Small-stress crystal and substrate, and crystal growth device and crystal growth method capable of controlling cooling speed

Abstract

The invention belongs to the technical field of crystal growth, and particularly relates to a small-stress crystal, a substrate, a crystal growth device with a controllable cooling speed and a crystal growth method. The surface of the small-stress crystal is free of solution droplet residual traces, residual droplet damage and cracks, the TSD density of the small-stress crystal is smaller than 50 cm <-2 >, and the BPD density of the small-stress crystal is smaller than 100 cm <-2 >. According to the crystal growing device, the gas ring is used for conducting gas purging on the growing crystal, residual liquid drops on the surface of the crystal are blown away, the cooling speed of the crystal is controlled by controlling the flow speed of inert gas, the situation that the surface of the crystal is damaged by the residual liquid drops and cracks are generated is avoided, and the small-stress crystal and the small-stress substrate are obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal growth, and in particular relates to a low-stress crystal and a substrate, and a crystal growth device and a crystal growth method with controllable cooling speed. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Wide bandgap semiconductors represented by silicon carbide have broad application prospects in new energy vehicles, energy storage and other fields. The main growth method of silicon carbide crystals is physical vapor transport, but it has problems such as difficult to control growth stability, diameter expansion and p-type doping. The liquid phase method has a low growth temperature, a relatively stable growth environment, a growth process close to thermodynamic equilibrium conditions, good crystal quality, and the advantages of growing high-quality substrates, as well as the advantages of growing on p-type substrates.

[0004] However, when the crystal is separated from the solution, due to the existence of surface tension, a droplet will be attached to the surface of the crystal, becoming a residual droplet. When the residual droplet changes from liquid to solid, it will generate thermoelastic stress on the crystal and compressive stress on the back of the crystal, which can reach 1.19GPa. The excessive stress generated by the droplets remaining on the surface of the crystal causes the crystal quality of the tail section to deteriorate, and in severe cases, it can cause the crystal to crack. In view of the impact of residual solution droplets on the growing crystal, the usual practice is to reduce the size of the residual droplets as much as possible, such as quickly pulling away from the solution after the crystal growth is completed, or using the centrifugal force generated by the rapid rotation of the upper shaft to reduce the size of the residual droplets. However, the above method cannot guarantee the complete elimination of residual droplets on the crystal. If the cooling rate cannot be controlled during the cooling process, the stress generated by the residual droplets will generate new defects in the crystal, which may cause the crystal to crack and damage in severe cases.

[0005] The cooling of the crystal is generally achieved by adjusting the furnace temperature. However, in the existing crystal growth device, the cooling speed of the crucible and the crystal is consistent, which cannot be accurately and controllably adjusted. In addition, in the liquid phase method, it is also necessary to consider the damage of the crucible caused by the rapid cooling of the solution in the crucible.

[0006] In summary, it is difficult to ensure that the crucible cools down slowly while effectively controlling the cooling rate of the crystal in the prior art, and it is also difficult to completely eliminate the residual droplets on the crystal. Summary of the invention

[0007] In order to solve the deficiencies of the prior art, the present invention provides a low stress crystal and substrate, and a crystal growth device and a crystal growth method with controllable cooling rate. The crystal growth device provided by the present invention uses a gas ring to purge the growing crystal with gas to blow away residual droplets on the crystal surface, and controls the cooling rate of the crystal by controlling the flow rate of the inert gas to avoid the crystal surface being damaged by the residual droplets and cracks, thereby obtaining a low stress crystal and a low stress substrate.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect, the present invention provides a low stress crystal, wherein the surface of the low stress crystal has no trace of solution droplets, no residual droplet damage, and no cracks, and the TSD density of the low stress crystal is less than 50cm -2 , BPD density is less than 100cm -2 .

[0010] Preferably, the low stress crystal includes silicon carbide, the crystal type of the silicon carbide includes 4H-SiC, 6H-SiC or 3C-SiC, and the conductivity type of the silicon carbide includes n-type, semi-insulating or p-type.

[0011] In a second aspect, the present invention provides a low stress substrate obtained by the low stress crystal processing as described in the first aspect, wherein the stress value of the low stress substrate is ≤30Mpa, the axial stress deviation value is less than 10%, and the radial stress deviation value is less than 10%.

