Single crystal diameter control method, device and system

Abstract

The invention discloses a single crystal diameter control method, device and system, and belongs to the field of semiconductors, and the method comprises the following steps: obtaining the current diameter of a single crystal; based on the current diameter, the target diameter of the single crystal and a pre-constructed current calculation model, target current is determined, and the current calculation model is used for representing the mapping relation between the diameter difference value and the current; and controlling the current generation device to apply the target current to the solid-liquid interface of the single crystal so as to adjust the current diameter based on the target current. According to the method, the response speed of diameter control can be greatly increased, and the diameter change of the single crystal caused by the fluctuation of the solid-liquid interface temperature field is effectively inhibited, so that the accuracy of diameter control is improved, and the diameter control effect in the Czochralski single crystal production process is integrally improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a method, apparatus, and system for controlling the diameter of a single crystal. Background Technology

[0002] Single crystals can be prepared using the Czochralski method, which involves controlling the rotation and pulling of a seed crystal from a solution to allow the solution to solidify at the solid-liquid interface and grow a single crystal that meets the required size. Maintaining the stability of the single crystal diameter throughout the growth process is a key step in ensuring single crystal quality and improving the yield.

[0003] The relevant technologies mainly control the diameter of single crystals by adjusting the pulling speed or heating power. However, adjusting the pulling speed can easily cause transient solute segregation, affecting the quality of the finished single crystal, while adjusting the heating power has a strong lag, and often cannot suppress spontaneous diameter fluctuations in a timely and accurate manner during stages where rapid diameter adjustment is required (such as the shoulder expansion stage). Therefore, the diameter control effect of the relevant technologies is relatively poor. Summary of the Invention

[0004] A method, apparatus, and system for controlling the diameter of single crystals are provided, aiming to improve the diameter control effect of Czochralski single crystals.

[0005] Firstly, a method for controlling the diameter of a single crystal is provided, including: Get the current diameter of the single crystal; Based on the current diameter, the target diameter of the single crystal, and the pre-built current calculation model, the target current is determined. The current calculation model is used to characterize the mapping relationship between the diameter difference and the current. The current generating device is controlled to apply the target current to the solid-liquid interface of the single crystal, so as to adjust the current diameter based on the target current.

[0006] In some embodiments, the steps of constructing the current calculation model include: Based on the Boltier effect, an initial mapping relationship is established between the diameter of the single crystal and the current flowing through the solid-liquid interface and the thermodynamic correlation parameters of the solid-liquid interface. Based on the initial mapping relationship, the current calculation model is constructed.

[0007] In some embodiments, the solid-liquid interface thermodynamic correlation parameters include at least one of the following: solid-liquid interface temperature, solid-liquid interface Seebeck coefficient, latent heat of solidification of single crystal material, solid density of single crystal material, and axial pulling speed of single crystal growth.

[0008] In some embodiments, the method further includes: Based on the current diameter, the target current, and the thermodynamic correlation parameters of the solid-liquid interface, the net temperature dissipation of the solid-liquid interface is determined.

[0009] In some embodiments, the current generating device includes a first current device, one end of which is connected to the steel wire pulling the single crystal via a first loop wire, and the other end is connected to the silicon solution via a second loop wire to form a first current loop. The control current generating device applies the target current to the solid-liquid interface of the single crystal, including: The first current device is controlled to output the target current to the solid-liquid interface.

[0010] In some embodiments, the first current device includes a DC power supply and a variable resistor, the DC power supply being configured to output a preset voltage; Controlling the first current device to output the target current to the solid-liquid interface includes: The variable resistor is controlled to be adjusted to the target resistance value so that the first current loop generates the target current.

[0011] In some embodiments, the current generating device includes a second current device disposed outside the single crystal furnace; controlling the current generating device to apply the target current to the solid-liquid interface of the single crystal includes: The second current device is controlled to generate a first magnetic field, and the second current device is controlled to move in a direction perpendicular to the single crystal growth axis, so as to form the target current at the solid-liquid interface when the first magnetic field covers the solid-liquid interface.

[0012] In some embodiments, the second current device includes: The first support rods are arranged opposite to each other on both sides of the single crystal furnace, and the slide rails are arranged on the first support rods; A magnetic field generating device is slidably connected to the corresponding slide rail. The magnetic field generating device is configured to generate the first magnetic field, wherein the magnetic induction intensity of the first magnetic field and / or the moving speed of the magnetic field generating device along the slide rail are configured to adjust the magnitude of the current formed at the solid-liquid interface.

[0013] In some embodiments, the current generating device includes a third current device disposed outside the single crystal furnace; controlling the current generating device to apply the target current to the solid-liquid interface of the single crystal includes: The third current device controls the induction of the target current in the second current loop, wherein the second current loop is formed by connecting the steel wire pulling the single crystal and the silicon solution through the third loop wire.

[0014] In some embodiments, the third current device includes: The number of turns of the magnetic induction coil and / or the rate of change of the input current of the magnetic induction coil are configured to adjust the magnitude of the current induced in the second current loop, relative to the second support rods disposed on both sides of the single crystal furnace and the magnetic induction coil disposed on the second support rods.

[0015] Secondly, a single crystal diameter control device is also provided, comprising: The diameter detection module is used to obtain the current diameter of the single crystal; The current calculation module is used to determine the target current based on the current diameter, the target diameter of the single crystal, and a pre-built current calculation model. The current calculation model is used to characterize the mapping relationship between the diameter difference and the current. A diameter control module is used to control the current generating device to apply the target current to the solid-liquid interface of the single crystal, so as to adjust the current diameter based on the target current.

[0016] Thirdly, a single crystal diameter control system is also provided, including: A central control device, the central control device being configured to perform the single crystal diameter control method as described in any of the first aspects; A current generating device, connected to the central control device, is configured to apply a target current to the solid-liquid interface of the single crystal to adjust the current diameter of the single crystal based on the target current.

