WO2014148156A1

WO2014148156A1 - Crucible for growing sapphire monocrystal and method for growing sapphire monocrystal

Info

Publication number: WO2014148156A1
Application number: PCT/JP2014/053296
Authority: WO
Inventors: 大田賀; 聖一星; 博横山
Original assignee: 株式会社アライドマテリアル
Priority date: 2013-03-21
Filing date: 2014-02-13
Publication date: 2014-09-25
Also published as: JP5650869B1; JPWO2014148156A1

Abstract

The problem addressed by the present invention is to provide a crucible that is for growing a sapphire monocrystal and that has a structure that can suppress the contamination of molten sapphire by crucible components. The crucible (1) for growing a sapphire monocrystal is configured from unavoidable impurities and molybdenum, tungsten, or an alloy of molybdenum and tungsten, and has a cylindrical tube shape having a cylindrical tube section (3) and a flat floor (7) provided integrally to one end of the cylindrical tube section (3) with an R section (5) therebetween.

Description

Crucible for growing sapphire single crystal and method for growing sapphire single crystal

The present invention relates to a crucible for growing a sapphire single crystal and a method for growing a sapphire single crystal.

Sapphire single crystal is a material excellent in transmittance and mechanical properties, and is widely used, for example, as an optical material, and has been increasingly used as an epitaxial substrate for GaN growth.

This sapphire single crystal has been conventionally used by using a pulling method (also called Czochralski method, CZ method, etc.) EFG method (Edge-defined.fFilm-fed Growth) method or Kyropoulos method using a crucible made of iridium, tungsten, molybdenum or the like. It was obtained by growing from a seed crystal.

On the other hand, in recent years, sapphire single crystals have been increased in size to improve the yield of sapphire, and the crucible and other devices have been increased in size even in the above-described pulling method.

Therefore, the HEM (Heat-Exchange Method) method has come to be used as a growth method that can cope with an increase in the size of the sapphire single crystal (Non-patent Document 1).

Here, among the crucible materials described above, molybdenum is widely used as a crucible material because it is less expensive than iridium and tungsten (Patent Document 1).

On the other hand, since the melting point of sapphire exceeds 2000 ° C., molybdenum-tungsten alloys in which tungsten is contained in molybdenum are also used (Patent Documents 2 to 4).

In addition, the R part which has a predetermined | prescribed internal angle dimension may be formed in the part which connects the bottom part and side part of a crucible (patent documents 5, 6).

JP 2010-270345 A JP 2011-127150 A JP 2011-127839 A Japanese Patent No. 3917208 Japanese Patent Laid-Open No. 11-169993 JP 2001-323302 A

However, in the crucible described in the above document, molten alumina erodes the molybdenum crystal grain boundary, and as a result, molybdenum particles of the order of several tens of μm to mm fall off and enter the sapphire crystal, thereby coloring the sapphire crystal. In some cases, the crystallinity is deteriorated.

The present invention has been made in view of the above problems, and an object thereof is to provide a crucible for growing a sapphire single crystal having a structure capable of suppressing mixing of crucible components into dissolved sapphire.

In order to solve the above-mentioned problems, the present inventor examined again the conditions necessary for the crucible capable of suppressing the mixing of the crucible components into the melted sapphire, particularly the shape of the inner peripheral surface of the crucible in contact with sapphire.

At this time, the inventor of the present invention paid attention to the shape of the R portion that connects the cylindrical portion and the flat bottom portion in an equal-thickness cylindrical crucible.

The shape of the R part is desirably larger to some extent from the viewpoint of workability when manufacturing a crucible.

On the other hand, of the grown sapphire single crystal, the portion corresponding to the R portion is different from the portion corresponding to the cylindrical portion in size and shape, and is therefore discarded when a wafer or the like is cut out from the sapphire single crystal. Part.

Therefore, as a crucible for growing a sapphire single crystal, it has been conventionally considered that a sapphire single crystal can be manufactured with a high yield when the R portion is as small as possible.

However, as a result of further investigations, the present inventor can suppress the mixing of the crucible component into the melted sapphire by increasing the R portion to a certain size, and can improve the yield. The inventors have found that this is possible and have come to make the present invention.

