JP2006151777A - Ceramic-metal compound material, its forming process, and conductive member using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that cracking and crazing heretofore produced in a ceramic-metal composite material completed by rapid shrinkage of the metal in its cooling process after porous ceramic is impregnated under pressurization with the molten metal in the ceramic-metal composite material used mainly for semiconductor and liquid crystal production processes etc. <P>SOLUTION: The ceramic-metal composite material having the metal in the pores of the porous ceramic composed of silicon nitride is characterized in that crystal particles of the silicon nitride at the boundary surfaces of the porous ceramic and the metal are bonded to each other via the metal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a composite of porous ceramics and metal mainly used in stages such as etching apparatuses and exposure apparatuses for manufacturing semiconductors and liquid crystals, various electrodes, wafer holding mechanisms, and the like. The present invention relates to a ceramic-composite using aluminum or an alloy containing the same and a method for producing the same.

  Various thin film forming devices, cleaning devices, heat treatment devices, etc. used in semiconductor manufacturing often use fluorine-based, chlorine-based and other corrosive gases, and various types exhibiting good corrosion resistance against these corrosive gases. These ceramics have been widely used. However, since ceramics are inferior to metals in terms of thermal conductivity and fracture toughness compared to metals that have been used in the past, attempts have recently been made to use ceramics and metal composites. It is coming.

  Recently, for the purpose of imparting conductivity and improving properties such as heat dissipation and fracture toughness, production of ceramic-metal composites in which various porous metals are impregnated with various pressures has been carried out. ing.

  Various ceramics such as alumina, silicon carbide, silicon nitride, and aluminum nitride are applied as the material of the porous ceramics used for manufacturing such a ceramic-metal composite, and the ceramic-metal composite is used. It is properly used according to the environment.

  Among these materials, ceramics made of silicon nitride, in particular, have the advantage of having excellent properties of high strength and high hardness because the atomic bonding state has both covalent bonds and ionic bonds. Low fracture toughness has become a problem, and attempts have been made to obtain high fracture toughness by combining ceramics and metal and imparting metal properties that are easily plastically deformed. .

  For example, in Patent Document 1, a sintering aid made of rare earth metal oxide is added to silicon nitride powder having an average particle size of 1 μm or less, and a temperature of 1550 to 1800 ° C. in an inert atmosphere. To form porous ceramics made of silicon nitride having a closed porosity of 2% by volume or less, an open porosity of 10 to 65% by volume, a β silicon nitride columnar crystal minor axis of 1 μm or less, and an aspect ratio of 5 or more. And the manufacturing method of the silicon nitride ceramic matrix composite material which press-fits the molten metal to this is disclosed.

Further, Patent Document 2 discloses a metal-ceramic composite material obtained by pressure impregnating a molten metal serving as a matrix into pores of a porous ceramic sintered body having a pore diameter of 7 to 50 μm and cooling, and production thereof. A method is disclosed.
Japanese Patent No. 3287202 JP 2000-336438 A

  However, in Patent Document 1, since a large amount of 5-15% by weight of a sintering aid made of a rare earth metal oxide is added to silicon nitride powder, porous ceramics made of silicon nitride are affected by this effect. Try to be more precise. Therefore, the porous ceramic produced by heat treatment at a high temperature is a high-strength porous ceramic having a three-dimensional network structure in which a contact portion between silicon nitride crystals, a so-called neck portion, grows due to the influence of the sintering aid. However, after impregnating the molten metal, a great stress is applied to the neck portion, which is a contact portion between the silicon nitride crystals, due to the rapid shrinkage of the metal in the cooling step, and the strength thereof is low. There was a problem that a crack occurred from the part and eventually it was damaged.

  That is, usually, when producing the porous ceramics, a silicon nitride powder is mixed with a sintering aid and a binder to produce a mixed powder, and the mixed powder is put into a predetermined mold, After obtaining a molded body by pressure molding, the molded body is heated and sintered to produce porous ceramics. By adding the sintering aid, the sintering aid is made porous. This serves as a binder for strongly bonding the columnar crystals of silicon nitride constituting the porous ceramic to each other. For this reason, when the porous ceramic is impregnated with a molten metal and cooled, In the cooling step, when stress is generated in the columnar crystals due to shrinkage due to cooling of a metal having a larger coefficient of thermal expansion than silicon nitride, the contact portion where the columnar crystals are bonded to each other is firmly fixed. Another strength cracks or breakage occurs in the weaker portion of it had become a cause for generating defects during the manufacturing process.

  Further, in Patent Document 2, a porous ceramic having a relatively large pore diameter of 7 to 50 μm is impregnated with a metal having a high metal impregnation rate and sufficient heat conductivity to impregnate a molten metal. In the cooling step after impregnation of the molten metal as described above, the strength of the crystal particles is affected by the stress generated at the contact portion of the crystal particles constituting the porous ceramics due to rapid contraction in the same manner as described above. There was a problem that the weak part could not endure and the resulting ceramic-metal composite was damaged.