[0017] The method in this application embodiment determines the target current based on the difference between the current diameter and the target diameter through a preset current calculation model, which can realize closed-loop feedback and quantitative control from diameter deviation to current control quantity. By directly applying the target current to the solid-liquid interface of crystal growth, the solid-liquid interface can be quickly and directly intervened, thereby greatly improving the response speed of diameter control, effectively suppressing the single crystal diameter change caused by solid-liquid interface temperature field fluctuation, and thus improving the accuracy of diameter control, and improving the overall diameter control effect in the Czochralski single crystal production process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the structure of the Czochralski single crystal control system provided in the embodiments of this application; Figure 2 This is a schematic flowchart of the single crystal diameter control method according to an embodiment of this application; Figure 3This is a schematic diagram of an example of a current generating device according to an embodiment of this application; Figure 4 for Figure 3 A circuit diagram of the first current loop in the circuit; Figure 5 for Figure 3 A schematic diagram of the structure of the first current device in the middle; Figure 6 This is another example schematic diagram of the current generating device according to an embodiment of this application; Figure 7 for Figure 6 A schematic diagram of the second current device along the AA direction; Figure 8 This is another example schematic diagram of the current generating device according to an embodiment of this application; Figure 9 for Figure 8 A schematic diagram of the structure of the third current device at one angle; Figure 10 This is a schematic diagram illustrating an example of the diameter during the shoulder-expanding stage in an embodiment of this application; Figure 11 This is a schematic diagram of the single crystal diameter control device according to an embodiment of this application.

[0020] Explanation of reference numerals in the attached figures: 10-Central control equipment; 20-Current generating device; 21-DC power supply; 22-Variable resistor; 23-Ammeter; 24-First support rod; 25-Slide rail; 26-Magnetic field generating device; 27-Second support rod; 28-Magnetic induction coil; 30-Steel wire; 40-Single crystal; 51-First circuit wire; 52-Second circuit wire; 53-Third circuit wire; 60-Silicon solution; 71-Diameter detection module; 72-Current calculation module; 73-Diameter control module. Detailed Implementation

[0021] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0023] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0024] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0025] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0026] In the process of single crystal growth, related technologies mainly control the diameter of single crystals by adjusting the pulling speed or heating power. However, both methods have inherent drawbacks. For example, adjusting the pulling speed can easily cause transient solute segregation, directly affecting the quality of the finished single crystal. Adjusting the heating power mainly involves regulating the power of the graphite heating device. Due to the inherent characteristics of graphite's high specific heat capacity and non-uniform heat conduction, the delay effect of the multi-medium coupling heat transfer path, and the insufficient response of traditional PID (Proportional-Integral-Derivative) control strategies, controlling the diameter growth of single crystals by adjusting the heating power exhibits strong lag, making it impossible to adjust the diameter in a timely manner. This lag is particularly problematic during the shoulder expansion stage, where it is difficult to effectively suppress spontaneous shoulder expansion. Therefore, the diameter control effect of these technologies is relatively poor.

[0027] In view of this, embodiments of this application provide a single crystal diameter control method, device and system, which determines the target current by combining the difference between the current diameter and the target diameter with a preset current calculation model, and applies the target current to the solid-liquid interface of crystal growth to control the current diameter to tend towards the target diameter, thereby realizing precise autonomous control of the diameter during the growth of single crystal 40, and effectively improving the diameter control effect in the production process of Czochralski single crystal 40.

[0028] Please see Figure 1 , Figure 1 This is a schematic diagram of the Czochralski single crystal control system provided in an embodiment of this application. The Czochralski single crystal control system includes a central control device 10 and a current generating device 20. The central control device 10 is configured to execute the single crystal diameter control method of this embodiment to determine a target current. The current generating device 20 is connected to the central control device 10 and is configured to apply the target current to the solid-liquid interface of the single crystal 40 to adjust the current diameter of the single crystal 40 based on the target current.

[0029] The single crystal diameter control method and current generation device 20 of this application embodiment will be described below with reference to the accompanying drawings.

[0030] Please see Figure 2 , Figure 2 This is a schematic flowchart of a single crystal diameter control method according to an embodiment of this application. The single crystal diameter control method includes the following steps: Step 201: Obtain the current diameter of single crystal 40.

[0031] For example, the current diameter can be obtained directly or indirectly, such as by using a CCD (Charge) sensor. A charge-coupled device (CCD) reads the current diameter of a single crystal 40 in real time during its growth process.

[0032] In this embodiment, since there is a known conversion relationship between the diameter d, radius r, and cross-sectional area S, for example, d = 2 × r, S = πr 2 =π×(d / 2) 2 Therefore, at least one of the current diameter, current radius, and current cross-sectional area during the growth process of single crystal 40 can be read in real time, and the current diameter can be obtained directly or indirectly. Unless otherwise specified, the diameter will be used as an example in the following description. It is understood that the diameter of single crystal 40 mentioned in the embodiments of this application can be converted between the radius and cross-sectional area of ​​single crystal 40.

[0033] Step 202: Based on the current diameter, the target diameter of single crystal 40, and the pre-built current calculation model, determine the target current. The current calculation model is used to characterize the mapping relationship between the diameter difference and the current.

[0034] Specifically, a target diameter can be set during the growth of single crystal 40 as a control benchmark. For example, during the shoulder expansion stage, the target diameter can be determined based on the target shoulder shape, where the target shoulder shape characterizes the mapping relationship between the axial length of single crystal 40 and the target diameter.

[0035] In some examples, the steps to build a current calculation model include: Step 1: Based on the Boltier effect, establish an initial mapping relationship between the diameter of single crystal 40 and the current flowing through the solid-liquid interface and the thermodynamic correlation parameters of the solid-liquid interface.

