JPH0891932A - High-density aluminum fluoride sintered compact and its production - Google Patents

Abstract

PURPOSE: To obtain a new raw material usable as various structural members, having suitable high corrosion resistance, especially also as a member of a derive for producing semiconductors and having low dust-generating property. CONSTITUTION: The characteristics of this high-density aluminum fluoride sintered compact are to have >=90% relative density and <=100ppm content (based on element) of impurities other than oxygen. The aluminum fluoride sintered compact having >=90% relative density is produced by (1) a step for preparing aluminum raw material powder having 0.1-100μm particle size distribution, (2) a step for forming the aluminum fluoride raw material powder and (3) a sintering step for sintering the resultant formed body at 900-1500 deg.C under pressure of an inert gas atmosphere. In this time, the pressure sintering is preferably carried out by a hot press method or hot isostatic press method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-density aluminum fluoride sintered body and a method for manufacturing the same, and more particularly to a chamber, bell jar, and susceptor of an apparatus used in a CVD process or a dry etching process in a semiconductor manufacturing process. The present invention relates to a high-purity, high-density aluminum fluoride sintered body suitable for various structural members such as a clamp ring, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In a semiconductor manufacturing process, for periodic self-cleaning for removing film components attached to other than a wafer of a CVD apparatus for forming an oxide film and a metal film of wiring on a silicon wafer by CVD, CVD by thermal etching of etching equipment or plasma etching
NF ₃ , which is highly corrosive, to remove the film formed in
Fluorine-based gas such as CF ₄ and ClF ₃ is used. Use under severe conditions such as these highly corrosive gases, for example,
Conventionally, components such as a bell jar, a chamber, a susceptor, a clamp ring, and a focus ring are semiconductors such as silicon (Si) and aluminum (Al).
Quartz glass, silicon carbide, etc. have been selectively applied according to the application. However, there are various problems in various materials that have been conventionally used. For example, quartz glass is widely used in semiconductor manufacturing equipment because it is possible to obtain a high-purity member, and because it is composed of the same element as the silicon of the wafer to be manufactured, it is highly reactive fluorine-based gas. In the presence of the above, since the vapor pressure of the reaction product compound such as silicon fluoride is high and vaporizes as a gas, corrosion may proceed continuously and the member may disappear. Further, silicon carbide is basically superior in corrosion resistance to quartz glass, but since silicon carbide used for semiconductor manufacturing equipment is mainly silicon-impregnated silicon carbide, the silicon part has the same fluorine content as quartz glass. Since it disappears due to the reaction with the system gas, the structural structure is coarsened and silicon carbide is easily released from the equipment, which causes particles.

[0003]

On the other hand, aluminum-based materials such as aluminum (metal), aluminum oxide (alumina), and aluminum nitride are produced by reacting with a fluorine-based gas, as compared with the above-mentioned quartz glass and silicon carbide. Aluminum fluoride (AlF ₃ ) has a vapor pressure remarkably lower than that of silicon fluoride, and its use has been attempted. Further, in aluminum-based materials, there is a difference in corrosion rate depending on the type. For example, comparing a metal system and a ceramic system, a metal system having low interatomic bond strength has low corrosion resistance, and a ceramic system having high bond strength has high corrosion resistance. The ceramic aluminum, becomes a difference in thermal expansion problems between the product AlF ₃ the type of ceramic material, when subjected to heat history, depending on its kind, AlF ₃ ceramic substrate
May peel off and become particles. As described above, AlF ₃ having a low vapor pressure is generated, and even aluminum-based materials that are expected to be applied have to wait for further improvement as a constituent member of a semiconductor manufacturing apparatus that is exposed to a fluorine-based gas. is there.

In view of the above situation, the inventors have conducted extensive studies for the purpose of developing a material having high corrosion resistance and low dust generation suitable as a constituent member of a semiconductor manufacturing apparatus under severe conditions. AlF ₃ itself, which is a product of the above aluminum-based material surface, is applied to the constituent members,
Raw material AlF _{3 having} a purity applicable to the constituent members of the apparatus for the CVD process and the dry etching process for the semiconductor manufacturing exposed to the fluorine-based gas, the molding of the raw material powder, and the molded product of AlF ₃ single-phase polycrystal As a result of further various studies such as the production of an AlF ₃ sintered body composed of Up to now, efforts have been made to improve the corrosion resistance by improving conventionally known ceramic materials, but the present invention has not been studied as a raw material for the constituent members.
It was made with the intention of using F ₃ itself as a raw material and making it a raw material applicable to semiconductor manufacturing equipment members. In particular, AlF ₃ has characteristics that cannot be handled in the same way as conventional raw materials, such as sublimation without being melted by heating, and therefore, its advantages can be utilized and an AlF ₃ sintered body, particularly semiconductor manufacturing, can be used efficiently and effectively. Device member A
It forms an IF ₃ sintered body.

