Device for growing gallium oxide through cold crucible method and czochralski method

Abstract

The invention belongs to the technical field of semiconductor wafer manufacturing, and particularly relates to a device for growing gallium oxide through a cold crucible method and a czochralski method, which comprises a shell, a crucible is arranged in the shell, the crucible comprises a crucible body, communicated cooling cavities are arranged at the bottom and in the side wall of the crucible body, and the cooling cavities are respectively a bottom cooling cavity and a side cooling cavity. The ratio of the size of the side cooling cavity in the radial direction of the crucible to the inner diameter of the crucible is 1: 20-100, and a high-frequency heating device is wound on the outer side of the side wall of the crucible body and connected with a power source. According to the technical scheme, the ratio of the transverse size of the side cooling cavity to the inner diameter of the crucible is found through research, a gallium oxide solid layer can be formed on the inner wall of the crucible body in the production process, the gallium oxide solid layer can completely isolate contact between internal gallium oxide and a crucible body material, and the production efficiency is improved. And the produced gallium oxide crystal is prevented from being polluted.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor wafer manufacturing, and in particular relates to a device for growing gallium oxide by a cold crucible method and a Czochralski method. Background Art

[0002] Gallium oxide has excellent material properties, and its energy saving effect is 3,400 times that of silicon and 10 times that of silicon carbide. Gallium oxide, like silicon, can be grown from liquid crystals by dissolving raw materials, but the current crystallization method uses very expensive metal iridium in the crucible that holds the molten liquid, making it difficult to reduce costs.

[0003] The currently reported growth methods of β-Ga2O3 crystals include the Czochralski method, the guided mold method, the Bridgman method, the floating zone method, etc. Among them, the crucibles used are mostly made of precious metals, mainly iridium and platinum-rhodium alloys. However, because the melting point of gallium oxide is 1793°C, and gallium oxide will volatilize and decompose at high temperatures, there is a problem that the metal gallium is enriched in the melt and corrodes the iridium crucible, affecting the growth process and crystal quality of the crystal; and the platinum-rhodium alloy crucible has a melting point very close to that of gallium oxide, so the temperature control needs to be extremely accurate, and there are problems such as rhodium pollution; in addition, because a large amount of precious metals are required for growth, the cost of crystal growth investment is high, and the cost of crucible corrosion maintenance after growth is very high; the optical floating zone method does not require precious metal crucibles for growing crystals, and its commonly used heating light sources are high-pressure xenon lamps and laser heating; ordinary optical floating zone furnaces are limited by the size of the heating heat source, and the floating zone method can only obtain φ5-10mm crystal rods. Although the crystal quality is good, it cannot meet the industrial needs of large quantities and large sizes.

[0004] Due to the high volatility of raw materials in the Czochralski method, the gallium oxide crystal growth process has gradually evolved from the Czochralski method to the guided mold method with an iridium cover and mold. Both methods require the use of an iridium crucible. Currently, the guided mold method has become the mainstream gallium oxide crystal growth method. However, due to the high cost and loss of iridium crucibles, they will be corroded and worn out after dozens of furnaces of growth, requiring re-smelting and processing. In addition, during the crystal growth process, iridium will form impurities and enter the crystal. The industry has a strong demand for the development of iridium-free methods.

[0005] In April 2022, the Nihon Keizai Shimbun reported that Japan's C&A company used the direct pulling technology of the copper crucible of Tohoku University to grow 2-inch gallium oxide single crystals, which can reduce the cost to 1 / 100 of the guided mold method. Its working principle is to fill the gallium oxide raw material in a crucible with a gap, and the high-frequency coil generates a magnetic field to directly heat the gallium oxide raw material. Then, by further increasing the output of the high-frequency magnetic field, the gallium oxide raw material will melt. At this time, a temperature zone suitable for sintering will be generated between the raw material melt and the water-cooled crucible, where the raw material solidifies, replacing the crucible that holds the melt. The center part is in a molten state, and the sintered state is maintained near the cold crucible wall. Although the direct pulling method reduces costs, it still cannot grow large-size (6-10 inch) gallium oxide single crystals, cannot meet industrial needs, and cannot be produced continuously, and production efficiency is limited. Summary of the invention

[0006] The purpose of the present invention is to provide a device for growing gallium oxide by a cold crucible method and a Czochralski method. Through this device, the production efficiency of gallium oxide single crystals can be improved on the basis of achieving the growth of large-sized gallium oxide single crystals to meet industrial needs.