That is, the first aspect of the present invention is composed of molybdenum or tungsten, or an alloy of molybdenum and tungsten, and inevitable impurities, and is integrated with the cylindrical portion and one end portion of the cylindrical portion via the R portion. A crucible for growing a sapphire single crystal, wherein the crucible has a flat bottom and an inner angle dimension of the R portion is 20 mm or more and 40 mm or less.

A second aspect of the present invention is a sapphire single crystal growth method using the sapphire single crystal growth crucible described in the first aspect.

According to the present invention, it is possible to provide a crucible for growing a sapphire single crystal having a structure capable of suppressing mixing of crucible components into dissolved sapphire.

It is sectional drawing which shows the crucible 1 for sapphire single crystal growth. It is a flowchart which shows an example of the manufacturing method of the crucible 1 for sapphire single crystal growth.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

First, the shape of the sapphire single crystal growing crucible 1 according to the embodiment of the present invention will be described with reference to FIG.

Here, as the crucible 1 for growing a sapphire single crystal, a crucible for growing a single crystal using a CZ method, an EFG method or the like is illustrated.

As shown in FIG. 1, the crucible 1 for growing a sapphire single crystal has a cylindrical portion 3 and a flat bottom 7 that is integrally provided at one end of the cylindrical portion 3 with an R portion 5 without a joint. It is a uniform cylindrical shape.

Hereinafter, the shape and composition of the members constituting the crucible 1 for growing a sapphire single crystal and the method for producing the crucible 1 for growing a sapphire single crystal will be described.

<Material>
As a material constituting the sapphire single crystal growing crucible 1, molybdenum, tungsten, or an alloy of molybdenum and tungsten is preferably used as a metal material that can withstand the melting temperature of sapphire (alumina) and has high strength.

When an alloy of molybdenum and tungsten is used, tungsten and molybdenum can form a solid solution type alloy. Examples of alloys include 90 mass% molybdenum-10 mass% tungsten alloy (abbreviation 9 MW), 70 mass% molybdenum-30 mass% tungsten alloy (7 MW), 50 mass% molybdenum-50 mass% tungsten alloy (5 MW), and the like. is there.

When molybdenum is contained in molybdenum, the minimum tungsten content necessary for exhibiting the effect of alloying is 5% by mass. Therefore, the tungsten content is preferably at least 5% by mass.

On the other hand, if the tungsten content exceeds 50% by mass, the characteristics are very similar to those of tungsten, so the technical significance of the alloy is lost. Therefore, the upper limit of the alloy amount is 50% by mass.

Also, the purity of the above material is preferably 99.9% by mass or more, and the remainder is inevitable impurities. This is because erosion of the molten sapphire on the inner surface of the crucible is unavoidable, but a high-purity material of this level requires very little impurity contamination, and problems such as coloring can be avoided.

In addition, the purity here is based on the analysis based on tungsten-molybdenum industry association standard (TMIAS) standard number 0001 (tungsten powder and molybdenum analysis method).

<Cylindrical part 3 and flat bottom 7>
The cylindrical portion 3 has an inner diameter (opening portion diameter D) corresponding to the diameter of the sapphire single crystal wafer to be grown. The diameter of the wafer includes a 4-inch wafer and a 6-inch wafer. In order to cope with these wafer sizes, it is desirable that at least the opening diameter D of the crucible is 200 mm. Further, in the future, it is predicted that a crucible having an opening diameter of 400 mm and a crucible having an opening diameter of 660 mm will be generated. Therefore, the opening diameter D is in a range where a range of 200 mm or more and 660 mm or less is assumed. is there.
The flat bottom 7 is a bottom portion having a flat shape.

Here, it is desirable that the cylindrical portion 3 and the flat bottom 7 have a thickness of 5 mm or more and 15 mm or less. For example, the weight of a sapphire ingot is about 25 kg for a diameter of 200 mm and a height of 200 mm, and about 85 kg for a diameter of 300 mm and a height of 300 mm. However, increasing the thickness of the crucible is one measure. This is because the thickness needs to be increased as the diameter of the crucible opening increases, so that it needs to be at least 5 mm.

