JP2006232605A - Method of and apparatus for producing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of efficiently producing a bulk single crystal by a liquid phase epitaxial method for bringing a seed crystal into contact with the melt of a single-crystal raw material heated in a crucible and pulling up the seed crystal from the melt to grow a single crystal. <P>SOLUTION: While uplifting and induction-heating the melt 4 by applying thereto, the Lorentz force induced by energization of AC current to a normal conductive coil 5, the seed crystal 7 is brought into contact with the vicinity of top of the uplifted melt to grow the single crystal 15 on the seed one. The rapid thermal-flux amount change of the crystal is prevented by auxiliary-heating the vicinity of the crystal 5 or 15 in the non-steady processes in the vicinity of crystal growth start and/or completion to obtain the good quality crystal having no crack. The auxiliary heating is performed by induction heating with the lifted coil 5 or another coil and/or immersion of a tool 13 in the melt. If the tool 13 is meltable in the melt, it also achieves the adjustability of melt composition necessary for heteroepitaxial growth. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a manufacturing method and a manufacturing apparatus by liquid phase epitaxial growth (LPE method) of silicon carbide (SiC) or other single crystal used as a semiconductor material or the like. The method and apparatus for producing a single crystal of the present invention enables the growth of a single crystal having a high quality and a practical size.

  Silicon carbide is a kind of thermally and chemically stable compound semiconductor. Compared to silicon, silicon carbide is about three times the band gap, about ten times the dielectric breakdown voltage, about twice the electron saturation speed, and about three times. It exhibits advantageous properties such as thermal conductivity coefficient. Therefore, silicon carbide is expected to be used as a substrate material for new electronic devices.

  The manufacturing technology of single crystal, which is a substrate material for wide band gap semiconductors with a larger band gap than silicon, such as silicon carbide, gallium arsenide, gallium nitride, aluminum nitride, and diamond, is a vapor phase growth method such as sublimation or chemical vapor deposition. It is roughly classified into a phase growth method (CVD method) and a liquid phase epitaxial method (LPE method). However, when applied on an industrial scale, all of these methods have significant problems.

In general, it is known that a single crystal produced by a sublimation method has a large number of lattice defects. For example, in the case of SiC, at the time of sublimation, SiC is once decomposed and vaporized into Si, SiC ₂ , Si ₂ C, etc., and at the same time, graphite is sublimated, but the gas that reaches the surface of the single crystal substrate depending on the temperature The species is different. It is difficult to control these partial pressures stoichiometrically accurately. For this reason, a specific element or molecule is excessively precipitated in the crystal and easily becomes a defect. In addition, the sublimation method has a drawback that polymorphic dislocations are easily generated.

Since the CVD method supplies the raw material by gas, it is difficult to increase the supply amount of the raw material, and is not practical as a bulk (large-size) single crystal growth method.
In the LPE method, for example, in the case of SiC, a Si melt is accommodated in a crucible (for example, a graphite crucible) containing carbon as a constituent element, and SiC is produced by reacting Si with carbon in the crucible. The melt is turned into a SiC solution (ie, liquid raw material) and a temperature gradient is generated, and the single crystal substrate attached to the tip of the crystal holder is in a supercooled (supersaturated solution) state. In general, a SiC single crystal is grown on a substrate by dipping in a low temperature portion of a SiC solution. Normally, a temperature gradient is formed in the SiC solution so that the upper part is cooler than the lower part, the single crystal substrate at the tip of the crystal holder is brought into contact with the liquid surface of the Si melt, and the crystal is retained as the SiC single crystal grows. Pull up the ingredients.

  The SiC single crystal obtained by the LPE method generally has the features that there are few defects and few defects that cause polymorphic transition. However, when a single crystal growth is performed for a long time in order to obtain a bulk single crystal by the LPE method, the vicinity of the crystal holder immersed in the low temperature part of the crucible, the low temperature part of the SiC solution, or the surface of the SiC solution, etc. As a result of heat removal, the temperature becomes lower than that of the single crystal growth portion, and many polycrystals grow there. When the polycrystal grows, the growth of the single crystal is hindered, so that it is difficult to obtain a bulk single crystal. Therefore, in the present situation, only a thin SiC single crystal can be formed on a single crystal substrate in the growth of an SiC single crystal by the LPE method. In addition, in the LPE method, the growth temperature of the SiC single crystal is about 300 ° C. higher than the melting point of Si, so that the SiC concentration in the SiC solution increases due to the vaporization of Si and is easily oversaturated, and polycrystals are likely to be formed. There is also a problem.

The following technique has been proposed as an improvement of the LPE method for growing a bulk SiC single crystal.
In the following Patent Document 1, the carbon of the crucible is dissolved in the Si melt in a state where the periphery of the crucible containing carbon is insulated and soaked, and the SiC single crystal is applied to the seed crystal brought into contact with the surface of the generated SiC solution. A method of growing is disclosed. It is characterized in that the temperature of the melt surface is adjusted using heating means such as an induction heated carbon block or resistance heater installed above the SiC solution, but the temperature of the melt surface is adjusted by radiant heating. It seems difficult to do. If the heat insulation is successfully achieved by this method, there is no temperature gradient in the SiC solution, and therefore growth of a single crystal cannot be expected or even if it grows, an increase in growth rate cannot be expected.

In Patent Document 2 below, a raw material containing at least one transition metal, silicon, and carbon is heated and melted in a carbonaceous crucible to form a SiC solution, and the SiC solution is cooled, or a temperature gradient is applied to the SiC solution. A method is disclosed in which a SiC single crystal is deposited and grown on a seed crystal by forming. It has been explained that the growth of SiC polycrystals in places other than the seed crystal can be suppressed because the vapor pressure of the SiC solution can be lowered by selecting an appropriate transition metal. It is difficult to suppress the growth of polycrystals by suppressing the supersaturation of the SiC concentration. In addition, there is no disclosure of a special technique for the generation of polycrystals in a low-temperature part such as a low-temperature part of a crucible, a crystal holder, or the vicinity of the surface of a SiC solution. Is difficult.
JP-A-7-172998 JP 2000-264790 A

  An object of the present invention is to provide a single crystal manufacturing method and a manufacturing apparatus capable of efficiently manufacturing a bulk single crystal by the LPE method without the above-mentioned problems such as growth of polycrystals and increase in crystal defects. To do.

  The present inventors raised the melt by utilizing the Lorentz force induced by passing an alternating current through the normal coil, and brought the seed crystal into contact with the apex of the raised melt on the seed crystal. A single crystal manufacturing method has been developed to grow bulk single crystals by liquid phase epitaxial growth. In this method, the melt subjected to high-frequency induction heating rises from the side surface, so that the area of the melt side surface subjected to heating increases, heating is promoted, and at the same time, the distribution of non-uniform Lorentz force in the melt is increased. As a result, the melt is electromagnetically stirred. In addition, by placing the normal coil below the top of the raised melt and immersing the crystal holder in the melt surface layer, a vertical temperature gradient is formed in the melt so that the top of the raised portion is at a low temperature. Is done. Therefore, it becomes possible to grow a single crystal at a practical growth rate while suppressing the growth of the polycrystal.

  However, in order to use a special furnace in which the melt is induction-heated from the side and a part of the crucible is cooled, compared to the techniques described in Patent Documents 1 and 2, due to the structure of this furnace. The ambient temperature in the vicinity of the crystal holder, that is, in the vicinity of the crystal growth site is lowered. For this reason, especially when the seed crystal is brought into contact with the melt to start single crystal growth, or when the seed crystal on which the single crystal has grown after the epitaxial growth is completed is recovered from the melt, the amount of heat flux received by the crystal is reduced. It has been found that there is a disadvantage that the crystal changes greatly in a short time and cracks are likely to occur in the crystal.

