阅读说明：本技术 一种液相法生长碳化硅晶体的装置及方法 (Device and method for growing silicon carbide crystals by liquid phase method ) 是由 张泽盛 于 2021-09-03 设计创作，主要内容包括：本发明涉及一种液相法生长碳化硅晶体的装置及方法。所述装置包括：用于容纳Si合金助溶液的坩埚和用于固定碳化硅籽晶的籽晶杆；所述装置还包括液面高度保持装置,液面高度保持装置包括液面保持圆环和用于推动液面保持圆环下降至Si合金助溶液中的推动装置。所述方法为：将包含有Si和金属单质的生长原料熔化成Si合金助溶液；使碳化硅籽晶下降并与助溶液相接触进行碳化硅晶体的生长；在碳化硅晶体的生长过程中,通过推动装置推动液面保持圆环下降至Si合金助溶液中以保持Si合金助溶液的液面高度不变。本发明可使得碳化硅晶体生长过程中液面高度不变且温场保持恒定,还可以保持助溶液成分的稳定以及提高生成的碳化硅晶体的厚度。(The invention relates to a device and a method for growing silicon carbide crystals by a liquid phase method. The device comprises: a crucible for containing a Si alloy solution and a seed rod for fixing a silicon carbide seed crystal; the device also comprises a liquid level height maintaining device, wherein the liquid level height maintaining device comprises a liquid level maintaining circular ring and a pushing device used for pushing the liquid level maintaining circular ring to descend into the Si alloy auxiliary solution. The method comprises the following steps: melting a growth raw material containing Si and a metal simple substance into an Si alloy auxiliary solution; lowering the silicon carbide seed crystal and contacting the silicon carbide seed crystal with the cosolvent to grow the silicon carbide crystal; and in the growth process of the silicon carbide crystal, the liquid level keeping ring is pushed by the pushing device to descend into the Si alloy auxiliary solution so as to keep the liquid level height of the Si alloy auxiliary solution unchanged. The invention can keep the liquid level constant and the temperature field constant in the growth process of the silicon carbide crystal, and can also keep the stability of the components of the assistant solution and improve the thickness of the generated silicon carbide crystal.)

1. An apparatus for growing silicon carbide crystals by a liquid phase method, comprising:

the device comprises: a crucible for containing a Si alloy solution and a seed rod for fixing a silicon carbide seed crystal; an insulating layer is arranged on the outer side of the crucible, and an induction heating device is arranged on the outer side of the insulating layer;

the device also comprises a liquid level height maintaining device, wherein the liquid level height maintaining device comprises a liquid level maintaining circular ring and a pushing device used for pushing the liquid level maintaining circular ring, and the pushing device is used for pushing the liquid level maintaining circular ring to descend into the Si alloy auxiliary solution contained in the crucible or ascend above the liquid level of the Si alloy auxiliary solution contained in the crucible.

2. The apparatus of claim 1, wherein:

the crucible is a graphite crucible;

the crucible wall thickness of the graphite crucible is not less than 10mm, the bottom thickness of the graphite crucible is not less than 15mm, and the density of the graphite crucible is 1.70-2.00 g/cm³And/or the purity of the graphite contained in the graphite crucible is not less than 99.95%.

3. The apparatus of claim 1, wherein:

the height of the liquid level maintaining ring is 10-30 mm; and/or

The liquid level maintaining ring is made of silicon carbide ceramic material or graphite material.

4. The apparatus of claim 1, wherein:

the diameter of the silicon carbide seed crystal is 10-50 mm smaller than the inner diameter of the crucible; and/or

The outer diameter of the liquid level maintaining circular ring is smaller than the inner diameter of the crucible, and the inner diameter of the liquid level maintaining circular ring is larger than the diameter of the silicon carbide crystal grown by the liquid phase method.

5. A method for growing silicon carbide crystals by a liquid phase method, which is carried out by using the apparatus for growing silicon carbide crystals by a liquid phase method according to any one of claims 1 to 4, comprising the steps of:

(1) placing growth raw materials containing Si and metal simple substances in the crucible, and heating the crucible through the induction heating device to melt the growth raw materials containing Si and metal simple substances into Si alloy auxiliary solution;

(2) descending the silicon carbide seed crystal fixed on the seed crystal rod and contacting the silicon carbide seed crystal with the Si alloy cosolvent to grow the silicon carbide crystal to obtain the silicon carbide crystal;

and in the growth process of the silicon carbide crystal, the liquid level maintaining ring is pushed by the pushing device to descend into the Si alloy auxiliary solution so as to maintain the liquid level of the Si alloy auxiliary solution unchanged.

6. The method of claim 5, wherein:

in the growth process of the silicon carbide crystal, the silicon carbide seed crystal is lifted at the speed of 10-500 mu m/h through a seed crystal rod; and/or

And in the growth process of the silicon carbide crystal, the liquid level maintaining ring is lowered at a speed of 100-700 mu m/h by a pushing device.

7. The method of claim 5, wherein:

and in the growth process of the silicon carbide crystal, increasing the heating power of the induction heating device by 100-500W.

