CN107555439A - Polycrystalline silicon growth electric current autocontrol method and device - Google Patents
Polycrystalline silicon growth electric current autocontrol method and device Download PDFInfo
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Abstract
The present invention provides a kind of polycrystalline silicon growth electric current autocontrol method, comprises the following steps：The overall process that charging terminates to stop feeding to reaction since polysilicon is divided into three periods, the respectively first to the 3rd period；Within the first period, pre-set target temperature curve, the output of given electric current is controlled according to actual temperature, so that actual temperature is close to target temperature；Within the second period, given current curve is preset, and the output of given electric current is controlled according to given current curve；Within the 3rd period, given current value is preset, and controls given electric current consistently to export the default given current value.Correspondingly, a kind of polycrystalline silicon growth current auto-controller is also provided.The present invention can automatically control polycrystalline silicon growth electric current, and so as to reduce or even avoid manual operation, and repeatability is high, can adapt to different operating mode and parameter, is easy to adjust and improves.
Description
Technical Field
The invention relates to the technical field of polycrystalline silicon production, in particular to a polycrystalline silicon growth current automatic control method and a polycrystalline silicon growth current automatic control device.
Background
Polycrystalline silicon is a basic material in the solar photovoltaic industry. At present, an improved siemens method (namely a trichlorosilane reduction method) is mainly adopted for producing polycrystalline silicon, and the basic principle is as follows: using SiHCl 3 And H 2 Carrying out vapor deposition reaction in a reducing furnace according to a certain proportion, wherein the reaction temperature is 1000-1100 ℃, and the generated polycrystalline silicon crystal particles are deposited and grown on a silicon core, thereby obtaining the rod-shaped polycrystalline silicon. Wherein the reduction furnace is a reaction vessel for producing polycrystalline silicon.
The main reaction equation for polysilicon production is:
SiHCl 3 +H 2 →Si+3HCl
silicon is known as a semiconductor material, and has conductivity at high temperatures. In the production of polycrystalline silicon, electrodes are required to be arranged on a chassis of a reduction furnace, copper bars are connected below the electrodes, and the copper bars are connected to an electric control cabinet system through a circuit; and a silicon core and a cross beam are arranged above the electrodes so as to form a conductive loop. When current passes through the silicon core, the silicon core can generate heat to provide heat required by reduction reaction in the reduction furnace. In the reaction area of the whole reduction furnace, the surface temperature of the silicon core is the highest, so that the silicon core becomes a carrier for depositing the polycrystalline silicon.
Only part of the heat generated by electrifying the silicon core is used for reduction reaction, and most of the rest is radiated to the surrounding gas phase and then is taken away by heat exchange of materials and heat exchange of water in a furnace barrel. Therefore, in the process of polysilicon growth, an electric control cabinet system is needed to provide the current and voltage required by the polysilicon growth, compensate heat loss and maintain the reaction temperature.
In the actual production, under the influence of material flow, proportion and heat condition in the reduction furnace, the current in the polycrystalline silicon growth process cannot be a fixed value, the current output value of the electric control cabinet system needs to be continuously adjusted manually, the operation is complicated, and the control level and the operation experience of operators are required to be high. Moreover, the repeatability is poor, which is not favorable for regular summarization and adjustment.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art and provides a method and a device for automatically controlling the polycrystalline silicon growth current.
The technical scheme adopted for solving the technical problem of the invention is as follows:
the invention provides a polysilicon growth current automatic control method, which comprises the following steps:
dividing the whole process from the start of feeding the polycrystalline silicon to the end of reaction and stopping feeding into three time periods, namely a first time period to a third time period;
in a first time interval, presetting a target temperature curve, and controlling the output of given current according to the actual temperature so as to enable the actual temperature to approach the target temperature;
in a second time interval, presetting a given current curve, and controlling the output of the given current according to the given current curve;
in the third period, a given current value is preset, and the given current is controlled to constantly output the preset given current value.
The invention also provides a device for automatically controlling the polycrystalline silicon growth current, which comprises:
the dividing unit is used for dividing the whole process from the start of feeding the polycrystalline silicon to the end of reaction and stopping feeding into three time periods, namely a first time period to a third time period;
the first control unit is used for presetting a target temperature curve in a first time interval and controlling the output of given current according to the actual temperature so as to enable the actual temperature to be close to the target temperature;
the second control unit is used for presetting a given current curve in a second time interval and controlling the output of the given current according to the given current curve;
and a third control unit for presetting the given current value and controlling the given current to constantly output the preset given current value in a third period.
Has the advantages that:
the method and the device for automatically controlling the polycrystalline silicon growth current divide the whole process from the start of feeding the polycrystalline silicon to the end of reaction and stop of feeding into three time periods, and adopt different current control modes in different time periods to realize the automatic control of the growth current in the whole process of polycrystalline silicon production, thereby reducing or even avoiding manual operation, having high repeatability, being capable of adapting to different working conditions and parameters and being easy to adjust and improve.
