is produced. When the electron beam is melted, volatile substances can be volatilized and removed.

High purity hydrazine can be obtained by the above method. The analytical values of the high purity cerium after the electron beam melting are shown in Table 4. As shown in Table 4, Li < 0.005 wtppm, Na < 0.05 wtppm, Al: 2.4 wtppm, Si: 0.55 wtppm, Ca: 1.9 wtppm, Fe: 3.5 wtppm, Cu: 5.8 wtppm, Zn < 0.05 wtppm, Mo < 0.05 Wtppm, Ta < 5 wtppm, W: 0.09 wtppm, C: 110 wtppm, N: 100 wtppm, O: 440 wtppm, S < 10 wtppm, H: 10 wtppm, either of which satisfies the conditions of the present invention.

Moreover, oxygen and Ca which are not reduced when calcium is reduced can be greatly reduced.

In addition, when the rare earth element other than cerium exceeds 100 wtppm, since the purification step of the present embodiment does not directly affect the rare earth element, the rare earth element other than the cerium after the electron beam melting will exceed 100 wtppm.

Depending on the application, rare earth elements other than cerium may not be particularly problematic. Therefore, it should be readily understood that the present invention encompasses all conditions for producing high purity cerium having a purity of 4N or more of rare earth elements and gas components other than cerium.

The tantalum ingot obtained in the above manner was hot pressed as needed, and further mechanically processed and ground to prepare a disk-shaped target of 140 × 14t. The weight of this target was 1.42 kg. Further, it was bonded to a support plate to form a target for sputtering. Thereby, the target for high-purity ruthenium sputtering of the above-mentioned component composition can be obtained. Further, since this target has high oxidizing property, it is preferably stored or transported in a vacuum package.

(Comparative Example 1)

A commercially available product having a purity of 2N5 to 3N as shown in Table 5 below is used as a raw material for the treatment. The commercially available product used in Comparative Example 1 was composed of a plate member of 120 mm square × 30 mmt. One piece has a weight of 2.0 kg to 3.3 kg, and 12 pieces of such a plate are used, and a total of 24 kg of raw materials are used. Since these slab-shaped bismuth raw materials are substances which are very easily oxidized, aluminum is vacuum-packed.

If the main impurities shown in Table 5 are listed, Li: 1200 wtppm, Na: 4.3 wtppm, Mg: 33 wtppm, Al: 120 wtppm, Si: 160 wtppm, S: 50 wtppm, Ti: 5.7 wtppm, Cr: 21 wtppm, Mn: 36 wtppm, Fe: 330 wtppm, Cu: 17 wtppm, Zr: 0.31 wtppm, C: 920 wtppm, N < 10 wtppm, O: 540 wtppm, S < 10 wtppm, H: 26 wtppm.

Next, using an EB melting furnace, melting was performed at a vacuum degree of 7.0 × 10 ^-5 to 3.5 × 10 ^-5 mbar, and a melting output of 32 kW, and an ingot was produced at a casting speed of 45 kg / h. When the electron beam is melted, volatile substances can be volatilized and removed.

A high-purity bismuth ingot of 22.54 kg can be obtained by the above method. The analytical values of the high purity hydrazine obtained in this manner are shown in Table 6.

As shown in Table 6, the main impurity elements in the crucible after electron beam melting were as follows. Li: 12 wtppm, Na: 0.86 wtppm, Mg: 2.7 wtppm, Al: 72 wtppm, Si: 29 wtppm, S: 30 wtppm, Ti: 1.9 wtppm, Cr: 4.2 wtppm, Mn: 6.4 wtppm, Fe: 130 wtppm, Cu: 9.2 wtppm, Zr: 0.22 wtppm, C: 1100 wtppm, N < 10 wtppm, O: 680 wtppm, S: 13 wtppm, H: 23 wtppm.

As is clear from the above, it is impossible to reduce Al and Fe, and the decrease in gas composition is insufficient. Overall, compared with the foregoing embodiments, the amount of impurities is high, and the object of the present invention cannot be achieved.

(Example 2)

A 4N purity ruthenium trifluoride raw material was used as a raw material for the treatment. Although metal ruthenium has recently been a material of great interest, the commercial product of metal ruthenium has a problem of low purity and quality.

On the other hand, ruthenium trifluoride is a commercially available product, and a high-purity material can be obtained. However, since the ruthenium trifluoride is not directly usable, it is necessary and important to efficiently and stably produce a high-purity metal ruthenium using the 4N-purinated ruthenium trifluoride raw material.

