Crystal growth device and crystal growth method for adjusting vertical temperature gradient by adopting heat insulation plate

Abstract

The invention discloses a crystal growth device and a crystal growth method adopting a heat insulation plate to adjust a vertical temperature gradient, the heat insulation plate is introduced between a heater and a crystal growth crucible, the relative positions of the heater and the crystal growth crucible are kept immobile, and the temperature gradient in the vertical direction in a growth chamber is adjusted by utilizing the lifting of the heat insulation plate; therefore, solidification and crystallization of the semiconductor melt in the crucible from bottom to top are achieved, and the single crystal growth process is completed. The device and the crystal growth method are suitable for semiconductor crystal materials such as gallium oxide which can be grown by adopting a melt method. Compared with a traditional method that power is reduced from bottom to top through multiple sets of heaters or a crucible is lowered relative to the heaters, the crystal growth method can keep high stability of a thermal field in the crystal growth process and linear pushing of a crystal growth interface, and therefore the controllability of crystal growth is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor single crystal material preparation, and particularly relates to a crystal growth device and a crystal growth method for adjusting a vertical temperature gradient by using a heat insulation plate. BACKGROUND

[0002] The melt method is a growth method for forming crystals by directional solidification of a molten substance. High-purity raw materials are heated to above the melting point to form a uniform melt, and atomic ordering is achieved by directional solidification or seed crystal induction under a specific temperature gradient. During the phase transition from liquid to solid, the supercooling degree and the growth rate need to be accurately controlled to avoid the formation of polycrystals or defects. The melt method can be applied to the growth of various crystal materials.

[0003] For example, gallium oxide (Ga2O3) is a new generation of ultra-wide bandgap semiconductor material, which has an ultra-wide bandgap width of 4.8-5.3 eV and a breakdown electric field strength of up to 8 MV / cm, and has important application prospects in high-voltage power devices, radio frequency devices, solar blind ultraviolet detectors, and extreme environment electronic devices. In particular, driven by the demand of emerging markets such as electric vehicle charging piles, data center power supplies, and 5G base station power amplifiers, gallium oxide power devices are expected to be industrialized and applied in the next 5-10 years, becoming the third generation of power semiconductor core materials after silicon and silicon carbide. Compared with SiC and GaN, gallium oxide can directly grow large-size single crystal substrates by the melt method, significantly reducing the manufacturing cost. In recent years, with the continuous maturity of the crystal growth technology such as the crucible lowering method (i.e. the vertical Bridgman method or VB method) and the VGF method, the batch production of 2-4 inch high-quality β-Ga2O3 single crystals has been realized, and 6 inch β-Ga2O3 single crystals have been reported.

[0004] The current vertical temperature gradient method (VGF) and the vertical Bridgman method (VB) are the main preparation technologies for β-Ga2O3 single crystals. However, these two technologies still face many technical challenges in growing gallium oxide single crystals, and the ultra-high temperature growth environment is the main difficulty. The melting point of gallium oxide is as high as 1795℃, which requires the furnace body to have extremely high temperature stability and uniformity, which puts strict requirements on the heating elements, insulation materials and crucible materials, resulting in high equipment cost and difficult maintenance. In the VB method, due to the mechanical movement of the crucible lowering, the temperature field in the chamber is unstable. Although the VGF method does not have mechanical moving parts during crystal growth, it improves the stability of the crystal growth process, but the method of sequentially lowering the power from bottom to top by using multiple heaters has the disadvantages of complex adjustment, large temperature band and unstable interface movement. Therefore, there is an urgent need to develop a new temperature gradient control method to improve the temperature stability and controllability of the crystal growth temperature field. SUMMARY

[0005] The present application provides a crystal growth device for growing crystals in a thermal field environment with a vertical temperature gradient constructed by lifting a heat insulation plate. Unlike the traditional vertical temperature gradient method (VGF) which uses a method of sequentially reducing the power of a heater to achieve the upward translation of the crystal growth interface and complete the transition of the single crystal from the melt to the crystalline state, the device relies on the up-and-down movement of the heat insulation plate between the heater and the crystal growth crucible to complete the translation of the growth interface in the crucible, which is a new type of crystal growth method.