Drawings
Fig. 1 is a flowchart of an automatic control method for polysilicon growth current according to embodiment 1 of the present invention;
FIG. 2 is a graph of time versus target temperature versus given current provided in example 1 of the present invention;
fig. 3 is a schematic view of an automatic control device for polysilicon growth current according to embodiment 2 of the present invention.
In the figure: 100-a partitioning unit; 200-a first control unit; 300-a second control unit; 400-a third control unit; 500-temperature alarm unit; 600-current alarm unit.
Detailed Description
In order to make the technical solutions of the present invention better understood, the present invention is further described in detail below with reference to the accompanying drawings and examples.
Example 1:
as shown in fig. 1, the present embodiment provides a method for automatically controlling a polysilicon growth current, which includes the following steps S101 to S104.
S101, dividing the whole process from the start of feeding the polycrystalline silicon to the end of reaction and stopping feeding into three time periods, namely a first time period to a third time period.
Wherein the first time period is 0-A1 hours, the second time period is A1-A2 hours, and the third time period is A2-A3 hours. As can be seen, 0 is the point in time at which the first period begins; a1 is both the point in time at which the first period ends and the point in time at which the second period begins; a2 is both the point in time at which the second period ends and the point in time at which the third period begins; a3 is a point in time at which the third period ends.
Generally, the time from the start of feeding from polycrystalline silicon to the end of reaction with the termination of feeding is less than 150 hours, so 0-A1-A2-A3-150.
Preferably, 20 is equal to or more than A1 and equal to or less than 70, 50 is equal to or more than A2 and equal to or less than 90, and 80 is equal to or more than A3 and less than 150.
In this example, "reaction" means SiHCl 3 And H 2 The reduction reaction occurring in the reduction furnace requires, in order to ensure sufficient reaction, that the temperature in the furnace reaches an initial preset value, for example 1000 ℃ before the charge, in other words, the time point t at which the first period starts 0 Corresponding target temperature T in the furnace 0 Should equal the initial preset value.
S102, adopting a temperature control current mode: as shown in fig. 2, in the first period (0-A1 hour), a target temperature curve is preset, the actual temperature and the given current are cascade-controlled, and the output of the given current is controlled according to the actual temperature, so that the actual temperature approaches the target temperature.
Specifically, when the actual temperature is higher than the target temperature, the given current is reduced according to the difference between the actual temperature and the target temperature so that the actual temperature is reduced and approaches the target temperature;
when the actual temperature is lower than the target temperature, the given current is increased according to the difference between the target temperature and the actual temperature so that the actual temperature is increased and approaches the target temperature.
Preferably, an infrared thermometer is used for measuring the temperature of the surface of the silicon rod in the reduction furnace through a sight glass on the reduction furnace to obtain the actual temperature. Of course, other thermometric instruments may be used to measure the temperature of the surface of the silicon rod.
In this step, the target temperature curve is represented by x segments connected end to end in sequence, that is, the target temperature curve is approximately expressed as a multi-segment line, wherein the time points are t 0 ,t 1 ,t 2 ,······,t x-1 ,t x The target temperature values corresponding to the time points are respectively T 0 ,T 1 ,T 2 ,······,T x-1 ,T x If the target temperature varies (increases or decreases) in a straight line in a time interval composed of adjacent time points, the expression of the target temperature curve is as follows:
wherein i =0,1,2, x-1; x is more than or equal to 1 and less than or equal to 30; t is the target temperature and T is the time; t is t 0 ＝0，t x ＝A1，T x ＝T A1 A1 is a time point at which the first period ends; t is t 1 ,t 2 ,······,t x-1 ,A1,T 0 ,T 1 ,T 2 ,······,T x-1 ,T A1 Are constants which can be derived from practical experience by those skilled in the art and can also be called empirical values, t 0 ≠t 1 ≠t 2 ≠······≠t x-1 ≠t x 。
It can be seen that the number of line segments used to represent the target temperature curve is divided according to the slope, and the greater the number of line segments, the greater the approximation to the target temperature curve, the more complex the corresponding multi-segment line. Preferably, x is 7, and the target temperature curve is represented by 7 line segments which are connected end to end in sequence (see table 2 for specific examples).
In the step, the purpose of adjusting the given current is to control the actual temperature to be close to the target temperature, so that a control loop is formed among the actual temperature, the target temperature and the given current, the change of the difference value of the actual temperature and the target temperature is directly fed back to the given current, and the given current is quickly and stably adjusted by setting a proper PID (proportion integration differentiation) parameter.