[0036] For example, the thermodynamic correlation parameters of the solid-liquid interface include the solid-liquid interface temperature and the Seebeck coefficient S at the solid-liquid interface. αβ At least one of the following: the latent heat of solidification of single crystal 40 material, the solid density of single crystal 40 material, and the axial pulling rate of single crystal 40 growth.

[0037] The Bolter effect indicates that when an electric current passes through two different materials, it is accompanied by either heat absorption or release. Based on this example and the principle of the Bolter effect, the solid-liquid contact area A of single crystal 40 can be determined by the following formula: ; Where A is the solid-liquid contact area of ​​single crystal 40, A=πr 2 r is the radius of the single crystal (40). This represents the heat dissipation of the solid. ν is the heat transfer rate of the liquid; L is the latent heat of solidification of the material; v is the axial pulling speed of single crystal 40 growth; The solid density of single-crystal 40 material; This is caused by the glass-like effect ( ) or absorption ( ( ) calories.

[0038] Based on the above formula, there are four ways to adjust the solid-liquid contact area (or radius, diameter) of single crystal 40: increasing the heat exchange of the solid, reducing the heat transferred from the liquid, adjusting the pulling speed, and generating or absorbing heat through the Boltier effect. The Boltier effect can be expressed by the following formula: ; ; Where Q represents power heat; The glass coefficient (α and β represent two different materials and are related to both materials and temperature); For current; This refers to the solid-liquid interface temperature. It is the Seebeck coefficient at the solid-liquid interface (corresponding to the Seebeck effect, which is the opposite of the Bolter effect).

[0039] Combining the formula for determining the solid-liquid contact area A of single crystal 40 and the Bolter effect formula, the initial mapping relationship can be expressed by the following formula: .

[0040] Step 2: Based on the initial mapping relationship, construct the current calculation model.

[0041] Specifically, the current calculation model can be determined using the following formula: ; Where r2 is the target radius, d2 is the target diameter, and the unit is millimeters (mm); r1 is the current radius, d1 is the current diameter, and the unit is millimeters (mm). For example, the value range can be 5mm to 150mm. It is the solid-liquid interface temperature, with the dimension K (Kelvin), for example, the value range can be 1675K~1695K (i.e. 1400℃~1420℃). This is the Seebeck coefficient at the solid-liquid interface, with dimensions V / K (volts per Kelvin). For example, its value can be... 1.5×10 4 V / K; The current I flows through the solid-liquid interface, with the dimension A (ampere). It can be measured by ammeter 23. The direction of the current I can be from solid to liquid or from liquid to solid. The latent heat of solidification of a material is expressed in J / g (joules per gram). For example, its value can range from 1654 J / g to 1826 J / g. The latent heat of solidification can be obtained using differential scanning calorimetry (DSC). The axial pulling speed for single crystal 40 growth is measured in mm / h (millimeters per hour). The value can be set directly; for example, the range of the pulling speed set in the process can be 20 mm / h to 50 mm / h. The solid density of single-crystal 40 material is expressed in g / mm². 3 (grams per cubic millimeter), for example, the solid density of monocrystalline silicon is 2.33E-3 g / mm². 3 .

[0042] For example, based on the initial mapping relationship, the current calculation model of this application embodiment can be derived as follows: For the current radius r1, if no current is applied to the solid-liquid interface, then the initial mapping relationship corresponding to the current radius r1 is: ; The current radius r1 is controlled by the temperature field and the pulling speed. A current is to be applied at the solid-liquid interface to control the current radius r1 towards the target radius r2. Therefore, the initial mapping relationship corresponding to the target radius r2 is: ; Since they are under the same thermal field and pulling speed, the difference between the initial mapping relationship corresponding to the current radius r1 and the initial mapping relationship corresponding to the target radius r2 can be used to obtain the mapping formula between the current and the radius difference, i.e. the current calculation model. Since the positive and negative signs before the current only indicate the direction, the negative signs are removed and only the current magnitude is retained. The specific current direction is explained below.

[0043] By establishing the mapping relationship between the diameter difference between the current diameter and the target diameter and the current flowing through the solid-liquid interface using the above method, the target current can be obtained based on the diameter difference between the current diameter and the target diameter. Specifically, when the current diameter is larger than the target diameter, the direction of the target current is from the solution to the crystal; when the current diameter is smaller than the target diameter, the direction of the target current is from the crystal to the solution.

[0044] In some embodiments, step 202 can be implemented in the following ways: If the diameter difference between the current diameter and the target diameter exceeds a preset range, the target current is adjusted to bring the current diameter to the target diameter. In other words, the target current adjustment can be initiated when the diameter difference exceeds a preset range.

[0045] In other embodiments, the target current can also be adjusted in real time based on the diameter difference, but this application does not specifically limit this.

[0046] In some embodiments, after performing step 202 to determine the target current, the present application embodiments further include the following steps: Based on the current diameter, target current, and thermodynamic correlation parameters of the solid-liquid interface, determine the net temperature dissipation at the solid-liquid interface.

[0047] For example, by modifying the initial mapping relationship, the net temperature dissipation at the solid-liquid interface can be expressed by the following formula: ; in, This represents the net temperature dissipation at the solid-liquid interface, measured in J (joules).

[0048] For example, a display device can be set up to show the net temperature dissipation at the solid-liquid interface. In this way, by using the current diameter of the single crystal 40, the target current, and the thermodynamic correlation parameters of the solid-liquid interface, the net temperature dissipation at the solid-liquid interface can be obtained, enabling efficient and accurate monitoring of the net temperature dissipation at the solid-liquid interface. This facilitates the detection of any abrupt changes and provides a data foundation for subsequent research.