[0012] The average deviation within the surface = maximum or minimum value - average value.

[0013] Preferably, the half-width of the (0004) plane rocking curve of the low-stress substrate is ≤30 arcsec, and the in-plane average deviation is ≤3 arcsec; the length of the edge notch caused by stress is ≤0.5 mm, and the depth of the edge notch is ≤0.5 mm; the total thickness variation TTV of the low-stress substrate is ≤10 μm, the curvature BOW is ±25 μm, and the warpage is ≤40 μm.

[0014] Preferably, the radial stress deviation value of the low-stress substrate is less than 5%.

[0015] More preferably, the half-width of the rocking curve of the (0004) plane is ≤15 arcsec, and the in-plane average deviation is ≤2 arcsec.

[0016] Further preferably, the low stress substrate has no notch at the edge, a total thickness variation TTV≤5 μm, a curvature BOW of ±15 μm, and a warpage ≤20 μm.

[0017] In a third aspect, the present invention provides a crystal growth device with controllable cooling rate, which is used to grow the low stress crystal as described in the first aspect, comprising:

[0018] A crucible, wherein a heat-insulating material is arranged outside the crucible, the crucible is arranged on a crucible supporting shaft, and an upper heat-insulating port is arranged on the upper part of the crucible and the heat-insulating material;

[0019] A heating coil, wherein the heating coil is arranged outside the heat-insulating material;

[0020] A seed crystal shaft, one end of which is connected to the seed crystal, and the other end of which is connected to the water-cooling shaft;

[0021] A gas ring, wherein the gas ring is provided with a plurality of gas nozzles facing the inner diameter direction, the gas nozzles are located on the outside of the cylinder formed by the moving trajectory of the seed crystal axis and the water-cooling axis, the gas ring is fixedly arranged on the upper insulation port or connected to one or more lifting rods, and the lifting rods are arranged through the top wall of the crystal growth device and are parallel to the water-cooling axis.

[0022] Preferably, the gas ring consists of two half rings or a plurality of sector rings.

[0023] Further preferably, the half ring or the fan ring is respectively connected to one or more lifting rods.

[0024] Still further preferably, a plurality of movable grooves are radially provided on the top wall of the crystal growth device, the lifting rods are arranged in the movable grooves, and baffles are sleeved on the lifting rods.

[0025] In a fourth aspect, the present invention provides a crystal growth method with controllable cooling rate, using the crystal growth device as described in the third aspect, comprising the following steps:

[0026] The raw materials are placed in a crucible, the seed crystal is connected to the seed crystal axis, the crystal growth device is evacuated and then an inert gas is introduced, the raw materials are heated and melted to form a solution, and the temperature is continuously raised to a predetermined growth temperature;

[0027] The seed crystal is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, so that the crystal grows;

[0028] After the crystal growth is completed, the crystal is pulled up to be separated from the solution, the gas nozzle is adjusted to be flush with the crystal surface, and the gas nozzle sprays inert gas to blow the residual droplets on the crystal surface away from the crystal surface;

[0029] By setting the cooling curve, adjust the inert gas flow rate to adjust the cooling speed, and take out the crystal after the cooling is completed.

[0030] Preferably, when increasing the inert gas flow rate cannot meet the cooling rate, the rising gas ring and the crystal are moved away from the upper insulation port at the same time.

[0031] Preferably, when reducing the inert gas flow rate cannot meet the temperature reduction rate, the seed crystal axis is lowered to allow the crystal to extend into the crucible.

[0032] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0033] The surface of the low-stress crystal of the present invention has no residual droplet damage and no cracks, and the TSD density and BSD density are greatly reduced, so dislocation caused by stress is prevented, the crystal quality is improved, and high-quality, low-stress substrate products can be further processed.

[0034] The stress value and stress deviation value of the low stress substrate obtained by further processing the low stress crystal are reduced, the edge defects caused by stress are avoided, the uniformity is good, and it can be used as an epitaxial substrate or seed crystal, which is beneficial to improve the production quality of downstream products.

