JP2011001198A - Method for producing plasma-proof fluoride sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a fluoride sintered compact suitable for a component required for high plasma-proof characteristics in an apparatus for producing a silicon semiconductor, a compound semiconductor and the like.SOLUTION: The method for producing the fluoride sintered compact includes: a step to mix 1-5 wt.% of a high purity MgFpowder with a high purity CaFpowder and further add and mix 0.1-1 wt.% of a sintering auxiliary agent; a molding step at a press pressure of 0.2 MPa/cmor more using a mold and a press-molding machine; a step to temporarily sinter the molded material by heating at 600-700°C in the atmosphere; and a step to form a CaF-MgFbinary sintered compact having a dense structure by heating at 1,250-1,370°C for 6-12 hours in the atmosphere.

Description

The present invention relates to a method for producing a plasma-resistant fluoride sintered body, and more specifically, CaF ₂ -MgF ₂ having a dense structure suitable for a plasma-resistant member used in silicon and compound semiconductor production processes. The present invention relates to a method for producing an original sintered body.

  In the manufacturing process of silicon semiconductors and compound semiconductors, wafers of silicon, gallium arsenide, sapphire, etc. are generated by generating plasmas of halogen gases such as fluorine and chlorine in each process such as CVD, MOCVD, etching, cleaning, and ashing. There are various plasma processing steps for processing the substrate surface. Since plasma is extremely reactive, materials having excellent plasma resistance are required for apparatus members such as chambers and processing jigs of these plasma processing apparatuses, and are carefully selected and used. In addition, in the manufacturing process of silicon and compound semiconductors, it is extremely important to avoid contamination by impurity metals and particle contamination. For this reason, in the said plasma processing apparatus, in addition to the outstanding plasma resistance, it is also requested | required that it is excellent in anti-contamination property. Furthermore, these device members are each required to have specific performance (characteristics) depending on the use site such as high mechanical strength, high heat resistance, high thermal shock, high heat dissipation, and high dielectric properties. Of course, the low price is also an important option.

As described above, a material excellent in plasma resistance is required for the constituent members of the plasma processing apparatus. However, as a conventional material, yttria (yttrium oxide: Y ₂ O ₃ ) excellent in plasma resistance on a quartz glass surface is used. Is ionized to form a film, or vacuum deposition is performed. Alternatively, a sintered body of alumina (Al ₂ O ₃ ) having excellent plasma resistance is used, but none of them satisfy the required characteristics including plasma resistance.

By the way, it is generally estimated that a compound containing the same halogen element (fluorine, chlorine, bromine, iodine, etc.) is chemically stable in order to have resistance to fluorine-based or chlorine-based so-called halogen-based plasma. Is done. In addition, considering the required characteristics other than the above-mentioned plasma resistance, calcium fluoride (CaF ₂ ) and the like are regarded as candidates for new materials for this device member.

The CaF ₂ is a natural mineral called fluorite. According to the physics and chemistry dictionary, it has a melting point of 1418 ° C, a boiling point of 2500 ° C, a density of 3.18g / cm ³ and a Mohs hardness of 4 belonging to a cubic system. Colorless crystals. For this reason, high-purity single crystals are extremely excellent in light transmittance, and have been conventionally used as optical members such as prisms and lenses. Recently, the transmittance in the vacuum ultraviolet region has been drastically increased due to higher purity and improved crystal structure, and as an optical member using vacuum ultraviolet light as a light source, specifically, an ArF excimer laser with a wavelength of 193 nm is used as the light source. It has come to be used for high-grade optical parts such as lenses for reduction projection exposure machines.

On the other hand, CaF ₂ is also known to be a material with excellent plasma resistance. For example, Japanese Patent No. 3017528 (Patent Document 1) discloses a coating film of CaF _{2 on} an electrode surface made of a material containing Al or stainless steel that is exposed to plasma by a combination of an ion plating method and a vapor deposition method. It is disclosed that an excellent plasma processing apparatus can be obtained by forming the film, improving the plasma resistance, and preventing the electrode from becoming a contamination source. However, for example, it is difficult to uniformly coat CaF ₂ on a member having a large surface area such as a chamber lining material of a plasma processing apparatus, in particular, a member having a large unevenness or a complicated shape or a large product. Even if it was possible to coat, the film had a problem that it was easy to peel off.