Because the actual temperature is the surface temperature of the silicon rod detected by the infrared thermometer through the sight glass, the accuracy of the actual temperature is influenced by the factors such as the cleanness degree of the sight glass, the measurement error of the infrared thermometer, the alignment direction of the probe of the infrared thermometer and the like, and therefore deviation exists between the measurement value of the infrared thermometer and the actual temperature. In order to avoid that the deviation affects the accuracy of the current control mode in the first period, it is preferable to preset an actual temperature measurement deviation, where the preset actual temperature measurement deviation refers to a deviation between a measurement value of the temperature measuring instrument and an actual temperature, so that the target temperature curve includes the preset actual temperature measurement deviation, thereby eliminating an influence caused by the measurement deviation of the temperature measuring instrument, and a numerical value of the actual temperature measurement deviation can be changed at any time by a person skilled in the art according to an actual situation, so that the operation is convenient.
Accordingly, the expression for the target temperature profile is modified to:
wherein, delta Fruit of Chinese wolfberry The deviation of the actual temperature measurement for the presetting can be derived by the skilled person from actual experience.
In addition, in the process of cascade control of the actual temperature and the given current, if the difference between the actual temperature and the target temperature is too large, it indicates that the temperature control current mode fails, and the current temperature control current mode needs to be exited. Therefore, preferably, a temperature deviation alarm value is preset, and if the absolute value of the difference between the target temperature and the actual temperature exceeds the preset temperature deviation alarm value, an alarm is given, so that the temperature is found to be abnormal in the first time, the temperature control current mode is exited, manual adjustment is changed, and the current temperature of the silicon rod can be maintained, so as to ensure safety. Wherein the preset temperature deviation alarm value range is 10-20 ℃.
S103, adopting a time control current mode: as shown in fig. 2, in the second period (A1-A2 hours), a given current curve is preset, and the output of a given current is controlled according to the given current curve.
In this step, the given current curve is represented by y segments connected end to end in sequence, that is, the given current curve is approximately expressed as a multi-segment line, wherein the time points are t 0 ',t 1 ',t 2 ',······,t y-1 ',t y ' the given current values corresponding to the time points are I 0 ,I 0 +ΔI 1 ,I 0 +ΔI 2 ,······,I 0 +ΔI y-1 ,I 0 +ΔI y In the time interval composed of adjacent time points, the given current varies (increases or decreases) in a straight line, and the expression of the given current curve is as follows:
wherein j =0,1,2, y-1; y is more than or equal to 1 and less than or equal to 30; i is a given current; t' is time; t is t 0 '＝A1，t y '＝A2，I 0 ＝I A1 A1 is the time point at which the second period starts, I A1 A given current value corresponding to the A1 st hour, and A2 is the time point of the end of the second period; a1, t 1 ',t 2 ',······,t y-1 ',A2,I A1 ,ΔI 0 ,ΔI 1 ,ΔI 2 ,······,ΔI y-1 ,ΔI y Are constants which can be derived from practical experience by those skilled in the art and can also be called empirical values, t 0 '≠t 1 '≠t 2 '≠······≠t y-1 '≠t y '。
It can be seen that, in the time-controlled current mode, the given current value I at the time A1 is based on the time A1 (i.e. I) 0 ) The output of a given current is controlled according to a plurality of segments having different slopes for representing a curve of the given current as an initial value. Also, the number of segments used to represent a given current curve is divided according to slope, and the greater the number of segments, the greater the approximation to the given current curve, the more complex the corresponding multi-segment line. Preferably, y is 7, and the given current curve is represented by 7 line segments which are sequentially connected end to end (see table 4 for specific examples).
In the step, in A1-A2 hours (the second time period), the silicon rods are shielded with each other along with the increasing diameter of the polycrystalline silicon, and the sight glass is more fuzzy, so that the measurement error of the infrared thermometer is overlarge, and the temperature control current mode is not applicable. In actual work, the inventor finds that the increasing amplitude of the given current is relatively stable in the period, a multi-segment curve of the given current changing along with the time base, namely the given current curve, can be determined according to an empirical value, and the time control current mode is started.
S104, adopting a constant current mode: as shown in fig. 2, in the third period (A2-A3 hours), a given current value is preset, and the given current is controlled to constantly output the preset given current value.
Preferably, in the third period, the preset given current value is the given current value corresponding to the time point when the second period ends, i.e. I Constant temperature ＝I A2 ＝I 0 +ΔI y ＝I A1 +ΔI y 。
In the step, in A2-A3 hours (the third time interval), the deposition speed of the polycrystalline silicon is accelerated after the polycrystalline silicon enters the later growth stage, and the temperature required by the reaction can be met without increasing the current in the time interval along with the change of the feed flow and the adjustment of the target temperature. Therefore, the constant current mode control is adopted in the later stage of the growth of the polycrystalline silicon, the power consumption of the reduction furnace can be greatly reduced, and the production cost is reduced.
