Preparation method of large-size single crystal silicon under different dynamic magnetic fields

Abstract

The present invention relates to the field of semiconductor material preparation, in particular to the field of preparation of large-size single crystal silicon, specifically to a method for preparing large-size single crystal silicon under different dynamic magnetic fields. The steps of the method are: applying a dynamic magnetic field in both the initial growth stage and the stable growth stage to obtain large-size single crystal silicon; wherein, a low-frequency and high-intensity magnetic field with a frequency of 50Hz-100Hz and an intensity of 80G-120G is adopted in the initial growth stage, and a high-frequency and low-intensity dynamic magnetic field with a frequency of 40-60G and a frequency of 500Hz-1kHz is adopted in the stable growth stage. The method optimizes the crystal growth process of single crystal silicon and improves the quality and growth rate of single crystal silicon by accurately controlling the dynamic magnetic field.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor material preparation, in particular to the field of large-size single-crystal silicon preparation, and specifically to a method for preparing large-size single-crystal silicon under different dynamic magnetic fields. Background Art

[0002] As the most basic material in the semiconductor and photovoltaic industries, large-size single crystal silicon is widely used in integrated circuits, solar cells and other fields. Traditional large-size single crystal silicon preparation methods, such as the Czochralski (CZ) method, have problems such as slow crystal growth, more impurities introduced, and crystal defects.

[0003] In recent years, researchers have tried to improve the quality of single crystal silicon by optimizing the preparation process, such as introducing an external magnetic field. In the existing technology, although static magnetic fields can improve crystal growth to a certain extent, how to further improve the quality and growth efficiency of single crystal silicon under the application of different dynamic magnetic fields is still a technical problem that needs to be solved urgently.

[0004] Therefore, further research and development of the production method of single crystal silicon is needed. Summary of the invention

[0005] The purpose of the present invention is to provide a method for preparing large-size single crystal silicon under different dynamic magnetic fields in response to the problems existing in the prior art. The method optimizes the crystal growth process of single crystal silicon and improves the quality and growth rate of single crystal silicon by precise control of the dynamic magnetic field.

[0006] In order to solve the above technical problems, this application adopts the following technical solutions:

[0007] A method for preparing large-size single-crystal silicon under different dynamic magnetic fields refers to applying a dynamic magnetic field in both the initial growth stage and the stable growth stage to obtain large-size single-crystal silicon; wherein a low-frequency and high-intensity magnetic field is used in the initial growth stage, and a high-frequency and low-intensity dynamic magnetic field is used in the stable growth stage.

[0008] Furthermore, in the method for preparing large-size single crystal silicon under different dynamic magnetic fields, the low-frequency and high-intensity magnetic field conditions used in the initial growth stage are: frequency of 50Hz-100Hz, intensity of 80G-120G; the high-frequency and low-intensity dynamic magnetic field conditions used in the stable growth stage are: magnetic field intensity of 40-60G, frequency of 500Hz-1kHz.

[0009] As a preferred method, the method for preparing large-size single crystal silicon under different dynamic magnetic fields comprises the following specific steps:

[0010] 1) Initial growth stage: The initial growth stage is the stage when single crystal silicon begins to form. At this time, the crystal diameter is small, and the growth time needs to be shortened by increasing the crystal growth rate. To this end, the present invention uses a low-frequency and high-intensity magnetic field in this stage.

[0011] 1.1) Melting silicon material: First, silicon particles are placed in a crystal pulling furnace and heated to 1400°C in an argon atmosphere. The silicon material is completely melted at this temperature to form a uniform silicon melt;

[0012] 1.2) Adjusting the magnetic field: In the initial stage, a low-frequency strong magnetic field with a frequency of 50Hz-100Hz (specifically 50Hz, 60Hz, 70Hz, 80Hz, 90Hz, 100Hz, etc.) and an intensity of 80G-120G (specifically 80G, 90G, 100G, 110G, 120G, etc.) is applied; the magnetic field is generated by an electromagnet device, and the direction of the magnetic field is parallel to the crystal growth direction, so that it acts on the surface of the silicon melt, thereby enhancing the thermal convection of silicon and promoting the directional growth of the crystal;

[0013] As a preferred manner, in the initial growth stage of the preparation method of large-size single crystal silicon under different dynamic magnetic fields, the temperature in the furnace is maintained between 1400°C and 1450°C (specifically 1400°C, 1410°C, 1420°C, 1430°C, 1440°C, 1450°C, etc.), and the temperature gradient is controlled by a precise temperature control system to avoid crystal defects caused by temperature fluctuations.