  In the present invention, for such a problem, the stress generated at the contact portion of the columnar crystal constituting the porous ceramic due to the rapid shrinkage in the cooling process after impregnating the molten metal into the porous ceramic made of silicon nitride. An object of the present invention is to provide a ceramic-metal composite that can be relaxed and is not damaged.

  In view of the above problems, the present invention provides a ceramic-metal composite having a metal in pores of porous ceramics made of silicon nitride, wherein the silicon nitride crystal particles at the interface between the porous ceramics and the metal are It is characterized by being connected through a metal.

  Further, the metal is made of aluminum or an alloy containing aluminum.

  Furthermore, the metal is 30 to 50% by volume.

  Furthermore, it is a method for producing a ceramic-metal composite having a metal in the pores of porous ceramics made of silicon nitride, which comprises a binder (not including a sintering aid) or binder and pore-forming agent in silicon nitride powder. A first step of obtaining a mixed powder, a second step of charging the mixed powder into a predetermined mold and pressure forming to obtain a molded body, and a non-oxidizing atmosphere of the molded body. Among them, the third step of obtaining porous ceramics by heating and sintering at a temperature of 1600 to 1900 ° C. and the porous ceramics made of silicon nitride are placed in a pressure-resistant container in which a heat storage body is laid at the bottom, The method comprises a fourth step of impregnating molten metal in the pores with pressure or normal pressure and then cooling.

  Furthermore, the ceramic-metal composite is used as a conductive member.

  In the present invention, a ceramic-metal composite having a metal in pores of a porous ceramic made of silicon nitride is obtained by bonding silicon nitride crystal particles at the interface between the porous ceramic and the metal through the metal. Therefore, in manufacturing the ceramic-metal composite, in the cooling step after impregnating the molten metal, the stress applied to the porous ceramic due to the rapid shrinkage of the metal is relieved, and cracks and breakage that occur are reduced. It becomes possible to prevent.

  Hereinafter, embodiments of the present invention will be described.

  The ceramic-metal composite of the present invention has a metal in the pores of a porous ceramic made of silicon nitride, and silicon nitride crystal particles at the boundary surface between the porous ceramic and the metal are bonded together via the metal. It is characterized by that.

  Here, in order for the silicon nitride crystal particles at the interface between the porous ceramics and the metal to bond with each other via the metal, the columnar crystal particles constituting the silicon nitride are firmly bonded by a sintering aid or a binder. It is important to eliminate undue bonds.

  Therefore, when producing the porous ceramics, the produced silicon nitride columnar crystals are fixed by causing some grain growth at the contact portions due to the high temperature during heating and sintering. Becomes a low-strength porous ceramic in which columnar crystals are weakly bonded. Then, by impregnating the melted metal with this porous ceramic under pressure, the fixed portion between the columnar crystals is separated by the pressure of the metal during the pressure impregnation, so that the rapid contraction when the molten metal cools. On the other hand, since each columnar crystal particle can follow the contraction and the generation of stress is slightly suppressed, the weak portion of the columnar crystal is not cracked or broken. As shown in FIG. 1, the ceramic-metal composite thus obtained has a structure in which the periphery of the silicon nitride columnar crystal particles 1 is covered with the metal 2 at the boundary between the porous ceramics and the metal. Thus, the silicon nitride crystal particles 1 at the boundary with the metal 2 are bonded to each other through the metal.

  The structure of the silicon nitride crystal particles 1 bonded to each other at the interface between the porous ceramics and the metal 2 can be confirmed by analyzing by X-ray diffraction. For example, a ceramic-metal composite obtained by pressurizing and impregnating metal 2 into porous ceramics made of silicon nitride formed by adding a conventional sintering aid with higher strength is shown on the X-ray diffraction chart of its surface. When confirmed, a peak of the added sintering aid is observed. In comparison with this, in the X-ray diffraction chart of the surface of the ceramic-metal composite of the present invention, no peak of the sintering aid component is seen. That is, it is composed only of a porous ceramic component and a metal component peak made of silicon nitride, whereby the silicon nitride crystal particles 1 at the boundary surface between the porous ceramic and the metal 2 are bonded together only through the metal. I understand that

  Note that the structure in which the silicon nitride crystal particles 1 are bonded to each other via a metal may be at least the crystal structure at the boundary between the metal 2 and the pores of the porous ceramics. You may have.