Therefore, in order to use CaF ₂ itself as a plasma-resistant member, it is conceivable to grind the high-purity CaF ₂ single crystal used for the optical member as it is to the plasma-resistant member. However, this case has the following various problems. First, in order to produce a high-purity single crystal, it is necessary to use advanced technology to improve the purity of raw materials that require a large number of processing steps, and to grow single crystals in a high-temperature furnace for several months. As a result, enormous manufacturing costs are required and the material becomes extremely expensive. Furthermore, this material is brittle because it is a single crystal, and is easily scratched even by a slight mechanical impact, and may be cracked even by a relatively mild impact. In addition, it is extremely weak against thermal shock and easily cracks, so it requires advanced knowledge and skill. As a result, the processing requires advanced technology and a great number of man-hours, and the processing becomes extremely expensive. Therefore, it was not suitable for practical use for this application.

As described above, there are a number of problems in using the high-purity CaF ₂ single crystal used for the optical member as it is for the plasma-resistant member. An attempt to improve this is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-300777 (the following Patent Document 2), in which high-purity CaF ₂ single crystal pieces such as cutting scraps of CaF ₂ single crystals for optical members are pulverized. It is shown that the obtained powder is used as a starting material to form a dense sintered body by a hot press method using hot pressing.

However, this manufacturing method has the following various problems. First, the problem of impurity contamination arises in the pulverization process of the cutting material of the CaF ₂ single crystal for optical members, which is the original material. It is impossible to pulverize a high-purity original material without causing impurity contamination and use it as a starting material for sintering while maintaining a high purity. In order to use as a starting material for sintering, it is necessary to finely pulverize it into a fine powder. First, the constituent materials of the container and the jig for grinding are worn out and mixed into the starting material. Contamination and environmental pollution caused by handling in the grinding process are considered.

  Furthermore, in order to use the finely pulverized fine powder as a starting material for sintering, a particle size adjustment process is generally required, and coarse particles and fine particles are removed using air classification or sieving. It is necessary to adjust the particle size to a particle size distribution that is easy to sinter into a dense sintered body. Environmental pollution due to handling in this process is inevitable. Impurity contamination progresses as each handling process passes.

  In addition, in the specification of Japanese Patent Application Laid-Open No. 2003-300777 (the following Patent Document 2), this finished sintered body has an X-ray diffraction peak intensity equivalent to the single crystal of the original material from the analysis result of the powder X-ray diffraction method. In addition, it has been explained that it has a peak broadening, and has high single crystallinity. Single crystals are brittle materials and tend to be brittle. In addition, a mold is required in the hot press method using hot press, and distortion is likely to occur inside the sintered body during the cooling process after heat and pressure due to the difference in thermal expansion coefficient between the mold and the sintered body. . Furthermore, single crystals are inherently inferior in impact resistance and sometimes crack. In addition, since the hot press method using hot press is batch processing, it tends to be inferior in productivity and expensive.

JP-A-2004-83362 (Patent Document 3) discloses that a low-purity starting material containing Mg is subjected to a treatment for removing impurities other than Mg using hydrofluoric acid. precipitated high purity CaF _2, which was heat-treated, granulated, and then molded, the invention of a method and a sintered body thereof for producing a sintered body of CaF ₂ containing MgF ₂ is disclosed by sintering ing.
However, in the present invention, the starting material is first of low purity, and therefore the type and concentration of impurities are usually not constant. Therefore, it is necessary to perform analysis each time, and to change the conditions of the purification treatment using hydrofluoric acid according to the starting material. Furthermore, depending on the state of impurities in the starting material, such as the type and concentration of impurities, the precipitation treatment method may not be able to sufficiently purify. For this reason, the intermediate product after the purification treatment becomes unstable in physical properties including purity. In this manufacturing method, the purity can be increased only in this purification treatment step, and as a result, the physical properties of the sintered product as the final product also become unstable. In other words, it is a difficult method to stably obtain a sintered body having good characteristics.

Furthermore, in this production method, the sintering temperature is as low as 800 ° C. at most in both the normal pressure sintering step and the pressure sintering step, and as shown in the CaF ₂ -MgF ₂ binary phase diagram as described later, Since it is not 980 degreeC or more which produces a solid solution, it becomes solid phase sintering by reaction between solid phases. In solid-phase sintering, there is a problem that the bonding force between the particles is weak because the molten phase is not passed, the grain growth is insufficient, and the sintered body becomes weak.

As described above, there are various problems in using a conventional CaF ₂ single-component single crystal body or a sintered body containing CaF ₂ as a main component for a plasma-resistant member.

