JP2017193472A - Crystal growth apparatus for EFG method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crystal growth apparatus for EFG method facilitating short-time installation of heat reflection plates at optimum intervals capable of uniformizing heat distribution in an upper portion of a crucible according to a width dimension of a die.SOLUTION: A crystal growth apparatus for EFG method includes at least a die having a slit, a crucible, a lid, and a plurality of heat reflection plates. The die is housed in the crucible, and an opening of the crucible except the die is covered with the lid. The plurality of heat reflection plates are provided successively from the side on which the crucible is installed. The crystal growth apparatus is formed so that each interval to a lower surface of a second and subsequent heat reflection plates with respect to an upper surface of the lid as a reference plane is not a natural number multiple (excluding multiples of zero and one) of an interval to a lower surface of the first heat reflection plate with respect to the upper surface of the lid as the reference plane.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a crystal growth apparatus for the EFG method.

  Currently, a sapphire single crystal substrate is widely used as a semiconductor substrate typified by a light emitting element such as an LED (Light Emitting Diode). Examples of mass production methods for sapphire single crystal substrates include CZ method (Czochralski method) and EFG method (Edge-defined Film-fed. Growth method).

  The CZ method is a method of growing a sapphire single crystal with an ingot and further slicing the ingot into a substrate. One EFG method is a method of growing a sapphire single crystal into a flat plate shape and cutting the sapphire single crystal into a substrate shape. In the EFG method, since the sapphire single crystal is grown in a flat plate shape as compared with the CZ method, the step of slicing the sapphire single crystal can be omitted, which is advantageous in terms of mass productivity. An apparatus for growing a sapphire single crystal by such an EFG method has been filed and published (for example, see Patent Document 1 or Patent Document 2).

  In the single crystal growing apparatus described in Patent Document 1, a seed crystal (referred to as “seed crystal” in Patent Document 1) is disposed on the liquid surface of the raw material melt for growing a flat sapphire single crystal, and then the seed crystal. By pulling up, one flat sapphire single crystal is manufactured.

  In Patent Document 2, mass productivity is improved by growing a plurality of sapphire single crystals at once using the EFG method.

  In Patent Documents 1 and 2, both use a heat reflector (referred to as “horizontal shield 28” in Patent Document 1 and “horizontal heat shield 160” in Patent Document 2) in order to adjust the heat distribution in the die. ing. Both patent documents disclose the structure of a growing apparatus in which a plurality of heat reflecting plates are provided in the vertical direction. It seems that the heat distribution is adjusted by this, and the heat distribution at the top of the die is made uniform over the width direction of the die.

JP 2010-229030 A Special table 2010-504274 gazette

  However, when the present applicant reproduced the growth of a sapphire single crystal based on Patent Documents 1 and 2, the mixing of bubbles in the growing sapphire single crystal was not eliminated. In patent documents 1 and 2, when installing a plurality of heat reflectors in the vertical direction, it can be read from the drawings of each document that the installation intervals are set uniformly. In order to grow a single crystal having no crystal defects, it is considered best to set the heat distribution uniformly in the width direction of the die. In particular, when growing a large single crystal in which the number of inches of the sapphire single crystal to be grown is 2 inches or more, the width of the die increases as the number of inches of the single crystal increases. It is thought that uniform distribution will become more important.

  Therefore, in view of the purpose of providing a uniform heat distribution across the width direction of the die, the heat reflection of the radiant heat is more uniform when the plurality of heat reflecting plates are also set at equal intervals in the vertical direction. Presumed to be. However, when the present applicant reproduced and verified the growth of the sapphire single crystal, bubbles were mixed into the sapphire single crystal during the growth.

  When the applicant verified the cause of the mixing of bubbles into the sapphire single crystal through a growth experiment, the influence of the radiant heat from the lid covering the opening of the crucible containing the die and the radiant heat from the top of the die was observed. It has been found that it works greatly.

  In the crucible, a melt (melt) obtained by melting the raw material of the sapphire single crystal is stored, and the opening of the crucible is covered with a lid so as to cover the melt. Furthermore, due to capillary action, a melt pool is formed at the top of the die through the slit. When radiant heat from the melt is radiated to the outside of the crucible, radiant heat is radiated in all directions from the outside of the crucible. However, radiant heat radiated in the growth direction of the sapphire single crystal at the top of the crucible through the lid, or radiant heat radiated in the growth direction of the sapphire single crystal at the top of the crucible from the melt pool at the top of the die. The applicant considered that this directly affects the pulling direction accompanying the growth of a sapphire single crystal. As described above, the applicant of the present invention is that the radiant heat radiated to the upper part of the crucible through the lid and the radiant heat radiated to the upper part of the crucible from the melt pool at the upper part of the die in the growth direction of the sapphire single crystal. The conclusion that the heat distribution is destabilized is derived.

  From there, when installing multiple stages of heat reflectors in the vertical direction, the heat distribution at the top of the crucible will be uniform unless the heat reflector is placed precisely according to the width of the die. Unexpectedly, the present applicant has derived from experimental verification that bubbles cannot be eliminated during the growth of a sapphire single crystal.

  The present invention has been made in view of the above problems, and in accordance with the width dimension of the die, the heat reflector is easily installed in a short time at an optimal interval at which the heat distribution in the upper part of the crucible can be made uniform. An object of the present invention is to provide a crystal growth apparatus for the EFG method.