  Further, when a single crystal substrate that can be used as a seed crystal has not been obtained, heteroepitaxial growth using a single crystal substrate having a lattice arrangement similar to the target crystal is required. In that case, it is required to suppress the generation of cracks and to appropriately control the melt composition to promote heteroepitaxial growth of the target crystal.

  The present invention provides a method for producing a single crystal in which a melt is raised using the Lorentz force described above, and prevents the occurrence of cracks inside the crystal at the start or completion of the growth of the single crystal and, if necessary, heteroepitaxial growth. A method for manufacturing a single crystal and a manufacturing apparatus are provided.

The method for producing a single crystal according to the present invention comprises a single crystal grown by bringing a seed crystal into contact with a melt in which a single crystal raw material heated in a crucible is dissolved, and pulling the seed crystal from the melt. In the manufacturing method,
The seed crystal is brought into contact with the apex of the raised melt while the Lorentz force induced by the application of alternating current to the normal conducting coil is applied to the melt to cause the rise and induction heating of the melt. Grow a single crystal on top,
Further, by auxiliary heating in the vicinity of the seed crystal in the unsteady process before and after the start of crystal growth and / or in the vicinity of the growth crystal in the unsteady process before and after the end of crystal growth, the seed crystal and / or Or prevent rapid changes in the heat flux of the growing crystal,
It is the method characterized by this.

  The present invention also relates to a single crystal manufacturing apparatus. The single crystal production apparatus of the present invention includes a crucible for holding a melt of a single crystal raw material, a crystal holder that can be raised and lowered that can hold a seed crystal at the tip, and generates Lorentz force in the melt. A normal coil that can heat up the melt at the same time and induction heating, and a means that can auxiliaryly heat the vicinity of the seed crystal and the grown crystal in the unsteady process before and after the start and end of crystal growth, respectively. It is characterized by providing.

Hereinafter, the vicinity of the seed crystal at the start of the auxiliary crystal growth and the vicinity of the grown crystal at the end of the crystal growth are collectively referred to as a crystal growth portion.
In the single crystal production method and production apparatus of the present invention, the auxiliary heating in the vicinity of the crystal growth site is performed by (1) non-contact heating means with respect to the melt heating site, for example, electromagnetic induction heating, or ( 2) It is performed by bringing a jig made of a part of the composition constituting the melt into contact with the melt (in this case, a part of the jig in contact with the melt simultaneously with the heating is in the melt). (In the following, this jig is referred to as an auxiliary heating / component adjustment jig) or a combination of (1) and (2).

  Auxiliary heating by electromagnetic induction heating is performed by changing the position of the normal conductive coil so that the vicinity of the crystal growth site is heated by an appropriate lifting jig, or is installed at a position for heating the vicinity of the crystal growth site. The normal conducting coil may be different from the normal conducting coil.

  The crucible in the single crystal production apparatus of the present invention can be composed of a first crucible member that comes into contact with the melt and a second crucible member made of a conductive material that surrounds the side peripheral surface of the melt. In that case, the normal conducting coil is arranged around the second crucible member, and the second crucible member has a plurality of slits in a direction substantially orthogonal to the winding direction of the normal conducting coil, and further the second crucible member. There may be means for cooling. The top surface of the first crucible member can have a recess at a distance from the second crucible member.

  In the following description, “the Lorentz force is used to elevate the melt and promote induction heating, and the seed crystal is brought into contact with the apex of the raised melt and the liquid is applied on the seed crystal. The method of growing a bulk single crystal by phase epitaxial growth is called a “cooled crucible liquid phase epitaxy (CC-LPE) method” because a part of the crucible is cooled.

  On the other hand, the liquid phase epitaxial growth method employed in Patent Documents 1 and 2 is called a “heated crucible liquid phase epitaxy (HC-LPE) method” because a heated crucible is used.

  Compared with the HC-LPE method, the CC-LPE method has a lower temperature for the crystal holder that holds the single crystal substrate that is the seed crystal. The temperature around the growth crystal (that is, the vicinity of the crystal growth site) is low. FIG. 1 is a longitudinal sectional view showing a state of manufacturing a single crystal of the CC-LPE method, and FIG. 2 is a partially broken perspective view showing an example of a crucible structure at that time.

  In the CC-LPE method, the temperature in the vicinity of the crystal holder 1 and the crystal growth site becomes low, as shown in FIG. 2, around the crystal holder 1 holding the seed crystal single crystal substrate 7 around the side wall of the crucible. This is because the side walls are cooled by flowing cooling water through the double pipes arranged in the segments 8 constituting the crucible. Thus, the low temperature in the vicinity of the crystal growth site has the advantage that the temperature gradient (which becomes the driving force for crystal growth) formed in the liquid raw material 4 increases, and a large crystal growth rate can be obtained. Moreover, since induction heating is performed from the surface layer of the liquid raw material, there is another advantage that crystals can be grown under low temperature conditions compared to the HC-LPE method, and crystals having a structure that cannot be grown by the HC-LPE method can be obtained. .

  Since the crystal holder 1 is at a distance away from the energizing coil 5 constituting the normal conducting coil, the liquid raw material 4 in a molten state rather than induction heating by the energizing coil 5 (this is heated by induction heating by the energizing coil 5). Heated by conduction heat transfer from For this reason, immediately after the single crystal substrate 7 attached to the tip of the crystal holder 1 is brought into contact with the liquid raw material 4, the amount of heat flux from the single crystal substrate 7 toward the crystal holder 1 rapidly increases in a short time. Therefore, cracks are likely to occur in the crystal due to the thermal shock.

  On the other hand, when the epitaxial growth is completed and the crystal is detached from the liquid raw material 4, the amount of heat flux from the single crystal substrate 7 toward the crystal holder 1 rapidly decreases in a short time. Cracks tend to occur. In particular, since the grown crystal is rich in wettability by the liquid raw material 4, when the crystal holder 1 is raised to detach the grown crystal from the liquid raw material 4, the free surface of the liquid raw material 4 adheres to the crystal due to interfacial tension. After being pulled up and slightly raised, the crystal is detached from the liquid raw material 4 when the gravity becomes greater than the interfacial tension, and the free surface drops rapidly. The amount of change (decrease) in the heat flux that the crystal is subjected to at this time is generally larger than the amount of change (increase) in the heat flux when the crystal is in contact with the liquid raw material, so the thermal shock is greater at the end of growth, The situation is such that cracks in the crystal (ie, the grown crystal) are more likely to occur.

  In the present invention, in order to mitigate a rapid change in heat flux applied to the crystal at the beginning and end of crystal growth, not only the crystal is heated by conduction heat transfer through the liquid raw material, but also the start of crystal growth and / or In the final stage, the vicinity of the crystal growth site is heated using an additional controllable auxiliary heating means.

  As this auxiliary heating means, a heating means such as electromagnetic induction heating capable of non-contact heating capable of controlling the amount and time required for the crystal growth site can be adopted. However, in the case of heteroepitaxial growth using a seed crystal different from the grown crystal (which causes lattice mismatch), it is necessary to prevent dissolution of the seed crystal. An auxiliary heating means that can adjust the composition of the liquid raw material is desirable. As a heating means for this purpose, an auxiliary heating and component adjustment jig that has the function of adjusting the composition of the liquid raw material by dissolving when it comes into contact with the liquid raw material is crystal-grown. It can be placed around the site.

