阅读说明：本技术 一种稳定提拉法晶体生长界面的控制装置和方法 (Control device and method for stabilizing crystal growth interface of Czochralski method ) 是由 何晔 周益民 岑伟 陈川贵 于 2019-11-15 设计创作，主要内容包括：本发明属于晶体生长技术领域,为一种稳定提拉法晶体生长界面的控制装置和方法；方法包括实时测量晶体生长的重量,将测量的晶体重量与其理论重量作差,根据两者的差值采用PID控制算法控制晶体生长所需的加热功率；实时测量料棒的重量,并将测量得到的晶体重量与料棒重量之和作为整体重量,根据整体重量与其初始重量的差值,采用PID控制算法控制料棒下降速度；采用CCD旋转装置对CCD光学放大装置进行旋转,光学放大装置实时测量晶体基准线灰度值对应的位置与测量基准线中线的距离,根据该距离与其初始距离的差值采用PID控制算法控制晶体旋转速度；本发明能维持晶体生长界面的稳定,保证晶体外形符合设定尺寸要求。(The invention belongs to the technical field of crystal growth, and relates to a control device and a control method for stabilizing a crystal growth interface of a Czochralski method; the method comprises measuring the weight of crystal growth in real time, subtracting the measured weight of crystal from the theoretical weight of crystal, and controlling the heating power required by crystal growth by PID control algorithm according to the difference between the measured weight of crystal and the theoretical weight of crystal; measuring the weight of the charge bar in real time, taking the sum of the measured weight of the crystal and the weight of the charge bar as the overall weight, and controlling the descending speed of the charge bar by adopting a PID control algorithm according to the difference value of the overall weight and the initial weight of the charge bar; rotating the CCD optical amplifying device by adopting a CCD rotating device, measuring the distance between the position corresponding to the gray value of the crystal reference line and the central line of the measuring reference line by the optical amplifying device in real time, and controlling the rotating speed of the crystal by adopting a PID control algorithm according to the difference value of the distance and the initial distance; the invention can maintain the stability of the crystal growth interface and ensure that the crystal appearance meets the set size requirement.)

1. A control method for stabilizing a crystal growth interface of a Czochralski method is characterized by comprising the following steps:

s1, measuring the weight of the crystal growth in real time, and making a difference between the measured weight of the crystal and the theoretical weight of the crystal; controlling the heating power required by the crystal growth by adopting a PID control algorithm according to the difference value of the two;

s2, measuring the weight of the material rod in real time, and taking the sum of the measured weight of the crystal and the weight of the material rod as the whole weight; controlling the descending speed of the material rod by adopting a PID control algorithm according to the difference value of the whole weight and the initial weight;

and S3, rotating the CCD optical amplifying device by adopting a CCD rotating device, measuring the distance between the position corresponding to the gray value of the crystal reference line and the central line of the measuring reference line by the CCD optical amplifying device in real time, and controlling the rotating speed of the crystal by adopting a PID control algorithm according to the difference value between the distance and the initial distance.

2. The method of claim 1, wherein controlling the heating power required for crystal growth by a PID control algorithm according to the difference between the two comprises controlling the heating power required for crystal growth by a heating power control system according to the following formula:

wherein Δ P represents a heating power supply power adjustment value; p₁、I₁、D₁、T₁Is a PID control parameter, P, of the heating power supply control system₁A proportional control parameter, I, representing the heating power supply control system₁An integral control parameter indicative of the heating power supply control system; d₁A differential control parameter indicative of the heating power supply control system; t is₁A time control parameter indicative of the heating power supply control system; (Δ g)₁)_iRepresents the difference between the actually measured weight of the crystal and the theoretical weight thereof in the ith control period; (Δ g)₁)_i-1Represents the difference between the actually measured weight of the crystal and the theoretical weight of the crystal in the i-1 th control period; (Δ g)₁)_i-2The difference between the actual measured weight of the crystal and the theoretical weight thereof in the i-2 th control cycle is shown.