[0035] A gas ring is provided in the crystal growth device. The gas ring can remove residual droplets on the surface of the crystal by spraying air flow to the crystal, and can control the cooling rate of the crystal by the inert gas flow rate without affecting the cooling rate of the crucible. It can effectively solve the stress caused by residual droplets and uncontrollable cooling rate and prevent crystal damage.

[0036] In the crystal growth mode, the inert gas flow rate is adjusted according to the set cooling curve to adjust the cooling speed, and the position of the crystal is further adjusted when the gas flow rate cannot meet the cooling speed, so as to meet the cooling needs of the crystal in different situations and realize independent controllable crystal cooling speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0038] Figure 1 is a schematic structural diagram of the crystal growth device in Example 1;

[0039] Figure 2 is a schematic diagram of the structure of the gas ring in Example 1;

[0040] Figure 3 is a schematic structural diagram of the crystal growth device in Example 2;

[0041] Figure 4 is a schematic structural diagram of the crystal growth device in Example 3;

[0042] In the figure, 1 is a crucible, 2 is a heat-insulating material, 3 is a crucible supporting shaft, 4 is a heating coil, 5 is a seed crystal shaft, 6 is a seed crystal, 7 is a water-cooling shaft, 8 is a gas ring, 9 is a gas nozzle, 10 is a lifting rod, and 11 is a baffle. DETAILED DESCRIPTION

[0043] As described in the background technology, when the crystal is separated from the solution, a droplet will be attached to the surface of the crystal due to the existence of surface tension, which becomes a residual droplet. When the residual droplet changes from liquid to solid, it will generate thermoelastic stress on the crystal and compressive stress on the back of the crystal. The stress generated by the residual droplet during the cooling process may damage the crystal.

[0044] In order to solve the above problems, the present invention provides a low-stress crystal and a substrate, and a crystal growth device and a crystal growth method with controllable cooling speed.

[0045] The embodiment of the present invention provides a low stress crystal, wherein the surface of the low stress crystal has no trace of solution droplets, no residual droplet damage, and no cracks, and the TSD density of the low stress crystal is less than 50cm -2 , BPD density is less than 100cm -2 .

[0046] In some embodiments of the present invention, the low stress crystal includes silicon carbide, the crystal form of the silicon carbide includes 4H-SiC, 6H-SiC or 3C-SiC, and the conductivity type of the silicon carbide includes n-type, semi-insulating or p-type.

[0047] An embodiment of the present invention provides a substrate obtained by the low stress crystal processing as described above, wherein the stress value of the low stress substrate is ≤30 MPa, the axial stress deviation value is less than 10%, and the radial stress deviation value is less than 10%.

[0048] In some embodiments of the present invention, the half-height width of the (0004) plane rocking curve of the low-stress substrate is ≤30 arcsec, and the in-plane average deviation is ≤3 arcsec; the length of the edge notch caused by stress in the low-stress substrate is ≤0.5 mm, and the depth of the edge notch is ≤0.5 mm; the total thickness variation TTV of the low-stress substrate is ≤10 μm, the curvature BOW is ±25 μm, and the warpage is ≤40 μm.

[0049] In some embodiments of the present invention, the radial stress deviation value of the low-stress substrate is less than 5%.

[0050] In some embodiments of the present invention, the half-height width of the (0004) plane rocking curve is ≤15 arcsec, the in-plane average deviation is ≤2 arcsec; there is no notch at the edge, the total thickness variation TTV is ≤5 μm, the curvature BOW is ±15 μm, and the warpage is ≤20 μm.

[0051] An embodiment of the present invention provides a crystal growth device with controllable cooling speed, which is used to grow the small stress crystal as described above, comprising:

[0052] A crucible, wherein a heat-insulating material is arranged outside the crucible, the crucible is arranged on a crucible supporting shaft, and an upper heat-insulating port is arranged on the upper part of the crucible and the heat-insulating material;

[0053] A heating coil, wherein the heating coil is arranged outside the heat-insulating material;

[0054] A seed crystal shaft, one end of which is connected to the seed crystal, and the other end of which is connected to the water-cooling shaft;

[0055] A gas ring, wherein the gas ring is provided with a plurality of gas nozzles facing the inner diameter direction, the gas nozzles are located on the outside of the cylinder formed by the moving trajectory of the seed crystal axis and the water-cooling axis, the gas ring is fixedly arranged on the upper insulation port or connected to one or more lifting rods, and the lifting rods are arranged through the top wall of the crystal growth device and are parallel to the water-cooling axis.