The above problems are solved by the present invention described below. That is,
(1) The crystal growth apparatus for EFG method of the present invention includes at least a die having a slit, a crucible, a lid, and a plurality of heat reflecting plates, and the die is accommodated in the crucible, and the opening of the crucible except for the die Are covered with a lid, and are provided with a plurality of heat reflecting plates in order from the side where the crucible is installed, and each interval from the upper surface of the lid to the lower surface of the second and subsequent heat reflecting plates However, it is formed so as not to be a natural number multiple (however, excluding zero and 1 times) of the distance from the top surface of the lid to the bottom surface of the first heat reflecting plate.

  (2) In one embodiment of the crystal growth apparatus for EFG method of the present invention, at least two heat reflecting plates are provided, and the distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as a reference surface However, it is preferable that the length is set to be longer than twice the distance from the upper surface of the lid to the lower surface of the first heat reflecting plate.

  (3) In another embodiment of the crystal growth apparatus for EFG method of the present invention, it is preferable that the second heat reflecting plate is disposed above the upper end surface of the die.

  (4) In another embodiment of the crystal growth apparatus for EFG method according to the present invention, the distance from the upper surface of the lid to the lower surface of the first heat reflecting plate is a die having the upper surface of the lid as the reference surface. The distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as the reference surface is set to the upper surface of the die with the upper surface of the lid as the reference surface. It is preferable that the interval is set to be larger than this interval.

  (5) In another embodiment of the crystal growth apparatus for EFG method of the present invention, the heat reflecting plate is supported by a pin, a plurality of steps are formed on the pin, and the heat reflecting plate is supported by the step. It is preferable.

  (6) In another embodiment of the crystal growth apparatus for EFG method of the present invention, it is preferable that the pin has a cylindrical shape, and the diameter of the step becomes smaller as the distance from the lid increases.

  (7) In another embodiment of the crystal growth apparatus for the EFG method of the present invention, the crystal grown by the EFG method is a sapphire single crystal, the die has a plurality of slits, and the respective longitudinal directions are arranged in parallel. The die has a width of 2 to 8 inches, has at least two heat reflecting plates, the heat reflecting plate has a flat plate shape, and the shape seen from the plane direction is a die. The heat reflecting plate is shaped so that it is closer to both ends of the die than the center of the die, and the distance from the upper surface of the lid to the lower surface of the first heat reflecting plate is the reference surface of the lid The distance between the upper surface of the die and the upper surface of the die is set to be smaller, and the distance from the upper surface of the lid to the lower surface of the second heat reflecting plate is the die with the upper surface of the lid as the reference surface. It is set larger than the distance to the upper end surface of the pin Two step is formed, as a reference surface to the upper surface of the lid, the step of first one is 5 mm, it is preferable that the second of the step is formed to a height of 10.3 mm.

  According to the invention of (1), it is possible to make the heat distribution uniform in the upper part of the crucible, and to suppress the generation of bubbles during crystal growth. More preferably, as described in the invention of (2) above, the distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as the reference surface is the first heat with the upper surface of the lid as the reference surface. That is, it is set longer than twice the distance to the lower surface of the reflecting plate. With such a configuration, the second heat reflecting plate can be installed closer to the upper portion of the die, so that the heat distribution at the upper portion of the crucible can be made more uniform. . Accordingly, the generation of bubbles during crystal growth can be further suppressed.

  According to the invention of (3), in addition to the reflection of the radiant heat from the lid, the efficiency of the reflection of the radiant heat from the upper part of the die (the upper end surface of the die) is also improved. It becomes possible to make the heat distribution of the end face uniform. Therefore, a uniform and stable heat distribution can be formed over the crystal growth direction. Therefore, it is possible to further uniform the heat distribution in the upper part of the crucible, and to eliminate generation of bubbles during crystal growth.

  According to the invention of the above (4), in addition to the effect of the invention of the above (3), the first heat reflecting plate is disposed below the upper end surface of the die, so that the die phenomenon is caused by capillary action. It becomes possible to adjust the temperature gradient in the melt passing through the slit. Therefore, it is possible to prevent the occurrence of crystal side slip and grain boundary and improve the crystal quality.

  Furthermore, by suppressing the number of heat reflecting plates to two, the number of parts of the crystal growth apparatus for EFG method can be reduced and the cost can be reduced, and the function of each heat reflecting plate can be allocated (one sheet). Generation of side slip and grain boundary is prevented by the heat reflecting plate of the eye, and generation of bubbles during crystal growth can be eliminated by the second heat reflecting plate). Therefore, it is possible to prevent crystal defects of the grown crystal while minimizing the number of parts of the heat reflecting plate.

  According to the invention of (5), in addition to the above effects, a plurality of stages of heat reflectors can be easily installed in a short time at an optimal interval at which the heat distribution at the upper part of the crucible is made uniform. I can do it. Therefore, it is possible to install a plurality of stages of heat reflecting plates at optimum intervals with good reproducibility without depending on the skill of the installation operator. Therefore, the installation work can be prevented from becoming complicated, the installation work time can be shortened, and the installation work cost can be suppressed. Further, according to the invention of (6), in addition to the above effects, the heat reflecting plate can be easily supported on the pins, the installation work can be facilitated, and the work time can be further shortened. I can do it.

  According to the invention of (7) above, in addition to the above effects, even if the die width size is 2 inches or more and 8 inches or less, the heat at the upper part of the crucible depends on the die width size. It is possible to easily install the heat reflecting plate in a short time at an optimum interval at which the distribution is made uniform.