3. The method as claimed in claim 1, wherein the controlling the descent of the ingot using the PID control algorithm comprises controlling the descent speed of the ingot using a supplemental control system using the following equation:

wherein, is Δ V₂The adjustment quantity is expressed as the descending speed of the material bar; p₂、I₂、D₂、T₂Supplementing the PID control parameter, P, of the control system for the charge bar₂Indicating the charge bar replenishment controlProportional control parameter of the system, I₂An integral control parameter representing the charge bar make-up control system; d₂A differential control parameter indicative of the charge bar make-up control system; t is₂Time control parameters representing the charge bar replenishment control system; Δ q of_iThe difference value of the sum of the weight of the crystal and the weight of the material rod measured in the ith control period and the initial sum of the weight of the material rod is expressed; Δ q of_i-1The difference value of the sum of the weight of the crystal and the weight of the material rod measured in the i-1 th control period and the initial sum of the weight of the material rod is expressed; Δ q of_i-2The difference between the sum of the crystal weight and the weight of the ingot measured in the i-2 control period and the initial sum thereof is shown.

4. The method as claimed in claim 1, wherein the step S3 includes controlling the CCD optical amplifier to rotate by the CCD rotating device until the crystal growth solid-liquid interface is at the center of the window, determining the edge of the crystal from the CCD window as the crystal reference line, and recording the gray value H1; determining the central line of a certain gray value H0 as a measuring reference line according to the crystal type, and recording the initial distance between H0 and H1 as L₀(ii) a Keeping the central line of the measurement reference line unchanged in the CCD window in the whole control process, and recording the distance between the position with the measurement gray value of H1 and the central line of the measurement reference line as L in real time when the control period i is reached_i(ii) a According to (L)_i-L₀) The crystal rotation speed is adjusted by a crystal rotation control system.

5. The method of claim 4, wherein rotating the crystal using the crystal rotation control system comprises controlling using the following equation:

wherein, Δ ω₁An adjustment amount indicating a crystal rotation speed; p₃、I₃、D₃、T₃Is a PID control parameter, P, of the crystal rotation control system₃A proportional control parameter, I, representing the crystal rotation control system₃An integral control parameter indicative of the crystal rotation control system; d₃A differential control parameter indicative of the crystal rotation control system; t is₃A time control parameter indicative of the crystal rotation control system; Δ L_iIndicating the ith control period L_iAnd L₀A difference of (d); Δ L_i-1Indicating the i-1 th control period L_i-1And L₀Difference of (D), L_i-1The distance between the gray value at H1 and the central line of the measurement datum line in the i-1 control period is represented; Δ L_i-2Indicating the i-2 control period L_i-2And L₀Difference of (D), L_i-2The distance between the gray value at H1 and the central line of the measurement reference line in the i-2 control period is shown.

6. A control device for stabilizing a crystal growth interface of a Czochralski method is characterized by at least comprising a heating power supply control system, a charge bar supplement control system and a crystal rotation control system;

the heating power supply control system comprises a first scale, a first control module and an induction heating module; the first scale measures the weight of the growing crystal in real time; the induction heating module provides heat energy required by crystal growth; the first control module adopts a PID control algorithm to control the power of the induction heating module according to the difference value between the measured weight of the growing crystal and the theoretical weight of the crystal;

the charge bar supplementing control system comprises a second scale, a second control module and a stepping motor; the second scale measures the weight of the supplement bar in real time; the stepping motor controls the descending speed of the material rod; the second control module adopts a PID control algorithm to obtain the speed required by the stepping motor and controls the stepping motor to run at the speed;

the crystal rotation control system comprises a CCD optical amplifying device, a CCD rotating device, a third control module and a torque motor; the CCD rotating device controls the CCD optical amplifying device to rotate, and the CCD optical amplifying device acquires the distance between the position corresponding to the gray value of the crystal datum line and the central line of the measuring datum line; and the third control module obtains the rotation speed required by the torque motor by adopting a PID control algorithm according to the difference value between the distance and the initial distance, and controls the torque motor to enable the crystal to rotate at the rotation speed.

