JP2005008482A - Yttrium oxide sintered compact and its producing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a Y<SB>2</SB>O<SB>3</SB>sintered compact, which has been developed in order to solve a problem of prior technologies related to the Y<SB>2</SB>O<SB>3</SB>sintered compact; and to provide the Y<SB>2</SB>O<SB>3</SB>sintered compact which is obtained while suppressing an increase in cost by a near net shape technology. <P>SOLUTION: The Y<SB>2</SB>O<SB>3</SB>sintered compact is obtained by preparing slurry by dispersing a Y<SB>2</SB>O<SB>3</SB>raw material having a purity of ≥99 wt.% and an average particle diameter of ≤2 μm into an aqueous solution of radically polymerizable organic monomers or oligomers, then inpouring the obtained slurry in a mold, polymerizing the monomers or oligomers in the slurry in the mold to form a formed body comprising a wet polymer gel-like material containing the Y<SB>2</SB>O<SB>3</SB>raw material, and firing the formed body at 1,710-1,850 °C in a gaseous hydrogen atmosphere. At this time, it is possible to inhibit the increase of viscosity of the slurry by treating the surface of each Y<SB>2</SB>O<SB>3</SB>particle of the raw material powder with a chelating agent or the like. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４２】
調整後のスラリーに重合開始剤として過硫酸アンモニウムを０．０２９ｇ、触媒としてＮ，Ｎ，Ｎ’，Ｎ’−テトラメチルエチレンジアミンを０．０２９ｇ加えた。攪拌と重合の過程は窒素雰囲気で行った。重合開始剤および触媒を混合したスラリーをポリスチレン製角型容器（長さ９０ｍｍ、幅５５ｍｍ、深さ約２０ｍｍ）に流し込んだ。重合反応が十分に進行した４時間後に脱型を行ない、湿潤成形体を得た。
【００４３】
該湿潤成形体は調湿プログラム可能な乾燥機を用いて、５ＲＨ％／日で９０ＲＨ％から６０ＲＨ％まで乾燥した。乾燥後、６００℃で４時間キープして脱脂を行った。
【００４４】
該脱脂体を２００ｍ^３／時間の流量での水素ガス雰囲気にて１７１０℃、１７８０℃、１８５０℃の焼成を行った。焼成後の密度、平均結晶粒径、透光性の有無を表２に示す。
【００４５】
【表２】

【００４６】
（比較例１〜２）
焼成温度を、１６５０℃および１９００℃で焼成したこと以外には、上記実施例１〜３と同様にしてＹ_２Ｏ_３の焼成を行った。その結果を表２に併せて示す。
【００４７】
（比較例３）
原料となるＹ_２Ｏ_３の粉末の表面処理を行わなかったこと以外は、実施例１と同様にして、スラリーを形成した。しかしながら、得られたスラリーは、調整後１分程度で、粘度が上昇し、型への注型が困難となり成形体を得ることができなかった。
【００４８】
以上実施例および比較例の結果から明らかなように、Ｙ_２Ｏ_３の焼成温度を１７１０〜１８５０℃以内とすることによって透光性及び耐プラズマ性の性質が優れた焼結体を得ることができた。また、原料粉末の表面を処理することにより、スラリー粘度上昇をもたらすことなく、ゲルキャスト法に適したセラミックススラリーを得ることができた。
【００４９】
【発明の効果】
以上本発明によれば、半導体製造装置に用いるのに適した優れた特性を有するＹ_２Ｏ_３焼結体を鋳込み成形によって製造することができることが明かとなった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an yttria (Y ₂ O ₃ ) -based sintered body that is optimal as a member for a semiconductor manufacturing apparatus and a method for manufacturing the same.
[0002]
[Prior art]
The Y ₂ O ₃ sintered body is expected to be applied to a semiconductor device member because of its excellent plasma resistance. However, since the Y ₂ O ₃ raw material is expensive, it is difficult to say that it is necessarily fully utilized. Therefore, establishment of a near net shape technique using a Y ₂ O ₃ raw material is desired as a molding method with little loss of raw material powder.
