JP2007254205A - Silicon nitride joined body, its production method and member for semiconductor production apparatus using the joined body - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a silicon nitride hollow joined body having a low coefficient of thermal expansion and high strength, as a member for a semiconductor production apparatus. <P>SOLUTION: In the silicon nitride hollow joined body, a pair of base bodies 1,4 composed of a silicon nitride-based sintered compact containing silicon nitride as a main component, erbium oxide (Er<SB>2</SB>O<SB>3</SB>) and alumina (Al<SB>2</SB>O<SB>3</SB>) are joined through a joining layer containing glass as a main component, fine crystallites of silicon nitride and an Er component. Thereby, the thermal expansion of the member can be suppressed to the utmost, and the deformation of the member caused by heat can be prevented. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a silicon nitride bonded body obtained by bonding silicon nitride sintered bodies to each other using a bonding agent, a method for manufacturing the same, and a member for a semiconductor manufacturing apparatus using the silicon nitride bonded body. The present invention relates to a member applied to a member having a large hollow structure such as a stage for an exposure apparatus.

  In semiconductor manufacturing, there is an increasing demand for wafer surface plates used for polishing of wafer surfaces and stages for semiconductor exposure equipment in order to process more products at once and streamline the process. ing.

  In such an increase in size, the wafer surface plate, stage, etc. do not bend, are less likely to resonate with vibration, are lightweight, have a low coefficient of thermal expansion, and are unlikely to change in shape due to a slight temperature difference. In order to satisfy this requirement, a wafer surface plate and a stage member made of a ceramic structure having a hollow structure are frequently used.

  A large hollow ceramic structure is obtained by, for example, bonding a plate-shaped ceramic sintered body to a container-shaped ceramic sintered body via a bonding agent. However, in such a joining method, when a heavy object is loaded on the surface of a large hollow ceramic structure and moved, the load concentrates only on the engagement point, and the load is repeatedly applied. As a result, there is a possibility that the engagement portion is broken, and when vibration is applied, stress concentration occurs in the engagement portion and the engagement may be loosened.

  From such a problem, a method is used in which the container-shaped ceramic sintered body and the plate-shaped ceramic sintered body are joined and integrated with an inorganic bonding agent.

  In addition, ceramics such as alumina, silicon carbide, and silicon nitride are used as the ceramic sintered body used for the wafer surface plate and stage. In recent years, however, the silicon nitride-based sintered body is lightweight and has a low thermal expansion coefficient. The thing which consists of is used extensively.

As a ceramic structure in which the silicon nitride sintered bodies are bonded to each other, for example, in Patent Document 1, at least one component or more of the sintering aids of the silicon nitride sintered body that is the bonded body is used as a bonding agent. , bonding agent comprising a silicon nitride has been proposed, specifically using the bonding agent was added _Si 3 _{N 4} in _{Y 2 O 3 -Al 2 O 3} -SiO 2 based glass _Y 2 O ₃ , joining silicon nitride sintered bodies using Yb ₂ O ₃ as a sintering aid is shown.

Further, Patent Document 2 discloses that in the bonding agent formed by mixing an oxide of a group 3 element of a periodic table, a silicon oxide, and an aluminum oxide in order to bond a ceramic sintered body, the periodic rule is used. It has been proposed to reduce the thermal expansion coefficient and improve the heat resistance and mechanical properties of the joint by incorporating at least two Group 3 element oxides and containing nitrogen. It is shown that the ceramics are bonded with this bonding agent.
Japanese Patent Laid-Open No. 5-4876 JP 11-278950 A

However, in Patent Document 1, a bonding agent such as Y ₂ O ₃ —Al ₂ O ₃ —SiO ₂ glass or glass having a composition in which silicon nitride is added in advance is used, and these bonding agents have a melting point. It is as high as 1450-1550 ° C. Similarly, in the bonding agent of Patent Document 2, a bonding agent having a melting point of 1200 to 1450 ° C. is lower than that of the conventional one, and the thermal expansion of the bonded body can be reduced, but each component contained in the bonding agent Since the crystal grain size and the SiO ₂ grain size are large, the bonding layer cannot be made high in strength, so that there is a problem that cracks are likely to occur when a thermal stress is generated at the joint.

