KR20230153916A - Crystal growth device, method, system and storage media for control of crystal diameter - Google Patents

Abstract

This application provides a crystal growth device, a crystal diameter control method, system, and storage medium. The growth apparatus includes a diameter detection unit, a crucible, a reflector, a heating unit, a crystal lifting unit, a crucible lifting unit, a reflector lifting unit, and a control unit. The control unit calculates the deviation of the distance between the melt surface and the reflector based on the diameter deviation between the real-time diameter of the crystal and the target diameter of the crystal, and adjusts the reflector position based on the distance deviation to change the distance between the melt surface and the reflector. Accordingly, the crystal diameter deviation can be corrected, and the fluctuation of crystal diameter change can be reduced.

Description

Crystal growth device, method, system and storage media for control of crystal diameter}

The present invention relates to the field of crystal growth technology, and in particular to crystal growth devices, methods, systems and storage media for crystal diameter control.

The Czochralski method (CZ method) is a conventional process for single crystal growth. In an argon gas-filled furnace, the polycrystalline silicon material is placed in a quartz crucible, and a graphite heater is used to heat and melt the polycrystalline silicon. A seed crystal is inserted into the melt and rotated. The crucible is rotated in the opposite direction. The seed crystal is slowly pulled up and the neck, shoulder, crown, body, tail, and cooling steps are performed, and an ingot with the desired diameter and length is obtained.

Conventionally, the crystal pulling speed and heating efficiency of a graphite heater can be adjusted to control the diameter of the crystal during the body stage.

However, since the crystal pulling speed directly affects the internal defects of the crystal, the crystal pulling speed must first satisfy the requirements of crystal quality. Based on Vornkov's crystal growth theory, the type of defects inside the crystal is related to the v/G value, where v is the crystal pulling speed (mm/min) and G is the perpendicular to the crystal melt interface of the crystal. is the temperature gradient (K/mm).

Large v/G values will result in the formation of excessive cavities within the crystal above the crystal melt interface. After the crystal cools, excess cavities can accumulate, creating crystal defects known as COPs. If the v/G value is small, excess interstitial silicon atoms will be formed in the crystal above the crystal melt interface, and excess interstitial silicon atoms may accumulate to create crystal defects called dislocations. In order of v/G values from largest to smallest, there are COP domains, OSF domains, PvPi domains (defect-free domains), and translocation domains in the crystal. In the radial cross section of the crystal, the range of v/G values corresponding to the PvPi domain (defect-free domain) is very narrow. Therefore, under the requirements for controlling crystal defects in semiconductor single crystal silicon growth, the variation range of the pulling speed is very narrow.

Adjustment of the deviation of crystal diameter by adjusting the thermal power of the graphite heater has a long time delay due to heat transfer and melt convection. The time lag can be greater than 30 minutes so changes in crystal diameter cannot be corrected in time.

According to the above, it is difficult to control the crystal diameter in a timely and efficient manner by limiting the crystal pulling speed and only adjusting the thermal power of the graphite heater corresponding to the deviation of the crystal diameter. This causes periodic fluctuations in crystal diameter changes. Fluctuations in crystal diameter cause additional severe oscillations of the diameter, making the diameter uncontrollable.

In order to solve the above problems, the present application provides a crystal growth device, a crystal diameter control method, a system, and a storage medium.

According to a first aspect, the present invention provides a crystal growth device, the device comprising:

a diameter detection unit for obtaining the real-time diameter of the crystal;

A crucible for transporting a melt of crystalline material,

A reflector located above the surface of the melt and surrounding the crystals;

a heating unit for heating the crucible,

a decision raising unit for raising the decisions;

a crucible elevating unit that elevates the crucible;

a reflector lifting unit for raising and lowering the reflector;

It includes a control unit connected to a diameter detection unit, a heating unit, a crystal pulling unit, a crucible lifting unit and a reflector lifting unit,

The control unit calculates the deviation of the distance between the melt surface and the reflector based on the deviation of the diameter between the real-time diameter of the crystal and the target diameter of the crystal, and adjusts the distance between the melt surface and the reflector to change the distance between the melt surface and the reflector. Adjust the reflector position based on the deviation in the distance and correct the deviation in the diameter of the crystal.

The distance between the melt surface and the reflector refers to the distance between the melt surface contained in the crucible and the bottom of the reflector, hereinafter also referred to as the “melt gap”.

In one embodiment, the control unit calculates the deviation of the melt gap based on the deviation of the diameter between the real-time diameter of the crystal and the target diameter of the crystal and adjusts the reflector position based on the deviation of the distance between the melt surface and the reflector. Specifically, the control unit for calculation and adjustment is

Input the deviation of the diameter into the first proportional integral derivative (PID) calculation,

Obtaining the deviation of the distance between the melt surface and the reflector based on the first PID algorithm,

It is further configured to control the reflector lifting unit to raise or lower the reflector based on the deviation of the distance between the melt surface and the reflector.

In one embodiment, the control unit

Input the diameter deviation into the second PID algorithm,

Obtaining a deviation in the pulling speed of the decision pulling unit based on the second PID algorithm,

and configured to control the pulling speed of the crystal pulling unit based on the deviation of the pulling speed.

In one embodiment, the control unit

Input the diameter deviation into the third PID algorithm,

Obtaining a deviation in thermal power of the heating unit based on the third PID algorithm,

The thermal power of the heating unit is controlled based on the deviation of the thermal power.