(1) Electromagnetic induction heating One method of avoiding a sudden change in the amount of heat flux with respect to the crystal at the start or end of epitaxial growth, i.e., when the crystal growth is in an unsteady state, is possible without contaminating the heating object. Heating a crystal or a crystal holder using electromagnetic induction, which is a non-contact heating means capable of applying thermal energy. Electromagnetic induction heating includes high-frequency heating, microwave heating, dielectric heating, and the like depending on the frequency band to be used.

  During epitaxial growth in a steady state, it is better not to promote induction heating in the vicinity of the crystal growth site from the viewpoint of realizing a temperature gradient (crystal growth surface becomes a low temperature) as a driving force for crystal growth in the liquid raw material. However, in the unsteady stage at the start or end of growth, if the vicinity of the crystal growth site remains at a low temperature, the thermal shock increases, so induction heating in the vicinity of the crystal growth site is promoted to increase the temperature of this part. It is advantageous to prevent the occurrence of crystal cracks.

  In order to achieve this, the induction heating must be able to control the heating position and time as well as the amount of heat. For example, in the case of high-frequency heating, the energizing coils (normal conducting coils) are divided into a plurality of parts, and the power supplied to each energizing coil is controlled (for example, the energizing coils near the crystal growth site are only required when auxiliary heating is required. (Applying electric power) or raising and lowering the energizing coil so that the energizing coil is brought close to the crystal growth site at a necessary time.

  On the other hand, while the epitaxial growth is in a steady state, the liquid source requires a temperature gradient in which the crystal growth site is at a low temperature, so the applied power to the energizing coil close to the crystal growth site is reduced, cut off, or crystal growth occurs. It is only necessary to keep the energizing coil away from the site.

  As a means for controlling electromagnetic induction heating, in addition to a coil raising / lowering jig that makes the distance to the crystal to be auxiliary heated variable, a method for controlling energy attenuation such as placing an induction shielding plate between the crystal and the coil Can also be used.

(2) Auxiliary heating / component adjustment jig In the case of the LPE method using a seed crystal, a seed crystal is not obtained depending on the type of crystal, and a seed crystal that causes lattice mismatch with the single crystal to be manufactured is used. Heteroepitaxial growth may be necessary. In the case of heteroepitaxial growth, homoepitaxial growth from a seed crystal often occurs, and a crystal different from the intended purpose may grow. In such a case, it is necessary not only to suppress crystal cracking but also to control the structure of the grown crystal. It is also necessary to prevent the seed crystal from dissolving after the seed crystal is brought into contact with the liquid raw material until the target crystal begins to grow.

  For this purpose, an auxiliary heating / component adjustment jig that melts in contact with the liquid raw material can be used. The material of the jig is composed of components included in the composition constituting the liquid raw material. When a part of the jig is dissolved and enters the liquid raw material, the amount of seed crystal dissolved is controlled. Such a jig is heated by being in contact with the liquid raw material, heats the vicinity of the jig, and changes part of the composition of the liquid raw material to suppress homoepitaxial growth of the seed crystal.

  When performing heteroepitaxial growth, while the heteroepitaxial growth is in a steady state, an auxiliary heating / component adjustment jig is used from the viewpoint of realizing a temperature gradient in which the crystal growth site has a low temperature in the liquid material and continuing crystal growth. It is better not to. Conversely, in the non-stationary stage, particularly at the beginning of crystal growth, the temperature gradient is relaxed using auxiliary heating and component adjustment jigs, and the liquid raw material components are adjusted to promote heteroepitaxial growth (homogeneous growth). It is desirable to suppress the growth of the seed crystal while suppressing the epitaxial growth.

  The auxiliary heating / component adjustment jig exhibits the intended function by contacting with the liquid raw material. For example, the auxiliary heating / component adjustment jig has a substantially tubular shape that circulates around the crystal, and includes a mechanism that allows the auxiliary heating / component adjustment jig to move up and down. As a result, when the auxiliary heating / component adjustment jig is lowered and immersed in the liquid raw material, the temperature of the crystal growth site located inside the jig is raised to alleviate the temperature gradient, and at the same time a part of the jig Can be dissolved in the liquid raw material, and the composition of the liquid raw material can be changed to a composition suitable for it when heteroepitaxial growth is required.

  On the other hand, at the stage of crystal growth where the crystal growth proceeds and the single crystal substrate is covered with the target heteroepitaxially grown crystal in a steady state, the auxiliary heating / component adjustment jig is raised so as to be detached from the liquid raw material. . As a result, the ambient temperature in the vicinity of the crystal growth site is lowered and a predetermined temperature gradient is obtained, and the composition of the liquid raw material is returned to the original, and a liquid raw material composition suitable for the intended crystal growth can be realized.

  The ambient temperature control means using the auxiliary heating / component adjustment jig is not limited to the method of immersing the auxiliary heating / component adjustment jig in the liquid material as described above. A method of conducting heating and a method of combining with the electromagnetic induction heating described above can be used together to increase heating efficiency and promote dissolution in a liquid raw material.

  According to the method and apparatus for producing a single crystal according to the present invention, the CC-LPE method, which does not easily generate polycrystals, suppresses a rapid change in the amount of heat flux at the beginning or end of crystal growth, and cracks are observed inside. High-quality bulk single crystals can be produced efficiently. As a result, it is possible to produce a high-quality bulk single crystal by the LPE method, which has been difficult in the past.

  In the following description, the present invention will be described with respect to the production of silicon carbide or aluminum nitride single crystals, but the single crystals that can be produced according to the present invention are not limited thereto. The present invention can also be applied to the production of single crystals of various compounds, such as gallium arsenide, gallium nitride, and diamond, to which the LPE method has conventionally been applied.

  First, an outline of a basic cooling crucible liquid phase epitaxial growth (CC-LPE) method will be described with reference to FIG. 1 (longitudinal sectional view of the apparatus) and FIG. 2 (partially broken perspective view of the crucible). Specific examples relating to the production of crystals will be described.

  The crucible substantially comprises a side wall portion, a first crucible member 2 that does not contact the liquid raw material (melt) 4, and a second crucible member 3 that substantially constitutes the bottom surface portion and contacts the liquid raw material 4. It consists of two members. The first crucible member 2 has a substantially cylindrical shape with an inner diameter of about 100 mm and a height of about 300 mm, and is made of a copper material. As shown in FIG. 2, the wall of the first crucible member 2 is shorter than the height of the first crucible member 2 but is longer than the winding height of the current-carrying coil 5 that is a normal conducting coil and has a vertical direction. It is assembled from a plurality of segments 8 that are insulated from each other in the circumferential direction through slits 6 that have an insulating function. Since the induction current generated from the energizing coil is blocked by the slit, the first crucible member cannot flow in the circumferential direction but flows from the outside to the inside, and the Lorentz force can be efficiently generated in the melt. . The winding height of the energizing coil 5 and the length of the slit 6 are about 100 mm and about 200 mm, respectively.

  Each of the plurality of segments 8 can be cooled by passing cooling water through a double pipe installed inside. During operation, the temperature of the first crucible member 2 is maintained at a temperature that does not rise above 100 ° C. above the temperature of the cooling water. The upper part of the first crucible member 2 is an opening 9 having a circular cross section with an inner diameter of about 100 mm, and the crystal holder 1 can be inserted into the crucible from this opening.

