CN116163004A - Device and method for growing silicon carbide crystal by liquid phase method - Google Patents
Device and method for growing silicon carbide crystal by liquid phase method Download PDFInfo
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- CN116163004A CN116163004A CN202211636437.5A CN202211636437A CN116163004A CN 116163004 A CN116163004 A CN 116163004A CN 202211636437 A CN202211636437 A CN 202211636437A CN 116163004 A CN116163004 A CN 116163004A
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/003—Heating or cooling of the melt or the crystallised material
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B11/00—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method
- C30B11/14—Single-crystal growth by normal freezing or freezing under temperature gradient, e.g. Bridgman-Stockbarger method characterised by the seed, e.g. its crystallographic orientation
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/36—Carbides
Abstract
The invention provides a device for growing silicon carbide crystals by a liquid phase method. When the device is used, the jacking is screwed into the seed crystal seat, and graphite paper can be clamped at the joint to serve as a buffer layer. Then, after the boss on the ring sleeve is clamped in the ring groove on the seed crystal ingot, the seed crystal ingot is connected with the seed crystal seat through the screw thread on the ring sleeve, so that the seed crystal ingot is in close contact with the jacking. The device can realize reliable clamping of the seed crystal ingot. The invention also provides a method for preparing silicon carbide crystals, which uses the device for growing silicon carbide crystals by a liquid phase method. The device can recycle seed crystals, omit the processes of sticking the seed crystals and fixing the seed crystals by subsequent hot pressing, and reduce the cost. The device can also eliminate growth defects caused by seed crystal adhesion, and can adjust the axial temperature field during crystal growth by changing the thickness of the jacking, thereby improving the quality of silicon carbide crystals grown by a liquid phase method. The silicon carbide crystal prepared by the method has excellent quality.
Description
Technical Field
The invention belongs to the technical field of liquid phase growth of silicon carbide single crystals. In particular, the invention relates to a device and a method for growing silicon carbide crystals by a liquid phase method.
Background
Silicon carbide (SiC) is one of widely-focused wide-bandgap semiconductor materials, has the advantages of low density, large forbidden bandwidth (the bandgap of 4H-SiC is 3.2eV at room temperature), high breakdown field strength (about 10 times of Si), high saturated electron mobility (about 2 times of Si), high thermal conductivity (about 3 times of Si, 10 times of GaAs), good chemical stability, and the like, and is an ideal substrate material for manufacturing high-frequency, high-voltage, high-power devices and blue light emitting diodes. Silicon carbide has important application potential in the fields of electric automobiles, rail transit, high-voltage power transmission and transformation, photovoltaics, 5G communication and the like.
The main growth method of SiC at present is a physical vapor transport method, but the problems of difficult control of growth stability, difficult diameter expansion, difficult p-type doping and the like exist. The liquid phase method has low growth temperature, relatively stable growth environment, close thermodynamic equilibrium condition in the growth process, good crystal quality, good prospect in the aspects of expanding diameter, p-type doping and the like, and is widely focused in academia and industry in recent years.
Seed crystal bonding and hot pressing are very important links in growing silicon carbide by a liquid phase method. The quality of the seed crystal adhesion directly affects the quality of the grown silicon carbide crystal. The prior art typically uses a squeegee to manually apply an organic glue to the seed crystal and graphite support surfaces, then bonding the two together (sometimes with a graphite paper between them as a buffer layer), and applying heat and pressure to cure the glue. At present, the mode has the following defects:
1. the uniformity of adhesion is not guaranteed. In the prior art, manual gluing is generally used, the thickness and uniformity of the adhesive layer cannot be guaranteed, and uneven adhesive layer can directly lead to uneven back heat dissipation of seed crystals, so that the crystal quality is affected.
2. Heating will introduce pores. In the carbonization process of the organic glue, low-boiling-point substances in the glue body volatilize, pores are even aggregated in the glue layer to form a large range of bubbles, and the temperature of a pore area in crystal growth is higher than that of a bonding area due to the difference of heat conductivity between the pores and the glue layer, so that seed crystals are sublimated back and escape along the pores, and finally, hexagonal cavity defects are formed.
