JP6014237B1 - Sapphire single crystal member manufacturing equipment - Google Patents

Abstract

A structure for connecting a graphite heater and an electrode disposed so as to surround an outer peripheral surface of a crucible is simple, and a graphite heater can be supported and fixed stably for a long period of time. Cylindrical graphite which surrounds the outer peripheral surface side of the crucible disposed in the containment vessel, is disposed so that the central axis is parallel to the vertical direction, and is provided with a heater side screw hole 132 on the bottom surface 130BT. A graphite rod-like shape having a heater 130 and an end surface 140TP provided with electrode-side screw holes 142, and having an end surface 140TP connected to the bottom surface 130BT of the graphite heater 130 so that the central axis is parallel to the vertical direction. The electrode 140 and the graphite screw 150 which is screwed into the heater-side screw hole 132 and the electrode-side screw hole 142 are at least provided, and the bottom surface 130BT of the graphite heater 130 and the end surface 140TP of the graphite rod-shaped electrode 140 are in the vertical direction. A sapphire single crystal member manufacturing apparatus orthogonal to each other. [Selection] Figure 2

Description

  The present invention relates to a sapphire single crystal member manufacturing apparatus.

  In a single crystal member manufacturing apparatus used for manufacturing various single crystal members such as a sapphire substrate and a silicon wafer, a resistance heating element such as a graphite heater is used to heat and dissolve the raw material charged in the crucible ( Patent Documents 1 to 3). Moreover, in order to prevent the convection of the melt in the crucible together with the resistance heating element, a coil may be further used as a magnetic field application device that applies a magnetic field to the melt (Patent Document 1).

  In the single crystal member manufacturing apparatus shown in Patent Document 1, the lower end of a graphite heater arranged so as to surround the outer peripheral surface of the crucible is fixed to the upper surface of a plate-like fixing member via a mounting bolt. The fixing member is fixed on the base of the single crystal member manufacturing apparatus. Furthermore, an electrode is attached to the through-hole provided in this fixing member. And, by providing a carbonized or graphitized adhesive layer between the graphite heater and the fixing member, both are firmly fixed, and the relative movement between the graphite heater and the fixing member causing discharge is suppressed. In addition, gaps are prevented from occurring.

  Patent Document 2 discloses a cage-shaped graphite heating element, a graphite joint that is connected to the outer peripheral side of the bottom surface of the graphite heating element and extends to the outer peripheral side of the graphite heating element, and an outer peripheral side bottom surface of the graphite joint. There is disclosed a conductive structure including an extremely short graphite electrode connected to a copper electrode and a copper electrode connected to the bottom side of the graphite electrode. In this conductive structure, (1) a graphite heating element and a graphite joint are fixed with a bolt made of a C / C composite material (carbon fiber reinforced carbon composite material) having a tensile strength of 98 MPa, (2 ) The graphite joint and the graphite electrode are fixed with a graphite bolt having a tensile strength of 30 MPa. (3) The graphite electrode and the copper electrode are fixed via a male screw portion provided at one end of the copper electrode. Furthermore, the graphite sheet is arrange | positioned at the interface of each member shown to (1)-(3).

  Moreover, in the single crystal member manufacturing apparatus shown in Patent Document 3, a columnar heater electrode is connected to the lower end side of the outer peripheral surface of the graphite heater disposed so as to surround the outer peripheral surface of the crucible. That is, the graphite heater is supported and fixed by the cylindrical heater electrode.

Japanese Utility Model Publication No. 3-53791 JP 7-288178 A JP 2010-120831 A

  However, in the conventional single crystal member manufacturing apparatus as exemplified in Patent Documents 1 and 2, the structure for connecting the heater and the electrode arranged so as to surround the outer peripheral surface of the crucible is complicated, or for a long time. It is difficult to stably support and fix the heater.

  The present invention has been made in view of the above circumstances, and has a simple structure for connecting between a graphite heater and an electrode arranged so as to surround the outer peripheral surface of the crucible, and stably for a long period of time. It is an object of the present invention to provide a sapphire single crystal member manufacturing apparatus having a structure capable of supporting and fixing a graphite heater.

The above-mentioned subject is achieved by the following present invention. That is,
The apparatus for producing a sapphire single crystal member according to the first aspect of the present invention encloses a storage container, a bottomed cylindrical crucible disposed in the storage container, an outer peripheral surface side of the crucible, and a central axis parallel to the vertical direction. A graphite graphite heater having a heater-side screw hole on the bottom surface, and an end face provided with an electrode-side screw hole, and having a central axis parallel to the vertical direction. A graphite rod-shaped electrode having an end surface connected to the bottom surface of the heater made of graphite, and a graphite screw screwed into the screw hole on the heater side and the electrode side screw hole, and the bottom surface of the graphite heater and the graphite rod electrode The end face of the graphite heater is perpendicular to the vertical direction, the bottom surface side of the graphite heater, and the thickness in the diameter direction of the graphite heater in the vicinity where the heater side screw hole is provided in the circumferential direction, the bottom surface side of the graphite heater, and , Circumferential direction It is larger than the diameter direction of the thickness of the graphite heater in the portion other than the vicinity of the Oite heater side screw holes provided.
Moreover, the sapphire single crystal member manufacturing apparatus of the second aspect of the present invention surrounds the storage container, the bottomed cylindrical crucible disposed in the storage container, the outer peripheral surface side of the crucible, and the central axis is in the vertical direction. It has a cylindrical graphite heater with a heater-side screw hole on the bottom and an end face with an electrode-side screw hole, and the central axis is parallel to the vertical direction. At least, a graphite rod-shaped electrode whose end face is connected to the bottom surface of the graphite heater, and a graphite screw screwed into the heater side screw hole and the electrode side screw hole. The end face of the rod-shaped electrode is perpendicular to the vertical direction, and the diameter of the graphite heater screw is the thickness of the graphite heater in the diameter direction near the bottom of the graphite heater and in the vicinity of the heater side screw hole in the circumferential direction. 1/3 Characterized in that it obtain.