[0005]

According to the present invention, a high-density aluminum fluoride sintered body having a relative density of 90% or more and an impurity content other than oxygen of 100 ppm or less on an elemental basis. The body is provided. Furthermore, (1)
A step of preparing an aluminum fluoride raw material powder having a particle size distribution of 0.1 to 100 μm, (2) a step of molding the aluminum fluoride raw material powder, and (3) a molded body in an inert gas atmosphere at 900 to 1500 ° C. The method for producing a high-density aluminum fluoride sintered body is characterized by comprising a sintering step of pressure-calcining and sintering, and the relative density of the obtained sintered body is 90% or more. Provided. The pressing in the sintering step in the present invention is preferably performed by a hot pressing method or a hot isostatic pressing method. Further, it is preferable to use, as the raw material powder, high-purity aluminum fluoride powder having a total amount of impurities of 50 ppm or less on an elemental basis except oxygen. Furthermore, the purity of the high-density aluminum fluoride sintered body of the present invention is preferably 99.99% or more.

[0006]

The present invention is configured as described above, the content of impurities is reduced by using synthetic aluminum fluoride as the raw material powder, and the melting method of the polycrystalline body is avoided because of the characteristics of aluminum fluoride which easily sublime. By sintering at a temperature lower than the sublimation temperature, an aluminum fluoride sintered body having a relative density of 90% or more and impurities other than oxygen of 100 ppm or less on an elemental basis can be effectively obtained. In addition, since aluminum fluoride raw material powder is molded and subjected to pressure heating and sintering by hot pressing (HP) or hot isostatic pressing (HIP), each raw material powder particle is in a dense state and has a driving force for sintering. Become. Further, sublimation is suppressed even in a high temperature range of 900 to 1500 ° C., sintering is efficiently performed, and a sintered body having a relative density of 90% or more can be obtained. Further, as the raw material powder, high-purity aluminum fluoride, especially when the content of impurities on the elemental basis is 50 ppm, the aluminum fluoride sintered body obtained is 99.
It has a high purity of 99% or more, has high corrosion resistance to corrosive gases, particularly fluorine-based gas and its plasma, has low dust generation, does not contaminate semiconductor wafers, and is suitable as a constituent member of a semiconductor manufacturing apparatus. .

The present invention will be described in detail below.
The aluminum fluoride (AlF that constitutes the sintered body of the present invention
₃ ) itself is extremely stable, is generally well known as a fluorine compound of aluminum having excellent corrosion resistance, strong resistance to corrosion by acids and alkalis, etc., and also having high heat resistance and high thermal shock resistance. Conventionally, ore cryolite naturally produced as a fluorine compound of aluminum (cryoli)
te) (Na ₃ AlF ₆ ) is used as an enamel, an emulsifying agent for broth, and a melting agent for aluminum scouring.
AlF ₃ is industrially produced by eutectic melting of the cryolite and aluminum sulfate and then washing with water to remove the sodium content contained in the crystal structure. Also, in general,
It is also known that aluminum fluoride is produced by the reaction between metallic aluminum and hydrogen fluoride or silicon tetrafluoride, or the heat treatment of alumina and hydrofluoric acid.