  In addition, as a structure in which silicon nitride crystal particles 1 are bonded to each other through a metal 2, a porous ceramic made of silicon nitride, which is a skeleton impregnated with a molten metal 2, is cracked before or during the impregnation. Although the case where breakage arises and the metal 2 is impregnated there and the crystal particles 1 of the breakage part are combined with metal is considered, in the present invention, the form is not included. Furthermore, when the porous ceramics made of silicon nitride are impregnated with the metal 2, some unimpregnated portions may be generated. However, the present invention may have a structure including this.

  Further, as the degree of impregnation of metal 2, it is more preferable that 80% or more of the pores of metal 2 are impregnated with respect to all pores of the porous ceramics made of silicon nitride measured by Archimedes method or the like.

  In the ceramic-metal composite of the present invention, the strength of the porous ceramic made of silicon nitride impregnated with the metal 2 is very low compared to the conventional case. A strength increase of more than double is confirmed. For example, when the strength of the porous ceramic made of silicon nitride is 10 MPa or more when measured in accordance with JIS R1601-1995, the ceramic-metal composite produced using the porous ceramic has a strength of 100 MPa or more. Have

  In the present invention, the produced ceramic-metal composite is less likely to warp. This is because, when a sintering aid is added, porous ceramics made of silicon nitride are formed with higher strength and strength. If the impregnation state of the metal 2 is uneven, for example, a disk-shaped ceramics- In the case of a metal composite, a tensile or compressive force acts on either the front or back surface of the metal 2 due to a sudden contraction of the metal 2 and warps. On the other hand, in the present invention, the crystal particles 1 can follow the contraction of the metal 2 as described above, and warpage is hardly generated in any shape.

  Moreover, the ratio of the metal 2 in the ceramic-metal composite of the present invention may be adjusted according to various purposes as long as it is about 15 to 50% by volume, preferably 30 to 50% by volume, and more preferably 30%. ~ 40% by volume. Thereby, while maintaining the strength of the porous ceramics made of silicon nitride, it is possible to easily obtain pores that communicate with each other so that the metal 2 enters the inside by impregnation, and the impregnated metal makes the ceramic-metal composite itself. The thermal conductivity can be adjusted to 50 W / m · K or more.

The ceramic-metal composite of the present invention preferably has a thermal conductivity of 50 W / m · K or more. Thereby, when a ceramic-metal composite is used as a member of a semiconductor manufacturing apparatus, it can be effectively used as a member having heat dissipation. The thermal conductivity may be measured according to JIS R 1611-1997 by a laser flash method.
Furthermore, the ceramic-metal composite of the present invention preferably has a thermal expansion coefficient of 12 × 10 ⁻⁶ / ° C. or less from room temperature to 400 ° C. However, although the amount of metal increases, the toughness can be increased, but the strength of the structural member is insufficient. In addition, what is necessary is just to measure the said thermal expansion coefficient based on JISR1618-1994 (average linear expansion coefficient measurement).

  In addition, the bending strength of the ceramic-metal composite of the present invention is preferably 500 MPa or more, and cracks that cause breakage are not latent in the ceramic-metal composite structure. When the pressure is lower than 500 MPa, a crack causing low strength is latent in a part of the ceramic-metal composite, and when used as a member to which a load is applied, this is not preferable because it causes damage.

  Furthermore, the porosity of the ceramic-metal composite of the present invention is preferably 3% or less (excluding 0%). If the porosity is higher than 3%, not only the mechanical strength is lowered, but also the characteristics such as the thermal conductivity are lowered. In order to obtain the bending strength of 500 MPa or more, a porosity of 3% or less is required, and in order to obtain a ceramic-metal composite having higher strength and high thermal conductivity, the porosity is set to 1% or less. Is good. The porosity is a value measured by Archimedes method, and the bending strength is a three-point bending strength measured according to JIS R1601-1995.

Furthermore, it is preferable that the electrical resistance of the ceramic-metal composite of the present invention is uniform. If the electrical resistance is not uniform, when this is used as a member for various electrodes, when a current flows through the member, a portion with a high electrical resistance generates heat, and the melting temperature of the metal 2 is reduced. This is because there is a risk of short-circuiting if the value is exceeded. As a preferable resistance value, the volume resistivity is preferably 1 × 10 ⁻⁵ Ω · cm or less. When the volume resistivity is higher than this, the metal is extremely in a part of the cross section. There is a possibility that there are few places composed only of silicon nitride columnar crystals, and it is considered that the resistance is increased due to the influence of that part, and in such a structure, heat is generated when electricity is passed, Eventually, there is a high risk of short-circuiting beyond the melting temperature of metal 2. In addition, the said volume specific resistance is shown by the value when measuring based on JISC2141.