7. The control device for stabilizing a crystal growth interface of a Czochralski method as claimed in claim 6, further comprising a housing, a thermal insulation layer, a crucible, a flow guide sleeve and a melt; a plurality of symmetrical material rod holes are formed above the shell, the material rods are fixed on a lifting structure of the stepping motor, and the material rods are controlled to pass through the material rod holes and descend; a crystal hole is formed in the middle of the material rod hole, and a rotating mechanism of the torque motor penetrates through the crystal hole to control the crystal connected in the shell to rotate; the inner wall of the shell is provided with a heat insulation layer, a crucible is arranged in the heat insulation layer, a melt is contained in the crucible, and the upper part of the crucible is provided with a flow guide cover.

8. The control device as claimed in claim 7, wherein the top of the enclosure comprises a partially transparent material through which the CCD optical amplifier partially captures images of the crystal inside the enclosure.

9. The control device for stabilizing a crystal growth interface of a Czochralski method according to claim 6, wherein the induction heating module is a multi-turn induction coil.

Technical Field

The invention belongs to the technical field of crystal growth, and particularly relates to a control device and a control method for stabilizing a crystal growth interface of a Czochralski method.

Background

Crystal growth interface stabilization is an important condition for growing high quality crystals. The currently used full-automatic crystal pulling single crystal furnace uses a high-precision upper weighing system to indirectly measure the actual growth diameter of the crystal, and feeds the actual growth diameter back to a computer control system to control the output power of a heating source, so that the whole crystal can be well controlled to complete the whole growth process according to a preset shape. From the start of seeding to the end of growth, along with the growth of the crystal, the solid-liquid interface of the crystal continuously moves downwards, and at different positions, the growth interface is influenced by comprehensive factors such as crystal heat dissipation change, heat preservation change of a heat preservation system at the position, heating effect change of a heating system at the position and the like, so that the temperature gradient of the growth interface is continuously changed, and as a result, the shape of the growth interface is correspondingly changed, namely, the psi angle in fig. 1 is changed, and the growth interface is unstable in the whole growth process.

An unstable growth interface will affect the uniformity of the internal quality of the entire crystal. Meanwhile, the change of the shape of the growth interface changes the buoyancy force borne by the crystal, influences the weighing system to accurately measure the quality of the crystal and further causes the inaccuracy of the control diameter of the crystal.

Disclosure of Invention

Based on the problems in the prior art, the invention starts from the factor of causing the shape change of the crystal growth interface, and mainly adopts two means, one is to continuously add the crystal growth raw material to enable the melt interface to fluctuate in a tiny interval, thus solving the problem of temperature gradient change caused by the reduction of the melt interface in the traditional control system and being convenient for optical detection of the diameter deviation of the crystal. The second means is to adjust the angle of the growth interface by optically detecting the deviation between the crystal diameter and the theoretical diameter and controlling the rotation speed of the crystal, so that the angle of the growth interface is always maintained to be a small interval fluctuation.

Based on the above, the invention provides a control device and a method for stabilizing a crystal growth interface of a Czochralski method.

A control method for stabilizing a crystal growth interface of a Czochralski method comprises the following steps:

s1, measuring the weight of the crystal growth in real time, and making a difference between the measured weight of the crystal and the theoretical weight of the crystal; controlling the heating power required by the crystal growth by adopting a PID control algorithm according to the difference value of the two;

s2, measuring the weight of the material rod in real time, and taking the sum of the measured weight of the crystal and the weight of the material rod as the whole weight; controlling the descending speed of the material rod by adopting a PID control algorithm according to the difference value of the whole weight and the initial weight;

and S3, rotating the CCD optical amplifying device by adopting a CCD rotating device, measuring the distance between the position corresponding to the gray value of the crystal reference line and the central line of the measuring reference line by the CCD optical amplifying device in real time, and controlling the rotating speed of the crystal by adopting a PID control algorithm according to the difference value between the distance and the initial distance.