The analytical values of the antimony trifluoride raw material are shown in Table 7. Among them, the main impurities include the following elements. Na: 33 wtppm, Al: 3.5 wtppm, Si: 8.5 wtppm, S: 63 wtppm, Cl: 17 wtppm, Cu: 1.4 wtppm, Zn: 5.1 wtppm, C: 61 wtppm, N: 200 wtppm, O: 5600 wtppm, H: 1200 wtppm, containing many The gas composition.

On the other hand, the rare earth element has Ce: 63 wtppm, Pr: 14 wtppm, Nd: 9.2 wtppm, Sm: < 0.1 wtppm, etc., and relatively many impurities.

(calcium reduction of raw materials)

The melting crucible used in the reduction is made of crucible (Ta) of × 250 × H400. Powdered LaF ₃ : 14.1 kg and block Ca: 6 kg were mixed into the crucible. As the Ca of the reducing material, Ca which was distilled twice was used for the analysis value shown in Table 1, and the amount of addition was about 10% more than the calculated amount.

The filler in the crucible placed in the reduction device was slowly heated to 600 ° C, during which time the inside of the reduction device was suctioned to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further increase the heating temperature. If the filler is heated to 800 ° C ~ 1000 ° C, the reaction will start. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is an exothermic reaction and will end quickly. In order to smoothly separate the purified metal from the slag, it is maintained at a temperature about 50 ° C higher than the melting point of the La metal. Further, since the melting point of La is 950 ° C, the heating temperature is adjusted to +50 ° C, that is, 1000 ° C.

The metal La can be obtained in this way. The analytical values of the calcium-reduced metal La are shown in Table 8.

As shown in Table 8, Al: 1.9 wtppm, Si: 0.55 wtppm, Ca: 5.2 wtppm, Fe: 0.69 wtppm, Cu < 0.05 wtppm, Mo < 0.05 wtppm, Ta < 5 wtppm, W: 0.09 wtppm, C: 120 wtppm, N: 90 wtppm, O: 290 wtppm, S < 10 wtppm, H: 5.9 wtppm. As described above, although it is a result of Ca reduction, there is a problem that a large amount of Ca is contained.

(electron beam melting)

Next, the obtained tantalum molded body was subjected to electron beam melting. This is carried out by irradiating a low-output electron beam to a cerium melting raw material in a furnace in a wide range. Irradiation was carried out at a vacuum of 6.0 × 10 ^-5 to 7.0 × 10 ^-4 mbar and a melting output of 32 kW. This electron beam melting was repeated twice. The respective melting time is 30 minutes. Thereby, an EB melting ingot is produced. When the electron beam is melted, volatile substances can be volatilized and removed.

High purity hydrazine can be obtained by the above method. The analytical values of the high purity cerium after the electron beam melting are shown in Table 9. As shown in Table 9, Li < 0.005 wtppm, Na < 0.05 wtppm, Al: 1.5 wtppm, Si: 0.42 wtppm, S: 4.9 wtppm, Ca: 0.16 wtppm, Fe: 0.65 wtppm, Cu < 0.05 wtppm, Zn < 0.05 Wtppm, Mo<0.05wtppm, Ta<5wtppm, W<0.05wtppm, C:140wtppm, N:50wtppm, O:150wtppm, S<10wtppm, H:22wtppm, can be further improved by using Ca which has been distilled twice The purity, either of them satisfies the conditions of the invention of the present invention. Moreover, oxygen and Ca which are not reduced when calcium is reduced can be greatly reduced.

The tantalum ingot obtained in the above manner was hot pressed as needed, and further mechanically processed and ground to prepare a disk-shaped target of 140 × 14t. The weight of this target was 1.42 kg. Further, it was bonded to a support plate to form a target for sputtering. Thereby, the target for high-purity ruthenium sputtering of the above-mentioned component composition can be obtained. Further, since this target has high oxidizing property, it is preferably stored or transported in a vacuum package.

(Example 3)

A rare earth trifluoride raw material containing 4N of rare earth is used as a raw material for the treatment. Although metal ruthenium has recently been a material of great interest, the commercial product of metal ruthenium has a problem of low purity and quality.

On the other hand, ruthenium trifluoride is a commercially available product, and a high-purity material can be obtained. However, since the ruthenium trifluoride is not directly usable, it is necessary and important to efficiently and stably produce a high-purity metal ruthenium using the 4N-purinated ruthenium trifluoride raw material.