In one embodiment, the device further includes:

A distance detection unit for obtaining the real-time distance between the melt surface and the reflector,

The distance detection unit is connected to the control unit,

The control unit controls the real-time distance between the melt surface and the reflector within the target range.

According to a second aspect, the present application provides a method for controlling crystal diameter comprising the following steps:

obtaining real-time diameters of crystals;

calculating a deviation in diameter between the real-time diameter of the crystal and a target diameter of the crystal;

determining the deviation of the distance between the melt surface and the reflector based on the deviation of the diameter, and

Correcting the deviation of the diameter of the crystal by adjusting the reflector position based on the deviation of the distance between the melt surface and the reflector to change the distance between the melt surface and the reflector.

In one embodiment, adjusting the reflector position based on the variation in distance between the melt surface and the reflector includes:

Inputting the deviation of the diameter into a first proportional integral derivative (PID) calculation;

Obtaining the deviation of the distance between the melt surface and the reflector based on the first PID algorithm, and

and controlling the reflector lifting unit to raise or lower the reflector based on the deviation in distance.

In one embodiment, after calculating the deviation of the diameter between the real-time diameter of the crystal and the target diameter of the crystal, the method further includes the following steps:

Inputting the deviation of the diameter into the second PID algorithm,

Obtaining a deviation in the pulling speed of the crystal pulling unit based on the second PID algorithm, and

Controlling the pulling speed of the crystal pulling unit based on the deviation of the pulling speed.

In one embodiment, after calculating the deviation of the diameter between the real-time diameter of the crystal and the target diameter of the crystal, the method further includes the following steps:

Inputting the deviation of the diameter into the third PID algorithm,

Obtaining a deviation of the thermal power of the heating unit based on the third PID algorithm, and

Controlling the thermal power of the heating unit based on the deviation of the thermal power.

In one embodiment, the method further includes:

Obtaining the real-time distance between the melt surface and the reflector, and

Controlling the real-time distance between the melt surface and the reflector within the target range.

According to a third aspect, the present application provides a system for control of crystal diameter. The system includes a storage device, a processor, and a computer program stored on the storage device. The processor may process a computer program to perform the steps of the method described above.

According to a fourth aspect, the present application provides a computer-readable storage medium storing a computer program. The computer program can be processed by a processor to perform the method steps as previously described.

According to the crystal growth device, crystal diameter control method, system, and storage medium of the present application, the distance between the melt surface and the reflector can be changed by adjusting the position of the reflector, and the crystal diameter can be adjusted. Deviations in crystal diameter can be corrected effectively in a timely manner. This allows for variation in the rate of decision raising within a reasonable range. At the same time, since fluctuations in crystal diameter changes can be suppressed, diameter deviations and crystal inherent defects due to repeated fluctuations in crystal pulling speed and crystal diameter can be prevented.

Figure 1 shows the structure of a crystal growth device according to one embodiment of the present application.
2 is a flow chart illustrating the steps of diameter control in a crystal growth process according to one embodiment of the present application.
Figure 3 shows the heat transfer at the interface between the solid crystal and the melt and the heat flux distribution around the crystal.
Figure 4 shows the variation of crystal diameter in one example and comparative example of the present application.
Figure 5 shows the variation in crystal pulling speed in one example and a comparative example of the present application.
6 is a flowchart illustrating the steps of diameter control in a crystal growth process according to one embodiment of the present application.
Figure 7 shows the structure of a crystal diameter control system according to one embodiment of the present application.

Examples are provided to ensure that the disclosed content is faithful and that the idea of the present invention can be sufficiently conveyed to those skilled in the art. Numerous specific details, such as examples of specific components, devices, and methods, are set forth to provide a thorough understanding of embodiments of the invention. It will be apparent to those skilled in the art that specific details are not required to be employed and that the illustrative embodiments may be embodied in many different forms and none should be construed as limiting the scope of the invention. In some embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

It should be understood that the invention may be practiced in different forms and should not be construed as limiting the scope of the disclosed examples. Rather, the examples are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the spirit of the invention. In the drawings, for clarity, the sizes and relative sizes of layers and regions may be exaggerated. Like reference numbers in the drawings indicate like elements.

Spatially relative terms such as “inside”, “outside”, “below”, “below”, “lower”, “above”, “above”, etc. are used herein to identify different element(s) or features shown in the drawings. May be used for convenience to describe the relationship of one element or feature to part(s). Spatially relative terms may be intended to include other orientations of the device in use or operation in addition to those depicted in the drawings.

The terms used in this specification are merely used to describe specific embodiments and are not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” are intended to include plural forms as well, unless the context clearly dictates otherwise. The terms "comprise", "comprising", "comprising" and "having" are inclusive and therefore specify the presence of the specified feature, integer, step, operation, element and/or component, but also specify the presence of one or more other features, integer, or integer. , does not exclude the presence or addition of steps, tasks, elements, components and/or groups thereof. The method steps, processes and operations described herein are not to be construed as necessarily requiring performance in the specific order discussed or described unless that order of performance is specifically identified. It should also be understood that additional or alternative steps may be employed.

The exemplary embodiments described herein refer to schematic cross-sectional views of ideal embodiments (and intermediate structures) of the invention. Therefore, shape changes can be expected, for example due to manufacturing techniques and/or tolerances. Accordingly, embodiments of the present invention are not limited to the specific shape of the illustrated area and include, for example, variations in shape due to manufacturing. Accordingly, the areas shown in the drawings are schematic in nature and their shapes are not intended to define the actual area of the display device and are not intended to limit the scope of the invention.

