Production device and preparation method of monocrystalline silicon, monocrystalline silicon and insulated gate bipolar transistor

Abstract

The invention relates to the field of crystal preparation, in particular to a production device and a preparation method of monocrystalline silicon, the monocrystalline silicon and an insulated gate bipolar transistor. The apparatus for producing monocrystalline silicon comprises: a crucible for placing and melting a raw material; the heating module is arranged around the crucible and comprises a fixed heater at the upper part and a movable heater at the lower part, and the movable heater moves along the lifting direction of the crystal bar so as to accurately control the crystal growth temperature gradient and the oxygen diffusion transmission mode at different stages of crystal growth; and the magnetic field module is used for applying an asymmetric hook-shaped magnetic field in the crystal growth process so as to inhibit convection of raw materials in the crucible, reduce the oxygen concentration and improve the radial uniformity of oxygen. According to the technical scheme, on the basis of 300mm N-type monocrystalline silicon, under low oxygen (lt; 5ppma), ROGlt; and on the basis of 10%, the target of low potential type defect density can also be achieved, so that the high-quality requirements, including ultralow oxygen content, low defect density and the like, of an IGBT (Insulated Gate Bipolar Translator) on a silicon single crystal substrate are met. The efficient preparation of the ultralow-oxygen N-type silicon single crystal is realized by combining a heater with a novel structure with a CUSP magnetic field technology and matching with crystal pulling process parameter optimization. According to the silicon single crystal prepared by the method, the performance and the reliability of an IGBT (Insulated Gate Bipolar Translator) can be remarkably improved, the production cost is reduced, and the requirements of modern power electronic devices on high-performance silicon-based materials are met.

Description

Technical Field

[0001] The present invention relates to the field of crystal preparation, and in particular to a single crystal silicon production device, a preparation method, single crystal silicon and an insulated gate bipolar transistor. Background Art

[0002] Insulated gate bipolar transistor (IGBT) is a high-efficiency semiconductor device in power electronic equipment. It combines the high input impedance of MOSFET and the low on-state voltage drop of bipolar transistor (BJT). It is widely used in rail transportation, smart grid, aerospace, electric vehicles, wind power generation and other fields. The core material of IGBT is single crystal silicon wafer, and its quality directly affects the performance and reliability of IGBT. IGBT devices have certain requirements on the thickness, crystal orientation, size and resistivity of silicon single crystal substrate materials. In order to improve the withstand voltage of the device, the substrate material is usually required to have a higher resistivity and a complete and defect-free lattice structure. Since the electron mobility is greater than the hole mobility (μ n >μ p ), the conductivity type of the substrate material is usually N-type. For IGBT, it is required to use <100> Crystal orientation of silicon single crystal material.

[0003] During the preparation of IGBT, the oxygen content in silicon wafers needs to be strictly controlled. Too high oxygen content will lead to the formation of oxygen donors and oxygen precipitation in silicon, affecting electrical performance, and causing black core inefficiency and light attenuation. Therefore, reducing oxygen content is one of the main improvement indicators for improving the intrinsic quality of single crystals. The oxygen content required for silicon wafers for IGBT is usually less than 5ppma.

[0004] Most of the existing technologies related to Cusp magnetic fields are concentrated on diameters of 200mm and below. Even some technologies targeting diameters above 300mm only solve partial problems, such as being able to achieve low oxygen or only meet defect requirements. There is no patent report that shows that 300mm N-type single crystal silicon can achieve the goal of low vacancy defect density on the basis of low oxygen (<5ppma) and ROG<10%. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a single crystal silicon production device, preparation method, single crystal silicon and insulated gate bipolar transistor, which can achieve the goal of low vacancy defect density based on 300mm N-type single crystal silicon with low oxygen (<5ppma) and ROG <10%, so as to meet the high quality requirements of IGBT for silicon single crystal substrates, including ultra-low oxygen content, low defect density, etc. By combining a heater with a new structure with CUSP magnetic field technology and optimizing the crystal pulling process parameters, efficient preparation of ultra-low oxygen N-type silicon single crystals can be achieved. The silicon single crystal prepared by the method of the present invention can significantly improve the performance and reliability of IGBT, reduce production costs, and meet the needs of modern power electronic devices for high-performance silicon-based materials.