  In one embodiment of the sapphire single crystal member manufacturing apparatus of the present invention, a carbon adhesive layer is preferably provided between the bottom surface of the graphite heater and the end surface of the graphite rod-shaped electrode.

  In another embodiment of the sapphire single crystal member manufacturing apparatus of the present invention, it is preferable that the specific resistance value of the graphite material constituting the graphite rod-shaped electrode and the graphite immo screw is 10 μΩm or less.

  In another embodiment of the sapphire single crystal member manufacturing apparatus of the present invention, the thermal conductivity of the graphite material constituting the graphite rod-shaped electrode and the graphite immo screw is preferably 150 W / m · K or more.

  In another embodiment of the sapphire single crystal member manufacturing apparatus of the present invention, it is preferable that the tensile strength of the graphite material constituting the graphite rod-shaped electrode and the graphite immo screw is 20 MPa or less.

  Another embodiment of the sapphire single crystal member manufacturing apparatus of the present invention preferably includes only a graphite heater as the heating member of the crucible.

  In another embodiment of the sapphire single crystal member manufacturing apparatus of the present invention, a seed crystal can be moved vertically in a die provided with a slit disposed in a crucible and extending downward from the upper end, and on the upper side of the die. It is preferable to further include a seed crystal holding member that holds the seed crystal.

  According to the present invention, the structure for connecting the graphite heater and the electrode arranged so as to surround the outer peripheral surface of the crucible is simple, and the structure capable of supporting and fixing the graphite heater stably for a long period of time. The provided sapphire single crystal member manufacturing apparatus can be provided.

It is a schematic diagram which shows an example of the sapphire single-crystal member manufacturing apparatus of this embodiment. In the sapphire single-crystal member manufacturing apparatus shown in FIG. 1, it is an enlarged end elevation which shows an example of the cross-sectional structure of the connection part vicinity of a graphite heater and an electrode. It is a perspective view which shows an example of the graphite heater used for the sapphire single-crystal member manufacturing apparatus of this embodiment. It is a schematic diagram which shows the other example of the graphite heater used for the sapphire single-crystal member manufacturing apparatus of this embodiment. Here, FIG. 4 (A) is a top view of the graphite heater, and FIG. 4 (B) is an end view between A1 and A2 shown in FIG. 4 (A). It is a model end elevation which shows the dimension of each part of the heater side screw hole vicinity of the graphite heater used for the sapphire single crystal member manufacturing apparatus of this embodiment.

  FIG. 1 is a schematic diagram showing an example of a sapphire single crystal member manufacturing apparatus according to the present embodiment, and FIG. 2 is a view of the vicinity of a connection portion between a graphite heater and an electrode in the sapphire single crystal member manufacturing apparatus shown in FIG. It is an enlarged end elevation showing an example of a cross-sectional structure. In FIG. 1, the details of the cross-sectional structure in the vicinity of the connecting portion between the graphite heater and the electrode are omitted, and the central axes C1 and C2 are parallel to the vertical direction Z. Moreover, description is abbreviate | omitted also about the heater side screw hole shown in FIG. 2, the electrode side screw thread, the screw thread of a stud, and a screw groove. The same applies to an enlarged end view shown in FIG.

  As shown in FIGS. 1 and 2, the sapphire single crystal member manufacturing apparatus 100 of the present embodiment includes a storage container 110, a bottomed cylindrical crucible 120 disposed in the storage container 110, and an outer peripheral surface of the crucible 120. A cylindrical graphite heater 130 (hereinafter abbreviated as “heater 130”) that surrounds the 120S side and is arranged so that the central axis C1 is parallel to the vertical direction Z and has a heater-side screw hole 132 in the bottom surface 130BT. The end surface 140TP is connected to the bottom surface 130BT of the graphite heater 130 so that the central axis C2 is parallel to the vertical direction Z. Graphite rod-like electrode 140 (hereinafter may be abbreviated as “electrode 140”) and graphite-made screw 15 screwed into heater-side screw hole 132 and electrode-side screw hole 142 (Hereinafter sometimes referred to as "stud 150") comprises at least a, the.

  That is, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, it is not necessary to connect the heater 130 and the electrode 140 via a fixing member or a joint used in the techniques described in Patent Documents 1 and 2. For this reason, the structure which connects between the heater 130 and the electrode 140 can be simplified. Therefore, assembly, disassembly, and maintenance of the sapphire single crystal member manufacturing apparatus 100 become easier.

  A current flows between the heater 130 and the electrode 140 when the sapphire single crystal member manufacturing apparatus 100 is used. For this reason, as shown in Patent Documents 1 and 2, the connection between the heater 130 and the electrode 140 is composed of a large number of parts, and the more complicated the gaps between the parts causing the discharge are formed. It becomes easy to be done. Further, the occurrence of electric discharge leads to defective heating of the alumina raw material in the crucible 120 and the alumina melt 200 in which the alumina raw material is dissolved, thereby causing various problems such as a decrease in yield and production interruption due to process abnormality. Therefore, the connection portion between the heater 130 and the electrode 140 is gradually broken by long-term discharge, so that the fixing of the heater 130 becomes unstable. In the worst case, for example, the heater 130 that generates heat is inclined. This may cause problems such as contact with the outer peripheral surface 120S of the crucible 120 and damage of the crucible 120. However, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, not only can the structure of the connection portion between the heater 130 and the electrode 140 be simplified, but also the occurrence of discharge due to the complexity of the connection portion is greatly suppressed. it can.