In addition, when erbium oxide (Er ₂ O ₃ ) is included as a Group 3 element oxide in the bonding agent, erbium oxide constitutes β-Er ₂ Si ₂ O ₇ for heat treatment at a high temperature. Therefore, it is difficult to reduce the thermal expansion of the joint.

  Furthermore, since the thickness of the joint portion is as thick as 40 to 70 μm, it is difficult to make the density of the joint portion uniform, and there is a problem that the joint area ratio after joining is lowered and the joint strength is easily lowered.

The present invention relates to a pair of substrates made of a silicon nitride sintered body containing silicon nitride as a main component and containing erbium oxide (Er ₂ O ₃ ) and alumina (Al ₂ O ₃ ) as a main component. It is characterized in that it is bonded through a bonding layer containing fine crystals and an Er component.

The bonding layer is characterized by containing 5% by mass or less of an Er element in terms of Er ₂ O ₃ .

  Further, the fine crystal of silicon nitride in the bonding layer has an average crystal grain size of 0.2 μm or less.

  Furthermore, the bonding layer has a thickness of 0.5 to 5 μm.

  Further, the semiconductor manufacturing apparatus member is made of the silicon nitride bonded body, wherein one base is provided with a hole, and the other base is bonded so as to close the periphery of the hole.

Furthermore, in the method for manufacturing the silicon nitride bonded body, the silicon nitride material comprising silicon nitride as a main component and erbium oxide (Er ₂ O ₃ ) and alumina (Al ₂ O ₃ ) as sintering aids. A step of obtaining a pair of substrates made of a sintered body, a bonding agent mainly composed of glass is applied to a predetermined position of one substrate, and the other substrate is placed via the bonding agent, and 1250 to 1400. And a heat treatment step at a temperature of ° C.

According to the present invention, when a silicon nitride sintered body containing Er ₂ O ₃ and Al ₂ O ₃ as a sintering aid is used as a substrate of a silicon nitride bonded body, when used as a member for a semiconductor manufacturing apparatus, It becomes possible to suppress the thermal expansion of the member as much as possible and prevent the shape change of the member due to heating. Thereby, for example, when used as a member for a wafer processing apparatus such as a wafer surface plate, the fine processing of the wafer surface and the surface processing are not affected. Similarly, when used as a semiconductor exposure stage, it is possible to minimize changes in the shape of the member when forming a mask pattern on a wafer, and it is possible to form a pattern with higher accuracy.

  In addition to this, the bonding layer of the silicon nitride bonded body includes a fine crystal composed of silicon nitride and an Er component, whereby the bonding layer can be increased in strength, and the bonding layer is formed by the action of the Er component. A low melting point and low thermal expansion can be achieved.

  Hereinafter, the best mode for carrying out the present invention will be described.

The silicon nitride bonded body of the present invention is formed by bonding a pair of bases made of a silicon nitride sintered body containing erbium oxide (Er ₂ O ₃ ) and alumina (Al ₂ O ₃ ) via a bonding layer. In addition, the bonding layer includes fine crystals made of silicon nitride and an Er component.

In the silicon nitride bonded body having such a structure, a silicon nitride sintered body as a base contains erbium oxide (Er ₂ O ₃ ), which acts as a sintering aid during sintering and is a main component. By reacting with β-Si ₃ N ₄ , β-Er ₂ Si ₂ O ₇ having a small thermal expansion exists between crystal grains of the silicon nitride sintered body. Therefore, for example, the thermal expansion coefficient is 1.4 × 10 ⁻⁶ / ° C. compared with a silicon nitride sintered body containing alumina (Al ₂ O ₃ ) and yttria (Y ₂ O ₃ ) as a sintering aid. The following can be low.

As described above, the reason why a silicon nitride sintered body having a small thermal expansion coefficient can be obtained is to reduce the thermal expansion of the silicon nitride bonded body itself by making β-Er ₂ Si ₂ O ₇ exist between crystal grains. Therefore, the sum of thermal expansion of each crystal of β-Si ₃ N ₄ and β-Er ₂ Si ₂ O ₇ which are main components when heat is applied to the sintered body can be reduced. As a result, the thermal expansion coefficient of the silicon nitride sintered body can be reduced to 1.4 × 10 ⁻⁶ / ° C. or less.