3. The adhesion firmness is not guaranteed. Although organic glue (such as glucose, graphite glue, photoresist, AB glue, phenolic resin glue, epoxy resin glue and the like) is widely used as an adhesive in the vapor phase method for growing silicon carbide, the firmness of the adhesion can be ensured, but the up-and-down movement and high-speed rotation movement of the seed crystal in the liquid phase method are required to have higher adhesion strength, and the reliability of the adhesive mode cannot be ensured.
4. The melt can infiltrate into the bonding surface, creating defects caused by stress. After the seed crystal contacts the liquid level of the melt, if the wettability of the melt and the silicon carbide is better, the melt can climb upwards along the seed crystal and enter the bonding surface of the seed crystal and the graphite support, so that the bonding firmness and the heat conduction uniformity are affected. After cooling, these metals solidify at the bonding surface, introducing stress to the crystal and, in severe cases, causing cracking.
5. The cost is high. A single seed crystal is used for each crystal grown. The seed crystal is generally a commercially available silicon carbide wafer, and the seed crystal cost in the liquid phase method accounts for 40% -50% of the total cost of each furnace. In addition, the seed crystal portion is not available after growth is completed, and is generally cut off due to corrosion of the seed crystal by the melt vapor, inconsistent doping concentration of the seed crystal and growth portion, stress accumulation at the seed crystal, and the like. In addition, the two procedures of sticking the seed crystal and fixing the seed crystal by hot pressing increase the time and labor cost for growing the silicon carbide crystal by the liquid phase method.
Therefore, for the link of seed crystal preparation in the liquid phase method for growing silicon carbide, a device for simplifying the flow, reducing the cost and improving the quality of the liquid phase method for growing silicon carbide crystal is urgently needed.
Disclosure of Invention
The invention aims to provide a device for growing silicon carbide crystals by a liquid phase method. The device can recycle seed crystals, omit the processes of sticking the seed crystals and fixing the seed crystals by subsequent hot pressing, and reduce the cost. The device can also eliminate growth defects caused by seed crystal adhesion, and can adjust the axial temperature field during crystal growth by changing the thickness of the jacking, thereby improving the quality of silicon carbide crystals grown by a liquid phase method.
It is yet another object of the present invention to provide a method of preparing silicon carbide crystals. The silicon carbide crystal prepared by the method has excellent quality.
The above object of the present invention is achieved by the following means.
In one aspect, the present invention provides an apparatus for growing silicon carbide crystals by liquid phase method, comprising: seed rod, seed seat, jacking, seed ingot and ring sleeve;
the seed crystal base comprises a substrate, a first cylinder and a second cylinder, wherein the first cylinder extends along the circumferential direction of one side of the substrate, and the second cylinder extends along the circumferential direction of the other side of the substrate; the first cylinder is provided with internal threads; the second cylinder comprises a first section and a remaining second section close to the base plate, wherein the inner diameter of the second section is larger than that of the first section, and the first section and the second section are provided with internal threads;
one end of the ring sleeve is provided with a boss extending radially inwards, and the other end of the ring sleeve is provided with external threads;
the seed crystal ingot is provided with a circumferential groove;
the seed rod is connected to the first cylinder through threads;
the jacking is connected to the first section of the second cylinder by threads;
the seed crystal ingot is connected to the seed crystal seat through the annular sleeve, so that the jacking is clamped between the seed crystal seat and the seed crystal ingot; the boss on the ring sleeve is clamped into the groove on the seed crystal ingot, and the external thread of the ring sleeve is connected with the internal thread of the second section of the second cylinder in an adaptive manner.
Preferably, in the apparatus for growing silicon carbide crystals by liquid phase method of the present invention, the collar comprises at least two sub-collars, the external thread of each sub-collar being adapted to be connected to the internal thread of the second section of the second cylinder.
Preferably, in the apparatus for growing silicon carbide crystals by liquid phase method of the present invention, the apparatus further comprises a graphite paper, which is located between the jacking and the seed holder such that the jacking and the seed holder are spaced apart.