The analytical values of the antimony trifluoride raw material are shown in Table 10. Among them, the following elements may be mentioned as a large amount of impurities. Na: 0.2 wtppm, Al < 0.05 wtppm, Si: 0.94 wtppm, Cl: 12 wtppm, Cu < 0.05 wtppm, Zn < 0.1 wtppm, C: 180 wtppm, N: 70 wtppm, O: 5200 wtppm, H: 540 wtppm, containing many gas components .

On the other hand, the rare earth element has Ce: 1.1 wtppm, Pr < 0.1 wtppm, Nd: 0.24 wtppm, Sm: 0.17 wtppm, etc., and impurities are not many. When a raw material having a low rare earth element is used as described above, the rare earth (but not including ruthenium) may have a purity of 4N.

(calcium reduction of raw materials)

The melting crucible used in the reduction is made of crucible (Ta) of × 250 × H400. Powdered LaF ₃ : 14.1 kg and block Ca: 6 kg were mixed into the crucible. As the Ca of the reducing material, Ca which was distilled once using the analytical value shown in Table 1 was used, and the amount of addition was about 10% more than the calculated amount.

The filler in the crucible placed in the reduction device was slowly heated to 600 ° C, during which time the inside of the reduction device was suctioned to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further increase the heating temperature. If the filler is heated to 800 ° C ~ 1000 ° C, the reaction will start. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is an exothermic reaction and will end quickly. In order to smoothly separate the purified metal from the slag, it is maintained at a temperature about 50 ° C higher than the melting point of the La metal. Further, since the melting point of La is 950 ° C, the heating temperature is adjusted to +50 ° C, that is, 1000 ° C. In this way, the metal La is obtained.

The analytical values of the metal La are shown in Table 11. As shown in Table 11, Al: 8.1 wtppm, Si: 4.5 wtppm, Ca: 9.9 wtppm, Fe: 9.2 wtppm, Cu: 4.3 wtppm, Mo < 0.05 wtppm, Ta < 5 wtppm, W: 0.12 wtppm, C: 100 wtppm, N: 93 wtppm, O: 400 wtppm, S < 10 wtppm, H: 12 wtppm.

Although it is a result of Ca reduction, Ca is abundant and the oxygen (O) content is also high.

(electron beam melting)

Next, the obtained tantalum molded body was subjected to electron beam melting. This is carried out by irradiating a low-output electron beam to a cerium melting raw material in a furnace in a wide range. Irradiation was carried out at a vacuum of 6.0 × 10 ^-5 to 7.0 × 10 ^-4 mbar and a melting output of 32 kW. This electron beam melting was repeated twice. The respective melting time is 30 minutes. Thereby, an EB melting ingot is produced. When the electron beam is melted, volatile substances can be volatilized and removed.

High purity hydrazine can be obtained by the above method. The analytical values of the high purity cerium after the electron beam melting are shown in Table 12. As shown in Table 12, Li < 0.005 wtppm, Na < 0.05 wtppm, Al: 7.5 wtppm, Si: 5.5 wtppm, Ca: 1.9 wtppm, Fe: 8.4 wtppm, Cu: 5.8 wtppm, Zn < 0.05 wtppm, Mo < 0.05 Wtppm, Ta<5wtppm, W: 0.09wtppm, C: 110wtppm, N: 100wtppm, O: 240wtppm, S<10wtppm, H: 10wtppm, which can be further improved by using high-purity lanthanum trifluoride, either Both meet the conditions of the invention of the present invention.

Moreover, oxygen and Ca which are not reduced when calcium is reduced can be greatly reduced. In the present embodiment, since the high-purity lanthanum trifluoride of 10 wtppm or less is used as the rare earth element other than cerium, the enthalpy after electron beam melting is similarly 10 wtppm or less.

The tantalum ingot obtained in the above manner was hot pressed as needed, and further mechanically processed and ground to prepare a disk-shaped target of 140 × 14t. The weight of this target was 1.42 kg. Further, it was bonded to a support plate to form a target for sputtering. Thereby, the target for high-purity ruthenium sputtering of the above-mentioned component composition can be obtained. Further, since this target has high oxidizing property, it is preferably stored or transported in a vacuum package.

(Example 4)

A 4N purity ruthenium trifluoride raw material was used as a raw material for the treatment. Although metal ruthenium has recently been a material of great interest, the commercial product of metal ruthenium has a problem of low purity and quality.

On the other hand, ruthenium trifluoride is a commercially available product, and a high-purity material can be obtained. However, since the ruthenium trifluoride is not directly usable, it is necessary and important to efficiently and stably produce a high-purity metal ruthenium using the 4N-purinated ruthenium trifluoride raw material.