8. The method of claim 5, wherein:

the Si alloy solution is Si_aX_bOr a mixture thereof, wherein X is one or more of Al, Ti, Cr, Y, Yb, Pr, Sn, La and Ce, a is more than or equal to 0.30 and less than or equal to 0.60, b is more than or equal to 0.40 and less than or equal to 0.70, and a + b is 1; and/or

The liquid level height of the Si alloy auxiliary solution is 20-50 mm.

9. The method of claim 5, wherein:

the initial position of the lower end of the liquid level maintaining circular ring is 1-3 mm lower than the liquid level of the Si alloy auxiliary solution.

10. A silicon carbide crystal obtained by the method of any one of claims 5 to 9.

Technical Field

The invention belongs to the technical field of liquid phase production of silicon carbide single crystals, and particularly relates to a device and a method for growing silicon carbide crystals by a liquid phase method.

Background

Silicon carbide is one of wide band gap semiconductor materials which are widely concerned, has the advantages of low density, large forbidden bandwidth, high breakdown field strength, high saturated electron mobility, good thermal stability and chemical stability and the like, and is an ideal substrate material for manufacturing high-frequency, high-voltage and high-power devices and blue light emitting diodes.

The main growth method of silicon carbide at present is a physical vapor transport method, although the method is mature and a large number of silicon carbide single crystal substrates are already supplied to the market, due to the poor stability of the gas growth environment in the vapor growth process, the grown crystals have defects such as micropipes and small particle wrapping, and meanwhile, the vapor growth method has the problems of difficult realization in the aspects of expanding diameter, doping p-type crystals and the like, and the further development of the whole industry of silicon carbide is limited. With the continuous deepening of the research of the liquid phase method, the advantages of the liquid phase method are continuously embodied, the growth temperature required by the growth of the liquid phase method is low, the growth environment is relatively stable, the growth process is close to the thermodynamic equilibrium condition, and the method has good prospects in the aspects of p-type crystals, expanding and the like.

In the liquid phase growth process of the single crystal silicon carbide, the temperature difference is required to be formed between the seed crystal at the top and the bottom of the crucible, so that the temperature of the bottom of the crucible is higher, and the solute is dissolved; the temperature of the seed crystal is lower, and the crystal is separated out. The growth process is always accompanied by the dissolution of the crucible wall by the cosolvent and the consumption of silicon and carbon in the cosolvent, and the processes directly result in the change of the components of the cosolvent and the change of the total amount of the cosolvent. Further leads to the problems of reduction of the proportion of silicon in the solution, reduction of the distance between a growth end (solid-liquid interface) and a raw material end (the bottom of a graphite crucible), reduction of temperature gradient and the like, and reduces the quality of the grown crystal and the sustainable proceeding of crystal growth. At present, a larger crucible can be adopted only by regulation and control, and more auxiliary solution is filled to counteract the influence on the components of the auxiliary solution and a temperature field in the growth process, but the crystal growth cost is increased. Meanwhile, after the crystal growth is carried out for a period of time, the growth needs to be stopped to ensure the growth quality of the crystal, and the thickness of the growing ingot is generally very low.

Disclosure of Invention

The invention provides a device and a method for growing silicon carbide crystals by a liquid phase method, which aim to solve one or more technical problems in the prior art. The device and the method can keep the distance between the liquid level of the growing crystal and the bottom of the crucible in the growth process of the liquid-phase silicon carbide crystal constant, and can keep the temperature field constant in the whole growth process of the liquid-phase silicon carbide crystal; in addition, the device and the method can also keep the stability of the components of the cosolvent in the growth process of the silicon carbide crystal by the liquid phase method and improve the thickness of the generated silicon carbide crystal.

In order to achieve the above object, the present invention provides in a first aspect an apparatus for growing a silicon carbide crystal by a liquid phase method, the apparatus comprising: a crucible for containing a Si alloy solution and a seed rod for fixing a silicon carbide seed crystal; an insulating layer is arranged on the outer side of the crucible, and an induction heating device is arranged on the outer side of the insulating layer; the device also comprises a liquid level height maintaining device, wherein the liquid level height maintaining device comprises a liquid level maintaining circular ring and a pushing device used for pushing the liquid level maintaining circular ring, and the pushing device is used for pushing the liquid level maintaining circular ring to descend into the Si alloy auxiliary solution contained in the crucible or ascend above the liquid level of the Si alloy auxiliary solution contained in the crucible.

Preferably, the crucible is a graphite crucible; the crucible wall thickness of the graphite crucible is not less than 10mm, the bottom thickness of the graphite crucible is not less than 15mm, and the density of the graphite crucible is 1.70-2.0 g/cm³And/or the purity of the graphite contained in the graphite crucible is not less than 99.95%.

Preferably, the height of the liquid level maintaining ring is 10-30 mm; and/or the liquid level holding ring is made of a silicon carbide ceramic material or a graphite material.

Preferably, the diameter of the silicon carbide seed crystal is 10-50 mm smaller than the inner diameter of the crucible; and/or the outer diameter of the liquid level maintaining circular ring is smaller than the inner diameter of the crucible, and the inner diameter of the liquid level maintaining circular ring is larger than the diameter of the silicon carbide crystal grown by the liquid phase method.