[0056] After the crystal growth is completed, the gas nozzle is flush with the crystal surface, and then the gas valve is opened, and the gas is blown to the crystal surface through the gas nozzle to blow away the residual droplets on the crystal surface. The gas ring is fixedly set on the upper insulation port or can be axially moved by the lifting rod, both of which can realize the use of thermal radiation from the upper insulation port to heat the crystal, and the residual droplets are blown away through the gas nozzle without causing a significant impact on the temperature of the crystal.

[0057] In some embodiments of the present invention, the gas ring consists of two half rings or a plurality of sector rings.

[0058] In some embodiments of the present invention, the half ring or the sector ring is respectively connected to one or more lifting rods.

[0059] In some embodiments of the present invention, a plurality of movable grooves are radially provided on the top wall of the crystal growth device, the lifting rods are arranged in the movable grooves, and baffles are sleeved on the lifting rods.

[0060] By setting the moving groove, the fan ring or half ring can move radially with the lifting rod, so as to be suitable for crystals of different sizes. The set baffle can prevent the steam generated by the solution from overflowing through the moving groove to avoid pollution and safety hazards.

[0061] An embodiment of the present invention provides a crystal growth method with controllable cooling rate, using the crystal growth device as described above, comprising the following steps:

[0062] The raw materials are placed in a crucible, the seed crystal is connected to the seed crystal axis, the crystal growth device is evacuated and then an inert gas is introduced, the raw materials are heated and melted to form a solution, and the temperature is continuously raised to a predetermined growth temperature;

[0063] The seed crystal is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, so that the crystal grows;

[0064] After the crystal growth is completed, the crystal is pulled up to be separated from the solution, the gas nozzle is adjusted to be flush with the crystal surface, and the gas nozzle sprays inert gas to blow the residual droplets on the crystal surface away from the crystal surface;

[0065] By setting the cooling curve, adjust the inert gas flow rate to adjust the cooling speed, and take out the crystal after the cooling is completed.

[0066] In some embodiments of the present invention, when increasing the inert gas flow rate cannot meet the cooling rate, the rising gas ring and the crystal are moved away from the upper insulation port at the same time.

[0067] In some embodiments of the present invention, when reducing the flow rate of the inert gas cannot meet the cooling rate, the seed crystal axis is lowered to allow the crystal to extend into the crucible.

[0068] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0069] Example 1

[0070] like Figure 1 As shown, a crystal growth device with controllable cooling speed comprises:

[0071] A crucible 1, a heat-insulating material 2 is arranged outside the crucible 1, the crucible 1 is arranged on a crucible supporting shaft 3, and an upper heat-insulating port is arranged on the upper part of the crucible 1 and the heat-insulating material 2;

[0072] The heating coil 4 is arranged outside the heat-insulating material 2;

[0073] A seed crystal shaft 5, one end of which is connected to a seed crystal 6, and the other end of which is connected to a water-cooled shaft 7;

[0074] The gas ring 8 is provided with a plurality of gas nozzles 9 facing the inner diameter direction. The gas nozzles 9 are located outside the cylinder formed by the moving tracks of the seed crystal shaft 5 and the water-cooling shaft 7. The gas ring 8 is fixedly arranged at the upper insulation port.

[0075] Using the crystal growth device to grow silicon carbide crystals includes the following steps:

[0076] The raw materials (Si, Cr) are placed in a crucible 1, the seed crystal 6 is connected to the seed crystal shaft 5, the crystal growth device is evacuated and then an inert gas is introduced, the raw materials are heated to melt to form a solution, and the temperature is continuously raised to a predetermined growth temperature;

[0077] The seed crystal 6 is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, so that the crystal grows;

[0078] After the crystal growth is completed, the crystal is pulled to separate from the solution, the gas nozzle 9 is adjusted to be flush with the crystal surface, and the gas nozzle sprays inert gas to blow the residual droplets on the crystal surface away from the crystal surface;

[0079] By adjusting the inert gas flow rate to adjust the cooling speed through the set cooling curve, the crystal is taken out after the cooling is completed; when reducing the inert gas flow rate cannot meet the cooling speed, the seed crystal axis 5 is lowered to allow the crystal to extend into the crucible 1, and the crystal is taken out after the cooling is completed.

