JP5435932B2 - Alumina sintered body, manufacturing method thereof, member for semiconductor manufacturing apparatus, member for liquid crystal panel manufacturing apparatus, and member for dielectric resonator - Google Patents

Description

  The present invention relates to an alumina sintered body, a member for a semiconductor manufacturing apparatus, a member for a liquid crystal panel manufacturing apparatus, and a member for a dielectric resonator, and in particular, an inner wall material (chamber), a microwave introduction window, a shower of a semiconductor manufacturing apparatus. Used in parts such as heads, focus rings, shield rings, liquid crystal panel manufacturing equipment stages, mirrors, mask holders, mask stages, chucks, reticles, and other high-frequency regions such as microwaves and millimeter waves It can be suitably used for various resonator materials, MIC dielectric substrate materials, dielectric waveguide materials, and the like.

  Conventionally, alumina sintered bodies are excellent in heat resistance, chemical resistance, and plasma resistance, and have a low dielectric loss tangent (tan δ) in the high frequency region, so they have been used for semiconductors and high frequency plasma device members for liquid crystals. ing.

  Semiconductor or liquid crystal panel manufacturing equipment members are in contact with highly reactive halogen-based corrosive gases used for etching and cleaning, and their plasmas, and therefore require high corrosion resistance, and generally 99.0 mass. % Or more high-purity alumina sintered body is required. On the other hand, the dielectric loss tangent increases from the viewpoint of sinterability as it becomes a high-purity alumina sintered body, which decreases the high-frequency transmittance in the MHz band, increases energy loss, breaks the member due to heat generation, etc. Problems are known to occur.

For reducing the loss of the alumina sintered body, SiO ₂ , CaO, and MgO are included as sintering aids, and the content is controlled to be within a certain range. There is known an alumina sintered body with improved sinter (see, for example, Patent Document 1).

In Patent Document 1, and 99.8 to 99.9 wt% alumina, the balance is composed of a _SiO 2, CaO, grain boundary phase component composed of MgO having a predetermined ratio, Q value at a measuring frequency 8GHz 10,000 or more ( It is described that an alumina sintered body for a microwave resonator having a dielectric loss tangent of 0.0001 or less was obtained.
JP-A-6-16469

As in Patent Document 1, an alumina sintered body containing SiO ₂ , CaO, and MgO has a dielectric loss tangent of 0.0001 or less at a measurement frequency of 8 GHz. However, the dielectric loss tangent in the MHz band is large. For example, when used for a member for a high-frequency plasma device for semiconductors in which a high frequency in the MHz band is used, the transmittance of the high frequency in the MHz band is reduced, and energy loss Problems such as increase and damage to members due to heat generation have occurred. Furthermore, in recent years, there are applications in a wide frequency range from the MHz band to the GHz band, and a reduction in loss has been demanded there.

  An object of the present invention is to provide an alumina sintered body capable of reducing the dielectric loss tangent in the MHz band to the GHz band, a manufacturing method thereof, a member for a semiconductor manufacturing apparatus, a member for a liquid crystal panel manufacturing apparatus, and a member for a dielectric resonator. .

Alumina sintered body of the present invention, the A l _Al 2 _{O 3} in terms of 99.3 mass% or more, 0.05 to 0.32 wt% of Si in terms of SiO _2, the Sr in terms of SrO 0.01 ~ 0.16% by mass and alumina crystal particles as the main crystal particles, there is a crystal phase containing each element of Si, Al, Sr and O at the triple point composed of the alumina crystal particles , the crystal phase is present in 60% or more of the triple point, and the average particle size of the alumina crystal particles, characterized in der Rukoto less than 10 [mu] m.

Such an alumina sintered body contains Al as an element in an amount of 99.3% by mass or more in terms of Al ₂ O ₃ , so that it can maintain the original excellent corrosion resistance, mechanical characteristics, and electrical characteristics of alumina. In addition, since there is a low-loss crystal phase containing Si, Al, Sr and O elements in the triple point composed of alumina crystal particles, instead of the conventional glass composed of grain boundary phase components, A low-loss alumina sintered body can be obtained in the MHz band to the GHz band.