  Furthermore, since the die has a plurality of slits, a plurality of sapphire single crystals can be grown at once. Therefore, it is possible to grow a large inch-size sapphire single crystal suitable for market demand while improving the mass productivity of the sapphire single crystal.

  Furthermore, the shape when the heat reflecting plate is viewed from the plane direction is formed into a shape in which the heat reflecting plate is arranged closer to both ends of the die than the center of the die, so that both ends on the upper end surface of the die are By limiting the reflected heat to be irradiated, it is possible to further uniform the heat distribution over the entire upper end surface of the die. Accordingly, it is possible to more reliably eliminate the generation of bubbles during the growth of the sapphire single crystal.

It is a perspective view which shows typically the assembly state of a crucible, a die, a lid, a pin, a heat reflecting plate, and a shield in the crystal growth apparatus for EFG method according to the embodiment of the present invention. It is a perspective view which shows typically the state which the assembly of the crucible, die | dye, lid | cover, pin, heat | fever reflecting plate, and shield of FIG. 1 was completed. It is an enlarged view of the pin concerning the embodiment of the present invention. It is a top view of the heat reflection board concerning the embodiment of the present invention. It is a partial side view which shows typically the state of the relative position of the lid | cover, die | dye, a pin, and two heat | fever reflecting plates based on embodiment of this invention. It is a top view which shows typically the 3rd heat reflection board with which the crystal growth apparatus for EFG methods which are the modifications which concern on this invention is equipped. It is a perspective view which shows typically the state which the assembly of the die | dye, a lid | cover, a pin, and a heat reflection board was completed in the crystal growth apparatus for EFG methods which is the modification which concerns on this invention.

  The first feature of the present embodiment is that the crystal growth apparatus for the EFG method includes at least a die having a slit, a crucible, a lid, and a plurality of heat reflecting plates, and the die is accommodated in the crucible. The crucible opening is covered with a lid, and a plurality of heat reflecting plates are provided in order from the side where the crucible is installed. Each distance to the lower surface is formed so as not to be a natural number of times (excluding zero and 1 times) the distance to the lower surface of the first heat reflecting plate with the upper surface of the lid as a reference surface. That is.

  According to this configuration, each distance to the lower surface of the second and subsequent heat reflecting plates with the upper surface of the lid as the reference surface is set to the lower surface of the first heat reflecting plate with the upper surface of the lid as the reference surface. By forming it so that it does not become a natural number multiple of the interval (however, excluding zero and 1 times), it becomes possible to achieve a uniform heat distribution at the top of the crucible, and bubbles during crystal growth Can be suppressed.

  In the present invention, the heat reflecting plate refers to a plate disposed on the upper surface side of the lid, and the plate disposed on the upper surface side of the lid reflects radiant heat from the melt reservoir of the lid or die. It is defined as a heat reflecting plate having the function of

  The interval refers to an interval in a direction orthogonal to the surface direction of the upper surface of the lid when the lid and each heat reflecting plate are installed in parallel.

  The second feature of the present embodiment is that at least two heat reflecting plates are provided, and the distance from the upper surface of the lid to the lower surface of the second heat reflecting plate is the reference to the upper surface of the lid. That is, it is set to be longer than twice the distance to the lower surface of the first heat reflecting plate as the surface.

  According to this configuration, it is possible to install the second heat reflecting plate closer to the top of the die, so that the heat distribution at the top of the crucible can be made more uniform. Become. Therefore, the generation of bubbles during crystal growth can be further suppressed.

  In the present invention, the distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as the reference surface is twice the distance to the lower surface of the first heat reflecting plate with the upper surface of the lid as the reference surface. Is set to be longer than ((the distance from the upper surface of the lid to the lower surface of the second heat reflecting plate)> (2 × (the first image having the upper surface of the lid as the reference surface) The distance to the lower surface of the heat reflecting plate))).

  The distance from the top surface of the lid to the bottom surface of the second heat reflector is set to be longer than twice the distance from the top surface of the lid to the bottom surface of the first heat reflector. As a result, the distance between the heat reflectors is increased, which may adversely affect the uniform heat distribution at the top of the crucible, but the second heat reflector is closer to the top of the die. It has been proved by the experiment verification by the present applicant that it is important to make it installed in order to make the heat distribution uniform in the growth direction of the sapphire single crystal.

  The third feature of the present embodiment is that the second heat reflecting plate is arranged above the upper end surface of the die.

  According to this configuration, in addition to the reflection of radiant heat from the lid, the efficiency of radiant heat reflection from the top of the die (the top surface of the die) is also improved, and the heat distribution on the top surface of the die is reflected by the reflected heat. Can be made uniform. Therefore, a uniform and stable heat distribution can be formed over the crystal growth direction. Therefore, it is possible to further uniform the heat distribution in the upper part of the crucible, and to eliminate generation of bubbles during crystal growth.

  In the present invention, disposing the second heat reflecting plate above the upper end surface of the die means that the second heat reflecting plate is disposed above the upper end surface of the die. Shall.

  The fourth feature of the present embodiment is that the distance to the lower surface of the first heat reflecting plate with the upper surface of the lid as the reference surface is larger than the distance to the upper end surface of the die with the upper surface of the lid as the reference surface. The distance between the upper surface of the die and the upper surface of the die is set larger than the distance between the upper surface of the lid and the lower surface of the second heat reflecting plate with the upper surface of the lid as the reference surface. It is that.

  According to this configuration, in addition to the above effect, the first heat reflecting plate is disposed below the upper end surface of the die, so that the temperature gradient in the melt passing through the slit of the die due to capillary action can be increased. It becomes possible to adjust. Therefore, it is possible to prevent the occurrence of crystal side slip and grain boundary and improve the crystal quality.