[0049] Step 203: Control the current generating device 20 to apply a target current to the solid-liquid interface of the single crystal 40, so as to adjust the current diameter based on the target current.

[0050] Please refer to the following: Figure 3 , Figure 4 and Figure 5 , Figure 3 This is a schematic diagram of an example of a current generating device according to an embodiment of this application. Figure 4 for Figure 3 The circuit diagram of the first current loop in the circuit. Figure 5 for Figure 3 A schematic diagram of the first current generating device is shown. In some examples, the current generating device 20 includes a first current generating device, one end of which is connected to the steel wire 30 of the pulled single crystal 40 via a first loop wire 51, and the other end is connected to the silicon solution 60 via a second loop wire 52 to form a first current loop. Exemplarily, an electrode may be provided at the end of the second loop wire 52 connected to the silicon solution 60. This electrode is made of a high-temperature resistant conductive material, such as silicon carbide. This provides the advantages of introducing fewer impurities and high-temperature resistance.

[0051] Based on this example, step 203 is achieved through the following steps: The first current control device outputs the target current to the solid-liquid interface.

[0052] Specifically, the first loop conductor 51 and the second loop conductor 52 are both at least partially located inside the single crystal 40 furnace. The first loop conductor 51, the second loop conductor 52, the single crystal 40, the silicon solution 60, and the first current device form a closed first current loop. The first current device can directly output a target current to the solid-liquid interface to change the current diameter of the single crystal 40.

[0053] In some examples, the first current device includes a DC power supply 21 and a variable resistor 22. The DC power supply 21 is configured to output a preset voltage, and the variable resistor 22 is configured to adjust the current in the first current loop, for example, the current adjustment range can be 1A to 10000A. The first current device may also include an ammeter 23, which is configured to detect the current in the first current loop. The central control device 10 is configured to control the first current device to output a target current to the solid-liquid interface in the following manner: The variable resistor 22 is adjusted to the target resistance value so that the first current loop generates the target current.

[0054] Specifically, based on the calculated target current and the preset voltage output by the DC power supply 21, the target resistance value of the variable resistor 22 is determined. The central control device 10 controls the variable resistor 22 to adjust to the target resistance value, thereby generating the target current in the first current loop, and causing the solid-liquid interface to flow through the target current.

[0055] Through the above scheme, the central control device 10 can directly control the magnitude and direction of the current in the first current loop, realize precise regulation of the current parameters, and thus precisely adjust the current diameter of the single crystal 40; the central control device 10 can also detect the current value in the first current loop in real time, and thus monitor the operating status of the first circuit loop in real time; the central control device 10 can have a built-in adjustment system, which can automatically adjust the current magnitude when the change of the current diameter relative to the target diameter exceeds the preset range, and thus regulate the current diameter to the target range; the central control device 10 can also be equipped with a calculation program to calculate the net temperature dissipation at the solid-liquid interface based on parameters such as the current diameter, pulling speed, and target current, thereby realizing real-time monitoring of the net temperature dissipation at the interface.

[0056] Please refer to the following: Figure 6 and Figure 7 , Figure 6 This is another example schematic diagram of the current generating device according to an embodiment of this application. Figure 7 for Figure 6 A schematic diagram of the second current device along the AA direction. In other examples, the current generating device 20 includes a second current device disposed outside the single crystal furnace 40. In some examples, the central control device 10 is connected to the second current device.

[0057] Based on this example, the central control device 10 can implement step 203 through the following steps: The second current device is controlled to generate a first magnetic field, and the second current device is controlled to move along a direction (Y direction) perpendicular to the growth axis of the single crystal 40 (Z direction) to form a target current at the solid-liquid interface when the first magnetic field covers the solid-liquid interface.

[0058] Specifically, high magnetic fields are generally generated electrically, and the magnetic field strength varies at each location, thus the first magnetic field always carries a magnetic field strength gradient. For example, the magnetic field strength gradient can be set to 1-5 Tesla per meter (T / m), such as any one or a range of any two of the following values: 1T / m, 1.2T / m, 1.4T / m, 1.6T / m, 1.8T / m, 2T / m, 2.2T / m, 2.4T / m, 2.6T / m, 2.8T / m, 3T / m, 3.2T / m, 3.4T / m, 3.6T / m, 3.8T / m, 4T / m, 4.2T / m, 4.4T / m, 4.6T / m, 4.8T / m, and 5T / m. This application does not impose specific requirements on the magnetic field strength gradient; generally, a larger value results in better performance.

[0059] In some examples, the second current device includes: The first support rods 24 are respectively arranged on both sides of the single crystal 40 furnace, and the slide rails 25 are arranged on the first support rods 24; A magnetic field generating device 26 is slidably connected to a corresponding slide rail 25. The magnetic field generating device 26 is configured to generate a first magnetic field, wherein the magnetic induction intensity of the first magnetic field and / or the moving speed of the magnetic field generating device 26 along the slide rail 25 are configured to adjust the magnitude of the current formed at the solid-liquid interface.

[0060] For example, the magnetic field generating device 26 is an element that generates a magnetic field, and generates a first magnetic field by being driven by an electric current.

[0061] Specifically, the formula for determining the motional current is as follows: ; Where B is the magnetic flux density, with the dimension T (Tesla), and its value range can be 1T to 2T; The effective cutting length of the conductor rod, in this embodiment of the application, refers to the solid-liquid length of the cutting magnetic field lines, with the dimension of mm. For example, the default length can be 5mm~10mm. The velocity of the conductor rod perpendicular to the direction of the magnetic field is measured in m / s (meters per second), and its range can be 0 to 200 m / s. The circuit resistance is in units of Ω (ohms) and can be calculated using resistivity.