The alumina sintered body of the present invention is characterized in that the crystal phase is a SrAl ₂ Si ₂ O ₈ type crystal phase. Since the SrAl ₂ Si ₂ O ₈ type crystal phase has a low loss in the MHz band to the GHz band, an alumina sintered body having a low loss in the MHz band to the GHz band can be obtained.

Furthermore, the alumina sintered body of the present invention desirably contains at least one of Mg and Ca as an element. In such an alumina sintered body, Mg and Ca can function as a sintering aid, improve the sinterability, and obtain a lower loss alumina sintered body in the MHz band to the GHz band. Can do. Furthermore, since the sinterability is improved, for example, the central portion in the thickness direction of the thick sintered body is sufficiently sintered, and the characteristics such as the mechanical strength of the entire thick sintered body can be improved. . When Ca is contained, the low-loss SrAl ₂ Si ₂ O ₈ type crystal phase containing Si, Al, Sr, Ca, and O elements, for example, (Sr, Ca) Al ₂ Si ₂ O ₈ By forming the crystal to be produced, the dielectric loss tangent of the alumina sintered body can be further reduced.

  In the alumina sintered body of the present invention, the crystal phase containing each element of Si, Al, Sr, and O exists at a triple point of 60% or more of the triple points composed of the alumina crystal particles. It is characterized by doing.

  In such an alumina sintered body, a low-loss crystal phase containing each element of Si, Al, Sr and O is present in 60% or more of the triple points in the sintered body. Since the existence ratio of the amorphous phase that increases the tangent is reduced, the dielectric loss tangent at a frequency of 1 MHz to 8.5 GHz can be reduced.

  The alumina sintered body of the present invention is characterized in that the average particle diameter of the alumina crystal particles is less than 10 μm. Such an alumina sintered body can improve strength.

The manufacturing method of the alumina sintered body of the present invention is as follows. The content after firing to 99.3% by mass or more of alumina powder is 0.05 to 0.32% by mass in terms of SiO ₂ and Sr in terms of SrO. After mixing a raw material powder obtained by heat-treating a mixture containing Si source and Sr source in an amount of 0.01 to 0.16% by mass in the air, it is molded into a predetermined shape and fired in the air And

In such a method for producing an alumina sintered body, a mixture containing an Sr source and an Si source is heat-treated in the atmosphere to produce a raw material powder in which Sr and Si are partially reacted and synthesized. The raw material powder for forming the boundary phase is added to the alumina powder, mixed, and fired in the atmosphere. Therefore, a small amount of raw material powder for forming the grain boundary phase can be sufficiently uniformly mixed in the alumina powder. The raw material powder that forms the grain boundary phase at the time of firing melts and gathers at the triple point composed of alumina crystal particles, and Al, Sr, and Si react to contain Si, Al, Sr, and O elements A low-loss crystal phase composed of a compound exists at the triple point of the alumina crystal particles.

  The member for a semiconductor manufacturing apparatus, the member for a liquid crystal panel manufacturing apparatus, and the member for a dielectric resonator according to the present invention are made of the above-mentioned alumina sintered body. Such a member for a semiconductor manufacturing apparatus, a member for a liquid crystal panel manufacturing apparatus, and a member for a dielectric resonator have a small dielectric loss tangent in a frequency region between MHz and GHz, so that high-frequency transmittance in the MHz to GHz band is improved. Energy loss can be reduced, and damage to the member due to heat generation can be suppressed.

In the alumina sintered body of the present invention, since Al is contained in an amount of 99.3% by mass or more in terms of Al ₂ O ₃ , the original excellent corrosion resistance, mechanical properties, and electrical properties of alumina can be maintained. , Si is contained in 0.05 to 0.32 mass% in terms of SiO ₂ , Sr is contained in 0.01 to 0.16 mass% in terms of SrO , and the conventional grain boundary phase is composed of triple points composed of alumina crystal particles. A low loss crystal phase containing Si, Al, Sr, and O elements, not glass composed of components, is present in more than 60% of the triple points, so that the loss of alumina in the MHz to GHz band is lower than before. A quality sintered body can be obtained.