The analytical values of the antimony trifluoride raw material are shown in Table 13. Among them, the following elements may be mentioned as a large amount of impurities. Na: 0.2 wtppm, Al < 0.05 wtppm, Si: 0.94 wtppm, Cl: 12 wtppm, Cu < 0.05 wtppm, Zn < 0.1 wtppm, C: 180 wtppm, N: 70 wtppm, O: 5200 wtppm, H: 540 wtppm, containing many gas components .

On the other hand, the rare earth element has Ce: 1.1 wtppm, Pr < 0.1 wtppm, Nd: 0.24 wtppm, Sm: 0.17 wtppm, etc., and impurities are not many. When a raw material having a low rare earth element is used as described above, the rare earth (but not including ruthenium) may have a purity of 4N.

(calcium reduction of raw materials)

The melting crucible used in the reduction is made of crucible (Ta) of × 250 × H400. Powdered LaF ₃ : 14.1 kg and block Ca: 6 kg were mixed into the crucible. As the Ca of the reducing material, Ca which was distilled twice was used for the analysis value shown in Table 1, and the amount of addition was about 10% more than the calculated amount.

The filler in the crucible placed in the reduction device was slowly heated to 600 ° C, during which time the inside of the reduction device was suctioned to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further increase the heating temperature. If the filler is heated to 800 ° C ~ 1000 ° C, the reaction will start. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is an exothermic reaction and will end quickly. In order to smoothly separate the purified metal from the slag, it is maintained at a temperature about 50 ° C higher than the melting point of the La metal. Further, since the melting point of La is 950 ° C, the heating temperature is adjusted to +50 ° C, that is, 1000 ° C. In this way, the metal La is obtained.

The analytical values of the metal La are shown in Table 14. As shown in Table 14, Al: 0.82 wtppm, Si: 0.47 wtppm, Ca: 2.1 wtppm, Fe: 1.3 wtppm, Cu < 0.05 wtppm, Mo < 0.05 wtppm, Ta < 5 wtppm, W < 0.05 wtppm, C: 120 wtppm, N: 90 wtppm, O: 260 wtppm, S < 10 wtppm, H: 16 wtppm.

Although it is a result of Ca reduction, Ca is abundant and the oxygen (O) content is also high.

(electron beam melting)

Next, the obtained tantalum molded body was subjected to electron beam melting. This is carried out by irradiating a low-output electron beam to a cerium melting raw material in a furnace in a wide range. Irradiation was carried out at a vacuum of 6.0 × 10 ^-5 to 7.0 × 10 ^-4 mbar and a melting output of 32 kW. This electron beam melting was repeated twice. The respective melting time is 30 minutes. Thereby, an EB melting ingot is produced. When the electron beam is melted, volatile substances can be volatilized and removed.

High purity hydrazine can be obtained by the above method. The analytical values of the high purity cerium after the electron beam melting are shown in Table 15. As shown in Table 15, Li < 0.005 wtppm, Na < 0.05 wtppm, Al: 0.75 wtppm, Si: 0.36 wtppm, Ca: 0.41 wtppm, Fe: 0.71 wtppm, Cu: 0.24 wtppm, Zn < 0.05 wtppm, Mo < 0.05 Wtppm, Ta<5wtppm, W<0.05wtppm, C: 110wtppm, N: 80wtppm, O: 150wtppm, S<10wtppm, H: 9.4wtppm, by using high purity lanthanum trifluoride, the purity can be further improved, either All of them meet the conditions of the invention of the present invention.

Moreover, oxygen and Ca which are not reduced when calcium is reduced can be greatly reduced. In the present embodiment, since the high-purity lanthanum trifluoride of 10 wtppm or less is used as the rare earth element other than cerium, the enthalpy after electron beam melting is similarly 10 wtppm or less.

The tantalum ingot obtained in the above manner was hot pressed as needed, and further mechanically processed and ground to prepare a disk-shaped target of 140 × 14t. The weight of this target was 1.42 kg. Further, it was bonded to a support plate to form a target for sputtering. Thereby, the target for high-purity ruthenium sputtering of the above-mentioned component composition can be obtained. Further, since this target has high oxidizing property, it is preferably stored or transported in a vacuum package.

(Comparative Example 2)

(The EB melts after the commercially available Ca is reduced by the commercially available LaF ₃ )

Lanthanum trifluoride (LaF ₃ ) and commercially available calcium (Ca) were used as raw materials for the treatment.