[0007] To achieve the above objectives, this application is implemented through the following technical solutions:

[0008] A device for growing gallium oxide by a cold crucible method and a Czochralski method, comprising a shell, a crucible is arranged inside the shell, and a lifting device is arranged below the shell, wherein the lifting device passes through the bottom of the shell and is connected to the bottom of the crucible;

[0009] A single crystal silicon lifting assembly comprises a crystal ascending and rotating mechanism, a suspension wire, a seed crystal chuck and a seed crystal, wherein the crystal ascending and rotating mechanism is arranged on the top outer side of a housing, a rotating shaft of the crystal ascending and rotating mechanism passes through the housing and is connected to the upper end of the suspension wire, a lower end of the suspension wire is connected to the seed crystal chuck, and the seed crystal chuck is connected to the seed crystal;

[0010] A vacuum outlet is provided on the side of the shell and connected to the vacuum pump through a pipeline, and a filling gas inlet is provided on the upper side of the shell and connected to the filling gas supply device through a pipeline;

[0011] A diameter control sensor is arranged on the housing and connected to the control system through a wire;

[0012] The crucible comprises a crucible body, wherein the bottom and side walls of the crucible body are provided with connected cooling cavities, namely a bottom cooling cavity and a side cooling cavity, and the bottom cooling cavity and the side cooling cavity are both provided with a cooling water inlet and a cooling water outlet;

[0013] The overall shape of the side cooling chamber is cylindrical, the overall shape of the bottom cooling chamber is disc-shaped, and the ratio of the radial dimension of the side cooling chamber to the inner diameter of the crucible is 1:20-100;

[0014] The cooling water inlet is connected to the cooling water source through a pipeline, and the cooling water outlet is connected to the hot water inlet of the heat exchanger through a pipeline;

[0015] A high-frequency heating device is wound around the outer side of the side wall of the crucible body, and the high-frequency heating device is connected to a power source;

[0016] The high-frequency heating device comprises high-frequency heating coils, and the distances between two adjacent high-frequency heating coils in the same layer are not equal.

[0017] Furthermore, the shell includes a shell body and a neck arranged on the upper part of the shell body, an isolation valve is arranged at the connection between the shell body and the neck, the crystal rising and rotating mechanism is installed on the top outside of the neck, and the seed crystal can pass through the isolation valve.

[0018] Furthermore, the control system is also connected to the crystal rising and rotating mechanism, the lifting device, and the power supply wire respectively.

[0019] Furthermore, a feed port is provided at the top of the shell body, a feed pipe is movably inserted into the feed port and extends into the cavity of the crucible body, and an outer end of the feed pipe is connected to the feed system.

[0020] Furthermore, 2-6 cooling water inlets are provided on the bottom cooling cavity and the side cooling cavity.

[0021] Furthermore, the thickness of the bottom cooling cavity is greater than the thickness of the side cooling cavity, and the ratio of the thickness of the bottom cooling cavity to the thickness of the side cooling cavity is 1.2-2:1.

[0022] Furthermore, the ratio of the radial dimension of the side cooling cavity to the inner diameter of the crucible is 1:30-60.

[0023] Furthermore, the high-frequency heating coil extends from the upper and lower ends to the middle, and the distance between two adjacent coils gradually decreases.

[0024] Furthermore, the cross-section of the coil in the middle 1 / 3-1 / 2 of the axial length of the high-frequency heating coil is rectangular, and the cross-section of the remaining coils is circular.

[0025] The beneficial effects of the present invention are:

[0026] 1. Through research, this technical solution discovered the ratio of the radial size of the side cooling cavity along the crucible to the inner diameter of the crucible, which can form a solid layer of gallium oxide on the inner wall of the crucible body during the production process. The solid layer of gallium oxide can completely isolate the internal gallium oxide from the contact with the crucible body material, thereby preventing the produced gallium oxide crystals from being contaminated.

[0027] 2. This technical solution, through the design of the high-frequency heating coil in the high-frequency heating device, enables corresponding control of the heating direction and heating position, so that the device can be used to grow gallium oxide crystals by the cold crucible method and the vertical pulling method, and can produce 6-10 inch gallium oxide single crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic structural diagram of a device for growing gallium oxide by a cold crucible Czochralski method according to the present invention.

[0029] Description of reference numerals:

[0030] 1. Shell; 2. Crucible; 3. Lifting device; 4. Insulation layer; 5. High-frequency heating device; 6. Control system; 7. Crystal rising and rotating mechanism; 8. Suspension line; 9. Isolation valve; 10. Feed inlet; 11. Shell body; 12. Neck; 13. Diameter control sensor; 14. Seed crystal chuck; 15. Seed crystal; 16. Vacuum outlet; 17. Filling gas inlet. DETAILED DESCRIPTION

[0031] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solution of the present invention, but cannot be construed as limiting the technical solution of the present invention.