Preferably, in the apparatus for growing silicon carbide crystals by liquid phase method of the present invention, the apparatus further comprises a graphite paper, which is located between the jacking and the seed ingot such that the jacking and the seed ingot are spaced apart.
Preferably, in the device for growing silicon carbide crystals by a liquid phase method, the jacking is a solid cylinder, and the thickness is 2-50 mm. The thickness of the jacking is adjusted to realize the regulation and control of the axial temperature field of the crystal.
Preferably, in the apparatus for growing silicon carbide crystals by liquid phase method of the present invention, the seed ingot has a size of 2 to 8 inches and a thickness of 4 to 10mm. The ring groove on the seed crystal ingot is processed by adopting a diamond sintering grinding head, the width is 1-3 mm, and the depth is 1-3 mm.
Preferably, in the apparatus for growing silicon carbide crystals by liquid phase method of the present invention, the jacking, the ring cover and the seed crystal seat are made of high purity graphite or molybdenum.
Preferably, in the apparatus for growing silicon carbide crystals by liquid phase method of the present invention, the ring and the seed holder are provided with end surfaces so as to be screwed and unscrewed by using a tool.
In another aspect, the present invention provides a method for preparing a silicon carbide crystal using the apparatus for growing a silicon carbide crystal by a liquid phase method of the present invention, comprising the steps of:
(1) Placing the growth raw material into a crucible, and heating the crucible by an induction heating device to melt the growth raw material into a melt;
(2) Adjusting the position of the crucible in the induction coil to enable the liquid level of the melt to be in a high-temperature area, and then descending the seed crystal ingot to enable the seed crystal ingot to be in contact with the liquid level of the melt, so that the seed crystal ingot is reversely melted;
(3) Adjusting the position of the crucible in the induction coil to enable the bottom of the melt to be located in a high-temperature area so as to enable silicon carbide crystal growth to be carried out at the contact surface of the melt and the seed crystal ingot;
(4) After the growth is completed, the seed ingot is taken off, then the grown portion is cut off, and the cut surface of the seed ingot is flattened for reuse.
Preferably, in the method of the present invention, the seed ingot back-melting in the step (2) is performed by back-melting the seed ingot to a thickness of 1 to 100 μm.
Preferably, in the method of the present invention, the flattening of the cut surface of the seed ingot in the step (4) is performed by using a surface grinder, a thinning machine or a grinder.
Preferably, in the method of the present invention, the crucible is a graphite crucible; more preferably, the purity of the graphite crucible is not less than 99.95%, the inner diameter of the graphite crucible is 10-150mm larger than the diameter of the seed ingot, the wall thickness of the graphite crucible is not less than 10mm, and the density of the graphite crucible is 1.7-2.0g/cm 3 。
In the specific embodiment of the invention, external threads are arranged on the jacking and the ring sleeve, internal threads are arranged on the seed crystal seat, the seed crystal ingot is processed with a ring groove, and two semicircular rings are sleeved with bosses. When in use, the jacking is screwed into the seed crystal seat, and graphite paper is clamped at the joint to be used as a buffer layer. Then, after the bosses on the two semicircular ring sleeves are clamped in the ring grooves on the seed crystal ingot, the seed crystal ingot is connected with the seed crystal seat through the threads on the ring sleeves, so that the seed crystal ingot is in close contact with the jacking. A graphite paper can be clamped at the joint of the seed crystal ingot and the jacking as a buffer layer. The device can realize reliable clamping of the seed crystal ingot. The whole body can be connected to a seed rod for use.
In a specific embodiment of the present invention, the present invention provides a method for growing silicon carbide crystals by a liquid phase method, which is performed in the apparatus of the present invention, using an induction heating method, using a graphite crucible placed in a heating cylinder. The heating cylinder is made of graphite soft felt or graphite hard felt wrapped with graphite cylinder, and the purity of the graphite felt is not less than 99.9%. The growth feedstock of the present invention may comprise elemental metals of Si and Cr.