[0062] According to the formula for determining motional current, when the first magnetic field passes through the solid-liquid interface, several conducting rods will cut the magnetic field lines, resulting in several induced loops e. The potential difference generated after a conducting rod in the same loop cuts the magnetic field lines is different; therefore, the total current is not zero, and current flows through the solid-liquid interface. Since the material remains unchanged and no new resistance is introduced, the loop resistance R is constant, and the effective cutting length of the conducting rod is... At the solid-liquid interface, the default value is fixed. Therefore, the method for adjusting the motional current can include adjusting the magnetic induction intensity B of the first magnetic field, or adjusting the moving speed V of the magnetic field generating device 26 along the slide rail 25, or simultaneously adjusting the magnetic induction intensity B of the first magnetic field and the moving speed V of the magnetic field generating device 26 along the slide rail 25. For example, the moving speed V of the conductor rod perpendicular to the magnetic field direction can be calculated using the formula for determining the motional current, based on the target current I, the magnetic induction intensity B of the first magnetic field, the effective cutting length l of the conductor rod, and the loop resistance R. Then, the central control device 10 adjusts only the moving speed V of the magnetic field generating device 26 along the slide rail 25 to achieve the adjustment of the current diameter.

[0063] In this example, a movable first magnetic field with magnetic induction intensity is set outside the single crystal furnace 40, and a target current is generated by utilizing the principle of a conductor cutting magnetic field lines. The direction of the target current can be changed by controlling the direction of the first magnetic field or the movement direction of the magnetic field generating device 26 along the slide rail 25 via the central control device 10. The magnitude of the current can be adjusted by controlling the movement speed of the magnetic field generating device 26 along the slide rail 25 or the magnetic induction intensity of the first magnetic field via the central control device 10.

[0064] The above scheme involves adding a constant magnetic field with a magnetic induction intensity gradient outside the single crystal 40 furnace, causing the single crystal 40 and the solution to move relative to the applied constant magnetic field. This generates a motional electromotive force by cutting the magnetic field lines, thereby forming a target current at the solid-liquid interface. This scheme eliminates the need to build circuits inside the furnace and avoids the need to consider high-temperature resistant materials, which can reduce contamination of the silicon solution 60, thereby reducing the impact on the quality of the single crystal 40. It is also convenient to set up and can make the solute distribution more uniform.

[0065] Please refer to the following: Figure 8 and Figure 9 , Figure 8 This is another example schematic diagram of the current generating device according to an embodiment of this application. Figure 9 for Figure 8 A schematic diagram of the third current device from an angle. In some other examples, the current generating device 20 includes a third current device, which is located outside the single crystal furnace 40. In some examples, the central control device 10 is connected to the third current device.

[0066] Based on this example, the central control device 10 can implement step 203 through the following steps: The third current control device induces the target current in the second current loop, wherein the second current loop is formed by connecting the steel wire 30 of the pulled single crystal 40 and the silicon solution 60 through the third loop wire 53.

[0067] Specifically, an electrode can be installed at one end of the third circuit wire 53 connected to the silicon solution 60. This electrode is made of a high-temperature resistant conductive material, such as silicon carbide. This provides the advantages of introducing fewer impurities and being resistant to high temperatures.

[0068] In some examples, the third current device includes: The number of turns of the magnetic induction coil 28 and / or the rate of change of the input current of the magnetic induction coil 28 are configured to adjust the magnitude of the current induced in the second current loop relative to the second support rod 27 disposed on both sides of the single crystal 40 furnace and the magnetic induction coil 28 disposed on the second support rod 27.

[0069] Specifically, the formula for determining the induced current is as follows: ; ; in, is the magnetic flux, with dimensions Wb (Weber). This refers to the number of coil turns. The circuit resistance is measured in Ω (ohms). is the change in magnetic flux density, with the dimension T (Tesla). Let be the area through which the magnetic field lines pass perpendicularly.

[0070] According to the formula for determining the induced current, a magnetic induction coil 28 is placed outside the single crystal furnace. By changing the input current of the magnetic induction coil 28, a changing magnetic field is generated, thereby inducing a current at the solid-liquid interface through electromagnetic induction, which serves as the target current. Since the material remains unchanged and no new resistance is introduced, the loop resistance R is constant. After the position of the magnetic induction coil 28 is set, the area through which the magnetic field lines pass perpendicularly is determined. This is also a constant value. Therefore, the method for adjusting the induced current can include adjusting the number of coil turns n, or adjusting the rate of change of magnetic flux density (i.e., adjusting the amount of change of magnetic flux density per unit time), or simultaneously adjusting the number of coil turns n and the rate of change of magnetic flux density. The rate of change of flux density can be achieved by adjusting the rate of change of the input current of the magnetic induction coil 28. For example, when the number of coil turns n is selected, it can be adjusted using the target current I, the number of coil turns n, the loop resistance R, and the area through which the magnetic field lines perpendicularly pass. The rate of change of magnetic flux density is calculated using the formula for determining induced current. Then, based on the conversion relationship between magnetic flux density and input current, the rate of change of input current is obtained. Subsequently, the rate of change of input current is controlled by the central control device 10 to achieve the adjustment of the current diameter.

[0071] In this example, a magnetic induction coil 28 is placed outside the single crystal 40 furnace. By adjusting the input current of the coil, the magnitude of the magnetic field it generates can be precisely controlled. The change in the magnitude of the magnetic field directly affects the intensity of magnetoelectricity, thereby achieving the regulation of the current magnitude at the solid-liquid interface.

[0072] The above scheme generates an induced electromotive force by controlling the rate of change of the input current of the magnetic induction coil 28, thereby forming a target current at the solid-liquid interface. This scheme can reduce the number of devices installed inside the furnace, thus reducing the space occupied inside the furnace. At the same time, it does not require moving the equipment, making it convenient to set up, and it can also make the solute distribution more uniform.