On the other hand, when the thickness is increased, the weight of the crucible increases. For example, the weight of a molybdenum crucible having an opening diameter of 300 mm, a height of 300 mm, and a thickness of 15 mm is about 55 kg. If the weight exceeds this value, the load-carrying countermeasures of the crystal growth apparatus become large, so the thickness is preferably 15 mm or less.

<R part 5>
The R portion 5 is a portion that connects the cylindrical portion 3 and the flat bottom 7, and the cross-sectional shape parallel to the axial direction of the crucible has an arc shape.

As described above, the present inventors have found that mixing the crucible component into the melted sapphire can be suppressed by setting the inner angle dimension 5a (arc radius) of the R portion 5 within a predetermined range.

Specifically, by setting the inner angle dimension 5a of the R portion 5 to 20 mm or more and 40 mm or less, it is possible to suppress the metal particles constituting the R portion 5 from dropping out and mixing into the sapphire crystal during sapphire growth. Become.

The reason why the crucible component is prevented from being mixed into the dissolved sapphire by setting the inner angle dimension 5a of the R portion 5 within the above range is considered as follows.

That is, sapphire melted in the crucible is a high-temperature fluid, but when the inner angle dimension 5a of the R portion 5 is less than 20 mm, the convection of sapphire during melting is not smooth, so the temperature in the R portion 5 is other than that. It is considered that a so-called “heat pool”, which is higher than the portion, occurs, and the metal particles constituting the crucible component of the R portion 5 drop off and enter the sapphire crystal.

Alternatively, when the inner angle dimension 5a of the R part 5 is less than 20 mm, the convection is turbulent in the R part 5 and the sapphire solution vortex becomes more intense than the others, which is considered to promote erosion.

On the other hand, by setting the inner angle dimension 5a of the R portion 5 to 20 mm or more, the heat accumulation is eliminated and the turbulent flow of the molten sapphire is suppressed, so that mixing of the crucible component into the dissolved sapphire is suppressed. Conceivable.
Therefore, it is desirable that the inner angle dimension 5a of the R portion 5 is 20 mm or more.

If the internal angle dimension 5a of the R portion 5 exceeds 40 mm, the crucible shape becomes a shape close to a round bottom instead of a flat bottom, and the portion discarded when cutting a wafer or the like from a sapphire single crystal increases, resulting in a deterioration in yield. In addition, the convection of the molten sapphire is different from that of a flat bottom, and mixing of crucible components may not be suppressed, which is not preferable.

<Surface shape>
The surface shape of the sapphire single crystal growth crucible 1 is desirably a shape capable of suppressing the mixing of the crucible components into the melted sapphire. Specifically, the inner circumference in contact with sapphire is Ry 7 μm or less and Ra 1 μm or less. Is desirable.

とする By making the inner circumference within the range, mixing of the crucible components into the dissolved sapphire can be suppressed. Furthermore, since the surface of the sapphire crystal after growth becomes smooth and can be seen through the inside, defects can be easily confirmed, and an effect that a high-quality crystal can be provided is also produced.

<H / D>
In the crucible 1 for sapphire single crystal growth of the present invention, it is desirable that H / D, which is a ratio of the crucible height (H) and the opening diameter (D), is 1.4 or less. From the standpoint of sapphire crystal growth, a tall crucible is advantageous for the production of a larger ingot, but from the viewpoint of the design and production of growth equipment, a tall crucible has an external heating structure and arrangement, This is because there are many problems such as the vertical holding structure of the crucible, and on the other hand, from the standpoint of crucible production, there are restrictions on the molding technology into the crucible shape.
Therefore, the limit of H / D is 1.4.

<Manufacturing method>
The method for producing the sapphire single crystal growth crucible 1 is not particularly limited as long as the sapphire single crystal growth crucible having the above-mentioned shape and composition can be produced. Examples thereof are as follows. be able to.
Hereinafter, an example of the manufacturing method will be described with reference to FIG.

