Method and system for controlling the central oxygen content of a silicon single crystal

Abstract

This paper discloses a method and system for controlling the central oxygen content of a silicon single crystal, which belongs to the semiconductor technology field. The control method of this application includes obtaining parameters for growing a silicon single crystal under a transverse magnetic field and adjusting the central oxygen content of the silicon single crystal based on these parameters, the parameters including the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection, which is melt convection in the center of the crucible, and edge convection, which is melt convection near the crucible walls inside the crucible.

Description

Technical Field

[0001] This application claims priority based on a Chinese patent application filed with the China National Intellectual Property Administration on June 28, 2024, with an application number of 2024108685443 and an invention title of "Method for Controlling the Central Oxygen Content of a Silicon Single Crystal and Its Control System", and incorporates herein by reference all the contents of the above application.

[0002] Embodiments of this application relate to the technical field of semiconductors, but are not limited thereto. Specifically, they relate to a method for controlling the central oxygen content of a silicon single crystal and its control system.

Background Art

[0003] Oxygen is the most important impurity other than dopants in a silicon crystal and has a very significant impact on the quality of a silicon wafer. An appropriate oxygen concentration can increase the mechanical strength of the silicon wafer and enable oxygen precipitates formed in the crystal to play the role of internal gettering. In the growth of conventional silicon single crystals, it has not been possible to effectively analyze which of the fluctuations in the dissolution amount of the inner wall of the quartz crucible, the changes in the melt convection behavior, and the changes in the SiO diffusivity in the gas-liquid two-phase system are the dominant factors for the oxygen content fluctuations. Therefore, the control of the central oxygen content of a silicon single crystal is restricted to a certain extent.

Summary of the Invention

[0004] The following is a summary of the subject matter described in detail in this specification. This summary is not intended to limit the scope of protection of the claims.

[0005] In a first aspect, embodiments of this application provide a method for controlling the central oxygen content of a silicon single crystal. This method for controlling the central oxygen content of a silicon single crystal is as follows: To grow the aforementioned silicon single crystal under a transverse magnetic field, parameters including the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection (melt convection in the center of the crucible) and edge convection (melt convection along the inner wall of the crucible) are obtained. This includes adjusting the central oxygen content of the silicon single crystal based on the aforementioned parameters.

[0006] In a second embodiment, the embodiment of the present application further provides a system for controlling the central oxygen content of a silicon single crystal, which is a system for controlling the central oxygen content of a silicon single crystal. An acquisition module is configured to acquire parameters for growing the aforementioned silicon single crystal under a transverse magnetic field, including the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection, which is melt convection in the center of the crucible, and edge convection, which is melt convection along the inner wall of the crucible. The system includes an adjustment module which is connected to the acquisition module by signal and is configured to adjust the central oxygen content of the silicon single crystal based on the parameters.

[0007] Other embodiments can be understood by reading and understanding the drawings and detailed descriptions. [Effects of the Invention]

[0008] In the embodiment of the present invention, the method for controlling the central oxygen content of a silicon single crystal includes obtaining parameters for growing a silicon single crystal under a transverse magnetic field, including the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection (melt convection in the center of the crucible) and edge convection (melt convection on the inner wall of the crucible), and adjusting the central oxygen content of the silicon single crystal based on these parameters. The magnitude of the central oxygen content of the silicon single crystal is adjusted by four parameters: the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection and edge convection. [Brief explanation of the drawing]

[0009] To more clearly illustrate the technical solutions in the embodiments of the present application, the drawings that need to be used in the embodiments will be briefly described below. However, the drawings in the following description represent only a few embodiments of the present application, and it will be obvious to those skilled in the art that other drawings can be obtained based on these drawings without any creative effort.