  The silicon nitride bonded body of the present invention is characterized in that the bonding layer contains fine crystals made of silicon nitride and an Er component.

Thereby, glass such as Y ₂ O ₃ —Al ₂ O ₃ —SiO ₂ glass, Yb ₂ O ₃ —Al ₂ O ₃ —SiO ₂ glass, Lu ₂ O ₃ —Al ₂ O ₃ —SiO ₂ glass, etc. In order to form Er ₂ O ₃ and β-Er ₂ Si ₂ O ₇ by precipitating fine crystals of silicon nitride in the bonding layer containing as a main component and further diffusing Er elements in the substrate into the bonding layer, The presence of β-Er ₂ Si ₂ O _{7 having} a low glass abundance ratio and low thermal expansion makes it possible to reduce the thermal expansion and increase the strength of the bonding layer.

In order to include the fine crystal made of silicon nitride and the Er component in the bonding layer in this way, the fine crystal made of silicon nitride is the main component of the joined body that becomes the bonding layer, as will be described in detail later. The glass component Si is fired in a nitrogen atmosphere to produce silicon nitride in the bonding layer of the resulting bonded body. The Er component diffuses into the bonding layer during the heat treatment. Thus, Er ₂ O ₃ and β-Er ₂ Si ₂ O ₇ are formed. In addition, by controlling the SiO ₂ particle size in the bonding agent to be the bonding layer, lowering the heat treatment temperature, and further adjusting the atmosphere gas, heat treatment temperature, and keeping time during the heat treatment, Fine crystals made of silicon nitride can be deposited and the Er component can be diffused from the substrate.

  The fine crystal of silicon nitride is a crystal of silicon nitride having an average crystal grain size of 0.2 μm or less, and the average crystal grain size of silicon nitride as a base is about 1 to 5 μm. The structure of the bonding layer containing the silicon nitride crystal having a small average crystal grain size has an effect of remarkably improving the strength of the bonding portion, and the bonding layer can have almost the same strength as that of the substrate. Furthermore, by using fine silicon nitride crystals, the thickness of the bonding layer can be further reduced. The thickness of the bonding layer can be very thin, 0.5-5 μm. If the thickness of the bonding layer is less than 0.5 μm, sufficient bonding strength cannot be obtained. The stress applied to the part is undesirably increased. The thickness of the bonding layer is more preferably 0.7-2 μm.

  As for the silicon nitride fine crystal in the bonding layer, for example, a part of the bonded body including the bonding layer is cut out, and the surface is mirror-finished by high-precision lapping, followed by SEM observation at 3000 to 10,000 times. To confirm its existence. And about the particle size, while analyzing the arbitrary places of a joining layer with a wavelength dispersion type | mold X-ray microanalyzer apparatus (the JXA-8600M type | model made by JEOL), while confirming distribution of N element of an observation part, the range It can be estimated from the size.

Further, as the Er component contained in the bonding layer, it is preferable that an Er element is contained in an amount of 5% by mass or less in terms of Er ₂ O ₃ . The Er component is included to promote the low thermal expansion of the bonding layer. When this amount exceeds 5% by mass, Y ₂ O ₃ —Al ₂ O mainly plays a role of bonding between the substrates. The amount of _3- SiO ₂ glass is small, which causes a decrease in bonding strength.

  The presence of the Er component in the bonding layer is determined by cutting out a part of the bonded body including the bonding layer, preparing a sample that has been subjected to mirror finishing on this surface by high-precision lapping, and then removing a part of the bonding layer by SEM. It is possible to carry out by magnifying 1000 to 5000 times, analyzing the range with a wavelength dispersive X-ray microanalyzer (JXA-8600M type manufactured by JEOL Ltd.), and confirming the distribution state of Er element in the observation part. is there. In addition, the amount of Er component is confirmed by cutting out only the bonding layer by precision machining, pulverizing it into a powder, and then confirming the amount of Er element with an ICP emission spectroscopic analyzer (ICPS-8100 manufactured by Shimadzu Corporation). And after observing the bonding layer at a magnification of 5000 to 20,000 times with a transmission electron microscope, an arbitrary portion of the bonding layer is analyzed with an energy dispersive X-ray diffractometer, and the Er count of each part is It can be confirmed by any of the methods for determining the mass ratio of the components.