[0006] The technical solution of the present application is:

[0007] A crystal growth device for adjusting a vertical temperature gradient by using a heat insulation plate, comprising a heat preservation layer, a heater, a heat insulation plate, a crystal growth crucible, a first lifting mechanism and a second lifting mechanism; the heat preservation layer forms a growth chamber, the heater and the crystal growth crucible are located in the growth chamber, the heater is cylindrical and located between the heat preservation layer and the side wall of the crystal growth crucible; the first lifting mechanism is used to drive the crystal growth crucible to move up and down; the heat insulation plate is cylindrical, and the second lifting mechanism is used to drive the heat insulation plate to move up and down between the heater and the crystal growth crucible, so as to adjust the axial temperature distribution gradient in the crucible by adjusting the relative height of the heat insulation plate and the heater.

[0008] In the spatial distribution of the above components, the crystal growth crucible is located at the center of the growth chamber and is made of Pt / Rh alloy or other high-temperature metal or alloy material, which is used to fill the powder and the melt formed after high-temperature heating and the crystal after crystallization; the crystal growth crucible can be an equal-diameter crucible or a funnel-shaped crucible suitable for small seed crystal growth. With the vertical center of the crystal growth crucible as the axis, the crystal growth device is distributed symmetrically. There is a gap between the heater, the heat preservation layer, the heat insulation plate and the crystal growth crucible, which is filled with process gas during crystal growth.

[0009] Optionally, the heater is a resistance heater with a maximum heating temperature not lower than 1800℃, preferably a silicon-molybdenum material heater.

[0010] Optionally, the thickness of the heat insulation plate is 5-30mm, the material thermal conductivity is 0.5-5W / (m*K), and the surface emissivity is 0.1-0.5. The material properties can effectively block the radiation heat transfer of the heating unit, thereby adjusting the axial heat field distribution of the crucible inside the heat insulation plate ring. For example, the material of the heat insulation plate can be zirconia or alumina ceramic insulation material.

[0011] Optionally, the heat preservation layer comprises a first heat preservation layer and a second heat preservation layer, the second heat preservation layer forms a cylindrical and closed growth chamber, and the first heat preservation layer forms a cylindrical shape and is attached to the outside of the second heat preservation layer. The closed chamber structure is used to maintain the basic thermal field environment of the crystal growth process.

[0012] Further, a peripheral stainless steel water-cooled shell is provided to form the external environment and temperature boundary of the growth chamber. The diameter of the stainless steel water-cooled shell is larger than the diameter of the first insulation layer, and the space between the two is filled with process gas.

[0013] Optionally, the material of the first and second insulation layers comprises at least one of zirconia ceramic and alumina ceramic. For example, the first insulation layer is made of ZrO2 or Al2O3 fiber structure, etc. to improve the insulation performance of the chamber; the second insulation layer is made of ZrO2 insulation bricks stacked to provide the main insulation effect of the thermal field of the chamber.

[0014] Optionally, the bottom of the growth chamber has an insulation plate lifting channel and a crucible access channel; the crystal growth crucible and the first lifting mechanism are connected through a support structure, which comprises a support frame and a support bottom plate, the support frame is used to fix the crystal growth crucible, and the support bottom plate is connected to the bottom of the support frame and matches the crucible access channel.

[0015] Optionally, the lower part of the crystal growth crucible is used to install a seed crystal, and the upper part is used to install growth raw materials; the heater is used to heat the growth raw materials to form a melt, and the melt / crystal growth interface is lifted by lifting the insulation plate.

[0016] Optionally, the insulation effect of the insulation plate, when the insulation plate is lifted to a certain height, an effective axial temperature gradient can be formed in the interior of the crucible in the area flush with the upper part of the insulation plate. By adjusting the power of the heater, an optimal melt / crystal growth interface can be formed at this place, and the temperature gradient at this place can be controlled at 5-30 K / cm, preferably 15-20 K / cm. To achieve the optimization of the above-mentioned temperature gradient, the thickness or the material thermal conductivity of the insulation plate, or the surface emissivity can be adjusted to adjust the insulation effect.

[0017] Optionally, a driving mechanism is further provided to drive the crystal growth crucible to rotate along the central axis.