In a specific embodiment of the invention, the thickness of the back melt after the seed crystal contacts the liquid surface of the melt is 1-100 mu m, the holding time is 1-30 minutes, and the thickness of the back melt is larger than the surface roughness value after processing and the corrosion thickness of the melt steam to the seed crystal.
In a specific embodiment of the present invention, the seed ingot is removed after growth is completed, the seed ingot portion is cut off by a single wire cutter, or a multi-wire cutter is used, the growth portion is placed in the cutting area, the growth portion is directly cut into wafers, the seed ingot portion remains, and the cut surface of the seed ingot is ground flat by a flat grinder, a thinning machine or a grinder and then reused as a growth surface.
Compared with the prior art, the invention has at least the following beneficial effects:
(1) The invention provides a seed crystal fixing mode for growing silicon carbide crystals by a liquid phase method, and the mode can eliminate growth defects caused by seed crystal adhesion. Compared with the current seed crystal sticking mode, the device does not need glue and reliably clamps the seed crystal ingot by means of the clamp. In the device, the graphite paper is used as the buffer layer on the contact surface, even if the joint of the seed crystal and the jacking is still in a certain condition of uneven heat conduction, the thickness of the seed crystal is large, the influence can be weakened, and the temperature at the growth surface is still relatively uniform. Therefore, the problems of poor uniformity caused by adhesion, seed crystal back evaporation caused by air hole introduction, poor firmness and reliability and the like are avoided. In addition, since the thickness of the seed ingot is much greater than that of the seed piece, the melt does not substantially climb up to the junction, nor does it have the problem of metal-induced stress that solidifies at the interface.
(2) The invention provides a device capable of recycling seed crystals in the liquid phase method for growing silicon carbide crystals. The seed crystal ingot is used as the seed crystal and is combined with the back melting process, so that the seed crystal ingot can be repeatedly used after being cut and simply processed, the investment of the seed crystal in the growth process is greatly reduced, the processes of sticking the seed crystal and fixing the seed crystal by hot pressing are omitted, and the time and labor cost are reduced.
(3) The invention provides a device for adjusting the axial temperature field of a crystal in the growth of silicon carbide crystals by a liquid phase method. The device can adjust the back heat dissipation of the seed crystal by changing the thickness of the jacking, thereby adjusting the axial temperature field during the growth of the crystal. The axial temperature field determines the supersaturation degree during growth, and directly influences the growth speed and the crystallization morphology. Therefore, the quality of the silicon carbide crystal grown by the liquid phase method can be improved by constructing a reasonable axial temperature field. This object is achieved by the device according to the invention.
Drawings
Embodiments of the present invention are described in detail below with reference to the attached drawing figures, wherein:
FIG. 1 is a schematic illustration of an apparatus according to one embodiment of the present invention;
FIG. 2 is a schematic perspective view of an apparatus according to one embodiment of the present invention;
FIG. 3 is a schematic view of a portion of the structure of an apparatus according to one embodiment of the present invention;
FIG. 4 is a diagram showing the appearance of a silicon carbide crystal obtained in example 1 of the present invention;
FIG. 5 is a seed crystal holder according to comparative example 1 of the present invention obtained by fixing a seed crystal by means of adhesion;
FIG. 6 is a diagram showing the outline of a silicon carbide crystal produced in comparative example 1 of the present invention;
wherein, the reference numerals:
1-water cooling rod; 2-seed rods; 3-a heating cylinder; 4-a crucible; 5-raw materials; 6-an induction coil; 7-a crucible tray; 8-seed crystal base; 9-graphite paper; 10-jacking; 11-loop; 12-boss; 13-grooves; 14-seed ingot; 15-end face; 16-a first cylinder; 17-a second cylinder.
Detailed Description
The following detailed description of the invention is provided in connection with the accompanying drawings that are presented to illustrate the invention and not to limit the scope thereof.