  The second crucible member 3 is housed therein in a state where it partially contacts the inner wall of the first crucible member 2. The gap between the first crucible member 2 and the second crucible member 3 is 1 mm in a wide area and 0 mm in a narrow area (both are in contact). The main material of the second crucible member 3 is carbon (eg, graphite).

  On the outer periphery of the first crucible member 2, a current-carrying coil 5, which is a normal conductive coil, is arranged in a multiple spiral winding structure of about 4 to 5 turns in such a manner that one turn is included in a substantially horizontal plane. That is, the winding direction of the slit 6 and the energizing coil 5 is in a positional relationship in a substantially orthogonal direction. There is no point at which the energization coil 5 and the first crucible member 2 come into contact with each other, and there is no point between them, and the distance between them is about 1 mm when they are close and about 10 mm when they are apart. The energizing coil 5 is connected to a high frequency power source (not shown) through a bus bar (not shown). The maximum output of the high frequency power supply is 300 kW, and the frequency is variable between 5 kHz and 30 kHz.

The upper surface of the second crucible member 3 has a concave shape, which is raised near the first crucible member 2 and is depressed near the center away from the first crucible member 2. Depending on the type, a flat shape may be used. The change of the undulation on the upper surface of the second crucible member 3 is about 20 mm. A space surrounded by the upper surface of the second crucible member 3, the side wall of the first crucible member 2 and the opening 9 is a free space 10, in which the liquid raw material 4, gas 12, single crystal substrate 7, crystal Part of the holder 1 can be accommodated. The volume of the free space 10 is approximately 1200 cm ³ .

  The crystal holder 1 that can be moved up and down and is inserted into the crucible from the opening 9 has a length of about 500 mm and a diameter that varies depending on the height, but the tip is 30 mm and the vicinity of the root is 60 mm. The crystal holder 1 is mainly made of a carbon material. A single crystal substrate 7 having a diameter of about 30 mm is attached to the tip of the crystal holder 1 as a seed crystal. The single crystal substrate 7 may be the same as the substance to be crystallized (epitaxial growth) dissolved in the liquid raw material or may be different from the substance to be crystallized (heteroepitaxial growth).

The first crucible member 2, the second crucible member 3, a part of the crystal holder 1, a part of the energizing coil 5, etc. are partially water-cooled chambers capable of increasing / decreasing pressure, supplying and evacuating gas 12. 11, and a gas supply device (not shown), a vacuum pump (not shown), an exhaust gas treatment device (not shown), and the like are connected to the chamber 11. The chamber 11 has airtightness and pressure resistance, the internal volume is about 35000 cm ³ , and the material is stainless steel. The chamber 11 is appropriately equipped with valves, pressure gauge P, flow meter, thermocouple insertion port, radiation thermometer window, observation window, and the like necessary for operation. The first crucible member 2 and the second crucible member 3 may be rotated in the same direction at substantially the same speed with the substantially vertical direction as the rotation axis. Furthermore, the crystal holder 1 can also be rotated.

  When a solid raw material (for example, Si or Si and other metal) is charged on the second crucible member of the above apparatus, and the inside of the chamber is appropriately evacuated, an AC current is passed through the energizing coil from a high-frequency power source. The raw material is induction-heated and melted, and at the same time, the generated melt rises like a dome as shown in the figure by the Lorentz force induced by the energization. When induction heating is continued in this state, carbon is dissolved in the melt from the second crucible member 3 in contact with the melt, and the melt becomes an SiC solution, that is, the liquid raw material 4. Since the liquid raw material 4 is induction-heated and electromagnetically stirred at the same time, its SiC concentration is relatively uniform. The energizing coil 5 is arranged so that its uppermost portion is lower than the top of the raised liquid raw material 4, so that a temperature gradient in the vertical direction is formed in the liquid raw material 4 such that the temperature of the top of the liquid raw material 4 is lowered. The

  When the SiC concentration in the melt is close to or close to the saturation concentration (hereinafter referred to as “substantially saturated concentration”), the crystal holder 1 with the single crystal substrate 7 attached to the tip is lowered, and the peak of the raised liquid raw material 4 Make contact. Since the top of the liquid raw material 4 is a low temperature part and the SiC concentration is supersaturated, SiC crystals are epitaxially grown on the single crystal substrate 7. Crystal growth is continued while pulling up the crystal holder 1 at a constant rate in accordance with the growth rate of SiC. After a crystal having a predetermined length is obtained, the crystal holder 1 is pulled up so that the substrate 7 is separated from the liquid raw material 4, and the substrate 7 to which the grown crystal is attached is recovered from the holder 1. The raw material can be replenished to the liquid raw material 4, and the process from the dissolution of carbon can be repeated again.

Next, an embodiment of the present invention capable of preventing the occurrence of crystal cracks at the initial stage and / or the final stage of the cooling crucible liquid phase epitaxial growth (CC-LPE) method will be described.
[First embodiment]
FIG. 3 is a longitudinal sectional view showing the first embodiment of the present invention, which is particularly effective in preventing the occurrence of crystal cracks at the initial growth stage in the CC-LPE method. In the figure, A, B, and C indicate the relationship among the crystal holder 1, the energizing coil 5, and the liquid raw material 4 before starting growth, immediately after starting growth, and during growth, respectively.

  The difference between the basic form shown in FIGS. 1 and 2 and the first embodiment lies in the presence or absence of the energizing coil lifting jig 14. In the first embodiment of the present invention, the energizing coil 5 can be moved up and down by installing the energizing coil raising / lowering jig 14 provided with an appropriate drive mechanism M such as a motor. Thereby, according to the crystal growth stage, the position of the energizing coil 5 can be moved to a portion requiring heating.

The outline of the production of the single crystal in the first embodiment of the present invention will be described next with respect to the production of the SiC single crystal.
Solid raw material containing silicon on the second crucible member 3 in the free space 10 in the crucible composed of the first crucible member 2 and the second crucible member 3 (for example, only silicon or silicon and Mn) About 1 kg. Cooling water is supplied to parts that require cooling, such as single crystal manufacturing equipment and high-frequency power supplies. After the pressure inside the chamber 11 is reduced to about 0.13 Pa, the gas 12 mainly composed of Ar gas is supplied into the chamber 11 and the supply is exhausted to maintain the pressure in the chamber 11 at about 0.11 MPa.

  An alternating current having a frequency of 10 kHz and an output of 100 kW is supplied to the energizing coil 5 using a high-frequency power source. In a few minutes, the solid raw material is heated to melt and becomes a melt. At that time, since the melt rises in a dome shape by the Lorentz force induced by the alternating current, the periphery thereof is held without contacting the inner wall of the first crucible member 2, and at the same time, the influence of electromagnetic stirring is exerted. Received and stirred. As shown in FIG. 3A, the position of the energizing coil 5 at this time is such that the top of the coil 5 is below the top of the raised melt and the bottom of the coil 5 is the same height as the second crucible member 3. It is a position to come to. Thereby, a temperature gradient in the vertical direction is formed in the melt so that the temperature at the top of the melt is lowered.

  When operated in this state, the carbon of the second crucible member is dissolved in the melt, and the melt becomes a SiC solution, that is, the raw material solution 4. Instead of supplying carbon by melting the second crucible member, carbon can also be contained in the solid raw material and dissolved in the melt. Also in this case, heating is performed for a sufficient time so that the supplied solid carbon is completely dissolved. In this case, the second crucible member 3 may be either one that does not dissolve carbon during heating or one that dissolves.