For a complete understanding of the present invention, detailed steps will be presented in detail in the following description to explain the technical solutions of the present invention. Preferred embodiments of the present invention are described in detail below, but the present invention may have other embodiments other than the detailed description.

1, a crystal growth device according to one embodiment of the present application is shown.

In this example, the crystal growth device may be a single crystal furnace applied to the growth of single crystal silicon through the CZ method. The crystal growth device includes a furnace 100, a crucible 110, a heater 120, a reflector 130, an insulating layer 140, a crystal pulling unit 150, a crucible lifting unit 160, a diameter detection unit 170, It includes a reflector lifting unit 190 and a control unit 180.

A crucible 110 is disposed within the furnace body 100 to transport polysilicon material. Polysilicon materials are used for the growth of single crystal silicon. Crucible 110 includes a quartz crucible and a graphite crucible. The polysilicon material is contained in a quartz crucible and the graphite crucible is placed outside the quartz crucible.

The heater 120 is located inside the furnace body 100 and is used to heat the crucible 110 to melt the polysilicon material that will become the melt 210 and maintain the melted state. Heater 120 may be a graphite heater, for example.

Reflector 130, also referred to as a “heat shield reflector,” is located on the surface of melt 210 and within furnace body 100 surrounding crystals 200. In one embodiment, reflector 130 has an inverted tapered structure made of graphite material. The reflector 130 adjusts the flow direction and flow rate of the argon gas so that the argon gas injected downward can be concentrated near the growth interface of the crystal 200. In addition, the reflector 130 blocks heat radiation from the melt surface and the crucible 110 to the crystal 200, increases the heat emitted from the surface of the crystal 200 to the surroundings, not only increases the heat transfer rate, but also increases the heat transfer rate of the crystal. Increase the temperature gradient.

The insulation layer 140 is located inside the furnace body 100 and is located between the heater 120 and the furnace body 100 and is used to maintain the temperature inside the furnace. Insulating layer 140 may be carbon felt, for example.

The crystal pulling unit 150, also called a “pulling head”, is fixedly connected to the furnace body 100 to lift and rotate the seed crystal. Crystal pulling unit 150 may also record further process data including crystal weight, displacement of crystal 200, etc. The crystal pulling unit 150 includes, for example, a high-speed motor, a low-speed motor, a rotation motor, a tungsten wire cable, and a seed metering head.

The crucible lifting unit 160 is fixedly connected to the furnace body 100 to lift and rotate the crucible 110. The crucible lifting unit 160 includes, for example, a ball linear guide, a high-precision screw, a lifting motor and a rotation motor.

Diameter detection unit 170 may include a CCD (charge coupled device) camera. An image of the crystal melt interface of crystal 200 is acquired using a CCD camera. Based on the bright ring at the crystal melt interface, the crystal outline is obtained. The crystal outline is fitted to obtain an elliptical boundary, and then the elliptical boundary is corrected to a circular boundary. The coordinates of three or more pixels from the circle border can be taken and applied to the circle coordinate equation to calculate the coordinates and diameter of the circle center. Therefore, the crystal diameter can be obtained.

The reflector lifting unit 190 is fixedly connected to the furnace body 100. The reflector lifting unit 190 may include, for example, a motor and a transmission unit. The motor may be a stepper motor or a servo motor. The motor is connected to the reflector 130 through the transmission part and drives the reflector 130 to rise or fall with respect to the surface of the melt 210.

The control unit 180 may include, for example, a programmable controller (PC) control module and/or a programmable logic controller (PLC) control module. Specifically, the control unit 180 may include a processor, memory, input/output interface, etc. In this example, control unit 180 is connected to diameter detection unit 170, heater 120, crystal lifting unit 150, crucible lifting unit 160 and reflector lifting unit 190. During the growth process of the crystal 200, especially the body growth, the control unit 180 calculates the diameter deviation between the target crystal diameter and the real-time crystal diameter obtained by the diameter detection unit 170, and melts the crystal based on the diameter deviation. The distance deviation of the gap (sometimes referred to hereinafter as “distance deviation”) may be calculated, and the position of the reflector 130 may be adjusted based on the distance deviation to change the distance of the melt gap accordingly. Therefore, the diameter deviation can be corrected, that is, the distance of the melt gap can be changed to adjust the crystal diameter. If the current crystal diameter is larger than the target crystal diameter, the distance can be changed to reduce the crystal diameter. If the current crystal diameter is smaller than the target crystal diameter, the distance can be changed to increase the crystal diameter. Accordingly, the crystal diameter is controlled to be close to the target crystal diameter, and fluctuations in the crystal diameter change are suppressed. In this example, the distance of the melt gap refers to the distance between the liquid surface of the silicon melt 210 in the crucible 110 and the bottom of the reflector 130. Additionally, the control unit 180 can correct the deviation in diameter by adjusting the crystal pulling speed, which is the heating efficiency of the heater 120.

With reference to Figure 2, the crystal diameter control process during crystal growth in the crystal growth apparatus of the present application is explained in detail.