(S1: Preparation of raw materials)
First, raw materials for the crucible are prepared.
Specifically, when pure molybdenum is used as the material for the sapphire single crystal growth crucible 1, the raw material is a molybdenum powder having an Fsss (Fisher Sub-Sieve Sizer) particle size of 4 to 5 μm and a purity of 99.9% by mass or more. It is desirable to use

On the other hand, when a tungsten-molybdenum alloy is used, a tungsten powder having a Fsss particle size of 2 to 3 μm and a purity of 99.9% by mass or more as a raw material for the crucible, and a molybdenum having a Fsss particle size of 4 to 5 μm and a purity of 99.9% by mass or more. The powder is weighed at the desired alloy weight ratio. Typical alloy types are 90 mass% Mo-10 mass% W (abbreviated as 9 MW), 70 mass% Mo-30 mass% W (7 MW), 50 mass% Mo-50 mass% W (5 MW). .

Furthermore, when using pure tungsten, it is desirable to use a tungsten powder having a Fsss particle size of 2 to 3 μm and a purity of 99.9% by mass or more.

(S2: mixing of raw materials)
Next, when a tungsten-molybdenum alloy is used as the material for the sapphire single crystal growth crucible 1, the two kinds of measured powders are used with an appropriate apparatus (for example, a ball mill, a V-type mixer, a double cone mixer, etc.). Mix to make raw material powder for alloy.

When pure molybdenum or pure tungsten is used as the material for the sapphire single crystal growth crucible 1, it is not necessary to mix the raw materials.

(S3: Raw material molding)
Next, the raw material powder is filled into a rubber having the shape of a desired molded body, the open port is sealed with a stopper, and then the rubber is evacuated. After the evacuation is completed, the rubber is loaded into a CIP (Cold Isostatic Pressing) apparatus and molded by applying water pressure according to a predetermined procedure. After depressurization, the rubber is taken out from the CIP device to wipe off moisture on the surface, the stopper is opened, and the powder compact is taken out.

(S4: Raw material sintering)
Next, the powder compact is sintered at 2000 ° C. or higher for 20 hours in a batch type or continuous hydrogen sintering furnace. A higher temperature and longer sintering treatment is preferable for improving the sintered density. For example, when the crucible shape is formed with a spatula, the sintered material is a plate-like sintered body having a thickness of 30 mm, a width of 300 mm, a length of 300 mm, and a weight of about 28 kg. When the crucible shape is formed by sintering, Is a crucible-shaped sintered body.

In sintering, it is desirable that the theoretical density ratio of the obtained sintered body is 95% or more. This is because if the theoretical density ratio is 95% or more, the densification of the powder particles proceeds, or the high-density strength is improved by high densification due to plastic deformation, and the erosion resistance is further improved. The theoretical density ratio here means a value obtained by measurement by the Archimedes method.
In the case of an as-sintered crucible (a crucible without surface polishing), the crucible is completed here.

(S5: Plastic working)
When processing the crucible shape with a spatula drawing, the processing described in S5 to S7 below is performed.
Specifically, first, plate rolling is performed on a plate-like sintered body obtained by sintering with a four-stage hot rolling mill. In this plastic working process by hot rolling, the blank material and the quality of the crucible after drawing are created. At this time, a rolling material suitable for drawing with a theoretical density ratio of 98% or more can be obtained by devising the pass schedule (drop rate, heating temperature × time, threading direction, etc.).

(S6: Surface oxide removal treatment)
The above-described hot-rolled material has an oxidized surface and is covered with a light yellow or dark oxide. Therefore, after reducing the surface oxide at a temperature of 900 ° C. using a hydrogen reduction furnace, this is dissolved and removed with a strong acid to form the surface of the metal background. The rolled sheet is cut by an appropriate cutting method such as discharge wire cutting or plasma cutting to obtain a disk-shaped blank for drawing.

(S7: Spatula stop)
Next, in order to process the blank material into a crucible shape, spatula drawing is performed.
Specifically, a mold is set on a spatula squeezing device, a blank material is pressed against this, and the blank material is fixed with a push bar. Next, in this state, the mold, the blank material, and the push rod are integrally rotated. Further, while heating the blank material in the air to the extent of red heat, the roller (spar) is drawn out and the same surface oxide removal treatment as that in S6 is performed to obtain a crucible with a metal background.

(S8: Molding process)
The obtained crucible is subjected to finishing processing by cutting and polishing into product dimensions and shapes using cutting tools. A lathe or machining center is used for cutting.