In the method for producing an alumina sintered body of the present invention, a small amount of raw material powder for forming a grain boundary phase can be sufficiently uniformly mixed in the alumina powder, and the grain boundary phase is formed during firing. The raw material powder melts, gathers at the triple point of the alumina crystal particles, Al reacts with Sr and Si, and the low-loss crystal phase containing Si, Al, Sr and O elements becomes the triple point of the alumina crystal particles. It can be an existing organization.

  Furthermore, in the semiconductor manufacturing device member, the liquid crystal panel manufacturing device member, and the dielectric resonator member of the present invention, the dielectric loss tangent is small in the frequency range between MHz and GHz, and therefore, the high frequency transmittance in the MHz to GHz band. Can be improved, energy loss can be reduced, and damage to the member due to heat generation can be suppressed.

  The alumina sintered body of the present invention is an alumina sintered body containing alumina crystal particles as main crystal particles and containing Si and Sr as elements, wherein Si, Al, There is a low-loss crystalline phase containing Sr and O elements. FIG. 1 shows a schematic cross-sectional view of an alumina sintered body. Reference numeral 1 is alumina crystal particles, and reference numeral 2 is a triple point.

  In the present application, the triple point 2 constituted by the alumina crystal particles 1 is a grain boundary formed by three or more alumina crystal particles 1, and a two-plane grain boundary 5 constituted by two alumina crystal particles 1. Is different.

  In general alumina sintered bodies, subcomponents added as sintering aids exist between the alumina crystal particles as glass or crystals with a high dielectric loss tangent, and tend to increase the dielectric loss tangent of the entire alumina sintered body. was there. However, when a low-loss crystal phase containing Si, Al, Sr, and O elements is deposited on the triple point composed of alumina crystal particles as in the present invention, the crystal phase itself has a low dielectric loss tangent. Moreover, the dielectric loss tangent in the MHz band to the GHz band of the entire alumina sintered body can be reduced.

In addition, as described above, alkaline earth metals such as Mg and Ca have been conventionally known as sintering aids, but among alkaline earth metals, Sr and Ba have a large ionic radius, so sintering. It is not used as an auxiliary agent, and in particular, there is no example of actively using Sr. In the present invention, in particular, Sr is not used as a sintering aid, but is used to precipitate SrAl ₂ Si ₂ O ₈ type crystal phase which is a low dielectric loss tangent crystal phase. Therefore, the dielectric loss tangent of the alumina sintered body can be lowered directly.

The low-loss crystal phase containing Si, Al, Sr, and O elements is preferably a SrAl ₂ Si ₂ O ₈ type crystal from the viewpoint of electrical characteristics, and the generation of this crystal can reduce the dielectric loss tangent. As a low-loss crystal phase containing Si, Al, Sr and O elements, other than the stoichiometric composition of SrAl ₂ Si ₂ O ₈ , it may be slightly deviated from the stoichiometric composition. In the present invention, the SrAl ₂ Si ₂ O ₈ type crystal is a concept including one in which a part of the constituent elements is replaced with another element. For example, it is a concept that includes one in which some of the constituent elements of SrAl ₂ Si ₂ O ₈ are substituted with other elements, such as (Sr, Ca) Al ₂ Si ₂ O ₈ .

  In the present invention, it is desirable that a crystal phase composed of a compound containing Si, Al, and Sr as elements exists in the triple point 2 of 60% or more of the triple point 2 constituted by the alumina crystal particles 1. The crystal phase is present in the triple point 2 of 60% or more of the triple point 2 constituted by the alumina crystal particles 1. This means that a crystal phase composed of a compound containing Si, Al and Sr exists in at least 60% of the triple point 2 of the above.

  In the present invention, at least 60% of the many triple points 2 are mixed with the raw material powder constituting the crystal phase, as will be described later, so that the crystal phase composed of the compound containing Si, Al and Sr exists. The mixed powder is pulverized and calcined to synthesize a crystal phase composed of a compound containing Si, Al and Sr and added to the alumina powder. Alternatively, in order to make a crystal phase composed of a compound containing Si, Al, and Sr exist, raw material powders of Si and Sr are mixed and pulverized, the mixed powder is calcined, and this is added to the alumina powder.