The given currents described in the above steps S102 to S104 are all single-phase given currents. And a plurality of groups of silicon rods are arranged in the reduction furnace, each group of silicon rods corresponds to a given phase current, in other words, the corresponding given phase current is introduced into each group of silicon rods, and the silicon rods in each group of silicon rods are electrically connected in series or in parallel, and the currents introduced into the silicon rods in each group of silicon rods are ensured to be equal. Taking 36 pairs of rod reduction furnaces as an example, 6 silicon rods are provided, each set of silicon rods corresponds to a given current for one phase, and the total of the 6 given currents is 6, while for any 3 of the 6 silicon rods, each set comprises 4 silicon rods (i.e. 8 silicon rods), and for the remaining 3 of the 6 silicon rods, each set comprises 8 silicon rods (i.e. 16 silicon rods).
For each group of silicon rods in the reducing furnace, if the environment in the reducing furnace is not changed greatly and the conditions of each group of silicon rods are approximately the same, the given currents of each phase respectively flowing into each group of silicon rods can be the same. However, under the influence of the distribution change of the flow field and the thermal field in the reduction furnace, the upper ring, the lower ring, the inner ring and the outer ring of each group of silicon rods have temperature differences, and the temperature difference conditions of the silicon rods of each group are different, and if the silicon rods of each group are introduced with the same given current, the actual temperature of the silicon rods of a certain group/certain groups cannot be close to the target temperature, and the expected control effect cannot be achieved. In order to meet different temperature control requirements of the inner ring and the outer ring of each group of silicon rods, preferably, a given current deviation of each phase is preset, each group of silicon rods corresponds to a given current deviation of one phase, the single-phase given current corresponding to each group of silicon rods comprises the preset given current deviation of the corresponding phase, and the value of the given current deviation of each phase can be changed at any time by a person skilled in the art according to actual conditions, so that the given currents of different phases can be controlled respectively.
In addition, rod cracking, arc discharge and the like often occur in the growth process of the polysilicon, so that the difference between the actual current and the given current is too large, and the given current introduced into the silicon rod cannot be maintained. Therefore, it is preferable to preset a warning value of each phase current deviation, and if the absolute value of the difference between the actual current of a certain phase and the given current of the phase exceeds the preset warning value of the phase current deviation, an alarm is given, so that the current abnormality is found at the first time, the current control mode is exited, and the current control mode is changed into manual adjustment. The preset range of the alarm value of the deviation of each phase current is 10-20A, and the alarm values of the deviation of each phase current can be the same or different, and can be specifically set by a person skilled in the art according to the actual situation. The actual current of each phase can be measured by adopting the existing current measuring equipment, for example, the electric control cabinet system has the function of measuring the actual current of each phase.
Two examples of applying the automatic control method of the polycrystalline silicon growth current according to the present embodiment in a 36-pair rod reduction furnace are shown below.
The first example: in a 36-pair rod reduction furnace, a material parameter (see table 1) of a number 015 is used, a temperature control current mode (comprising 7 line segments which are formed by 8 time points and are sequentially connected end to end is adopted within 0-50 hours, the actual temperature and the given current are controlled in a cascade mode, the actual temperature measurement deviation is set to be 10 ℃, and the given current deviation of each phase is set to be 0; and setting the temperature deviation alarm value of the target temperature and the actual temperature to be +/-10 ℃, and setting the current deviation alarm value of each phase of actual current and the given current to be +/-10A. The time-controlled current mode (comprising 7 segments of consecutive line segments formed by 8 time points, see table 2) was used for 50-80 hours. The constant current mode is adopted within 80-100 hours, and the output constant current is a given current value corresponding to 80h (the time point of the end of the second period) (see table 2).
TABLE 1
TABLE 2
The second example: in a 36-pair rod reduction furnace, using the material parameters (see table 3) with the number of 031, adopting a temperature control current mode (comprising 7 segments of line segments which are sequentially connected end to end and are formed by 8 time points and see table 4) within 0-70 hours, carrying out cascade control on the actual temperature and the given current, setting the actual temperature measurement deviation to be 10 ℃, and setting the given current deviation of each phase to be 0; setting the temperature deviation alarm value of the target temperature and the actual temperature as +/-10 ℃, and setting the current deviation alarm value of each phase of actual current and given current as +/-10A. The time-controlled current mode (comprising 7 segments of consecutive line segments formed by 8 time points, see table 4) was used for 70-90 hours. The constant current mode is adopted within 90-110 hours, and the output constant current is a given current value corresponding to the 90h (the time point of the end of the second period) (see table 4).
TABLE 3
TABLE 4
In summary, the method for automatically controlling the polycrystalline silicon growth current according to the embodiment divides the whole process from the start of feeding polycrystalline silicon to the end of reaction and the stop of feeding into three time periods, and adopts different current control modes in different time periods, namely a temperature control current mode, a time control current mode and a constant current mode, so as to adapt to the growth requirements of polycrystalline silicon in different time periods.