  The ceramic-metal composite of the present invention preferably has a 10-point average roughness Rz of 0.4 to 100 μm on the surface thereof. This is because, in particular, the ceramic-metal composite of the present invention is often used as a conductive member inside a semiconductor manufacturing apparatus or a deposited film forming apparatus, and in such an apparatus, film forming material scattered in the apparatus adheres to the electrode part. However, if this falls onto the product, it causes so-called particles. Therefore, the surface of the ceramic-metal composite of the present invention is set to Rz 0.4 to 100 μm, so that it can be firmly adhered by the anchor effect between the deposited film forming material and the conductive member, and can be prevented from falling. The value of the ten-point average roughness Rz 0.4 to 100 μm is expressed in the range of about 0.1 to 25 μm in terms of the surface roughness Ra.

The specific heat of the ceramic-metal composite of the present invention is preferably in the range of 0.5 × 10 ³ to 1 × 10 ³ J / (kg · K). Specific heat is determined by the ratio of ceramics to metal. In the present invention, a ceramic-metal composite having such specific heat can be obtained when the amount of impregnated metal is in the range of 20 to 50% by volume. The specific heat is a value determined by a laser flash method.

  Further, the ceramic-metal composite of the present invention includes those in which the outer peripheral surface is composed only of the metal 2. The manufacturing method will be described later, but when impregnating the porous ceramics made of silicon nitride with the metal 2, it is placed in a pressure-resistant vessel, and the molten metal is poured into it, pressurized and impregnated, and then cooled. This is because the finished ceramic-metal composite is covered with the entire metal 2 on the outer peripheral surface. By manufacturing the outer peripheral surface covered with the metal 2 in this way, the ceramic-metal composite portion in the metal is directly impacted even if it is dropped during transportation or an impact is applied. There is no damage.

  Furthermore, the ceramic-metal composite according to the present invention includes at least one of P, S, Cl, K, Ca, Cr, Mn, Fe, Ni, Cu, Zn, Ga, Y, Zr, and Mo as inevitable impurities. These elements may be included in a total of 200 ppm or less in terms of oxides. When the elements contain a total of 200 ppm or more in terms of oxides, these serve as a sintering aid, and the porous ceramic made of silicon nitride is not only densified, but this is used as a conductive member for the electrode part. When used in various devices, the element falls on the product as particles and adversely affects its characteristics, which is not preferable. The content of the inevitable impurities can be measured with an ICP emission spectroscopic analyzer.

  Next, the method for producing the ceramic-metal composite of the present invention will be described in detail.

  The method for producing a ceramic-metal composite of the present invention includes a first step of mixing a silicon nitride powder with a binder (not including a sintering aid) or a binder and a pore forming agent to obtain a mixed powder, and the mixing A second step in which a powder is put into a predetermined mold and pressure-molded to obtain a molded body; and the molded body is heated and sintered at a temperature of 1600 to 1900 ° C. in a non-oxidizing atmosphere, and porous ceramics And a porous ceramic made of silicon nitride is placed in a pressure-resistant container having a heat storage body laid on the bottom thereof, and molten aluminum or an alloy containing aluminum is pressurized or normally applied to the pores. And a fourth step of cooling after pressure impregnation.

  Specifically, first, in the first step, a binder of 0.1 to 10% by mass with an external ratio is added to 100% by mass of β silicon nitride powder having an average particle size of 0.1 to 10 μm and an aspect ratio of 2 to 8, Furthermore, after adding 15-50 mass% pore forming agent with respect to silicon nitride powder, this is stirred using a mixing stirrer, and mixed powder is obtained. In addition, about this mixed powder, it is also possible to set it as the mixed powder granulated using spray granulation methods, such as spray drying.

  Here, it consists of mixing a powder mainly composed of β silicon nitride having a particle size of 1 to 10 μm, a binder, and a pore-forming agent, further promoting the grain growth at the contact portion between the above-mentioned silicon nitride columnar crystals, It is important to produce a mixed powder without using a sintering aid as a binder for increasing the strength.

  The pore forming agent added together with the binder to adjust the average pore size of the porous ceramics made of silicon nitride is a resin having a sublimation temperature of 1000 ° C. or less having a particle size equivalent to the desired average pore size. What is necessary is just to mix a system thing with a silicon nitride and a binder. As the pore forming agent, for example, acrylic resin, polystyrene, silicon, wood chips, rice husks, and the like that can be burned out at 1000 ° C. or lower are applicable, and these are also referred to as pore forming agents and burnout agents. Moreover, since an excessive amount of pore forming agent adversely affects the molding in the next step, the amount added is preferably in the range of 15 to 50% by mass with respect to the silicon nitride powder.

  The pore forming agent described above may be used if necessary to produce the porous ceramic of the present invention, and may not be used unless particularly necessary.

  Next, in the second step, the mixed powder obtained in the first step is put into a prepared mold of a predetermined size, and a molded body is obtained by pressure molding. Here, as the pressure molding method, a powder press molding method, a cold isostatic press molding method, or the like can be used. As the molding die, a metal die, a resin die, a rubber die, or the like can be used. Molding can be performed using any type of molding die depending on conditions and the like.