Japanese Patent No. 3017528 Japanese Unexamined Patent Publication No. 2003-300777 JP 2004-83362 A

Means for solving the problems and their effects

  The present invention has been made in view of the above problems, and has high plasma resistance suitable for various plasma processing processes in which a halogen-based gas plasma is generated in the manufacturing process of a silicon semiconductor or a compound semiconductor to process a wafer surface. Plasma-resistant fluoride that has excellent anti-contamination properties, mechanical strength, heat resistance, thermal shock resistance, heat dissipation, dielectric properties, etc., and does not become a high-priced product like high-purity single crystals It aims at providing the manufacturing method of a sintered compact.

In order to achieve the above object, the method (1) for producing a plasma-resistant fluoride sintered body according to the present invention comprises mixing 1 to 5 wt.% Of high-purity MgF ₂ powder with high-purity CaF ₂ powder and further sintering. A step of adding 0.1 to 1 wt.% Of an auxiliary agent and mixing, a step of molding at a press pressure of 0.2 MPa / cm ² or more using a mold and a press molding machine, and 600 to 600 of the molded product in an air atmosphere. A process of pre-sintering by heating to 700 ° C., heating in a temperature range of 1250 to 1370 ° C. for 6 to 12 hours to form a CaF ₂ -MgF ₂ binary sintered body having a dense structure It is characterized by including a process.

Moreover, the manufacturing method (2) of the plasma-resistant fluoride sintered body according to the present invention replaces the sintered body forming step in the manufacturing method (1) of the plasma-resistant fluoride sintered body with a heating atmosphere. It is characterized by including a step of forming a CaF ₂ -MgF ₂ binary sintered body having a dense structure by heating in a temperature range of 1220 to 1350 ° C. for 6 to 12 hours in an inert gas atmosphere.

Moreover, the manufacturing method (3) of the plasma-resistant fluoride sintered body according to the present invention replaces the sintered body forming step in the manufacturing method (1) of the plasma-resistant fluoride sintered body with a heating atmosphere. It is characterized by including a step of forming a CaF ₂ -MgF ₂ binary sintered body having a dense structure by heating in a temperature range of 1205-1330 ° C. for 6-12 hours under a high vacuum of 10 ⁻² Pa or less. Yes.

  The mechanical strength of the sintered body is the micro-strength of the joint between the particles and the defoamed state such as the size, shape, distribution, number of bubbles, in other words, the joint of the joint and the original particle (matrix). Due to the shape, such as the thickness and length of the material (this is generally referred to as the denseness of the sintered body) and the crystal structure (polycrystalline, single crystal or amorphous) of the matrix It depends on the degree of brittleness.

  The basic technical idea in the present invention is: 1) relaxation of the melt sintering condition by mixing two kinds of starting materials, that is, one kind of simple (in the raw material processing technology area, single and synonymous) 2) This sintering should be mainly melt-sintering by melting reaction, and the sintered body should have a strong inter-particle bonding force. 3) Melt-sintering To make a dense sintered body by optimizing the conditions, 4) to produce a plasma-resistant fluoride sintered body having excellent mechanical strength and the like by the combined use of 2) and 3), It is.

According to the method for producing a plasma-resistant fluoride sintered body according to the present invention, the CaF ₂ -MgF ₂ binary sintered body produces a solid solution in the CaF ₂ -MgF ₂ binary phase diagram shown in FIG. Since sintering is performed at a temperature of 980 ° C. or higher, which is the temperature range, melt sintering is mainly performed by a melt reaction. The sintered body produced by this melt sintering has a strong bonding force between particles, and the mechanical strength (micro strength) of the bonded portion is considerably high. Further, according to the manufacturing method of the present invention, the sintered body, the mixing ratio of CaF ₂ MgF _2, the heating atmosphere, the selection of such heating temperature pattern, a higher denseness. Moreover, according to the manufacturing method according to the present invention, since the base is a sintered body, the crystal structure becomes polycrystalline, and the brittleness is remarkably improved as compared with a single crystal.

It is a phase diagram of CaF ₂ -MgF ₂ binary system. It is a figure which shows the relationship between the heating conditions of a temporary sintering process, and the shrinkage rate of a temporary sintered compact. It is a figure which shows the relationship between the heating conditions of the sintering process in an atmospheric condition, and the production | generation state of a sintered compact. It is a figure which shows the relationship between the heating conditions of the sintering process in argon gas atmosphere, and the production | generation state of a sintered compact. It is a figure which shows the relationship between the heating conditions of a sintering process by ^10-3 Pa in a vacuum atmosphere, and the production | generation state of a sintered compact.

Hereinafter, embodiments of a method for producing a plasma-resistant fluoride sintered body according to the present invention, more specifically, a CaF ₂ -MgF ₂ binary sintered body having a dense structure will be described with reference to the drawings.