  If the operation is continued for about 5 hours under the above conditions, the SiC concentration of the raw material solution 4 reaches a substantially saturated concentration, so that crystal growth by the LPE method becomes possible. At this point, the single crystal substrate 7 is attached to the tip of the crystal holder 1 so that the (11-20) direction of the 6H-SiC single crystal is parallel to the moving direction of the crystal holder 1, and is inserted into the chamber. However, as shown in FIG. 3A, it stops at a position where it does not come into contact with the liquid raw material 4 raised in a dome shape. At this stage, since the crystal holder 1 and the single crystal substrate 7 are hardly subjected to induction heating as described above, they are only heated by the surrounding gas atmosphere.

  Subsequently, the energization coil raising / lowering jig 14 is operated so that the single crystal substrate 7 attached to the tip of the crystal holder 1 is effectively induction-heated by the energization coil 5 (for example, the height of the energization coil 5). The energizing coil 4 is raised to a position where the vicinity of the center is at the same height as the position of the single crystal substrate 7 (see FIG. 3B). As a result, the single crystal substrate 7 at the tip of the crystal holder 1 is intensively auxiliary heated to raise the temperature. After the temperature of this portion reaches a predetermined temperature (for example, substantially the same temperature as the apex of the liquid raw material 1), as shown in FIG. 3B, the liquid crystal 4 in which the single crystal substrate 7 at the tip of the crystal holder 1 is raised. The crystal holder 1 is lowered until it contacts the apex.

  After 5 minutes have passed since the single crystal substrate 7 contacts the liquid raw material 4, the energizing coil raising / lowering jig 14 is operated to lower the energizing coil 5 to the original position (see FIG. 3C). As a result, a temperature gradient in the vertical direction in which the apex becomes a low temperature again is formed in the liquid raw material 4, and the apex becomes supercooled (supersaturated concentration), and the apex of the liquid raw material 4 (contact surface with the substrate 7). The driving force for crystal growth at this point is generated.

  Thereafter, a SiC crystal is grown on the substrate 7 by continuously operating for 100 hours while pulling up the crystal holder 1 at an average speed of about 500 μm / h. At the initial stage of raising, the raising speed is appropriately increased or decreased. As a result, a silicon carbide single crystal (growth crystal 15 shown in FIG. 3C) having a length of about 50 mm and a diameter of about 50 mm was obtained. During this time, the liquid raw material 4 was always in contact with the second crucible member 3 and the gas 12, but was not in contact with the first crucible member 2.

  Prior to the start of crystal growth, the energizing coil 5 is raised to preheat the vicinity of the tip of the crystal holder 1 where the single crystal substrate 7 is located, that is, the crystal growth site, so that the liquid raw material 4 and the crystal growth site are heated. The temperature difference from As a result, a change in the amount of heat flux applied to the substrate 7 (ie, thermal shock) when the single crystal substrate 7 comes into contact with the liquid raw material 4 is reduced, and cracking of the substrate 7 is prevented. The prevention of cracking when stopping crystal growth using the same single crystal manufacturing apparatus will be described in the second embodiment below.

[Second Embodiment]
FIG. 4 is a longitudinal sectional view showing a second embodiment of the present invention effective for preventing the occurrence of crystal cracks at the end of growth in the CC-LPE method. In the figure, A, B, and C respectively indicate the positional relationship among the crystal holder 1, the energizing coil 5, and the liquid raw material 4 at the end of growth, immediately before the growth stop, and immediately after the growth stop. The single crystal manufacturing apparatus shown in FIG. 4 is the same as that shown in FIG.

The outline of the production of the single crystal in the second embodiment of the present invention will be described next with respect to the production of the SiC single crystal.
As described in the first embodiment, the crystal 15 is grown to a predetermined length. During this crystal growth, as shown in FIG. 4A, the position of the energizing coil 5 is such that a temperature gradient in the vertical direction is generated in the liquid material 4 so that the temperature at the top of the raised liquid material 4 is lowered (that is, In the lowered position).

  At the stage of stopping the crystal growth, first, the energization coil raising / lowering jig 14 is operated to raise the energization coil 5 to a position where the growth crystal 15 is effectively induction-heated by the energization coil 5 (see FIG. 4B). ). By this auxiliary heating, the temperature gradient of the liquid raw material 4 is reduced and the driving force for crystal growth is lost, so that crystal growth substantially stops. In this state, the operation is continued to raise the temperature of the growth crystal 15 and the vicinity of the tip of the crystal holder 1 (about 1500 ° C.) until a predetermined temperature (about 1800 ° C.) is reached. Thereafter, the crystal holder 1 is raised until the grown crystal 15 is detached from the apex of the liquid raw material 4 raised in a dome shape. Thereafter, the energizing coil raising / lowering jig 14 is operated to lower the energizing coil 5 and return it to the original position.

  When the silicon carbide single crystal obtained by applying the first and second embodiments was polished and observed with a microscope, the crystal was sound with no cracks observed. Also, polymorphic dislocations and polycrystals were not included.

[Third embodiment]
FIG. 5 is a longitudinal sectional view showing a third embodiment of the present invention effective for preventing the occurrence of crystal cracks at the initial growth stage in the CC-LPE method. In the figure, A, B, and C indicate the positional relationship between the crystal holder 1 and the liquid raw material 4 that are being grown before and immediately after the start of growth, respectively, and D is the power output time of the high-frequency power supplies G1 and G2. Showing change. The difference from the basic form shown in FIGS. 1 and 2 is that in the third embodiment of the present invention, a plurality of energizing coils 5 connected to independent high-frequency power supplies G1 and G2 are provided. is there. In other words, the energizing coil 5 is divided into two parts, a lower coil and an upper coil, and each can be supplied with an alternating current independently.

The outline of the production of the single crystal in the third embodiment of the present invention will be described next with respect to the production of the SiC single crystal.
About 1 kg of a solid material containing silicon is charged into the free space 10 in the crucible composed of the first crucible member 2 and the second crucible member 3. Cooling water is supplied to parts that require cooling, such as single crystal manufacturing equipment and high-frequency power supplies. After depressurizing the inside of the chamber 11 to about 0.13 Pa, the gas 12 mainly composed of Ar gas is supplied into the chamber 1 and the supply is exhausted to maintain the pressure in the chamber 11 at about 0.11 MPa.

  An alternating current having a frequency of 10 kHz and an output of 100 kW is supplied from the high frequency power supply G1 to the lower energizing coil 5. In a few minutes, the solid raw material is heated and melted into a melt. At that time, by the Lorentz force induced by the energization of alternating current to the energizing coil 5, the periphery of the melt is raised and held in a dome shape without contacting the side wall of the first crucible member 2, and electromagnetic stirring is performed. Stirred under the influence of

  When the operation is continued in this state, carbon is dissolved from the second crucible member in the melt, and the liquid raw material 4 in which SiC is dissolved is generated. Since the lower energization coil that is energized heats the lower side of the liquid raw material 4, a temperature gradient is formed in the liquid raw material 4 so that the upper portion has a lower temperature than the lower portion. The operation is continued for about 5 hours, and after the SiC concentration in the liquid raw material approaches the saturated concentration, the (11-20) direction of the 6H—SiC single crystal is parallel to the moving direction of the crystal holder 1. The single crystal substrate 7 is attached to the tip of the crystal holder 1 and inserted into the free space of the crucible until it does not come into contact with the liquid raw material 4 (see FIG. 5A).