  Such a silicon nitride bonded body having a small thermal expansion coefficient can be suitably used as a member for a semiconductor manufacturing apparatus such as a wafer processing surface plate or a stage having a hollow portion that is difficult to manufacture integrally, and can be used even at high temperatures. A member for a semiconductor manufacturing apparatus with small expansion and high dimensional accuracy can be obtained. Specifically, as shown in FIG. 1A, a disc-shaped base 4 having a convex portion 3 fitted to an edge of the base 1 is provided on one concave base 1 having a hole 2. Then, it is bonded via a bonding agent applied to the bonding portion 5 of the base body 1 to obtain a semiconductor manufacturing apparatus member composed of a cylindrical hollow body as shown in FIG.

  This member for a semiconductor manufacturing apparatus has a hollow inside in order to reduce the weight, and since a hollow body having such a structure cannot be formed integrally, it is manufactured as a joined body in which a pair of substrates 1 and 4 are joined. The For example, by using this as a surface plate or stage for wafer processing of semiconductor manufacturing equipment, semiconductor manufacturing that allows ultra-precise processing of wafers, ultra-precise wiring of semiconductors, etc., even with slight changes in temperature It can be a device.

  In addition, the intensity | strength of the joining layer of the silicon nitride joined body of this invention has the intensity | strength of 500 Mpa or more by the measurement based on JISR1601-1995. This strength is almost equal to or higher than that of the silicon nitride sintered body as the substrate. As for the thermal expansion coefficient, since it is necessary to measure the thermal expansion coefficient at room temperature in particular, the joined body including the base body and the joining layer is cut out and processed to have a length of 15 to 16 mm, and both ends in the length direction are formed. It is assumed that it is chamfered into an R shape. Next, using a laser thermal dilatometer manufactured by Vacuum Riko Co., Ltd., using a laser while heating the sample continuously in He gas at a temperature rising rate of about 1 ° C./min in the range of 0 to 50 ° C. The length of the sample was measured, and the coefficient of thermal expansion at 23 ° C. was measured in accordance with ASTM (The American Society of Testing and Materials) E289 (Standard Test Method for Linear Thermal Expansion of Rigid Solids with Interferometry).

  Next, the details of the method for producing the silicon nitride bonded body of the present invention will be described below.

As a method for producing a silicon nitride bonded body according to the present invention, first, a silicon nitride raw material powder having a purity of 99 to 99.8% containing Er ₂ O ₃ and Al ₂ O ₃ as sintering aids as a substrate is prepared. A binder, a dispersant, and a solvent are added to form a slurry, which is then granulated with a spray granulator (spray dryer) to produce a spherical secondary raw material powder. Thereafter, a molded body is produced using the secondary raw material powder by a powder press molding method or a wet isostatic press molding (rubber press) method, and is subjected to cutting as necessary. The base used for the silicon nitride bonded body of the present invention often forms holes and irregularities, and such holes and irregularities are often formed during the cutting process. And the said molded object is baked. Firing is performed at a maximum temperature of 1700 to 2000 ° C. in a nitrogen atmosphere. Thereafter, grinding may be performed as necessary to obtain a substrate of the silicon nitride bonded body of the present invention.

Next, a bonding agent is prepared. As the bonding agent, glass such as Y ₂ O ₃ —Al ₂ O ₃ —SiO ₂ , Yb ₂ O ₃ —Al ₂ O ₃ —SiO ₂ , Lu ₂ O ₃ —Al ₂ O ₃ —SiO ₂ is used. Here, the Y ₂ O ₃ powder has a purity of 98% or more and an average particle size of 0.5 to 1.5 μm, and the SiO ₂ powder has a purity of 99% or more and an average particle size of 0.5 μm. The following are used as Al ₂ O ₃ powder having a purity of 95% or more and an average particle size of 0.5 to 2 μm. Then, this _Y 2 _{O 3} is 35 to 45 wt%, _Al 2 _{O 3} is 10 to 30 mass%, as the sum of the three powders in the range SiO ₂ is 35 to 45 mass% of 100 mass% To mix.