  Furthermore, by suppressing the number of heat reflecting plates to two, the number of parts of the crystal growth apparatus for EFG method can be reduced and the cost can be reduced, and the function of each heat reflecting plate can be allocated (one sheet). Generation of side slip and grain boundary is prevented by the heat reflecting plate of the eye, and generation of bubbles during crystal growth can be eliminated by the second heat reflecting plate). Therefore, it is possible to prevent crystal defects of the grown crystal while minimizing the number of parts of the heat reflecting plate.

  The fifth feature of the present embodiment is that the heat reflecting plate is supported by a pin, a plurality of steps are formed on the pin, and the heat reflecting plate is supported by the step.

  According to this configuration, in addition to the above-described effects, a plurality of stages of heat reflecting plates can be easily installed in a short time at an optimum interval at which the heat distribution in the upper part of the crucible is made uniform. Therefore, it is possible to install a plurality of stages of heat reflecting plates at optimum intervals with good reproducibility without depending on the skill of the installation operator. Therefore, the installation work can be prevented from becoming complicated, the installation work time can be shortened, and the installation work cost can be suppressed.

  The sixth feature of the present embodiment is that the pin has a cylindrical shape, and the diameter of the step becomes smaller as it gets away from the lid.

  According to this configuration, in addition to the above effects, the heat reflecting plate can be easily supported on the pin, the installation work can be facilitated, and the work time can be further shortened.

  The seventh feature of the present embodiment is that the crystal grown by the EFG method is a sapphire single crystal, and the die has a plurality of slits and the longitudinal directions thereof are arranged in parallel. The die has a width of 2 inches or more and 8 inches or less, is provided with at least two heat reflecting plates, the heat reflecting plate is flat, and the shape seen from the plane direction is at the ends of the die rather than the center of the die. The heat reflecting plate is formed in a shape that is placed close to the upper surface of the die with the upper surface of the lid as the reference surface and the distance to the lower surface of the first heat reflecting plate as the reference surface. The distance between the upper surface of the die and the upper surface of the die with the upper surface of the lid as a reference surface is smaller than the distance between the upper surface of the die. Is set large, the pin is formed with two steps, the lid Top as a reference plane, the step of first one is 5 mm, is that The second step is a crystal growth apparatus for EFG method, which is formed to a height of 10.3 mm.

  According to this configuration, in addition to the above-described effects, even when the die width dimension is 2 inches or more and 8 inches or less, the heat distribution in the upper part of the crucible is made uniform according to the die width dimension. Therefore, it is possible to easily install the heat reflecting plate in a short time at an optimal interval.

  Furthermore, since the die has a plurality of slits, it is possible to grow a large inch-size sapphire single crystal suitable for market demand while improving the mass productivity of the sapphire single crystal.

  Furthermore, the shape when the heat reflecting plate is viewed from the plane direction is formed into a shape in which the heat reflecting plate is arranged closer to both ends of the die than the center of the die, so that both ends on the upper end surface of the die are By limiting the reflected heat to be irradiated, it is possible to further uniform the heat distribution over the entire upper end surface of the die. Accordingly, it is possible to more reliably eliminate the generation of bubbles during the growth of the sapphire single crystal.

  Hereinafter, an EFG crystal growth apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

  As shown in FIGS. 1 and 2, the crystal growth apparatus for EFG method according to the present embodiment (hereinafter referred to as “growth apparatus”) includes at least a die pack 2 having a slit, a crucible 1, a lid 3, and a plurality of heats. It comprises reflectors 5a and 5b (two in the embodiment of FIGS. 1 and 2) and a pulling container for pulling up the grown sapphire single crystal, and sapphire by the EFG (Edge-defined Film-fed. Growth) method. Growing and growing single crystals. Further, the growing apparatus includes a crucible driving unit, a heater, an electrode, and a heat insulating material (not shown).

  The sapphire single crystal is suitable as a substrate for epitaxial growth of a group III nitride semiconductor, a gallium nitride-based compound semiconductor or the like (hereinafter referred to as GaN etc., including both) which is a blue light emitting element material. This is because the lattice constant of the sapphire single crystal is relatively close to the lattice constant of GaN or the like, so that GaN or the like is easily grown epitaxially and the price is the lowest among such substrate materials.

  The crucible 1 is made of molybdenum and melts an aluminum oxide raw material that is a raw material of a sapphire single crystal. The crucible drive unit rotates the crucible 1 with the vertical direction as an axis. The heater heats the crucible 1. The electrode energizes the heater.

  The die pack 2 is housed and installed in the center of the crucible 1 and determines the liquid surface shape of the aluminum oxide melt (hereinafter simply referred to as “melt” as necessary) when pulling up the sapphire single crystal. The heat insulating material is installed so as to surround the crucible 1, the die pack 2, and the heater.

  The die pack 2 is made of molybdenum and has a plurality of partition plates. The partition plates have the same flat plate shape and are arranged in parallel to each other so as to form a minute gap (slit). The slit is provided over almost the entire width of the die pack 2. In addition, since the plurality of partition plates have the same shape and are arranged in parallel at predetermined intervals so that their longitudinal directions are parallel to each other, a plurality of slits are provided. In the embodiment of FIGS. 1 and 2, the die pack 2 is formed of a plurality of dies, has a plurality of slits, and is arranged in parallel with each other in the longitudinal direction. Furthermore, the upper part of each partition plate is formed with an inclined surface, and an acute angle opening is formed by arranging the inclined surfaces facing each other. The slit has a role of raising the melt from the lower end to the upper end (slit opening) of each die by capillary action.