  Next, for the third step, the molded body obtained in the second step is heated at a baking temperature of 1600 to 1900 ° C. in a non-oxidizing gas atmosphere such as nitrogen gas and argon gas in the baking furnace. Sintering to produce a porous ceramic made of silicon nitride. In addition, it is preferable that the porous ceramics made of silicon nitride obtained here have a porosity of 15 to 50%. When the porosity is lower than 15%, the metal is not sufficiently impregnated in the step of impregnating the metal, which will be described later, so that not only the strength is improved but the thermal conductivity does not become a desired value as a member for a semiconductor / liquid crystal manufacturing apparatus . In addition, when the porosity is higher than 50%, the strength of the porous ceramic made of silicon nitride is lower than 10 MPa, and it is later damaged by the applied pressure for impregnating the metal.

Furthermore, the porous ceramics obtained have pores uniformly dispersed in advance, the average pore size is less than 7 μm, and the number of pores having a pore size of 2 μm or less per 100 μm ^{2 of} the surface is 50 or less. It is preferable. If the pores are not uniformly dispersed, when the molten metal is impregnated, no uniform pressure is applied to the surface of the porous ceramics made of silicon nitride. This is because cracks and breakage occur and a good ceramic-metal composite cannot be obtained. The uniform dispersion means a state in which pores exist at a distance of at least a pore diameter. The average pore diameter is preferably less than 7 μm. In the present invention, since a sintering aid is not used during the production of porous ceramics made of silicon nitride, the columnar crystals are fixed by slight grain growth during firing, and maintain a skeleton as a porous sintered body. ing. Therefore, when the average pore diameter is 7 μm or more, the contact portions between the columnar crystals in the porous ceramics made of silicon nitride are extremely reduced. If the number of contact portions supporting the skeleton is small, the strength cannot be maintained. It is. In order to obtain such a structure of porous ceramics made of silicon nitride, it is necessary to keep the number of pores having a pore diameter of 2 μm or less in the porous ceramic surface of 100 μm ^{2 made of} silicon nitride to 50 or less, and more than 50 This is because the number of pores cannot maintain the minimum strength required to maintain the skeleton as a porous ceramic made of silicon nitride. As the minimum strength at which the metal impregnation can be satisfactorily carried out without causing the porous ceramics made of silicon nitride to break apart due to the pressure during the impregnation of the molten metal, 10 MPa when measured in accordance with JIS R1601-1995. The above strength is required.

Incidentally, the pore number pore size 2μm following in the 100 [mu] m ^2, the after the porous ceramic section made of silicon nitride mirror finished, taking tissue photograph 50-1000 times, the following 2μm in this photo 100 [mu] m ² It can be measured by a method of counting the number of pores. More preferably, the average of the measurement results at 10 or more locations is used.

  In the fourth step, the porous ceramic made of silicon nitride obtained in the third step is made of at least a metal having a higher melting temperature than the molten metal impregnated on the inner surface thereof, or a ceramic having poor wettability with the metal. The molten metal is impregnated in the pores of the porous ceramics made of silicon nitride by being set at a predetermined position in the covered pressure-resistant vessel and pressurized. At this time, the applied pressure is preferably 30 to 100 MPa. Further, after pressurization, the molten metal is uniformly impregnated throughout the pores of the porous ceramics made of silicon nitride by holding for 1 minute or more. It becomes possible. In addition, as a time to hold | maintain after the said pressurization, when cost and time reduction of a process are considered, it is more preferable to set it as 1 to 60 minutes.

  In addition, if porous ceramics made of silicon nitride are preheated before impregnation of the molten metal, damage or cracking of the porous ceramics due to thermal shock when the molten metal is put into the pressure resistant container can be prevented. More preferred. Thereafter, it is possible to obtain a ceramic-metal composite by cooling, but it is preferable to naturally cool as the cooling method, and further, the pressure vessel is cooled on a metallic mounting table having high thermal conductivity. Therefore, it is possible to shorten the cooling time.

  In addition, as the metal to be impregnated, general materials such as copper and aluminum may be used. However, workability after impregnation, corrosion resistance to corrosive gas when used as an electrode or the like as a conductive member, and further completion. In view of reducing the weight of the ceramic-metal composite, it is preferable to use aluminum or an alloy containing aluminum. Examples of aluminum or aluminum-containing alloys include pure aluminum (1000 series), aluminum-copper alloys (2000 series), aluminum-manganese alloys (3000 series), and aluminum-silicon alloys (4000) shown in JIS standards. ), Aluminum-magnesium alloy (5000 series), aluminum-magnesium-silicon alloy (6000 series), and aluminum-zinc-magnesium alloy (7000 series) can be applied. If used, it is more preferable to use pure aluminum (JIS standard number: 1080, 1070, 1050, 1100) excellent in corrosion resistance.