[0003]
A casting method and an injection molding method are known as techniques suitable for near-net shape of complex-shaped products in the molding methods using ceramics developed so far.
[0004]
The cast molding method, which is the near net shape technique, is a method in which a slurry formed using raw material powder is poured into a mold and dried and solidified to obtain a molded body. However, the slurry using Y ₂ O ₃ powder is inferior in stability over time, has a drawback that viscosity increases immediately after the slurry is produced, fluidity is lowered, and casting molding becomes difficult (Patent Document 1). reference). Therefore, until now, casting molding using Y ₂ O ₃ powder has not been performed.
[0005]
Further, both the casting method and the injection molding method have an essential problem that the flow process and the solidification process of the forming raw material cannot be completely separated. That is, as the slurry or melt compound is filled into the mold, the solidification or cooling and solidification occurs from the mold contact surface, so that the solidification time shifts between the surface and the inside of the molded body, resulting in nonuniform filling. Furthermore, conventional molding methods such as the pressure molding method as well as the casting molding method and the injection molding method often cause irregular shape particle orientation and particle size segregation in the flow process, that is, the shape imparting process and the solidification process. Brings shrinkage anisotropy. Overlapping these causes, deformation and cracking occurred in the drying / degreasing process, and the moldable size was limited.
[0006]
As a means for solving this, it is known that the gel cast method is suitable (Patent Document 1).
However, this method is intended to provide a material having no problem in terms of environment and safety by using hydraulic urethane as a gelling component, and as described above, Y ₂ is difficult to cast. It did not solve the conventional problem of applying the O ₃ raw material to casting.
[0007]
Further, Y ₂ O ₃ sintered bodies are conventionally manufactured by atmospheric firing. However, in this atmospheric firing, since it is colored yellow due to contamination from inside the furnace, in order to produce an uncolored sintered body, Y ₂ O ₃ such as high-purity alumina or Y ₂ O ₃ sintered body is used during firing. It is necessary to seal the molded product with a fired body container that does not contaminate, and to fill it with Y ₂ O ₃ filling powder. Therefore, the size of the fired body container is restricted for the firing space, and the volumetric efficiency of the manufacturing equipment is low, and it is inconvenient for mass production.
[0008]
Further, in the air firing of the Y ₂ O ₃ compact, the firing temperature is a maximum of 1700 ° C. due to the heat resistance limitation of the refractory, and the average crystal grain size of the Y ₂ O ₃ sintered body obtained in this firing temperature range is Only those in the range of 5 to 20 μm were obtained. Moreover, since it does not have translucency, the request | requirement which requires translucency was not responded.
[0009]
As described above, it has been difficult to manufacture a Y ₂ O ₃ sintered body as a member for a semiconductor manufacturing apparatus having excellent characteristics while suppressing an increase in cost using the Y ₂ O ₃ raw material powder.
[0010]
[Patent Document 1] JP-A-11-171651 [Patent Document 2] JP-A-6-128033
[Problems to be solved by the invention]
The present invention has been made to solve the problems of the prior art Y ₂ O ₃ sintered body, while suppressing an increase in cost by near net shape technique, excellent Y ₂ O ₃ sintering properties It aims at realizing a body and its manufacturing method.
[0012]
[Means for Solving the Problems]
In the first aspect of the present invention, a Y ₂ O ₃ raw material having a purity of 99% by weight or more and an average particle size of 2 μm or less is dispersed in an organic monomer or oligomer aqueous solution that undergoes radical polymerization to form a slurry, and the resulting slurry is used as a mold. And a monomer or oligomer in the slurry is polymerized in the mold to form a molded product made of a wet polymer gel containing a Y ₂ O ₃ raw material, and the molded product is then placed in a hydrogen gas atmosphere. , And firing at 1710 to 1850 ° C., which is a method for producing a Y ₂ O ₃ sintered body.