However, the inventors have found that AlF ₃ produced from the above-mentioned conventional cryolite is iron (Fe), sodium (Na), calcium (Ca), nickel (N).
i), CV of a semiconductor manufacturing apparatus that contains a large amount of impurity elements such as silicon (Si), so that pollution is strictly limited.
In terms of purity, it is insufficient to be used as a raw material for an aluminum fluoride sintered body for forming various constituent members such as chambers, bell jars, susceptors, and clamp rings in the D step and dry etching step, and the above-mentioned metallic aluminum. It was found that AlF ₃ obtained by the reaction of hydrogen fluoride or silicon tetrafluoride or the heat treatment of alumina and hydrofluoric acid is suitable. Further, as the raw material powder for molding,
Those having a particle size distribution of 0.1 to 100 μm are preferable. This is because if the particle size distribution of the raw material powder is outside the above range, the material powder will not be sufficiently densified. In the method for producing AlF ₃ described above and below, it is preferable to adjust the above particle size distribution by controlling various production conditions in the production process. If the particle size distribution cannot be adjusted even by controlling the production conditions, the obtained AlF ₃ product is suppressed as much as possible by mixing impurities, and the particle size distribution is adjusted to the above range by a treatment such as pulverization. It is preferable to use it.

Furthermore, in the present invention, high-purity AlF ₃ having a total amount of impurities of 50 ppm or less on the basis of elements is further used.
Can be produced and the high-purity AlF ₃ can be used.
As a method for producing this high-purity AlF ₃ , in particular, the AlF ₃ obtained by the above-mentioned conventional method of the method found by the inventors.
In a non-oxidizing gas atmosphere containing hydrogen chloride, for example, at least one gas selected from hydrogen, nitrogen, argon and helium, or at least one gas selected from nitrogen, argon and helium and hydrogen. In a contained non-oxidizing gas atmosphere, preferably heat sublimation treatment is performed at 950 ° C. or higher and Al is added to a low temperature portion of 300 to 600 ° C.
By the method of re-aggregating F ₃ , the content of impurities other than oxygen produced was 50 ppm or less based on the element, and the purity of A was high.
it is preferable to use a lF _3. In this case, the heat sublimation treatment is carried out by adding about 0.5 hydrogen chloride to the non-oxidizing gas atmosphere.
It is preferable to carry out by containing at least 1.0% by volume, preferably at least 1.0% by volume. More preferably, 2 of at least one gas selected from nitrogen, argon and helium and hydrogen is used.
Hydrogen chloride was added to the mixed gas of 0.
It is preferably carried out in a non-oxidizing gas atmosphere containing 5% by volume or more.

In the present invention, the raw material powder having a relatively high purity and a particle size distribution of 0.1 to 100 μm is used to form a desired shape. For the molding, any of various known molding methods such as press molding such as uniaxial pressing and isostatic pressing, injection molding, extrusion molding, and casting molding may be used. It is preferable to perform press molding. This is because the pressure sintering in the next step becomes smoother. In the molding of the present invention, a solvent as a lubricant or a binder for imparting strength to the molded body can be added. As the solvent, water and alcohols can be used, but since AlF ₃ dissolves in water in an amount of about 5% by weight, alcohols are preferable, and as the binder,
Although various known organic substances can be used, it is preferable to use those which are volatile at low temperature and do not leave a residue, such as polyvinyl butyral. When these organic binders are added, they are heat-treated and degreased in an inert atmosphere before firing in the next step.

The molded body obtained in the above molding step and degreased if necessary is then fired under pressure to form a sintered body. Firing of the present invention, nitrogen, under an inert gas atmosphere such as argon,
A sintered body can be obtained by performing the treatment under pressure at 900 to 1500 ° C. This is because the inert gas atmosphere suppresses the oxidation of AlF ₃ . Also, the firing temperature is 900 ° C
If less than 1, the densification is insufficient, while 1500 ° C
It is because sublimation becomes remarkable when the value exceeds. The pressure firing in the sintering step of the present invention is preferably performed by a hot press (HP) method and a hot isostatic press (HIP) method. In these HP method and HIP method, a molded body is placed in a mold having a predetermined shape and heated and pressed, and the molded raw material AlF ₃ particles can be heated while being pressed in a more dense state. . Therefore, in the sintering process under pressure of the present invention, it is possible to further densify the AlF ₃ particles and to provide a driving force for smoothly proceeding the sintering at a relatively low temperature with a low vapor pressure. Further, in the high temperature range of the above heating temperature range, AlF ₃ sublimation may occur,
Suppressing them while densifying them allows the sintering to proceed smoothly.