  In addition, the porous ceramics made of silicon nitride produced in the third step shrinks with the shrinkage of the impregnated metal until it becomes a ceramic-metal composite after the fourth step. Is preferably 2% or less. Here, the reason why the shrinkage rate is set to 2% or less is that when the shrinkage rate is larger than 2%, the ceramic-metal composite is liable to be cracked or broken easily. In addition, as a measuring method of shrinkage | contraction rate, the average value which measured the outer diameter of the porous ceramics which consist of silicon nitride after completion | finish of a 3rd process, for example, and the ceramic-metal composite body after completion | finish of a 4th process were obtained. Thereafter, this is processed to expose the surface of the porous ceramic outer diameter made of silicon nitride, and the outer diameter is calculated from the average value of the measured values of the outer diameter.

  Furthermore, in the present invention, it is preferable that the metal impregnation rate into the porous ceramics made of silicon nitride is 80% or more after the fourth step. Here, the metal impregnation rate is a value obtained by measuring the porosity of the ceramic-metal composite after impregnation by the Archimedes method and subtracting this value from 100%. The impregnation rate is calculated from the product of the porosity of porous ceramics made of silicon nitride and the specific gravity of the impregnated metal to calculate the weight of the ceramic-metal composite when 100% metal is impregnated in all the pores. It can be calculated by either a method of calculating from the comparison with the weight of the actual ceramics-metal composite after completion of the process or processing.

  In the fourth step, the porous ceramic made of silicon nitride is placed in contact with the bottom of the pressure vessel and impregnated with molten metal. Therefore, the porous ceramic made of silicon nitride is impregnated with the molten metal only from the outer periphery and does not reach the center of the bottom and the vicinity thereof. Furthermore, since heat escapes from the bottom of the pressure vessel, the temperature of the center of the bottom of the porous ceramics made of silicon nitride advances, and the metal is cooled and solidified before the molten metal reaches it. As a method for solving such a problem that the melted metal is not impregnated at the center of the bottom and the vicinity thereof, in the present invention, a heat storage body in which heat is difficult to escape is installed at the bottom of the pressure vessel. As a result, the center and the vicinity of the bottom of the porous ceramics made of silicon nitride can be maintained at the same temperature as the other portions, so that the molten metal can be more satisfactorily impregnated.

  As described above, the ceramic-metal composite of the present invention and the manufacturing method thereof have been described. These can be used as a member for a semiconductor / liquid crystal manufacturing apparatus, for example, as described above as a conductive member. In particular, it is suitably used as a conductive member for a plasma generating electrode mounted on the apparatus or as an internal electrode member for a semiconductor wafer holding apparatus. As another application, it can be used as a high-strength heat-resistant material installed at the top of the internal combustion engine piston, and can be used in various fields.

  In addition, the first to fourth steps have been described as the manufacturing method of the present invention, but the manufacturing method of the present invention is not limited to only these four steps, and appropriately includes another step between these steps. It does not matter.

  Furthermore, it goes without saying that the present invention can be applied to various improvements and modifications as long as they do not depart from the spirit of the invention.

  Examples of the present invention will be described below.

Example 1
Samples of the present invention and a conventional ceramic-metal composite were prepared, the presence or absence of an auxiliary component by X-ray diffraction, the strength of porous ceramics composed of silicon nitride and the strength improvement rate after metal impregnation, warpage, cracks, and damage The test which compares was carried out.

  First, sample No. 1 of the present invention. 1 is produced. A β silicon nitride powder having an average particle size of about 1 μm, 2 wt% of a commercially available binder (PVA) and water are mixed to prepare a slurry, and then spray granulated with a spray dryer to obtain a mixed powder. Thereafter, the mixed powder is filled into a rubber mold and subjected to pressure molding by a cold isostatic pressing method (rubber press) to obtain a molded body.

  And after giving a cutting process to the said molded object, it baked for 3 to 5 hours in the temperature range of 1700-1900 degreeC in a nitrogen gas atmosphere in a baking furnace, and the shape is outer diameter 500mm, thickness 15mm, porcelain As a characteristic, porous ceramics made of silicon nitride having a porosity of 35% and an average pore diameter of 1.5 μm was manufactured. After that, the porous ceramics made of silicon nitride is placed in a pressure vessel of a large press device in which alumina ceramics is laid as a heat storage body at the bottom, and molten aluminum (JIS standard number 1050) is injected to give 50 MPa. Hold for at least 10 minutes in a pressurized state. Thus, the molten aluminum was impregnated in the pores of the porous ceramics made of silicon nitride, and then cooled to room temperature by natural cooling to produce the ceramic-metal composite of the present invention. The ceramic-metal composite of the present invention had a porosity of 0.5% and a thermal conductivity of 80 W / m · K.