[0013]
In the method for producing a Y ₂ O ₃ sintered body according to the first aspect of the present invention, a Y ₂ O ₃ raw material having a purity of 99% by weight or more and an average particle size of 2 μm or less is subjected to a surface treatment. preferable. The surface treatment is particularly preferably a surface treatment with a chelating agent.
[0014]
In the second aspect of the present invention, the bulk density of the Y ₂ O ₃ sintered body is 4.9 g / cm ³ or more, and the average crystal grain size of Y ₂ O _{3 in} the sintered body is 30 to 600 μm. This is a Y ₂ O ₃ sintered body.
[0015]
In the second aspect of the present invention, the Y ₂ O ₃ sintered body preferably has translucency.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The operation of the present invention will be described below.
In gel cast molding, it is possible to completely separate the flow process and the solidification process, that is, the polymerization reaction proceeds uniformly throughout the system after the slurry is sufficiently filled in the mold. The non-uniformity of the particle filling state as seen in casting molding does not appear. For this reason, shrinkage accompanying drying and sintering occurs isotropically, and deformation and cracking can be prevented. Further, by processing the Y ₂ O ₃ raw material surface as a raw material, it is possible to prevent the Y ₂ O ₃ raw material premature gelation of the slurry.
Thus, the present invention uses a gel cast molding, and by employing a Y ₂ O ₃ raw material powder surface-treated, in which a gel cast molding a Y ₂ O ₃ raw material powder.
[0017]
Embodiments of the present invention will be described below.
[0018]
[material]
(Y ₂ O ₃ raw material powder)
The Y ₂ O ₃ raw material powder preferably has a purity of 99% or more. If it is less than 99%, it is not preferable if it is used for a semiconductor device member, because the impurity component adheres to the surface of the semiconductor wafer as a foreign substance, or the semiconductor wafer is contaminated with impurities such as metal.
[0019]
The particle size of the Y ₂ O ₃ raw material powder is preferably 2 μm or less. When the particle size of the Y ₂ O ₃ raw material exceeds 2 μm, the density of the sintered body to be produced is less than 4.9, which is not preferable because the plasma resistance and bending strength are reduced.
[0020]
(Surface treatment agent)
In the present invention, the surface treatment agent is to prevent the Y ₂ O ₃ raw material powder from being thickened in water. As such a surface treatment agent, the surface of the raw material powder is coated with a polymer substance or the like. Among these, a coating agent, a surfactant, a chelating agent, and the like are given, and among these, the chelating agent is most suitable. In the present invention, the mechanism that can prevent the viscosity increase in the slurry of the Y ₂ O ₃ raw material powder by surface treatment with these surface treatment agents is not clear, but the water resistance is improved, and the Y ₂ O ₃ raw material powder and water It is thought that reaction with is suppressed.
[0021]
Examples of the chelating agent include oxyphenols such as catechol and pyrogallol; amino alcohols such as diethanolamine and triethanolamine; oxyacids such as glycolic acid, citric acid, tartaric acid, lactic acid, mandelic acid, malic acid, and hydroxyacrylic acid And lower alkyl or hydroxyalkyl esters thereof such as methyl, ethyl and hydroxyethyl; oxyaldehydes such as glycol aldehyde; polycarboxylic acids such as oxalic acid and malonic acid; amino acids such as glycine and alanine; acetylacetone and benzoylacetone , Β-diketones such as stearoylacetone, stearoylbenzoylmethane, dibenzoylmethane; β-ketones such as acetoacetic acid, propionylacetic acid, benzoylacetic acid and their Examples thereof include alkyl esters such as til, ethyl, n-propyl, isopropyl, n-butyl and tert-butyl. These chelating agents can be used alone or in combination of two or more.
[0022]
Of these chelating agents, glycolic acid, citric acid, tartaric acid, lactic acid, mandelic acid, malic acid, hydroxyacrylic acid and other oxyacids and β-diketones such as acetylacetone are preferably used. In particular, carbonyl compounds having an oxygen atom on α, β and γ carbon atoms, such as α, β and γ-oxy acids, are preferably used.