Referring to fig. 1 to 4, the present invention provides an apparatus for growing silicon carbide crystals by a liquid phase method, comprising: a seed rod (2), a seed crystal seat (8), a jacking (10), a seed crystal ingot (14) and a ring sleeve (11); the seed crystal seat (8) comprises a substrate, a first cylinder (16) extending circumferentially along one side of the substrate, and a second cylinder (17) extending circumferentially along the other side of the substrate; the first cylinder (16) is provided with internal threads; the second cylinder (17) comprises a first section close to the base plate and a remaining second section, wherein the inner diameter of the second section is larger than that of the first section and the second section are provided with internal threads; one end of the ring sleeve (11) is provided with a boss (12) extending radially inwards, and the other end of the ring sleeve (11) is provided with external threads; the seed crystal ingot (14) is provided with a circumferential groove (13); the seed rod (2) is connected to the first cylinder (16) through threads; the jacking (10) is screwed to the first section of the second cylinder (17); the seed ingot (14) is connected to the seed holder (8) through the annular sleeve (11), so that the jacking (10) is clamped between the seed holder (8) and the seed ingot (14); wherein the boss (12) on the ring sleeve (11) is clamped into the groove (13) on the seed crystal ingot (14), and the external thread of the ring sleeve (11) is in fit connection with the internal thread of the second section of the second cylinder (17).
In one embodiment of the invention, the seed ingot (14) is 4 inch semi-insulating 4H-SiC, 25mm thick; the circumferential groove (13) on the seed crystal ingot (14) is processed by adopting a diamond sintering grinding head, the width is 2mm, and the depth is 2mm.
In a specific embodiment of the invention, the jacking (10), the ring sleeve (11), the seed crystal seat (8), the seed crystal rod (2) and the crucible (4) are made of high-purity graphite, and the purity is not less than 99.95%; the heating cylinder (3) is made of graphite soft felt, and the purity of the graphite felt is not less than 99.9%.
In a specific embodiment of the invention, the seed rod (2) has a diameter of 15mm, the graphite crucible (4) has an inner diameter of 150mm and a wall thickness of 15mm.
In a specific embodiment of the invention, the collar (11) comprises at least two sub-collars, the external thread of each sub-collar being adapted to be connected to the internal thread of the second section of the second cylinder (17).
In one embodiment of the invention, the device further comprises a graphite paper (9), the graphite paper (9) being located between the jacking (10) and the seed holder (8) such that the jacking (10) and the seed holder (8) are spaced apart.
In one embodiment of the invention, the apparatus further comprises a graphite paper (9), the graphite paper (9) being located between the jacking (10) and the seed ingot (14) such that the jacking (10) and the seed ingot (14) are spaced apart.
In one embodiment of the present invention, the jacking (10) is a solid cylinder with a thickness of 2-50 mm, which may be 15mm as shown in fig. 3 or 5mm as shown in fig. 4.
In a preferred embodiment of the invention, the seed ingot (14) is 2 to 8 inches in size and 4 to 10mm in thickness.
In the preferred embodiment of the invention, the jacking (10), the ring sleeve (11) and the seed crystal seat (8) are made of high-purity graphite or molybdenum.
In a preferred embodiment of the invention, end surfaces (15) are provided on the collar (11) and the seed holder (8) to facilitate screwing and unscrewing of the collar and the seed holder using a tool.
When the device is used, the jacking (10) is screwed into the seed crystal seat (8), and graphite paper (9) is clamped at the joint to be used as buffer. Then, after the bosses (12) on the two semicircular ring sleeves (11) are clamped on the circumferential grooves (13) on the seed crystal ingot (14), the bosses are connected with the seed crystal seat (8) through threads on the ring sleeves (11) and are tightly contacted with the jacking (10), and graphite paper (9) is clamped at the connecting position to serve as buffer. In this way, a reliable clamping of the seed ingot (14) is achieved, and the whole is connected to the seed rod (2) for use.