Here, only the average particle diameter of the SiO ₂ powder must be reduced to 0.5 μm or less because the size of the SiO ₂ powder affects the size of the silicon nitride fine crystal formed in the bonding layer. It is. When SiO ₂ powder larger than 0.5 μm is used, the size of the silicon nitride fine crystal of the bonding layer cannot be made 0.2 μm or less. On the other hand, if the content of SiO ₂ is less than 35% by mass, it is difficult to form fine silicon nitride crystals in the bonding layer, and a high-strength bonding layer that constitutes the structure of the present invention cannot be obtained. On the other hand, if the amount of SiO ₂ exceeds 45% by mass, the amount of silicon nitride fine crystals produced is large, the amount of Y ₂ O ₃ —Al ₂ O ₃ —SiO ₂ glass is reduced, and the strength of the bonding layer is reduced. It is not preferable.

  Then, an appropriate amount of alumina balls and an organic solvent (isopropyl alcohol) added to the mixed powder is put into a cylindrical plastic container and mixed by rotating for 12 to 36 hours in parallel with the axial direction by a rotating device. After mixing, the slurry is discharged into a metal container while separating the alumina balls and the mixed slurry from the plastic container. After discharging, it is dried in a dryer at a temperature of 40 to 80 ° C. for 36 to 60 hours while being put in a metal container, and the powder mass obtained after drying is crushed to obtain a bonding material.

  Next, the raw material for the bonding agent, a solvent, and a dispersant are prepared. Add 100 to 20% by weight of solvent and 0.5 to 2% by weight of a dispersant with respect to 100% by weight of the raw material for the bonding agent, and put them into a cylindrical plastic container again. Mix for 8 hours or more while rotating with a rotating device parallel to the axial direction of the container. Here, as the solvent, it is preferable to use a hydrophobic organic solvent, for example, a paraffin-based solvent. When the hydrophobic organic solvent is applied to the bonding portion of one substrate to be bonded, the surface is difficult to dry, and the hydrophobic organic solvent is easily compatible with the bonding portion of the other substrate, so that a better bonding layer can be obtained. As the dispersant, it is preferable to use a nonionic surfactant suitable for the hydrophobic solvent. For example, sucrose fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid alkanolamide and the like are preferably used. Note that the mixed solution of the bonding agent raw material, the solvent, and the dispersing agent, that is, the bonding agent paste, is separated or solidified when placed and stored, so it is preferable to store it while rotating. Furthermore, the viscosity of the bonding agent paste is preferably 0.5 to 2 Pa · s. When the viscosity is lower than 0.5 Pa · s, the viscosity is too low, and this is not preferable because the paste drips without staying at the joint when applied to the joint of the substrate. A viscosity exceeding 2 Pa · s is not preferable because a thin paste cannot be applied to the bonding portion of the substrate, resulting in an increase in the thickness of the bonding layer.

  Next, the bonding agent paste produced as described above is applied to the bonding portion of the substrate made of the silicon nitride sintered body. The bonding paste may be applied using a brush or the like. However, in order to make the coating thickness more uniform, only a joint is opened, and the other is plugged. It is preferable that the opening portion is aligned with the joining portion, the joining paste is hung on the screen, and the joining paste is applied through the screen with a resin squeegee. Here, the coating thickness of the bonding agent paste is preferably in the range of 10 to 100 μm. When the thickness is less than 10 μm, when bonding the substrates made of silicon nitride sintered bodies to each other, the surface of one of the substrates is pressed and pressure is applied to the bonded portion, so that the bonding agent paste is difficult to spread uniformly over the entire bonded portion. . Furthermore, in the present invention, when the bonding agent paste that protrudes from the joint is in a molten state at the time of heat treatment, it spreads to the corners that are susceptible to stress concentration due to the influence of surface tension, and has the effect of reinforcing that part. To obtain a coating thickness of 10 μm or more is required. Moreover, when the coating thickness of the bonding agent paste exceeds 100 μm, the bonding agent paste that protrudes from the bonding portion after pressing adheres to the inner and outer surfaces of the substrate, and a good appearance cannot be obtained. Since additional work must be performed, the manufacturing cost increases accordingly, which is not preferable. Further, the pressure applied to the bonded portion may be set so that the pressure applied to the bonded surface (surface pressure) is 15 MPa or more, although it depends on the viscosity of the bonding agent paste.