[0018] A crystal growth method based on the crystal growth device with the insulation plate adjusting the vertical temperature gradient described above, the method comprising the following steps:

[0019] S1. Put a seed crystal into the bottom of the crystal growth crucible, fill in growth raw materials, and use the first lifting mechanism to send the crystal growth crucible into the growth chamber;

[0020] S2. Fill in process gas in the growth chamber, adjust the insulation plate to be flush with the top of the growth chamber by the second lifting mechanism, and melt the growth raw materials into a melt by heating with the heater;

[0021] S3. Control the heater power to make the critical temperature at the upper region of the seed crystal, and then gradually reduce the heater power to make the melt begin to solidify and crystallize from the seed crystal region upwards;

[0022] S4. From the crystal setting-up stage, adjust the rising height of the heat insulation plate through the second lifting mechanism to control the axial temperature gradient in the crystal growth crucible, so that the melt / crystal growth interface rises, and the rising speed of the heat insulation plate is 0.5-8 mm / h;

[0023] S5. After the crystal growth is completed, the heater power is gradually reduced, and the crystal is taken out after the temperature in the growth chamber is reduced to room temperature.

[0024] Optionally, the process gas is filled in the growth chamber, and the atmosphere in the chamber can be kept pure through several gas exchange operations before the filling. The process gas can be air, oxygen, nitrogen, argon, or a mixture of two or more of the above.

[0025] The melt in the crystal growth crucible begins to solidify and crystallize from the seed crystal region upwards, and the crystallization driving force comes from the reduced heater power and the upper-high and lower-low axial temperature gradient of the crucible due to the position of the crucible. Under appropriate conditions, the initial axial temperature gradient can be determined by fine-tuning the relative position of the crucible and the heater. Then, by lifting the heat insulation plate, the heat radiation from the lower part of the heater to the crucible is gradually blocked, so that the axial temperature gradient in the crucible is moved, and the crystal is gradually solidified and crystallized from bottom to top. The higher the position of the heat insulation plate is lifted, the higher the temperature line of the melt / solid growth interface is.

[0026] In the preferred embodiment, the position of the top of the heat insulation plate is equivalent to the position of the optimal melt / solid growth interface, and the movement of the heat insulation plate brings the synchronous upward movement of the optimal melt / solid growth interface, so that the crystal growth process is constantly controllable. Compared with the traditional VGF crystal growth equipment which relies on the sequential reduction of power / temperature of different heaters, the method of moving the heat insulation plate presents the advantages of simplicity, reliability, and easy implementation.

[0027] The crystal growth device and method using the heat insulation plate to adjust the vertical temperature gradient described above are suitable for the preparation of Ga2O3 crystals, and can also be used for other crystals prepared by the melt method, such as GaAs, InP, GaSb, InAs, CdTe, ZnSe, and other semiconductor single crystal materials. According to the type of crystal, the selection of the material of the heat field can be adjusted according to the growth temperature and the growth atmosphere requirements; in order to obtain the optimal growth heat field parameters, the material, thickness, and other parameters of the heat insulation plate can be adjusted synchronously to obtain the axial temperature gradient of the growth interface suitable for the specific single crystal growth, and the rising speed of the heat insulation plate is adjusted accordingly to complete the solidification and crystallization growth of the crystal from bottom to top.

[0028] The beneficial effects of the present application are:

[0029] The present application is different from the current conventional vertical temperature gradient method (VGF) or vertical crucible lowering method (VB) in constructing a vertical direction, movable gradient position melt method crystal growth thermal field environment in a crystal growth crucible, and is a new device and technical approach to adjust the vertical temperature distribution in the crystal growth crucible. The crystal growth device introduces a heat insulation plate between the crucible and the heater, and under the premise of controlling the spatial position of the heater and the spatial position of the crucible to be fixed, adjusts the heat radiation of the heater to the crucible by lifting the heat insulation plate, thereby adjusting the movement of the crystal growth interface temperature line in the crucible, and realizing the continuous cooling crystallization of the melt.