AlF of the present invention obtained as described above
_{The 3} sintered body has a relative density of 90% or more, and can be formed to 99.5% or more by the HP method if necessary, and has high mechanical strength in addition to the high corrosion resistance of AlF ₃ itself. Therefore, it is suitable as a precision structural member. Also,
By appropriately selecting the purity of the AlF ₃ raw material powder, it is possible to obtain an AlF ₃ sintered body in which impurities other than oxygen are 100 ppm or less on the elemental basis, and further, the purity is 95% or more. Therefore, the AlF ₃ sintered body of the present invention is suitable as a semiconductor manufacturing apparatus member that severely limits contamination. In particular, when using a high-purity AlF ₃ raw material powder having an impurity content of 50 ppm or less on the elemental basis, the obtained sintered body also has a higher purity, and is excellent even with a corrosive fluorine-based gas. Corrosion resistance is exhibited, and dust generation is significantly reduced, which is suitable for a constituent member of a CVD apparatus or an etching apparatus of a semiconductor manufacturing apparatus. Also, the obtained AlF ₃ sintered body is
It can be used after being appropriately processed into a shape according to its application.

[0013]

EXAMPLES The present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples. Example 1 As shown in FIG. 1, inner diameter 150 mm, length 1500 mm
An electric furnace was constructed by arranging heaters 2, 3 and 4 which can be controlled by three systems in the furnace core tube 1. In the electric furnace configured as described above, the temperatures of the sublimation part X and the low temperature part Y can be independently controlled, and the soaking section length corresponding to the sublimation part X in the central portion is approximately 300.
mm, and the low temperature part Y for agglomerating AlF ₃ at the end of the core tube
Are formed. Using the electric furnace configured as described above, the temperature of the sublimation part X is 1000 ° C. and the low temperature part Y is
Temperature of 450 ° C., the atmosphere in the furnace was nitrogen gas, and the sublimation part was prepared by eutectic melting of cryolite and aluminum sulfate by a conventional method and washing with water to obtain a particle size distribution of 10 to 100 μm.
AlF ₃ powder (manufactured by Kanto Kagaku Co., Ltd.) having a particle size of m and an average particle diameter of 50 μm was placed as a starting material, and sublimated and reaggregated to obtain highly purified AlF ₃ powder. The impurity content of the obtained high-purity AlF ₃ powder is shown in Table 1 as a raw material. To 100 g of raw AlF ₃ powder having a particle size distribution of 3 to 50 μm and an average particle diameter of 12 μm obtained by high purification as described above, 1% by weight of polyvinyl butyral as a binder and 100 ml of isopropyl alcohol as a solvent were added, The mixture was stirred and mixed in a ball mill for about 1 hour. The obtained mixture was dried at 70 ° C., the solvent was removed, and the mixture was passed through a # 60 sieve to obtain a granule. Using the obtained granule, uniaxial pressure molding was performed at 30 MPa into a cylindrical shape of 20 mmφ, and CIP molding was further performed at 100 MPa. HP of the obtained compact at 1000 ° C. and 60 MPa
Sintered. For the obtained sintered body, cut out a sample,
The chemical analysis was performed to measure the content of impurities, the density was measured using the Archimedes method, and the relative density was calculated. The results are shown in Table 1.

[0014]

[Table 1]

Example 2 Using the same furnace as in Example 1, a high-purity AlF ₃ powder was obtained in the same manner as in Example 1 except that the atmosphere in the furnace was 2% by volume of hydrogen chloride gas and the balance was nitrogen gas. It was High purity A obtained
The amount of impurities in the 1F ₃ powder is shown in Table 1 as a raw material. Using the above high-purity AlF ₃ powder, an AlF ₃ sintered body was obtained in exactly the same manner as in Example 1. Using a sample cut out from the obtained sintered body, the impurity content and the relative density were measured in the same manner, and the results are shown in Table 1.

Example 3 As Example 1, except that the same furnace as in Example 1 was used, the atmosphere in the furnace was 2% by volume of hydrogen chloride gas, and the balance was 1: 1 mixed gas of nitrogen gas and hydrogen gas. Similarly, high purity AlF ₃
A powder was obtained. The amount of impurities in the obtained high-purity AlF ₃ powder is shown in Table 1 as a raw material. Using the above high-purity AlF ₃ powder, an AlF ₃ sintered body was obtained in exactly the same manner as in Example 1.
Using the sample cut out from the obtained sintered body, the impurity content and the relative density were measured in the same manner, and the results are shown in Table 1.