  Moreover, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, the members constituting the connection portion between the heater 130 and the electrode 140, that is, the heater 130, the electrode 140, and the stud 150 are made of graphite. For this reason, even if the heater 130 is heated from room temperature to a predetermined temperature, a gap is generated in the connection portion due to a difference in thermal expansion coefficient between the heater 130, the electrode 140, and the stud 150, or the connection portion is broken. Can be suppressed. In terms of mechanical strength, it is considered that it is preferable to use a metal or ceramic having excellent mechanical strength for the members other than the heater 130 rather than a brittle graphite member. However, when manufacturing a sapphire single crystal member, it is necessary to cause the heater 130 to generate heat at a temperature equal to or higher than the melting point of alumina (2072 degrees). When it is necessary to heat the heater 130 to such a high temperature range exceeding 2000 degrees, if the connecting portion is made of a different material having a fundamentally different coefficient of thermal expansion, the material constituting the connecting portion is vulnerable. Rather, the adverse effect of the formation of a gap in the connecting portion and the occurrence of destruction due to the difference in thermal expansion coefficient becomes extremely serious. Therefore, in consideration of these points, the present inventors used only graphite as a material constituting the connection portion.

  On the other hand, as described above, the graphite member has the drawback of being brittle and easy to break. Therefore, when an external force is applied in the diameter direction, which is the most fragile part of the electrode 140 that supports the heater 130 and the stud 150 that connects the heater 130 and the electrode 140, these graphite members are easily destroyed. However, since the sapphire single crystal member manufacturing apparatus 100 according to the present embodiment is used for manufacturing a sapphire member, the sapphire single crystal member manufacturing apparatus 100 is used to prevent convection of the silicon melt in the crucible as in the single crystal member manufacturing apparatus shown in Patent Document 1. It is not necessary to provide a magnetic field generator (coil) that generates a large force for rotating the heater 130 in the circumferential direction. For this reason, since the rotating force does not act on the heater 130 itself, the force does not act in the diameter direction of the electrode 140 and the stud 150 due to such a rotating force.

  In addition to this, the weight of the heater 130 is supported by the electrode 140 and the stud 150 arranged on the lower side of the heater 130 in the vertical direction Z. In other words, due to the weight of the heater 130, in principle, the force acting on the electrode 140 and the stud 150 acts only in the axial direction of the electrode 140 and the stud 150, and acts on the fragile diameter direction mechanically. No. For these reasons, even if graphite members are used as the electrodes 140 and the studs 150, the disadvantage of the graphite members that are brittle and easy to break does not cause a decrease in the strength of the connection portion.

  Furthermore, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, the bottom surface 130BT of the heater 130 and the end surface 140TP of the electrode 140 are orthogonal to the vertical direction Z. That is, the connection interface between the bottom surface 130BT and the end surface 140TP is parallel to a plane orthogonal to the vertical direction Z. In addition, an electrode 140 that supports the weight of the heater 130 is disposed immediately below the heater 130 so that the central axis C1 of the heater 130 and the central axis C2 of the electrode 140 are parallel to each other. For this reason, the weight of the heater 130 acting on the lower side in the vertical direction Z does not act as a peeling force that promotes breakage of the connection interface and formation of a gap.

  Therefore, (1) the heater acting on the lower side of the vertical direction Z pushes the other end of the joint whose one end is supported by the electrode disposed on the outer peripheral side of the heater downward, so that the heater / joint The conductive structure shown in Patent Document 2 that generates peeling force at the connection interface and the joint / electrode connection interface, and (2) the weight of the heater acting on the lower side in the vertical direction Z is the heater and the outer peripheral surface of the heater In the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, compared with the single crystal member manufacturing apparatus shown in Patent Document 3 that generates a shearing force (peeling force) in a direction parallel to the connection interface with the electrode connected to the electrode, Destruction at the connection interface between the heater 130 and the electrode 140 is extremely difficult to occur.

  Further, since the stud 150 is screwed into the heater side screw hole 132 and the electrode side screw hole 142, the outer peripheral surface of the stud 150 and the inner peripheral surface of the heater side screw hole 132 and the electrode side screw hole 142 are substantially the same. Can be tightly attached. In addition, even when the heater 130 generates heat at a high temperature exceeding 2000 degrees, the heater 130, the electrode 140, and the stud 150 are made of graphite, so that a gap due to a difference in thermal expansion coefficient is hardly generated. Therefore, the connection between the stud 150, the heater-side screw hole 132, and the electrode-side screw hole 142 is less likely to be discharged or broken due to the discharge.

  Therefore, the sapphire single crystal member manufacturing apparatus 100 of the present embodiment has a simple structure for connecting the heater 130 and the electrode 140 disposed so as to surround the outer peripheral surface 120S of the crucible 120, but is stable for a long time. Thus, the heater 130 can be supported and fixed.

  In the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, as illustrated in FIG. 2, carbon cement is usually provided at the interface between the bottom surface 130BT of the graphite heater 130 and the end surface 140TP of the graphite rod electrode 140. It is particularly preferable to provide a carbon adhesive layer 160 formed using By providing the carbon adhesive layer 160, the heater 130 and the electrode 140 can be more firmly fixed. In addition to this, it is possible to more reliably prevent the occurrence of discharge by forming a gap at the interface between the two members. The carbon adhesive layer 160 is made of the same graphite as the material constituting the heater 130, the electrode 140, and the stud 150, which are main members constituting the connection portion between the heater 130 and the electrode 140. For this reason, since the difference in thermal expansion coefficient between these four members is zero or very small, it is difficult to form a gap between members due to the difference in thermal expansion coefficient (that is, the cause of discharge). The carbon cement can be used without particular limitation as long as it is a known carbon cement, but generally a carbon cement containing at least a graphite powder and a solvent such as furfuryl alcohol can be used.