[0030] The crystal growth method based on the crystal growth device avoids the shortcomings that the power of the heater needs to be sequentially lowered from bottom to top in the traditional VGF crystal growth process, which causes the axial gradient to be difficult to linearly and continuously adjust, and also overcomes the problems of potential mechanical vibration and non-uniform thermal field in the crucible caused by the mechanical lowering of the crucible in the VB crystal growth process. By adjusting the thickness or thermal conductivity of the heat insulation plate, different crystal growth temperature gradient fields can also be constructed, which has the advantages of flexibility and efficiency, and is simple to operate and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 The structure schematic diagram of the crystal growth device for adjusting the vertical temperature gradient provided for the embodiment, 1 is a first heat preservation layer, 2 is a second heat preservation layer, 3 is a heater, 4 is a heat insulation plate, 5 is a crystal growth crucible, 6 is a support frame, 7 is a support bottom plate, 8 is a first lifting mechanism, 9 is a second lifting mechanism, 10 is a melt, 11 is a crystal solid, A is a growth chamber, a is a crucible access passage, b is a heat insulation plate lifting passage, and the arrows represent the lifting direction;

[0032] Figure 2 The schematic diagram of the crystal growth device for adjusting the vertical temperature gradient provided for the embodiment by the heat insulation plate, the upper arrow represents the heat radiation of the heating body in the area without the heat insulation plate to the crucible, and the lower arrow represents that when the heat insulation plate exists, the heat radiation of the heating body to the crucible area is blocked;

[0033] Figure 3 The schematic diagram of the crystal growth device for adjusting the vertical temperature gradient provided for the embodiment by the heat insulation plate, when the crystal is grown, the lifting height H of the heat insulation plate and the position of the crystal melt / crystal growth interface relative to the height △h of the crystal equiaxial growth starting point;

[0034] Figure 4 The schematic diagram of the position of the optimal melt / crystal growth interface, i.e. the melt and solid interface, in the crucible obtained by optimizing the power of the heater when the lifting height of the heat insulation plate in Example 1 is 0 mm (a), and the temperature field distribution in the growth chamber under this condition (b);

[0035] Figure 5 The schematic diagram of the position of the melt / solid interface in the crucible (a) and the temperature field distribution in the growth chamber (b) for the case of the heat shield rising height of 100 mm in Example 1, and the optimized heater power.

[0036] Figure 6 The schematic diagram of the position of the melt / solid interface in the crucible (a) and the temperature field distribution in the growth chamber (b) for the case of the heat shield rising height of 110 mm in Example 1, and the optimized heater power.

[0037] Figure 7 The schematic diagram of the position of the melt / solid interface in the crucible (a) and the temperature field distribution in the growth chamber (b) for the case of the heat shield rising height of 120 mm in Example 1, and the optimized heater power.

[0038] Figure 8 The schematic diagram of the position of the melt / solid interface in the crucible (a) and the temperature field distribution in the growth chamber (b) for the case of the heat shield rising height of 130 mm in Example 1, and the optimized heater power.

[0039] Figure 9 The schematic diagram of the position of the melt / solid interface in the crucible (a) and the temperature field distribution in the growth chamber (b) for the case of the heat shield rising height of 140 mm in Example 1, and the optimized heater power.

[0040] Figure 10 The relationship between the position of the melt / solid interface in the crucible and the optimal height Ah of the crystal relative to the position of the crystal at the start of the isodiametric growth for the case of the heat shield rising height H in Example 1, and the fitted curve. DETAILED DESCRIPTION

[0041] The present application will be further explained with reference to the drawings and specific examples. The drawings of the present application are only schematic and are non-limiting with respect to the scope of the present application, as the dimensions are chosen for the clarity of presentation, unless otherwise defined.

[0042] The crystal growth apparatus of the example employing the heat shield to adjust the vertical temperature gradient is shown in Fig. 1. Figure 1As shown, the support structure includes a first heat preservation layer 1, a second heat preservation layer 2, a heater 3, an insulation plate 4, a crystal growth crucible 5, a support frame 6 and a support bottom plate 7, a first lifting mechanism 8 and a second lifting mechanism 9. The first heat preservation layer 1 and the second heat preservation layer 2 enclose a growth chamber A, and there is also a stainless steel water-cooled shell (not shown in the figure) on the periphery.

[0043] The above-mentioned main functional components are distributed in space. The crystal growth crucible 5 is located at the center of the growth chamber A. With the vertical center of the crucible as the axis, the crystal growth device is distributed in axial symmetry. From the outside to the inside, there are a cylindrical and closed stainless steel water-cooled shell, a peripheral cylindrical heat preservation structure composed of the first heat preservation layer 1, a growth chamber A surrounded by the second heat preservation layer 2 material and closed at the top and bottom, a cylindrical heater 3, a cylindrical insulation plate 4 and a crystal growth crucible 5.