Next, as a conventional ceramic-metal composite, Sample No. 2 was made. 5 wt% of Y ₂ O ₃ and ₂ wt% of binder (PVA) are added to and mixed with elongated silicon nitride powder having an average particle diameter of 0.2 μm and an aspect ratio of 10 as a sintering aid, and water is further added to form a slurry. Then, after spray granulation with a spray dryer, it was produced by the same production method as the present invention.

The characteristics of each sample are shown in Table 1.

  As a result, sample No. 1 which is a conventional ceramic-metal composite was obtained. For No. 2, in the cooling step after impregnating with molten aluminum, cracks were first generated on the surface of the end of the sample, and after warping of 2 mm or more was observed, it was divided into two when cooled to room temperature. It was damaged. When the damaged surface was analyzed by X-ray diffraction, in addition to the silicon nitride and aluminum peaks, yttria added as a sintering aid was detected as a compound with other components.

  In comparison with this, Sample No. which is a ceramic-metal composite of the present invention in which no cracks or breakage was observed. From the X-ray diffraction analysis result of one surface, it was confirmed that only peaks of silicon nitride and aluminum were detected. Further, in the SEM observation of the surface, it is observed that the columnar crystals of silicon nitride are bonded to each other in the ceramic-metal composite of the present invention, and such a crystal structure causes breakage or cracking. It was confirmed that it was possible to produce a ceramic-metal composite without any problems.

(Example 2)
Next, a pore-forming agent was added within the scope of the present invention to prepare a ceramic-metal composite in which the average pore diameter and porosity were controlled.

Sample No. 1 of the present invention used in Example 1 was used. Using the same silicon nitride powder as in No. 1, the porous ceramics made of silicon nitride were shaken by changing the average pore diameter and porosity, and a plurality of samples having a shape of φ60 mm × thickness 10 mm were manufactured. Strength measurement was carried out. Thereafter, the sample is impregnated with pure aluminum (JIS standard number 1050) as a metal under pressure to prepare a sample of the ceramic-metal composite of the present invention, and the number of pores of 2 μm or less present per 100 μm ^{2 on the} surface thereof, Check the pore area ratio, strength, thermal conductivity, and thermal expansion coefficient.

  The method for producing the sample is specifically shown below.

  The same silicon nitride powder and binder as in Example 1 and a resin pore-forming agent are added in the amounts shown in Table 2, and mixed with a mixing stirrer to produce a mixed powder. Thereafter, the mixed powder and water are added to a ball mill. The slurry was obtained after 10 to 24 hours of operation. The slurry was put into a spray dryer apparatus and granulated, and the granulated powder was molded into a size capable of obtaining a size of φ60 mm × thickness 10 mm after firing in a press molding apparatus to obtain a molded body. This molded body was put into a degreasing furnace adjusted to a nitrogen atmosphere and degreased at 600 to 1000 ° C., and then fired in a nitrogen atmosphere at a temperature of 1700 to 1900 ° C. for 3 to 5 hours to obtain the silicon nitride of the present invention. A porous ceramic consisting of

  Thereafter, the porous ceramic made of silicon nitride is placed in a pressure vessel of a large press device, heated to a temperature of around 600 ° C., and then molten aluminum (JIS standard number 1050) is put in the pressure vessel. inject. Then, a pressure of 60 MPa is applied to the pressure vessel by a large press, and the pressure is maintained for 10 minutes or more, and after cooling to room temperature (20-30 ° C.) in the pressure vessel, it is taken out and excess aluminum is removed by grinding and polishing. Sample No. of the ceramic-metal composite of the present invention. 3-18 were obtained.

Results of measurement of average pore diameter, porosity and strength of porous ceramics made of silicon nitride and measurement of strength, thermal conductivity, number of pores of 2 μm or less in surface 100 μm ² and pore occupation area ratio after impregnation of metal The results are shown in Table 2.

The average pore diameter of the porous ceramics is measured by the mercury intrusion method, the porosity is measured by the Archimedes method, the strength is a three-point bending strength (measured in accordance with JIS R1601-1995), and the thermal conductivity is the laser flash method. The value measured at. In addition, regarding the number of pores of 2 μm or less in 100 μm ² and the occupied area ratio of pores, after the surface was mirror-finished, a structure photograph of 1000 times of 5 samples was taken by SEM, the numerical value was calculated from this photograph, and the average value Is described.