  Since the die pack 2 has a plurality of slits, a plurality of sapphire single crystals can be grown at a time, so that the mass productivity of the sapphire single crystals is improved.

  Furthermore, the opening of the crucible 1 is covered with a lid 3. The lid 3 is provided with an opening having a shape corresponding to the outer peripheral shape of the die pack 2. The die pack 2 is inserted into the opening and the opening of the crucible 1 is covered. Accordingly, the opening of the crucible 1 is covered with a lid 3 except for the die pack 2 as shown in FIG. In addition, convex projections (not shown) are provided at the four corners of the die pack 2, and the die pack 2 and the lid 3 are fixed by fixing the projections and the four corners of the opening of the lid 3.

  The lid 3 is provided with a large number (several tens of holes) of holes, and the pins 4 are inserted into the holes. The outer shape of the pin 4 is formed in a cylindrical shape, and a plurality of steps 4a, 4b, 4c and cylindrical portions 4a1, 4b1, 4c1 are formed as shown in FIG. A pin 4 is inserted into each hole of the lid 3 and is locked by a step 4 c so that a large number of pins 4 are installed on the upper surface of the lid 3. In FIG. 1, the pin 4 is thinned out for the sake of easy viewing.

  Furthermore, heat reflection plates 5a and 5b are provided on the top of the lid 3 in order from the side where the crucible 1 is installed. Each of the heat reflection plates 5a and 5b is a flat plate and is formed in the same shape. In the embodiment of FIGS. 1 and 2, a growing apparatus provided with a pair of heat reflection plates 5 a and 5 b that are symmetrical one to one is illustrated. The two heat reflecting plates 5a and 5b are disposed on both the left and right sides of the side surface of the die pack 2.

  A number of holes 5a3 are provided in the first-stage heat reflecting plates 5a, 5a, and the cylindrical portion 4a1 of the pin 4 is inserted into the holes 5a3. The cylindrical portion 4a1 is inserted into each hole 5a3 and locked and supported by the step 4a, so that the heat reflecting plates 5a, 5a are parallel to the surface direction of the lid 3 and at a constant distance D1 from the upper surface of the lid 3. Is installed. The interval D1 is an interval from the upper surface of the lid 3 to the lower surface of the first-stage heat reflecting plates 5a and 5a in the orthogonal direction.

  Similarly, a number of holes 5b3 are provided in the second-stage heat reflecting plates 5b and 5b, and the cylindrical portion 4b1 of the pin 4 is inserted into the holes 5b3. The cylindrical portion 4b1 is inserted into each hole 5b3 and locked and supported by the step 4b, so that the heat reflecting plates 5b, 5b are parallel to the surface direction of the lid 3 and at a constant distance D2 from the upper surface of the lid 3. Is installed. The distance D2 is the distance from the upper surface of the lid 3 to the lower surface of the second-stage heat reflecting plates 5b and 5b in the orthogonal direction.

  For convenience of explanation, the surface of the lid 3 facing the melt stored in the crucible 1 is the lower surface, and the surface of the lid 3 opposite to the heat reflecting plate 5a is the upper surface.

  In the present invention, the distance D2 to the lower surface of the second heat reflecting plate 5b with the upper surface of the lid 3 as the reference surface is equal to the lower surface of the first heat reflecting plate 5a with the upper surface of the lid 3 as the reference surface. It is formed so as not to be a natural number multiple of the interval D1 (excluding zero times and 1 times). That is, D2 is not equal to (2, 3,..., N) × D1. More preferably, as shown in FIGS. 1, 2, and 5, in the case of a growth apparatus provided with two heat reflecting plates, the second heat reflecting plate 5b with the upper surface of the lid 3 as a reference surface. Is set to be longer than twice the distance D1 to the lower surface of the first heat reflecting plate 5a with the upper surface of the lid 3 as a reference surface. In the present invention, the fact that the interval D2 is set to be longer than twice D1 means that the relationship of D2> 2D1 is satisfied.

  More preferably, the second heat reflecting plate 5b is disposed above the upper end surface of the die pack 2 as shown in FIGS. In the present invention, the second heat reflecting plate 5b is disposed above the upper end surface of the die pack 2. The second heat reflecting plate 5b is disposed above the upper end surface of the die pack 2. It means to be. In the case of FIG. 5, the distance De from the upper surface of the lid 3 to the upper end surface of the die pack 2 with the reference surface as the reference surface is less than the distance D2 (De <D2).

  More preferably, the interval D1 is set lower than the interval De (D1 <De), and the interval D2 is set higher than the interval De (De <D2). That is, as shown in FIG. 5, it is the structure of the growing apparatus that satisfies D1 <De <D2.

  By setting D1 <D2, the distance between the heat reflecting plates 5a and 5b is increased, and at first glance, it seems to have an adverse effect on the uniform heat distribution in the upper part of the crucible 1. However, the second heat reflecting plate 5b is set closer to the upper portion of the die pack 2 (more preferably, as shown in FIGS. 2 and 5, the upper surface of the lid 3 and the upper end surface of the die pack 2 are set higher. The present applicant has derived from experimental verification that installation is important for achieving uniform heat distribution in the growth direction of the sapphire single crystal.