  Thus, since the low dielectric loss tangent crystal phase is present in the triple point 2 of 60% or more of the triple points 2, the alumina sintered body can be further reduced in the dielectric loss tangent. In order to reduce the dielectric loss tangent even in the frequency region between 1 MHz and 8.5 GHz, the ratio of the grain boundary triple point 2 where the crystal phase of the low dielectric loss tangent exists is preferably 80% or more.

  In the present invention, the triple point 2 composed of the alumina crystal particles 1 and the triple point 2 where the above crystal phase does not exist has an amorphous phase containing Si, Al and Sr as elements. Or a crystal phase to be described later exists. The triple point where an amorphous phase containing Si, Al, and Sr as elements exists does not substantially exist or is 50% or less in a predetermined area of an arbitrary cross section.

Moreover, it is desirable that the alumina sintered body of the present invention further contains at least one of crystal phases composed of compounds represented by MgAl ₂ O ₄ and CaAl ₁₂ O ₁₉ . These crystals are present at the triple point 2 composed of the alumina crystal particles 1. By generating these crystal phases, the amorphous phase that increases the dielectric loss tangent can be reduced, and the dielectric loss tangent can be lowered in the region of 1 MHz to 8.5 GHz. In particular, MgAl ₂ O ₄ and CaAl ₁₂ O ₁₉ have a low dielectric loss tangent in the GHz band, and are therefore effective in reducing the dielectric loss tangent in the GHz band of an alumina sintered body.

Alumina sintered body of the present invention has an average particle diameter D ₅₀ of the crystal grains of alumina is less than 10 [mu] m. Since the average particle size is small in this way, the dielectric loss tangent is slightly increased, but the strength of the sintered body can be improved. From the viewpoint of obtaining a low dielectric loss tangent, the average particle diameter D ₅₀ of the alumina crystal particles 1 is preferably 5 μm or more. Incidentally, the average particle diameter D _50, refers to the particle size of cumulative 50% fine particle side of the cumulative particle size distribution.

The alumina sintered body of the present invention contains Al in an amount of 99.3% by mass or more in terms of Al ₂ O ₃ and contains Si and Sr as elements. In addition, Mg can be contained. Mg is an optional component, but by containing Mg, electrical characteristics such as dielectric loss tangent can be improved, sinterability can be improved, and mechanical strength can be improved.

In addition to Si, Mg and Sr, it is desirable to contain Ca as a subcomponent. Although Ca is not necessarily required, it is preferably added in an appropriate amount from the viewpoint of electrical and mechanical properties since the sinterability is improved by adding it in the same manner as Mg. When Ca is contained, a low-loss SrAl ₂ Si ₂ O ₈ type crystal phase containing Si, Al, Sr, Ca, and O elements is formed between the alumina crystal particles. This low-loss crystal phase is preferably a compound represented by (Sr, Ca) Al ₂ Si ₂ O ₈ from the viewpoint of electrical characteristics. Not only (Sr, Ca) Al ₂ Si ₂ O ₈ but also a slight deviation from the stoichiometric composition may be used.

The alumina sintered body of the present invention preferably contains 99.3% by mass of Al in terms of Al ₂ O ₃ and 0.7% by mass or less of other subcomponents. By containing Al Al ₂ O ₃ in terms of 99.3% by mass or more, can maintain excellent corrosion resistance and mechanical properties at the same time Al ₂ O ₃ and improvement of the sinterability, the electrical characteristics Become. When the amount of the subcomponent is 0.7% by mass or more, it leads to a decrease in mechanical / electrical characteristics and a decrease in plasma resistance. Therefore, it is preferable that Al is 99.3% by mass or more in terms of Al ₂ O ₃ and the subcomponent is 0.7% by mass or less.