(S9: Electropolishing process)
When oxidative discoloration is recognized on the surface during the molding process, first, the surface of the metal background is brought out by the same treatment as S6 (surface oxide removal treatment). Thereafter, blasting is performed and preparation for electrolytic polishing is performed. In the cutting finish, a pattern such as bite remains, so blasting is performed. The same effect can be obtained by either dry or wet blasting. The electrolytic polishing process is performed only on the inner surface of the crucible. As a result of the blast treatment and the electropolishing treatment, a crucible product having a surface roughness of Ry 7 μm or less and Ra 1 μm or less is completed.

S8: When the surface roughness is obtained by molding, one or both of the blasting process and the electrolytic polishing process may be omitted.
The above is an example of the manufacturing method of the crucible 1 for sapphire single crystal growth.

Thus, according to the present embodiment, the crucible 1 for growing a sapphire single crystal is composed of molybdenum, tungsten, or an alloy of molybdenum and tungsten and an inevitable impurity, and includes a cylindrical portion 3 and one end portion of the cylindrical portion 3. The inner portion 5a of the R portion 5 has a flat bottom 7 which is integrally provided through the R portion 5 without a joint, and the inner angle dimension 5a of the R portion 5 is 20 mm or more and 40 mm or less.

Therefore, the crucible 1 for growing a sapphire single crystal has a structure capable of suppressing mixing of crucible components into the dissolved sapphire.

Hereinafter, the present invention will be described more specifically based on examples.

(Example 1)
An attempt was made to produce a crucible 1 for growing a sapphire single crystal of a 9 MW alloy (theoretical density: 10.70 g / cm ³ ) by sintering. The specific procedure is as follows.

First, 4.2 kg of tungsten powder having an Fsss particle size of 2.3 μm and a purity of 99.9% by mass and 37.8 kg of molybdenum powder having an Fsss particle size of 4.3 μm and a purity of 99.9% by mass were measured using a V-type mixer. By mixing for 1 hour, 42 kg of tungsten-molybdenum mixed powder was obtained.

Next, set a metal core in the center of the rubber for crucible molding, fill the space between the rubber and the core with the tungsten-molybdenum mixed powder, and further cover the upper end of the core thickly The mixed powder was filled.

After sealing the rubber with a stopper, the inside of the rubber was evacuated for about 30 minutes to confirm that there was no air leak. The rubber surface was washed with water to remove the adhering powders, and then inserted into a CIP apparatus and subjected to hydrostatic pressure. After holding at a pressure of ² ton / cm ² for about 10 minutes, the pressure was released and the CIP molding operation was completed. After removing the rubber from the CIP apparatus and wiping and removing the moisture on the surface, the stopper was removed and opened. Thereafter, a crucible-shaped tungsten-molybdenum mixed powder molded body was taken out from the rubber, and burrs and protrusions were removed by sanding or the like.

Next, the molded body is inserted into a hydrogen sintering furnace, sintered at 2000 ° C. for 20 hours, and a tungsten-molybdenum alloy sintered crucible material having a specific gravity of about 10.2 (theoretical density ratio of about 95%). Got. Furthermore, the sintered crucible material was made into the required shape and dimensions by cutting such as a lathe.

Next, the obtained crucible was placed in a wet blasting apparatus, and surface treatment was performed by spraying alumina abrasive grains (particle size 100 mesh) on the inner and outer surfaces. Thereafter, the abrasive grains remaining on the crucible surface were removed with jet water and dried. Furthermore, after the dried crucible is placed in the electrolyte bath and filled with the electrolyte solution, a negative electrode material is placed in the electrolyte solution inside the crucible, and electrical connection is made so that the crucible becomes a positive electrode. Applied to start electropolishing. After processing for about 1 hour, the connection was removed, the electrode was removed, the chemical solution was discharged, and the crucible was taken out from the liquid bath. Further, the crucible was placed in a neutralization chemical solution tank and neutralized with the adhering chemical solution, and then washed with water, washed with hot water and dried to finish a product crucible.

