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

Abstract

The present disclosure belongs to the technical field of semiconductors, and discloses a method and system for controlling the central oxygen content of a silicon single crystal. The control method in the present application comprises: acquiring parameters for growing a silicon single crystal under a transverse magnetic field, wherein the parameters comprise the content of oxygen at the bottom of a crucible, the content of oxygen generated by the wall of the crucible, the content of oxygen volatilized at a gas phase and a liquid phase, and the melt flow velocity at the junction of central convection and edge convection, the central convection being melt convection at the center in the crucible, and the edge convection being melt convection close to the wall of the crucible in the crucible; and adjusting the central oxygen content of the silicon single crystal on the basis of the parameters.

Description

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

[0001] The present application claims priority to the Chinese patent application No. 2024108685443, filed on June 28, 2024, and entitled "Method and system for controlling central oxygen content of silicon single crystal", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] Embodiments of the present application relate to, but are not limited to, the technical field of semiconductor technology, and specifically relate to a method and system for controlling central oxygen content of silicon single crystal. BACKGROUND

[0003] Oxygen is the most important impurity in silicon crystal besides dopants, which has a great impact on the quality of silicon wafers. Appropriate oxygen concentration can increase the mechanical strength of silicon wafers, and the oxygen precipitates generated in the crystal can play the role of internal gettering. The existing growth of silicon single crystal cannot effectively analyze which of the changes in the amount of dissolved quartz crucible inner wall, the changes in melt convection and the changes in the degree of SiO diffusion in the gas-liquid two-phase are the main influencing factors of the change in oxygen content, so it has certain limitations for controlling the central oxygen content of silicon single crystal.

[0004] SUMMARY

[0005] The following is a summary of the subject matter of the detailed description herein. This summary is not intended to limit the scope of the claims.

[0006] In a first aspect, the embodiments of the present application provide a method for controlling central oxygen content of silicon single crystal, comprising:

[0007] obtaining parameters of growing the silicon single crystal under a transverse magnetic field, the parameters comprising: oxygen content at the bottom of the crucible, oxygen content generated by the crucible wall, volatile oxygen content in the gas-liquid two-phase, and melt flow rate at the intersection of the central convection and the edge convection, the central convection being the melt convection at the center of the crucible, and the edge convection being the melt convection at the inner wall of the crucible;

[0008] adjusting the central oxygen content of the silicon single crystal according to the parameters.

[0009] In a second aspect, the embodiments of the present application also provide a system for controlling central oxygen content of silicon single crystal, comprising:

[0010] an obtaining module configured to obtain parameters of growing the silicon single crystal under a transverse magnetic field, the parameters comprising: oxygen content at the bottom of the crucible, oxygen content generated by the crucible wall, volatile oxygen content in the gas-liquid two-phase, and melt flow rate at the intersection of the central convection and the edge convection, the central convection being the melt convection at the center of the crucible, and the edge convection being the melt convection at the inner wall of the crucible;

[0011] an adjusting module, which is connected with the acquiring module, and is configured to adjust the central oxygen content of the silicon single crystal according to the parameters.

[0012] Other aspects can become apparent from the following detailed description, when considered in conjunction with the accompanying drawings and the detailed description. Advantageous Effects

[0013] In the embodiments of the present application, the method for controlling the central oxygen content of a silicon single crystal comprises: acquiring parameters of a silicon single crystal grown under a transverse magnetic field, the parameters including: oxygen content at the bottom of a crucible, oxygen content generated by the wall of the crucible, oxygen content of a gas-liquid two-phase volatilization, and melt flow rate at the intersection of a central convection and an edge convection, the central convection being a melt convection at the center of the crucible, and the edge convection being a melt convection at the inner wall of the crucible; and adjusting the central oxygen content of the silicon single crystal according to the parameters. The four parameters of the oxygen content at the bottom of the crucible, the oxygen content generated by the wall of the crucible, the oxygen content of the gas-liquid two-phase volatilization, and the melt flow rate at the intersection of the central convection and the edge convection are used to adjust the size of the central oxygen content of the silicon single crystal. BRIEF DESCRIPTION OF DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0015] FIG. 1 is a structural schematic diagram of a silicon single crystal growth device in a method for controlling the central oxygen content of a silicon single crystal according to an embodiment of the present application;