The method for producing a plasma-resistant fluoride sintered body according to the present invention comprises 1 to 5 wt.% Of MgF ₂ powder of high purity (purity 99 wt.% Or more) added to CaF ₂ powder of high purity (purity 99 wt.% Or more). In addition, a carboxymethyl cellulose (CMC) solution, for example, as a sintering aid is added to the mixture 100 in an amount of 0.1 to 1 wt. , Using a mold and a press molding machine at a press pressure of 0.2 MPa / cm ² or more, and heating the molded body in an air atmosphere to a temperature range of 600 to 700 ° C. to perform preliminary sintering. The sintered product is heated for a required time in the temperature range where an appropriate amount of solid solution is formed in the air, in an inert atmosphere or in vacuum, and then cooled to produce a CaF ₂ -MgF ₂ binary sintered body having a dense structure. .

The purpose of mixing the MgF ₂ powder as the auxiliary material to CaF ₂ powder of the main raw material, as shown in FIG. 1, (in the figure, 1410 ° C. the drawing) melting point in the CaF ₂ plain is high, and a solid solution Part of the temperature range of formation is not clear in dotted line notation. By mixing MgF ₂ powder, the solid solution generation region on the phase diagram shown in FIG. There is to do.

Ca is the same group of elements in the periodic table, but the periods are adjacent, and MgF ₂ which is a Mg fluorine compound, which is presumed to have similar characteristics, is mixed to lower the melting point and form a solid solution. The temperature conditions can be further clarified (by mixing MgF ₂ , from the dotted line area at the right end of the temperature area display line at the start of solid solution generation in FIG. 1 to the solid line area of the intermediate mixing ratio area located on the left side. As a result, it is easy to optimize the sintering temperature condition.

  For the selection of the sintering aid, two types of CMC and calcium stearate were selected, and the ratio of each was changed, and the effect of these sintering aids was tested. For comparison, a test without using a sintering aid was also performed.

The mixing of the main raw material CaF ₂ and the auxiliary raw material MgF ₂ was carried out by varying the mixing ratio in the range of 0 to 12.5 wt.%. After kneading for half a day with a ball mill, two kinds of sintering aids were added at a mixing ratio of 0 to 2 wt.%, Respectively, and kneaded for a whole day and night using a pot mill to obtain a starting material. The ball mill used was an alumina ball having an inner diameter of 280 mm, a length of 400 mm, and a ball of φ5: 1800 g, φ10: 1700 g, φ20: 3000 g, and φ30: 2800 g. The pot mill was made of alumina and had an inner diameter of 200 mm and a length of 250 mm. The starting material was put into one of the molds having an inner diameter of 160 mm, 265 mm and 375 mm, and press molding was performed by changing the pressing conditions at room temperature using a single screw press. After preliminarily sintering the molded body in the atmosphere at various heating conditions in the range of a heating temperature of 550 to 750 ° C. and a heating time of 3 to 18 hours, and observing the appearance of the temporary sintered body In an air atmosphere, which was expected to have good sintering conditions in a preliminary test, the temperature was raised from room temperature to 1300 ° C. at a constant rate over 6 hours, held at the same temperature for 6 hours, and then cooled to 100 ° C. 6 hours were taken to observe the appearance of the sintered body, the state of internal densification, and the like, and the proper raw material composition, raw material processing conditions and pre-sintering conditions were investigated.

As a result, the mixing ratio of the auxiliary material MgF ₂ in the main raw material CaF ₂ is, 1 wt becomes insufficient densification of the sintered body is less than.%, Probably because the sintering speed is too fast at 5.1 wt.% Or more, In some cases, the appearance of the sintered body, specifically the vicinity of the edge of the outer peripheral portion, melted and the shape collapsed after partial softening. From these facts, the appropriate range of the mixing ratio of MgF ₂ was set to 1 to 5 wt. There was no significant difference in the effect of the two types of sintering aids, but the shape maintenance performance of the molded product was poor without the aid, and when the compounding ratio exceeded 1.1 wt. In some cases, coloration that appears to be a residue of the auxiliaries was observed. For these reasons, the appropriate range of the mixing ratio of the sintering aid is set to 0.1 to 1 wt.

Fragile and the molded body is broken during handling is less than the press pressure of 0.2 MPa / cm ^2, whereas, presintered body in the case of 1 MPa / cm ² a little less than a press pressure of 1.1 MPa / cm ² or more, the sintered body There was no significant difference in performance. For these reasons, the appropriate value of the pressing pressure is set to 0.2 MPa / cm ² or more.