0.01 The subcomponent in the sintered body, 0.05-0.3 wt% of Si in terms of SiO _2, 0.01 to 0.16 wt% of Sr in terms of SrO, and Mg in terms of MgO It is preferable to contain 0.1 mass% and Ca 0.01-0.16 mass% in conversion of CaO. By setting it as such a composition range, it becomes possible to improve the sinterability of Al ₂ O ₃ and to improve the mechanical characteristics and electrical characteristics by generating crystals containing Si, Al, Sr, and O elements.

  The alumina-based sintered body of the present invention is used as a part for industrial machinery, and can be suitably used as a large and thick member used especially for a semiconductor manufacturing apparatus or a liquid crystal panel manufacturing apparatus. The member for a semiconductor manufacturing apparatus in the present invention means an inner wall material (chamber), a microwave introduction window, a shower head, a focus ring, a shield ring, or the like of the semiconductor manufacturing apparatus. A member for a liquid crystal panel manufacturing apparatus refers to a stage, a mirror, a mask holder, a mask stage, a chuck, a reticle, and the like.

In particular, in order to be applied as a member for a semiconductor or liquid crystal panel manufacturing apparatus, it is necessary to have excellent corrosion resistance against plasma under a halogen-based gas, so Al is 99.5% by mass or more in terms of Al ₂ O _3. Is preferred. From the viewpoint of sinterability, it is desirable that Al is 99.9% by mass or less in terms of Al ₂ O ₃ . Examples of the halogen-based gas include fluorine-based gases such as SF ₆ , CF ₄ , CHF ₃ , ClF ₃ , NF ₃ , C ₄ F ₈ , and HF, and chlorine-based gases such as Cl ₂ , HCl, BCl ₃ , and CCl _4. There is a gas or a bromine-based gas such as Br ₂ , HBr, or BBr ₃ . In order to enhance the etching effect of semiconductors, liquid crystal panels, etc., plasma may be generated by introducing an inert gas such as Ar together with the halogen-based gas.

  Furthermore, the alumina sintered body of the present invention is also used as a dielectric resonator, a dielectric substrate for MIC, a waveguide or the like in a high frequency region such as a microwave or a millimeter wave. In particular, it can be suitably used as a dielectric resonator member such as a support for various dielectric resonators.

  Next, the manufacturing method of the alumina sintered body of this invention is demonstrated. In order to obtain an alumina sintered body having a low dielectric loss tangent, it is important that a crystal phase having a low dielectric loss tangent in the MHz band to the GHz band is generated at the triple point composed of alumina crystal particles. By achieving a higher density by improving the sinterability, an alumina sintered body having a lower dielectric loss tangent can be obtained.

  In the method for producing an alumina sintered body of the present invention, the raw material powder obtained by mixing the Si source and the Sr source and heat-treating in the air is mixed with the alumina powder. Bake at 1800 ° C.

The raw material powder obtained by mixing and firing the Sr source and the Si source is prepared by mixing the Si source and the Sr source at a predetermined ratio so as to generate, for example, an SrAl ₂ Si ₂ O ₈ type crystal phase, and is 500 ° C. in the atmosphere. It is a powder obtained by heat treatment (also referred to as calcination) at ˜1400 ° C. The Si source and Sr source here may be any of metals, oxides, hydroxides, carbonates, nitrates, and other salts. By using the raw material powder of Si and Sr, the distribution of Si and Sr in the alumina sintered body can be made uniform, and the non-uniform sintered structure can be eliminated.

  In addition, it is possible to preferentially cause the reaction between Si and Sr to generate a crystal having a low dielectric loss tangent composed of Si, Sr, Al, and O elements between alumina crystal particles. If the distribution of Si and Sr is not uniform, an amorphous phase (glass) or a crystalline phase having a high dielectric loss tangent is generated, which causes an increase in the dielectric loss tangent of the entire alumina sintered body.

In addition, Si source, Sr source, and Al source are mixed at a predetermined ratio so as to produce SrAl ₂ Si ₂ O ₈ type crystals, fired at 500 ° C. to 1400 ° C. in the atmosphere, and directly SrAl ₂ Si ₂ O. It is also possible to produce type ₈ crystals and add them to the alumina powder. In this case, the SrAl ₂ Si ₂ O ₈ type crystal can be more reliably dispersed in the alumina sintered body.