By changing the powder mixing ratio, a 7 MW alloy (theoretical density of 11.88 g / cm ³ ) crucible and a 5 MW (theoretical density of 13.35 g / cm ³ ) crucible can be manufactured in the same procedure. Further, by using pure tungsten and pure molybdenum as raw materials, a tungsten crucible and molybdenum can be obtained in the same manner.

(Example 2)
A 9 MW alloy crucible having an opening diameter of 300 mm, a height of 300 mm, and a thickness of 10 mm was manufactured by a spatula drawing. The specific procedure is as follows.

First, a mixed powder was prepared in the same manner as in Example 1. Next, CIP molding was performed on the mixed powder. Here, in the case of the spatula drawing method, a blank material is produced by performing plastic working such as rolling on the molded body after sintering. The other conditions were the same as in Example 1. Next, sintering was performed in the same manner as in Example 1 to obtain a sintered alloy sintered material for rolling (theoretical density ratio: about 95%) having a thickness of 30 mm, a length and width of 370 mm, and a specific gravity of about 10.2.

By changing the powder mixing ratio, a 7 MW alloy (theoretical density 11.88 g / cm ³ ) crucible and a 5 MW (theoretical density 13.35 g / cm ³ ) crucible were prepared in the same procedure, and the theoretical density ratio was about 95%. An alloy sintered material for rolling was obtained. A blank material for tungsten crucible and a blank material for molybdenum can be obtained in the same manner.

Next, the sintered material was rolled using a four-high rolling mill for hot rolling. At this time, the size of the blank material necessary for molding into a crucible having an opening diameter of 300 mm, a height of 300 mm, and a thickness of 10 mm was set to a thickness of 12 mm and a diameter of 550 mm, and was executed based on a rolling schedule. First, a sintered body heated to 1400 ° C. in a hydrogen furnace is rolled out to about 570 mm and hot-rolled, then the rolling direction is changed, and finally the heating temperature is lowered appropriately to 800 ° C. Unidirectional rolling was repeated to obtain a hot-rolled cross-rolled alloy sheet having a thickness of approximately 12 mm, a width of 570 mm, and a length of 570 mm.

The reason why rolling is performed while lowering the heating temperature is to prevent a recrystallization phenomenon that occurs during rolling. Next, the alloy plate whose surface is covered with a light yellow oxide is inserted into a hydrogen annealing furnace for annealing heat treatment maintained at 930 ° C., heated and maintained for about 30 minutes, and then placed in a hydrogen atmosphere cooling zone. It was moved, cooled to room temperature, and taken out of the furnace. After this treatment, the reduced surface deposits were dissolved and removed in strong acid, washed with water and dried to obtain an alloy plate with a flat alloy background.

Here, in order to investigate the density and purity of this alloy plate, an end material having a thickness of 12 mm and a length and width of 10 mm was cut out by a discharge wire cutting machine and subjected to measurement. As a result, a theoretical density ratio of 99.1% (specific gravity of 10. 60) and the purity was 99.9% by mass.

Further, as a result of producing a 7 MW alloy plate in the same procedure, a rolled plate having a theoretical density ratio of 99.5% (specific gravity of 11.82) and a purity of 99.9% by mass was obtained.

Similarly, a 5 MW alloy sheet obtained a rolled sheet having a theoretical density ratio of 98.9% (specific gravity: 13.20) and a purity of 99.9% by mass.

In addition, when pure tungsten was used, a rolled plate having a theoretical density ratio of 98.9% (specific gravity 19.09, purity 99.9% by mass) was obtained.

Furthermore, when pure molybdenum was used, a rolled sheet having a theoretical density ratio of 99.1% (specific gravity of 10.11) and a purity of 99.9% by mass was obtained.

Next, a blank material to be subjected to spatula drawing was cut out from the obtained rolled plate to a thickness of 12 mm and a diameter of 550 mm with a discharge wire cutting machine. This blank material is applied to the portion corresponding to the bottom of the drawing type crucible attached to the spatula drawing machine, and the blank material is fixed with a push rod while taking out the center of rotation. While the drawing die / blank material / push bar integrated in series are simultaneously rotated, the blank material is heated to a red hot state of 600 ° C. to 700 ° C. with a burner. In this state, the roller (spar) was drawn out and formed into a crucible shape following the drawing die.