  As the stud 150, as shown in FIG. 2, a so-called imor screw having no head and having only a cylindrical screw shaft portion is used. A screw thread is engraved on the outer peripheral surface 150S of the screw shaft portion (not shown in FIG. 2). The thread may be carved on the entire outer peripheral surface 150S of the screw shaft portion, but may be carved only in the vicinity of both end sides in the axial direction on the outer peripheral surface 150S of the screw shaft portion. In addition, the shape of both ends (screw tips 150TP, 150BT) of the stud 150 is not particularly limited. For example, in addition to the flat surface (flat tip) illustrated in FIG. A well-known screw tip shape such as a (dent point) or a pointed point (point of sharpness) can be appropriately selected.

  Further, when the heater 130 and the electrode 140 are connected by the stud 150, for example, after the stud 150 is lightly inserted and fixed into the electrode side screw hole 142 of the electrode 140, the tip of the stud 150 is inserted into the heater side screw hole 132. The stud 150 can be screwed deeply into both the heater side screw hole 132 and the electrode side screw hole 142 by using the electrode 140 as a tool. For this reason, it is not necessary to adopt a shape suitable for tightening the stud 150 with a metal tool such as a wrench, spanner or screwdriver as the shape of the screw tips 150TP and 150BT. Further, since the graphite stud 150 is brittle and easily broken, if a metal tool harder than graphite is used, the stud 150 may be cracked or chipped, but the same graphite electrode as the stud 150 is used. If 140 is used as a substitute member of a tool, such a problem can be suppressed. The shape suitable for tightening the stud 150 with a tool is a case where a hole or a protrusion that engages with the tool is provided in the screw tip 150TP or 150BT part, or the outer peripheral contour line of the screw tip 150TP or 150BT part. The case where it becomes the polygonal shape which meshes with a tool is mentioned. Specifically, a shape in which a hexagonal hole is provided in the screw tips 150TP and 150BT, a shape in which a cross or straight groove is provided, and a screw shape such as a hexagonal column and a quadrangular column is provided in the screw tips 150TP and 150BT. This is the case where the protrusion is provided or the planar shape of the screw tips 150TP and 150BT is a polygonal shape such as a hexagon or a quadrangle.

  Further, the heater-side screw hole 132 and the electrode-side screw hole 142 may have a vertical hole shape in which at least the inner peripheral surfaces 132S and 142S can be screwed into the stud 150 with substantially no gap, as illustrated in FIG. In addition, it is more preferable that the heater side screw hole 132 and the bottom surfaces 132BT and 142BT of the electrode side screw hole 142 having a vertical hole shape have substantially no gap with the screw tips 150TP and 150BT of the stud 150. In the example shown in FIG. 2, the bottom surfaces 132BT and 142BT are flat surfaces corresponding to the flat-tip studs 150.

As a material constituting the heater 130, the electrode 140, and the stud 150, any known material including a carbon fiber reinforced carbon composite material can be used without particular limitation as long as it is a graphite material. There are various varieties of graphite materials having different physical properties such as specific resistance, bending strength, tensile strength, thermal expansion coefficient, thermal conductivity, etc., depending on the raw materials and the production method. For example, typical numerical ranges of physical properties of commercially available graphite materials include a specific resistance value of 1 to 40 μΩm, a bending strength of 5 to 350 MPa, a tensile strength of 5 to 350 MPa, and a thermal expansion coefficient of 0 to 10 × 10. ⁻⁶ / ° C. and thermal conductivity of about 5 to 200 W / m · K. For this reason, the graphite material to be used can be selected in consideration of functions and roles required for the heater 130, the electrode 140, and the stud 150. Here, in order to increase the heat generation efficiency, the heater 130 preferably has a higher specific resistance value that constitutes the heater 130. Specifically, it is preferably 13 μΩm or more, more preferably 16 μΩm or more. The upper limit of the specific resistance value is not particularly limited, but is practically preferably 40 μΩm or less.

  On the other hand, the electrode 140 and the stud 150 are a conduction path between the heater 130 and the power source. Therefore, in order to suppress wasteful power consumption when the heater 130 generates heat, the specific resistance value of the graphite material constituting the electrode 140 and the stud 150 is preferably low, specifically, 10 μΩm or less is preferable. 5 μΩm or less is more preferable. The lower limit value of the specific resistance value is not particularly limited, but is practically preferably 1 μΩm or more. The electrode 140 and the stud 150 generate a thermal stress due to a steep temperature gradient in the axial direction C2 in a heating stage in which the heater 130 generates heat and reaches a temperature exceeding room temperature to 2000 degrees. It becomes easy. Such a thermal stress tends to cause the electrode 140 and the stud 150 to be destroyed. Therefore, in order to relieve the thermal stress, it is preferable that the thermal conductivity of the graphite material constituting the electrode 140 and the stud 150 is higher, specifically, 150 W / m · K or more is preferable, and 170 W / m · K is more preferable. The above is more preferable. In addition, although the upper limit of heat conductivity is not specifically limited, 200 W / m * K or less is preferable practically.

  Further, the electrode 140 is used as a structural member that supports and fixes the heater 130, and the stud 150 is also used as a structural member that connects the heater 130 and the electrode 140. Therefore, as a material constituting these structural members, it is usually necessary to use a graphite material having excellent mechanical properties. However, obtaining a graphite material satisfying a desired value for a plurality of physical property values becomes more difficult as the types of physical property values increase, and if the satisfaction of a certain physical property value is prioritized, other physical property values must be sacrificed. Trade-off problems are likely to occur. In addition, when the present inventors investigated a commercially available graphite material, there is no graphite material that simultaneously satisfies a low specific resistance value, a high thermal conductivity, and an excellent mechanical property value. It has been found that a commercially available graphite material cannot be used without sacrificing these physical properties.

  However, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, as described above, the weight of the heater 130 is received in the direction in which the electrode 140 has the highest mechanical strength, that is, the axial direction. For this reason, it is difficult to apply bending stress or tensile stress due to the weight of the heater 130 to the electrode 140 or the stud 150. In addition to this, the present inventors manufactured the electrode 140 and the stud 150 using a graphite material having extremely low tensile strength and bending strength among various commercially available graphite materials. Although it applied to the sapphire single crystal member manufacturing apparatus 100, it confirmed that a problem did not arise practically especially at the point of the structural material used with the sapphire single crystal member manufacturing apparatus 100.