[0006] In order to solve the above problems, the present invention provides a production device for single crystal silicon, including: a crucible for placing and melting raw materials; a heating module, which is arranged around the crucible and includes a fixed heater at the top and a movable heater at the bottom, and the movable heater moves along the direction of crystal rod pulling to accurately control the crystal growth temperature gradient and the diffusion transmission mode of oxygen at different stages of crystal growth; a magnetic field module, which is used to apply an asymmetric hook-shaped magnetic field during the crystal growth process to suppress the convection of the raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen.

[0007] Optionally, the width range of the fixed heater is 220-320 mm, the width range of the lower heater is 100-250 mm, and the movable range of the lower heater is 200 mm.

[0008] Optionally, the magnetic field strength of the asymmetric hook-shaped magnetic field is 500-2000 Gauss, the position is within the range of 50-0 mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field generator is within the range of 1.5-1.

[0009] In order to solve the above problems, the present invention provides a method for preparing single crystal silicon, comprising the following steps: placing raw materials in a crucible for melting; pulling and growing a single crystal silicon rod, wherein the growth includes necking, shoulder release, shoulder rotation, equal diameter, tailing and cooling; during the pulling and growing process, fixed heating is applied to the upper part of the crucible and movable heating is applied to the lower part, wherein the movable heating is applied along the direction of pulling the crystal rod to accurately control the crystal growth temperature gradient and the diffusion and transmission mode of oxygen at different stages of crystal growth; and an asymmetric hook-shaped magnetic field is applied during the pulling and growing process to suppress convection of the raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen.

[0010] Optionally, the heating area of ​​the fixed heating is 220-320mm, the movable heating area is 100-250mm, and the heating moving range is 200mm.

[0011] Optionally, the magnetic field strength of the asymmetric hook-shaped magnetic field is 500-2000 Gauss, the position is within the range of 100-0 mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field generator is within the range of 1.5-1.

[0012] Optionally, the crystal rotation speed is 5-20 rpm, the crucible rotation speed is 0.5-8 rpm, and the pulling speed is 0.35-0.65 mm / min.

[0013] In order to solve the above problems, the present invention provides a single crystal silicon prepared by any of the above methods, which is a low-oxygen N-type silicon single crystal with an oxygen content of <5ppma, oxygen uniformity of <10%, vacancy defect size of <37nm, and vacancy defect density of <100 particles / cm2.

[0014] In order to solve the above problems, the present invention provides an insulated gate bipolar transistor, which is manufactured using the above single crystal silicon as a substrate.

[0015] The above technical solution adopts the Czochralski method (CZ method) combined with Cusp (sharp magnetic field) to grow N-type silicon single crystals with a diameter of 300mm or even larger than 300mm. Its oxygen level can reach below 5ppma, and the oxygen uniformity (ROG) can be less than 10%. It can also achieve no dislocation and low vacancy defect density (vacancy defect size <37nm, density <100 particles / cm 2 ) goals. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Attached Figure 1 Shown is a schematic structural diagram of a single crystal silicon production device according to a specific embodiment of the present invention.

[0017] Attached Figure 2 Shown is a schematic diagram of the steps of a method for preparing single crystal silicon according to a specific embodiment of the present invention. DETAILED DESCRIPTION

[0018] The following is a detailed description of a single crystal silicon production device, a preparation method, single crystal silicon and a specific implementation of an insulated gate bipolar transistor provided by the present invention in conjunction with the accompanying drawings.