[0014] As a preferred manner, in the initial growth stage of the preparation method of large-size single crystal silicon under different dynamic magnetic fields, the crystal growth rate is controlled at 1.0mm / min-2.0mm / min (specifically 1.0mm / min, 1.1mm / min, 1.2mm / min, 1.3mm / min, 1.4mm / min, 1.5mm / min, 1.6mm / min, 1.7mm / min, 1.8mm / min, 1.9mm / min, 2.0mm / min, etc.) to ensure rapid growth of the crystal.

[0015] 2) Stable growth stage: When the diameter of the single crystal silicon gradually increases to about 100mm, it enters the stable growth stage; at this time, the main goal is to improve the uniformity of the crystal and prevent crystal stress caused by excessive temperature gradient. In this stage, a high-frequency, low-intensity dynamic magnetic field is used to maintain uniform growth of the crystal.

[0016] After entering the stable growth stage, the magnetic field strength is adjusted to 40G-60G (specifically 40G, 45G, 50G, 55G, 60G, etc.), and the frequency is increased to 500Hz-1kHz (specifically 500Hz, 600Hz, 700Hz, 800Hz, 900Hz, 1kHz, etc.). The high-frequency and low-intensity magnetic field can reduce the convection of the melt, suppress the uneven stress inside the crystal, and improve the uniformity of the crystal.

[0017] As a preferred manner, in the method for preparing large-size single crystal silicon under different dynamic magnetic fields, it is necessary to control the oxygen concentration in the atmosphere to be between 5% and 8% during the entire growth process.

[0018] As a preferred manner, in the stable growth stage of the method for preparing large-size single crystal silicon under different dynamic magnetic fields, the temperature is maintained between 1450°C and 1480°C (specifically, 1450°C, 1460°C, 1470°C, 1480°C, etc.). The crystal pulling speed in the stable growth stage is controlled at 0.8mm / min to 1.5mm / min (specifically, 0.8mm / min, 0.9mm / min, 1.0mm / min, 1.1mm / min, 1.2mm / min, 1.3mm / min, 1.4mm / min, 1.5mm / min, etc.) to ensure that the crystal grows stably and uniformly at this stage.

[0019] In addition, the method also includes crystal morphology optimization: that is, by adjusting the atmosphere in the crystal pulling furnace and finely controlling the magnetic field parameters, it can be ensured that the crystal has a smooth appearance, a flat surface, and no obvious cracks or bubbles.

[0020] Another object of the present invention is to protect large-sized single crystal silicon prepared by any of the above methods or a combination of method steps under different dynamic magnetic fields.

[0021] Preferably, the large-sized single crystal silicon obtained above under different dynamic magnetic fields has a maximum diameter of 300 mm and a length of up to 1.5 m.

[0022] Compared with the prior art, this application has the following beneficial effects:

[0023] The technical solution of the present invention can significantly improve the production efficiency of single crystal silicon and ensure the quality of the crystal. Compared with the traditional Czochralski method, the defect density of the crystal of the present invention is reduced by about 66%. In the production of large-size single crystal silicon, the use of dynamic magnetic field control has significantly improved the uniformity and electrical properties of the crystal, and the resistivity has been reduced from the traditional 0.006Ω·cm to 0.0038Ω·cm; the maximum diameter of the crystal reaches 300mm and the length can reach 1.5m. DETAILED DESCRIPTION

[0024] The technical solutions in some embodiments of the present application are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments provided by the present application, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present application.

[0025] In the following, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features.

[0026] When describing some embodiments, the expression "A and / or B" may be used. It is easy to understand that "A and / or B" includes the following three combinations: only A, only B, and a combination of A and B.

[0027] When describing some embodiments, the expressions "at least one of A, B and C" and "at least one of A, B or C" may be used, both of which have the same meaning and include the following combinations of A, B and C: A only, B only, C only, the combination of A and B, the combination of A and C, the combination of B and C, and the combination of A, B and C.

[0028] Unless otherwise specified, the materials and devices used in the following examples can be purchased through conventional commercial channels or are prior art.

[0029] Czochralski crystal pulling furnace (CZ-1200A):

[0030] The crystal pulling furnace is the core equipment for melting and growing single crystal silicon. Equipped with a high-precision temperature control system, it can maintain the temperature in the furnace stable, with a control error within ±1°C. The equipment has a large capacity and can melt up to 50kg of silicon material, supporting the pulling of single crystal silicon with a maximum diameter of 300mm. The furnace body is made of high-temperature resistant alloy material and can operate stably for a long time under high temperature conditions.

[0031] Electromagnet device (EM-2000D):

[0032] The electromagnet device consists of 4 adjustable magnetic field sources, which can generate a dynamic magnetic field with an intensity of 50G to 150G and a frequency range of 10Hz to 1kHz. The magnetic field strength and frequency of each electromagnet can be adjusted independently, and the configuration of the magnetic field can be adjusted in real time at different crystal growth stages. Through the computer control system, the operator can accurately set the magnetic field strength, frequency and waveform (sine wave or square wave) required for each stage.