Example 2:
as shown in fig. 3, the present embodiment provides an automatic control device for polysilicon growth current, which includes a dividing unit 100, a first control unit 200, a second control unit 300, and a third control unit 400.
The dividing unit 100 is configured to divide the whole process from the start of feeding the polycrystalline silicon to the end of the reaction to stop the feeding into three periods, namely, a first period to a third period.
Wherein the first time interval is 0-A1 hours, the second time interval is A1-A2 hours, and the third time interval is A2-A3 hours. As can be seen, 0 is the point in time at which the first period begins; a1 is both the point in time at which the first period ends and the point in time at which the second period begins; a2 is both the point in time at which the second period ends and the point in time at which the third period begins; a3 is a point in time at which the third period ends.
In general, the time from the start of feeding from polycrystalline silicon to the end of reaction to the stop of feeding is less than 150 hours, so 0-straw A1-straw A2-straw A3-straw 150.
Preferably, 20 is equal to or more than A1 and equal to or less than 70, 50 is equal to or more than A2 and equal to or less than 90, and 80 is equal to or more than A3 and less than 150.
In this example, "reaction" means SiHCl 3 And H 2 The reduction reaction taking place in the reduction furnace, in order to ensure a sufficient reaction, it is necessary to bring the temperature in the furnace to an initial preset value, for example 1000 ℃ before the charge, in other words, the time point t at which the first period starts 0 Corresponding target temperature T in the furnace 0 Should equal the initial preset value.
The first control unit 200 controls the output of the given current by using a temperature control current mode, which is used for presetting a target temperature curve in a first period (0-A1 hour), controlling the output of the given current by cascade connection of the actual temperature and the given current according to the actual temperature, so that the actual temperature approaches the target temperature.
The first control unit 200 is specifically configured to: when the actual temperature is higher than the target temperature, reducing the given current according to the difference between the actual temperature and the target temperature so that the actual temperature is reduced and approaches the target temperature; when the actual temperature is lower than the target temperature, the given current is increased according to the difference between the target temperature and the actual temperature so that the actual temperature is increased and approaches the target temperature.
Preferably, the device further comprises an infrared thermometer, which is used for measuring the temperature of the surface of the silicon rod in the reduction furnace through a sight glass on the reduction furnace to obtain the actual temperature. Of course, other thermometric instruments may be used to measure the temperature of the surface of the silicon rod.
In this embodiment, the preset target temperature curve in the first control unit 200 is represented by x segments connected end to end in sequence, that is, the target temperature curve is approximately expressed as a multi-segment line, where the time points are t 0 ,t 1 ,t 2 ,······,t x-1 ,t x The target temperature values corresponding to the time points are respectively T 0 ,T 1 ,T 2 ,······,T x-1 ,T x If the target temperature varies (increases or decreases) in a straight line in a time interval composed of adjacent time points, the expression of the target temperature curve is as follows:
wherein i =0,1,2, · x-1; x is more than or equal to 1 and less than or equal to 30; t is the target temperature and T is the time; t is t 0 ＝0，t x ＝A1，T x ＝T A1 A1 is a time point at which the first period ends; t is t 1 ,t 2 ,······,t x-1 ,A1,T 0 ,T 1 ,T 2 ,······,T x-1 ,T A1 Are constants which can be derived from practical experience by those skilled in the art and can also be called empirical values, t 0 ≠t 1 ≠t 2 ≠······≠t x-1 ≠t x 。
It can be seen that the number of line segments used to represent the target temperature curve is divided according to the slope, and the greater the number of line segments, the greater the approximation to the target temperature curve, the more complex the corresponding multi-segment line. Preferably, x is 7, and the target temperature curve is represented by 7 line segments which are connected end to end in sequence.
In this embodiment, the purpose of adjusting the given current is to control the actual temperature to approach the target temperature, so that a control loop is formed among the actual temperature, the target temperature, and the given current, the change of the difference between the actual temperature and the target temperature is directly fed back to the given current, and the given current is rapidly and stably adjusted by setting a suitable PID parameter.
Because the actual temperature is the surface temperature of the silicon rod detected by the infrared thermometer through the sight glass, the accuracy of the actual temperature is influenced by the factors such as the cleanness degree of the sight glass, the measurement error of the infrared thermometer, the alignment direction of the probe of the infrared thermometer and the like, and therefore deviation exists between the measurement value of the infrared thermometer and the actual temperature. In order to avoid that the deviation affects the accuracy of the current control mode in the first time period, preferably, the first control unit 200 is further configured to preset an actual temperature measurement deviation, where the preset actual temperature measurement deviation refers to a deviation between a measurement value of the temperature measuring instrument and an actual temperature, so that the target temperature curve includes the preset actual temperature measurement deviation, thereby eliminating an influence caused by the measurement deviation of the temperature measuring instrument, and a value of the actual temperature measurement deviation can be changed at any time by a person skilled in the art according to an actual situation, which is convenient to operate.