[0019] The technical solution described in this specific embodiment can effectively control the oxygen content in the crystal by introducing a hook-shaped magnetic field in the crystal growth device and combining it with a specific heater structure. Specifically, the introduction of the hook-shaped magnetic field can form a specific magnetic field distribution in the silicon melt during the cooling process, thereby affecting the arrangement of silicon atoms in the crystal and the diffusion behavior of oxygen atoms. At the same time, the adjustment of the heater structure can further optimize the effect of the magnetic field, so that the oxygen content can be accurately controlled.

[0020] Specifically, refer to the attached Figure 1 The structure diagram of the production device of single crystal silicon according to a specific embodiment of the present invention is shown. The production device of single crystal silicon according to this specific embodiment comprises: a crucible 10 , a heating module 20 and a magnetic field module 30 .

[0021] Crucible 10 is used to place and melt raw materials. Crucible 10 includes a quartz crucible and a graphite crucible. A quartz crucible 101 containing high-purity (>99.999999999%) polycrystalline silicon is placed into a graphite crucible 102, and the position of the graphite crucible is adjusted so that the bottom of the heating zone of the heater is at the same level as the liquid surface of the silicon melt, and the material is added multiple times and heated until it melts.

[0022] The heating module 20 is arranged around the crucible 10. In this specific embodiment, the heater designed by numerical simulation and experiment is divided into two layers, including an upper fixed heater 201 and a lower movable heater 202. The movable heater 202 moves along the direction of pulling the crystal rod 11 to accurately control the crystal growth temperature gradient and the diffusion and transmission mode of oxygen at different stages of crystal growth. The lower movable heater 202 can move precisely in the vertical direction; the position of the upper heater is fixed, and the temperature gradient, oxygen diffusion and transmission mode during the crystal growth process are accurately controlled by moving the lower heater, and the crystal growth rate, oxygen content and defects can be adjusted according to needs. The heating zone of the upper heater is located above the silicon melt. At different stages of crystal growth, such as necking, shouldering, equal diameter growth and tailing, the position and power of the lower heater are dynamically adjusted to meet the requirements of the axial temperature gradient of the solid / liquid interface of crystal growth at different stages. Specifically, from necking, shouldering, equal diameter to the final stage, the distance between the mobile heater 202 and the bottom of the crucible is gradually reduced; at the same time, the power of the heater can remain unchanged or change according to the requirements of different crystal oxygen concentrations and defect control; by superimposing or not superimposing the change of power on the above-mentioned heater position movement, the requirements of controlling the oxygen concentration of crystal growth and the axial temperature gradient of the solid / liquid interface at different stages can be met.

[0023] In this specific embodiment, the width of the fixed heater is 220-320 mm, the width of the lower heater is 100-250 mm, the moving range of the lower heater is 200 mm, the power of the fixed heater is 70-80 kW, and the power of the movable heater is 10-20 kW.

[0024] The movable heater 202 is placed at a lower position, which has the advantage of being conducive to crystallization, but has the disadvantage of relatively increasing oxygen precipitation, promoting oxygen to enter the crystal, and increasing the oxygen content in the crystal; the movable heater 202 is placed at an upper position, which has the advantage of reducing oxygen precipitation, the bottom temperature is low, and the melt temperature gradient is higher, which is conducive to the volatilization of oxygen from the free interface and reduces the oxygen content in the crystal. Similarly, increasing the power of the movable heater 202 will relatively promote oxygen precipitation and increase the oxygen content, but is conducive to crystallization, while reducing the power of the movable heater 202 will inhibit oxygen precipitation, but is not conducive to crystallization. But in general, setting a movable heater is significantly helpful in reducing oxygen content, improving oxygen uniformity, and reducing vacancy defect size and vacancy defect density.