[0044] In order to construct a suitable temperature field in the growth chamber, the diameter of the stainless steel water-cooled shell is larger than the diameter of the cylinder composed of the first heat preservation layer 1, and the space between them is filled with process gas. The main part of the internal crystal growth thermal field is composed of the first heat preservation layer 1 and the second heat preservation layer 2 materials. The first heat preservation layer 1 is closely attached to the second heat preservation layer 2. The heater 3 and the insulation plate 4 are distributed between the second heat preservation layer 2 and the crystal growth crucible 5, and there is a space between the structures, which is filled with process gas.

[0045] In order to realize the normal feeding and discharging of the crystal growth device, the crystal growth crucible 5 can be connected to the first lifting mechanism 8 after being fixed by the support structure, so as to realize the up and down movement of the crystal growth crucible 5 in the core area of the thermal field. The crystal growth crucible 5 is fixed by the support frame 6, the support bottom plate 7 is connected to the lower section of the support frame 6, the support bottom plate 7 is connected to the first lifting mechanism 8, and the function of the first lifting mechanism is to send or remove the crystal growth crucible 5 into or out of the growth chamber A by moving up and down, so as to realize the feeding and discharging function, and also to assist in optimizing the best initial crystal growth interface at the initial stage of crystal growth. A crucible access passage a is provided at the bottom of the growth chamber A for feeding or removing the crystal growth crucible 5, and the support bottom plate 7 matches the crucible access passage a to realize the sealing effect. Preferably, the support frame 6 can also realize the sealing effect of the crucible access passage a, so as to maintain the airtight stability of the growth chamber A.

[0046] In order to ensure the uniformity of the crucible heating during the crystal growth process, the first lifting mechanism 8 also has the function of connecting the shaft which can rotate, and drives the crystal growth crucible 5 to rotate around the central axis through a driving mechanism (not shown in the figure).

[0047] In order to realize the function of gradually moving the axial temperature gradient in the crucible in the vertical direction during the crystal growth process, the crystal growth device introduces a cylindrical insulation plate 4, which is inserted between the heater 3 and the crystal growth crucible 5 to isolate the heat radiation from the heater 3 to the crystal growth crucible 5.Figure 2 The temperature field in the growth chamber A is adjusted, especially the axial temperature gradient distribution in the crucible, due to the blocking effect of the heat insulation plate 4 on the heat radiation from the lower part of the heater 3 into the crystal growth crucible 5.

[0048] The heat insulation plate 4 is connected with the second lifting mechanism 9, so that the heat insulation plate 4 can be lifted or lowered in the vertical direction in the growth chamber A to adjust the relative height of the heat insulation plate 4 with the heating body of the heater 3. The lowest height of the heat insulation plate 4 can be flush with the top end of the bottom of the growth chamber A, and the highest height can be lifted to be flush with or above the top of the crystal growth crucible 5. During the crystal growth process, when the crystal growth crucible 5 and the heater 3 are kept stationary, the adjustment of the axial temperature gradient in the crucible, especially the linear rise of the crystal growth interface, can be realized by only lifting the height of the heat insulation plate 4, and the cooling and crystallization of the melt in the crucible from bottom to top are completed.

[0049] The heater 3 used in the crystal growth device is preferably a resistance heater. The height of the heating body of the heater 3 in the longitudinal direction is equivalent to or slightly longer than the height of the crystal growth crucible 5 in the longitudinal direction, so as to ensure the uniformity of the heat field and the complete melting of the powder in the crucible at the initial stage of growth.

[0050] The crystal growth method for adjusting the vertical temperature gradient by using the heat insulation plate, the crystal growth device for adjusting the vertical temperature gradient by using the heat insulation plate, and the method for growing gallium oxide crystals are described below.