Example 1
The device of the invention is adopted, wherein: the jacking is screwed into the seed crystal seat, graphite paper is clamped at the joint to serve as buffer, after the bosses on the two semicircular annular sleeves clamp the annular grooves on the seed crystal ingot, the annular grooves are connected with the seed crystal seat through threads on the annular sleeves and are in tight contact with the jacking, and the graphite paper is clamped at the joint to serve as buffer, so that the seed crystal ingot can be reliably clamped, and the integral seed crystal ingot can be used after being integrally connected to the seed crystal rod. The jacking is a solid cylinder with the thickness of 15mm, as shown in figure 3. The seed ingot was 4 inch semi-insulating 4H-SiC (available from Peking Tianke Heda semiconductor Co., ltd.) 15mm thick; the circumferential groove on the seed crystal ingot is processed by adopting a diamond sintering grinding head, the width is 2mm, and the depth is 2mm. The jacking, the annular sleeve, the seed seat, the seed rod and the crucible are made of high-purity graphite, and the purity is not less than 99.95%; the heating cylinder is made of graphite soft felt, and the purity of the graphite felt is not less than 99.9%. The ring sleeve and the seed crystal seat are provided with end surfaces, and the ring sleeve and the seed crystal seat are screwed and unscrewed by using special tools. The diameter of the seed rod is 15mm, the inner diameter of the graphite crucible is 150mm, and the wall thickness is 15mm.
The liquid phase method for growing the silicon carbide crystal comprises the following steps:
(1) Placing a growth raw material containing Si and Cr metal simple substances into a crucible, heating the crucible by an induction heating device, and melting the growth raw material containing Si and Cr metal simple substances;
(2) Adjusting the position of the crucible in the induction coil, controlling the liquid level of the melt to be positioned in a high-temperature area heated by the coil, lowering the seed crystal to be in contact with the liquid level of the melt, and keeping the contact for 20 minutes to enable the seed crystal to be reversely melted by 50 mu m;
(3) Adjusting the position of the crucible in the induction coil, and controlling the bottom of the melt to be positioned in a high-temperature area heated by the coil for growth;
(4) And taking off the ingot after the growth is finished, cutting off a growth part by using a single-wire cutting machine, and grinding the cut surface of the seed ingot by using a surface grinder to be flat and then repeatedly using the flat surface as a growth surface.
A physical photograph of the silicon carbide crystal obtained in example 1 is shown in FIG. 4. The figure shows that the silicon carbide crystal obtained by growth has flat and smooth surface, no macroscopic defects such as grooves and cracks, and good crystal quality.
Comparative example 1
The apparatus for growing silicon carbide crystals by the liquid phase method used in this comparative example 1 did not include the structure shown in fig. 2, and a 4-inch semi-insulating 4H-SiC wafer (purchased from tokyo-gakuda semiconductor inc.) was fixed to a graphite seed crystal holder by means of organic bonding and hot pressing. As shown in fig. 5, many bubbles exist on the bonding surface. The whole body can be connected to a seed rod for use. The purity of the graphite seed crystal support is not less than 99.95 percent; the heating cylinder is made of graphite soft felt, and the purity of the graphite felt is not less than 99.9%. The diameter of the seed rod is 15mm, the inner diameter of the graphite crucible is 150mm, and the wall thickness is 15mm.
The liquid phase method for growing the silicon carbide crystal comprises the following steps:
(1) Placing a growth raw material containing Si and Cr metal simple substances into a crucible, heating the crucible by an induction heating device, and melting the growth raw material containing Si and Cr metal simple substances;
(2) Lowering the seed crystal support to contact with the liquid level of the melt for growth;
(3) And cutting off the growth part by using a single-wire cutting machine after the growth is finished to obtain the silicon carbide crystal.