[0025] The magnetic field module 30 includes an upper line 301 and a lower coil 302, and currents in opposite directions form a magnetic field. The equal currents are symmetrical magnetic fields, and the unequal currents are asymmetric hook-shaped magnetic fields. The asymmetric hook-shaped magnetic field applied during the crystal growth process can suppress the convection of the raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen. The Cusp magnetic field is applied during the crystal growth process. The Cusp magnetic field is an asymmetric hook-shaped magnetic field, which can effectively suppress the convection in the melt, reduce the oxygen concentration, and improve the radial uniformity of oxygen. The strength and position of the magnetic field need to be precisely controlled to ensure the best oxygen control effect. The magnetic field strength is in the range of 500-2000G, the position is in the range of 100-0mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field is in the range of 1-1.5. Regardless of the magnetic field strength or the magnetic field position, it is to achieve the suppression of the melt by changing the magnetic field strength. The suppression strength is large, which will suppress the precipitation of oxygen, and the flow in the melt will also be suppressed.

[0026] Reference Figure 2 The figure shows a schematic diagram of the steps of a method for preparing single crystal silicon according to a specific embodiment of the present invention. The method comprises the following steps: step S11, placing the raw material in a crucible for melting; step S12, pulling and growing a single crystal silicon rod, during the pulling and growing process, applying fixed heating to the upper part of the crucible, applying movable heating to the lower part, and applying an asymmetric hook-shaped magnetic field during the pulling and growing process.

[0027] In step S11, the raw materials are placed in a crucible for melting. Specifically, the crucible includes a quartz crucible and a graphite crucible. The quartz crucible containing high-purity (>99.999999999%) polycrystalline silicon is placed in the graphite crucible, and the position of the graphite crucible is adjusted so that the bottom of the heating zone of the upper fixed heater is at the same horizontal line as the liquid level of the silicon melt, and the materials are added multiple times and heated until melting.

[0028] In step S12, a single crystal silicon rod is grown by pulling, and the growth includes necking, shoulder release, shoulder rotation, equal diameter, tailing and cooling. During the pulling growth process, fixed heating is applied to the upper part of the crucible, and movable heating is applied to the lower part, and the movable heating is applied along the direction of pulling the crystal rod to accurately control the crystal growth temperature gradient and the diffusion and transmission mode of oxygen at different stages of crystal growth; and an asymmetric hook-shaped magnetic field is applied during the pulling growth process to suppress the convection of the raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen.

[0029] Specifically, in this embodiment, the lower movable heating area moves along the direction of pulling to accurately control the crystal growth temperature gradient and the diffusion and transmission mode of oxygen at different stages of crystal growth. The lower movable heating area can be precisely moved in the vertical direction. By moving the lower heater, the temperature gradient, oxygen diffusion and transmission mode during the crystal growth process can be precisely controlled, and the crystal growth rate, oxygen content and defects can be adjusted according to needs. The position and power of the lower heating area are dynamically adjusted to meet the requirements of the axial temperature gradient of the solid / liquid interface of crystal growth at different stages.

[0030] In this specific embodiment, the height range of the center position of the fixed heating area from the bottom of the crucible is 220-320mm, the height range of the center position of the lower heating area from the bottom of the crucible is 100-250mm, the moving range of the lower heater is 200mm, the fixed heater power is 70-80kW, and the mobile heater power is 10-20kW.

[0031] The advantage of the lower heating position is that it is conducive to crystallization, but the disadvantage is that it will relatively increase oxygen precipitation, promote oxygen to enter the crystal, and increase the oxygen content in the crystal; the advantage of the lower heating position is that it reduces oxygen precipitation, the bottom temperature is low, and the melt temperature gradient is higher, which is conducive to the volatilization of oxygen from the free interface and reduces the oxygen content in the crystal. Similarly, increasing the lower heating power will relatively promote oxygen precipitation and increase the oxygen content, but it is conducive to crystallization. Reducing the lower heating power will inhibit oxygen precipitation, but it is not conducive to crystallization. But in general, setting a lower heater is significantly helpful in reducing oxygen content, improving oxygen uniformity, and reducing vacancy defect size and vacancy defect density.