  As shown in FIG. 2, the pre-sintering conditions in the air atmosphere of the molded product showed a slight shrinkage compared to the size of the molded product when the heating temperature was less than 600 ° C., and the shrinkage rate was higher than 701 ° C. Since the shrinkage control becomes difficult quickly, the appropriate range of the pre-sintering temperature was set to 600 to 700 ° C. As shown in FIG. 2, the appropriate value for the heating time was optimal at 10 to 11 hours from the evaluation of the shrinkage rate at 600 ° C., and 6 to 12 hours were appropriate. At 650 ° C., 8 to 10 hours was optimum, and 6 to 12 hours was appropriate. On the other hand, 7 to 8 hours were optimal at 700 ° C., and 6 to 12 hours were appropriate. From this result, the heating conditions for pre-sintering were heating at 600 to 700 ° C. for 6 to 12 hours in an air atmosphere.

  The last step in manufacturing a plasma-resistant fluoride sintered body, and the most likely to affect the performance of the sintered body is the sintering process. Appropriate conditions until just before the sintering process were revealed.

  The sintering mechanism considered desirable for this plasma-resistant fluoride sintered body is as follows. In the raw material mixing, particle size adjustment, kneading, pressing, pre-sintering etc. just before the pre-sintering process, the space between the particles of the pre-sintered body is small, and the space is almost uniformly dispersed without aggregation. (First half of the primary agglomeration process). The heating temperature gradually rises in the temperature rising process of the sintering process, and the temperature starts slightly from 980 ° C., where the aggregation of particles starts from around the pre-sintering temperature range (600 to 700 ° C.) and then the solid solution starts to form. The reaction between solid phases starts from the region (generally, it is said to start from a temperature range of about 10% or more from that temperature), and the aggregation of the particles proceeds along with it, and the distance between the particles is short The gap becomes smaller. However, the voids still remain open pores (second half of the primary aggregation process).

Here, the micro behavior of the raw material particles will be described. It is presumed that the MgF ₂ particles as the auxiliary material are present around the CaF ₂ particles as the main material, and proceed with the interfacial reaction with the CaF ₂ particles. When the heating temperature exceeds 980 ° C., it starts to melt from the interface where the MgF ₂ particles exist, and a solid solution of CaF ₂ —MgF ₂ binary compound begins to be generated. It is thought that this solid solution fills the voids between the particles, and in part, fills the fine voids by capillary action (secondary aggregation process).

  During the secondary agglomeration process, the voids between the particles become smaller, and all or most of the voids are surrounded by particles or solid solution to form closed pores (bubbles) or, depending on the conditions, desorb through the voids (open pores). Gas or gas penetrates into particles or solid solution to degas and does not become bubbles (referred to as defoaming phenomenon). Whether the voids between the particles become closed pores, that is, bubbles, or bubbles are not generated by degassing is a major factor in determining the degree of densification of the sintered body and, consequently, the characteristics of the sintered body. In particular, in sintering in a vacuum state, the capillary phenomenon and the defoaming phenomenon due to this solid solution are promoted, and bubbles are unlikely to remain, and it is considered that densification is easy. In order to densify the whole as described above, it is important that the primary agglomeration process and the secondary agglomeration process are almost uniformly advanced almost simultaneously for each process.

  In the present invention, the preliminary sintering process corresponding to the first half of the primary aggregation process and the sintering process corresponding to the second half of the primary aggregation process and the secondary aggregation process are performed separately. It is easy to proceed almost uniformly. However, if the heating conditions are not appropriate just because the process is divided into temporary sintering and sintering in this way, for example, heating is performed at a temperature exceeding the appropriate range in the preliminary sintering process, or the temperature of the sintering process is increased. When heating is performed rapidly in the temperature stage, or when the holding temperature in the same process is a high temperature exceeding the appropriate range, the degree of densification is significantly different between the outer peripheral portion and the inside of the sintered body. In such a state, degassing becomes difficult during the densification process inside the sintered body, and the internal densification becomes particularly insufficient. Therefore, it is important to optimize the heating temperature pattern in the sintering process according to the size.

  As described above, the proper conditions until immediately before the sintering process have been clarified, and the preliminary sintered product used in this sintering process has already advanced to the first half of the primary aggregation. What is important here is that the entire pre-sintered body has already progressed almost uniformly to the middle of primary aggregation. For this reason, in the sintering process, the remaining primary agglomeration and the secondary agglomeration tend to proceed almost uniformly as a whole.

Here, the appropriate range of the size of the temporary sintered body and the sintering conditions will be described. The size of the temporary sintered body is 152 mm, 253 mm, and 357 mm in outer diameter, and each 20 mm in thickness. The heating atmosphere at the time of sintering was three types: air, inert (argon) gas, and vacuum with a vacuum degree of 10 ⁻² Pa or less.