The present invention provides, in a second aspect, a method for growing a silicon carbide crystal by a liquid phase method, which is carried out in the apparatus for growing a silicon carbide crystal by a liquid phase method according to the first aspect, comprising the steps of:

(1) placing growth raw materials containing Si and metal simple substances in the crucible, and heating the crucible through the induction heating device to melt the growth raw materials containing Si and metal simple substances into Si alloy auxiliary solution;

(2) descending the silicon carbide seed crystal fixed on the seed crystal rod and contacting the silicon carbide seed crystal with the Si alloy cosolvent to grow the silicon carbide crystal to obtain the silicon carbide crystal;

and in the growth process of the silicon carbide crystal, the liquid level maintaining ring is pushed by the pushing device to descend into the Si alloy auxiliary solution so as to maintain the liquid level of the Si alloy auxiliary solution unchanged.

Preferably, in the growth process of the silicon carbide crystal, the silicon carbide seed crystal is lifted at a speed of 10-500 mu m/h through a seed crystal rod; and/or in the growth process of the silicon carbide crystal, the liquid level maintaining ring is lowered at a speed of 100-700 mu m/h by a pushing device.

Preferably, the heating power of the induction heating device is increased by 100-500W in the growth process of the silicon carbide crystal.

Preferably, the Si alloy solution aid is Si_aX_bOr a mixture thereof, wherein X is one or more of Al, Ti, Cr, Y, Yb, Pr, Sn, La and Ce, a is more than or equal to 0.30 and less than or equal to 0.60, b is more than or equal to 0.40 and less than or equal to 0.70, and a + b is 1; and/or the liquid level height of the Si alloy auxiliary solution is 20-50 mm.

Preferably, the initial position of the lower end of the liquid surface maintaining ring is 1-3 mm lower than the liquid surface of the Si alloy auxiliary solution.

The invention provides in a third aspect a silicon carbide crystal obtained by the method of the invention in the second aspect.

Compared with the prior art, the invention at least has the following beneficial effects:

(1) the invention provides a device and a method capable of keeping the liquid level height of a Si alloy auxiliary solution unchanged in the process of growing a silicon carbide single crystal by a liquid phase method. According to the device and the method for growing the silicon carbide crystal by the liquid phase method, the height of the liquid level of the Si alloy solution is kept unchanged in the growing process, so that the temperature field in the whole growing process is kept constant, namely, the constant temperature field growth of the silicon carbide crystal is ensured, the growing time is prolonged, a thicker crystal ingot can be obtained by one-time growth, and the yield is effectively improved on the premise of not increasing the cost; meanwhile, the growth condition is stable, so that the long-time stable growth of the silicon carbide crystal is facilitated, and the quality of the grown crystal is improved; in addition, because the temperature field changes due to the change of parameters such as the heat preservation condition, the liquid level height and the like in the growth process, in some preferred embodiments of the invention, the heating power of the induction heating device can be properly adjusted to offset the variables, so that the stability of the temperature field can be further improved, and the long-time stable growth of the silicon carbide crystal can be realized.

(2) In some preferred embodiments of the present invention, the level-maintaining ring is made of a silicon carbide ceramic material or a graphite material, which is supplemented with a growth raw material (carbon or silicon carbide) during the growth of a silicon carbide crystal; unlike the secondary feeding or the sudden feeding, the liquid level maintaining ring in the invention is slowly and stably pushed into the Si alloy auxiliary solution by a pushing device, the liquid level maintaining ring capable of supplementing the growth raw materials is added milder, and has no sudden interference on the growth conditions, thereby ensuring the stability of the growth conditions, and simultaneously ensuring that the transformation of the components of the Si alloy auxiliary solution can be continuously controlled according to the pushing speed of the liquid level maintaining ring.

(3) The device and the method can keep the liquid level height of the Si alloy solution in the growth process of the silicon carbide by the liquid phase method constant, and can keep the temperature field constant in the growth process of the silicon carbide crystal by the whole liquid phase method; in addition, the device and the method can also keep the stability of the components of the cosolvent in the growth process of the silicon carbide crystal by the liquid phase method and improve the thickness of the generated silicon carbide crystal.

Drawings

FIG. 1 is a schematic diagram of an apparatus for growing silicon carbide crystals by the liquid phase method according to some embodiments of the invention.

FIG. 2 is a schematic view of silicon carbide crystals obtained in examples 1 to 3 of the present invention and comparative example 1.

In the figure: FIG. (a) is a view showing the external appearance of a silicon carbide crystal obtained in example 1; FIG. b is a schematic representation of the silicon carbide crystal obtained in example 2; FIG. c is a schematic view showing the outer appearance of the silicon carbide crystal obtained in example 3; FIG. d is a view showing the external appearance of the silicon carbide crystal obtained in comparative example 1.

FIG. 3 is a graph showing the change in diameter of a silicon carbide crystal during growth in example 1 of the present invention.