  That is, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, the constituent material of the electrode 140 and the stud 150 is a graphite material whose bending strength and tensile strength are considerably lower than the average value of a general graphite material. However, since it can be used, a graphite material can be selected without considering bending strength and tensile strength. For this reason, the freedom degree of selection of the graphite material which can be utilized as the electrode 140 or the stud 150 can be enlarged greatly. For example, within the above-described typical numerical range, a graphite material having a bending strength of 35 MPa or less and further 28 MPa or less can be used, and a tensile material having a tensile strength of 20 MPa or less and further 15 MPa or less can be used.

  In addition, when it is not necessary to consider bending strength and tensile strength, the electrode 140 and the stud 150 are manufactured by procuring the above-described low-resistance and high-thermal conductivity graphite material from commercially available graphite materials. Is also possible. In addition, as such a graphite material, it can select from non-composite type graphite materials other than the carbon fiber reinforced carbon composite material excellent in mechanical characteristics among commercially available graphite materials. Specifically, among commercially available graphite materials, the tensile strength is 20 MPa or less, and the mechanical properties are inferior, but the specific resistance value is 10 μΩm or less and the thermal conductivity is 150 W / m · K or more. A certain graphite material can be used, and among these, the tensile strength is 15 MPa or less, and the mechanical property value is further inferior, but the specific resistance value is 5 μΩm or less and the thermal conductivity is 170 W / m · K or more. It is also possible to use a graphite material.

  Moreover, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, a coil for the purpose of suppressing convection of the alumina melt 200 in the crucible 120 is unnecessary. Further, from the viewpoint of promoting the melting of the alumina raw material and promoting / maintaining the heating of the alumina melt 200, in addition to the graphite heater 130 (side heater) that heats the outer peripheral surface 120S side of the crucible 120, patent literature As in the single crystal member manufacturing apparatus shown in FIG. 3, a graphite heater (bottom heater) for heating the bottom surface 120BT side of the crucible 120 can be newly provided. However, in the sapphire single crystal member manufacturing apparatus 100 of the present embodiment, it is desirable to provide only the heater 130 as the heating member of the crucible 120, and it is preferable not to use the bottom heater. The use of the bottom heater is advantageous in terms of shortening the melting / heating time, but also has the disadvantages described below.

  That is, when the bottom heater is provided, only the portion close to the bottom heater is heated on the outer peripheral surface of the electrode 140 that supports the side heater (heater 130). For this reason, a temperature gradient is generated in the diameter direction of the electrode 140, and a difference in thermal expansion occurs between the bottom heater side and the opposite side of the bottom heater, so that the electrode 140 is warped, resulting in the electrode 140. Is easy to break. Further, from the viewpoint of temperature control of the alumina melt 200, the control factor increases to two (the heater 130 and the bottom heater) instead of one (the heater 130), so that the temperature control becomes more complicated.

  The shape of the heater 130 is not particularly limited as long as the heater 130 has a cylindrical shape in which the heater side screw hole 132 is provided on the bottom surface 130BT. However, the heater 130 is preferably a cylindrical heater, and in particular, like the heater 130A (130) illustrated in FIG. 3, the first slit extending from the top surface 130TP to the lower side in the direction of the central axis C1. It is preferable that 134A and the second slits 134B extending from the bottom surface 130BT to the upper side in the direction of the central axis C1 are cylindrical heaters provided alternately along the circumferential direction. The lengths of the slits 134A and 134B are set to be shorter than the length of the heater 130A in the central axis C direction so that the heater 130A is not divided in the circumferential direction and an appropriate strength can be maintained. The

  Further, the thickness in the diameter direction of the heater 130 may be constant in the circumferential direction and the central axis C1 direction as illustrated in FIG. However, like the heater 130B (130) illustrated in FIG. 4, the diameter of the heater 130B in the vicinity of the bottom surface 130BT of the heater 130B and in the vicinity where the heater-side screw hole 132 is provided in the circumferential direction (screw hole vicinity 136A). The thickness t11 in the direction is preferably larger than the thickness t12 in the diameter direction of the heater 130 in a portion other than the screw hole vicinity portion 136A (non-screw hole vicinity portion 136B). In this case, since only the thickness t11 of the screw hole vicinity portion 136A can be increased while suppressing an increase in the thickness and weight of the entire heater 130B, the strength of the screw hole vicinity portion 136A can be increased. In addition to this, in order to increase the strength of the entire connecting portion, it is also easy to employ a larger diameter heater side screw hole 132 and stud 150. When the slits 134A and 134B illustrated in FIG. 3 are provided in the heater 130B illustrated in FIG. 4, the screw hole vicinity portion 136A is provided between the two second slits 134B adjacent in the circumferential direction.

  The diameter of the stud 150 is not particularly limited as long as it corresponds to the inner diameters of the heater side screw hole 132 and the electrode side screw hole 142. When the mechanical strength of the heater 130 alone is taken into consideration in the vicinity where the heater-side screw hole 132 is provided, the structure in the diameter direction of the heater 130 is considered to be ideal as described below. That is, as shown in FIG. 5, the diameter of the heater side screw hole 132 corresponding to the diameter of the stud 150 is T2, the thickness from the inner peripheral surface 130S1 of the heater 130 to the heater side screw hole 132 is T1, and the heater 130 When the thickness from the outer peripheral surface 130S2 to the heater-side screw hole 132 is T3, it is considered that T1, T2, and T3 are ideally the same. By adopting such a configuration, the diameter of the heater 130 of each of the inner peripheral side portion (thickness T1 portion) and the outer peripheral side portion (thickness T3 portion) of the heater side screw hole 132 and the stud 150 (thickness T2 portion). The mechanical strength in the direction can be maximized without bias. On the other hand, the breakage of any of the thickness T1 portion, the thickness T2 portion, or the thickness T3 portion leads to the formation of a gap and the occurrence of discharge due to the gap. For this reason, equalizing the thicknesses of T1, T2, and T3 can equalize the probability of breakage of each part (no bias), and thus it is considered that the probability of occurrence of discharge due to the gap can be minimized.