  Of the heating patterns, first, the temperature rise and fall conditions were preliminarily tested in three cases of 4, 6, and 8 hours, respectively. As a result, small cracks occurred in the sintered body in 4 hours, and the others were good. It was set to 6 hours.

  Regarding the heating holding temperature and the same time, first, the holding temperature was changed in the range of 1100 to 1390 ° C., and the holding time was carried out in 5 cases of 3, 6, 9, 12, and 15 hours. In the atmospheric heating shown in FIG. 3, when the temperature is lower than 1250 ° C., the densification is insufficient regardless of the holding time. On the other hand, when the temperature is 1371 ° C. or higher, the sintering speed is too high and there are many bubbles regardless of the holding time. When the holding time is 15 hours or more, the outer periphery of the sintered body has melted and the appearance shape has collapsed. Therefore, the holding temperature is 1250 to 1370 ° C., and the holding time is 6 to 12 hours. It was judged.

  Next, the heating in an argon gas atmosphere is as shown in FIG. 4, and if it is less than 1220 ° C., it does not depend on the holding time, and if the holding time is 3 hours, the densification is insufficient regardless of the heating temperature. When the temperature is higher than or equal to ° C., the sintering rate is too high regardless of the holding time, and many bubbles are generated regardless of the holding time. It was judged that 1350 ° C. and holding time of 6 to 12 hours were proper conditions.

  The same effect was obtained not only with argon but also with nitrogen, neon, and the like.

  When heating in vacuum, as shown in FIG. 5, if it is less than 1205 ° C., it does not depend on the holding time, and if the holding time is 3 hours, it is insufficiently densified regardless of the heating temperature. Like the heating in the atmosphere, the sintering speed is too high and many bubbles are generated. If the holding time is 15 hours or more, the melt may be melted and the external shape may be destroyed. Therefore, the holding temperature is 1205 to 1330 ° C., the holding time is 6 to 12 hours. Judged to be the proper condition.

  When the heating conditions of this sintering process are in the proper range, the final state of the sintered body is always dense, and obvious defects such as large voids and cracks that are found locally in general ceramic sintered bodies The site was not found in this sintered body.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not restrict | limited by the following Example.

Mix 1.5 wt.% Of the same MgF ₂ powder (average particle size 10 μm, purity 99 wt.% Or more) with high purity CaF ₂ powder (main raw material: average particle size 10 μm, purity 99 wt.% Or more). Kneaded for hours. Thereafter, a carboxymethyl cellulose (CMC) solution as a sintering aid was further added to the mixture 100 at a rate of 0.2 wt.% And mixed for 12 hours in a pot mill as a starting material. Using a 160 mm mold, press molding was performed at a press pressure of 0.9 MPa / cm ² to obtain a molded body. The molded body was pre-sintered at 680 ° C. for 7 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 152 mm and a thickness of 20 mm. It is heated at a constant rate from room temperature to 1365 ° C. for 6 hours in the air atmosphere, held at the same temperature for 6 hours, and then cooled for 6 hours from the take-off temperature and the set temperature drop to 100 ° C., I took it out. The approximate dimensions of the sintered body were an outer diameter of 145 mm, a thickness of 19 mm, and a bulk density of 3.13 g / cm ³ from the appearance and weight, and the sintered state was good. The “bulk density” referred to here is a disk-like appearance of the sintered body, so the bulk volume is calculated from the measured outer diameter and thickness of the disk, and the separately measured weight is the bulk volume. I took the method of dividing by. Hereinafter, it was decided to carry out similarly.

The same main raw material as in Example 1 above was mixed with 2.5 wt.% Of Mg F ₂ powder and kneaded in a ball mill for 12 hours. After that, 0.7 wt.% Of calcium stearate was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 265 mm, a press pressure of 0.5 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 650 ° C. for 10 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 253 mm and a thickness of 20 mm. The temperature was raised from room temperature to 1340 ° C. over 6 hours in an argon gas atmosphere at a constant rate, held at the same temperature for 8 hours, cooled to 100 ° C. over 6 hours, cooled and taken out. The approximate dimensions of the sintered body were an outer diameter of 242 mm, a thickness of 19 mm, and a bulk density of 3.14 g / cm ³ , and the sintered state was good.