  The raw material powder may be calcined by mixing a Ca source in addition to the Sr source and the Si source. The Ca source may be any metal, oxide, hydroxide, carbonate, nitrate, or other salt.

  When the raw material powder obtained by mixing the Sr source and Si source or the Sr source, Si source and Ca source and calcining in the atmosphere with the alumina powder and the raw material powder containing the Mg source and firing in the air There is also. As the Mg source, it is possible to use salts such as metals, metal oxides, metal hydroxides, and metal carbonates as powders or aqueous solutions.

  For molding, a molding method such as press molding, casting, cold isostatic pressing, or cold isostatic pressing can be used. Next, the obtained molded body is fired in the temperature range of 1500 to 1800 ° C. This makes it possible to produce an alumina sintered body having a high density and a crystal phase made of a compound containing Si, Sr, Al, and O elements at the triple point composed of alumina crystal particles.

  A method for measuring the dielectric loss tangent of the alumina sintered body of the present invention will be described.

By measuring the dielectric loss tangent of the sintered body at a measurement frequency of 1 MHz and 8.5 GHz, and using a non-defective product of 5 × 10 ⁻⁴ or less at 1 MHz and 5 × 10 ⁻⁴ or less at 8.5 GHz, a measurement frequency of 1 MHz to A dielectric loss tangent can be expected to be 5 × 10 ⁻⁴ or less even in a frequency region between 8.5 GHz. By this method, it is possible to use a highly accurate capacitance meter (Hewlett Packard: HP-4278A) and network analyzer (Agilent Technology: 8722ES) with respect to dielectric loss tangent, and 1 MHz that cannot be guaranteed by a conventional impedance analyzer. It is possible to design a low dielectric loss tangent material in the ˜8.5 GHz band.

When measuring with a network analyzer using a sample having a dimension when measuring the dielectric loss tangent with a capacitance meter based on JIS C2141, the measurement frequency may slightly deviate from 8.5 GHz. This deviation comes from the sample outer dimensional accuracy and the variation in the dielectric constant of the material. In the case of an alumina sintered body of Al ₂ O ₃ 99.3% or more, 8.5 ± 0.3 GHz is expected.

That is, conventionally, the dielectric loss tangent at a measurement frequency of 1 MHz is measured using a capacitance meter (HP-4278A), and the dielectric loss tangent at a measurement frequency of 8.5 GHz is measured using a cavity resonator method (network analyzer 8722ES). Are known to obtain accurate dielectric loss tangents of ± 2 × 10 ⁻⁴ or less and ± 0.1 × 10 ⁻⁴ or less, respectively, but from 1 MHz required for semiconductor and liquid crystal panel manufacturing apparatus members In the frequency region of 8.5 GHz, particularly 10 MHz to 1 GHz, there is only measurement using an impedance analyzer (HP-4291A, manufactured by Hewlett-Packard Company), and the measurement error is about ± 30 × 10 ⁻⁴ even if it is small, 5 × 10 Measurement accuracy is very low for dielectric loss tangent of ^-4 or less.

Therefore, the dielectric loss tangent at the measurement frequency of 1 MHz and 8.5 GHz is measured without directly measuring the dielectric loss in the frequency domain from 1 MHz to 8.5 GHz with an impedance analyzer with low measurement accuracy, and the measurement frequency at 1 MHz and 8.5 GHz is measured. When the dielectric loss tangent is in the range of 5 × 10 ⁻⁴ or less, the dielectric loss tangent can be recognized as 5 × 10 ⁻⁴ or less even in the frequency range between 1 MHz to 8.5 GHz, particularly 10 to 100 MHz, The dielectric loss tangent at a measurement frequency of 1 MHz to 8.5 GHz can be measured easily and accurately.