FIG. 4 is a graph showing the change in diameter of a silicon carbide crystal during growth in example 2 of the present invention.

FIG. 5 is a graph showing the change in diameter of a silicon carbide crystal during growth in example 3 of the present invention.

FIG. 6 is a graph showing the change in diameter of a silicon carbide crystal in comparative example 1 of the present invention during growth.

In fig. 1: 1: a liquid level height maintaining means; 11: a pushing device; 12: a liquid level maintaining ring; 2: an induction coil; 3: a seed rod; 4: silicon carbide seed crystals; 5: a crucible; 6: a Si alloy aid solution; 7: a heat-insulating layer; 8: a crucible support.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.

The present invention provides in a first aspect an apparatus for growing a silicon carbide crystal by a liquid phase method, for example, as shown in FIG. 1, the apparatus comprising: a crucible 5 for containing a Si alloy solution 6 and a seed rod 3 for fixing a silicon carbide seed crystal 4; an insulating layer 7 is arranged on the outer side of the crucible 5, and an induction heating device (only an induction coil 2 is shown in the figure) is arranged on the outer side of the insulating layer 7; in the invention, the heat-insulating layer 7 is made of heat-insulating materials, the seed rod 3 is driven by a driving source to control the lifting and the rotation of the silicon carbide seed crystal 4, the upper end of the seed rod 3 is positioned outside the crucible, and the lower end of the seed rod 3 is positioned inside the crucible; the induction heating device comprises an induction coil 2, the induction coil 2 and the seed rod 3 are coaxially arranged, the induction heating device inductively heats the crucible through electromagnetic induction, and the growth raw materials contained in the crucible are melted into a Si alloy auxiliary solution; in the growth process of growing the silicon carbide crystal by the liquid phase method, the induction heating device can enable the Si alloy cosolvent to be maintained at the growth temperature of the silicon carbide crystal; in the invention, in the process of growing silicon carbide crystals by a liquid phase method, a silicon carbide seed crystal 4 is fixed at the lower end of a seed crystal rod 3, and a Si alloy auxiliary solution 6 is contained in a crucible; the device also comprises a liquid level height maintaining device 1, wherein the liquid level height maintaining device 1 comprises a liquid level maintaining ring 12 and a pushing device 11 for pushing the liquid level maintaining ring 12, the pushing device 11 is used for pushing the liquid level maintaining ring 12 to ascend and descend along the height direction of the Si alloy auxiliary solution, namely in the invention, the pushing device 11 is used for pushing the liquid level maintaining ring 12 to descend into the Si alloy auxiliary solution contained in the crucible or ascend above the liquid level of the Si alloy auxiliary solution contained in the crucible; in the present invention, the pushing device 11 may include, for example, a pushing rod and a pushing source, the pushing source pushes the liquid level holding ring 12 to move up and down through the pushing rod, the upper end of the pushing rod is located outside the crucible and connected to the pushing source, the lower end of the pushing rod is located inside the crucible and connected to the liquid level holding ring 12, and the pushing source may be, for example, a servo motor; in the present invention, the apparatus may further include, for example, a rotating device for rotating the crucible; it is specifically stated that the terms "upper", "lower", "bottom", "inner", "outer", "height direction", etc., indicate orientations or positional relationships based on those shown in fig. 1, and are only for convenience in describing the present invention and simplifying the description.

According to the device, in the growth process of growing the silicon carbide crystal by the liquid phase method, the liquid level of the Si alloy solution is kept constant by pushing the liquid level keeping ring into the liquid level of the Si alloy solution, namely, the distance between the liquid level of the Si alloy solution and the bottom of the crucible is kept constant, so that the temperature field in the whole growth process is kept constant, the growth time is prolonged, a thicker crystal ingot can be obtained by one-time growth, and the yield is effectively improved on the premise of not increasing the cost; meanwhile, the growth condition is stable, so that the long-time stable growth of the silicon carbide crystal is facilitated, and the quality of the grown crystal is improved; the device can keep the liquid level height of the Si alloy solution in the growth process of the silicon carbide by the liquid phase method constant, and can keep the temperature field constant in the growth process of the silicon carbide crystal by the whole liquid phase method; in addition, the device and the method can also keep the stability of the components of the cosolvent in the growth process of the silicon carbide crystal by the liquid phase method and improve the thickness of the generated silicon carbide crystal.

According to some preferred embodiments, the bottom of the insulating layer 7 is further provided with a susceptor 8, for example, as shown in fig. 1.

According to some preferred embodiments, the crucible 5 is a graphite crucible; the crucible wall thickness of the graphite crucible is not less than 10mm, the bottom thickness of the graphite crucible is not less than 15mm, and the density of the graphite crucible is 1.70-2.0 g/cm³And/or the purity of the graphite contained in the graphite crucible is not less than 99.95%, namely, the purity of the graphite material adopted by the graphite crucible is not less than 99.95%.