[0080] The surface of the obtained low stress crystal has no traces of solution droplets, no residual droplet damage, and no cracks. The TSD density of the low stress crystal is less than 50cm -2 , BPD density is less than 100cm -2 The low stress crystal is processed into a low stress substrate, the stress value of the low stress substrate is ≤30Mpa, the axial stress deviation value is less than 10%, and the radial stress deviation value is less than 10%; the half-height width of the (0004) plane rocking curve is ≤30arcsec, and the in-plane average deviation is ≤3arcsec; the edge notch length of the low stress substrate caused by stress is ≤0.5mm, and the edge notch depth is ≤0.5mm; the TTV of the low stress substrate is ≤10μm, the BOW is ±25μm, and the warpage is ≤40μm.

[0081] Example 2

[0082] like Figure 2 As shown, a crystal growth device with controllable cooling speed comprises:

[0083] A crucible 1, a heat-insulating material 2 is arranged outside the crucible 1, the crucible 1 is arranged on a crucible supporting shaft 3, and an upper heat-insulating port is arranged on the upper part of the crucible 1 and the heat-insulating material 2;

[0084] The heating coil 4 is arranged outside the heat-insulating material 2;

[0085] A seed crystal shaft 5, one end of which is connected to a seed crystal 6, and the other end of which is connected to a water-cooled shaft 7;

[0086] Gas ring 8, such as Figure 3 The figure shows that it includes two half rings, each of which is provided with a plurality of gas nozzles 9 facing the inner diameter direction, and the gas nozzles 9 are located on the outside of the cylinder formed by the moving trajectory of the seed crystal axis 5 and the water-cooling axis 7. Each half ring is connected to a lifting rod 10, and the lifting rod 10 is penetrated and arranged on the top wall of the crystal growth device. The half ring can move along the axial direction of the seed crystal axis 5 and the water-cooling axis 7 through the lifting rod.

[0087] The crystal growth device is used to grow crystals, comprising the following steps:

[0088] The raw materials (Si, Cr) are placed in a crucible 1, the seed crystal 6 is connected to the seed crystal shaft 5, the crystal growth device is evacuated and then an inert gas is introduced, the raw materials are heated to melt to form a solution, and the temperature is continuously raised to a predetermined growth temperature;

[0089] The seed crystal 6 is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, so that the crystal grows;

[0090] After the crystal growth is completed, the crystal is pulled to separate from the solution, the gas nozzle 9 is adjusted to be flush with the crystal surface, and the gas nozzle sprays inert gas to blow the residual droplets on the crystal surface away from the crystal surface;

[0091] By adjusting the inert gas flow rate to adjust the cooling speed through the set cooling curve, the crystal is taken out after the cooling is completed; when reducing the inert gas flow rate cannot meet the cooling speed, the seed crystal axis 5 is lowered to allow the crystal to extend into the crucible 1, and the crystal is taken out after the cooling is completed.

[0092] The surface of the obtained low stress crystal has no traces of solution droplets, no residual droplet damage, and no cracks. The TSD density of the low stress crystal is less than 45cm -2 , BPD density is less than 90cm -2 The low stress crystal is processed into a low stress substrate, the stress value of the low stress substrate is ≤25Mpa, the axial stress deviation value is less than 8%, and the radial stress deviation value is less than 8%; the half-height width of the (0004) plane rocking curve is ≤20arcsec, and the in-plane average deviation is ≤2.5arcsec; the edge notch length of the low stress substrate caused by stress is ≤0.3mm, and the edge notch depth is ≤0.3mm; the TTV of the low stress substrate is ≤8μm, the BOW is ±20μm, and the warpage is ≤30μm.