[0016] FIG. 2 is a schematic diagram of simulating the central convection and the edge convection in the internal of a silicon single crystal growth device in a method for controlling the central oxygen content of a silicon single crystal according to an embodiment of the present application;

[0017] FIG. 3 is a columnar schematic diagram of the central oxygen content of a silicon single crystal at a growth interface under simulation in Embodiments 1 to 5 of the present application;

[0018] FIG. 4 is a columnar schematic diagram of the central oxygen content of a silicon single crystal at a growth interface under test in Embodiments 1 to 5 of the present application;

[0019] FIG. 5 is a columnar schematic diagram of the reference value (M value) of the central oxygen content of a silicon single crystal under simulation in Embodiments 1 to 5 of the present application;

[0020] FIG. 6 is a schematic diagram of a system for controlling the central oxygen content of a silicon single crystal according to an embodiment of the present application.

[0021] Explanation of reference numerals: 1 - magnetic field generator; 2 - quartz crucible; 3 - silicon melt; 4 - flow guide; 5 - range of values of oxygen content at the bottom of the crucible; 6 - range of values of oxygen content generated by the crucible wall; 7 - range of values of volatile oxygen content in the gas-liquid two-phase; 8 - position of the strongest Gauss surface of the transverse magnetic field; 30 - silicon single crystal; 31 - free melt surface; 301 - central convection; 302 - edge convection.

[0022] Embodiments of the present application

[0023] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the embodiments of the present application.

[0024] In the embodiments of the present application, the orientations or positional relationships indicated by the terms "top", "bottom", "inner", "outer", "vertical", "horizontal", "lateral", "longitudinal" and the like are based on the orientations or positional relationships shown in the drawings. These terms are mainly used to better describe the embodiments of the present application and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0025] In addition, in addition to being used to indicate the orientations or positional relationships, the above-mentioned terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. Those skilled in the art can understand the specific meanings of these terms in the embodiments of the present application according to the specific circumstances.

[0026] In addition, the terms "set", "connected", "connected" should be broadly understood. For example, it can be fixedly connected, detachably connected, or integrally constructed; it can be mechanically connected, or electrically connected; it can be directly connected, or indirectly connected through an intermediate medium, or internal communication between two devices, elements or components. Those skilled in the art can understand the specific meanings of the above-mentioned terms in the embodiments of the present application according to the specific circumstances.

[0027] Unless otherwise specified, the meaning of "a plurality of" is two or more.

[0028] The method for evaluating oxygen is mainly to evaluate the oxygen content at the growth interface center, which can only single express the change of the oxygen content at the growth interface center of the crystal, but cannot effectively analyze which one of the change of the dissolution amount of the inner wall of the quartz crucible, the change of the melt convection and the change of the diffusion degree of the SiO in the gas-liquid two-phase is the main influencing factor, so it has certain limitations for improving the oxygen content. The transverse magnetic field can effectively suppress the melt convection when the silicon single crystal is drawn by the CZ method (Czochralski), so as to improve the oxygen transport; at the same time, the magnetic field will cause the change of the temperature of the inner wall of the quartz crucible, thereby affecting the generation of oxygen at the inner wall of the quartz crucible. Due to the change of the convection form caused by the transverse magnetic field, the flow of the silicon melt flowing through the gas-liquid two-phase may also change, so it will also have a certain influence on the volatilization of SiO. Different convections will also cause the behavior of oxygen transport exchange when they intersect, which is also a main reason for the change of the oxygen content at the center of the growth interface.

[0029] In view of the problems in the background art, the embodiments of the present application provide a silicon single crystal center oxygen content control method to solve the technical problem of how to adjust the size of the silicon single crystal center oxygen content.