  The diameters of the holes 5a3 and 5b3 are set according to the diameters of the cylindrical portions 4a1 and 4b1, and the diameter of the hole 5b3 is smaller than the diameter of 5a3. Due to the difference in the diameter of the holes, the heat reflecting plates 5a and 5b at the upper and lower stages can be easily distinguished from each other, and an installation error can be prevented.

  Further, when the pin 4 is installed on the upper surface of the lid 3, the pin 4 is formed and installed so that the diameters of the steps 4a and 4b become smaller as the distance from the lid 3 increases. With such a configuration, the holes 5a3 and 5b3 can be easily inserted into the cylindrical portions 4a1 and 4b1 in this order. Therefore, the heat reflecting plates 5a and 5b can be easily supported on the pins 4, the installation work can be facilitated, and the work time can be further shortened.

  The shape of each heat reflecting plate 5a, 5b viewed from the plane direction is formed into a shape in which a part of the peripheral portion of each heat reflecting plate 5a, 5b is arranged closer to both ends than the center of the die pack 2. FIG. 4 illustrates a shape in which a notch 5a1 (5b1 in 5b) is partially formed in a half-moon shape. 1 and 2, the heat reflecting plates 5a and 5b are installed so that the edge portions of the notch 5a1 or 5b1 are close to both ends of the die pack 2. On the other hand, by forming the notch 5a1 or 5b1, the center of the die pack 2 is disposed farther from a part of the peripheral edge of each of the heat reflecting plates 5a and 5b than both ends thereof. Note that the lower surface of the lid 3 may be appropriately supported by a support, and the support may be installed through the notches 5a2 and 5b2 provided in the heat reflecting plates 5a and 5b. At that time, the lid 3 may be provided with a hole or notch for passing the support as necessary.

  Finally, a semicircular shield 6 is installed. 1 and 2 exemplify a growing apparatus in which the shield 6 is installed so as to cover the arc-shaped outer peripheral portions of the two heat reflecting plates 5a and 5b. Thus, since the shield 6 is provided so as to cover the growth direction of the sapphire single crystal by installing the shield 6 over the installation direction of the two heat reflecting plates 5a and 5b, the growth direction of the sapphire single crystal It is possible to suppress changes in the heat distribution in

  Next, a method for manufacturing a sapphire single crystal using the growth apparatus according to the present embodiment will be described. First, a predetermined amount of granulated aluminum oxide raw material powder (99.99% aluminum oxide), which is a sapphire raw material, is charged into a crucible 1 and filled. The aluminum oxide raw material powder may contain compounds and elements other than aluminum oxide depending on the purity or composition of the sapphire single crystal to be produced.

  Subsequently, the inside of the growth apparatus is replaced with argon gas, and the oxygen concentration is set to a predetermined value or less.

  Next, the crucible 1 is heated with a heater to melt the aluminum oxide raw material powder, thereby preparing an aluminum oxide melt. Furthermore, a part of the melt rises in the slit of the die pack 2 by capillary action, and a melt pool is formed in the upper part of the slit.

  Next, a plate-shaped sapphire single crystal is grown by bringing the seed crystal into contact with the melt surface and starting pulling up the seed crystal after the contact. Thereafter, the obtained sapphire single crystal is taken out from the growth apparatus.

  By filling the crucible 1 with the melt, radiant heat from the melt is radiated from the outside of the crucible 1 in all directions. In particular, the radiant heat radiated in the growth direction of the sapphire single crystal that is the upper part of the crucible 1 through the lid 3, and the growth direction of the sapphire single crystal that is also the upper part of the crucible 1 from the melt pool in the upper part of the die pack 2. The radiant heat radiated seems to directly influence the pulling direction accompanying the growth of the sapphire single crystal. However, in the present embodiment, the distance D2 to the lower surface of the second heat reflecting plate 5b with the upper surface of the lid 3 as the reference surface is defined as the lower surface of the first heat reflecting plate 5a with the upper surface of the lid 3 as the reference surface. It is formed so as not to be a natural number multiple of the interval D1 up to (but excluding zero and 1 times). Therefore, the heat distribution in the upper part of the crucible 1 can be made uniform, and the generation of bubbles during the growth of the sapphire single crystal can be suppressed.

  Furthermore, by constructing the growing apparatus so as to satisfy the relationship of D2> 2D1, the second heat reflecting plate 5b can be installed closer to the upper part of the die pack 2, so that the crucible 1 It becomes possible to further achieve uniform heat distribution in the upper part. Therefore, the generation of bubbles during the growth of the sapphire single crystal can be further suppressed.

  Further, by disposing the heat reflecting plate 5b above the upper end surface of the die pack 2, in addition to the reflection of the radiant heat from the lid 3 by the heat reflecting plate sub 5a, the upper portion of the die pack 2 (the upper end surface of the die pack 2). It is possible to improve the efficiency of reflection of radiant heat from and to make the heat distribution on the upper end surface of the die pack 2 uniform with the reflected heat. Therefore, a uniform and stable heat distribution can be formed over the growth direction of the sapphire single crystal. Therefore, it is possible to further uniform the heat distribution in the upper part of the crucible 1, and to eliminate the generation of bubbles during the growth of the sapphire single crystal.

  In addition to the above effects, the first heat reflecting plate 5a is disposed below the upper end surface of the die pack 2 in addition to the above effects by adopting a growth apparatus that satisfies D1 <De <D2 as shown in FIG. Therefore, the temperature gradient in the melt passing through the slit of the die pack 2 can be adjusted by capillary action. Therefore, the generation of side slip and grain boundary of the sapphire single crystal can be prevented, and the crystal quality of the sapphire single crystal can be improved.