The same main raw material as in Example 1 was mixed with 4.5 wt.% MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 1 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a single screw press and a mold with an inner diameter of 375 mm and a press pressure of 0.2 MPa / cm ^2. Was press-molded to obtain a molded body. The molded body was pre-sintered at 620 ° C. for 11 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 357 mm and a thickness of 20 mm. It was heated at a constant rate from room temperature to 1220 ° C. over 6 hours in a vacuum atmosphere of 10 ⁻³ Pa, held at the same temperature for 11 hours, cooled to 100 ° C. over 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 350 mm, a thickness of 19 mm, and a bulk density of 3.11 g / cm ³ , and the sintered state was good.

3 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. After that, 0.6 wt.% Of CMC solution was further added as a sintering aid and mixed in a pot mill for 12 hours as a starting material, using a uniaxial press machine and a mold with an inner diameter of 265 mm, a press pressure of 0.7 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 620 ° C. for 9 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 253 mm and a thickness of 20 mm. The temperature was raised from room temperature to 1320 ° C. over 6 hours in a nitrogen gas atmosphere at a constant rate, held at the same temperature for 7 hours, cooled to 100 ° C. over 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 249 mm, a thickness of 18.5 mm, a bulk density of 3.16 g / cm ³ , and the sintered state was good.

2 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. Then, 3.5 wt.% Calcium stearate as a sintering aid was further added and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 160 mm at a press pressure of 0.6 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 630 ° C. for 10 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 152 mm and a thickness of 20 mm. It was heated at a constant rate from room temperature to 1210 ° C. over 6 hours in a vacuum atmosphere of 10 ⁻⁵ Pa, held at the same temperature for 12 hours, cooled to 100 ° C. over 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 146 mm, a thickness of 18.5 mm, a bulk density of 3.15 g / cm ³ , and the sintered state was good.

The same main raw material as in Example 1 was mixed with 2.5 wt.% Of MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 0.5 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 265 mm and a press pressure of 0.3 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 600 ° C. for 12 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 254 mm and a thickness of 20.5 mm. It was heated at a constant rate from room temperature to 1325 ° C. over 6 hours in an argon gas atmosphere, held at the same temperature for 7 hours, cooled to 100 ° C. over 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 244 mm, a thickness of 19 mm, and a bulk density of 3.12 g / cm ³ , and the sintered state was good.

Comparative Example 1

6 wt.% Of MgF ₂ powder was mixed with the same main raw material as in Example 1 and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 160 mm at a press pressure of 0.9 MPa / cm ² press molding was performed to obtain a molded body. The molded body was pre-sintered at 680 ° C. for 7 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 150 mm and a thickness of 19.5 mm. The temperature was raised from room temperature to 1365 ° C. over 6 hours in an air atmosphere at a constant rate, held at the same temperature for 6 hours, cooled to 100 ° C., the take-out temperature, over 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 140 to 150 mm and a thickness of approximately 16 mm. However, some of the outer peripheral portion melted and collapsed. In addition, the bulk density was in a state where the shape could not be measured because the shape collapsed as described above.

Comparative Example 2

The same main raw material as in Example 1 was mixed with 1.5 wt.% Of MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 160 mm at a press pressure of 0.9 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 750 ° C. for 13 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 147 mm and a thickness of 18 mm. The temperature was raised from room temperature to 1365 ° C. over 6 hours in an air atmosphere at a constant rate, held at the same temperature for 6 hours, cooled to 100 ° C., the take-out temperature, over 6 hours, and taken out. The approximate dimensions of the sintered body were as follows: an outer diameter of 144 to 146 mm, a thickness of approximately 17 mm, and a bulk density of 2.97 g / cm ³ . When the inside of the sintered body was observed, numerous large bubbles having a size of 1 mm or more were present.

Comparative Example 3

The same main raw material powder as in Example 1 was mixed with 1.5 wt.% MgF ₂ powder and kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 160 mm at a press pressure of 0.9 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 680 ° C. for 7 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 152 mm and a thickness of 20 mm. The temperature was raised from room temperature to 1385 ° C. in an air atmosphere at a constant rate for 6 hours, held at the same temperature for 6 hours, cooled to the removal temperature of 100 ° C. for 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 148 to 150 mm and a thickness of approximately 18 mm, but some of the outer periphery melted and collapsed. The bulk density was in a state where the shape was broken and measurement was impossible.