[0030] The present application will be described in detail below through specific embodiments:

[0031] A silicon single crystal center oxygen content control method, comprising: obtaining parameters of growing a silicon single crystal 30 under a transverse magnetic field, the parameters including: oxygen content at the bottom of the crucible, oxygen content generated by the crucible wall, volatile oxygen content in the gas-liquid two-phase, melt flow rate at the intersection of the center convection 301 and the edge convection 302, the center convection 301 being the melt convection at the center of the quartz crucible 2, and the edge convection 302 being the melt convection at the inner wall of the quartz crucible 2 (as shown in FIG. 2); and adjusting the silicon single crystal center oxygen content according to the parameters. By obtaining the four parameters of the oxygen content at the bottom of the crucible, the oxygen content generated by the crucible wall, the volatile oxygen content in the gas-liquid two-phase and the melt flow rate at the intersection of the center convection 301 and the edge convection 302, the generation, transport and exchange of oxygen in the quartz crucible 2 during the process of drawing the silicon single crystal 30 by the transverse magnetic field CZ method are analyzed, so as to more accurately analyze the change trend of the oxygen in the silicon melt 3 in the transport process, thereby adjusting the silicon single crystal center oxygen content to improve the product quality of the prepared silicon single crystal 30. It should be understood that the transverse magnetic field is provided by a magnetic field generator 1 arranged outside the quartz crucible 2 (as shown in FIG. 1).

[0032] In some embodiments, the reference value increases with the increase of the difference between the oxygen content generated by the crucible wall and the oxygen content of the gas-liquid two-phase volatilization, and the increase of the melt flow rate. It needs to be understood that the central oxygen content of the silicon single crystal is represented by the reference value, and in the process of preparing the silicon single crystal, the two main influencing factors are the difference between the oxygen content generated by the crucible wall and the oxygen content of the gas-liquid two-phase volatilization, and the melt flow rate. The greater the difference between the oxygen content generated by the crucible wall and the oxygen content of the gas-liquid two-phase volatilization, the greater the reference value, which means the higher the central oxygen content of the silicon single crystal. The greater the melt flow rate, the greater the reference value, which means the higher the central oxygen content of the silicon single crystal.

[0033] In some embodiments, the reference value increases with the increase of the oxygen content of the crucible bottom, the difference between the oxygen content generated by the crucible wall and the oxygen content of the gas-liquid two-phase volatilization, and the melt flow rate. It needs to be understood that in the process of preparing the silicon single crystal, the oxygen at the bottom of the crucible will reach the center of the crucible with the flow of the melt, becoming part of the central oxygen content of the crucible; in the process of melt flow, the oxygen generated by the crucible wall exchanges with the oxygen at the center of the crucible in the process of melt convection, forming part of the gas-liquid two-phase volatilization oxygen. Since the oxygen content generated by the crucible wall is greater than the oxygen content of the gas-liquid two-phase volatilization, the melt flow rate at the confluence of the central convection and the edge convection is positively correlated with the lipid exchange, that is, the greater the melt flow rate, the more the oxygen content of the lipid exchange, and the more the central oxygen content of the silicon single crystal. In summary, the reference value is positively correlated with the oxygen content of the crucible bottom, and the product of the difference between the oxygen content generated by the crucible wall and the oxygen content of the gas-liquid two-phase volatilization and the melt flow rate at the confluence of the central convection and the edge convection is positively correlated with the reference value.

[0034] Specifically, the more the oxygen content at the bottom of the crucible, the greater the reference value, which means the more the oxygen content entering the center of the crucible; the more the oxygen generated by the crucible wall, the less the oxygen volatilized by the gas-liquid two-phase, and the greater the melt flow rate, the greater the reference value, which means the more the oxygen content entering the center of the crucible after lipid exchange.

[0035] In some embodiments, the central oxygen content of the silicon single crystal is adjusted according to the parameters, including: obtaining a reference value of the central oxygen content of the silicon single crystal according to the oxygen content of the crucible bottom, the oxygen content generated by the crucible wall, the oxygen content of the gas-liquid two-phase volatilization, and the melt flow rate; and adjusting the central oxygen content of the silicon single crystal according to the reference value. The reference value of the central oxygen content of the silicon single crystal is obtained according to the four parameters, and the reference value is used as an intermediate to represent the high and low of the central oxygen content of the silicon single crystal, so as to effectively adjust the central oxygen content of the silicon single crystal and improve the product quality of the silicon single crystal 30.