[0023]
These chelating agents are coated on the surface of the raw material Y ₂ O ₃ raw material powder and then added to the dispersion medium of the slurry to form a slurry. The amount added is Y ₂ O ₃ raw material The range of 0.5-5.0% is preferable with respect to the powder. When this addition amount is less than the above range, the effect of coating the chelating agent is not exhibited, and the increase in viscosity cannot be suppressed. On the other hand, when the coating amount exceeds the above range, an effect commensurate with the increase in the coating amount cannot be expected, which is not economical. The treatment with this chelating agent can be performed by adding the chelating agent to an organic solvent to form a solution, adding this to the Y ₂ O ₃ raw material powder, and drying.
[0024]
(Monomer or oligomer)
As the monomer used in the present invention, a known monomer or oligomer having an unsaturated carbon bond capable of radical polymerization can be used, and in particular, acrylamide and N, N′-methylenebisacrylamide, methacrylic acid, N-hydroxymethyl. It is preferable to use monomers such as acrylamide and ammonium acrylate alone or in a mixture thereof. Furthermore, the present invention may be used as an oligomer in which several molecules of these monomers are combined.
[0025]
The addition amount of the monomer or oligomer is suitably in the range of 10 to 40% with respect to the slurry. When the amount added is less than the above range, even if these monomers or oligomers are polymerized to form a molded product, its strength is not sufficient, handling is difficult, and it is not practical. On the other hand, if the amount added exceeds the above range, the proportion of the polymer in the molded body becomes too large, the porosity of the resulting sintered body increases, and the strength of the sintered body decreases, which is preferable. Absent.
[0026]
(Dispersant)
As the dispersant, polycarboxylic acid, polyacrylic acid, sulfonic acid and the like can be used. In order to obtain a high molded body density, these are preferably 70% or more for the reason that the molded body density is high and firing shrinkage is small, but it is not limited thereto.
[0027]
(Polymerization initiator)
As a polymerization initiator for polymerizing the monomer or oligomer capable of radical polymerization of the present invention, ammonium persulfate or a mixture obtained by adding potassium sulfate thereto, hydrogen peroxide, azobisisobutyronitrile, ferrous ammonium sulfate / ammonium persulfate However, it is not limited to these.
The addition amount of this polymerization initiator is suitably in the range of 0.05 to 5% in the slurry. When the amount of the polymerization initiator is below the above range, there is a problem of sedimentation segregation due to gelation delay.On the other hand, when the amount exceeds the above range, the gel strength is reduced due to the progress of the termination reaction and the gel is nonuniformly solidified. There is a problem and it is not preferable.
[0028]
(Polymerization catalyst)
As the polymerization catalyst, a known radical polymerization catalyst such as tetramethylethylenediamine can be used, but it is not limited thereto.
The addition amount of this polymerization catalyst is suitably in the range of 0.05 to 7% in the slurry. When the amount of the polymerization catalyst is below the above range, there is a problem of sedimentation segregation due to gelation delay. On the other hand, when the amount is above the above range, there is a problem of gel non-uniformity, which is not preferable.
[0029]
(Other additives)
In addition, the additive used for preparing the slurry containing the ceramic powder can also be employed in the present invention. These additives include sintering aids, rheology modifiers, lubricants, antifoaming agents, plasticizers and the like. The amount of these additives added is preferably 20% by weight or less with respect to the ceramic raw material powder.
[0030]
[Production method]
In the manufacturing method of the sintered body of the present embodiment, first, a step of forming a slurry containing Y ₂ O ₃ raw material powder, this slurry is injected into a mold, and a monomer or an oligomer contained in the slurry is polymerized. And a step of forming a sintered body by firing the resulting molded body. Hereinafter, the manufacturing method of the present embodiment will be described in order according to this step.