A combination of model-preferred empirical control and real-time feedback control enables crystal diameter control. To guide control, the model preferred experience determines target values of crystal diameter, distance of melt gap, crystal pull speed and thermal power of heater 120 based on the results of operations in previous batches. That is, according to the summary of the work in the previous batch, the target crystal diameter, the target distance of the melt gap, the target crystal pulling speed and the target thermal power are set. In real-time feedback control, real-time data collection of the crystal diameter during the growth process is performed and three PID (Proportional Integral Differential) control loops are applied to adjust the melt gap, crystal pulling speed and thermal power of the heater 120 to reduce the deviation of the diameter. can be corrected.

In the first PID control loop, the deviation of the diameter is input to the first PID algorithm, and the deviation of the distance of the melt gap is obtained based on the first PID algorithm. Then, the reflector lifting unit 190 is controlled to drive the reflector 130 to rise or fall by a distance corresponding to the distance deviation. More specifically, the distance deviation calculated by the first PID algorithm is a correction amount for the current distance of the melt gap (the initial value of the distance is the target distance as described above). The correction amount of the reflector 130 may be a correction distance that must be moved during one control cycle. The control period is the sampling period, i.e., the time interval between two sampling operations for the diameter detection unit 170 to obtain the crystal diameter. The control unit 180 controls the reflector lifting unit 190 to drive the reflector 130 to move the correction distance. Therefore, the surface of the melt 210 can be maintained at a relatively constant position, that is, according to the law of conservation of mass, the mass of the crystal raised per unit time is the same as the mass of the melt 210 whose liquid surface falls. Thereby, the falling speed of the surface of the melt 210 can be confirmed based on the crystal diameter, crystal pulling speed, and crucible size, and the crucible lifting unit 170 raises and lowers the crucible 110 at the falling speed to raise the melt ( 210) causes the surface to be in a relatively constant position. The moving distance of the reflector 130 is equal to the change in distance of the melt gap. By repeating this loop, the distance of the melt gap is continuously adjusted based on the distance deviation. That is, the position of the reflector 130 is continuously adjusted. Accordingly, the deviation in diameter can be corrected. Therefore, the crystal diameter is controlled to be close to the target crystal diameter, and fluctuations in the crystal diameter change are suppressed. The proportional coefficient, integral coefficient, and differential coefficient of the first PID algorithm can be determined by experiment or software simulation.

Referring to Figure 3, the principle is explained in detail.

In crystal growth, latent heat of crystallization is released at the crystal melt interface during the phase transition from liquid silicon to solid silicon. For this purpose, the following heat balance equation is applied, where Qm is the rate of heat transfer from liquid silicon to the liquid side of the crystal-melt interface, Ql is the rate of formation of latent heat of crystallization, and Qs is the rate of heat transfer from the crystal-melt interface to the crystal. am.

Qs=Qm+Ql

In the case of Qs, heat transfer from the crystal melt interface to the crystal mainly occurs through thermal radiation, that is, heat is emitted from the surface of the crystal 200 through thermal radiation. For Qm, the heat transfer rate from liquid silicon to the liquid side of the crystal melt interface is mainly positively correlated with the thermal power of the heater 120, and is also related to the convection mode of the silicon melt 210. For Ql, i.e. the rate of formation of the latent heat of crystallization, the following equation applies:

Ql = L*m = L*(1/4*D2*ð*v)*ρ

where L is the latent heat of silicon crystallization (J/kG), m is the crystal growth rate (kG/min), D is the crystal diameter (mm), ρ is the density of the silicon crystal (kG/mm3), and v is the crystal pulling speed (mm). /minute).

By changing the distance between the melt surface and the reflector, the thermal radiation from the surface of the crystal 200, the distribution h(z) of the heat flux on the crystal surface and the temperature gradient G of the crystal can be varied within a shorter period of time. The rate of heat transfer from the crystal, Qs, can therefore be changed, causing a change in the heat flux, i.e., ΔQ=(Qs-Qm), and changing the rate of formation of the latent heat of crystallization, Ql. Therefore, changes in crystal diameter can be achieved in a shorter time. In conventional crystal diameter control methods, the distance of the melt gap is approximately constant or is gradually increased or decreased based on the length of the crystal. Conventionally, the distance of the melt gap is not adjusted according to the crystal diameter. However, in this example, the distance of the melt gap is adjusted based on the variation in crystal diameter, that is, the position of the reflector 130 is adjusted. In particular, in this embodiment, the distance of the melt gap is not constant. The distance does not increase or decrease incrementally based on crystal length. The distance may vary depending on the change in crystal diameter, i.e., the deviation between the current crystal diameter and the target crystal diameter, which fluctuates near the target distance of the melt gap to compensate for the deviation in diameter.

2, in the second PID control loop, the above deviation of the diameter is input to the second PID algorithm, and the deviation of the pulling speed of the crystal pulling unit 150 is obtained based on the second PID algorithm, and the crystal pulling The pulling speed of unit 150 is adjusted based on the deviation in pulling speed. More specifically, the deviation of the pull-up speed output by the second PID algorithm is a correction amount for the current decision pull-up speed (the initial value of the decision pull-up speed is the target corrected pull-up speed as described above). The current crystal pulling speed may be added to the correction amount to obtain a corrected crystal pulling speed, and the crystal pulling unit 150 is adjusted to obtain the corrected crystal pulling speed. By repeating this loop, the crystal pulling speed is continuously adjusted based on the deviation of the diameter, so that the crystal diameter is controlled to be close to the target crystal diameter, and the fluctuation of the crystal diameter change is suppressed. According to the law of conservation of mass, the mass of the crystal lifted per unit time is equal to the mass of the melt 210 as the liquid surface descends. Thereby, the falling speed of the surface of the melt 210 can be confirmed based on the crystal diameter, crystal pulling speed and crucible size, and the control unit 180 causes the crucible lifting unit 170 to lower the crucible 110 at the above falling speed. is controlled to rise, causing the surface of the melt 210 to be in a relatively constant position. The second PID algorithm may be based on the proportional P term and the differential D term. The proportionality coefficient, integration coefficient, and differentiation coefficient of the second PID algorithm can be determined by experiment or software simulation.