[0073] The single crystal diameter control method of this application embodiment will be described below with reference to specific examples.

[0074] Assuming net temperature dissipation at the solid-liquid interface With the pulling speed v constant, let: ; ; The initial mapping relationship can then be transformed into the following formula: .

[0075] Please see Figure 10 , Figure 10 This is a schematic diagram illustrating the diameter during the shoulder expansion stage in an embodiment of this application. In actual production, under the same process conditions, the diameter of each 40mm single crystal pulled varies, as detailed below. Figure 10 As shown. Compared to the target diameter, the maximum deviation in diameter from the target diameter achieved in a single pulling process can reach 55%. To address this, this application embodiment utilizes the Peltier effect to achieve real-time control of the current diameter of the single crystal 40 by adjusting the target current. The data obtained from the real-time control can be found in Table 1 below, where the Seebeck coefficient of the solid-liquid interface used in Table 1... The value is taken as 1.5E-4 (V / K), the latent heat of solidification L of the material is taken as 1800 (J / g), the axial tensile speed v is taken as 20~50 (mm / h), and the solid density of single crystal 40 material is... The value is 2.33E-3 (g / mm 3 The solid-liquid interface temperature T is set to 1683 K. Verification showed that, using this control method, the maximum deviation between the actual and ideal shoulder shape was only 5%, a small deviation likely due to the time required for Peltier heat transfer. Furthermore, this current control method based on the Peltier effect also provides good diameter control during the constant-diameter stage and the final stage of single-crystal 40 growth.

[0076] Table 1: Data on Current Diameter and Target Current During the Shoulder Expansion Stage

[0077] To adopt Figure 3 Taking the current generating device 20 as an example, electrodes are added above the seed crystal and in the molten silicon. The electrodes placed in the molten silicon are preferably made of a material that is heat-resistant and causes minimal contamination to the silicon melt. In this embodiment, silicon carbide is used, which has a high melting point (2700℃) and minimal contamination. A central control device 10 is added to the secondary chamber, connecting the first circuit wire 51 and the second circuit wire 52. After the seed crystal contacts the solid-liquid interface, the circuit forms a closed circuit. After temperature stabilization, the crucible position, in this embodiment, represents the position where the molten raw material surface in the crucible is a certain distance from the bottom of the guide tube. The first position is 20mm~35mm from the bottom of the guide tube, preferably 25mm~30mm. To improve the stability of the dopant in the molten silicon, this embodiment sets the crucible rotation speed between 5rpm and 20rpm and keeps it constant. Adjust the heater to set the shoulder expansion power between 60KW and 80KW, with a power decrease gradient of 0.5KW-1KW to ensure temperature stability during the shoulder expansion stage. Control the seed crystal rise speed (pulling speed) between 20mm / h and 50mm / h. To avoid transient segregation leading to breakage during single crystal 40 pulling or poor quality after crystallization, the pulling speed must be kept constant. Simultaneously, control the rotation speed of single crystal 40 between 5rpm and 20rpm. To prevent excessive volatilization of dopants, resulting in a low dopant concentration in the solid single crystal silicon after crystallization, the furnace pressure environment is set to 70-300 torr.

[0078] Because the shoulder growth stage has a certain degree of spontaneity, the shoulder shape must be manually controlled. Therefore, the shoulder shape growth is different each time. In the embodiments of this application, single-crystal silicon was pulled multiple times under the above process parameters. After the temperature of the single-crystal silicon decreased, the diameter was recorded and the shoulder shape was drawn every 10mm~15mm. When no current was applied, the repeatability of the shoulder shape was extremely poor, and the shoulder shape drawn each time was different. At the same position (same z-axis length), the wider the shoulder shape, the greater the error. During the experiment, the maximum error could reach a deviation of 55%.

[0079] When current is passed through the first current loop, a change in the shoulder shape can be observed as the current passes through the solid-liquid interface. This is due to the Boltzmann effect. When the forward current is applied, i.e., the current flows from the crystal to the solution, heat is absorbed, and the diameter increases; when the reverse current is applied, i.e., the current flows from the solution to the crystal, heat is released, and the diameter decreases. The current can be adjusted via the central control device 10. The current diameter can be viewed through a CCD device, and the required current adjustment value can be calculated using the diameter difference between the target diameter and the current diameter.

[0080] During the experiment, a target shoulder shape was set, and multiple sets of tests were conducted at different locations. For example, the shoulder shape was measured for the first time at a 10mm expansion position, and then the current was adjusted to bring it closer to the target shoulder shape; the shoulder shape was measured again at a 20mm expansion position, and the current was adjusted to bring it closer to the target shoulder shape; and so on. Finally, a shoulder shape controlled in real time throughout the process was designed. The final records included the current diameter (CCD data), input current (central control device 10), and adjusted diameter (CCD data). The data is displayed in a table showing the diameter and current during shoulder expansion (the data is a summary of the data for each experiment, as shown in Table 1). The experiment shows that the current magnitude is affected by the process and the shoulder expansion position. Generally, the further the expansion, the greater the deviation, and the larger the current is required for adjustment. In this embodiment, the current range is 5A-6000A.

[0081] To adopt Figure 6 Taking the current generating device 20 shown as an example, the growth parameters of single crystal 40 are discussed in the previous example. During the experiment, it is necessary to control the magnetic induction intensity and the magnetic field moving speed. The magnetic induction intensity is set between 1T and 2T, forming a gradient magnetic field. This allows a potential difference to be generated when cutting magnetic field lines, resulting in heat absorption or release. The magnetic field moving speed is set between 10cm / min and 20cm / min to prevent excessive speed from significantly affecting convection in the molten liquid. In this embodiment, a cutting length of 1mm to 5mm at the solid-liquid interface is relatively reasonable. The motional current increases with the increase of both the magnetic induction intensity and the magnetic field moving speed. In this magnetic field design, the current can vary from 5A to 6000A, satisfying the current range required in the previous example. This experiment only involved real-time changes to the shoulder shape; the range of motion was changed from a 5% fluctuation range of the original target shoulder shape to an 8% fluctuation range. Simultaneously, due to the disturbance of the transverse magnetic field, the wafer's RRV (Radial Resistivity Variation) decreases, resulting in more uniform resistivity.