(calcium reduction)

Next, calcium reduction is performed using commercially available calcium. The melting crucible used in the reduction is made of tantalum (Ta). Powdered LaF ₃ and bulk Ca were mixed into the crucible. Usually, the amount of addition of Ca as a reducing material is about 10% more than the calculated amount.

The filler in the crucible placed in the reduction device was slowly heated to 600 ° C, during which time the inside of the reduction device was suctioned to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further heating is carried out, and if the filler is heated to 800 ° C to 1000 ° C, the reaction is started. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is an exothermic reaction and will end quickly. In order to smoothly separate the purified metal from the slag, it can be maintained at a temperature of about 50 ° C higher than the melting point of the La metal for several minutes.

The yield of the metal La is about 97%. The main impurities are unreacted Raw materials and slag. Further, since the Ta which is a coffin may be mixed in the form of impurities, the reduction reaction should be carried out at a low temperature as much as possible. In this way, the metal La is obtained. The analytical values of the metal La are shown in Table 16.

Among them, the following elements may be mentioned as a large amount of impurities. Na: 0.06 wtppm, Al: 6.2 wtppm, Si: 11 wtppm, S: 19 wtppm, Cl: 1.7 wtppm, Cu: 140 wtppm, Zn: 0.06 wtppm, C: 340 wtppm, N: 120 wtppm, O: 410 wtppm, H: 15 wtppm, containing many The gas composition.

On the other hand, the rare earth element has Ce: 80 wtppm, Pr: 33 wtppm, Nd: 16 wtppm, Sm: 6.8 wtppm, Gd: 10 wtppm, Tb: 11 wtppm, etc., and many impurities.

Next, using an EB melting furnace, melting was performed at a vacuum degree of 7.0 × 10 ^-5 to 3.5 × 10 ^-5 mbar, and a melting output of 32 kW, and an ingot was produced at a casting speed of 45 kg / h. When the electron beam is melted, volatile substances can be volatilized and removed.

A high-purity bismuth ingot of 22.54 kg can be obtained by the above method. The analytical values of the high purity hydrazine obtained in this manner are shown in Table 17.

As shown in Table 17, the main impurity elements in the crucible after electron beam melting were as follows. Al: 8 wtppm, Si: 16 wtppm, S: 20 wtppm, Ca: 2.9 wtppm, Ti: 2.2 wtppm, Cr: 2.1 wtppm, Mn: 1.2 wtppm, Fe: 5.1 wtppm, Cu: 165 wtppm, C: 330 wtppm, N: 110 wtppm, O : 1100 wtppm, H: 20 wtppm.

As is clear from the above, it is not possible to reduce Al, Fe, Cu, and in particular, a large amount of Cu remains. And the reduction in gas composition is also insufficient. Overall, compared with the foregoing embodiments, the amount of impurities is high, and the object of the present invention cannot be achieved.

(Comparative Example 3)

(The EB melts after the low-reliance of LaF _{3 is} reduced by commercially available Ca)

Low RE lanthanum trifluoride (LaF ₃ ) and commercially available calcium (Ca) were used as raw materials for the treatment.

(calcium reduction)

Next, calcium reduction is performed using commercially available calcium. The melting crucible used in the reduction is made of tantalum (Ta). Powdered LaF ₃ and bulk Ca were mixed into the crucible. Usually, the amount of addition of Ca as a reducing material is about 10% more than the calculated amount.

The filler in the crucible placed in the reduction device was slowly heated to 600 ° C, during which time the inside of the reduction device was suctioned to a vacuum to perform degassing of the filler. Then, purified argon gas was fed to form 0.5 atmosphere.

Further heating is carried out, and if the filler is heated to 800 ° C to 1000 ° C, the reaction is started. The reaction formula is 2LaF ₃ +3Ca→2La+3CaF ₂ . This reaction is quickly terminated because it is an exothermic reaction. In order to smoothly separate the purified metal from the slag, it can be maintained at a temperature of about 50 ° C higher than the melting point of the La metal for several minutes.

The yield of the metal La is about 97%. The main impurities are unreacted reducing materials and slag. Further, since the Ta which is a coffin may be mixed in the form of impurities, the reduction reaction should be carried out at a low temperature as much as possible. In this way, the metal La is obtained. The analytical values of the metal La are shown in Table 18.