According to some preferred embodiments, the height of the level maintaining ring is 10 to 30mm (e.g. 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30 mm); and/or the liquid level holding ring is made of a silicon carbide ceramic material or a graphite material; in the present invention, it is preferable that the liquid level holding ring is made of a silicon carbide ceramic material or a graphite material, which is supplemented with a growth raw material (carbon or silicon carbide) during the growth of the silicon carbide crystal; unlike the secondary feeding or the sudden feeding, the liquid level maintaining ring in the invention is slowly and stably pushed into the Si alloy auxiliary solution by a pushing device, the liquid level maintaining ring capable of supplementing the growth raw materials is added milder, and has no sudden interference on the growth conditions, thereby ensuring the stability of the growth conditions, and simultaneously ensuring that the transformation of the components of the Si alloy auxiliary solution can be continuously controlled according to the pushing speed of the liquid level maintaining ring.

According to some preferred embodiments, the diameter of the silicon carbide seed crystal is 10 to 50mm (e.g., 10, 15, 20, 25, 30, 35, 40, 45, or 50mm) less than the inner diameter of the crucible; and/or the outer diameter of the liquid level maintaining circular ring is smaller than the inner diameter of the crucible, and the inner diameter of the liquid level maintaining circular ring is larger than the diameter of the silicon carbide crystal grown by the liquid phase method.

The present invention provides, in a second aspect, a method for growing a silicon carbide crystal by a liquid phase method, the method being carried out using the apparatus for growing a silicon carbide crystal by a liquid phase method according to the first aspect of the present invention, the method comprising the steps of:

(1) placing growth raw materials containing Si and metal simple substances in the crucible, and heating the crucible through the induction heating device to melt the growth raw materials containing Si and metal simple substances into Si alloy auxiliary solution;

(2) descending the silicon carbide seed crystal fixed on the seed crystal rod and contacting the silicon carbide seed crystal with the Si alloy cosolvent to grow the silicon carbide crystal, and finally obtaining the silicon carbide crystal; in the growth process of the silicon carbide crystal, the liquid level maintaining ring is pushed to descend into the Si alloy auxiliary solution by the pushing device so as to maintain the liquid level height of the Si alloy auxiliary solution unchanged; specifically, the growth raw material containing Si and metal simple substances is filled into a device for growing silicon carbide by a liquid phase method as shown in figure 1, air in a growth furnace is pumped out and then inert gas is filled for protection, the growth raw material is heated to be molten to form a Si alloy auxiliary solution, and after the conditions are relatively stable, a silicon carbide seed crystal is lowered to be in contact with the Si alloy auxiliary solution and crystal growth is carried out; the method adopts an induction heating method to heat the crucible, controls the liquid level height of the Si alloy solution and the temperature field to be unchanged by controlling the position of the liquid level maintaining ring in the growth process, and realizes the long-time stable growth of the crystal; in some preferred embodiments, the heating power is preferably changed by properly adjusting the current in the induction coil during the growth process to further ensure that the temperature field is not changed, which is more favorable for realizing the long-time stable growth of the crystal; in the invention, when the silicon carbide seed crystal is contacted with the liquid level of the Si alloy auxiliary solution, the bottom (lower end) of the liquid level retaining ring is horizontal to the liquid level of the Si alloy auxiliary solution, and after the silicon carbide seed crystal is contacted with the liquid level of the Si alloy auxiliary solution, the liquid level retaining ring can be pushed downwards into the Si alloy auxiliary solution by a pushing device according to the descending speed of the liquid level of the Si alloy auxiliary solution in the growth process, so that the liquid level height of the Si alloy auxiliary solution in the growth process is ensured to be unchanged; after the growth process is finished, the grown silicon carbide crystal is pulled out from the Si alloy solution aid and slowly cooled, namely the whole growth process of the liquid phase method silicon carbide single crystal is finished.

In the method, the liquid level maintaining ring is pushed into the liquid level of the Si alloy solution during the growth process of growing the silicon carbide crystal by the liquid phase method, so that the height of the liquid level of the Si alloy solution is kept unchanged, namely, the distance between the liquid level of the Si alloy solution and the bottom of the crucible is kept constant, and the temperature field in the whole growth process is kept constant, so that the growth time is prolonged, a thicker crystal ingot can be obtained by one-time growth, and the yield is effectively improved on the premise of not increasing the cost; meanwhile, the growth condition is stable, so that the long-time stable growth of the silicon carbide crystal is facilitated, and the quality of the grown crystal is improved; the method can keep the liquid level height of the Si alloy solution in the growth process of the silicon carbide by the liquid phase method constant, and can keep the temperature field constant in the growth process of the silicon carbide crystal by the whole liquid phase method; in addition, the device and the method can also provide solute for growth by melting the liquid surface maintaining ring into the Si alloy auxiliary solution, maintain the stability of the auxiliary solution components in the growth process of the silicon carbide crystal by the liquid phase method and improve the thickness of the generated silicon carbide crystal.