  Subsequently, as shown in FIG. 5D, the operation of the high frequency power supply G2 is started, the current of the upper energizing coil is supplied, and the vicinity of the apex (that is, the crystal growth site) of the single crystal substrate 7 or the liquid raw material 4 is observed. Induction heating. After the temperature in the vicinity of the tip of the crystal holder 1 reaches a predetermined temperature as described in the first embodiment, the single crystal substrate 7 attached to the tip of the crystal holder 1 is raised in a dome shape. The crystal holder 1 is lowered until it contacts the apex of the raw material 4 (see FIG. 5B). Since the vicinity of the tip of the crystal holder 1 on which the substrate 7 is mounted is preheated, the thermal shock applied to the substrate 7 when in contact with the liquid raw material 4 is small, and cracking is prevented.

  After 5 minutes have passed since the single crystal substrate 7 contacts the liquid raw material 4, the operation of the high frequency power supply G2 is stopped as shown in FIG. 5D. As a result, the operation with only the high frequency power source G1 is performed again, that is, induction heating (only the lower side of the liquid raw material 4 is heated) using only the lower energizing coil, and a temperature gradient is formed in which the temperature of the raised vertex of the liquid raw material 4 is lowered. Then, a driving force for growing a crystal is generated on the substrate 7 in contact with the apex, and crystal growth occurs.

  Thereafter, a SiC crystal is grown on the substrate 7 by continuously operating for 100 hours while pulling up the crystal holder 1 at an average speed of about 500 μm / h. In the initial stage of raising, the raising speed is appropriately increased or decreased. As a result, a grown crystal 15 having a length of about 50 mm and a diameter of about 50 mm was obtained (see FIG. 5C). During this time, the liquid raw material 4 was always in contact with the second crucible member 3 and the gas 12, but was not in contact with the first crucible member 2.

  When the crystal completes growing to a predetermined length and stops the crystal growth, as shown in FIG. 5D, the operation of the high-frequency power source G2 is resumed to heat the vicinity of the crystal growth site. Thereby, the growth crystal 15 is heated. When the grown crystal 15 reaches a predetermined temperature, the crystal holder 1 is raised until the grown crystal 15 separates from the apex of the liquid raw material 4 raised in a dome shape. Thereafter, the operation of the high-frequency power supply G2 is stopped, and only the lower energizing coil is operated to keep the liquid raw material 4 in a molten state.

  When a single crystal of silicon carbide obtained by applying the third embodiment was polished and observed with a microscope, no cracks were observed in the crystal and it was sound. Also, polymorphic dislocations and polycrystals were not included.

  The first to third embodiments in which the auxiliary heating before and after the start of crystal growth and / or before and after the end by electromagnetic induction heating as a non-contact heating means is a single crystal in which no lattice mismatch occurs with the grown crystal 15 This is particularly suitable for homoepitaxial growth using the substrate 7.

  FIG. 6 is a longitudinal sectional view showing a fourth embodiment of the present invention effective for preventing the occurrence of crystal cracks at the initial stage of growth in the CC-LPE method. In the figure, A, B, and C indicate the positional relationship among the crystal holder 1, auxiliary heating / component adjustment jig 13, and liquid raw material 4 before the start of growth, immediately after the start of growth, and during the growth, respectively. D and E show two shape examples of the cross section along line aa in FIG. 6A, that is, the cross section of the auxiliary heating / component adjusting jig 13 surrounding the outer periphery of the crystal holder 1. The shape example shown in FIG. 6D is easier to handle than the shape example shown in FIG. 6E because the auxiliary heating / component adjustment jig 13 has a divided structure.

  The difference between the basic form shown in FIGS. 1 and 2 and the fourth embodiment is the presence or absence of the auxiliary heating / component adjustment jig 13. In the fourth embodiment of the present invention, a substantially tubular auxiliary heating / component adjusting jig 13 is arranged so as to surround the crystal holder 1 (see FIG. 6A). The auxiliary heating / component adjusting jig 13 can be moved up and down (moved up and down), and at the same time, the material contains an element constituting a part of the composition of the liquid raw material 4. When the auxiliary heating / component adjustment jig 13 is lowered and its tip is immersed in the liquid raw material 4 (see FIG. 6B), the tip of the auxiliary heating / component adjustment jig 13 is heated by heat transfer from the liquid raw material 4. Raise the temperature. At this time, the jig 13 comes into contact with the liquid source 4 that is outside the apex of the liquid source 4 that is raised, and thus the apex is higher than the apex in the low temperature gradient. As a result, the apex of the liquid raw material 4 surrounded by the auxiliary heating / component adjusting jig 13 and the vicinity of the tip of the crystal holder 1 near the single crystal substrate 7 are heated by the radiant heat from the jig 13 to raise the temperature. To do. At the same time, the tip of the auxiliary heating / component adjusting jig 13 can be dissolved in the liquid raw material 4 to adjust a part of the composition of the liquid raw material 4. The main composition of the auxiliary heating / component adjusting jig 13 is carbon.

The outline of the production of the single crystal in the fourth embodiment of the present invention will be described next with respect to the production of the aluminum nitride (AlN) single crystal.
About 1 kg of a solid raw material containing aluminum is charged into the free space 10 in the crucible composed of the first crucible member 2 and the second crucible member 3. Cooling water is supplied to parts that require cooling, such as single crystal manufacturing equipment and high-frequency power supplies. After reducing the pressure in the chamber 11 to about 0.13 Pa, the gas 12 mainly composed of nitrogen gas is supplied into the chamber 11 and the supply is exhausted to maintain the pressure in the chamber 11 at about 0.11 MPa.

  An AC current having a frequency of 5 kHz and an output of 120 kW is supplied to the energizing coil 5 using a high-frequency power source. In a few minutes, the solid raw material is heated to melt and become a melt. At that time, the melt is raised and held in a dome shape in a state where the periphery of the melt is not in contact with the side wall of the first crucible member 2 due to the Lorentz force, and is stirred under the influence of electromagnetic stirring.

  When the operation is continued in this state, carbon is dissolved from the second crucible member in the melt, and nitrogen is dissolved in the melt from the atmospheric gas, so that a liquid raw material 4 in which AlN is dissolved is generated. Since the energizing coil 5 is disposed below the top of the raised liquid material 4, a temperature gradient is formed in the liquid material 4 so that the upper part has a lower temperature than the lower part.

  The operation is continued for about 5 hours, and after the AlN concentration in the liquid raw material approaches the saturated concentration, the (11-20) direction of the 6H—SiC single crystal is parallel to the moving direction of the crystal holder 1. The single crystal substrate 7 is placed on the crystal holder 1 and inserted into the auxiliary heating / component adjustment jig 13 until it does not come into contact with the liquid raw material 4 (see FIG. 6A). Subsequently, the auxiliary heating / component adjustment jig 13 is lowered to a position where the tip is immersed in the liquid raw material 4 by about 10 mm. As a result, the tip of the auxiliary heating / component adjusting jig 13 is heated and heated, and the tip of the crystal holder 1 and the substrate 7 positioned inside the auxiliary heating / component adjusting jig 13 are near the top of the liquid raw material 4 (that is, near the crystal growth site). ) Temperature rises. At the same time, carbon is dissolved in the liquid raw material 4 from the jig 13. When the temperature in the vicinity of the crystal growth site (about 1400 ° C.) reaches a predetermined temperature (about 1900 ° C.), the single crystal substrate 7 attached to the tip of the crystal holder 1 rises to the apex of the liquid raw material 4 that rises like a dome. The crystal holder 1 is lowered until contact is made (see FIG. 6B). Since the vicinity of the substrate is heated in advance, the thermal shock applied to the substrate by the contact is small, and cracking of the substrate is prevented.