[0036] In some embodiments, the reference value is obtained by the following formula:

[0037] In the formula, M is the reference value; C(oxy) is the oxygen content of the gas-liquid two-phase volatilization; and V is the melt flow rate. CentralC(oxy) is the oxygen content of the bottom of the crucible; C(oxy) Edge C(oxy) is the oxygen content of the wall of the crucible; C(oxy) Free-melt V(cj) is the oxygen content of the gas-liquid two-phase volatile; V(cj) is the value of the melt flow rate, the oxygen content unit is ppma, and the melt flow rate unit is m / s.

[0038] It needs to be understood that the oxygen in the silicon single crystal 30 is mainly composed of three parts: the dissolution of the inner wall of the quartz crucible 2, the convection of the melt, and the volatilization of SiO in the gas-liquid two-phase. The oxygen content in the silicon melt 3 mainly comes from the dissolution of the inner wall of the quartz crucible 2, and the dissolution of the inner wall of the quartz crucible 2 is mainly affected by 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, the laminar flow velocity of the silicon melt 3 on the inner wall side increases, which will accelerate the dissolution of the inner wall of the quartz crucible 2, thereby increasing the oxygen content in the silicon melt 3.

[0039] The oxygen dissolved in the silicon melt 3 is also affected by the convection of the melt. The smaller the central vortex, the larger the edge convection 302, which means that more oxygen dissolved from the inner wall of the quartz crucible 2 will be transported to the gas-liquid two-phase to volatilize into the gas phase in the form of SiO, thereby reducing the input of oxygen below the growth interface.

[0040] The melt flow rate below the gas-liquid two-phase also has a certain influence on the transport and volatilization of oxygen. When the melt flow rate below the gas-liquid two-phase is larger, it means that the oxygen content input into the growth interface will be reduced, and the volatilization rate of SiO in the gas-liquid two-phase will also increase, which will lead to a decrease in the overall oxygen content at the growth interface and in the silicon melt 3.

[0041] As shown in FIG. 1, the melt convection of the present application mainly includes central convection 301 and edge convection 302. The central convection 301 presents a clockwise flow pattern, and the edge convection 302 presents a counterclockwise flow pattern. The central convection 301 mainly brings the oxygen at the bottom of the quartz crucible 2 into the central convection 301, so that part of the oxygen is transported into the silicon single crystal 30 along with the central silicon melt 3 flow; the edge convection 302 brings the oxygen generated by the wall of the crucible into the edge convection 302, and flows through the gas-liquid two-phase melt free surface, so that a large amount of gas-liquid two-phase volatile oxygen is volatilized in the form of SiO, and part of the oxygen that has not been volatilized will continue to be transported along the edge convection 302 in the counterclockwise flow pattern. Part of the oxygen in the edge convection 302 will be transported by solute exchange at the intersection of the central convection 301 and the edge convection 302, so when the melt flow rate (V(cj)) at the intersection of the central convection 301 and the edge convection 302 is larger, the solute exchange transport capacity is stronger, which means that the central convection 301 will obtain more oxygen, thereby transporting the oxygen into the silicon single crystal 30, and increasing the oxygen content in the silicon single crystal 30.

[0042] 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 a region 10-13 mm from the bottom wall of the quartz crucible 2, the maximum dimension L1 of the selected region of the silicon melt 3 projected in the vertical direction, and the center of the projection of the selected region of the silicon melt 3 is located on the central axis of the crucible, satisfying 60mm≤L1≤130mm. Specifically, 10-13 mm can be any value or a range between any two values of 10 mm, 11 mm, 12 mm, and 13 mm;

[0043] L1 can be any value or a range between any two values of 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, and 130 mm. It should be understood that the value region 5 of the oxygen content at the bottom of the crucible in the silicon melt 3 is the silicon melt 3 in the 10-13 mm interlayer from the bottom wall of the crucible, and the silicon melt 3 has a maximum length L1 in the projection plane in the vertical direction, which further limits the value region 5 of the oxygen content at the bottom of the crucible (as shown by the dashed line indicated by the arrow in FIG. 1); by limiting the oxygen content value region, the problem of the oxygen content value region at the bottom of the crucible being too large due to the saturation layer of the dissolved oxygen content in the inner wall of the quartz crucible 2 can be effectively avoided. At the same time, this region is the region where the oxygen content at the bottom of the crucible effectively enters the central convection 301, and therefore, the oxygen content at the bottom of the crucible can be effectively characterized.