[0051] (1) Put the gallium oxide seed crystal into the Pt / Rh alloy crystal growth crucible 5 at the bottom, fill in the gallium oxide raw material, assemble the crystal growth crucible 5 with the support frame 6 and the support bottom plate 7, and then use the first lifting mechanism 8 to send the crystal growth crucible 5 into the growth chamber A as a whole;

[0052] (2) Fill the process gas, preferably O2 or air, into the growth chamber A to maintain a certain pressure, keep the relative position of the crystal growth crucible 5 and the heater 3 stationary, completely lower the heat insulation plate 4, and make the top flush with the lower interface in the growth chamber A, and gradually increase the power of the heater 3 to melt the growth raw material in the crucible into a melt;

[0053] (3) Collect the temperature near the crystal growth crucible 5 by using a thermocouple, control the power of the heater 3 by a computer to make the critical temperature of the gallium oxide melt / solid growth interface in the crystal growth crucible 5 located in the upper region of the seed crystal, and then gradually reduce the power of the heater, so that the melt 10 in the crucible starts to solidify and crystallize upwards from the seed crystal region to form a crystal solid 11;

[0054] (4) Starting from the crystal growth stage, the rising speed of the second lifting mechanism 9 is adjusted by the computer control system, and the height of the heat shield 4 is gradually raised to control the axial temperature gradient in the crucible, so that the melt / crystal critical crystallization temperature interface rises slowly, and the continuous solidification and crystallization of the melt is achieved; the rising process of the heat shield is a uniform process, with a speed of 0.5 to 8 mm / h;

[0055] (5) After the crystal in the crucible is completely solidified, gradually reduce the heater power and remove the crucible and crystal after the temperature in the growth chamber drops to room temperature.

[0056] The vertical temperature gradient in the chamber is adjusted by using a heat shield to meet the gradient solidification crystallization requirements of melt-processed crystals. In principle, this method is applicable to gallium oxide single crystals and other crystals that can be prepared by the melt process, such as semiconductor materials such as GaAs, InP, GaSb, InAs, CdTe, and ZnSe. During the specific crystal growth process, other insulation materials and crucible materials can be replaced according to the crystal growth environment and temperature requirements. In terms of vertical temperature regulation, heat shields with different insulation properties can be selected based on the required vertical axial temperature gradient to block heat transfer from the heating element to the crucible area. At the same time, by simultaneously optimizing parameters such as the thickness of the heat shield, an axial temperature gradient at the crystal growth interface suitable for specific single crystal growth can be obtained, and the rising speed of the heat shield can be adjusted accordingly to complete the bottom-up crystal growth of the crystal.

[0057] Based on the above principles, the method provided by the present invention will be described in more detail below in conjunction with specific embodiments.

[0058] Example 1

[0059] A 4-inch gallium oxide crystal growth device using a heat shield to adjust the vertical temperature gradient, such as Figure 1 As shown in the figure, the first insulation layer of the growth device is made of Al2O3 fiber and is located at the outermost layer of the growth chamber. It is 40mm thick and 270mm high. The second insulation layer is made of ZrO2 ceramic, with an internal diameter (i.e., the diameter of the growth chamber) of 240mm and a height of 220mm. The heater is made of SiMo alloy and is 150mm high. The crystal growth crucible has an internal diameter of 110mm and is made of Pt / Rh alloy. It is 5mm thick and has a total height of 160mm. The constant diameter growth area is 100mm high. The crucible support base has a diameter of 120mm, and the insulation plate is located outside the support base. It is 12mm thick and has a total height of 165mm. The insulation plate is made of zirconium oxide.

[0060] The 4-inch gallium oxide crystal growth apparatus using the heat shield to adjust the vertical temperature gradient can be used for melt growth of typical 4-inch gallium oxide crystals. The growth method is as follows:

[0061] (1) Put the gallium oxide seed crystal into the Pt / Rh alloy crucible bottom, fill in the gallium oxide raw material, wherein the purity of the gallium oxide raw material is 99.999%. Assemble the crucible with the support frame and the support bottom plate, and then use the first lifting mechanism to send the crucible into the growth chamber as a whole;

[0062] (2) After the chamber is evacuated and aerated, dry air is filled into the chamber, and the pressure is maintained at 1 atmosphere (~101 kPa). The second lifting mechanism is controlled so that the heat insulation plate is at the initial position, i.e., the highest point is flush with the lower plane of the growth chamber;

[0063] (3) Slowly increase the power on the heater to heat the heating body to 2147K at a rate of 100-300K / h, and set the crucible rotation speed to 3-10 rpm to ensure uniform heating of the crucible. At this time, the gallium oxide powder in the crucible gradually melts;

[0064] (4) Adjust the heating power of the heater and the initial position of the crucible in the axial direction to make the melt / solid growth interface in the upper region of the seed crystal, and the temperature in this region is 2093K;