[0010] [Figure 1] This is a schematic diagram of the structure of a silicon single crystal growth apparatus in a method for controlling the central oxygen content of a silicon single crystal according to an embodiment of the present invention. [Figure 2] This is a schematic diagram showing a simulation of central and edge convection inside a silicon single crystal growth apparatus in a method for controlling the central oxygen content of a silicon single crystal in an embodiment of the present invention. [Figure 3] This is a schematic columnar diagram of the central oxygen content of the silicon single crystal at the growth interface in the simulation cases of Examples 1 to 5 of the present application. [Figure 4] This is a schematic columnar diagram of the central oxygen content of the silicon single crystal at the growth interface in the test cases of Examples 1 to 5 of the present application. [Figure 5] This is a schematic columnar diagram of the reference value (M value) of the central oxygen content of a silicon single crystal in the simulation case of Examples 1 to 5 of this application. [Figure 6]This is a schematic diagram of a control system for the central oxygen content of a silicon single crystal according to an embodiment of the present invention. [Modes for carrying out the invention]

[0011] The technical solutions in the embodiments of this application will be described clearly and completely below with reference to the drawings of the embodiments of this application, although it is clear that the embodiments described are only a part of the embodiments of this application and not all of them. All other embodiments obtained by a person skilled in the art without creative work based on the embodiments of this application are within the scope of protection of the embodiments of this application.

[0012] In the embodiments of this application, the directions or positional relationships indicated by terms such as "up," "down," "inside," "outside," "vertical," "horizontal," "lateral," and "vertical" are the directions or positional relationships shown in the drawings. These terms are primarily for the purpose of better describing the embodiments of this application and their embodiments, and are not intended to limit the indication that the device, element, or component must have a specific orientation or be configured and operated in a specific orientation.

[0013] Furthermore, some of the above terms may be used to express directions or positional relationships, as well as to express other meanings. For example, the term "above" may, in some cases, be used to express some kind of dependency or connection. A person skilled in the art will be able to understand the specific meaning of these terms in the embodiments of this application depending on the specific situation.

[0014] Furthermore, the terms “installation,” “connection,” and “linking” should be understood broadly. For example, they may be fixed connections, removable connections, or integrated connections; they may be mechanical connections or electrical connections; they may be direct connections, indirect connections via an intermediate medium, or internal communication between two devices, elements, or components. Those skilled in the art will be able to understand the specific meaning of these terms in the embodiments of this application depending on the specific circumstances.

[0015] "Multiple" means two or more unless otherwise specified.

[0016] The primary method for evaluating oxygen is to assess it based on the level of oxygen content at the growth interface center. However, this method can only express the change in oxygen content at the crystal growth interface center in a single way. It cannot effectively analyze whether the change in the amount of solubility in the quartz crucible wall, the change in melt convection, or the change in the degree of diffusion of SiO in the gas-liquid phase is the main influencing factor in the change in oxygen content, thus limiting the improvement of oxygen content. A transverse magnetic field can effectively suppress melt convection and improve oxygen transport in the process of pulling silicon single crystals using the Czochralski method. Furthermore, the magnetic field causes a change in the temperature of the quartz crucible wall, affecting the generation of oxygen in the quartz crucible wall. Additionally, changes in the convection pattern due to the transverse magnetic field can potentially alter the flow of the gas-liquid phase silicon melt, thereby having a certain effect on its SiO volatilization. Oxygen transport exchange also occurs when different convection currents merge, and this is also one of the main factors that lead to changes in oxygen content at the growth interface center.

[0017] In view of the problems of the background art, the embodiments of the present invention provide a method for controlling the central oxygen content of a silicon single crystal in order to solve the technical problem of adjusting the magnitude of the central oxygen content of a silicon single crystal.

[0018] The present application will be described in detail below using specific examples.

[0019] A method for controlling the central oxygen content of a silicon single crystal, the method for controlling the central oxygen content of the silicon single crystal includes obtaining parameters for growing the silicon single crystal 30 under a transverse magnetic field, and adjusting the central oxygen content of the silicon single crystal based on the parameters. The parameters include the oxygen content at the bottom of the crucible, the oxygen content derived from the crucible wall, the oxygen content of the gas-liquid two-phase volatile, and the melt flow rate at the confluence of the central convection 301 and the edge convection 302. The central convection 301 is the melt convection at the center inside the quartz crucible 2, and the edge convection 302 is the melt convection at the inner wall of the quartz crucible 2 (shown in Figure 2). By obtaining the four parameters of the oxygen content at the bottom of the crucible, the oxygen content derived from the crucible wall, the oxygen content of the gas-liquid two-phase volatile, and the melt flow rate at the confluence of the central convection 301 and the edge convection 302, the generation, transport, and exchange of oxygen inside the quartz crucible 2 in the pulling process of the silicon single crystal 30 by the transverse magnetic field CZ method are analyzed. Thereby, the change trend in the oxygen transport process in the silicon melt 3 is analyzed more accurately, and by adjusting the central oxygen content of the silicon single crystal, the product quality of the silicon single crystal 30 is improved. The transverse magnetic field is supplied by a magnetic field generator 1 arranged outside the quartz crucible 2 (shown in Figure 1).