Among the defects that occur during spatula drawing, the phenomenon caused by the characteristics and quality of the blank material is caused by intragranular cracks that appear during the work to follow the dimensions and shape of the outer angle close to the bottom, and the opening at the time that is close to the end of processing. Are layered delamination and intergranular cracking. These are mainly caused by low blank material strength and crystal grain size. In order to increase the material strength, it can be achieved by increasing the density by performing plastic working on the powder sintered material to the strength. As for the influence of crystal size, if the particle size is about 10 μm to 50 μm, the material strength is high and it can withstand deformation, but if it is a coarse particle of about 300 μm to 500 μm, it is too low to endure deformation and breaks.

The obtained crucible having an opening diameter of 300 mm and a height of 300 mm was inserted into a hydrogen annealing furnace for annealing and heat treatment, and the surface oxide film was reduced, followed by dissolution / removal of surface deposits in a strong acid solution. A rough crucible with an alloy background was obtained.

The above-mentioned sintered crucible material or rough crucible was set on a lathe and processed into a desired shape and size with a cutting blade to obtain a cutting finished crucible.

The crucible 1 for growing a sapphire single crystal using a spatula drawing process could be manufactured by the above procedure.

(Example 3)
In order to confirm the effect of reducing the erosion due to the alumina inside the wall, which is influenced by the inner angle dimension of the R portion 5, 9 MW alloy and pure molybdenum are used as materials, the opening diameter is 300 mm, and the height is the same as in Example 1. A crucible with 300 mm, a thickness of 10 mm, and an internal angle dimension of the R portion 5 of 10 mm, 20 mm, 30 mm, 40 mm, and 50 mm, respectively, is prepared for sapphire growth, and the degree of erosion is evaluated by measuring the coloration and thickness change did.

Sapphire growth was performed at 2150 ° C. using a sapphire growth apparatus, and sapphire growth was repeated 10 times.

The observation site of the thickness change was performed in a portion where the wall portion where the most erosion occurred was transferred to the R portion 5. The size of the crucible before use was measured with a three-dimensional shape measuring instrument (Faro-Edge), and the crucible after 10 uses was broken at the time of disposal and measured with an optical microscope.

In addition, in the evaluation of coloring, when a crucible component is mixed in sapphire that is originally transparent, discoloration to a slightly grayish black or grayish black color is observed, so coloring is normal when the grown sapphire is transparent When discoloration was observed, it was determined that the crucible component was mixed.

The inner surface of the crucible was subjected to the same electrolytic polishing treatment as in Example 1 and subjected to an erosion experiment. The results are shown in Tables 1 and 2. Table 1 shows the results when a 9 MW alloy was used as the crucible material, and Table 2 shows the results when pure molybdenum was used.

As is clear from Tables 1 and 2, when the inner angle dimension of the R part 5 is 10 mm, the thickness of the R part 5 of the crucible after use is greatly reduced as compared with other dimensions. The sapphire was also colored. Therefore, it is considered that the R portion 5 was eroded and the crucible component was mixed in sapphire.

On the other hand, when the inner angle dimension of the R portion 5 was 20 mm, there was no significant change in the thickness of the R portion 5 before and after use, and no coloring was observed.

In addition, when the inner angle dimension of the R portion 5 was 20 mm or more, the change in thickness and the presence or absence of coloring were the same as in the case of 20 mm. However, in the case of 50 mm, as described above, the effective diameter of the obtained sapphire single crystal becomes small, and deterioration of the yield of sapphire becomes a problem.

In addition, the same result was obtained also in 7MW alloy, 5MW alloy, and pure tungsten.

Therefore, it was found that by setting the inner angle dimension of the R portion 5 to 20 mm or more, the erosion of the R portion 5 can be prevented, and mixing of crucible components into sapphire can be suppressed.

Example 4
A 9 MW, 7 MW, and 5 MW alloy crucible with an inner angle dimension of the R portion 5 of 30 mm was manufactured in the same procedure as in Example 3. In order to investigate the influence of the surface roughness on the sapphire coloring, an electrolytic polishing treatment was performed in the same procedure as described above. The crucible was installed in a wet blasting apparatus, and alumina abrasive grains (particle size 100 mesh) were sprayed on the inner and outer surfaces to perform surface treatment. After blasting, the abrasive grains remaining on the crucible surface were removed with jet water and dried.