By observing the above heat balance equation and the Ql (formation rate of latent heat of crystallization) equation, if Qs (heat transfer rate of crystal) and Qm (heat transfer rate of liquid) are constant, the crystal pulling rate is negatively correlated with the crystal diameter. have a relationship Therefore, if the crystal diameter is larger than the target value, the crystal pulling speed is increased to reduce the diameter. If the crystal diameter is smaller than the target value, the crystal pulling speed is reduced to increase the diameter. Accordingly, deviations in diameter can be corrected by adjustment of the crystal pulling speed through the second PID control loop.

Referring to FIG. 2, in the third PID control loop, the deviation of the above diameter is input to the third PID algorithm, the thermal power deviation of the heater 120 is obtained based on the third PID algorithm, and the deviation of the heater 120 is obtained. The thermal power (e.g., the thermal power of a graphite heater) is adjusted based on variations in thermal power. More specifically, the deviation of the thermal power output by the third PID algorithm is a correction amount for the current thermal power of the heater 120 (the initial value of the thermal power is the target thermal power as described above). The current thermal power is added to the correction amount to obtain corrected thermal power, and the heater 120 is adjusted to obtain the corrected thermal power. By repeating this loop, the thermal power is continuously adjusted according to the deviation of the diameter, so that the crystal diameter is controlled to be close to the target crystal diameter, and the fluctuation of the crystal diameter change is suppressed. The proportionality coefficient, integration coefficient, and differentiation coefficient of the third PID algorithm can be determined by experiment or software simulation.

Since thermal power is positively correlated with Qm (heat transfer rate of liquid), a change in thermal power results in a change in Qm, resulting in a difference in heat flow rate, i.e. a change in ΔQ=(Qs-Qm), and the rate of formation of latent heat of crystallization. Causes a change in Ql. Therefore, the crystal diameter changes. Therefore, the diameter deviation can be corrected by adjusting the thermal power of the heater 120 through the third PID control loop.

In the above diameter control process, the first PID control loop can be applied to correct the diameter deviation by adjusting the distance between the melt and the reflector, thereby effectively narrowing the adjustment range of the crystal pulling speed in the second PID control loop. You can. If the range of change in crystal pulling speed is reasonable, the fluctuation of crystal diameter change can be suppressed, diameter deviation can be prevented, the inherent defects of crystals caused by repeated oscillations of crystal pulling speed and crystal diameter can be avoided, and product yield can be improved. It can be improved. In these PID control loops, response to changes in crystal diameter can be achieved by the second PID control loop, the first PID control loop, and the third PID control loop from high speed to low speed.

With reference to comparative examples and examples of the present application, the technical effect of the diameter control process is explained in detail.

In the comparative example, the crystal growth device applies a horizontal superconducting magnetic field with a magnetic field strength of 4000G. A 32-inch crucible is used to transport 400 kg of polysilicon material. This device can be used to produce semiconductor ingots with a diameter of 310 mm and a length of 2000 mm. The distance between the melt and the reflector is controlled to 40 mm. During the body stage, the target crystal pull speed is 0.55 mm/min and the target crystal diameter is 310 mm. Because of the crystal defect-free control requirement, the variation range of the pulling speed v should be within ±10%. The target range of crystal diameter is 310 ±1.0 mm. In this comparative example, the second PID control loop and the third PID control loop are applied for diameter deviation correction.

In the embodiment of the present application, a horizontal superconducting magnetic field with a magnetic field strength of 4000G is applied. A 32-inch crucible is used to transport 400 kg of polysilicon material. A semiconductor ingot with a diameter of 310 mm and a length of 2000 mm is produced. The target distance of the melt gap is controlled to be 40 mm. During the body stage, the target crystal pull speed is 0.55 mm/min and the target crystal diameter is 310 mm. Because of the crystal defect-free control requirement, the variation range of the pulling speed v should be within ±10%. The target range of crystal diameter is 310 ±1.0 mm. In this example, the above-described first PID control loop, second PID control loop, and third PID control loop are applied for correction of the deviation of the diameter.

Among the 10 ingots in the comparative example, 4 ingots had diameter deviations greater than ±1.0 mm in certain sections of the ingot. Among these four ingots, two ingots have diameter deviations greater than ±3.0 mm. The part of the ingot with such fluctuations exceeds 400 mm, which reduces product quality and adversely affects product yield.

In the 10 ingots of the example, all ingots had smooth surfaces and the diameter deviation was less than ±1.0 mm. The variation in crystal pulling speed is within the target range. There are no defects in crystals within the target portion of the ingot. Product yield improves.