[0020] In some embodiments, the reference value increases with the increase in the melt flow rate and the difference value between the oxygen content derived from the crucible wall and the oxygen content of the gas-liquid two-phase volatile. The reference value represents the central oxygen content of the silicon single crystal. In the manufacturing process of the silicon single crystal, both the difference value between the oxygen content derived from the crucible wall and the oxygen content of the gas-liquid two-phase volatile and the melt flow rate are the main influencing factors. The larger the difference value between the oxygen content derived from the crucible wall and the oxygen content of the gas-liquid two-phase volatile, the larger the reference value, indicating that the central oxygen content of the silicon single crystal is high. The larger the melt flow rate, the larger the reference value, indicating that the central oxygen content of the silicon single crystal is high.

[0021] In some embodiments, the reference value increases with the oxygen content at the bottom of the crucible, the difference value between the oxygen content derived from the crucible wall and the oxygen content of the gas-liquid two-phase volatile oxygen, and the increase in the melt flow rate. In the process of manufacturing a single crystal silicon, the oxygen at the bottom of the crucible reaches the center of the crucible along with the flow of the melt and becomes a part of the oxygen content at the center of the crucible. In the process of the melt flowing, when the oxygen derived from the crucible wall moves to the center of the crucible, the oxygen derived from the crucible wall and the oxygen at the center of the crucible undergo mass exchange in the process of melt convection, forming a part of the gas-liquid two-phase volatile oxygen. The oxygen content derived from the crucible wall is greater than the oxygen content of the gas-liquid two-phase volatile oxygen, and the melt flow rate at the confluence of the central convection and the edge convection has a positive correlation with mass exchange, that is, the greater the melt flow rate, the greater the oxygen content at which mass exchange occurs, so the oxygen content at the center of the single crystal silicon increases. From the above, the reference value has a positive correlation with the oxygen content at the bottom of the crucible, and the product of the difference value between the oxygen content derived from the crucible wall and the oxygen content of the gas-liquid two-phase volatile oxygen and the melt flow rate at the confluence of the central convection and the edge convection has a positive correlation with the reference value.

[0022] Specifically, the greater the oxygen content at the bottom of the crucible, the greater the reference value, which means that the oxygen content moving to the center of the crucible is greater. The greater the oxygen derived from the crucible wall, the smaller the gas-liquid two-phase volatile oxygen, and the greater the melt flow rate, the greater the reference value, which means that the oxygen content moving to the center of the crucible after mass exchange is greater.

[0023] In some embodiments, adjusting the central oxygen content of the single crystal silicon based on parameters includes obtaining a reference value of the central oxygen content of the single crystal silicon based on the oxygen content at the bottom of the crucible, the oxygen content derived from the crucible wall, the oxygen content of the gas-liquid two-phase volatile oxygen, and the melt flow rate, and adjusting the central oxygen content of the single crystal silicon based on the reference value. By using the four parameters to obtain the reference value of the central oxygen content of the single crystal silicon and using the reference value as an intermediate to represent the high or low of the central oxygen content of the single crystal silicon, the central oxygen content of the single crystal silicon can be effectively adjusted, and the product quality of the produced single crystal silicon 30 can be improved.

[0024] In some embodiments, the reference value is obtained by the following formula (1).

[0025] JPEG2026526121000002.jpg18170

[0026] Here, M is the reference value, C(oxy) Central This is the oxygen content at the bottom of the crucible, C(oxy) Edge This is the oxygen content derived from the crucible wall, C(oxy) Free-melt V(cj) is a selected value for the gas-liquid two-phase volatile oxygen content, and V(cj) is the selected value for the molten flow rate. The unit for oxygen content is ppma, and the unit for molten flow rate is m / s.