Accordingly, the expression of the target temperature profile preset in the first control unit 200 is modified as follows:
wherein, delta Fruit of Chinese wolfberry The deviation of the actual temperature measurement for the presetting can be derived by the skilled person from actual experience.
In addition, in the cascade control process of the actual temperature and the given current, if the difference between the actual temperature and the target temperature is too large, it indicates that the temperature control current mode fails, and the current temperature control current mode needs to be exited. Therefore, preferably, the apparatus further comprises a temperature alarm unit 500, and the first control unit 200 is further configured to preset a temperature deviation alarm value, and if the absolute value of the difference between the target temperature and the actual temperature exceeds the preset temperature deviation alarm value, the temperature alarm unit 500 is controlled to issue an alarm, so that the temperature is found to be abnormal at the first time, the temperature control current mode is exited, manual adjustment is changed, and the current temperature of the silicon rod can be maintained, so as to ensure safety. Wherein the preset temperature deviation alarm value range is 10-20 ℃.
The second control unit 300 controls the output of the given current in a time-controlled current mode for presetting the given current profile and controlling the output of the given current according to the given current profile during the second period (A1-A2 hours).
In this embodiment, the predetermined given current curve in the second control unit 300 is represented by y segments connected end to end in sequence, that is, the given current curve is approximately expressed as a multi-segment line, where the time points are t 0 ',t 1 ',t 2 ',······,t y-1 ',t y ' the given current values corresponding to the time points are I respectively 0 ,I 0 +ΔI 1 ,I 0 +ΔI 2 ,······,I 0 +ΔI y-1 ,I 0 +ΔI y In the time interval composed of adjacent time points, the given current varies (increases or decreases) in a straight line, and the expression of the given current curve is as follows:
wherein j =0,1,2, · y-1; y is more than or equal to 1 and less than or equal to 30; i is given current; t' is time; t is t 0 '＝A1，t y '＝A2，I 0 ＝I A1 A1 is the point in time at which the second time interval begins, I A1 A given current value corresponding to the A1 st hour, and A2 is the time point of the end of the second period; a1, t 1 ',t 2 ',······,t y-1 ',A2,I A1 ,ΔI 0 ,ΔI 1 ,ΔI 2 ,······,ΔI y-1 ,ΔI y Are constants which can be derived from practical experience by those skilled in the art and can also be called empirical values, t 0 '≠t 1 '≠t 2 '≠······≠t y-1 '≠t y '。
It can be seen that the time-controlled current mode adopted by the second control unit 300 is based on time and has a given current value I at the time point A1 A1 (i.e. I) 0 ) The output of a given current is controlled according to a plurality of segments having different slopes for representing a curve of the given current as an initial value. Also, the number of segments used to represent a given current curve is divided according to slope, and the greater the number of segments, the greater the approximation to the given current curve, the more complex the corresponding multi-segment line. Preferably, y is 7, and a given current curve is represented by 7 line segments connected end to end in sequence.
In the embodiment, in the time period from A1 to A2 (the second time period), the silicon rods are shielded from each other along with the increasing diameter of the polycrystalline silicon, and the sight glass is more blurred, so that the measurement error of the infrared thermometer is too large, and the temperature control current mode is not applicable. In actual work, the inventor finds that the increasing amplitude of the given current is relatively stable in the period, a multi-segment curve of the given current changing along with the time base, namely the given current curve, can be determined according to an empirical value, and the time control current mode is started.
The third control unit 400 controls the output of the given current in a constant current mode for presetting the given current value during the third period (A2-A3 hours) and controlling the given current to constantly output the preset given current value.
Preferably, in the third period, the preset given current value is the given current value corresponding to the time point when the second period ends, i.e. I Constant temperature ＝I A2 ＝I 0 +ΔI y ＝I A1 +ΔI y 。
In this embodiment, during A2-A3 hours (the third period), the deposition rate of the polysilicon is increased after the polysilicon has entered the late growth stage, and the temperature required for the reaction can be satisfied without increasing the current during this period along with the change of the supply flow rate and the adjustment of the target temperature. Therefore, the constant current mode control is adopted in the later stage of the growth of the polycrystalline silicon, the power consumption of the reduction furnace can be greatly reduced, and the production cost is reduced.
The given currents described in the above-described first to third control units 200 to 400 are all single-phase given currents. And a plurality of groups of silicon rods are arranged in the reduction furnace, each group of silicon rods corresponds to a given phase current, in other words, the corresponding given phase current is introduced into each group of silicon rods, and the silicon rods in each group of silicon rods are electrically connected in series or in parallel, and the currents introduced into the silicon rods in each group of silicon rods are ensured to be equal.