  Furthermore, by limiting the number of heat reflecting plates to 5a and 5b, it is possible to reduce the number of parts of the EFG crystal growth apparatus and reduce the cost, and the functions of the heat reflecting plates 5a and 5b can be reduced. Can be allocated. Specifically, the occurrence of side slip and grain boundary is prevented by the first heat reflecting plate 5a, and the generation of bubbles during the growth of the sapphire single crystal can be eliminated by the second heat reflecting plate 5b. . Accordingly, it is possible to prevent crystal defects in the grown sapphire single crystal while minimizing the number of parts of the heat reflecting plate.

  Further, the heat reflecting plates 5a and 5b are supported by the pins 4, and a plurality of steps 4a and 4b are formed on the pins 4, and the heat reflecting plates 5a and 5b are supported by the steps 4a and 4b. In addition, the heat reflecting plates 5a and 5b having a plurality of stages can be easily installed in a short time at an optimum interval at which the heat distribution in the upper part of the crucible 1 is made uniform. Accordingly, it is possible to install a plurality of stages of the heat reflecting plates 5a and 5b at optimum intervals with good reproducibility without depending on the skill of the installation operator. Therefore, the installation work can be prevented from becoming complicated, the installation work time can be shortened, and the installation work cost can be suppressed.

  Furthermore, when the heat reflecting plates 5a and 5b are viewed from the plane direction, the shape of the peripheral portions of the heat reflecting plates 5a and 5b is arranged closer to both ends of the die pack 2 than the center of the die pack 2. By shaping, it is possible to limit the reflected heat applied to both ends at the upper end surface of the die pack 2 and to further uniform the heat distribution over the entire upper end surface of the die pack 2. Accordingly, it is possible to more reliably eliminate the generation of bubbles during the growth of the sapphire single crystal.

  In the present invention, the heat reflecting plate refers to a plate disposed on the upper surface side of the lid 3, and the plate disposed on the upper surface side of the lid 3 is from the melt pool of the lid 3 or the die pack 2. It is defined as a heat reflecting plate having a function of reflecting radiant heat. In the present embodiment, 5a and 5b are heat reflecting plates.

  The present invention can be variously modified based on its technical idea. For example, a third heat reflecting plate 7 as shown in FIG. 6 may be added to the upper surface of the lid 3 via the pins 4. The heat reflecting plate 7 has a flat plate shape, and the shape seen from the plane direction is a substantially quadrangular shape as shown in FIG. 6, and one side is formed in an arc shape.

  Further, as shown in FIG. 7, two symmetrical pairs are provided on the upper surface of the lid 3. In FIG. 7, the same overlapping numbers as those in FIGS. 1 to 5 are given the same drawing numbers, and the overlapping description is omitted or simplified. The heat reflecting plate 7 is also provided with a large number of holes 7a. The cylindrical portion 4a1 of the pin 4 is inserted into the hole 7a, and is locked and supported by the step 4a, so that it is parallel to the surface direction of the lid 3 and The heat reflecting plate 7 is installed at a constant distance D1 from the upper surface of the lid 3. At the time of installation, positioning is performed so that one side of the arc shape faces outward and one side of the opposing straight line is close to the die pack 2. The interval D1 is the interval from the upper surface of the lid 3 to the lower surface of the heat reflecting plates 5a and 7 in the orthogonal direction.

  Thus, by installing the heat reflecting plate 7 across the formation direction of the plurality of slits, it is possible to adjust the temperature gradient in the melt passing through the plurality of slits. Therefore, the generation of side slip and grain boundary of the sapphire single crystal can be prevented, and the crystal quality of the sapphire single crystal can be improved.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

  The growing apparatus in the present embodiment has the configuration shown in FIG. 7, and grows a sapphire single crystal by the EFG method. The width of the die pack 2 is set to a large size of 2 inches or more and 8 inches or less, and two heat reflecting plates 5a and 5b are provided. The inner diameter of the crucible 1 was either 322 mm or 400 mm.

  The heat reflecting plates 5a and 5b have a flat plate shape, and the shape seen from the plane direction is the shape shown in FIG. 4. When installed on the upper surface of the lid 3, the heat reflecting plates 5a and 5b The heat reflecting plates 5a and 5b are formed in a shape in which a part of the peripheral edge portion is disposed close to the heat reflecting plates 5a and 5b.

Further, as shown in FIG. 5, the configuration satisfies D1 <De <D2.

  The pin 4 is formed with at least two steps 4a and 4b. Furthermore, with the upper surface of the lid 3 as a reference surface, the height dimension to the first step 4a is 5 mm, and the height dimension to the second step 4b is 10.3 mm. Therefore, from FIG. 5, the interval D1 is set to 5 mm, and the interval D2 is set to 10.3 mm.

  A sapphire single crystal having a size of 2 inches or more and 8 inches or less was grown using the above growth apparatus. As the sapphire raw material, granulated aluminum oxide raw material powder (99.99% aluminum oxide) was used. The inside of the growth apparatus is replaced with argon gas, and the oxygen concentration is set to a predetermined value or less.

  Next, the crucible 1 is heated with a heater, the aluminum oxide raw material powder is melted to prepare a melt, a melt pool is formed in the upper part of the slit, the seed crystal is brought into contact with the melt surface, and the seed crystal is pulled up to form a flat plate. Shaped sapphire single crystals were grown.