[0027] The oxygen in the silicon single crystal 30 is mainly composed of three components: the dissolution of the inner wall of the quartz crucible 2, convective transport of the melt, and the volatilization of SiO in the gas-liquid phase. The oxygen content in the silicon melt 3 is mainly due to the dissolution of the inner wall of the quartz crucible 2. The dissolution of the inner wall of the quartz crucible 2 is mainly influenced by two factors: the temperature of the inner wall of the quartz crucible 2 and the laminar flow velocity of the silicon melt 3 on the inner wall side. When the temperature of the inner wall of the quartz crucible 2 increases and the laminar flow velocity of the silicon melt 3 on the inner wall side increases, the dissolution of the inner wall of the quartz crucible 2 is accelerated, and the oxygen content in the silicon melt 3 increases.

[0028] The oxygen dissolved in the silicon melt 3 is affected by melt convection, and the smaller the central vortex, the larger the edge convection 302 becomes. As a result, more oxygen dissolved on the inner wall of the quartz crucible 2 is transported to the gas-liquid phase, where it volatilizes into the gas phase as SiO, reducing the supply of oxygen to the area below the growth interface.

[0029] The melt flow rate below the gas-liquid phase also has a certain effect on oxygen transport and volatilization. The higher the melt flow rate below the gas-liquid phase, the less oxygen is supplied to the growth interface, and the higher the volatilization rate of SiO in the gas-liquid phase, which in turn reduces the oxygen content at the growth interface and throughout the silicon melt 3.

[0030] As shown in Figure 1, the melt convection of the present invention is mainly divided into two parts: central convection 301 and edge convection 302. Central convection 301 exhibits a clockwise flow pattern, and edge convection 302 exhibits a counterclockwise flow pattern. Central convection 301 mainly brings oxygen from the bottom of the quartz crucible 2 into central convection 301, and some of the oxygen is transported into the silicon single crystal 30 together with the flow of the central silicon melt 3. Edge convection 302 brings oxygen originating from the crucible wall into edge convection 302, and at the same time flows along the free surface of the gas-liquid two-phase melt, causing a large amount of gas-liquid two-phase volatile oxygen to volatilize as SiO. Some of the oxygen that has not volatilized is continued to be transported together with edge convection 302 in a counterclockwise flow pattern. Some of the oxygen in the edge convection 302 undergoes solute exchange transport as it flows through the confluence of the central convection 301 and the edge convection 302. Therefore, the greater the melt flow velocity (V(cj)) at the confluence of the central convection 301 and the edge convection 302, the higher the solute exchange transport capacity. This means that the central convection 301 acquires more oxygen and transports that oxygen to the silicon single crystal 30, thereby increasing the oxygen content in the silicon single crystal 30.

[0031] In some embodiments, the oxygen content at the bottom of the crucible is the average value of the oxygen content of the silicon melt 3 in the region 10 mm to 13 mm from the bottom wall of the quartz crucible 2, L1 is the maximum dimension of the orthographic projection in the vertical direction of the selected region of the silicon melt 3, the center of the orthographic projection of the selected region of the silicon melt 3 lies on the central axis of the crucible, and the conditions 60 mm ≤ L1 ≤ 130 mm are satisfied. Specifically, 10 mm to 13 mm may be any of the values ​​10 mm, 11 mm, 12 mm, or 13 mm, or a range value between any two of these values.

[0032] L1 may be any of the following values: 60mm, 70mm, 80mm, 90mm, 100mm, 110mm, 120mm, or 130mm, or it may be a range between any two of these values. The measurement area 5 for the oxygen content at the bottom of the crucible in the silicon melt 3 is the silicon melt 3 in the intermediate layer between 10mm and 13mm from the bottom wall of the crucible, and has the maximum length L1 in the vertical projection plane of this silicon melt 3, and L1 further defines the measurement area 5 for the oxygen content at the bottom of the crucible (indicated by the dotted line with an arrow in Figure 1). By limiting the measurement area for oxygen content, the problem of the measured oxygen content at the bottom of the crucible being inflated due to the saturated dissolved oxygen layer on the inner wall of the quartz crucible 2 can be effectively avoided. In addition, since this area is where the oxygen at the bottom of the crucible effectively flows into the central convection 301, it can effectively represent the oxygen content at the bottom of the crucible.