[0033] Temperature Control System (TC-4000):

[0034] The temperature control system is equipped with a multi-channel sensor that can monitor and adjust the temperature in the furnace in real time. The system's temperature control accuracy is ±0.5°C, ensuring that temperature fluctuations are minimized during the growth process. The temperature control system is automatically controlled through a feedback loop with the furnace and crystal pulling device to maintain temperature stability during the growth process.

[0035] Vacuum system (VS-100):

[0036] In order to control the atmosphere in the furnace, avoid impurity contamination and improve the quality of silicon crystals, an efficient vacuum system is equipped. The vacuum system can pump the gas in the furnace to a low pressure state, and at the same time, by adjusting the gas flow, accurately control the concentration of oxygen in the atmosphere. The oxygen concentration can be maintained between 5% and 8% to prevent oxidation of silicon during the melting process.

[0037] Gas flow control device (GA-600):

[0038] The present invention uses a gas flow control device to adjust the flow of argon and nitrogen in the furnace to ensure a stable atmosphere without introducing too many impurities. Argon and nitrogen as protective gases can effectively reduce the oxygen content of the gas in the furnace and reduce the oxidation reaction of the silicon material.

[0039] The above devices are all existing technologies, and the conditions involved can be achieved by existing technologies.

[0040] Comparative Example 1:

[0041] Prepare silicon raw materials: Select silicon particles with a purity of 99.99% (3-5 mm in diameter) and place them in a crystal pulling furnace.

[0042] Heating and melting: Heating to 1450°C in an argon atmosphere, the silicon material is completely melted at this temperature to form a uniform silicon melt. The oxygen concentration in the furnace atmosphere is controlled at 6% to prevent oxidation of silicon during the melting process.

[0043] Crystal growth: Fix the seed crystal with a certain crystal phase on the seed crystal connecting rod, and then gradually lower the position of the seed crystal. When the seed crystal stays at a distance of 10mm from the liquid surface for a period of time, the temperature of the seed crystal is close to the temperature of the molten silicon to reduce the thermal shock caused by the temperature difference; lower the seed crystal connecting rod to allow the seed crystal to slowly enter the molten silicon. The seed crystal first melts a part and forms a solid-liquid interface with the molten silicon: then, the seed crystal gradually rises, and the silicon crystal connected to the seed crystal leaves the solution and becomes the same body.

[0044] Cooling and solidification: When the crystal rod grows to the desired size, stop lifting and rotating to allow the silicon melt to cool and solidify.

[0045] Embodiment 1:

[0046] Initial growth stage:

[0047] The initial growth stage is the stage when the single crystal silicon begins to form. At this time, the crystal diameter is small, and the growth time needs to be shortened by increasing the crystal growth rate. For this reason, the present invention adopts a low-frequency and high-intensity magnetic field in this stage.

[0048] 1. Melting silicon material:

[0049] First, silicon particles with a purity of 99.9999% (3-5mm in diameter) are placed in a Czochralski crystal pulling furnace (CZ-1200A). They are heated to 1400°C in an argon atmosphere, at which the silicon material is completely melted to form a uniform silicon melt. The oxygen concentration in the furnace atmosphere is controlled at 6% to prevent oxidation of silicon during the melting process.

[0050] 2. Adjust the magnetic field:

[0051] In the initial growth stage, a low-frequency strong magnetic field with a frequency of 50 Hz and an intensity of 100 G is applied. The magnetic field is generated by an electromagnet device (EM-2000D), and its direction is parallel to the crystal growth direction, acting on the molten silicon surface, thereby enhancing the thermal convection of silicon and promoting the directional growth of the crystal.

[0052] 3. Control the temperature:

[0053] The temperature in the furnace is maintained at 1425°C, and the temperature gradient is controlled by a precise temperature control system (TC-4000) to avoid crystal defects caused by temperature fluctuations. In the initial stage, the temperature gradient is strictly controlled within ±0.5°C to ensure the uniformity of the silicon melt.

[0054] 4. Crystal growth rate control:

[0055] In the initial growth stage, the crystal growth rate is 2.0mm / min to ensure rapid growth of the crystal while maintaining crystal quality. By precisely controlling the pulling force and temperature of the crystal pulling furnace, it is ensured that the crystal does not deform or crack during the growth process.

[0056] Stable growth stage:

[0057] When the diameter of the single crystal silicon gradually increases to about 100mm, it enters the stable growth stage. At this time, the main goal is to improve the uniformity of the crystal and prevent crystal stress caused by excessive temperature gradient. In this stage, a high-frequency, low-intensity dynamic magnetic field is used to maintain uniform growth of the crystal.

[0058] 1. Adjust the magnetic field:

[0059] After entering the stable growth stage, the magnetic field strength is 50G and the frequency is 800Hz. The high-frequency and low-intensity magnetic field can reduce the convection of the melt, suppress the uneven stress inside the crystal, and improve the uniformity of the crystal.