Next, a bonding agent paste is applied, the bonded surfaces are brought into contact with each other and pressed, and then heat treatment is performed. For the heat treatment, a large batch furnace in which nitrogen gas is injected and the inside of the furnace can be adjusted to a nitrogen atmosphere is used. As the amount of nitrogen to be injected, it is preferable that the nitrogen amount is about 1 to 30% in terms of atomic ratio, and that the inside of the furnace is an N ₂ partial pressure of 2 to 5 × 10 ⁻³ MPa at normal pressure. If the heat treatment temperature is held at 1250 to 1400 ° C. for 0.5 to 3 hours, uniform and strong bonding is possible, and it is preferable to hold for 1 to 3 hours. By performing heat treatment in such an atmosphere, temperature, and holding time, finer silicon nitride crystals can be precipitated in the bonding layer, and the strength of the bonding layer can be increased. Further, the Er component in the substrate is easily diffused into the bonding layer, and it is possible to promote the low thermal expansion of the bonding layer. If the heat treatment temperature is lower than 1250 ° C., fine silicon nitride crystals cannot be generated in the bonding layer, and if it exceeds 1400 ° C., the components constituting the bonding layer begin to sublimate. The joint strength decreases. For this, in the present invention, the bonding layer is reduced in thermal expansion by diffusing the Er component from the substrate to the bonding layer, but the diffusion of the Er component also has the effect of lowering the melting point of the component constituting the bonding layer, As a result, the heat treatment temperature can be lowered and the heat treatment can be performed at a lower temperature, leading to a reduction in manufacturing cost.

  Details of the embodiments of the present invention will be described below.

(Example 1)
A silicon nitride joined body of the present invention and a conventional silicon nitride joined body were manufactured, and a test for comparing the joining strength and the thermal expansion coefficient was performed. Further, in the silicon nitride bonded body of the present invention, the presence or absence of a fine crystal composed of silicon nitride and an Er component in the bonding layer was confirmed.

As a silicon nitride bonded body sample of the present invention, first, a silicon nitride sintered body containing erbium oxide (Er ₂ O ₃ ) and alumina (Al ₂ O ₃ ) is manufactured in order to produce a substrate. Commercially available silicon nitride powder (purity 99.5% or more, average particle size 1 μm), erbium oxide powder (purity 99.5% or more, average particle size 1 μm), alumina powder (purity 99% or more, average particle size 1 μm) And 5 mass% of erbium oxide and 2.5 mass% of alumina powder were added to 100 mass% of silicon nitride powder and mixed with a mixing stirrer to contain erbium oxide and alumina as sintering aids. A silicon nitride powder is obtained. Thereafter, a binder, a dispersant, and a solvent are added to the powder to form a slurry, which is then granulated with a spray dryer to produce a secondary raw material powder. Then, using the secondary raw material powder, dozens of disk-shaped silicon nitride compacts having an outer diameter of 120 mm and a thickness of 40 mm were produced by a powder press molding method. Thereafter, the silicon nitride-based molded body is fired at 1900 ° C. in a nitrogen atmosphere to obtain a silicon nitride sintered body, which is subjected to grinding, and from a silicon nitride sintered body having an outer diameter of 100 mm and a thickness of 30 mm. Several dozen disk-shaped substrates were produced.

  Next, the bases are joined in a disk shape. The joining method is described below.