  After 5 minutes have passed since the single crystal substrate 7 contacts the liquid raw material 4, only the auxiliary heating / component adjustment jig 13 is raised and the jig 13 is detached from the liquid raw material 4. Since an appropriate amount of carbon is dissolved from the jig 13 in the liquid raw material 4 containing aluminum in the vicinity of the substrate 7 and the carbon concentration in this portion is increased, the 6H—SiC single crystal substrate 7 which is a heteroepitaxial substrate is an AlN solution. It does not dissolve in the liquid raw material 4.

  When the auxiliary heating / component adjusting jig 13 is pulled up and separated from the liquid raw material 4, the heating of the jig 13 by the liquid raw material 4 stops, and the crystal growth site (the tip of the crystal holder 1 in contact with the apex of the liquid raw material 4). The portion in the vicinity of the substrate 7) is exposed to free space. As a result, the temperature of this portion is lowered, and a temperature gradient in the vertical direction is formed in the liquid raw material 4 at a low temperature at the top thereof, as before the jig 13 is immersed in the liquid raw material 4. A driving force for AlN crystal growth occurs.

  Thereafter, the AlN crystal 15 is grown on the substrate 7 by performing continuous operation for 6 hours while pulling up the crystal holder 1 at an average speed of about 50 μm / h (see FIG. 6C). The pulling speed is appropriately increased or decreased at the initial stage of the pulling. As a result, an AlN single crystal heteroepitaxially grown at a growth thickness of about 300 μm on the 6H—SiC single crystal substrate 7 having a 15 mm square cross section was obtained.

  Although not shown in the figure, even when the crystal has been grown to a predetermined length and is in a stage where the crystal growth is stopped, the auxiliary heating / component adjustment jig 13 is used to generate cracks in the grown crystal 15. Can be prevented.

  For this purpose, first, the auxiliary heating / component adjusting jig 13 is lowered to a position where the tip of the auxiliary heating / component adjusting jig 13 is immersed in the liquid raw material 4 by about 10 mm. Thereby, the crystal holder 1 and the growth crystal 15 at the tip thereof are surrounded by the jig 13. The tip of the auxiliary heating / component adjusting jig 13 immersed in the liquid raw material 4 is heated by the heat transfer by the liquid raw material 4 to increase the temperature, and the vicinity of the growth site of the growth crystal 15 inside the liquid raw material 4 is heated. The temperature gradient disappears and crystal growth stops. Subsequently, the crystal holder 1 is raised until the grown crystal 15 separates from the top of the raised liquid material 4. Thereafter, the auxiliary heating / component adjustment jig 13 is raised, and the auxiliary heating / component adjustment jig 13 and the liquid raw material 4 are separated. Thus, even when the grown crystal is taken out, the thermal shock to the crystal can be suppressed and the occurrence of cracks can be prevented.

  When a single crystal of aluminum nitride obtained by applying the fourth embodiment was polished and observed under a microscope, the crystal was sound with no cracks observed. Also, polymorphic dislocations and polycrystals were not included.

[Fifth embodiment]
FIG. 7 is a longitudinal sectional view showing a fifth embodiment of the present invention effective for preventing the occurrence of crystal cracks at the initial stage of growth in the CC-LPE method. In the figure, A, B, and C respectively indicate the positional relationship among the crystal holder 1, the energizing coil 5, the auxiliary heating / component adjusting jig 13, and the liquid raw material 4 before growth start, immediately after growth start, and during growth. .

  The fifth embodiment is an embodiment in which the electromagnetic induction heating employed in the first and second embodiments described above and the auxiliary heating / component adjustment employed in the fourth embodiment are combined. The energizing coil raising / lowering jig 14 in the fifth embodiment of the present invention can move the energizing coil 5 up and down and arrange the coil 5 in a portion requiring heating. Instead of arranging this energization raising / lowering jig 14, the fifth embodiment is constituted by arranging two upper and lower energization coils connected to independent high-frequency power sources adopted in the third aspect described above. Is also possible.

  As described in the fourth embodiment, the auxiliary heating / component adjustment jig 13 surrounds the outer periphery of the crystal holder 1 and can be moved up and down. When immersed in the raw material 4, the tip of the auxiliary heating / component adjusting jig 13 is heated and heated, and the vicinity of the interface between the liquid raw material 4 and the single crystal substrate 7 surrounded by the auxiliary heating / component adjusting jig 13 is heated and raised. At the same time, the tip of the auxiliary heating / component adjusting jig 13 can be dissolved in the liquid raw material 4 to adjust a part of the composition of the liquid raw material 4.

The outline of the production of the single crystal in the fifth embodiment of the present invention will be described next for the production of the AlN single crystal.
First, as described in the fourth embodiment, the raw material is melted for about 5 hours, and C and N are dissolved in the melt to form the raw material solution 4 in which AlN has a substantially saturated concentration. To do. This raw material solution 4 is raised in a dome shape by the Lorentz force resulting from the application of an alternating current, and the energizing coil 5 is located below the raised vertex, so that a temperature gradient is generated at which the raised vertex becomes a low temperature.

  Thereafter, the single crystal substrate 7 is arranged on the crystal holder 1 so that the (11-20) direction of the 6H—SiC single crystal is parallel to the moving direction of the crystal holder 1 (see FIG. 7A). Subsequently, the energizing coil raising / lowering jig 14 is operated, and the position where the single crystal substrate 7 is effectively heated by the high frequency induction from the coil 5 (for example, as shown in FIG. The energizing coil 5 is raised to a position where the liquid raw material is at the same height as the raised apex of the liquid material. Before and after this, the auxiliary heating / component adjustment jig 13 is lowered to the extent that its tip is immersed in the liquid raw material 4 by about 10 mm as shown in FIG. 7B. As a result, the tip of the auxiliary heating / component adjusting jig 13 is heated to raise the temperature.

  In the present embodiment, the vicinity of the single crystal substrate 7 (that is, the vicinity of the crystal growth site) is heated by both the induction heating from the raised energization coil 5 and the radiant heat from the heated auxiliary heating / component adjustment jig 13. Therefore, the temperature rise to a predetermined temperature (from about 1400 ° C. to about 1900 ° C.) in this portion is achieved in a shorter time than the above-described embodiment. Further, as described in the fourth embodiment, a part of the tip portion of the auxiliary heating / component adjusting jig 13 immersed in the liquid raw material is dissolved in the liquid raw material 4, and the carbon of the liquid raw material 4 in the vicinity of the substrate 7. Concentration increases. When the temperature in the vicinity of the crystal growth site reaches a predetermined temperature, the crystal holder 1 is lowered until the single crystal substrate 7 attached to the tip of the crystal holder 1 comes into contact with the apex of the raised liquid raw material 4 (see FIG. 7B). .

  After 5 minutes have passed since the single crystal substrate 7 contacts the liquid raw material 4, the energizing coil raising / lowering jig 14 is operated to lower the energizing coil 5 to the original position, and the auxiliary heating / component adjusting jig 13 is installed. The auxiliary heating / component adjustment jig 13 is separated from the liquid raw material 4 by raising the temperature. At this time, since the appropriate amount of carbon was dissolved in the liquid raw material 4 containing aluminum, the 6H—SiC single crystal substrate 7 is not dissolved in the liquid raw material 4.