Figure 4 shows the variation of crystal diameter in Examples and Comparative Examples. Figure 5 shows variations in crystal pulling speed in Examples and Comparative Examples. According to the figure, the variations in crystal diameter and crystal pulling speed of the examples are obviously smaller than those of the comparative examples.

In this example, the crystal growth device further includes a diameter detection unit. The diameter detection unit includes a CCD camera for acquiring images of the liquid surface of melt 210. Depending on the reflected image of the reflector 130 on the liquid surface of the melt 210 or the reflected image of the indicator of the reflector 130 on the liquid surface of the melt 210, the distance between the reflector 130 and the melt 210, i.e. , the distance of the melt gap can be known. According to the distance of the melt gap obtained by the diameter detection unit, the control unit 180 limits the range of adjustment by the first PID control loop, so that the adjusted distance by the first PID control loop is the target of the melt gap. It does not exceed a certain percentage of the distance, such as ±10% of the target distance, meaning that the distance of the melt gap remains within an acceptable range of the target distance, such as 90%-110% of the target distance. More specifically, each time the first PID algorithm calculates and outputs the distance deviation, whether the sum of the distance deviation and the current distance of the melt gap exceeds the range of the target distance, for example, 90%-110% of the target distance. It is decided whether or not If the sum exceeds the target distance range, the position of the reflector 130 is not adjusted according to the output distance deviation.

In some embodiments, for the diameter control process during crystal growth, any one or two of the first PID control loop, the second PID control loop, and the third PID control loop as described above are used to correct for deviations in crystal diameter. It can be applied.

Referring to Figure 6, the present application also provides a method for control of crystal diameter based on the above crystal growth apparatus and adapted to control the diameter of the crystal during the growth process, particularly the body growth stage. The method includes the following steps S1-S3.

Step S1 includes obtaining the real-time diameter of the crystal.

In one embodiment, the diameter detection unit 170 of the crystal growth device is used to capture the current diameter of the crystal. Diameter detection unit 170 may be a CCD camera. A CCD camera acquires images of the crystal melt interface. The crystal diameter is obtained based on the bright ring of the crystal melt interface in the image. The diameter detection unit 170 is set to periodically acquire the crystal diameter. After the crystal diameter is obtained the next steps will be performed.

Step S2 includes calculating the diameter deviation between the real-time diameter of the crystal and the target diameter of the crystal.

Step S3 determines the deviation of the distance of the melt gap based on the deviation of the diameter, and adjusts the position of the reflector 130 based on the deviation of the distance of the melt gap to change the distance of the melt gap, thereby changing the diameter of the crystal. It includes correcting the deviation of . The distance of the melt gap refers to the distance between the surface of the melt 210 in the crucible 110 and the bottom of the reflector 130.

In one embodiment, step S3 includes the following steps:

Step S31: Inputting the deviation of the diameter into the first PID algorithm, and obtaining the deviation of the distance of the melt gap based on the first PID algorithm. The proportional coefficient, integral coefficient, and differential coefficient of the first PID algorithm can be determined by experiment or software simulation.

Step S32: Controlling the reflector lifting unit 190 to raise or lower the reflector 130 by a distance corresponding to the distance deviation. The distance deviation is a correction amount for the current distance of the melt gap (the initial value of the distance is the target distance as described above). The correction amount for the reflector 130 may be a correction distance that must be moved during one target control cycle. The control unit 180 controls the reflector lifting unit 190 to drive the reflector 130 to move the correction distance.

In steps S31-S32, the surface of the melt 210 may be maintained at a relatively constant position, that is, according to the law of conservation of mass, the mass of the crystal raised per unit time and the mass of the melt 210 from which the liquid surface descends are the same. do. Thereby, the falling speed of the surface of the melt 210 can be confirmed based on the crystal diameter, crystal pulling speed, and crucible size, and the crucible lifting unit 170 raises and lowers the crucible 110 at the falling speed to raise the melt ( 210) causes the surface to be in a relatively constant position. The moving distance of the reflector 130 is equal to the change in distance between the melt surface and the reflector.

In steps S31-S32, the liquid surface of the melt 210 may be at target positions of various stages of the growth process, which means that the position of the liquid surface of the melt 210 may change. For example, the position of the liquid surface of melt 210 can be raised or lowered regularly by changing the rate of raising and lowering the crucible. At the same time, the result is requested by adding or subtracting the distance deviation obtained from the first PID algorithm from the rising or falling distance of the liquid surface of the melt 210, and the result is obtained by adding or subtracting the distance deviation obtained from the first PID algorithm to the reflector 130 driven by the reflector lifting unit 190. is the moving distance of

After step S2, the method further includes the following steps.

Step S41: Inputting the deviation of the diameter into the second PID algorithm, and obtaining the deviation of the pulling speed of the crystal pulling unit 150 based on the second PID algorithm. The second PID algorithm may be based on the proportional P term and the differential D term. The proportional coefficient, integral coefficient, and differential coefficient of the second PID algorithm can be determined through experiment or software simulation. The deviation of the crystal pulling speed output by the second PID algorithm is a correction amount for the current crystal pulling speed (the initial value of the crystal pulling speed is the target corrected pulling speed as described above).

Step S42: Controlling the pulling speed of the crystal pulling unit 150 based on the deviation of the pulling speed. The corrected pull speed is obtained by adding the correction amount of the pull speed to the current determined pull speed. By controlling the crystal pulling unit 150, the current crystal pulling speed is adjusted to the corrected speed.