The invention mainly protects a method for keeping the height of a liquid level unchanged in the process of growing silicon carbide single crystals by a liquid phase method, which is realized by pressing a liquid level keeping ring prepared from a silicon carbide ceramic material or a graphite material into a Si alloy cosolvent in the growing process, and meanwhile, the pressed liquid level keeping ring can also provide raw materials for growth; the method ensures the solution of the Si alloy solutionThe surface height keeps the temperature field stable in the growth process, and the growth quality and the growth thickness are improved. The stable growth of the silicon carbide single crystal in the present invention is particularly useful for the liquid phase method of growing a silicon carbide single crystal, which involves the dissolution and recrystallization of solute material, and therefore requires the level of the Si alloy solution to be kept constant, such as silicon, YVO₄And the method has no obvious effect in a simple crystallization process.

In the invention, the liquid level maintaining ring is pushed downwards into the Si alloy auxiliary solution by a pushing device according to the descending speed of the liquid level of the Si alloy auxiliary solution in the growth process, so that the height of the liquid level of the Si alloy auxiliary solution in the growth process is ensured to be unchanged; in some preferred embodiments of the invention, the silicon carbide seed crystal is lifted by a seed rod at a speed of 10-500 μm/h (e.g., 10, 30, 50, 80, 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, or 500 μm/h) during the growth of the silicon carbide crystal; and/or in the growth process of the silicon carbide crystal, the liquid level maintaining ring is lowered at a speed of 100-700 mu m/h (such as 100, 120, 150, 180, 200, 220, 250, 280, 300, 320, 350, 380, 400, 420, 450, 480, 500, 520, 550, 580, 600, 620, 650, 680 or 700 mu m/h) by a pushing device.

According to some more preferred embodiments, during the growth of the silicon carbide crystal, the silicon carbide seed crystal is preferably lifted by a seed rod at a speed of 10-500 μm/h, while the liquid level holding ring is preferably lowered by a pushing device at a speed of 100-700 μm/h; in some further preferred embodiments, during the growth of the silicon carbide crystal, the silicon carbide seed crystal is lifted by a seed rod at a speed of 10-500 μm/h, and the liquid level holding ring is lowered by a pushing device at a speed of 100-700 μm/h, and the speed of lowering of the liquid level holding ring is less than the speed of lifting of the silicon carbide seed crystal.

According to some preferred embodiments, the heating power of the induction heating device is increased by 100-500W (for example, 100, 150, 200, 250, 300, 350, 400, 450 or 500W) during the growth process of the silicon carbide crystal; in the growth process of the silicon carbide crystal, as the heat preservation condition gradually becomes worse, the heating power is preferably properly controlled in the growth process, so that the heating power is increased by 100-500W, the temperature field can be further kept unchanged, and the long-time stable growth of the silicon carbide crystal is more favorably realized.

According to some preferred embodiments, the Si alloy co-solution is Si_aX_bOr a mixture thereof, wherein the metal element X is one or more of Al, Ti, Cr, Y, Yb, Pr, Sn, La and Ce, a is more than or equal to 0.30 and less than or equal to 0.60, b is more than or equal to 0.40 and less than or equal to 0.70, and a + b is 1; and/or the liquid level height of the Si alloy auxiliary solution is 20-50 mm (for example, 20, 25, 30, 35, 40, 45 or 50 mm).

In some specific embodiments, the liquid level maintains the lower end of the annular ring in horizontal contact with the liquid level of the Si alloy co-solution before the silicon carbide seed crystal is not in contact with the liquid level of the Si alloy co-solution, i.e., before the growth process of the silicon carbide crystal is not initiated; or before the growth process of the silicon carbide crystal is not started, the initial position of the lower end of the liquid level maintaining ring is 1-3 mm lower than the liquid level of the Si alloy auxiliary solution; in the invention, the lower end of the liquid level maintaining ring is preferably located 1-3 mm below the liquid level of the Si alloy auxiliary solution before the growth starts, namely the liquid level maintaining ring is in a contact state with the Si alloy auxiliary solution at the beginning of the growth, so that the phenomenon that the liquid level maintaining ring is suddenly pushed into the Si alloy auxiliary solution to generate sudden interference on growth conditions can be effectively avoided, and the stability of the growth conditions is not ensured.