[0044] In some embodiments, the oxygen content generated by the crucible wall is the average value of the oxygen content of the silicon melt 3 in a region 5-8 mm from the side wall of the crucible, the distance L2 between the top of the selected region of the silicon melt 3 and the free melt surface 31 in the vertical direction, satisfying 10mm≤L2≤15mm. Specifically, 5-8 mm can be any value or a range between any two values of 5 mm, 6 mm, 7 mm, and 8 mm;

[0045] L2 can be any value in 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm or a range between any two values. It should be understood that the inner wall of the crucible is composed of the bottom wall and the side wall of the crucible, and in the embodiment, the side wall of the crucible is the inner wall region of the crucible except the bottom wall. The oxygen content value region 6 generated by the crucible wall (as shown by the dotted line indicated by the arrow in FIG. 1) is the silicon melt 3 in the 5 mm to 8 mm interlayer from the side wall of the crucible, and the top of the selected region and the free melt surface 31 have a vertical distance L2, which further limits the oxygen content value region 6 generated by the crucible wall. There is part of oxygen in the region close to the free melt surface 31 in the form of SiO volatilization, so the average value of the oxygen content generated by the crucible wall should meet the vertical distance L2 between the top of the selected region of the silicon melt 3 and the free melt surface 31, so as to reduce the data deviation of the average value of the oxygen content. It should be understood that the free melt surface 31 is the gas-liquid interface of the silicon melt 3 in the quartz crucible 2.

[0046] In some embodiments, the average value of the oxygen content of the gas-liquid two-phase volatile oxygen is the oxygen content of the silicon melt 3 in the region 2 mm to 5 mm from the free melt surface. It should be understood that the value region 7 of the gas-liquid two-phase volatile oxygen content (as shown by the dotted line indicated by the arrow in FIG. 1) is the silicon melt 3 in the 2 mm to 5 mm interlayer from the free melt surface. Specifically, 2 mm to 5 mm can be any value in 2 mm, 3 mm, 4 mm, 5 mm or a range between any two values.

[0047] Above, the average values of the oxygen content of the crucible bottom, the oxygen content generated by the crucible wall, and the gas-liquid two-phase volatile oxygen content are obtained by the multi-point average method, that is, a plurality of points in the corresponding silicon melt 3 region are selected for oxygen content measurement, and then the average is calculated. Specifically, by selecting a fixed reference point, the oxygen content calculation value of the point can be obtained by selecting the point in the processing result after CGSim (crystal growth modeling software) simulation.

[0048] In some embodiments, the melt flow rate at the intersection of the center convection 301 and the edge convection 302 is the maximum melt flow rate at the intersection of the center convection 301 and the edge convection 302.

[0049] In some embodiments, before obtaining the parameters for growing the silicon single crystal 30 under the transverse magnetic field, further comprising: simulating the growth of the silicon single crystal 30 by using the CGSim simulation software, the simulation adopting the TDR135 furnace platform, the 32-inch hot field piece, and the 32-inch quartz crucible 2, and the simulated conditions for the growth of the silicon single crystal 30 including one or more of the raw material feeding amount of 400 Kg, the crystal pulling rotation speed of 8 rmp / min, the crucible rotation speed of 0.1 rmp / min, the distance d between the bottom end of the flow guide cylinder 4 and the free melt surface 31 of 40 mm, the transverse magnetic field strength of 0.45 T, the furnace pressure of 30 Torr, and the protective gas flow of 130 slpm, and the protective gas can be argon.