In addition, the control device for stabilizing the crystal growth interface of the Czochralski method at least comprises a heating power supply control system, a charge bar supplement control system and a crystal rotation control system;

the heating power supply control system comprises a first scale, a first control module and an induction heating module; the first scale measures the weight of the growing crystal in real time; the induction heating module provides heat energy required by crystal growth; the first control module adopts a PID control algorithm to control the power of the induction heating module according to the difference value between the measured weight of the growing crystal and the theoretical weight of the crystal;

the charge bar supplementing control system comprises a second scale, a second control module and a stepping motor; the second scale measures the weight of the supplement bar in real time; the stepping motor controls the descending speed of the material rod; the second control module adopts a PID control algorithm to obtain the speed required by the stepping motor and controls the stepping motor to run at the speed;

the crystal rotation control system comprises a CCD optical amplifying device, a CCD rotating device, a third control module and a torque motor; the CCD rotating device controls the CCD optical amplifying device to rotate, and the CCD optical amplifying device acquires the distance between the position corresponding to the gray value of the crystal datum line and the central line of the measuring datum line; and the third control module obtains the rotation speed required by the torque motor by adopting a PID control algorithm according to the difference value between the distance and the initial distance, and controls the torque motor to enable the crystal to rotate at the rotation speed.

The invention has the beneficial effects that:

by adopting the control method and the control device provided by the invention, the three sets of control systems can be operated independently, the three sets of control systems can be influenced mutually, the stability of a crystal growth interface can be maintained by comprehensively adjusting P, I, D, T parameters of each control system, crystals with the shapes conforming to the set size can be obtained, and the excellent quality of the crystals can be ensured.

Drawings

FIG. 1 is a prior art Czochralski crystal growth interface apparatus;

FIG. 2 is a flow chart of a method for controlling a crystal growth interface in a stable Czochralski method according to the present invention;

FIG. 3 is a control device for stabilizing the crystal growth interface of Czochralski method according to the present invention;

FIG. 4 is a bottom view of a crystal taken with the crystal rotation control system of the present invention;

FIG. 5 is a view of a window of the present invention after optical magnification of the bottom view of the crystal;

in the figure, 1, a first scale, 2, a second scale, 3, a material rod, 30, a lifting mechanism 4, a crystal, 40, a rotating mechanism, 5, a melt, 6, an induction coil, 7, a heat insulation layer, 8, a crucible, 9, a flow guide cover, 11, a CCD rotating device, 12, a CCD optical amplifying device, 100, a CCD view window, 101, a crystal datum line, 102 and a measurement datum line central line.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly and completely apparent, the technical solutions in the embodiments of the present invention are described below with reference to the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

As shown in fig. 1, the method for controlling a crystal growth interface in a stable czochralski method of the present invention comprises the following steps:

s1, measuring the weight of the crystal growth in real time, and making a difference between the measured weight of the crystal and the theoretical weight of the crystal; controlling the heating power required by the crystal growth by adopting a PID control algorithm according to the difference value of the two;

s2, measuring the weight of the material rod in real time, and taking the sum of the measured weight of the crystal and the weight of the material rod as the whole weight; controlling the descending speed of the material rod by adopting a PID control algorithm according to the difference value of the whole weight and the initial weight;

and S3, rotating the CCD optical amplifying device by adopting a CCD rotating device, measuring the distance between the position corresponding to the gray value of the crystal reference line and the central line of the measuring reference line by the CCD optical amplifying device in real time, and controlling the rotating speed of the crystal by adopting a PID control algorithm according to the difference value between the distance and the initial distance.

In step S1, the controlling the heating power required for the crystal growth by using the PID control algorithm according to the difference between the two includes controlling the heating power required for the crystal growth by using a heating power control system according to the following formula:

wherein Δ P represents a heating power supply power adjustment value; p₁、I₁、D₁、T₁Is a PID control parameter, P, of the heating power supply control system₁A proportional control parameter, I, representing the heating power supply control system₁An integral control parameter indicative of the heating power supply control system; d₁A differential control parameter indicative of the heating power supply control system; t is₁A time control parameter indicative of the heating power supply control system; (Δ g)₁)_iRepresents the difference between the actual measured weight of the crystal and the theoretical weight thereof in the ith control cycle, (Δ g)₁)_iAt the ith control cycle (g)₁-G₁) Value of (a), g₁Denotes the measured weight of the crystal, G₁Is the theoretical weight of the crystal; (Δ g)₁)_i-1Represents the difference between the actually measured weight of the crystal and the theoretical weight of the crystal in the i-1 th control period; (Δ g)₁)_i-2Represents the weight of the crystal actually measured at the i-2 control cycleDifference from its theoretical weight.