[0032] In the technical solution of the present application, the main focus is on the improvement technology of the device for growing gallium oxide using the Czochralski method, and the improvements of the device are mainly in the two or three aspects of the crucible, the high-frequency heating device and the feeding tube that can be used as needed. The other components are the same as those of the existing device for producing gallium oxide using the Czochralski method. Those skilled in the art can make corresponding selections and use them as needed. In this case, the applicant does not provide a detailed description of the other components and assembly relationships.

[0033] like Figure 1 As shown, the present application provides a device for growing gallium oxide by a cold crucible method and a Czochralski method, comprising a shell 1. The shell 1 of the present device is basically the same as the shell of the existing device for producing gallium oxide by the Czochralski method, and both include a shell body and a neck 12 arranged on the upper part of the shell body 11. The outer shape of the shell body of the present application is cylindrical, with a bottom cover at the bottom and an upper cover at the top. In other embodiments of the present application or the existing technology, a structure with a square tube cross-section is also used, which also has a bottom cover at the bottom and an upper cover at the top. The selection of the specific shape is more due to the consideration of the production site, and does not involve technical reasons.

[0034] The neck of the present application is also cylindrical, and the ratio of the outer diameter of the neck to the outer diameter of the shell body is between 1:4-8, which is determined according to actual needs.

[0035] A vacuum outlet 16 is provided at the lower side of the shell body and is connected to a vacuum pump through a pipeline. It is used to evacuate the shell when heating after feeding to avoid impurities in gallium oxide. This technology is also a conventional technology for producing gallium oxide crystals by the Czochralski method. The vacuum pump is connected to the control system by electrical signals.

[0036] A diameter control sensor 13 is provided on the upper end surface of the shell body. The diameter control sensor is electrically connected to the control system 6 for monitoring the crystal diameter during the crystal pulling process. The single crystal silicon pulling assembly includes a crystal rising and rotating mechanism 7, a hanging wire 8, a seed crystal chuck 14 and a seed crystal 15. The crystal rising and rotating mechanism 7 is provided on the top outer side of the shell. The rotating shaft of the crystal rising and rotating mechanism passes through the shell and is connected to the upper end of the hanging wire. The lower end of the hanging wire is connected to the seed crystal chuck, and the seed crystal chuck is connected to the seed crystal. An isolation valve 9 is provided at the connection between the shell body 11 and the neck 12. The seed crystal, the seed crystal chuck and the hanging wire can all pass through the isolation valve. Before the high-frequency heating device heats the gallium oxide raw material to pull the crystal, the isolation valve remains closed. When pulling the crystal, the isolation valve is opened, and the crystal rising and rotating mechanism is started, so that the seed crystal passes through the isolation valve and enters the shell body.

[0037] A filling gas inlet 17 is provided on the upper side of the neck 12 and is connected to a filling gas supply device through a pipeline. This part is a conventional component of an existing CZT device and can be designed by a person skilled in the art according to actual needs.

[0038] The housing also includes a lifting device 3 disposed below the housing body. The lifting device 3 passes through the bottom of the housing and is connected to the bottom of the crucible 2. The lifting device 3 is electrically connected to the control system 6 for moving the crucible up and down in the housing.

[0039] The crucible 2 of the present application includes a crucible body. In the technical solution of the present application, the material of the crucible is copper, that is, a copper crucible is used. The advantage of using a copper crucible is that it has a high thermal conductivity and is easy to process and manufacture. The bottom and side walls of the crucible body of the present application are provided with connected cooling chambers, which are a bottom cooling chamber and a side cooling chamber, respectively. 2-6 cooling water inlets and cooling water outlets are provided on the bottom cooling chamber and the side cooling chamber. In the device of the present application, during the crystal pulling process, the crucible is only lifted accordingly according to the pulling speed, and does not rotate. Therefore, the crucible rotating device is not included in the present device. In other embodiments of the present application, a crucible rotating device can be added. In this case, a cooling water inlet is not provided on the side wall of the crucible, and a cooling water inlet is only provided at the bottom of the crucible body, and it is installed in a sleeve-connected manner with the crucible rotating device to avoid interference with the crucible rotation.

[0040] In the technical solution of the present application, an insulating layer 4 is provided between the inside of the shell 1 and the crucible 2 to prevent the high temperature outside the shell from affecting the production site. This structure is a conventional technology in the field. The specific insulating material used is not required in this application, and the commonly used insulating materials in the field can be used as needed.