[0082] To adopt Figure 8 Taking the current generating device 20 shown as an example, the growth parameters of single crystal 40 are discussed in the first example. During the experiment, it is necessary to control the rate of change of magnetic induction intensity, which is set between 1T and 2T. Since there is only one single crystal 40 in the induction circuit, the number of coil turns is 1. When a large current is required, the magnetic flux per unit time must be very large, which will inevitably increase the cost. In this experiment, the change in magnetic induction intensity is between 0.001T and 1T. In the design of the magnetic field, the current can vary from 5A to 6000A, meeting the current range required in the first example. This experiment only involved real-time changes to the shoulder shape; the range of motion was changed from a 5% fluctuation range of the original target shoulder shape to a 10% fluctuation range. Simultaneously, due to the disturbance of the transverse magnetic field, the wafer RRV decreases, and the resistivity becomes more uniform.

[0083] It is understood that the method in this application embodiment, based on the difference between the current diameter and the target diameter, determines the target current through a preset current calculation model, which can realize closed-loop feedback and quantitative control from diameter deviation to current control quantity. By directly applying the target current to the solid-liquid interface of crystal growth, the solid-liquid interface can be quickly and directly intervened, thereby greatly improving the response speed of diameter control, effectively suppressing the diameter change of single crystal 40 caused by solid-liquid interface temperature field fluctuations, and thus improving the accuracy of diameter control, and improving the overall diameter control effect in the Czochralski single crystal 40 production process. It can also control the real-time parameters at the solid-liquid interface at all stages of Czochralski single crystal 40, achieve efficient monitoring of the net temperature dissipation of the solid-liquid interface, and significantly reduce the spontaneous effect of the shoulder expansion process.

[0084] Accordingly, this application provides a single crystal diameter control device. Please refer to [link / reference]. Figure 11 , Figure 11 This is a schematic diagram of the single crystal diameter control device according to an embodiment of this application. The single crystal diameter control device can be configured in the central control device 10, and specifically includes a diameter detection module 71, a current calculation module 72, and a diameter control module 73.

[0085] Diameter detection module 71 is used to obtain the current diameter of single crystal 40; The current calculation module 72 is used to determine the target current based on the current diameter, the target diameter of the single crystal 40, and the pre-built current calculation model. The current calculation model is used to characterize the mapping relationship between the diameter difference and the current. The diameter control module 73 is used to control the current generating device 20 to apply a target current to the solid-liquid interface of the single crystal 40, so as to adjust the current diameter based on the target current.

[0086] In some embodiments, the steps of constructing a current calculation model include: Based on the Boltier effect, an initial mapping relationship is established between the diameter of single crystal 40 and the current flowing through the solid-liquid interface and the thermodynamic correlation parameters of the solid-liquid interface. A current calculation model is constructed based on the initial mapping relationship.

[0087] In some embodiments, the solid-liquid interface thermodynamic correlation parameters include at least one of the following: solid-liquid interface temperature, solid-liquid interface Seebeck coefficient, latent heat of solidification of single crystal 40 material, solid density of single crystal 40 material, and axial pulling rate of single crystal 40 growth.

[0088] In some embodiments, the device further includes: The display module is used to determine the net temperature dissipation of the solid-liquid interface based on the current diameter, target current, and solid-liquid interface thermodynamic correlation parameters.

[0089] In some embodiments, the current generating device 20 includes a first current device, one end of which is connected to the steel wire 30 of the Czochralski single crystal 40 via a first loop wire 51, and the other end is connected to the silicon solution 60 via a second loop wire 52 to form a first current loop. Diameter control module 73 is specifically used for: The first current control device outputs the target current to the solid-liquid interface.

[0090] In some embodiments, the first current device includes a DC power supply 21 and a variable resistor 22, wherein the DC power supply 21 is configured to output a preset voltage. Diameter control module 73 is specifically used for: The variable resistor 22 is adjusted to the target resistance value so that the first current loop generates the target current.

[0091] In some embodiments, the current generating device 20 includes a second current device disposed outside the single crystal furnace 40; the diameter control module 73 is specifically used for: The second current device is controlled to generate a first magnetic field, and the second current device is controlled to move in a direction perpendicular to the growth axis of the single crystal 40, so as to form a target current at the solid-liquid interface when the first magnetic field covers the solid-liquid interface.

[0092] In some embodiments, the second current device includes: The first support rods 24 are respectively arranged on both sides of the single crystal 40 furnace, and the slide rails 25 are arranged on the first support rods 24; A magnetic field generating device 26 is slidably connected to a corresponding slide rail 25. The magnetic field generating device 26 is configured to generate a first magnetic field, wherein the magnetic induction intensity of the first magnetic field and / or the moving speed of the magnetic field generating device 26 along the slide rail 25 are configured to adjust the magnitude of the current formed at the solid-liquid interface.

[0093] In some embodiments, the current generating device 20 includes a third current device disposed outside the single crystal furnace 40; the diameter control module 73 is specifically used for: The third current control device induces the target current in the second current loop, wherein the second current loop is formed by connecting the steel wire 30 of the pulled single crystal 40 and the silicon solution 60 through the third loop wire 53.

[0094] In some embodiments, the third current device includes: The number of turns of the magnetic induction coil 28 and / or the rate of change of the input current of the magnetic induction coil 28 are configured to adjust the magnitude of the current induced in the second current loop relative to the second support rod 27 disposed on both sides of the single crystal 40 furnace and the magnetic induction coil 28 disposed on the second support rod 27.