[0093] Example 3

[0094] like Figure 4 As shown, a crystal growth device with controllable cooling speed comprises:

[0095] A crucible 1, a heat-insulating material 2 is arranged outside the crucible 1, the crucible 1 is arranged on a crucible supporting shaft 3, and an upper heat-insulating port is arranged on the upper part of the crucible 1 and the heat-insulating material 2;

[0096] The heating coil 4 is arranged outside the heat-insulating material 2;

[0097] A seed crystal shaft 5, one end of which is connected to a seed crystal 6, and the other end of which is connected to a water-cooled shaft 7;

[0098] The gas ring 8 includes two half rings, each half ring is provided with a plurality of gas nozzles 9 facing the inner diameter direction, and the gas nozzles 9 are located on the outside of the cylinder formed by the moving tracks of the seed crystal shaft 5 and the water-cooling shaft 7. Each half ring is connected to a lifting rod 10, and each lifting rod 10 passes through a moving groove provided on the top wall of the crystal growth device. A baffle 11 located on the outside of the crystal growth device is sleeved on the lifting rod 10, and the half ring can move axially and radially along the crystal growth device through the lifting rod.

[0099] The crystal growth device is used to grow crystals, comprising the following steps:

[0100] The raw materials (Si, Cr) are placed in a crucible 1, the seed crystal 6 is connected to the seed crystal shaft 5, the crystal growth device is evacuated and then an inert gas is introduced, the raw materials are heated to melt to form a solution, and the temperature is continuously raised to a predetermined growth temperature;

[0101] The seed crystal 6 is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, so that the crystal grows;

[0102] After the crystal growth is completed, the crystal is pulled to separate from the solution, the gas nozzle 9 is adjusted to be flush with the crystal surface, and the gas nozzle sprays inert gas to blow the residual droplets on the crystal surface away from the crystal surface;

[0103] By adjusting the inert gas flow rate to adjust the cooling speed through the set cooling curve, the crystal is taken out after the cooling is completed; when reducing the inert gas flow rate cannot meet the cooling speed, the seed crystal axis 5 is lowered to allow the crystal to extend into the crucible 1, and the crystal is taken out after the cooling is completed.

[0104] The surface of the obtained low stress crystal has no traces of solution droplets, no residual droplet damage, and no cracks. The TSD density of the low stress crystal is less than 40cm -2 , BPD density is less than 80cm -2 The low stress crystal is processed into a low stress substrate, the stress value of the low stress substrate is ≤20Mpa, the axial stress deviation value is less than 5%, and the radial stress deviation value is less than 5%; the half-height width of the (0004) surface rocking curve is ≤15arcsec, and the in-plane average deviation is ≤2arcsec; there is no notch at the edge of the low stress substrate; the TTV of the low stress substrate is ≤5μm, the BOW is ±15μm, and the warpage is ≤20μm.

[0105] Comparative Example 1

[0106] A crystal growth apparatus, comprising:

[0107] A crucible 1, a heat-insulating material 2 is arranged outside the crucible 1, the crucible 1 is arranged on a crucible supporting shaft 3, and an upper heat-insulating port is arranged on the upper part of the crucible 1 and the heat-insulating material 2;

[0108] The heating coil 4 is arranged outside the heat-insulating material 2;

[0109] The seed crystal shaft 5 has one end connected to the seed crystal 6 and the other end connected to the water-cooling shaft 7 .

[0110] The crystal growth device is used to grow crystals, comprising the following steps:

[0111] The raw material is placed in the crucible 1, the seed crystal 6 is connected to the seed crystal shaft 5, the crystal growth device is evacuated and then an inert gas is introduced, the raw material is heated and melted to form a solution, and the temperature is continuously raised to a predetermined growth temperature;

[0112] The seed crystal is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, so that the crystal grows;

[0113] After the crystal growth is completed, the crystal is pulled up to separate from the solution, and the temperature is cooled. After the cooling is completed, the crystal is taken out.

[0114] The surface of the obtained crystal has traces of solution droplets, and there are residual droplet damage and cracks. The crystal TSD density is greater than 50cm -2 , BPD density is greater than 100cm -2 The crystal was processed into a substrate, the stress value of the substrate was >30Mpa, the axial stress deviation value was greater than 10%, and the radial stress deviation value was greater than 10%; the half-height width of the (0004) plane rocking curve was >30arcsec, and the in-plane average deviation was >3arcsec; the edge notch length of the substrate caused by stress was >0.5mm, and the edge notch depth was >0.5mm; the TTV of the low-stress substrate was >10μm, and the warpage was greater than 40μm.