[0032] The asymmetric hook-shaped magnetic field applied during the crystal growth process can suppress the convection of raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen. The Cusp magnetic field is applied during the crystal growth process. The Cusp magnetic field is an asymmetric hook-shaped magnetic field that can effectively suppress convection in the melt, reduce the oxygen concentration, and improve the radial uniformity of oxygen. The strength and position of the magnetic field need to be precisely controlled to ensure the best oxygen control effect. The magnetic field strength is in the range of 500-2000G, the position is in the range of 100-0mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field is in the range of 1.5-1. Regardless of the magnetic field strength or the magnetic field position, it is to achieve the suppression of the melt by changing the magnetic field strength. A large suppression strength will suppress the precipitation of oxygen, and the flow in the melt will also be suppressed.

[0033] After necking, shoulder release and shoulder rotation, the process of equalizing the diameter is entered. The process parameters of the equalizing the diameter process are also crucial to the oxygen content and defect density, such as crystal rotation speed, crucible rotation speed, furnace pressure and argon flow rate, crystal pulling rate, etc. In this specific implementation: The crystal rotation speed is 5-20 rpm, and preferably 7-11 rpm; The crucible rotation speed is 0.5-8 rpm, and preferably 1-2 rpm; The pulling speed is 0.35-0.65mm / min. The specific pulling speed is determined by the combination of thermal field and other parameters. The furnace pressure is 2-7 kPa, and preferably 2-4 rpm; The argon gas flow rate is 80-200 slm, and preferably 100-160 slm.

[0034] In the finishing stage, the pulling speed and the temperature in the furnace are controlled to reduce dislocations and defects at the tail of the crystal and ensure the quality and integrity of the crystal. After the finishing, the crystal needs to be cooled slowly under controlled conditions to reduce thermal stress and internal stress. By accurately controlling the cooling rate, it can be ensured that the crystal remains stable during the cooling process and the generation of defects is reduced. The cooling rate is 0.5-5mm / min.

[0035] The single crystal silicon prepared by the above method is a low-oxygen N-type silicon single crystal with an oxygen content of <5ppma, an oxygen uniformity of <10%, a vacancy defect size of <37nm, and a vacancy defect density of <100 particles / cm 2 .

[0036] An embodiment of the present invention is given below.

[0037] The upper heater height is 250mm, the lower heater height is 150mm, and the moving range of the lower heater is 200mm.

[0038] Material melting stage: 350kg of material is added, the power of the upper heater is increased to 70kw within 4 hours, the power of the lower heater is increased to 20kw, and the lower heater is placed at the bottom, and the power of the bottom heater is increased to 50kw within 6 hours until all the silicon materials are melted.

[0039] Stabilization: After the material is quenched, turn off the bottom heater and move the lower heater to 20mm below the upper heater. Turn on the magnetic field and set the magnetic field parameters: the magnetic field strength is 2000G, the magnetic field centerline is -80mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field is set to 1.5:1. The stabilization time is about 4-6 hours.

[0040] Equal diameter growth: After necking, shoulder release and shoulder rotation, the process of equal diameter is entered. The position of the heater and magnetic field in the equal diameter process also has a great influence on the oxygen content. After entering the equal diameter stage, the magnetic field moves upward at a rate of 0.5mm / min to -20mm below the liquid surface; the position of the lower heater remains unchanged.

[0041] Finishing and cooling: After the equal diameter is completed, the pulling speed is increased by 10%-20% on the basis of the equal diameter pulling speed, and the heater temperature is gradually increased. The crystal diameter is reduced to within 200mm, and the pulling speed is continued to be increased by 30%-50% until it is closed into a cone. After the finishing is completed, cooling is carried out at a rate of 0.5-5mm / min to reduce thermal stress and internal stress, and reduce the generation of defects.

[0042] Multiple comparative experiments can also be carried out in the above manner. Table 1 shows the comparative results of the test results under multiple experiments. The parameters set in the embodiment are all for the equal diameter stage; the movable position is compared with 0, 100, and 200 mm three positions, and the fixed position is to change the magnetic field position or the crucible speed and crystal speed, etc.