[0050] In order to obtain different oxygen contents, simulation and experiment are carried out by changing the position of the strongest Gaussian surface. In the embodiment 1, the position of the strongest Gaussian surface 8 of the transverse magnetic field is 50 mm above the free melt surface; in the embodiment 2, the position of the strongest Gaussian surface 8 of the transverse magnetic field is flush with the free melt surface; in the embodiment 3, the position of the strongest Gaussian surface 8 of the transverse magnetic field is 50 mm below the free melt surface; in the embodiment 4, the position of the strongest Gaussian surface 8 of the transverse magnetic field is 100 mm below the free melt surface; and in the embodiment 5, the position of the strongest Gaussian surface 8 of the transverse magnetic field is 180 mm below the free melt surface. As shown in FIG. 2, according to the simulation-center oxygen content results, it can be known that: embodiment 2> embodiment 5> embodiment 3> embodiment 1> embodiment 4.

[0051] The growth conditions of the silicon single crystal 30 used in the experiment are consistent with the simulation. By comparing FIG. 3 and FIG. 4, the experimental-center oxygen content results are consistent with the simulation-center oxygen content results, which can prove the accuracy of the simulation-center oxygen content results.

[0052] Specifically, in the embodiments 1 to 5, the oxygen content C(oxy) Central at the bottom of the quartz crucible 2, the oxygen content C(oxy) Edge generated by the wall of the quartz crucible 2, the gas-liquid two-phase volatile oxygen content C(oxy) Free-melt , and the melt flow rate V(cj) at the intersection of the center convection 301 and the edge convection 302 are as follows:

[0053] According to the above table, the initial dissolved oxygen content at the inner wall of the quartz crucible 2 (the oxygen content C(oxy) Central at the bottom of the quartz crucible 2 + the oxygen content C(oxy) Edge), it can be seen that Example 5 > Example 2 > Example 3 > Example 1 > Example 4 (as shown in Figure 5). It can be clearly seen from the M value that the V(cj) of Example 2 is significantly greater than that of Example 5, so the exchange and transport capacity of solute oxygen at the intersection of the center and edge convection 302 is stronger, thereby more oxygen enters the center convection 301, and then is brought into the crystal by the center convection 301, so that the central oxygen content of the growth interface is significantly increased and is greater than that of Example 5. It can be clearly analyzed that: the main reason for the low oxygen content of Example 3, Example 4 and Example 1 is that the oxygen is generated and the dissolved oxygen content of the inner wall of the quartz crucible 2 is low, so that the overall oxygen content of the silicon melt 3 is relatively low, thereby the central oxygen content of the growth interface is also low.

[0054] From the comparison between the reference value M and the simulation and experimental central oxygen content of the growth interface, it can be seen that when 6≤M≤14, the smaller the M value, the smaller the central oxygen content of the growth interface.

[0055] The embodiment also provides a silicon single crystal central oxygen content control system, as shown in Figure 6, the control system includes an acquisition module and an adjustment module, the acquisition module is configured to acquire parameters of the silicon single crystal 30 grown under a transverse magnetic field, the parameters including: oxygen content at the bottom of the crucible, oxygen content generated by the crucible wall, gas-liquid two-phase volatile oxygen content, melt flow rate at the intersection of the center convection 301 and the edge convection 302, the center convection 301 is the melt convection at the center of the crucible, and the edge convection 302 is the melt convection close to the crucible wall in the crucible; the adjustment module is signal connected with the acquisition module, and is configured to adjust the central oxygen content of the silicon single crystal according to the parameters.

[0056] Correspondingly, the embodiment of the present application provides a silicon single crystal central oxygen content control system, which is used to realize the control method of the above-mentioned embodiment, so the silicon single crystal central oxygen content control system can have all the technical features and beneficial effects of the above-mentioned silicon single crystal central oxygen content control method, which will not be repeated here.

[0057] Finally, it should be pointed out that: the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, but not to limit them; although the embodiments of the present application have been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for controlling the central oxygen content of a silicon single crystal, comprising: The parameters for growing the silicon single crystal under a transverse magnetic field are obtained. The parameters include: oxygen content at the bottom of the crucible, oxygen content generated by the crucible wall, oxygen content volatilized in the gas-liquid two-phase system, and melt flow velocity at the junction of central convection and edge convection. The central convection is the melt convection at the center of the crucible, and the edge convection is the melt convection at the inner wall of the crucible. The oxygen content at the center of the silicon single crystal is adjusted according to the parameters.