A physical photograph of the silicon carbide crystal obtained by comparative example 1 is shown in FIG. 6. From the figure, it can be seen that the growth quality is significantly reduced at the bubble-containing site, the defects of grooves and wrappers are present, and the crystal quality is poor.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. An apparatus for growing silicon carbide crystals by a liquid phase process, comprising: seed rod, seed seat, jacking, seed ingot and ring sleeve;
the seed crystal base comprises a substrate, a first cylinder and a second cylinder, wherein the first cylinder extends along the circumferential direction of one side of the substrate, and the second cylinder extends along the circumferential direction of the other side of the substrate; the first cylinder is provided with internal threads; the second cylinder comprises a first section and a remaining second section close to the base plate, wherein the inner diameter of the second section is larger than that of the first section, and the first section and the second section are provided with internal threads;
one end of the ring sleeve is provided with a boss extending radially inwards, and the other end of the ring sleeve is provided with external threads;
the seed crystal ingot is provided with a circumferential groove;
the seed rod is connected to the first cylinder through threads;
the jacking is connected to the first section of the second cylinder by threads;
the seed crystal ingot is connected to the seed crystal seat through the annular sleeve, so that the jacking is clamped between the seed crystal seat and the seed crystal ingot; the boss on the ring sleeve is clamped into the groove on the seed crystal ingot, and the external thread of the ring sleeve is connected with the internal thread of the second section of the second cylinder in an adaptive manner.
2. The apparatus for liquid phase growth of silicon carbide crystals as claimed in claim 1, wherein the collar comprises at least two sub-collars, the external threads of each sub-collar being adapted to be connected to the internal threads of the second section of the second cylinder.
3. The apparatus for liquid phase growth of silicon carbide crystals as set forth in claim 1 wherein said apparatus further comprises a graphite paper positioned between said jacking and said seed holder such that said jacking and said seed holder are spaced apart.
4. The apparatus for liquid phase growth of silicon carbide crystals as set forth in claim 1 wherein said apparatus further comprises a graphite paper positioned between said jacking and said seed ingot such that said jacking and said seed ingot are spaced apart.
5. The apparatus for liquid phase growth of silicon carbide crystals as claimed in claim 1, wherein the jacking is a solid cylinder with a thickness of 2 to 50mm.
6. The apparatus for growing silicon carbide crystals by liquid phase method as claimed in claim 1, wherein the seed ingot has a size of 2 to 8 inches and a thickness of 4 to 10mm.
7. The apparatus for growing silicon carbide crystals by liquid phase method as claimed in claim 1, wherein the jacking, the ring cover and the seed crystal seat are made of high purity graphite or molybdenum.
8. An apparatus for growing silicon carbide crystals by liquid phase method according to claim 1, wherein the collar and the seed holder are provided with end surfaces for screwing and unscrewing the collar and the seed holder with a tool.
9. A method for producing a silicon carbide crystal using the apparatus for liquid-phase growth of a silicon carbide crystal according to any one of claims 1 to 8, comprising the steps of:
(1) Placing the growth raw material into a crucible, and heating the crucible by an induction heating device to melt the growth raw material into a melt;
(2) Adjusting the position of the crucible in the induction coil to enable the liquid level of the melt to be in a high-temperature area, and then descending the seed crystal ingot to enable the seed crystal ingot to be in contact with the liquid level of the melt, so that the seed crystal ingot is reversely melted;
(3) Adjusting the position of the crucible in the induction coil to enable the bottom of the melt to be located in a high-temperature area so as to enable silicon carbide crystal growth to be carried out at the contact surface of the melt and the seed crystal ingot;
(4) After the growth is completed, the seed ingot is taken off, then the grown portion is cut off, and the cut surface of the seed ingot is flattened for reuse.
10. The method of claim 9, wherein the back melting of the seed ingot in step (2) is performed by back melting the seed ingot to a thickness of 1 to 100 μm;
preferably, the flattening of the cut surface of the seed ingot in the step (4) is performed by using a surface grinder, a thinning machine or a grinder;
preferably, the crucible is a graphite crucible; more preferably, the purity of the graphite crucible is not less than 99.95%, the inner diameter of the graphite crucible is 10-150mm larger than the diameter of the seed ingot, the wall thickness of the graphite crucible is not less than 10mm, and the density of the graphite crucible is 1.7-2.0g/cm 3 。
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| CN117051471B (en) * | 2023-08-15 | 2024-03-22 | 通威微电子有限公司 | Device and method for growing silicon carbide crystal by liquid phase method |
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