Next, after installing the crucible in the electrolyte bath and filling the electrolyte solution, place a negative electrode material in the electrolyte solution inside the crucible, make electrical connection so that the crucible becomes a positive electrode, and apply voltage. Start electropolishing. After processing for about 1 hour, the connection is removed, the electrode is removed, the chemical solution is discharged, and the crucible is taken out from the liquid bath. The crucible was placed in a neutralization chemical solution tank, neutralized with the adhering chemical solution, then washed with water, washed with hot water, and dried.

The electrolytic polishing conditions were the following two types A and B, respectively.
Condition A: Voltage 35 V, current density 300 mA / cm ² , polishing time 60 minutes Condition B: Voltage 35 V, current density 1300 mA / cm ² , polishing time 30 minutes

Next, as a comparative example, a 9 MW alloy crucible in which the inner angle dimension of the R portion 5 was 30 mm was manufactured under the same conditions as the electrolytic polishing conditions: voltage 35V, current density 1500 mA / cm ² , polishing time 30 minutes, and other conditions. .

The prepared crucible was used to dissolve sapphire using the same sapphire growing apparatus as in Example 3 and held at 2150 ° C. for 50 hours, and then the sapphire was taken out and the presence or absence of coloring was observed in the same manner as in Example 3. .

The above results are shown in Table 3. Note that “Invention A” in Table 3 corresponds to the case where electrolytic polishing is performed under condition A, and “Invention B” corresponds to the case where electrolytic polishing is performed under condition B.

When the maximum surface roughness height Ry was 7 μm or less and the arithmetic average roughness Ra was 1.0 μm or less, the obtained sapphire ingot was not colored and was a normal sapphire ingot.

As mentioned above, although this invention was demonstrated based on embodiment and an Example, this invention is not limited to above-described embodiment.

It will be understood by those skilled in the art that various modifications and improvements are conceived within the scope of the present invention, and these are also within the scope of the present invention.

This application claims its benefit on the basis of priority from Japanese Patent Application No. 2013-57840 filed on March 21, 2013, the disclosure of which is hereby incorporated by reference in its entirety. Capture as.

1: Crucible for sapphire single crystal growth 3: Cylindrical part 5: R part 5a: Inner angle dimension 7: Flat bottom

Claims

Consists of molybdenum or tungsten, or an alloy of molybdenum and tungsten and inevitable impurities,
A cylindrical portion having a cylindrical portion and a flat bottom integrally provided at one end of the cylindrical portion via an R portion;
A crucible for growing a sapphire single crystal, wherein an inner angle dimension of the R portion is 20 mm or more and 40 mm or less.
The crucible for growing a sapphire single crystal according to claim 1, wherein the cylindrical part has an opening diameter of 200 mm or more and 660 mm or less.
The cylindrical portion is an equal thickness cylindrical shape,
The crucible for growing a sapphire single crystal according to claim 1 or 2, wherein the flat bottom is integrally provided at one end of the cylindrical portion via an R portion without a joint.
The crucible for growing a sapphire single crystal according to any one of claims 1 to 3, comprising a tungsten-molybdenum alloy containing 5 mass% or more and 50 mass% or less of tungsten and unavoidable impurities.
The crucible for growing a sapphire single crystal according to any one of claims 1 to 4, wherein at least the maximum height Ry of the inner circumference is 7 µm or less.
6. The crucible for growing a sapphire single crystal according to any one of claims 1 to 5, wherein the arithmetic average roughness Ra of at least the inner circumference is 1 μm or less.
The sapphire single crystal growth crucible according to any one of claims 1 to 6, wherein a ratio of height / opening diameter is 1.4 or less.
The sapphire single crystal growth crucible according to any one of claims 1 to 7, which has a theoretical density ratio of 95% or more and a purity of 99.9% by mass or more.
The sapphire single crystal growth crucible according to any one of claims 1 to 8, which is formed by a powder sintering method or a spatula drawing method.
A sapphire single crystal growth method using the sapphire single crystal growth crucible according to any one of claims 1 to 9.