For each group of silicon rods in the reducing furnace, if the environment in the reducing furnace is not changed greatly and the conditions of each group of silicon rods are approximately the same, the given currents of each phase respectively flowing into each group of silicon rods can be the same. However, under the influence of the distribution change of the flow field and the thermal field in the reduction furnace, the upper ring, the lower ring, the inner ring and the outer ring of each group of silicon rods have temperature differences, and the temperature difference conditions of the silicon rods of each group are different, and if the silicon rods of each group are introduced with the same given current, the actual temperature of the silicon rods of a certain group/certain groups cannot be close to the target temperature, and the expected control effect cannot be achieved. In order to meet different temperature control requirements of the inner ring and the outer ring of each group of silicon rods, preferably, each control unit is further configured to preset a given current deviation of each phase, each group of silicon rods corresponds to a given current deviation of one phase, and the single-phase given current corresponding to each group of silicon rods includes the preset given current deviation of the corresponding phase, and the value of the given current deviation of each phase can be changed at any time by a person skilled in the art according to actual conditions, so as to facilitate the respective control of the given currents of different phases.
In addition, the phenomena of rod cracking, arc discharge and the like often occur in the growth process of the polysilicon, so that the difference between the actual current and the given current is too large, and the given current introduced into the silicon rod cannot be maintained. Therefore, preferably, the apparatus further comprises a current alarm unit 600, and the above-mentioned control units are further configured to preset a current deviation alarm value of each phase, and if the absolute value of the difference between the actual current of a certain phase and the given current of the phase exceeds the preset current deviation alarm value of the phase, the current alarm unit 600 is controlled to issue an alarm, so as to find the current abnormality at the first time, and exit the current control mode, and change the current control mode to manual adjustment. The preset alarm value of each phase current deviation ranges from 10 to 20A, and the alarm values of each phase current deviation may be the same or different, and may be specifically set by those skilled in the art according to actual conditions. The actual current of each phase can be measured by adopting the existing current measuring equipment, for example, the electric control cabinet system has the function of measuring the actual current of each phase.
In summary, the automatic control device for polysilicon growth current described in this embodiment divides the whole process from the beginning of feeding polysilicon to the end of reaction to stop feeding into three time periods, and adopts different current control modes in different time periods, namely a temperature control current mode, a time control current mode and a constant current mode, so as to adapt to the growth requirements of polysilicon in different time periods.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (10)
1. A polysilicon growth current automatic control method is characterized by comprising the following steps:
dividing the whole process from the start of feeding the polycrystalline silicon to the end of reaction and stopping feeding into three time periods, namely a first time period to a third time period;
in a first time interval, presetting a target temperature curve, and controlling the output of given current according to the actual temperature so as to enable the actual temperature to approach the target temperature;
in a second time interval, presetting a given current curve, and controlling the output of the given current according to the given current curve;
in the third period, a given current value is preset, and the given current is controlled to constantly output the preset given current value.
2. The method according to claim 1, wherein the step of controlling the output of the given current in dependence on the actual temperature so that the actual temperature approaches the target temperature is embodied as:
when the actual temperature is higher than the target temperature, reducing the given current according to the difference between the actual temperature and the target temperature so that the actual temperature is reduced and approaches the target temperature;
when the actual temperature is lower than the target temperature, the given current is increased according to the difference between the target temperature and the actual temperature so that the actual temperature is increased and approaches the target temperature.
3. The method of claim 1, wherein the target temperature profile is represented by x segments of line segments connected end to end in sequence, wherein the time points are t 0 ,t 1 ,t 2 ,······,t x-1 ,t x The sequentially corresponding target temperature values are respectively T 0 ,T 1 ,T 2 ,······,T x-1 ,T x Then the expression for the target temperature curve is as follows:
wherein i =0,1,2, x-1; x is more than or equal to 1 and less than or equal to 30; t is the target temperature and T is the time; t is t 0 ＝0，t x ＝A1，T x ＝T A1 A1 is a time point at which the first period ends; t is t 1 ,t 2 ,······,t x-1 ,A1,T 0 ,T 1 ,T 2 ,······,T x-1 ,T A1 Are all constant, t 0 ≠t 1 ≠t 2 ≠······≠t x-1 ≠t x 。
4. Method according to claim 1, characterized in that the given current curve is represented by y segments connected end to end in sequence, wherein the time points are t 0 ',t 1 ',t 2 ',······,t y-1 ',t y ', the given current values corresponding in turn are respectively I 0 ,I 0 +ΔI 1 ,I 0 +ΔI 2 ,······,I 0 +ΔI y-1 ,I 0 +ΔI y Then the expression for a given current curve is as follows:
wherein j =0,1,2, · y-1; y is more than or equal to 1 and less than or equal to 30; i is given current; t' is time; t is t 0 '＝A1，t y '＝A2，I 0 ＝I A1 A1 is the time point at which the second period starts, I A1 A given current value corresponding to the A1 st hour, and A2 is the time point of the end of the second period; a1, t 1 ',t 2 ',······,t y-1 ',A2,I A1 ,ΔI 0 ,ΔI 1 ,ΔI 2 ,······,ΔI y-1 ,ΔI y Are all constant, t 0 '≠t 1 '≠t 2 '≠······≠t y-1 '≠t y '。
5. The method according to any one of claims 1 to 4, wherein the preset given current value is a given current value corresponding to a point in time at which the second period ends, during the third period.