However, when the present inventors examined, the diameter (thickness T2) of the stud 150 is
The thickness of the heater 130 in the diameter direction (T1 + T2 + T3) in the vicinity of the bottom side of the heater 130 and in the vicinity of the heater side screw hole 132 is set to 1/3, in other words, T2 / (T1 + T2 + T3) is 1 / It was confirmed that the occurrence of discharge could be further suppressed by setting the ratio to not less than 3, but exceeding 1/3, and more than 1/2.

  Although the details of the reason why such an effect is obtained are unknown, the present inventors presume as follows. That is, when some stress acting in the diameter direction of the heater 130 is applied to the thickness T1 portion and the thickness T3 portion located on both sides of the stud 150, the thickness T1 portion is directed to the inner peripheral side of the heater 130. The stress can be dispersed to the outer peripheral side of the heater 130 with respect to the thickness T3 portion. However, both sides of the stud 150 (thickness T2 portion) are surrounded by the thickness T1 portion and the thickness T2 portion. Therefore, when any stress acting on the stud 150 in the diametrical direction of the heater 130 is applied, the stud 150 is not released from the stressed state because there is no stress escape. For this reason, when the thicknesses of T1, T2, and T3 are equal, the stud 150 (thickness) is relatively compared with the inner peripheral side portion (thickness T1 portion) and the outer peripheral side portion (thickness T2 portion) of the heater side screw hole 132. (T2 portion) is considered to be most easily destroyed.

  Accordingly, by increasing the thickness of the stud 150 (thickness T2 portion) relative to the thickness T1 portion and the thickness T3 portion, the difference in the fracture probability between the stud 150 and the thickness T1 portion and the thickness T3 portion is further increased. Can be small. Further, even if the probability of destruction of the thickness T1 portion or the thickness T3 portion is increased due to the relative increase in the thickness of the stud 150 (thickness T2 portion), these portions are not affected by the destruction of the heater 130 main body. And easily fall off to the inner peripheral side or outer peripheral side of the heater 130. For this reason, even if breakage occurs, if such dropout occurs, a gap where a discharge is likely to occur may be formed between the stud 150 (thickness T2 portion) and the thickness T1 portion or the thickness T3 portion. Can be prevented.

  The number of electrodes 140 connected to the heater 130 may be at least two, but three or more may be used. However, from the viewpoint of stably supporting and fixing the heater 130, it is usually preferable to use four electrodes 140. When three or more electrodes 140 are used, if any two of the three or more electrodes 140 are connected to the power source, the remaining electrodes 140 are dummy that are not connected to the power source. It may be an electrode. Further, from the viewpoint of stably supporting and fixing the heater 130, the electrodes 140 are preferably arranged at equal intervals in the circumferential direction of the heater 130. For example, when the heater 130 is a cylindrical heater and four electrodes 140 are used, the electrodes 140 are disposed at positions of 0 degrees, 90 degrees, 180 degrees, and 270 degrees with respect to the central axis C1 of the heater 130. It is preferable to do. The lower end side of the electrode 140 is supported by a fixing member (not shown in FIG. 1) and connected to a power source. However, the electrode 140 may be supported and fixed near the center of the electrode 140 in the longitudinal direction or connected to a power source. Further, the electrode 140 functioning as a dummy electrode is not connected to a power source. In addition, as illustrated in FIG. 1, when the lower end side of the electrode 140 is positioned on the lower surface side of the bottom of the storage container 110, the bottom of the storage container 110 is provided with a through hole 110 </ b> H through which the electrode 140 is inserted. The inner peripheral surface of the hole 110H and the electrode 140 are electrically insulated by, for example, disposing an insulating member as necessary.

  Further, the length of the electrode 140 is not particularly limited, but if it is too short, the wiring connecting the power source and the electrode 140, the metal connection terminal, and the like are easily damaged by the heat of the heater 130. Therefore, the length of the electrode 140 is preferably at least 3 times the diameter of the electrode 140, more preferably at least 12 times. The upper limit of the length is not particularly limited, but is practically 50 times or less the diameter of the electrode 140.

  Next, the structure of each part of the sapphire single crystal member manufacturing apparatus 100 of the present embodiment other than those described above will be described. First, the storage container 110 has an open / close section such as a shutter so that the internal space is sealed off from the outside and the sapphire single crystal member 220 grown in the storage container 110 can be taken out. (Not shown in the figure) is provided. Further, in order to connect the inside and the outside of the storage container 110, a gas inlet and a gas outlet (not shown in FIG. 1) can be provided in any part of the storage container 110. In this case, the end of the gas introduction port outside the storage container 110 is connected to an inert gas supply source that supplies an inert gas such as Ar gas, and the end of the gas discharge port outside the storage container 110 is It may be open to the atmosphere, but is preferably connected to an exhaust device such as a rotary pump.

  The crucible 120 can be a bottomed cylindrical member made of a high melting point metal such as Mo having a melting point exceeding the melting point of alumina, but it is usually preferable to use a bottomed cylindrical member. The crucible 120 is disposed on the bottom side in the storage container 110. In this case, the crucible 120 may be disposed so as to be in contact with the bottom of the storage container 110, but normally, as illustrated in FIG. 1, the crucible 120 is placed on a plate-shaped crucible support 190 installed at the bottom of the storage container 110. It is preferable to arrange. The crucible support 190 may be provided with a through hole 190H through which the electrode 140 is inserted, as shown in FIG. In addition, the sapphire single crystal member manufacturing apparatus 100 of the present embodiment usually includes a known heating state detection device such as a thermocouple or a radiation thermometer in order to monitor the heating state of the alumina melt 200 in the crucible 120. Installed at an appropriate position. For example, a thermocouple can be placed near the bottom of crucible 120.