2. The method for controlling the central oxygen content of a silicon single crystal according to claim 1, wherein, Adjusting the oxygen content at the center of the silicon single crystal according to the parameters includes: A reference value for the oxygen content at the center of the silicon single crystal is obtained based on the oxygen content at the bottom of the crucible, the oxygen content generated by the crucible wall, the oxygen content volatilized in the gas-liquid two-phase reaction, and the melt flow rate. The oxygen content at the center of the silicon single crystal is adjusted according to the reference value.

3. The method for controlling the central oxygen content of a silicon single crystal according to claim 2, wherein, The reference value increases with the difference between the oxygen content generated by the crucible wall and the volatile oxygen content of the gas-liquid two-phase mixture, and with the increase of the melt flow rate.

4. The method for controlling the oxygen content at the center of a silicon single crystal according to claim 2, wherein, The reference value increases with the increase of oxygen content at the bottom of the crucible, the difference between oxygen content generated by the crucible wall and the volatile oxygen content of the gas-liquid two-phase system, and the increase of melt flow rate.

5. The method for controlling the oxygen content at the center of a silicon single crystal according to claim 2, wherein, The reference value is obtained using the following formula: In the formula, M is the reference value; C(oxy) Central This represents the oxygen content at the bottom of the crucible; C(oxy) Edge The oxygen content produced by the crucible wall; C(oxy) Free-melt V(cj) represents the volatile oxygen content of the gas-liquid two-phase system; V(cj) represents the melt flow rate, with oxygen content in ppma and melt flow rate in m / s.

6. The method for controlling the central oxygen content of a silicon single crystal according to any one of claims 2 to 5, wherein, The reference value satisfies: 6≤M≤14. The smaller the reference value, the lower the oxygen content at the center of the silicon single crystal.

7. The method for controlling the oxygen content at the center of a silicon single crystal according to claim 1, wherein, The oxygen content at the bottom of the crucible is the average oxygen content of the silicon melt in the region 10mm to 13mm from the bottom wall of the crucible. The maximum size L1 of the selected area of ​​the silicon melt is projected in the vertical direction. The center of the projection of the selected area of ​​the silicon melt is located on the central axis of the crucible, satisfying 60mm≤L1≤130mm.

8. The method for controlling the central oxygen content of a silicon single crystal according to claim 1, wherein, The oxygen content generated by the crucible wall is the average oxygen content of the silicon melt in the area 5mm to 8mm away from the side wall of the crucible. The vertical distance L2 between the top of the selected area of ​​the silicon melt and the surface of the free melt satisfies 10mm≤L2≤15mm.

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

10. The method for controlling the central oxygen content of a silicon single crystal according to claim 1, wherein, The melt velocity at the junction of the central convection and the edge convection is the maximum value of the melt velocity at the junction of the central convection and the edge convection.

11. The method for controlling the central oxygen content of a silicon single crystal according to claim 1, wherein, Before obtaining the parameters for growing the silicon single crystal under a transverse magnetic field, the method further includes: The growth of silicon single crystals is simulated using simulation software. The conditions for the simulated silicon single crystal growth include one or more of the following: raw material feed rate, crystal pulling speed, crucible speed, distance d between the bottom of the guide tube and the surface of the free melt, transverse magnetic field strength, furnace pressure, and protective gas flow rate.

12. A control system for the central oxygen content of a silicon single crystal, wherein, include: The acquisition module is configured to acquire parameters for growing the silicon single crystal under a transverse magnetic field. The parameters include: oxygen content at the bottom of the crucible, oxygen content generated by the crucible wall, oxygen content volatilized in the gas-liquid two-phase system, and melt flow velocity at the junction of central convection and edge convection. The central convection refers to melt convection at the center of the crucible, and the edge convection refers to melt convection at the inner wall of the crucible. An adjustment module, which is signal-connected to the acquisition module, is configured to adjust the oxygen content at the center of the silicon single crystal according to the parameters.

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