Comparative Example 4

Using the same raw material powder as in Example 1 above, MgF ₂ powder was mixed at 1.5 wt.% And kneaded in a ball mill for 12 hours. After that, 0.2 wt.% Of CMC solution was further added as a sintering aid and mixed for 12 hours in a pot mill as a starting material, using a uniaxial press machine and a mold with an inner diameter of 160 mm at a press pressure of 0.9 MPa / It was press-molded at cm ² to obtain a molded body. The molded body was pre-sintered at 570 ° C. for 8 hours in an air atmosphere to obtain a pre-sintered body having an outer diameter of 159 mm and a thickness of 21 mm. From the appearance, it was in a state where it could be judged that the shrinkage due to pre-sintering was insufficient. The temperature was raised from room temperature to 1365 ° C. over 6 hours in an air atmosphere at a constant rate, held at the same temperature for 6 hours, cooled to 100 ° C., the take-out temperature, over 6 hours, and taken out. The approximate dimensions of the sintered body were an outer diameter of 154 mm, a thickness of 19.5 mm, and some of the outer peripheral edge portions were chipped, so the bulk density was an approximate value, but was about 2.90 g / cm ³ . In addition, a large void (instead of a perfect sphere like a bubble and an indeterminate shape) was observed inside.

Comparative Example 5

Using the same molded body as in Comparative Example 4 above, preliminary sintering was performed in an air atmosphere at 680 ° C. for 7 hours to obtain a temporary sintered body having an outer diameter of 152 mm and a thickness of 20 mm. The temperature was raised from room temperature to 1235 ° C. over 6 hours in an air atmosphere at a constant rate, held at the same temperature for 12 hours, cooled to 100 ° C., the take-out temperature, and cooled for 6 hours. The dimensions of the sintered body were as light as 151 mm in outer diameter, 19 mm in thickness, and 2.89 g / cm ^{3 in} bulk density. When the inside of the sintered body was observed, there were innumerable medium-sized and small bubbles, and the joint part of the base was narrow, so secondary aggregation in the sintering process did not progress sufficiently It was speculated.

Comparative Example 6

  Using the same molded body as in Comparative Example 4 above, preliminary sintering was performed in an air atmosphere at 680 ° C. for 7 hours to obtain a temporary sintered body having an outer diameter of 152 mm and a thickness of 20 mm. The temperature was raised from room temperature to 1360 ° C. over 6 hours in an argon gas atmosphere at a constant rate, held at the same temperature for 6 hours, cooled to 100 ° C., the take-out temperature, over 6 hours, and taken out. As for the appearance of the sintered body, a part of the outer peripheral portion melted and collapsed, and melting was progressing too much. The dimensions were an outer diameter of 152 to 154 mm, a thickness of 17 to 19 mm, and the bulk density was not measurable.

Comparative Example 7

Using the same molded body as in Comparative Example 4 above, preliminary sintering was performed in an air atmosphere at 680 ° C. for 7 hours to obtain a temporary sintered body having an outer diameter of 152 mm and a thickness of 20 mm. It was heated at a constant rate from room temperature to 1340 ° C. over 6 hours in a vacuum atmosphere of 10 ⁻⁴ Pa, held at the same temperature for 7 hours, then cooled to 100 ° C., the take-out temperature, over 6 hours, and taken out. . As for the appearance of the sintered body, a part of the outer peripheral portion melted and collapsed in the same manner as in Comparative Example 6, and the melting progressed too much.

Claims (3)

A method for producing a plasma-resistant fluoride sintered body comprising a CaF ₂ -MgF ₂ binary sintered body having a dense structure,
Step high purity MgF ₂ powder with high-purity CaF ₂ powder 1-5 wt.% Are mixed and mixed for an additional sintering aids 0.1 to 1 wt.% Additive to,
Forming at a press pressure of 0.2 MPa / cm ² or more using a mold and a press molding machine;
A step of heating the molded product to 600 to 700 ° C. in an air atmosphere to perform preliminary sintering,
A step of forming a CaF ₂ -MgF ₂ binary sintered body having a dense structure by heating in an air atmosphere at a temperature range of 1250 to 1370 ° C. for 6 to 12 hours;
The manufacturing method of the plasma-resistant fluoride sintered compact characterized by including this. In place of the CaF ₂ -MgF ₂ binary sintered body forming step according to claim 1, the heating atmosphere is an inert gas atmosphere, and the heating is performed in a temperature range of 1220 to 1350 ° C. for 6 to 12 hours. Including a step of forming a CaF ₂ -MgF ₂ binary sintered body,
The other process is the same as each process of Claim 1, The manufacturing method of the plasma-resistant fluoride sintered compact characterized by the above-mentioned. In place of the sintered body forming step according to claim 1, the heating atmosphere is set to a high vacuum of 10 ⁻² Pa or less, and heated in a temperature range of 120 to 1330 ° C. for 6 to 12 hours to form CaF ₂ -MgF having a dense structure. ₂ including the step of forming a binary sintered body,
The other process is the same as each process of Claim 1, The manufacturing method of the plasma-resistant fluoride sintered compact characterized by the above-mentioned.

Images