[0065] (5) Keep the crucible position unchanged, and gradually increase the height of the heat insulation plate through the second lifting mechanism at a speed consistent with the crystal growth speed, about 0.5-8 mm / h. At the same time, the heater power can be appropriately reduced according to the temperature detection. Due to the heat insulation effect of the heat insulation plate, the temperature of the lower part of the crucible decreases, and a large enough temperature gradient is generated in the area surrounded by the heat insulation plate. At this time, the melt / solid interface rises. In some embodiments, the temperature gradient of the growth interface is 15-25K / cm;

[0066] (6) With the linear rise of the heat insulation plate, the crystal growth interface basically maintains a linear rise, so as to realize the gradual solidification and crystallization of the crystal from bottom to top;

[0067] (7) After the crystal in the crucible is completely solidified, gradually reduce the heater power, and take out the crucible and the crystal after the temperature in the growth chamber decreases to room temperature.

[0068] In order to verify the crystal growth effect, computer simulation technology is used to simulate the thermal field distribution of the crystal growth device and the growth of the gallium oxide crystal. For ease of analysis, the height of the heat insulation plate after entering the growth chamber is defined as H, and the height of the crystal melt / crystal growth interface relative to the starting point of the equiaxial growth region of the crucible is defined as Ah, as shown in Figure 3 .

[0069] Figure 4 It is shown that at the initial stage of growth, the optimal growth interface of the melt in the crucible can be adjusted to the equiaxial growth region by adjusting the heater power. At this time, the heating power of the heater is 8.58kW, Figure 4a shows the morphology of the crystal growth interface (melt / crystal growth interface) in the crucible, and the interface is slightly convex, indicating that the thermal field at this time is suitable for the growth of high-quality gallium oxide single crystal; Figure 4 b shows the thermal field distribution under this condition, and the crystal growth interface 2093K temperature line is consistent with the crystal interface, and the temperature gradient distribution of the crystallized area at the lower part is uniform, and the gradient value is about 10-25K / cm.

[0070] Figures 5-9 The figure shows the change of the best position of the crystal growth surface in the crucible when the height of the heat insulation plate is 100mm, 110mm, 120mm, 130mm and 140mm, and the corresponding thermal field distribution. As can be seen from the figure, with the increase of the height of the heat insulation plate, the crystal growth interface also rises synchronously, and the highest point of the heat insulation plate and the position of the growth surface basically remain consistent. From Figure 5 a, 6a, 7a, 8a, and 9a can be seen that under the condition of different heights of the heat insulation plate, the growth interface of gallium oxide presents a slightly convex morphology, indicating that the thermal field in the crucible regulated by the heat insulation plate can realize the ideal growth interface thermal field distribution, which is conducive to the growth of low-stress and low-defect concentration gallium oxide single crystal. From Figure 5 b, 6b, 7b, 8b and 9b, it can be seen that under the condition of different heights of the heat insulation plate, the temperature gradient distribution of the solidification and crystallization area is uniform, and the temperature gradient value is about 10-25K, which confirms that the heat insulation plate effectively regulates the thermal field distribution in the crucible, and the formed thermal field is conducive to the preparation of high-quality, low-stress gallium oxide crystal.

[0071] Figure 10 The relationship curve between the height △h of the crystal relative to the starting position of the isodiametric growth and the height H of the heat insulation plate is counted, and it can be seen that the increase of the height of the heat insulation plate can basically complete the linear growth of the crystal. The fitting curve also shows that the increase of the height of the heat insulation plate and the increase of the growth thickness of the crystal basically present a linear relationship. Obviously, this is due to the beneficial effect of the present application in adjusting the vertical temperature gradient in the growth chamber by using the heat insulation plate.

[0072] Compared with the growth process of the crucible lifting, the use of the heat insulation plate lifting not only can realize the linear regulation of the thermal field gradient in the vertical direction in the crucible, but also can avoid the vibration caused by the movement of the traditional crucible lowering method, and improve the stability of the crystal growth environment.

[0073] The above examples are only used to further illustrate the crystal growth device and method of the present application for adjusting the vertical temperature gradient by using the heat insulation plate, but the present application is not limited to the examples, and any simple modification, equivalent change and modification made according to the technical essence of the present application to the above examples all fall within the protection scope of the technical scheme of the present application.