First, powders of SiO ₂ , SrCO ₃ , and CaCO ₃ were weighed and mixed so as to have the compositions shown in Table 1 in terms of SiO _{2 and in} terms of SrO and CaO, respectively, to obtain a mixed powder. This powder was heat-treated at 1000 ° C. to 1300 ° C. in the atmosphere, and pulverized for 48 to 72 hours in an alumina ball mill to produce a raw material powder.

Purity 99.95% by mass of _Al 2 _{O 3} powder, the the raw material powder, the Mg _{(OH) 2} powder was added in an amount shown in Table 1 in terms of MgO, to which a predetermined amount of water was added The slurry was mixed for 48 hours with an alumina ball mill. The slurry is added to the slurry, dried, granulated, and the mixed powder is molded at a pressure of 1 t / cm ² to produce a cylindrical molded body (diameter 60 mm × height 30 mm). Then, firing was performed in the air to obtain an alumina sintered body having a diameter of 50 mm and a height of 25 mm.

Quantitative analysis of the elements of this alumina sintered body is performed by ICP emission spectroscopic analysis. In Table 1, Al is converted to Al ₂ O ₃ , Si is converted to SiO ₂ , Sr is converted to SrO, and Mg is converted to MgO. , Ca is described in terms of CaO. In addition, elements other than Al, Si, Sr, Mg, and Ca are used as the balance, and the amounts are also described. The balance was mainly Na ₂ O and Fe ₂ O ₃ .

Moreover, it was confirmed by X-ray diffraction measurement that all the samples in Table 1 had alumina crystal particles as main crystal particles. Furthermore, the presence / absence of a crystal phase composed of a compound represented by MgAl ₂ O ₄ or CaAl ₁₂ O ₁₉ was confirmed by X-ray diffraction measurement, and listed in Table 2 as the presence / absence of spinel or the like.

  A sample having a thickness of 1 mm was cut out from the center in the height direction of the obtained sintered body, and the density and dielectric loss tangent were measured. The density was measured by the Archimedes method.

  The dielectric loss tangent tan δ is measured at 1 MHz, 12 MHz, and 8.5 GHz, and measured using a capacitance meter (HP-4278A), impedance analyzer (HP-4291A), and cavity resonator method (network analyzer 8722ES), respectively. Was done.

  In addition, the frequency dependence of the dielectric loss tangent at 1 MHz to 1 GHz was also confirmed by an impedance analyzer. As a result, the dielectric loss tangent at 1 MHz to 1 GHz in this sample tends to be high at 1 to 10 MHz and 100 MHz to 1 GHz and low in the frequency band between them, particularly at 10 to 100 MHz. Tended to be low. Moreover, no peak was observed in the dielectric loss tangent in the frequency band of 10 to 100 MHz, and the shape was flat.

  First, using a network analyzer, a sample having a diameter of 50 mm × thickness 1 mm is sandwiched by a jig to obtain a dielectric loss tangent at 8.5 GHz. Next, using an impedance analyzer, the sample having a diameter of 50 mm × thickness 1 mm is cured. The electrode was formed on the upper and lower surfaces of the sample having a diameter of 50 mm and a thickness of 1 mm based on JIS C2141, and the dielectric loss tangent at 1 MHz was obtained with a capacitance meter. .

Moreover, the analysis of the crystal phase in each sintered body is performed by energy dispersive X-ray spectroscopic analysis (EDS) and limited-field electron diffraction using a transmission electron microscope (TEM), and MAl ₂ Si ₂ O ₈ Regarding the presence or absence of the type crystal phase (M is at least one of Sr and Ca), 30 grain boundary triple points were confirmed, and the generation ratio of the crystal phase and the generation ratio of the amorphous phase are shown in Table 2. Table 1 shows the presence or absence of the SrAl ₂ Si ₂ O ₈ type crystal phase.

Whether the grain boundary triple point is an amorphous phase was confirmed by limited-field electron diffraction. The amorphous phase contained Si, Al, Sr, and O elements. In addition, the crystal phase at the triple point was MAl ₂ Si ₂ O ₈ type crystal phase, and M was Sr or Ca or Sr and Ca as shown in Table 2. In FIG. Ten electron diffraction images were shown.