According to the control mode of the step S1, the crystal grows according to the designed weight, and the result that the crystal grows according to the preset shape is finally achieved.

In step S2, the controlling the material rod to descend by using the PID control algorithm includes controlling a descending speed of the material rod by using a material rod supplementary control system according to the following formula:

wherein, is Δ V₂The adjustment quantity is expressed as the descending speed of the material bar; p₂、I₂、D₂、T₂Supplementing the PID control parameter, P, of the control system for the charge bar₂Indicating a proportional control parameter of the charge bar supplementary control system, I₂An integral control parameter representing the charge bar make-up control system; d₂A differential control parameter indicative of the charge bar make-up control system; t is₂Time control parameters representing the charge bar replenishment control system; Δ q of_iThe difference value of the sum of the weight of the crystal and the weight of the material rod measured in the ith control period and the initial sum of the weight of the material rod is expressed; Δ q of_i-1The difference value of the sum of the weight of the crystal and the weight of the material rod measured in the i-1 th control period and the initial sum of the weight of the material rod is expressed; Δ q of_i-2The difference value of the sum of the weight of the crystal and the weight of the material rod measured in the (i-2) th control period and the initial sum of the weight of the material rod is expressed; will delta q_iAs a source for adjusting the descending speed of the charge bar, by Δ V₂And adjusting the descending speed of the material rod.

Through the control algorithm, the melt liquid level can be kept stable and hardly fluctuates.

The step S3 includes that the CCD optical amplifying device is controlled to rotate by the CCD rotating device until the crystal growth solid-liquid interface is in the center of the window, the edge of the crystal is determined as the crystal reference line from the CCD window, and the gray value H1 is recorded; determining the central line of a certain gray value H0 as a measuring reference line according to the crystal type, and recording the initial distance between H0 and H1 as L₀(ii) a Keeping the central line of the measurement reference line unchanged in the CCD window in the whole control process, and recording the distance between the position with the measurement gray value of H1 and the central line of the measurement reference line as L in real time when the control period i is reached_i(ii) a According to the distance i (L)_i-L₀) The crystal rotation speed is adjusted by a crystal rotation control system.

The rotating the crystal by the crystal rotation control system comprises controlling by the following formula:

wherein, Δ ω₁An adjustment amount indicating a crystal rotation speed; p₃、I₃、D₃、T₃Is a PID control parameter, P, of the crystal rotation control system₃A proportional control parameter, I, representing the crystal rotation control system₃An integral control parameter indicative of the crystal rotation control system; d₃A differential control parameter indicative of the crystal rotation control system; t is₃A time control parameter indicative of the crystal rotation control system; Δ L_iIndicating the ith control period L_iAnd L₀A difference of (d); Δ L_i-1Indicating the i-1 th control period L_i-1And L₀Difference of (D), L_i-1The distance between the gray value at H1 and the central line of the measurement datum line in the i-1 control period is represented; Δ L_i-2Indicating the i-2 control period L_i-2And L₀Difference of (D), L_i-2The distance between the gray value at H1 and the central line of the measurement reference line in the i-2 control period is shown.

A control device for stabilizing a crystal growth interface of a Czochralski method at least comprises a heating power supply control system, a charge bar supplement control system and a crystal rotation control system;

the heating power supply control system comprises a first scale 1, a first control module and an induction heating module; the first scale measures the weight of the growing crystal 4 in real time; the induction heating module provides heat energy required by crystal growth; the first control module adopts a PID control algorithm to control the power of the induction heating module according to the difference value between the measured weight of the growing crystal and the theoretical weight of the crystal;

the charge bar supplementing control system comprises a second scale 2, a second control module and a stepping motor; the second scale measures the weight of the supplement material rod 3 in real time; the stepping motor controls the material rod to descend; the second control module adopts a PID control algorithm to obtain the speed required by the stepping motor and controls the stepping motor to run at the speed;

the crystal rotation control system comprises a CCD optical amplifying device 12, a CCD rotating device 11, a third control module and a torque motor; the CCD rotating device controls the CCD optical amplifying device to rotate, and the CCD optical amplifying device acquires the distance between the position corresponding to the gray value of the crystal datum line and the central line of the measuring datum line; and the third control module generates the rotating speed required by the torque motor by adopting a PID control algorithm according to the difference value between the distance and the initial distance, and controls the torque motor to enable the crystal to rotate at the rotating speed.