[0041] The overall shape of the side cooling cavity of the present application is cylindrical, and the lateral thickness is the same, and the overall shape of the bottom cooling cavity is a circular plate. The ratio of the radial dimension of the side cooling cavity of the present application to the inner diameter of the crucible is 1:20-100. Preferably, the ratio of the radial dimension of the side cooling cavity to the inner diameter of the crucible is 1:30-60. This part of the technical features is the key to the present application. Only within this range can the cold crucible technology be realized. Within this range, the cooling water entering the side of the crucible can partially cool the gallium oxide in the crucible to below the melting point of gallium oxide, forming a gallium oxide crucible shape. If the ratio is too large, the gallium oxide layer formed will be too thick, wasting gallium oxide and reducing the yield of gallium oxide single crystals; if the ratio is too small, the gallium oxide crucible layer cannot be formed.

[0042] In the technical solution of the present application, the thickness of the bottom cooling cavity is greater than the thickness of the side cooling cavity (here, the thickness of the side cooling cavity is measured along the radial direction of the crucible), and the ratio of the thickness of the bottom cooling cavity to the thickness of the side cooling cavity is 1.2-2: 1. If the ratio is too large, cooling water will accumulate in the bottom cooling cavity, and the temperature of the cooling water will be too high, and the gallium oxide crucible layer cannot be realized at this time. If the ratio is too small, the cooling water temperature of the side cooling cavity may be too low, so that the thickness of the gallium oxide crucible layer increases, thereby affecting the yield. In this ratio range of the present application, it can basically ensure that the temperature difference between the cooling water and the molten gallium oxide in the crucible is about 700°C, so as to realize the cold crucible method technology of the present application.

[0043] In other embodiments of the present application, shallow grooves in the upper and lower directions are evenly arranged on the inner wall of the crucible, and the cross-section of the shallow grooves is an isosceles triangle. Such a structural design is to increase the cooling area, further improve the appearance of the cold crucible layer, and avoid the gallium oxide crucible layer from rotating and melting during the rotating crystal pulling process, thereby affecting the quality of the gallium oxide single crystal.

[0044] In the technical solution of the present application, a high-frequency heating device 5 is wound around the outer side of the side wall of the crucible body, and the high-frequency heating device 5 is connected to a power source; the high-frequency heating device includes a high-frequency heating coil, and the distances between two adjacent coils of the same layer of high-frequency heating coils are not equal. In the technical solution of the present application, the number of layers of the high-frequency heating coil is between 1 and 3 layers, which is specifically determined by the inner diameter of the crucible. The larger the inner diameter of the crucible, the higher the number of layers of the high-frequency heating coil required. In this embodiment, one layer of high-frequency heating coil is used as an example for explanation. The high-frequency heating coil of the present application can be used in 2×10 6 Up to 2×10 7 The conversion is specifically realized by the control system. Such frequency modulation control is already a prior art. The specific control module can be obtained by those skilled in the art through commercial channels as needed.

[0045] The high-frequency heating coil of the present application extends from the upper and lower ends to the middle, and the distance between two adjacent coils gradually decreases. The key is that when the cold crucible method is used, the temperature at the middle position of the inner diameter of the crucible increases, while the temperature at other positions is slightly different. In other embodiments of the present application, the cross-section of the coil in the middle 1 / 3-1 / 2 axial length of the high-frequency heating coil is rectangular, and the cross-section of the remaining coils is circular. The technical design of this part takes into account the heating direction of electromagnetic induction heating to facilitate the subsequent realization of the direct pulling method.

[0046] As for other auxiliary components for realizing the operation of this device, they are the same as those of the existing devices and will not be described one by one here.

[0047] In other embodiments of the present application, a feed port 10 is provided at the top of the shell body, a feed pipe is movably inserted into the feed port and extends into the cavity of the crucible body, and the outer end of the feed pipe is connected to the feed system. This structure allows feeding into the crucible in the later stage of crystal pulling, thereby solving the problem that after each straight pulling of the existing straight pulling method, the device needs to be cooled down and then heated up, which not only prolongs the production cycle but also leads to energy waste.