Further, the average particle diameter _{D 50} of the alumina crystal grain, the scanning electron micrograph of the sample (500 fold) in the range of 0.0432Mm ^2, determine the diameter of each crystal grain in an image analyzer, the average particle calculating the diameter _{D 50,} as described in Table 2.

  Further, the bending strength of the alumina sintered body was measured according to JIS R1601, and listed in Table 2.

From Tables 1 and 2, in the sample of the present invention containing Si, Sr, and O elements as subcomponents in addition to Al ₂ O ₃ , the crystal phase composed of a compound containing Si, Al, Sr, and O elements between the alumina crystal particles. Is generated, and the dielectric loss tangent is 2.2 × 10 ⁻⁴ or less at 8.5 GHz and low loss of 29 × 10 ⁻⁴ or less at 1 MHz and 5.1 × 10 ⁻⁴ or less at 12 MHz. I understand that.

  In addition, when the crystal phase containing each element of Si, Al, Sr and O is present at a triple point of 60% or more of the three points formed of alumina crystal particles, the dielectric loss tangent becomes smaller. I understand that. Furthermore, since the average particle diameter of the alumina crystal particles is 9.8 μm or less, it can be seen that the bending strength is 350 MPa or more.

On the other hand, Sample No. Thirteen samples were prepared as follows. The Al ₂ O ₃ powder having a purity of 99.95% by mass was mixed with SiO ₂ powder, CaCO ₃ powder, and Mg (OH) ₂ powder in Sample No. 1 in Table 1. 13 was added at a ratio shown in FIG. 13, and a predetermined amount of water was added thereto and mixed for 48 hours by a ball mill to form a slurry. The slurry is added with a binder, dried, granulated, and the mixed powder is molded at a pressure of 1 t / cm ² to produce a molded body (diameter 60 mm × height 30 mm) and fired at 1600 ° C. Was done.

The central part (thickness 1 mm) in the height direction of the obtained sintered body was cut out and evaluated by the same method as in the above examples. As a result of analysis, crystals composed of Si, Ca, Al, and O elements were generated between the alumina crystal particles. The value of dielectric loss tangent was as low as 1.4 × 10 ⁻⁴ or less at 8.5 GHz, but it was as high as 40 × 10 ^{−4 at} 1 MHz and 7 × 10 ^{−4 at} 12 MHz, and the dielectric loss was in the MHz band. it was high.

It is a schematic sectional drawing which shows the structure of an alumina sintered body. Sample No. 10 is an electron diffraction image.

Explanation of symbols

1 ... Alumina crystal particles 2 ... 3 points

Claims (7)

The A l _Al 2 _{O 3} in terms of 99.3 mass% or more, 0.05 to 0.32 wt% of Si in terms of SiO _2, while containing 0.01 to 0.16 wt% in terms of SrO and Sr, Alumina crystal particles are used as main crystal particles, and a crystal phase containing each element of Si, Al, Sr, and O is present at a triple point composed of the alumina crystal particles. % there over, and alumina sintered body having an average particle diameter of the alumina crystal particles, characterized in der Rukoto less than 10 [mu] m. _2. The alumina sintered body according to claim 1, wherein the crystal phase is a SrAl ₂ Si ₂ O ₈ type crystal phase. The alumina-based sintered body according to claim 1 or 2, comprising at least one of Mg and Ca as an element. In the alumina powder of 99.3% by mass or more, the content after firing is 0.05 to 0.32% by mass in terms of Si in terms of SiO ₂ and 0.01 to 0.16% by mass in terms of SrO. A method for producing an alumina sintered body, comprising mixing raw material powder obtained by heat-treating a mixture containing a Si source and a Sr source in the atmosphere, then forming the mixture into a predetermined shape and firing the mixture in the atmosphere. A member for a semiconductor manufacturing apparatus, comprising the alumina sintered body according to any one of claims 1 to 3 . A member for a liquid crystal panel manufacturing apparatus, comprising the alumina sintered body according to any one of claims 1 to 3 . A dielectric resonator member comprising the alumina sintered body according to any one of claims 1 to 3 .