[0033] In some embodiments, the oxygen content originating from the crucible wall is the average value of the oxygen content of the silicon melt 3 in the region 5 mm to 8 mm from the crucible side wall, and the distance L2 between the top of the selected region of the silicon melt 3 in the vertical direction and the free melt surface 31 satisfies 10 mm ≤ L2 ≤ 15 mm. Specifically, 5 mm to 8 mm may be any of the values ​​5 mm, 6 mm, 7 mm, or 8 mm, or it may be a range value between any two of these values.

[0034] L2 may be any of the following values: 10mm, 11mm, 12mm, 13mm, 14mm, or 15mm, or it may be a range between any two of these values. The crucible's inner wall is composed of the crucible's bottom wall and side walls. In this embodiment, the crucible's side walls refer to the inner wall region of the crucible excluding the bottom wall. The measurement target region 6 for oxygen content derived from the crucible wall (indicated by a dotted line with an arrow in Figure 1) is the silicon melt 3 in the intermediate layer between 5mm and 8mm from the crucible's side walls. Furthermore, a vertical gap L2 is set between the top of the selected region of this silicon melt 3 and the free melt surface 31, and L2 further defines the measurement target region 6 for oxygen content derived from the crucible wall. Since some of the oxygen originating from the crucible wall volatilizes as SiO in the region close to the free melt surface 31, the measurement range of the average value of the oxygen content originating from the crucible wall must satisfy the condition that there is a vertical gap L2 between the top of the selected region of the silicon melt 3 and the free melt surface 31. This reduces the data deviation of the average value of the oxygen content. The free melt surface 31 is the gas-liquid two-phase interface of the silicon melt 3 inside the quartz crucible 2.

[0035] In some embodiments, the gas-liquid two-phase volatile oxygen content is the average value of the oxygen content of the silicon melt 3 in the region from 2 mm to 5 mm from the free melt surface. The measurement area 7 for the gas-liquid two-phase volatile oxygen content (indicated by the dotted line with an arrow in Figure 1) is the silicon melt 3 in the intermediate layer between 2 mm and 5 mm from the free melt surface. Specifically, 2 mm to 5 mm may be any of the values ​​2 mm, 3 mm, 4 mm, or 5 mm, or a range between any two of these values.

[0036] As described above, the average values ​​of the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, and the gas-liquid two-phase volatile oxygen content are all determined by the multi-point measurement averaging method. That is, multiple measurement points are selected within the corresponding region of silicon melt 3, the oxygen content at each point is measured, and then these values ​​are averaged to obtain the average value. Specifically, by selecting a fixed reference point and selecting that point from the processing results after simulation using CGSim (crystal growth modeling software), the calculated oxygen content value at that point can be obtained.

[0037] In some embodiments, the molten flow velocity at the confluence of the central convection 301 and the edge convection 302 is the maximum value of the molten flow velocity at the confluence of the central convection 301 and the edge convection 302.

[0038] In some embodiments, the process further involves simulating the growth of a silicon single crystal 30 using CGSim simulation software before obtaining parameters for growing the silicon single crystal 30 under a transverse magnetic field. The simulation uses a TDR135 furnace base, a 32-inch hot field component, and a 32-inch quartz crucible 2. The conditions for simulating the growth of the silicon single crystal 30 include one or more of the following: raw material input of 400 kg, crystal pulling rotation speed of 8 rmp / min, crucible rotation speed of 0.1 rmp / min, distance d (i.e., 40 mm) between the bottom of the guide cylinder 4 and the free melt surface 31, transverse magnetic field strength of 0.45 T, furnace pressure of 30 Torr, and protective gas flow rate of 130 slpm. Here, the protective gas can be argon gas.

[0039] To obtain different oxygen content, simulations and experiments were conducted by changing the position of the strongest Gaussian surface. Here, in Example 1, the position of the strongest Gaussian surface in the transverse magnetic field, 8, is 50 mm above the free melt surface. In Example 2, the position of the strongest Gaussian surface in the transverse magnetic field, 8, is flush with the free melt surface. In Example 3, the position of the strongest Gaussian surface in the transverse magnetic field, 8, is 50 mm below the free melt surface. In Example 4, the position of the strongest Gaussian surface in the transverse magnetic field, 8, is 100 mm below the free melt surface. In Example 5, the position of the strongest Gaussian surface in the transverse magnetic field, 8, is 180 mm below the free melt surface. As shown in Figure 2, the simulation results for central oxygen content show that Example 2 > Example 5 > Example 3 > Example 1 > Example 4.