[0031]
(Slurry creation method)
Creation of the slurry of this Embodiment can be performed as follows. That is, first, a premixed liquid composed of water, a monomer or oligomer, and a dispersant is prepared, and Y ₂ O ₃ raw material powder is added thereto and mixed with a stirrer to make a high-concentration dispersed slurry. Thereafter, a polymerization initiator and a catalyst are added, and defoaming is performed to obtain a slurry for casting. In the defoaming treatment, the gas present in the slurry can be removed by allowing the slurry to stand under reduced pressure.
If oxygen is present during slurry adjustment or pouring, the polymerization reaction is inhibited. Therefore, this step is preferably performed in a nitrogen atmosphere.
[0032]
(Molding method)
While the obtained slurry is in a fluid state, it is poured into a mold. It is preferable to adjust the time until the reaction starts (induction time) so that the polymerization reaction starts after the slurry fills the mold. The induction time can be adjusted by controlling the amount of polymerization initiator and catalyst and the temperature. When the polymerization / crosslinking proceeds sufficiently, the slurry loses fluidity, and the Y ₂ O ₃ raw material is held in the network of the wet polymer gel to form a molded body. Since the molded body cracks when it is dried rapidly, it is preferable to perform humidity-control drying and then degrease.
[0033]
(Type)
As a mold material used in the molding in this step, polymer resin, metal, ceramics, and wood can be used. This mold may be a moisture permeable material or a non-moisture permeable material.
[0034]
(Baking method)
In the present embodiment, the firing temperature of Y ₂ O ₃ is preferably in the range of 1710 to 1850 ° C. Below 1700 ° C., the density of the sintered body is less than 4.9, which is insufficient. On the other hand, if the temperature exceeds 1850 ° C., it is necessary to make the firing furnace material more excellent in heat resistance, but it is not economical because improvement in characteristics commensurate with it cannot be expected.
[0035]
The firing temperature can be arbitrarily selected in the range of 1710 to 1850 ° C., but in the range of 1710 to 1780 ° C., the obtained Y ₂ O ₃ sintered body has an average crystal grain size of less than 30 μm and poor translucency. When the firing temperature exceeds 1780 ° C., the average crystal grain size becomes 30 μm or more and translucency is exhibited. The higher the firing temperature, the larger the average crystal grain size and the higher the translucency. However, the bending strength of the sintered body decreases as the firing temperature increases, and in order to achieve the bending strength of 50 MPa or more required for a semiconductor member, the sintering temperature is 1850 ° C. or less, and the average crystal grain size in that case is 500 μm. It is.
[0036]
The firing time can be selected between 0.5 and 8 hours. When the firing time falls below the above range, the strength is insufficient. On the other hand, if the firing time is longer than this, it is economically inconvenient. Generally, when firing at a low temperature, firing for a long time is required.
[0037]
The Y ₂ O ₃ may be fired in an inert gas atmosphere, but a pure hydrogen atmosphere is most preferable in consideration of economy. By firing in a hydrogen gas atmosphere in the present invention, a Mo base plate or a tungsten heater can be used as a firing furnace material, and firing at 1700 ° C. or higher is possible.
[0038]
[Sintered body]
The Y ₂ O ₃ sintered body produced by the method described in the above embodiment has a bulk density of 4.9 g / cm ³ or more and an average crystal grain size of Y ₂ O _{3 in} the sintered body. 30 to 600 μm. And this sintered compact had translucency, and had the optimal characteristic as a member for semiconductor manufacturing apparatuses.
When the bulk density of the Y ₂ O ₃ sintered body is lower than the above range, the mechanical strength is not sufficient and it is not suitable as a member for a semiconductor manufacturing apparatus.
[0039]
Moreover, when the average crystal grain size of Y ₂ O _{3 in} the Y ₂ O ₃ sintered body is below the above range, the translucency is not sufficient, and the use for the semiconductor manufacturing apparatus is limited. . On the other hand, when the average crystal grain size exceeds the above range, there is a disadvantage in terms of strength reduction, which is not preferable.
[0040]
【Example】
(Examples 1-3)
Y ₂ O ₃ having an average particle diameter of 1.18 μm and 1.2 μm was surface-treated using 3% of a chelating agent with respect to the raw material to obtain a raw material powder.