[0115] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A low stress crystal, characterized in that: The surface of the small stress crystal has no trace of solution droplets, no residual droplet damage, and no cracks, and the TSD density of the small stress crystal is less than 50cm -2 , BPD density is less than 100cm -2 .

2. The low stress crystal according to claim 1, characterized in that: The low stress crystal includes silicon carbide, the crystal type of the silicon carbide includes 4H-SiC, 6H-SiC or 3C-SiC, and the conductivity type of the silicon carbide includes n-type, semi-insulating or p-type.

3. A low stress substrate, characterized in that: Obtained by processing the low stress crystal as claimed in claim 1 or 2, the stress value of the low stress substrate is ≤30Mpa, the axial stress deviation value is less than 10%, and the radial stress deviation value is less than 10%.

4. The low stress substrate according to claim 3, characterized in that: The half-width at half maximum of the (0004) surface rocking curve is ≤30arcsec, and the in-plane average deviation is ≤3arcsec; the edge notch length caused by stress in the low-stress substrate is ≤0.5mm, and the edge notch depth is ≤0.5mm; the total thickness change of the low-stress substrate is ≤10μm, the curvature is ±25μm, and the warpage is ≤40μm.

5. A crystal growth device with controllable cooling rate, characterized in that: For growing the low stress crystal as claimed in claim 1 or 2, comprising: A crucible, wherein a heat-insulating material is arranged outside the crucible, the crucible is arranged on a crucible supporting shaft, and an upper heat-insulating port is arranged on the upper part of the crucible and the heat-insulating material; A heating coil, wherein the heating coil is arranged outside the heat-insulating material; A seed crystal shaft, one end of which is connected to the seed crystal, and the other end of which is connected to the water-cooling shaft; A gas ring, wherein the gas ring is provided with a plurality of gas nozzles facing the inner diameter direction, the gas nozzles are located on the outside of the cylinder formed by the moving trajectory of the seed crystal axis and the water-cooling axis, the gas ring is fixedly arranged on the upper insulation port or connected to one or more lifting rods, and the lifting rods are arranged through the top wall of the crystal growth device and are parallel to the water-cooling axis.

6. The crystal growth apparatus according to claim 5, characterized in that The gas ring is composed of two half rings or a plurality of sector rings, and the half rings or sector rings are respectively connected to one or more lifting rods.

7. The crystal growth apparatus according to claim 6, wherein: The top wall of the crystal growth device is provided with a plurality of moving grooves along the radial direction, the lifting rods are arranged in the moving grooves, and baffles are sleeved on the lifting rods.

8. A crystal growth method with controllable cooling rate, characterized in that: Using the crystal growth apparatus as claimed in any one of claims 5 to 7 comprises the following steps: The raw materials are placed in a crucible, the seed crystal is connected to the seed crystal axis, the crystal growth device is evacuated and then an inert gas is introduced, the raw materials are heated and melted to form a solution, and the temperature is continuously raised to a predetermined growth temperature; The seed crystal is lowered until it contacts the liquid surface of the solution, and then the seed crystal is pulled up to form a meniscus, and crystal growth is performed; After the crystal growth is completed, the crystal is pulled up to be separated from the solution, the gas nozzle is adjusted to be flush with the crystal surface, and the gas nozzle sprays inert gas to blow the residual droplets on the crystal surface away from the crystal surface; By setting the cooling curve, adjust the inert gas flow rate to adjust the cooling speed, and take out the crystal after the cooling is completed.

9. The crystal growth method according to claim 8, characterized in that When increasing the inert gas flow rate cannot meet the cooling rate, the rising gas ring and the crystal move away from the upper insulation port at the same time.

10. The crystal growth method according to claim 8, characterized in that When reducing the inert gas flow rate cannot meet the cooling rate, the seed crystal axis is lowered to allow the crystal to extend into the crucible.

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