Claims

1. A crystal growth apparatus using a heat shield to adjust the vertical temperature gradient, characterized in that: It includes an insulation layer, a heater, an insulation board, a crystal growth crucible, a first lifting mechanism and a second lifting mechanism; the insulation layer encloses a growth chamber, the heater and the crystal growth crucible are located in the growth chamber, the heater is cylindrical and is located between the insulation layer and the side wall of the crystal growth crucible; the first lifting mechanism is used to drive the crystal growth crucible to move up and down; the insulation board is cylindrical, and the second lifting mechanism is used to drive the insulation board to move up and down between the heater and the crystal growth crucible, and the axial temperature distribution gradient in the crucible is adjusted by adjusting the relative height of the insulation board and the heater.

2. The crystal growth device for adjusting the vertical temperature gradient using a heat insulation plate according to claim 1, characterized in that: The thickness of the heat insulation board is 5-30 mm, the thermal conductivity of the material is 0.5-5 W / (m*K), and the surface emissivity is 0.1-0.

5.

3. The crystal growth device for adjusting the vertical temperature gradient using a heat insulation plate according to claim 1, characterized in that: The thermal insulation layer includes a first thermal insulation layer and a second thermal insulation layer. The second thermal insulation layer is enclosed to form a cylindrical growth chamber that is closed from top to bottom. The first thermal insulation layer is enclosed to form a cylindrical shape and is attached to the outside of the second thermal insulation layer.

4. The crystal growth device for adjusting the vertical temperature gradient using a heat insulation plate according to claim 3, characterized in that: The materials of the first thermal insulation layer and the second thermal insulation layer include at least one of zirconia ceramics and alumina ceramics.

5. The crystal growth device for adjusting vertical temperature gradient using a heat insulation plate according to claim 1, characterized in that: The bottom of the growth chamber has an insulation plate lifting channel and a crucible inlet and outlet channel; the crystal growth crucible and the first lifting mechanism are connected by a support structure, and the support structure includes a support frame and a support bottom plate. The support frame is used to fix the crystal growth crucible, and the support bottom plate is connected to the bottom of the support frame and matches the crucible inlet and outlet channel.

6. The crystal growth device for adjusting vertical temperature gradient using a heat insulation plate according to claim 1, characterized in that: The lower part of the crystal growth crucible is used to accommodate seed crystals, and the upper part is used to accommodate growth raw materials. The heater is used to heat the growth raw materials to form a melt, and the melt / crystal growth interface is raised by raising the heat insulation plate.

7. The crystal growth device for adjusting the vertical temperature gradient using a heat insulation plate according to claim 6, characterized in that: The heat insulation effect of the heat insulation board enables the temperature gradient at the melt / crystal growth interface to be controlled within a range of 5 to 30 K / cm.

8. The crystal growth device for adjusting vertical temperature gradient using a heat insulation plate according to claim 1, characterized in that: The invention also includes a driving mechanism for driving the crystal growth crucible to rotate along the central axis.

9. A crystal growth method, characterized in that: Based on the crystal growth device for adjusting the vertical temperature gradient using a heat insulation plate according to any one of claims 1 to 8, the method comprises the following steps: S1. Place the seed crystal into the bottom of the crystal growth crucible, fill it with growth materials, and use a first lifting mechanism to move the crystal growth crucible into the growth chamber; S2. The process gas is filled in the growth chamber, and the heat shield is lowered to the top and flush with the lower interface of the growth chamber by adjusting the second lifting mechanism. The growth material is melted into a melt by the heater. S3. Control the heater power so that the critical temperature is located in the upper region of the seed crystal, and then gradually reduce the heater power so that the melt begins to solidify and crystallize upward from the seed crystal region; S4. From the crystal shoulder stage, the second lifting mechanism gradually adjusts the height of the insulation plate to control the axial temperature gradient in the crystal growth crucible, so that the melt / crystal growth interface rises, and the insulation plate rises at a rate of 0.5 to 8 mm / h; S5. After the crystal growth is completed, gradually reduce the heater power and take it out after the temperature in the growth chamber drops to room temperature.

10. The crystal growth method according to claim 9, wherein: The material of the crystal is Ga2O3, GaAs, InP, GaSb, InAs, CdTe or ZnSe.

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