Among them, the following elements may be mentioned as a large amount of impurities. Al: 3.2 wtppm, Si: 2.1 wtppm, S: 11 wtppm, Ca: 4.4 wtppm, Fe: 0.44 wtppm, Mn: 14 wtppm, Cl: 1.8 wtppm, Cu: 110 wtppm, C: 320 wtppm, N: 85 wtppm, O: 450 wtppm, H: 22 wtppm, containing many gas components.

On the other hand, the rare earth element has Ce: 2.4 wtppm, Pr: 0.16 wtppm, Nd: 0.64 wtppm, and the rest < 0.05 wtppm, which is a low concentration.

Next, using an EB melting furnace, melting was performed at a vacuum degree of 7.0 × 10 ^-5 to 3.5 × 10 ^-5 mbar, and a melting output of 32 kW, and an ingot was produced at a casting speed of 45 kg / h. When the electron beam is melted, volatile substances can be volatilized and removed.

A high-purity bismuth ingot of 22.54 kg can be obtained by the above method. The analytical values of the high purity hydrazine obtained in this manner are shown in Table 19.

As shown in Table 19, the main impurity elements in the crucible after the electron beam melting were as follows. Al: 4.2 wtppm, Si: 1.1 wtppm, S: 9 wtppm, Ti: 1.8 wtppm, Cr: 0.36 wtppm, Mn: 1.7 wtppm, Fe: 0.65 wtppm, Cu: 98 wtppm, C: 420 wtppm, N: 140 wtppm, O: 900 wtppm, H: 13 wtppm.

As is clear from the above, when compared with Comparative Example 2, although the purity is slightly increased, Al, S, Mn, and Cu cannot be lowered, and in particular, a large amount of Cu remains. And the reduction in gas composition is also insufficient. Overall, compared with the foregoing embodiments, the amount of impurities is high, and the object of the present invention cannot be achieved.

It is clear from the comparison between the above examples and the comparative examples that the selection of the raw materials (especially, the selection of rare earth elements and gas components other than cerium, the purity of lanthanum trifluoride having a purity of 4 N or more) is used, and by distillation of calcium The reduction is carried out to produce a ruthenium having a purity of 4 N or more, and then the reduced ruthenium is subjected to electron beam melting, and the step of removing the volatile matter is important, whereby a rare earth element and a gas component other than ruthenium can be produced, High purity 镧 with a purity of 4N or more.

Industrial availability

The high-purity germanium obtained by the present invention, the sputtering target made of high-purity germanium, and the metal gate film containing high-purity germanium as a main component are particularly suitable as an electronic material disposed close to the germanium substrate, since it is not lowered or disturbed. The function of the electronic device is therefore suitable as a material for a gate insulating film or a film for a metal gate.

Claims (10)

A method for producing a high-purity lanthanum having a purity of 4N5 or more, a purity of 4N5 or more, a purity of 4N5 or more, a Cu content of 1 wtppm or less, and a total gas component of 1000 wtppm or less. The rare earth element and the gas component other than ruthenium are reduced by a rare earth element and a gas component other than ruthenium, and the ruthenium trifluoride raw material having a purity of 4N or more is reduced to produce a ruthenium having a purity of 4N or more, and the reduced ruthenium is subjected to electron beam melting. , remove volatile substances. A method for producing a high-purity lanthanum having a purity of 4N5 or more excluding a gas component and having Al and Fe at 5 wtppm or less, Cu at 1 wtppm or less, and a total gas component of 1000 wtppm or less, by distillation of calcium The gas component and the ruthenium trifluoride raw material having a purity of 4 N or more are reduced to produce a ruthenium having a purity of 4 N or more, and the reduced ruthenium is subjected to electron beam melting to remove the volatile matter. A method for producing a high-purity lanthanum according to claim 1 or 2, which has a C of 200 wtppm or less. A method for producing a high-purity lanthanum according to claim 1 or 2, wherein the total amount of the rare earth element other than cerium is 10 wtppm or less. A high-purity lanthanum, excluding rare earth elements and gas components other than cerium, having a purity of 4 N5 or more, Al and Fe of 5 wtppm or less, Cu of 1 wtppm or less, and a total gas component of 1000 wtppm or less. For example, the high purity hydrazine of claim 5, wherein C is below 200 wtppm. For example, the high purity 镧 of the fifth or sixth patent application scope, The total amount of rare earth elements is below 10 wtppm. A sputtering target is produced using the high purity hydrazine of any one of claims 5 to 7. A metal gate film is formed using a sputtering target of claim 8 of the patent application. A semiconductor device and device comprising the metal gate film of claim 9th.