6. An automatic control device for polysilicon growth current is characterized by comprising:
the dividing unit is used for dividing the whole process from the start of feeding the polycrystalline silicon to the end of reaction and stopping feeding into three time periods, namely a first time period to a third time period;
the first control unit is used for presetting a target temperature curve in a first time interval and controlling the output of given current according to the actual temperature so as to enable the actual temperature to be close to the target temperature;
the second control unit is used for presetting a given current curve in a second time interval and controlling the output of the given current according to the given current curve;
and a third control unit for presetting a given current value and controlling the given current to constantly output the preset given current value in a third period.
7. The apparatus according to claim 6, wherein the first control unit is specifically configured to:
when the actual temperature is higher than the target temperature, reducing the given current according to the difference between the actual temperature and the target temperature so that the actual temperature is reduced and approaches the target temperature;
when the actual temperature is lower than the target temperature, the given current is increased according to the difference between the target temperature and the actual temperature so that the actual temperature is increased and approaches the target temperature.
8. The device according to claim 6, wherein the preset target temperature curve in the first control unit is represented by x segments connected end to end in sequence, and the time points are t 0 ,t 1 ,t 2 ,······,t x-1 ,t x The sequentially corresponding target temperature values are respectively T 0 ,T 1 ,T 2 ,······,T x-1 ,T x Then the expression for the target temperature curve is as follows:
wherein i =0,1,2, x-1; x is more than or equal to 1 and less than or equal to 30; t is the target temperature and T is the time; t is t 0 ＝0，t x ＝A1，T x ＝T A1 A1 is a time point at which the first period ends; t is t 1 ,t 2 ,······,t x-1 ,A1,T 0 ,T 1 ,T 2 ,······,T x-1 ,T A1 Are all constant, t 0 ≠t 1 ≠t 2 ≠······≠t x-1 ≠t x 。
9. The device according to claim 6, characterized in that the predetermined current curve preset in the second control unit is represented by y segments connected end to end in sequence, wherein the time points are t 0 ',t 1 ',t 2 ',······,t y-1 ',t y ' and the given current values corresponding in turn are respectively I 0 ,I 0 +ΔI 1 ,I 0 +ΔI 2 ,······,I 0 +ΔI y-1 ,I 0 +ΔI y Then the expression for a given current curve is as follows:
wherein j =0,1,2, y-1; y is more than or equal to 1 and less than or equal to 30; i is a given current; t' is time; t is t 0 '＝A1，t y '＝A2，I 0 ＝I A1 A1 is the time point at which the second period starts, I A1 A given current value corresponding to the A1 st hour, and A2 is the time point of the end of the second period; a1, t 1 ',t 2 ',······,t y-1 ',A2,I A1 ,ΔI 0 ,ΔI 1 ,ΔI 2 ,······,ΔI y-1 ,ΔI y Are all constant, t 0 '≠t 1 '≠t 2 '≠······≠t y-1 '≠t y '。
10. The device according to any one of claims 6 to 9, wherein the preset given current value in the third control unit is the given current value corresponding to the point in time at which the second period ends during the third period.
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| CN113778147A (en) * | 2021-07-23 | 2021-12-10 | 海天塑机集团有限公司 | Method and system for restraining current fluctuation by controlling current output |
| CN114229847A (en) * | 2021-12-15 | 2022-03-25 | 浙江中控技术股份有限公司 | Parameter configuration method and device for polycrystalline silicon reduction furnace, terminal equipment and medium |
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Application publication date: 20180109 Assignee: Xinte silicon based new materials Co.,Ltd. Assignor: XINTE ENERGY Co.,Ltd. Contract record no.: X2022990000325 Denomination of invention: Automatic control method and device of polysilicon growth current Granted publication date: 20190809 License type: Common License Record date: 20220627 Application publication date: 20180109 Assignee: Inner Mongolia Xinte silicon material Co.,Ltd. Assignor: XINTE ENERGY Co.,Ltd. Contract record no.: X2022990000326 Denomination of invention: Automatic control method and device of polysilicon growth current Granted publication date: 20190809 License type: Common License Record date: 20220627 |
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