  Further, as illustrated in FIG. 1, the heat insulating member 192 may be appropriately disposed at a position surrounding the heater 130 and the crucible 120. In addition, when the crucible support part 190 is comprised from a heat insulating material, the heat insulation member 192 may be a member formed integrally with the crucible support part 190. Further, the heat insulating member 192 is disposed so as to surround at least the outer peripheral side of the heater 130, but as illustrated in FIG. 1, in addition to the outer peripheral side of the heater 130, the upper side of the heater 130 and the upper outer periphery of the crucible 120. You may arrange | position so that the part side may be enclosed.

  Furthermore, a raw material supply device for supplying an alumina raw material into the crucible 120 may be provided as necessary. As the raw material supply device, for example, a device having a raw material supply pipe disposed above the crucible 120 and a raw material supply source (not shown in FIG. 1) such as a raw material supply tank connected thereto can be used. .

  Moreover, when manufacturing a sapphire single crystal member using the sapphire single crystal member manufacturing apparatus of this embodiment, the well-known manufacturing method which can utilize the sapphire single crystal member manufacturing apparatus of this embodiment can be utilized suitably, but it is typical. For this, an EFG (Edge-defined Film-fed Growth) method or a CZ (Czochralski) method can be used.

  When using the EFG method, as shown in FIG. 1, the sapphire single crystal member manufacturing apparatus 100 according to the present embodiment includes a die 170 having a slit 172 disposed in the crucible 120 and extending downward from the upper end. And a seed crystal holding member 180 that holds the seed crystal 210 so that the seed crystal 210 can move in the vertical direction Z above the die 170.

  The die 170 is usually disposed near the center of the crucible 120 and is made of a refractory metal such as Mo. When the sapphire single crystal member 220 is grown, the lower side of the die 170 is immersed in the alumina melt 200 held in the crucible 120. For this reason, the alumina melt 200 held in the crucible 120 rises in the slit 172 by capillary action and can reach the opening on the upper end side of the slit 172. In the example shown in FIG. 1, the die 170 is disposed in a state of being fixed in the crucible 120, and a fixing member (for example, a support rod that connects the upper end side of the crucible 120 and the upper side of the die 170 is used for fixing. Etc.) can also be used. The structure of the die 170 includes a slit 172 extending downward from the upper end of the die 170 so that the alumina melt 200 held in the crucible 120 can be guided to the upper end of the die 170 using a capillary phenomenon. However, it is generally preferable to have a structure provided with a slit 172 that penetrates the die 170 in the vertical direction Z as shown in FIG.

  As the die 170, as illustrated in FIG. 1, a member in which two partition plates are arranged in parallel with a small interval so as to form a slit 172 can be used. Therefore, in the example using the die 170 shown in FIG. 1, one plate-like sapphire single crystal member 220 can be manufactured. Further, if a member having three or more partition plates arranged in parallel with a small interval so as to form a slit 172 is used as the die 170, two or more plate-like sapphire single crystal members 220 are simultaneously manufactured. can do. Further, by appropriately selecting the cross-sectional shape of the slit 172 in the cross section obtained by cutting the die 170 along a plane orthogonal to the vertical direction Z, the sapphire single crystal member having various shapes such as a cylindrical shape and a semicylindrical shape in addition to the plate shape. 220 can also be manufactured.

  Moreover, the sapphire single crystal member manufacturing apparatus 100 includes a seed crystal holding member 180 that holds the seed crystal 210 on the upper side of the die 170 so that the seed crystal 210 can move in the vertical direction Z. In the example shown in FIG. 1, the seed crystal holding member 180 is a rod-shaped member whose longitudinal direction is parallel to the vertical direction Z, and the seed crystal 210 is fixed to the lower end of the seed crystal holding member 180. The seed crystal holding member 180 can be moved in the vertical direction Z by a driving device (not shown in the drawing) such as a motor. In manufacturing the sapphire single crystal member 220, first, the seed crystal 210 is brought into contact with the alumina melt 200 that has risen to the upper end opening of the slit 172 of the die 170. Subsequently, the sapphire single crystal member 220 can be grown on the lower side of the seed crystal 210 by gradually moving the seed crystal holding member 180 upward. In the case where a plurality of slits 172 are provided in the die 170, a seed crystal 210 having a size capable of simultaneously contacting the upper end openings of the plurality of slits 172 is used, or a plurality of slits 172 are provided corresponding to each slit 172. The seed crystal 210 can be used.

  On the other hand, when the CZ method is used, an apparatus in which the die 170 is omitted from the sapphire single crystal member manufacturing apparatus 100 shown in FIG. 1 is used. In the CZ method, after the seed crystal 210 is brought into contact with the alumina melt 200, the seed crystal holding member 180 is gradually pulled upward while rotating with its central axis as a rotation axis. Thereby, the cylindrical sapphire single crystal member 220 can be obtained.

  In both the EGF method and the CZ method, a sapphire single crystal is used as the seed crystal 210.

  Next, an example of a manufacturing process in the case of manufacturing the sapphire single crystal member 220 by the EFG method using the sapphire single crystal member manufacturing apparatus 100 of the present embodiment shown in FIG. 1 will be described. In manufacturing the sapphire single crystal member 220, a raw material supply step for supplying an alumina raw material into the crucible 120, a melting step for obtaining the alumina melt 200 by dissolving the alumina raw material supplied into the crucible 120, and a capillary phenomenon After the alumina melt 200 that has reached the opening on the upper end side of the slit 172 of the die 170 is brought into contact with the seed crystal 210, the seed crystal 210 is pulled upward to crystal-grow the sapphire single crystal member 220. And at least.