[0048] The working principle of this device is:

[0049] The installation method of this device is the same as that of the existing Czochralski method device. After the components of this device are installed in a conventional manner, a gallium oxide raw material is added to the crucible. The specifications of the gallium oxide raw material refer to the existing technology and are not improved here. Then the vacuum pump is started to evacuate the device. When the vacuum degree in the device reaches the set value, argon mixed with oxygen is filled into the device. Then the high-frequency heating device is started to heat the gallium oxide raw material. When the gallium oxide is heated to melt and kept warm for a set time, the inside of the gallium oxide melt is stabilized. Then cooling water is passed into the crucible. Through corresponding control, the temperature of the part of the gallium oxide close to the inner wall of the copper crucible is reduced to below the melting point of gallium oxide, forming a high-temperature gallium oxide solid layer. At the same time, it is necessary to adjust the high-frequency heating device and increase the conventional heating frequency to the set heating frequency to realize concentrated heating of the gallium oxide in the central part, so as to form a crucible similar to gallium oxide, thereby isolating part of the copper crucible from entering the gallium oxide in the central part, and then the conventional Czochralski method is used to pull gallium oxide crystals.

[0050] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A device for growing gallium oxide by a cold crucible method and a Czochralski method, comprising a shell, a crucible is arranged inside the shell, and a lifting device is arranged below the shell, wherein the lifting device passes through the bottom of the shell and is connected to the bottom of the crucible; A single crystal silicon lifting assembly comprises a crystal ascending and rotating mechanism, a suspension wire, a seed crystal chuck and a seed crystal, wherein the crystal ascending and rotating mechanism is arranged on the top outer side of a housing, a rotating shaft of the crystal ascending and rotating mechanism passes through the housing and is connected to the upper end of the suspension wire, a lower end of the suspension wire is connected to the seed crystal chuck, and the seed crystal chuck is connected to the seed crystal; A vacuum outlet is provided on the side of the shell and connected to the vacuum pump through a pipeline, and a filling gas inlet is provided on the upper side of the shell and connected to the filling gas supply device through a pipeline; A diameter control sensor is arranged on the housing and connected to the control system through a wire; the characteristic is that: The crucible comprises a crucible body, wherein the bottom and side walls of the crucible body are provided with connected cooling cavities, namely a bottom cooling cavity and a side cooling cavity, and the bottom cooling cavity and the side cooling cavity are both provided with a cooling water inlet and a cooling water outlet; The overall shape of the side cooling chamber is cylindrical, the overall shape of the bottom cooling chamber is disc-shaped, and the ratio of the radial dimension of the side cooling chamber to the inner diameter of the crucible is 1:20-100; The cooling water inlet is connected to the cooling water source through a pipeline, and the cooling water outlet is connected to the hot water inlet of the heat exchanger through a pipeline; A high-frequency heating device is wound around the outer side of the side wall of the crucible body, and the high-frequency heating device is connected to a power source; The high-frequency heating device comprises high-frequency heating coils, and the distances between two adjacent high-frequency heating coils in the same layer are not equal.

2. The apparatus for growing gallium oxide by the cold crucible Czochralski method according to claim 1, characterized in that: The shell includes a shell body and a neck arranged on the upper part of the shell body. An isolation valve is arranged at the connection between the shell body and the neck. The crystal rising and rotating mechanism is installed outside the top end of the neck. The seed crystal can pass through the isolation valve.

3. The apparatus for growing gallium oxide by cold crucible Czochralski method according to claim 1, characterized in that: The control system is also connected to the crystal rising and rotating mechanism, the lifting device, and the power supply wire respectively.

4. The apparatus for growing gallium oxide by cold crucible Czochralski method according to claim 1, characterized in that: A feed port is arranged on the top of the shell body, a feed pipe is movably inserted into the feed port and extends into the cavity of the crucible body, and the outer end of the feed pipe is connected to the feed system.

5. The apparatus for growing gallium oxide by cold crucible Czochralski method according to claim 1, characterized in that: 2-6 cooling water inlets are arranged on the bottom cooling cavity and the side cooling cavity.

6. The apparatus for growing gallium oxide by cold crucible Czochralski method according to claim 1, characterized in that: The thickness of the bottom cooling cavity is greater than the thickness of the side cooling cavity, and the ratio of the thickness of the bottom cooling cavity to the thickness of the side cooling cavity is 1.2-2:

1.

7. The apparatus for growing gallium oxide by cold crucible Czochralski method according to claim 6, characterized in that: The ratio of the radial dimension of the side cooling cavity to the inner diameter of the crucible is 1:30-60.

8. The apparatus for growing gallium oxide by cold crucible Czochralski method according to claim 1, characterized in that: The high-frequency heating coil extends from the upper and lower ends to the middle, and the distance between two adjacent coils gradually decreases.

9. The apparatus for growing gallium oxide by the cold crucible Czochralski method according to claim 8, characterized in that: The cross section of the coil in the middle 1 / 3-1 / 2 of the axial length of the high-frequency heating coil is rectangular, and the cross section of the remaining coils is circular.

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