[0060] 2. Control the temperature and crystal pulling rate:

[0061] The temperature in the stable growth stage is maintained at 1475°C, and the crystal pulling speed is controlled at 1.2mm / min to ensure that the crystal grows stably and evenly in this stage. Through the precise control of temperature and crystal pulling speed, the crystal is guaranteed to have good mechanical and electrical properties throughout the stable growth stage.

[0062] 3. Crystal morphology optimization:

[0063] By adjusting the atmosphere in the crystal pulling furnace, the argon flow rate in the atmosphere is guaranteed to be 50L / min to ensure that there are no impurities or bubbles in the melt. The crystal surface is flat and there are no obvious cracks or bubbles, ensuring that the large-size single crystal silicon finally produced has excellent optoelectronic properties.

[0064] In order to determine the effects of applying different magnetic field strengths and frequencies on the production of single crystal silicon in the initial growth stage and the stable growth stage, the following experiment was carried out under the same conditions as in Example 1. The specific parameters changed and the results are shown in Table 1:

[0065] Table 1:

[0066]

[0067] It can be seen from the above table that the use of a low-frequency, high-intensity magnetic field in the initial growth stage and a high-frequency, low-intensity dynamic magnetic field in the stable growth stage can maintain the uniform growth of the crystal. The surface of the prepared crystal is smooth without obvious cracks or bubbles, and the large-size single crystal silicon finally produced has excellent optoelectronic properties.

[0068] The above basic examples of the present invention and their further selected examples can be freely combined to form multiple embodiments, all of which are embodiments that can be adopted and claimed by the present invention. In the scheme of the present invention, each selected example can be arbitrarily combined with any other basic example and selected example. Those skilled in the art will know that there are many combinations.

[0069] The above embodiments are only preferred solutions of the present invention. The implementation methods and protection scope of the present invention are not limited to the above embodiments. All designs and technical solutions using the ideas of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some changes without departing from the design principles of the present invention should also be regarded as the protection scope of the present invention. The present invention extends to any new features or any new combination disclosed in this specification, as well as any new method or process steps or any new combination disclosed.

Claims

1. A method for preparing large-size single crystal silicon under different dynamic magnetic fields, characterized in that : Dynamic magnetic fields are applied in both the initial growth stage and the stable growth stage to obtain large-sized single crystal silicon; wherein, a low-frequency and high-intensity magnetic field is used in the initial growth stage, and a high-frequency and low-intensity dynamic magnetic field is used in the stable growth stage.

2. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 1, characterized in that: The low-frequency and high-intensity magnetic field conditions used in the initial growth stage are: frequency 50Hz-100 Hz, intensity 80G-120G; the high-frequency and low-intensity dynamic magnetic field conditions used in the stable growth stage are: magnetic field intensity 40-60G, frequency 500Hz-1kHz.

3. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 1 or 2, characterized in that The specific steps include: 1) Initial growth stage: a) Melting silicon material: First, silicon particles are placed in a crystal pulling furnace and heated to 1400°C in an argon atmosphere to form a uniform silicon melt after complete melting; b) Adjusting the magnetic field: applying a low-frequency strong magnetic field with a frequency of 50 Hz-100 Hz and an intensity of 80G-120G; the direction of the magnetic field is parallel to the crystal growth direction, so that it acts on the surface of the silicon melt, thereby enhancing the thermal convection of silicon and promoting the directional growth of the crystal; 2) Stable growth stage: When the diameter of the single crystal silicon gradually increases to about 100mm, it enters the stable growth stage; after entering the stable growth stage, the magnetic field strength is adjusted to 40G-60G, and the frequency is increased to 500Hz-1kHz.

4. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 3, characterized in that: During the entire growth process, the oxygen concentration in the atmosphere was controlled between 5% and 8%.

5. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 3, characterized in that: During the initial growth stage, the furnace temperature is maintained between 1400°C and 1450°C.

6. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 3, characterized in that: In the initial growth stage, the crystal growth rate is controlled at 1.0 mm / min-2.0 mm / min.

7. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 3, characterized in that: The temperature during the stable growth phase was maintained between 1450°C and 1480°C.

8. The method for preparing large-size single crystal silicon under different dynamic magnetic fields according to claim 3, characterized in that: The crystal pulling speed in the stable growth stage is controlled at 0.8 mm / min to 1.5 mm / min.

9. Large-sized single crystal silicon prepared by the method as described in any one of claims 1 to 8 under different dynamic magnetic fields.

10. The large-size single crystal silicon under different dynamic magnetic fields according to claim 9, characterized in that: The maximum diameter of a single-crystal silicon crystal reaches 300 mm and the length can reach 1.5 m.

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