  From Table 2, sample No. with an average pore diameter of 7 μm or more was obtained. About 16-18, although the value of thermal conductivity was favorable, the intensity | strength fell before and after metal impregnation as a whole. For example, the sample No. 17 and sample no. 10 is compared, sample No. Sample No. 17 has an average pore diameter of 7 μm or more and a total pore surface area of 3 μm with an average pore diameter of less than 7 μm. It becomes smaller than 23. For this reason, the contact area with the impregnated metal decreases, and it is considered that the effect of increasing the strength by the metal impregnation is small.

  In contrast, a sample having an average pore diameter of less than 7 μm has a large strength increasing effect because the contact area between the impregnated metal and the porous ceramic pores is large. In addition, compared to porous ceramics having the same porosity and an average pore diameter of 7 μm or more, it is confirmed that the pores are likely to be dispersed and present in the porous ceramics, so there is less variation in strength. It was.

  In addition, a sample having a relatively small porosity tends to have a low amount of impregnated metal and a low thermal conductivity. Moreover, although the sample with a large porosity has a high thermal conductivity, a tendency to decrease the strength was confirmed.

  Furthermore, the pore size of the porous ceramics made of silicon nitride is equal to or less than the particle size of the added pore forming agent, and the porosity is equal to or less than the added amount of the pore forming agent. The rate was found to depend on the particle size and amount of pore former.

In addition, regarding the number of pores of 2 μm or less in 100 μm ^{2 of the} porous ceramic made of silicon nitride, each sample shows an average value of 5 locations. Regarding 3 to 17, there is little variation in numerical values at five places, and it can be said that the degree of dispersion of pores is good. However, Sample No. with a porosity of 50% or more was shown. In No. 18, this variation was large, and it was confirmed that the pore dispersion tends to be poor.

  In addition to the samples within the scope of the present invention as described above, several samples were added to which a sintering aid outside the scope of the present invention was added. -Various properties as a metal composite could not be evaluated.

(Example 3)
Next, an example in which the ceramic-metal composite of the present invention is applied as a conductive member is shown.

  FIG. 2 is a schematic sectional view showing a general plasma etching apparatus 10.

In this plasma etching apparatus, an electrostatic chuck 14 for attracting and fixing a semiconductor wafer and a support table 13 for supporting the electrostatic chuck 14 are disposed in a processing container 11. A plasma generating upper electrode 15 is installed at the upper part of the processing container, and CF ₄ injected into the processing container 11 from the gas supply nozzle 17 with a lower electrode 13 ′ (not shown) built in the support table 13. Etching gas plasma is formed. Then, etching is performed by the plasma. The exhaust gas in the processing container 11 is exhausted from the exhaust nozzle 16 by an exhaust pump such as a turbo molecular pump connected to the processing container 11.

  When the upper electrode 15 and the lower electrode 13 ′ of the plasma etching apparatus 10 are made of the ceramic-metal composite of the present invention and plasma etching is performed, it has been confirmed that etching can be performed satisfactorily.

  Further, when the ceramic-metal composite member of the present invention was used as the conductive member for the electrostatic chuck 14, it was confirmed that the electrostatic chuck 14 has good adsorption characteristics and is applicable.

It is a schematic diagram which shows the structure | tissue structure of the ceramics-metal composite of this invention. It is a schematic sectional drawing of the plasma etching apparatus which used the ceramic-metal composite_body | complex of this invention as an electrically-conductive member.

Explanation of symbols

1: Columnar crystal 2: Metal 10: Plasma etching apparatus 11: Processing vessel 12: Support member 13: Support table 13 ': Lower electrode 14: Electrostatic chuck 15: Upper electrode 16: Exhaust nozzle 17: Vacuum exhaust nozzle 18: Gas Supply nozzle

Claims (5)

A ceramic-metal composite having a metal in pores of a porous ceramic made of silicon nitride, wherein silicon nitride crystal particles at the boundary surface between the porous ceramic and the metal are bonded together via the metal A ceramic-metal composite characterized by the above. The ceramic-metal composite according to claim 1, wherein the metal is made of aluminum or an alloy containing aluminum. The ceramic-metal composite according to claim 1 or 2, wherein the metal is 30 to 50% by volume. A method for producing a ceramic-metal composite having metal in pores of porous ceramics made of silicon nitride, in which silicon nitride powder is mixed with a binder (not including a sintering aid) or a binder and a pore-forming agent Then, a first step of obtaining a mixed powder, a second step of putting the mixed powder into a predetermined mold and press-molding to obtain a molded body, and the molded body in a non-oxidizing atmosphere 1600 A third step of obtaining porous ceramics by heating and sintering at a temperature of ˜1900 ° C., and placing the porous ceramics made of silicon nitride in a pressure-resistant container laid with a heat storage body at the bottom thereof, And a fourth step in which molten aluminum or an alloy containing aluminum is impregnated under pressure or atmospheric pressure, and then cooled, and then a method for producing a ceramic-metal composite. A conductive member comprising the ceramic-metal composite according to claim 1.

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