As shown in fig. 3, the apparatus further comprises a housing, a heat insulating layer 7, a crucible 8, a draft shield 9, and a melt 5; a plurality of symmetrical material rod holes are formed above the shell, the material rods are fixed on a lifting structure 30 of the stepping motor, and the material rods are controlled to pass through the material rod holes and descend; a crystal hole is formed in the middle of the material rod hole, and a rotating mechanism 40 of the torque motor penetrates through the crystal hole to control the crystal connected in the shell to rotate; the inner wall of the shell is provided with a heat insulation layer, a crucible is arranged in the heat insulation layer, a melt is contained in the crucible, and the upper part of the crucible is provided with a flow guide cover.

In the present invention, the first scale 1 can obtain the weight of the crystal and send the weight information to the control device, and the control device can judge the consumption of the material in the crucible 8 according to the weight information, so as to control the electric control material guiding device to add the raw material into the crucible 8. The weight of the added raw materials is measured in real time by the second scale 2 and is sent to the control device, the control device compares the difference value of the added amount of the raw materials and the added amount of the crystals, the difference value is used for adjusting the descending speed of the electric control material guiding device to achieve the purpose of adjusting the adding speed of the raw materials, the added weight of the crystals is guaranteed to be basically consistent with the supplement weight of the raw materials, and therefore the dynamic balance of the amount of the raw materials in the crucible 8 is guaranteed.

Wherein the CCD optical amplifying device comprises a CCD camera and an optical amplifier.

In a preferred embodiment, the housing comprises a partially light transmissive material at the top through which the CCD optical magnification device partially captures an image of the crystal inside the housing.

In a preferred embodiment, the induction heating module uses a multi-turn induction coil 6, although other induction heating methods or other existing heating methods may be used.

As shown in fig. 4, the lower view of the crystal collected by the CCD optical magnifying device is divided into a plurality of color regions (the figure only shows black and white line drawings), each region has a different color and therefore has a different gray value, and the color regions include the crystal 4, the melt 5 and the crucible 8 from the inside to the outside; taking the area of the crystal 4 and the melt 5 as a CCD view window 100, wherein a crystal reference line 101 and a measurement reference line central line 102 are divided in the view window; referring to FIG. 5, rotate w₂Until the crystal growth solid-liquid interface is positioned at the center of the window, determining the edge of the crystal from the CCD window as a crystal reference line 101, recording the gray value H1, defining a measurement reference line central line 102 by a certain gray value H0 (related to the crystal type), wherein the central line is kept unchanged in the CCD window in the whole control process, and recording the distance L between H0 and H1₀Repeatedly recording the distance L between the gray value H1 and the central line of the measurement reference line_i(ii) a And rotating the crystal by adopting a crystal rotation control system according to the distance.

The invention continuously adds crystal growth raw materials through the charge bar supplement control system, so that the melt interface fluctuates in a small interval. In addition, the invention also adjusts the angle of the growth interface by controlling the rotation speed of the crystal through a crystal rotation control system based on the deviation between the optical detection crystal diameter and the theoretical diameter, so that the angle of the growth interface is always maintained to be a small interval fluctuation.

It is to be understood that, in order to avoid redundant description, some features of the control method and the control device of the present invention may be mutually cited, and the present invention is not illustrated.

Those skilled in the art will appreciate that all or part of the steps in the methods of the above embodiments may be implemented by associated hardware instructed by a program, which may be stored in a computer-readable storage medium, and the storage medium may include: ROM, RAM, magnetic or optical disks, and the like.

The above-mentioned embodiments, which further illustrate the objects, technical solutions and advantages of the present invention, should be understood that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.