  Thereafter, while the crystal holder 1 is pulled up at an average speed of about 50 μm / h, continuous operation is performed for 100 hours to grow AlN crystals on the substrate. At the initial stage of raising, the raising speed is appropriately increased or decreased. As a result, an aluminum nitride crystal having a length of about 5 mm and a diameter of about 50 mm was obtained. When the obtained single crystal of aluminum nitride was polished and observed with a microscope, cracks were not observed in the crystal and it was sound. Also, polymorphic dislocations and polycrystals were not included.

  In the fourth and fifth embodiments in which the auxiliary heating before and after the start of crystal growth and / or before and after the end is performed by the auxiliary heating / component adjusting jig 13, the single crystal substrate 7 is a substance different from the grown crystal 15, Particularly suitable for heteroepitaxial growth in which lattice mismatch occurs with the single crystal to be manufactured (growth crystal 15), but in the case of homoepitaxial growth using the single crystal substrate 7 in which no lattice mismatch occurs with the growth crystal 15 It is also applicable to.

  As described above, the present invention uses the Lorentz force to raise the melt and promote induction heating, and the seed crystal is brought into contact with the vicinity of the apex of the raised melt to cause liquid phase epitaxial growth on the seed crystal. In the method for growing a bulk single crystal, the thermal shock of the crystal (seed crystal and / or growth crystal) at the initial stage and / or the end stage of growth can be reduced to prevent the growth crystal from cracking.

The longitudinal cross-sectional view which shows typically the single-crystal manufacturing apparatus used for the basic cooling crucible method liquid phase epitaxial growth (CC-LPE) method. The partially broken perspective view which shows the crucible structure example of FIG. The longitudinal cross-sectional view of the single crystal manufacturing apparatus which shows typically the mode of the crystal crack generation | occurrence | production prevention example of the single crystal growth initial stage by CC-LPE method of this invention. A: Before starting growth, B: Immediately after starting growth, C: Growing. The longitudinal cross-sectional view of the single crystal manufacturing apparatus which shows typically the mode of the crystal crack generation | occurrence | production prevention example of the single crystal growth end by the CC-LPE method of this invention. A: end of growth, B: immediately before growth stop, C: immediately after growth stop. Longitudinal cross-sectional view schematically showing an example of prevention of generation of crystal cracks in the initial stage of growth according to the present invention in cooling crucible liquid phase epitaxial growth (CC-LPE), A: before growth start, B: immediately after growth start, C: during growth, D: Time change of outputs of the two high-frequency power supplies G1 and G2. The figure which shows typically the crystal crack generation | occurrence | production prevention example 4 of the growth initial stage by this invention in cooling crucible method liquid phase epitaxial growth (CC-LPE), A: Before growth start, B: Immediately after growth start, C: During growth, D: One example of an aa cross section, E: Another example of an aa cross section. Longitudinal sectional views schematically showing a growth crack prevention example 5 in the early stage of growth according to the present invention in cooling crucible liquid phase epitaxial growth (CC-LPE), A: before growth start, B: immediately after growth start, C: during growth.

Explanation of symbols

1: Crystal holder, 2: First crucible member (substantially sidewall portion), 3: Second crucible member (substantially bottom portion), 4: Liquid raw material (melt), 5: Energizing coil (normal conducting coil) , 6: slit, 7: single crystal substrate (seed crystal), 8: segment, 9: opening, 10: free space, 11: chamber, 12: gas, 13: auxiliary heating / component adjustment jig, 14: energization Coil lifting jig, 15: growth crystal, G1, G2: high frequency power supply, M: drive mechanism

Claims (18)

A method for producing a single crystal, comprising bringing a seed crystal into contact with a melt in which a single crystal raw material heated in a crucible is dissolved and pulling the seed crystal from the melt,
The seed crystal is brought into contact with the apex of the raised melt while the Lorentz force induced by the application of alternating current to the normal conducting coil is applied to the melt to cause the rise and induction heating of the melt. Grow a single crystal on top,
Further, by auxiliary heating in the vicinity of the seed crystal in an unsteady process before and after the start of crystal growth and / or in the vicinity of the growth crystal in an unsteady process before and after the end of crystal growth, the seed crystal and / or Or prevent rapid changes in the heat flux of the growing crystal,
A method for producing a single crystal.   The method for producing a single crystal according to claim 1, wherein the auxiliary heating is performed by a heating means that is not in contact with the heated portion.   The auxiliary heating is performed by bringing a jig made of a part of the composition constituting the melt into contact with the melt, and at this time, a part of the jig in contact with the melt is dissolved in the melt. The single crystal manufacturing method according to claim 1, wherein the melt composition changes.   The auxiliary heating is also performed by bringing a jig made of a part of the composition constituting the melt into contact with the melt in addition to a heating means that is not in contact with the heated portion. The method for producing a single crystal according to claim 1, wherein a part of the jig in contact with the liquid is dissolved in the melt to change the melt composition.   The method for producing a single crystal according to claim 2 or 4, wherein the non-contact heating means is electromagnetic induction heating.   The single crystal manufacturing method according to claim 5, wherein the electromagnetic induction heating is performed by the normal conducting coil whose position is changed so as to heat the vicinity of the seed crystal and / or the grown crystal.   The single crystal production according to claim 5, wherein the electromagnetic induction heating is performed by a second normal conductive coil different from the normal conductive coil installed at a position where the vicinity of the seed crystal and / or the grown crystal is heated. Method.   The single crystal manufacturing method according to any one of claims 2 and 5 to 7, wherein a seed crystal that does not cause lattice mismatch with the single crystal to be manufactured is used.   The single crystal manufacturing method according to any one of claims 3 to 7, wherein a seed crystal in which lattice mismatch occurs with the single crystal to be manufactured is used.   A single crystal manufacturing apparatus comprising a crucible for holding a melt of a single crystal raw material and a crystal holder capable of moving up and down that can hold a seed crystal at the tip, and further generating Lorentz force in the melt A normal coil capable of inductively heating the melt at the same time as it rises, and means for auxiliary heating in the vicinity of the seed crystal and the grown crystal in the unsteady process before and after the start and end of crystal growth, respectively. An apparatus for producing a single crystal, comprising:   The single crystal manufacturing apparatus according to claim 10, wherein the means capable of performing auxiliary heating comprises means for performing non-contact heating on a heating portion.   The single crystal manufacturing apparatus according to claim 10, wherein the auxiliary heating means includes a jig made of a part of the composition constituting the melt.   11. The single crystal according to claim 10, wherein the means capable of performing auxiliary heating includes means for performing non-contact heating on a heating portion and a jig made of a part of the composition constituting the melt. Manufacturing equipment.   The single crystal manufacturing apparatus according to claim 12 or 13, wherein the non-contact heating means is electromagnetic induction heating.   The single crystal manufacturing apparatus according to claim 11 or 13, wherein the means for performing the non-contact heating includes the normal coil and an energizing coil lifting jig for moving the normal coil in a vertical direction.   The single crystal manufacturing apparatus according to claim 11 or 13, wherein the means for performing the non-contact heating is another normal coil disposed above the normal coil.   The crucible is composed of a first crucible member in contact with the melt and a second crucible member made of a conductive material surrounding a side peripheral surface of the melt, and the normal conduction is provided around the second crucible member. The coil according to claim 10, wherein the second crucible member has a plurality of slits in a direction substantially orthogonal to the winding direction of the normal coil, and further includes means for cooling the second crucible member. The single-crystal manufacturing apparatus in any one.   The single crystal manufacturing apparatus according to claim 17, wherein an upper surface of the first crucible member has a recess at a distance from the second crucible member.

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