According to some embodiments, the method of growing silicon carbide crystals by the liquid phase method of the present invention comprises the steps of: in the liquid phase method for growing silicon carbide single crystal according to the present invention, first Si and a metal simple substance are mixed according to Si_aX_bThe components are put into a graphite crucible (wherein X can be one or more of Cr, Al, Yb, Pr and Ce, a is more than or equal to 0.30 and less than or equal to 0.60, b is more than or equal to 0.40 and less than or equal to 0.70, and a + b is 1). The structure shown in FIG. 1 was loaded into an apparatus for growing silicon carbide crystals by the liquid phase method, and the experimental apparatus (crucible) was usedPerforming vacuum-pumping operation until the pressure reaches 10^-3And filling Ar or He rare gas of 0.5-1.5 atm into the crucible after Pa is lower, and heating the crucible. When the temperature in the crucible reaches the specified temperature (the temperature for melting the growth raw materials), completely melting Si and alloy in the graphite crucible to obtain Si alloy solution aid, slowly lowering the silicon carbide seed crystal to be within 5mm above the liquid level of the Si alloy solution aid to preheat the silicon carbide seed crystal, and starting the autorotation of the silicon carbide seed crystal and the autorotation of the crucible. In the subsequent heating process, because the Si alloy auxiliary solution corrodes the graphite crucible and dissolves C, the liquid level is further lowered, and the silicon carbide seed crystal can be slowly lowered continuously to ensure that the height between the silicon carbide seed crystal and the liquid level of the Si alloy auxiliary solution is unchanged. After the preheating is finished, the silicon carbide seed crystal is further descended to be in contact with the upper liquid level of the Si alloy fluxing solution, and the descent is stopped after the silicon carbide seed crystal is in contact with the upper liquid level of the Si alloy fluxing solution. When the silicon carbide seed crystal is contacted with the Si alloy auxiliary solution, the crystal growth process starts, the seed crystal is slowly lifted at the speed of 10-500 mu m/h, and the liquid level maintaining ring is slowly pushed into the Si alloy auxiliary solution at the speed of 100-700 mu m/h by a pushing device, so that the height of the Si alloy auxiliary solution is kept unchanged in the whole growth process. In the growth process, the heat preservation condition is gradually worsened, and the heating power is preferably properly controlled in the growth process, so that the heating power is improved by 100-500W. And after the growth is finished, slowly pulling the grown silicon carbide crystal upwards to separate the silicon carbide crystal from the Si alloy cosolvent, and slowly reducing the temperature until the temperature reaches the room temperature, namely finishing the whole growth process of the silicon carbide crystal by the liquid phase method.

The invention provides in a third aspect a silicon carbide crystal obtained by the method of the invention in the second aspect.

The invention will be further illustrated by way of example, but the scope of protection is not limited to these examples.

Example 1

The Si alloy solution adopted in this embodiment is composed of three phases of Si, Cr, and Al, and the atomic ratio thereof is Si: 50%, Cr: 40%, Al: 10 percent. Mixing the elementary particles of the three raw materials uniformly, placing the mixture in a graphite crucible, and performing reaction according to the formula shown in figure 1The structure is put into a device for growing silicon carbide crystals by a liquid phase method, and air in a crucible is pumped to 2 multiplied by 10 by a molecular pump^-4Introducing 1.5atm of Ar gas as protective gas below Pa and heating the crucible, wherein when the temperature in the crucible reaches the melting temperature of the growth raw materials, all Si, Cr and Al in the graphite crucible are melted to obtain a Si alloy solution aid, and in the embodiment, the initial position of the liquid level maintaining ring of the liquid level height maintaining device during charging is adjusted to a position that the lower end of the liquid level maintaining ring is 1-3 mm lower than the liquid level of the Si alloy solution. After the temperature of the Si alloy co-solution stabilized to 1800 deg.C (the growth temperature of the silicon carbide crystal), the silicon carbide seed crystal was lowered 3mm above the liquid surface and rotated at 40rpm while the graphite crucible was rotated in the reverse direction at 20 rpm. After the preheating process is finished for 1h, the silicon carbide seed crystal is descended to be contacted with the liquid surface of the Si alloy auxiliary solution, then the descending process of the silicon carbide seed crystal is stopped, and the growth process of the silicon carbide crystal is started. And in the growth process of the silicon carbide crystal, slowly pulling the silicon carbide seed crystal at the speed of 0.2mm/h, and descending the liquid level height maintaining device into the Si alloy auxiliary solution at the speed of 0.1mm/h to maintain the circular ring. After the whole growth process lasts for 60 hours, pulling up the silicon carbide seed crystal at the speed of 3mm/h to separate the grown silicon carbide crystal from the liquid level of the Si alloy auxiliary solution, and slowly cooling to room temperature, namely, completing the whole liquid phase method silicon carbide crystal growth process to obtain the silicon carbide crystal; the graphite crucible used in this example had an inner diameter of 100mm, an outer diameter of 140mm and a height of 100 mm. The silicon carbide seed crystal is 4H-SiC grown by adopting a PVT method, the diameter of the silicon carbide seed crystal is 50mm, and the thickness of the silicon carbide seed crystal is 0.5 mm. The liquid level height keeping device has a liquid level keeping ring with an inner diameter of 70mm, an outer diameter of 98mm and a height of 20mm, and the liquid level keeping ring is made of graphite.

The silicon carbide crystal grown in this example had a profile view (top view) as shown in FIG. 2 (a); as can be seen from FIG. 2(a), the surface of the silicon carbide crystal in this example is clean and clean, and the quality of the silicon carbide crystal is good.

The diameter variation graph of the silicon carbide crystal grown in the present example is shown in FIG. 3; fig. 3 shows that the diameter of the silicon carbide crystal growth crystal (abbreviated as crystal diameter in fig. 3) tends to expand first and then stabilize in the whole growth process, and as can be seen from fig. 3, the crystal diameter of the silicon carbide crystal tends to stabilize when the growth thickness reaches 4mm, and the crystal diameter of the silicon carbide crystal also stabilizes between 53 mm and 53.5mm even when the growth thickness reaches 7 mm.