[0043] Table 1 Comparison of test results of multiple experiments

[0044] It can be seen from the above table that after installing the lower heater, compared with the experiment with a single heater, all data have been significantly improved.

[0045] The single crystal silicon prepared by the above method can be applied to the substrate of the insulated gate bipolar transistor.

[0046] The above technical solution: 1. The method of using a hook-shaped magnetic field combined with the adjustment of the heater structure can effectively control the oxygen content in the crystal. Through this adjustment method, the oxygen content of the grown single crystal silicon can be lower, thus meeting the performance requirements of low-oxygen products. This technological breakthrough provides a new solution for the field of semiconductor material growth and helps to improve the purity and performance of semiconductor materials.

[0047] 2. It can not only reduce equipment costs to a certain extent, but also increase the growth rate, making it suitable for large-scale production. Compared with the FZ method, the equipment cost and energy consumption are lower, the growth rate is faster, and it is suitable for large-scale production; compared with the CZ method, the oxygen content of the product is lower, which can meet the performance requirements of low-oxygen products.

[0048] 3. Accurate control of oxygen content in the crystal is achieved.

[0049] The above technical solution not only improves the performance of semiconductor materials, but also provides new directions and ideas for the development of the field of semiconductor material growth.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A production device for single crystal silicon, characterized in that: include: Crucible, used to place and melt raw materials; A heating module, which is arranged around the crucible and includes an upper fixed heater and a lower movable heater, wherein the movable heater moves along the direction of the crystal rod pulling to accurately control the crystal growth temperature gradient and the diffusion and transmission mode of oxygen at different stages of crystal growth; The magnetic field module is used to apply an asymmetric hook-shaped magnetic field during the crystal growth process to suppress the convection of the raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen.

2. The device according to claim 1, characterized in that The width range of the fixed heater is 220-320mm, the width range of the lower heater is 100-250mm, and the movable range of the lower heater is 200mm.

3. The device according to claim 1, characterized in that The fixed heater power is 30-110kW, and the mobile heater power is 0-75kW.

4. The device according to claim 1, characterized in that The magnetic field strength of the asymmetric hook-shaped magnetic field is 500-2000 Gauss, the position is within the range of 100-0 mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field generator is within the range of 1.5-1.

5. A method for preparing single crystal silicon, comprising the following steps: Melt the raw materials in a crucible; Growing a single crystal silicon rod by pulling, wherein the growth includes necking, shoulder release, shoulder rotation, equal diameter, tailing and cooling; Features: During the pulling growth process, fixed heating is applied to the upper part of the crucible, and movable heating is applied to the lower part, wherein the movable heating is applied along the direction of pulling the crystal rod, so as to accurately control the crystal growth temperature gradient and the diffusion and transport mode of oxygen at different stages of crystal growth; and An asymmetric hook-shaped magnetic field is applied during the Czochralski growth process to suppress the convection of the raw materials in the crucible, reduce the oxygen concentration, and improve the radial uniformity of oxygen.

6. The method according to claim 5, characterized in that The fixed heating area is 220-320mm, the mobile heating area is 100-250mm, and the heating moving range is 200mm.

7. The method according to claim 5, characterized in that The magnetic field strength of the asymmetric hook-shaped magnetic field is 500-2000 Gauss, the position is within the range of 100-0 mm below the liquid surface, and the current ratio of the lower / upper coil of the magnetic field generator is within the range of 1.5-1.

8. The method according to claim 5, characterized in that The crystal rotation speed is 5-20rpm, the crucible rotation speed is 0.5-8rpm, and the pulling speed is 0.35-0.65mm / min.

9. A single crystal silicon, characterized in that: Prepared by any method of claims 5 to 8, it is a low-oxygen N-type silicon single crystal with an oxygen content of <5ppma, an oxygen uniformity of <10%, a vacancy defect size of <37nm, and a vacancy defect density of <100 particles / cm 2 .

10. An insulated gate bipolar transistor, characterized in that: The single crystal silicon as claimed in claim 9 is used as a substrate.

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