[0040] The growth conditions for silicon single crystal 30 used in the experiment are consistent with those of the simulation. By comparing Figure 3 and Figure 4, the experimental results for central oxygen content are consistent with the simulation results for central oxygen content, thus demonstrating the accuracy of the simulation results for central oxygen content.

[0041] Specifically, in Examples 1 to 5, the values ​​of the oxygen content C(oxy)Central at the bottom of the quartz crucible 2, the oxygen content C(oxy)Edge derived from the wall of the quartz crucible 2, the gas-liquid two-phase volatile oxygen content C(oxy)Free-melt, and the melt flow velocity V(cj) at the confluence of the central convection 301 and the edge convection 302 are shown in Table 1 below.

[0042] [Table 1]

[0043] From the table above, the initial dissolved oxygen content of the inner wall of quartz crucible 2 (oxygen content at the bottom of quartz crucible 2 C(oxy )Central +Oxygen content C(oxy) derived from the two walls of the quartz crucible EdgeCalculating the values, we can see that Example 5 > Example 2 > Example 3 > Example 1 > Example 4 (shown in Figure 5). Analysis from the M values ​​shows that V(cj) for Example 2 is clearly larger than that for Example 5, indicating a stronger exchange and transport capacity for solute oxygen at the confluence of central convection 302 and edge convection 302. This allows more oxygen to enter central convection 301, which then transports it into the crystal, resulting in a significantly higher oxygen content at the center of the growth interface, compared to Example 5. Furthermore, the analysis clearly shows that the main reason for the low oxygen content in Examples 3, 4, and 1 is the low oxygen generation and dissolved oxygen content on the inner wall of the quartz crucible 2, which results in a relatively low oxygen content in the entire silicon melt 3, and consequently, a low oxygen content at the center of the growth interface.

[0044] From the comparison between the reference value M and the oxygen content at the center of the growth interface in simulations and experiments, it can be seen that when 6 ≤ M ≤ 14, the smaller the M value, the smaller the oxygen content at the center of the growth interface.

[0045] This embodiment provides a control system for the central oxygen content of a silicon single crystal, as shown in Figure 6. The control system comprises an acquisition module and an adjustment module. The acquisition module is configured to acquire target parameters for growing a silicon single crystal 30 under a transverse magnetic field. These parameters include the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection 301, which is melt convection in the center of the crucible, and edge convection 302, which is melt convection near the crucible walls. The adjustment module is connected to the acquisition module by signal and is configured to adjust the central oxygen content of the silicon single crystal based on the parameters.

[0046] Accordingly, the embodiment of the present application provides a control system for the central oxygen content of a silicon single crystal used to realize the control method of the above embodiment, and thus can have all the technical features and beneficial effects of the control method for the central oxygen content of a silicon single crystal. These will not be explained further here.

[0047] Finally, the following should be added: The above embodiments are for illustrative purposes only and do not limit the technical solutions of the embodiments of the present application. Although the embodiments of the present application have been described in detail with reference to the embodiments described above, those skilled in the art should understand that it is still possible to modify the technical solutions described in the above embodiments or to replace some or all of their technical features with equivalents. Furthermore, such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application. [Explanation of symbols]

[0048] 1-Magnetic field generator, 2-Quartz crucible, 3-Silicon melt, 4-Guide tube, 5-Area for measuring oxygen content at the bottom of the crucible, 6-Area for measuring oxygen content originating from the crucible wall, 7-Area for measuring gas-liquid two-phase volatile oxygen content, 8-Position of the Gauss plane with the strongest transverse magnetic field, 30-Silicon single crystal, 31-Free melt surface, 301-Central convection, 302-Edge convection.

Claims

1. A method for controlling the central oxygen content of a silicon single crystal, To grow the aforementioned silicon single crystal under a transverse magnetic field, parameters including the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection (melt convection in the center of the crucible) and edge convection (melt convection along the inner wall of the crucible) are obtained. This includes adjusting the central oxygen content of the silicon single crystal based on the aforementioned parameters. A method for controlling the central oxygen content of a silicon single crystal.