[0095] The single crystal diameter control device of this application determines the target current based on the difference between the current diameter and the target diameter through a preset current calculation model. This enables closed-loop feedback and quantitative control from diameter deviation to current control quantity. By directly applying the target current to the solid-liquid interface of crystal growth, the solid-liquid interface can be quickly and directly intervened, thereby greatly improving the response speed of diameter control, effectively suppressing the diameter change of single crystal 40 caused by the temperature field fluctuation of the solid-liquid interface, and thus improving the accuracy of diameter control and improving the overall diameter control effect in the Czochralski single crystal 40 production process.

[0096] Accordingly, the single crystal diameter control system of this application applies a target current directly to the solid-liquid interface of crystal growth to quickly and directly intervene in the solid-liquid interface, thereby greatly improving the response speed of diameter control, effectively suppressing the diameter change of single crystal 40 caused by the temperature field fluctuation of the solid-liquid interface, thereby improving the accuracy of diameter control and improving the overall diameter control effect in the production process of Czochralski single crystal 40.

[0097] In the above embodiments, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0098] The above provides a detailed description of a single crystal diameter control method, apparatus, and system provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method of controlling the diameter of a single crystal, characterized by, The method comprises: obtaining a current diameter of a single crystal; determining a target current based on the current diameter, a target diameter of the single crystal, and a pre-constructed current calculation model, the current calculation model being used to represent a mapping relationship between a diameter difference and a current; controlling a current generation device to apply the target current to a solid-liquid interface of the single crystal, so as to adjust the current diameter based on the target current.

2. The single crystal diameter control method according to claim 1, wherein The step of constructing the current calculation model comprises: establishing an initial mapping relationship between the diameter of the single crystal and at least one of a current flowing through the solid-liquid interface and a solid-liquid interface thermodynamic correlation parameter based on the Peltier effect; constructing the current calculation model based on the initial mapping relationship.

3. The single crystal diameter control method according to claim 2, wherein The solid-liquid interface thermodynamic correlation parameter comprises at least one of a solid-liquid interface temperature, a solid-liquid interface Seebeck coefficient, a solidification latent heat of the single crystal material, a solid density of the single crystal material, and an axial pulling speed of the single crystal growth.

4. The single crystal diameter control method according to claim 2, wherein The method further comprises: determining a temperature net dissipation amount of the solid-liquid interface based on the current diameter, the target current, and the solid-liquid interface thermodynamic correlation parameter.

5. The single crystal diameter control method according to claim 1, wherein The current generation device comprises a first current device, one end of the first current device being connected to a steel wire for pulling the single crystal through a first loop wire, and the other end of the first current device being connected to a silicon solution through a second loop wire to form a first current loop; The step of controlling the current generation device to apply the target current to the solid-liquid interface of the single crystal comprises: controlling the first current device to output the target current to the solid-liquid interface.

6. The single crystal diameter control method according to claim 5, wherein The first current device comprises a direct current power supply and a variable resistor, and the direct current power supply is configured to output a preset voltage; The step of controlling the first current device to output the target current to the solid-liquid interface comprises: controlling the variable resistor to adjust to a target resistance value, so that the first current loop generates the target current.

7. The single crystal diameter control method according to claim 1, characterized by, The current generation device comprises a second current device, and the second current device is arranged outside the single crystal furnace; The step of controlling the current generation device to apply the target current to the solid-liquid interface of the single crystal comprises: controlling the second current device to generate a first magnetic field, and controlling the second current device to move in a direction perpendicular to an axial direction of the single crystal growth axis, so as to form the target current on the solid-liquid interface under the condition that the first magnetic field covers the solid-liquid interface.

8. The single crystal diameter control method according to claim 7, wherein The second current device comprises: first support rods oppositely arranged on two sides of the single crystal furnace, and a sliding rail arranged on the first support rods; a magnetic field generation device connected to the sliding rail in a sliding manner, and the magnetic field generation device is configured to generate the first magnetic field, wherein a magnetic induction intensity of the first magnetic field and / or a moving speed of the magnetic field generation device along the sliding rail are configured to adjust a current size formed on the solid-liquid interface.

9. The single crystal diameter control method according to claim 1, characterized by, The current generation device comprises a third current device, and the third current device is arranged outside the single crystal furnace; The step of controlling the current generation device to apply the target current to the solid-liquid interface of the single crystal comprises: controlling the third current device to induce the target current in a second current loop, wherein the second current loop is formed by connecting a third loop wire between the steel wire for pulling the single crystal and the silicon solution.

10. The single crystal diameter control method according to claim 9, wherein The third current device comprises: Second support rods oppositely arranged on two sides of the single crystal furnace, and a magnetic induction coil arranged on the second support rods, wherein a number of turns of the magnetic induction coil and / or a change rate of an input current of the magnetic induction coil are configured to adjust a size of a current induced in the second current loop.

11. A single crystal diameter control device, characterized in that, The method comprises: A diameter detection module configured to acquire a current diameter of the single crystal; A current calculation module configured to determine a target current based on the current diameter, a target diameter of the single crystal, and a pre-constructed current calculation model, wherein the current calculation model is used to represent a mapping relationship between a diameter difference and a current; A diameter control module configured to control the current generation device to apply the target current to the solid-liquid interface of the single crystal, so as to adjust the current diameter based on the target current.

12. A single crystal diameter control system, comprising: The system comprises: A central control device configured to perform the single crystal diameter control method according to any one of claims 1-10; A current generation device connected to the central control device and configured to apply a target current to the solid-liquid interface of the single crystal, so as to adjust a current diameter of the single crystal based on the target current.

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