Example 2

Example 2 is essentially the same as example 1, except that:

and in the growth process of the silicon carbide crystal, slowly pulling the silicon carbide seed crystal at the speed of 0.2mm/h, and descending the liquid level height maintaining device into the Si alloy auxiliary solution at the speed of 0.2mm/h to maintain the circular ring.

The silicon carbide crystal grown in this example had a profile view (top view) as shown in FIG. 2 (b); as can be seen from fig. 2(b), the surface of the silicon carbide crystal in this embodiment has many undulations and ravines, in which Si alloy solution and silicon carbide polycrystalline particles are included, and the quality of the silicon carbide crystal is deteriorated.

The diameter variation graph of the silicon carbide crystal grown in the present example is shown in FIG. 4; as can be seen from FIG. 4, the diameter of the silicon carbide crystal (abbreviated as crystal diameter in FIG. 4) shows a significant expansion characteristic from 50.8mm to 57mm during the whole growth process, which indicates that the too fast pressing liquid level height maintaining ring makes the height of the Si alloy solution higher, which is not favorable for stabilizing the crystal growth and maintaining the crystal quality.

Example 3

Example 3 is essentially the same as example 1, except that:

and after the whole growth process lasts for 90 hours, pulling up the silicon carbide seed crystal at the speed of 3mm/h to separate the grown silicon carbide crystal from the liquid level of the Si alloy auxiliary solution, and slowly cooling to room temperature, namely finishing the whole growth process of the liquid phase method silicon carbide crystal to obtain the silicon carbide crystal.

The diameter of the crystal grown in this example varied with the thickness of the crystal grown as shown in FIG. 5, and the surface profile (plan view) of the silicon carbide crystal grown in this example was as shown in FIG. 2 (c); it can be seen from the growth results that the growth thickness of the silicon carbide crystal grown in this embodiment reaches 10.5mm, the surface of the silicon carbide crystal is clean and tidy, the diameter of the silicon carbide crystal (abbreviated as crystal diameter in fig. 5) still shows a tendency of first expansion and then stabilization with the increase of the growth thickness, the crystal diameter of the silicon carbide crystal tends to be stable when the growth thickness reaches 4mm, and even if the growth thickness reaches 10.5mm, the crystal diameter of the silicon carbide crystal also stabilizes between 53 mm and 53.5mm, which indicates that the growth conditions in this embodiment are stable, the quality of the silicon carbide crystal is high, and the growth thickness of the obtained silicon carbide crystal can be improved, so that a silicon carbide ingot with high quality and thickness can be obtained by one-time growth, and the yield is effectively improved without increasing the cost.

Comparative example 1

The apparatus for growing a silicon carbide crystal by the liquid phase method according to the present comparative example has substantially the same structure as that shown in FIG. 1, except that the apparatus for growing a silicon carbide crystal by the liquid phase method according to the present comparative example does not include the liquid level height maintaining means.

The method for growing a silicon carbide crystal by the liquid phase method employed in this comparative example was substantially the same as in example 1 except that the operation step associated with the liquid level maintaining means was not included.

FIG. 2(d) is a schematic plan view of the silicon carbide crystal grown in this comparative example; as can be seen from FIG. 2(d), the silicon carbide crystal of this comparative example exhibited significant dishing in the surface and incorporated a large amount of Si alloy co-solution, and the quality of the silicon carbide crystal was poor.

The diameter variation of the silicon carbide crystal grown in this comparative example is shown in FIG. 6; fig. 6 shows that the diameter of the silicon carbide crystal growth (abbreviated as crystal diameter in fig. 6) shows a tendency of first expansion and then reduction in the whole growth process, and as can be seen from fig. 6, the crystal diameter of the silicon carbide crystal reaches a maximum value when the growth thickness reaches 3mm, then gradually reduces with the increase of the growth thickness, and even reduces to 49.5mm (smaller than the diameter of the silicon carbide seed crystal) when the growth thickness reaches 7mm, which indicates that the growth conditions in the present comparative example are not stable enough, the quality of the silicon carbide crystal growth is poor, the phenomenon that the diameter of the crystal growth is obviously reduced occurs, the stability of the crystal growth is damaged, and the silicon carbide crystal growth with large thickness cannot be guaranteed.

Comparative example 2

Changing the growth raw material to V₂O₅、Y₂O₃、Nd₂O₃The material of the polycrystal, the crucible and the liquid level maintaining ring of the liquid level maintaining apparatus was changed to iridium at 1850 ℃ for growth of YVO in the same manner as in example 1₄And (3) single crystal.

This comparative example found YVO grown in a constant temperature field with a liquid level height maintaining device₄yVO grown in temperature-variable field with single crystal quality and no liquid level height maintaining device₄There is no significant difference in the quality of the single crystal. The method has obvious advantages in the process of growing the silicon carbide single crystal by the liquid phase method, which is mainly that the silicon carbide grown by the liquid phase method not only involves the precipitation of the crystal, but also dissolves the solute (the process of dissolving the graphite crucible), so that the method has higher requirements on the liquid level height of the Si alloy auxiliary solution, and the method can only embody the obvious advantages.

The invention has not been described in detail and is in part known to those of skill in the art.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present 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 solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.