2. Adjusting the central oxygen content of the silicon single crystal based on the aforementioned parameters is: Based on the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the molten flow rate, a reference value for the central oxygen content of the silicon single crystal is obtained. This includes adjusting the central oxygen content of the silicon single crystal based on the aforementioned reference value, A method for controlling the central oxygen content of a silicon single crystal according to claim 1.

3. The aforementioned reference value is the difference between the oxygen content derived from the crucible wall and the gas-liquid two-phase volatile oxygen content, and increases with increasing molten flow rate. A method for controlling the central oxygen content of a silicon single crystal according to claim 2.

4. The aforementioned reference value is the oxygen content at the bottom of the crucible, the difference between the oxygen content originating from the crucible wall and the gas-liquid two-phase volatile oxygen content, and increases with increasing molten flow rate. A method for controlling the central oxygen content of a silicon single crystal according to claim 2.

5. The aforementioned reference value is calculated by the following formula (1), a method for controlling the central oxygen content of a silicon single crystal according to claim 2. (Here, M is the reference value, C is oxy) Ｃｅｎｔｒａｌ The oxygen content at the bottom of the crucible is C(oxy) Ｅｄｇｅ This is the oxygen content derived from the crucible wall, C(oxy) Ｆｒｅｅ－ｍｅｌｔ (where is the gas-liquid two-phase volatile oxygen content, V(cj) is a selected value of the molten flow rate, the unit of oxygen content is ppma, and the unit of molten flow rate is m / s)

6. The aforementioned reference value is 6 ≤ M ≤ 14, and the smaller the reference value, the lower the central oxygen content of the silicon single crystal. A method for controlling the central oxygen content of a silicon single crystal according to any one of claims 2 to 5.

7. The oxygen content at the bottom of the crucible is the average value of the oxygen content of the molten silicon in the region 10 mm to 13 mm from the bottom wall of the crucible. The maximum dimension of the orthographic projection in the vertical direction of the selected region of the silicon melt is L. １ Therefore, the center of the orthographic projection of the selected region of the silicon melt is located on the central axis of the crucible, and 60 mm ≤ L １ Satisfying ≤ 130 mm, A method for controlling the central oxygen content of a silicon single crystal according to claim 1.

8. The oxygen content originating from the crucible wall is the average value of the oxygen content of the silicon melt in the region 5 mm to 8 mm from the crucible side wall. The vertical distance L between the top of the selected region of the silicon melt and the free melt surface. ２ L is 10 mm ≤ L ２ Satisfying ≤ 15 mm, A method for controlling the central oxygen content of a silicon single crystal according to claim 1.

9. The gas-liquid two-phase volatile oxygen content is the average value of the oxygen content of the silicon melt in the region from 2 mm to 5 mm from the free melt surface. A method for controlling the central oxygen content of a silicon single crystal according to claim 1.

10. The molten flow velocity at the confluence of the central convection and the edge convection is the maximum value of the molten flow velocity at the confluence of the central convection and the edge convection. The method for controlling the central oxygen content of a silicon single crystal according to claim 1.

11. Before obtaining the parameters for growing the aforementioned silicon single crystal in a transverse magnetic field, The method for controlling the central oxygen content of the silicon single crystal is as follows: This further includes simulating the growth of silicon single crystals using simulation software, The conditions for simulating the growth of the silicon single crystal include one or more of the following: raw material input, crystal pulling rotation speed, crucible rotation speed, distance d between the bottom of the guide cylinder and the free melt surface, lateral magnetic field strength, furnace pressure, and protective gas flow rate. A method for controlling the central oxygen content of a silicon single crystal according to claim 1.

12. A system for controlling the central oxygen content of a silicon single crystal, An acquisition module is configured to acquire parameters for growing the aforementioned silicon single crystal under a transverse magnetic field, including the oxygen content at the bottom of the crucible, the oxygen content originating from the crucible walls, the gas-liquid two-phase volatile oxygen content, and the melt flow velocity at the confluence of central convection, which is melt convection in the center of the crucible, and edge convection, which is melt convection along the inner wall of the crucible. The system comprises an adjustment module connected to the acquisition module by a signal and configured to adjust the central oxygen content of the silicon single crystal based on the parameters, A system for controlling the central oxygen content of silicon single crystals.

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