  The supply of the alumina raw material to the crucible 120 in the raw material supply step may be performed outside the sapphire single crystal member manufacturing apparatus 100 or may be performed inside the sapphire single crystal member manufacturing apparatus 100.

  In the melting step, the raw material supplied into the crucible 120 is melted. Thereby, the alumina melt 200 is obtained. In the stage before crystal growth of the sapphire single crystal member 220, first, heating by the heater 130 is started after the inside of the storage container 110 is evacuated and sufficiently decompressed or while decompressing. In addition, the inert gas such as Ar gas is stored after the temperature in the storage container 110 is heated to a certain temperature within a range of 800 to 1800 degrees (preferably within a range of 1300 to 1700 degrees), for example. It may be further introduced into the container 110 and the inside of the storage container 110 may be replaced with an inert gas. When the inside of the containment vessel 110 is replaced with an inert gas, the oxygen concentration in the inert gas atmosphere is preferably controlled to, for example, 1000 ppm or less in the containment vessel 110 during the execution of the crystal growth step. More preferably, it is controlled to 100 ppm or less.

  In the crystal growth step, first, the alumina melt 200 that has reached the opening on the upper side of the slit 172 of the die 170 by capillary action is brought into contact with the seed crystal 210. Then, the sapphire single crystal member 220 is grown by pulling the seed crystal 210 upward. After finishing the crystal growth step, the sapphire single crystal member 220 is appropriately cooled, and then the seed crystal holding member 180 is further lifted upward, so that the sapphire single crystal grown under the seed crystal 210 together with the seed crystal 210. The member 220 is moved out of the storage container 110 and taken out.

100: Sapphire single crystal member manufacturing apparatus 110: Containment vessel 110H: Through hole 120: Crucible 120BT: Bottom surface 120S: Outer peripheral surface 130, 130A, 130B, 130C: Heater (graphite heater)
130TP: Top surface 130BT: Bottom surface 130S1: Inner peripheral surface 130S2: Outer peripheral surface 132: Heater side screw hole 132BT: Bottom surface 132S: Inner peripheral surface 134A: First slit 134B: Second slit 136A: Screw hole vicinity 136B: Non-screw Hole vicinity 140: Electrode (graphite rod electrode)
140TP: End surface 142: Electrode side screw hole 142BT: Bottom surface 142S: Inner peripheral surface 150: Stud (graphite thread screw)
150TP: screw tip 150BT: screw tip 150S: outer peripheral surface 160: carbon adhesive layer 170: die 172: slit 180: seed crystal holding member 190: crucible support 190H: through hole 192: heat insulating member 200: alumina melt 210: seed Crystal 220: Sapphire single crystal member

Claims (8)

A containment vessel,
A bottomed cylindrical crucible disposed in the containment vessel;
A cylindrical graphite heater that surrounds the outer peripheral surface side of the crucible and is arranged so that the central axis is parallel to the vertical direction and has a heater-side screw hole on the bottom surface;
A graphite rod-shaped electrode having an end surface provided with an electrode-side screw hole, the end surface of which is connected to the bottom surface of the graphite heater so that a central axis is parallel to the vertical direction;
A graphite screw that is screwed into the heater-side screw hole and the electrode-side screw hole;
The bottom surface of the graphite heater and the end surface of the graphite rod-shaped electrode are orthogonal to the vertical direction ,
The thickness in the diameter direction of the graphite heater in the vicinity of the bottom surface side of the graphite heater and in the vicinity where the heater side screw hole is provided in the circumferential direction is the bottom surface side of the graphite heater and the heater in the circumferential direction. The sapphire single crystal member manufacturing apparatus characterized by being larger than the thickness of the graphite heater in the diameter direction in a portion other than the vicinity where the side screw holes are provided . A containment vessel,
A bottomed cylindrical crucible disposed in the containment vessel;
A cylindrical graphite heater that surrounds the outer peripheral surface side of the crucible and is arranged so that the central axis is parallel to the vertical direction and has a heater-side screw hole on the bottom surface;
A graphite rod-shaped electrode having an end surface provided with an electrode-side screw hole, the end surface of which is connected to the bottom surface of the graphite heater so that a central axis is parallel to the vertical direction;
A graphite screw that is screwed into the heater-side screw hole and the electrode-side screw hole;
The bottom surface of the graphite heater and the end surface of the graphite rod-shaped electrode are orthogonal to the vertical direction,
The diameter of the graphite screw is more than one third of the thickness of the graphite heater in the diameter direction in the vicinity of the bottom side of the graphite heater and in the vicinity of the heater side screw hole in the circumferential direction. A sapphire single crystal member manufacturing apparatus. And the bottom surface of the graphite heater, a sapphire single crystal component manufacturing apparatus according to claim 1 or 2, characterized in that the carbon bonding layer is provided between the end surface of the graphite rod electrode. The apparatus for producing a sapphire single crystal member according to any one of claims 1 to 3, wherein a specific resistance value of the graphite material constituting the graphite rod electrode and the graphite screw is 10 µΩm or less. The sapphire single crystal member according to any one of claims 1 to 4 , wherein the graphite rod-shaped electrode and the graphite material constituting the graphite immobilizer have a thermal conductivity of 150 W / m · K or more. manufacturing device. The apparatus for producing a sapphire single crystal member according to any one of claims 1 to 5 , wherein a tensile strength of the graphite material constituting the graphite rod-shaped electrode and the graphite screw is 20 MPa or less. The sapphire single crystal member manufacturing apparatus according to any one of claims 1 to 6 , wherein only the graphite heater is provided as a heating member of the crucible. A die disposed in the crucible and provided with a slit extending downward from the upper end;
A seed crystal holding member that holds the seed crystal so that the seed crystal can move in the vertical direction on the upper side of the die;
The sapphire single crystal member manufacturing apparatus according to any one of claims 1 to 7 , further comprising:

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