After step S2, the method further includes the following steps.

Step S51: Inputting the deviation of the diameter into the third PID algorithm, and calculating the deviation of the heating power of the heating unit 120 based on the third PID algorithm. The proportionality coefficient, integration coefficient, and differentiation coefficient of the third PID algorithm can be determined by experiment or software simulation. The deviation of the thermal power output by the third PID algorithm is a correction amount for the current thermal power of the heater 120 (the initial value of the thermal power is the target thermal power as described above).

Step S52: Controlling the thermal power of the heater 120 based on the deviation of the thermal power. The current thermal power is added to the correction amount to obtain corrected thermal power, and the heater 120 is adjusted to obtain the corrected thermal power.

In this example, after step S2, steps S31-S32, S41-S42 and S51-S52 are performed simultaneously. By simultaneously applying three PID control loops (1st PID control loop: S31-S32, 2nd PID control loop: S41-S42, and 3rd PID control loop: S51-S52), deviation in crystal diameter can be corrected. there is. As another example, after step S2, one or two of steps S31-S32, S41-S42, and S51-S52 may be performed.

In this example, the control method further includes the following steps:

Step S61: Obtaining the real-time distance between the melt surface and the reflector, that is, the real-time distance of the melt gap.

More specifically, the real-time distance of the melt gap is obtained by the diameter detection unit of the crystal growth device. The diameter detection unit includes a CCD camera for acquiring images of the liquid surface of melt 210. Depending on the reflected image of the reflector 130 on the liquid surface of the melt 210 or the reflected image of the indicator of the reflector 130 on the liquid surface of the melt 210, the distance between the reflector 130 and the melt 210, i.e. , the real-time distance of the melt gap can be known.

Step S62: Controlling the real-time distance of the melt gap within the target range.

Each time, while the first PID algorithm calculates and outputs the distance deviation, it is determined whether the sum of the distance deviation and the current distance of the melt gap exceeds the range of the target distance, e.g., 90%-110% of the target distance. . If the sum exceeds the target distance range, the position of the reflector 130 is not adjusted according to the output distance deviation. That is, the adjustment range of the first PID control loop is limited to ensure that the adjusted distance of the melt gap through steps S31-S32 does not exceed a certain percentage of the target distance, for example, does not exceed ±10% of the target distance. .

7 illustrates the structure of a crystal diameter control system 300 according to one embodiment of the present application. Crystal diameter control system 300 includes a storage device 310 and a processor 320.

The storage device 310 stores program code for implementing the corresponding steps of the crystal diameter control method in the above embodiment.

The processor 320 processes the program code stored in the storage device 310 to implement the corresponding steps of the crystal diameter control method in the above embodiment.

The present application further provides a computer-readable storage medium. A computer-readable storage medium stores program instructions. The program instructions are processed by a computer or processor to implement the corresponding steps of the crystal diameter control method in the above embodiments. Computer-readable storage media include, for example, a storage unit of a tablet computer, a hard disk of a personal computer, Read-Only Memory (ROM), Erasable Programmable Read-Only Memory (EPROM), and portable compact disk read-only memory (CD-ROM). only memory), USB memory, or any combination thereof. A computer-readable storage medium may be a storage medium readable by a single computer or a combination of storage media readable by multiple computers.

The description of the foregoing embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, may be interchanged with and used in selected embodiments even if not specifically shown or described. The same thing can vary in many ways. Such variations should not be considered a departure from the present disclosure, and all such modifications are intended to be included within the scope of the present disclosure. The scope of the present invention is defined by the appended claims and their equivalents.

Those skilled in the art may recognize that the example units or algorithm steps of the above-described embodiments may be implemented by hardware, software, or a combination of hardware and software. Implementation by hardware or software depends on the specific application of the technical solution and design constraints. Those skilled in the art may implement the described functionality by applying a variety of means to a variety of specific applications. Such implementation should not be considered as extending beyond the scope of the present invention.

It should be understood that the unit division of the module described above is only a division of logical functions. During actual implementation, all or part of the units may be integrated into a physical entity or may be physically separated. Additionally, these units may all be implemented in the form of software called by processing elements, all of them may be implemented by hardware, or some units may be implemented in the form of software called by processing elements, and some units may be implemented in the form of software called by processing elements. can be implemented in hardware. For example, a processor may be a separately placed processing element or may be integrated into a chip of the device. Alternatively, a processor may be stored in the memory of the device as a program and called by processing elements of the device to perform the functions of the device. The implementation of other units is similar. Additionally, all or part of these units may be integrated or implemented separately. The processing element here may be an integrated circuit with signal processing capabilities. In the implementation process, the steps of the above-described method or the above-described module may be completed using instructions in the form of software or hardware integrated logic circuits of a processor element.

Examples are provided to ensure that the disclosed content is faithful and that the idea of the present invention can be sufficiently conveyed to those skilled in the art. Numerous specific details, such as examples of specific components, devices, and methods, are set forth to provide a thorough understanding of embodiments of the invention. It will be apparent to those skilled in the art that specific details are not required to be employed and that the illustrative embodiments may be embodied in many different forms and none should be construed as limiting the scope of the invention. In some embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

In order to simplify the disclosure and assist in understanding one or more inventive aspects, in the foregoing description of exemplary embodiments of the disclosure, features of the disclosure are sometimes grouped into a single embodiment or figure, or description thereof. You must understand that it will happen. However, the manner of the present disclosure should not be construed as reflecting the following intent: that is, to require that the disclosure claim protection have more features than are explicitly set forth in each claim. Or rather, as reflected in the following claims, aspects of the invention aim at less than all features of a single embodiment disclosed above.