Comparative Example 1 Particle size distribution 10 to 10 obtained by eutectic melting of cryolite and aluminum sulfate used as starting materials in Example 1 and washing with water
AlF ₃ powder (manufactured by Kanto Chemical Co., Inc.) having a particle size of 0 μm and an average particle size of 50 μm was used as a raw material powder as it was. The amount of impurities in this raw material AlF ₃ powder is shown in Table 1. Raw material Al
The F ₃ powder to obtain AlF ₃ sintered body in the same manner as in Example 1. Using the sample cut out from the obtained sintered body, the impurity content and the relative density were measured in the same manner, and the results are shown in Table 1.

As is clear from the above Examples and Comparative Examples, AlF ₃ produced from cryogenic natural ore, although the density characteristics of the obtained sintered body are equivalent to those of the present invention,
It can be seen that the content of impurities is not suitable for a semiconductor manufacturing apparatus, as compared with the one using highly purified AlF ₃ .

Examples 4 to 7 and Comparative Examples 2 to 5 The compacts obtained in the same manner as in Example 2 were set in the carbon pressure mold shown in FIG. 2 and heated under 60 MPa pressure to sinter HP. Sintering, HP sintering, the sintered body obtained by further heating the sintered body under a pressure of 150 MPa using argon gas as a pressure medium to sinter, and heating and firing while circulating argon gas in a carbon crucible. 900 to 1300 shown in Table 2 by using three types of pressureless (NP) sintering for binding.
It was heated to a temperature of ℃ to obtain a sintered body. The carbon mold of FIG. 2 has a carbon spacer 12 and an upper punch 1 which are arranged on the inner circumference of a mold 11 having a carbon peripheral wall.
The space S surrounded by the lower punch 3 and the lower punch 14 is filled with the forming raw material powder F via the spacers 15, respectively. After the molding raw material powder F is filled, it is pressed by the upper and lower punches 13 and 14 while being heated by a high frequency, and is sintered. As the HP sintered body used for the HIP sintering of Example 7, the sintered body obtained in Example 2 was used. A sample was cut out from each of the obtained sintered bodies and the relative density was measured in the same manner as in Example 1. The results are shown in Table 2.

[0020]

[Table 2]

From the above Examples and Comparative Examples, it can be seen that if the HP sintering temperature is lower than 900 ° C., a relative density of 90% or more cannot be obtained. Further, it is also understood that a sufficient relative density cannot be obtained without pressure sintering.

[0022]

The aluminum fluoride sintered body produced according to the present invention has a high density and high strength, has a small content of impurities, and does not become a source of contamination on semiconductor wafers. It can be suitably used as a constituent member.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of an electric furnace used in an example of the present invention.

FIG. 2 is a structural explanatory view of a HP sintering mold used in one example of the present invention.

[Explanation of symbols]

 1 Furnace Core Tube 2, 3, 4 Heater X Sublimation Part Y Low Temperature Part 11 Mold 12 Spacer 13 Upper Punch 14 Lower Punch 15 Spacer S Space Part F Raw Material Powder

Front Page Continuation (72) Inventor Shigeko Sugiyama 30 Soya, Hadano, Kanagawa Prefecture Toshiba Ceramics Co., Ltd.

Claims (5)

[Claims] 1. A high-density aluminum fluoride sintered body having a relative density of 90% or more and an impurity content other than oxygen of 100 ppm or less on an elemental basis. 2. (1) A step of preparing an aluminum fluoride raw material powder having a particle size distribution of 0.1 to 100 μm, (2) a step of molding the aluminum fluoride raw material powder, and
(3) 900-1500 moldings in an inert gas atmosphere
It is configured to have a sintering step of sintering by pressurizing and firing at ℃,
A method for producing a high-density aluminum fluoride sintered body, characterized in that the relative density of the obtained sintered body is 90% or more. 3. The method for producing a high-density aluminum fluoride sintered body according to claim 2, wherein the pressing in the sintering step is performed by a hot pressing method or a hot isostatic pressing method. 4. The method for producing a high-density aluminum fluoride sintered body according to claim 2, wherein the raw material powder is high-purity aluminum fluoride having a total content of 50 ppm or less on an element basis except for oxygen. 5. The method for producing a high-density aluminum fluoride sintered body according to claim 2, 3 or 4, wherein the sintered body has a purity of 95% or more.