  When the crystal quality of the grown sapphire single crystal was evaluated, no occurrence of side slip or grain boundary was confirmed, and generation of bubbles was not confirmed. From the above, when growing a sapphire single crystal of 2 inches or more and 8 inches or less, setting the distance D1 to 5 mm and the distance D2 to 10.3 mm achieves uniform heat distribution in the upper part of the crucible 1. As a result, it was found that this was the optimum setting value in that the generation of bubbles during the growth of the sapphire single crystal could be eliminated.

  At the same time, when the distance D1 was removed from 5 mm or the distance D2 was removed from 10.3 mm, occurrence of side slip, grain boundary, or generation of bubbles was confirmed. Accordingly, in growing a sapphire single crystal over a range of 2 inches to 8 inches, the melting point of the aluminum oxide raw material powder (about 2050 ° C. to 2072 ° C.), the dimensions of the crucible 1 and the dimensions of the crucible 1 From the relationship with the amount of radiant heat radiated, experimental verification revealed that the combination of setting the interval D1 to 5 mm and setting the interval D2 to 10.3 mm is optimal in terms of crystal quality.

  In this embodiment, with the upper surface of the lid 3 as a reference surface, the height of the pin 4 up to the first step 4a is 5 mm and the height of the second step 4b is 10.3 mm. ing. Therefore, the heat reflecting plates 5a and 5b can be easily installed in a short time at the installation values of the distances D1 and D2 as described above.

  The reason why the sapphire single crystal is set to 2 inches or more and 8 inches or less is because it is excellent in handling property when taking out the grown sapphire single crystal while satisfying the demand for larger size, and is most suitable for mass production. is there.

  Furthermore, by increasing the mass productivity of the sapphire single crystal by having the plurality of slits in the die pack 2, it is possible to grow a sapphire single crystal having a size of 2 inches to 8 inches, which is a large inch size suitable for market demand. I can do it.

Comparative example

  Below, the comparative example with respect to the said Example is demonstrated. In this comparative example, the description of the parts and processes that overlap with the above-described embodiment is omitted or simplified, and different parts and processes will be described mainly.

  The comparative example is different from the embodiment in that the second heat reflecting plate 5b is disposed below the upper end surface of the die pack 2. That is, De> D2 was set.

  Evaluation of the crystal quality of the sapphire single crystal of the flat plate shape grown and grown showed no occurrence of side slip or grain boundary, but generation of bubbles was confirmed in 55% of the number of samples. Therefore, it has been found that the sample non-defective rate falls below 50% with the mixing of bubbles.

1 crucible 2 die 3 lid 4 pin
4a, 4b, 4c steps
4a1, 4b1, 4c1 Cylindrical part
5a, 5b, 7 Heat reflector
5a1, 5b1, 5a2, 5b2 Notch
5a3, 5b3, 7a Hole 6 Shield

Claims (7)

The crystal growth apparatus for the EFG method includes at least a die having a slit, a crucible, a lid, and a plurality of heat reflecting plates,
The die is stored in the crucible,
Except for the die, the crucible opening is covered with a lid,
A plurality of heat reflection plates are provided in order from the side where the crucible is installed,
Each interval to the lower surface of the second and subsequent heat reflecting plates with the upper surface of the lid as the reference surface is a natural number multiple of the interval to the lower surface of the first heat reflecting plate with the upper surface of the lid as the reference surface (however, The crystal growth apparatus for the EFG method is formed so as not to become zero and 1 times. At least two of the heat reflecting plates are provided,
The distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as the reference surface is twice the interval to the lower surface of the first heat reflecting plate with the upper surface of the lid as the reference surface. The crystal growth apparatus for EFG method according to claim 1, which is set longer.   The crystal growth apparatus for an EFG method according to claim 1, wherein the second heat reflecting plate is disposed above the upper end surface of the die. The distance to the lower surface of the first heat reflecting plate with the upper surface of the lid as a reference surface is set smaller than the distance to the upper end surface of the die with the upper surface of the lid as a reference surface,
The distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as a reference surface is set larger than the distance to the upper end surface of the die with the upper surface of the lid as a reference surface. Item 4. The crystal growth apparatus for EFG method according to any one of Items 1 to 3. The heat reflecting plate is supported by pins;
The crystal growth apparatus for EFG method according to claim 1, wherein a plurality of steps are formed on the pin, and the heat reflecting plate is supported by the steps.   The crystal growth apparatus for an EFG method according to claim 5, wherein the pin has a cylindrical shape, and the diameter of the step becomes smaller as the distance from the lid increases. The crystal grown by the EFG method is a sapphire single crystal,
The die is formed from a plurality of slits having a plurality of slits and the longitudinal directions of the dies arranged in parallel.
The width of the die is not less than 2 inches and not more than 8 inches;
At least two of the heat reflecting plates are provided,
The heat reflecting plate has a flat plate shape, and the shape seen from the plane direction is molded into a shape in which the heat reflecting plate is arranged closer to both ends of the die than the center of the die,
The distance to the lower surface of the first heat reflecting plate with the upper surface of the lid as a reference surface is set smaller than the distance to the upper end surface of the die with the upper surface of the lid as a reference surface,
The distance to the lower surface of the second heat reflecting plate with the upper surface of the lid as a reference surface is set larger than the distance to the upper end surface of the die with the upper surface of the lid as a reference surface,
7. The step according to claim 5, wherein two pins are formed on the pin, and the first step is formed at a height of 5 mm and the second step is formed at a height of 10.3 mm with the upper surface of the lid as a reference surface. Crystal growth equipment for EFG method.

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