Those skilled in the art will recognize that all features disclosed herein (including the appended claims, abstract and drawings) and any process or unit are not mutually exclusive, unless at least some of such features and/or processes or units are mutually exclusive. I can understand. Any of the disclosed methods or devices can be combined using any combination. Unless otherwise specified, each feature disclosed in this specification (including the appended claims, abstract, and drawings) may be replaced by a replacement feature serving the same, equivalent, or similar purpose.

Additionally, a person skilled in the art will understand that, even if the embodiments described herein include some features included in other embodiments rather than other features, a combination of features in different embodiments is meant to be included in the scope and form of the present invention. You will be able to. For example, any one of the embodiments protected by the claims below may be used in any combination.

The above-described embodiments are not intended to limit the present invention, but rather are a description of the present invention, and those skilled in the art can design alternative embodiments without departing from the scope of the appended claims. “Include” does not exclude elements or steps not stated in the claims. The word “a” or “one” placed in front of an element does not exclude the presence of multiple such elements. The invention may be implemented by hardware comprising various other components and a suitably programmed computer. In device claims that list multiple devices, some devices may appear to use the same hardware. The use of words such as “first,” “second,” and “third” do not indicate order.

Claims (10)

As a crystal growth device,
a diameter detection unit for obtaining the real-time diameter of the crystal;
A crucible for transporting a melt of crystalline material,
A reflector located above the surface of the melt and surrounding the crystals;
a heating unit for heating the crucible,
a decision raising unit for raising the decisions;
a crucible elevating unit that elevates the crucible;
a reflector lifting unit for raising and lowering the reflector;
It includes a control unit connected to a diameter detection unit, a heating unit, a crystal pulling unit, a crucible lifting unit and a reflector lifting unit,
The control unit calculates the deviation of the distance between the melt surface and the reflector based on the deviation of the diameter between the real-time diameter of the crystal and the target diameter of the crystal, and adjusts the distance between the melt surface and the reflector to change the distance between the melt surface and the reflector. A crystal growth device that adjusts the reflector position based on the deviation of the distance and corrects the deviation of the diameter of the crystal. 2. The control unit according to claim 1, wherein the control unit for calculation and adjustment is
Input the deviation of the diameter into the first proportional integral derivative (PID) calculation,
Obtaining the deviation of the distance between the melt surface and the reflector based on the first PID algorithm,
The crystal growth device is further configured to control the reflector lifting unit to raise or lower the reflector based on the deviation of the distance. According to paragraph 1,
The control unit inputs the deviation of the diameter into the second PID algorithm, obtains the deviation of the pulling speed of the crystal pulling unit based on the second PID algorithm, and determines the pulling speed of the crystal pulling unit based on the deviation of the pulling speed. configured to control,
and/or
The control unit is configured to input the deviation of the diameter into the third PID algorithm, obtain the deviation of the thermal power of the heating unit based on the third PID algorithm, and control the thermal power of the heating unit based on the deviation of the thermal power. A crystal growth device. According to paragraph 1,
It further includes a distance detection unit for obtaining the real-time distance between the melt surface and the reflector,
The distance detection unit is connected to the control unit,
A crystal growth device, where the control unit controls the melt gap in real time within a target range. As a crystal diameter control method,
obtaining real-time diameters of crystals;
calculating a deviation in diameter between the real-time diameter of the crystal and a target diameter of the crystal;
determining the deviation of the distance between the melt surface and the reflector based on the deviation of the diameter, and
A crystal diameter control method comprising: correcting the deviation of the diameter of the crystal by adjusting the reflector position based on the deviation of the distance between the melt surface and the reflector to change the distance between the melt surface and the reflector. The method of claim 5, wherein adjusting the reflector position based on the deviation of the distance between the melt surface and the reflector comprises:
Inputting the deviation of the diameter into a first proportional integral derivative (PID) algorithm,
Obtaining the deviation of the distance between the melt surface and the reflector based on the first PID algorithm, and
A method for controlling a crystal diameter, comprising controlling a reflector lifting unit to raise or lower the reflector based on the variation in distance. 6. The method of claim 5, wherein after calculating the diameter deviation between the real-time diameter of the crystal and the target diameter of the crystal,
Inputting the deviation of the diameter into a second PID algorithm, obtaining a deviation of the pulling speed of the crystal pulling unit based on the second PID algorithm, and pulling the crystal pulling unit based on the deviation of the pulling speed. controlling the speed,
and/or
Inputting the deviation of the diameter into a third PID algorithm, obtaining a deviation of the heating power of the heating unit based on the third PID algorithm, and controlling the heating power of the heating unit based on the deviation of the heating power. A crystal diameter control method further comprising: According to clause 5,
Obtaining the real-time distance between the melt surface and the reflector, and
A method for controlling a crystal diameter, further comprising controlling the real-time distance between the melt surface and the reflector within a target range. A crystal diameter control system comprising a storage device, a processor, and a computer program stored in the storage device, wherein the processor processes the computer program to carry out the steps of the method according to claim 5. A computer-readable storage medium storing a computer program, wherein the computer program is processed by a processor to carry out the steps of the method according to claim 5.