First, in order to produce a bonding agent paste, commercially available Y ₂ O ₃ powder (purity 98%, average particle size 1 μm), Al ₂ O ₃ powder (purity 95%, average particle size 1 μm), SiO ₂ powder (purity) 99%, average particle size 0.5 μm). Y ₂ O ₃ , Al ₂ O ₃ , and SiO ₂ powders were mixed in proportions of 40, 20, and 40% by mass, respectively, so that the total amount would be 100% by mass, and alumina balls and organic solvent (isopropyl alcohol) were mixed therewith. After adding a suitable amount, and rotating and stirring in a plastic container for 24 hours, the slurry is discharged from the plastic container to a predetermined metal container, and dried in a dryer at a temperature of 60 ° C. for 40 hours. Is crushed into a raw material for a bonding agent.

  Next, the raw material for a bonding agent, a solvent, and a dispersant are mixed. Add 100% by mass of isoparaffin as a solvent and 1.5% by mass of polyoxyethylene sorbitan fatty acid ester as a dispersant to 100% by mass of the raw material for the bonding agent, and again add them into a cylindrical plastic container. The mixture is mixed for 10 hours while rotating with a rotating device. The viscosity of the bonding agent paste was measured with an E-type viscometer and found to be 1 Pa · s.

After that, the obtained bonding agent paste is applied to the surface of the substrate made of a disk-shaped silicon nitride sintered body through a screen, and the substrate made of the disk-shaped silicon nitride sintered body is bonded to the coated surface. , And pressurized with a pressure of 15 MPa. After the pressurization, the joined body sample was heat-treated at a temperature of 1300 ° C. in a heat treatment furnace having a nitrogen content of 20% and an N ₂ partial pressure of 3 × 10 ⁻³ MPa.

  After heat treatment, for each sample taken out from the furnace, dozens of test piece sizes according to JIS R1601-1995 are cut out by grinding so that the bonding layer is located in the center, and a test piece for strength test is produced. Then, the three-point bending strength was measured. Note that the thickness of the bonding layer of each sample was 1.5 μm, and the substrate alone showed a strength of 600 MPa.

  Further, a similar sample is processed to include a bonding layer to have a length of 15 to 16 mm, and both ends in the length direction are chamfered into an R shape. Next, using a laser thermal dilatometer manufactured by Vacuum Riko Co., Ltd., using a laser while heating the sample continuously in He gas at a temperature rising rate of about 1 ° C./min in the range of 0 to 50 ° C. The length of the sample was measured, and the coefficient of thermal expansion at room temperature was measured according to the measurement based on ASTM (The American Society of Testing and Materials) E289 (Standard Test Method for Linear Thermal Expansion of Rigid Solids with Interferometry).

  In addition, in order to confirm the presence of silicon nitride microcrystals in the bonding layer, the surface including the bonding layer of the sample is subjected to high-precision lapping to make a mirror surface, and then the surface is observed by SEM, and an arbitrary portion is wavelength-dispersed. Analysis with a type X-ray microanalyzer (JXA-8600M type manufactured by JEOL Ltd.) confirmed the distribution of the N element. Further, the Er element was similarly analyzed to confirm the presence of the Er element in the bonding layer.

  The silicon nitride sintered body serving as the substrate of the silicon nitride joined body of the present invention had an average silicon nitride crystal grain size of 3 μm. The thickness of the bonding layer is 2 μm.

Subsequently, as Comparative Example 1, the same evaluation was performed for a conventional silicon nitride bonded body. As the substrate, a disc-shaped silicon nitride sintered body having an outer diameter of 100 mm and a thickness of 30 mm containing yttria (Y ₂ O ₃ ) and alumina (Al ₂ O ₃ ) as a sintering aid is used. as with silicon nitride bonded body of the present invention were bonded using _{Y 2 O 3 -Al 2 O 3} -SiO 2 based bonding agent. At this time, the average particle diameter of SiO ₂ used for the bonding agent was set to 1 μm. Furthermore, the heat treatment temperature was set to a high heat treatment temperature of 1550 ° C. because the bonding agent did not melt at the same 1300 ° C. as that of the silicon nitride bonded body of the present invention.