Using the raw material powder, a slurry raw material was accommodated and mixed in a polyethylene container having a capacity of 250 ml capable of being sealed in accordance with the formulation shown in Table 1 to prepare a slurry. A polycarboxylic acid was used as the dispersant. As the monomer, methacrylamide was used, and as the crosslinking agent, N, N′-methylenebisamide was used. Slurry mixing was performed for 16 hours using a pot mill.
[0041]
[Table 1]

[0042]
0.029 g of ammonium persulfate as a polymerization initiator and 0.029 g of N, N, N ′, N′-tetramethylethylenediamine as a catalyst were added to the adjusted slurry. The process of stirring and polymerization was performed in a nitrogen atmosphere. The slurry in which the polymerization initiator and the catalyst were mixed was poured into a polystyrene square container (length 90 mm, width 55 mm, depth about 20 mm). Demolding was performed 4 hours after the polymerization reaction sufficiently proceeded to obtain a wet molded body.
[0043]
The wet molded body was dried from 90 RH% to 60 RH% at 5 RH% / day using a humidity control programmable dryer. After drying, degreasing was performed by keeping at 600 ° C. for 4 hours.
[0044]
The degreased body was fired at 1710 ° C., 1780 ° C., and 1850 ° C. in a hydrogen gas atmosphere at a flow rate of 200 m ³ / hour. Table 2 shows the density after firing, the average crystal grain size, and the presence or absence of translucency.
[0045]
[Table 2]

[0046]
(Comparative Examples 1-2)
Y ₂ O ₃ was fired in the same manner as in Examples 1 to 3 except that the firing temperature was 1650 ° C. and 1900 ° C. The results are also shown in Table 2.
[0047]
(Comparative Example 3)
A slurry was formed in the same manner as in Example 1, except that the surface treatment of the raw material Y ₂ O ₃ powder was not performed. However, in the obtained slurry, the viscosity increased in about 1 minute after adjustment, and it was difficult to cast into a mold, and a molded product could not be obtained.
[0048]
As is apparent from the results of the examples and comparative examples, a sintered body having excellent translucency and plasma resistance can be obtained by setting the firing temperature of Y ₂ O ₃ within 1710 to 1850 ° C. did it. Further, by treating the surface of the raw material powder, a ceramic slurry suitable for the gel casting method could be obtained without causing an increase in the slurry viscosity.
[0049]
【The invention's effect】
According to the present invention above, it became apparent that can be produced by casting a Y ₂ O ₃ sintered body having excellent properties suitable for use in semiconductor manufacturing equipment.

Claims (5)

A Y ₂ O ₃ raw material having a purity of 99% by weight or more and an average particle diameter of 2 μm or less is dispersed in an organic monomer or oligomer aqueous solution for radical polymerization to form a slurry, and the resulting slurry is poured into a mold, and the monomer in the slurry Alternatively, an oligomer is polymerized in the mold to form a molded body made of a wet polymer gel containing a Y ₂ O ₃ raw material, and then the molded body is fired at 1710 to 1850 ° C. in a hydrogen gas atmosphere. A method for producing a Y ₂ O ₃ sintered body. _{2. The} method for producing a Y ₂ O ₃ sintered body according to claim 1, wherein the Y ₂ O ₃ raw material having a purity of 99% by weight or more and an average particle diameter of 2 μm or less is surface-treated. A method for producing a Y ₂ O ₃ sintered body. The method for producing a Y ₂ O ₃ sintered body according to claim 2, wherein the surface treatment is a surface treatment with a chelating agent. Y ₂ O ₃ bulk density of the sintered body, at 4.9 g / cm ³ or more and an average grain size of _Y 2 _{O 3} in the sintered body, characterized in that it is a 30~600μm _{Y 2} O ₃ sintered body. Y ₂ O ₃ sintered body of claim 4, wherein said Y ₂ O ₃ sintered body has a light-transmitting property.