Further, as Comparative Example 2, a disk-shaped silicon nitride sintered body having an outer diameter of 100 mm and a thickness of 30 mm, containing yttria (Y ₂ O ₃ ) and alumina (Al ₂ O ₃ ) as a sintering aid in a base. This was used as an Er ₂ O ₃ —Y ₂ O ₃ —Al ₂ O ₃ —SiO ₂ bonding agent (Er ₂ O ₃ : 20% by mass, Y ₂ O ₃ : 20% by mass, Al ₂ O ₃ : 20 A conventional silicon nitride bonded body bonded by using (mass%, SiO ₂ : 40 mass%) was also prepared. The average particle diameter of SiO ₂ used for this bonding agent was set to 1 μm as in Comparative Example 1. The heat treatment temperature was 1450 ° C. at which the bonding agent melted and a good bonding state was obtained. Thereafter, the same evaluation as that of the silicon nitride bonded body of the present invention was performed.

The evaluation results of the present invention and Comparative Examples 1 and 2 are shown in Table 1.

In Table 1, Comparative Examples 1 and 2 each have a high heat treatment temperature. This is because, in Comparative Example 1, the Er component was not contained in the substrate, and the effect of lowering the melting point of the bonding agent due to the Er component diffusing into the bonding layer was not exhibited. In Comparative Example 2, although the Er component is contained in the bonding agent, the melting temperature of the bonding agent is high because the Er component content is large. Further, the strengths of both Comparative Examples 1 and 2 are low. This is because although the bonding layer contains silicon nitride crystals, the average particle size of SiO ₂ used for the bonding agent is large, so the silicon nitride crystal particle size in the bonding layer is larger than 0.2 μm, and the fine crystal It is because it is not. Furthermore, the thermal expansion coefficient of Comparative Example 1 is high because no Er component is present in the bonding layer and β-Er ₂ Si ₂ O ₇ is not generated. In Comparative Example 2, since the Er component is present, β-Er ₂ Si ₂ O ₇ is generated in the bonding layer, which is not as high as the present invention, but has a relatively low value.

Compared to this, the silicon nitride bonded body of the present invention has a smaller SiO ₂ average particle size used as a bonding agent, so that a fine crystal of silicon nitride of 0.2 μm or less can be precipitated in the bonding layer, and the bonding layer can be formed from the substrate. Since an appropriate amount of the Er component is diffused at a ratio of 5% by mass or less, β-Er ₂ Si ₂ O ₇ is generated, the bonding layer can be reduced in thermal expansion, the bonding agent can be reduced in melting point, and the heat treatment temperature is 1300 ° C. I was able to make it low.

It is the schematic which shows the structure of the hollow body which is a silicon nitride joined body of this invention, (a) is a disassembled perspective view, (b) is a perspective view after joining.

Explanation of symbols

1: Base body 2: Hole part 3: Convex part 4: Base body 5: Joint part

Claims (6)

A pair of substrates made of a silicon nitride sintered body containing silicon nitride as a main component and containing erbium oxide (Er ₂ O ₃ ) and alumina (Al ₂ O ₃ ), and a fine crystal made of silicon nitride as a main component And a silicon nitride bonded body bonded through a bonding layer containing an Er component. _{2. The} silicon nitride bonded body according to claim 1, wherein the Er component in the bonding layer is contained in a range of 5 mass% or less in terms of Er ₂ O ₃ . 3. The silicon nitride bonded body according to claim 1, wherein the fine crystal made of silicon nitride in the bonding layer has an average crystal grain size of 0.2 μm or less. 4. The silicon nitride bonded body according to claim 1, wherein the bonding layer has a thickness of 0.5 to 5 μm. The method for producing a silicon nitride bonded body according to any one of claims 1 to 4, wherein silicon nitride is a main component, and erbium oxide (Er ₂ O ₃ ) and alumina (Al ₂ O ₃ ) are used as sintering aids. A step of obtaining a pair of bases made of a silicon nitride-based sintered body, and a bonding agent mainly composed of glass applied to a predetermined position of one of the bases, and the other base through the bonding agent And a step of heat-treating at a temperature of 1250 to 1400 ° C. 5. A semiconductor manufacturing apparatus comprising the silicon nitride bonded body according to claim 1, wherein a hole is formed on one base and the hole is closed by the other base. Materials.

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