A method for feeding a single crystal furnace circulation section

Abstract

The application discloses a single crystal furnace feeding method, before feeding, the remaining material quantity in the single crystal furnace before feeding is calculated to obtain the preheating time, the preheating time is associated with the ideal preheating time, the power deviation value and the remaining material quantity deviation value, so that the obtained preheating time can conform to the size of the current remaining material quantity and the size of the working power, and the interval time between the adjacent two feedings corresponding to the current feeding quantity during the current split feeding is calculated, the interval time is also associated with the power deviation value and the feeding quantity deviation value, so that the interval time corresponding to each feeding is more accurate, and the single crystal furnace state is not unified or the silicon leakage accident occurs caused by artificial control of the preheating time and the feeding interval time or setting of the fixed feeding interval time and the preheating time.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of photovoltaic technology, and in particular to a method for feeding materials in the circulation section of a single crystal furnace. Background Technology

[0002] The Czochralski (Cz) method is a commonly used crystal growth method. It involves heating and melting silicon in a single crystal furnace, then immersing a rod-shaped seed crystal into the melt. This allows silicon atoms in the melt to form regular crystals at the solid-liquid interface along the arrangement of silicon atoms on the seed crystal, thus forming a single crystal. Specifically, the Czochralski method typically includes the following process steps: temperature control, crystal pulling, shoulder formation, shoulder rotation, equal diameter formation, tailing, and feeding.

[0003] When extracting the crystal rod for the first time and feeding it into the single crystal furnace again, preheating is required before feeding to ensure that the temperature inside the single crystal furnace reaches the preset value. In related technologies, different preheating times need to be manually modified for different feeding amounts, and the time interval between two feedings is fixed. When the bottom heater is turned off after feeding is completed, the intracranial condition needs to be observed manually and the bottom heater needs to be turned off manually.

[0004] Because different single crystal furnaces have different heat preservation performance, the amount of remaining material before feeding, the preheating power, and the feeding time are not uniform, resulting in different preheating times and feeding intervals. If a fixed preheating time and interval are set, there is a risk of silicon leakage accidents. Furthermore, because the state inside the single crystal furnace is not uniform, the timing of shutting off the bottom heater is not fixed. Therefore, the operation of feeding and temperature adjustment based on the operator's judgment of the furnace condition requires a high level of skill from the operator. There is also a possibility of inaccurate timing of the next step during the process, and a lot of human resources are wasted by manual observation. Summary of the Invention

[0005] This invention provides a feeding method for the circulation section of a single crystal furnace, aiming to automate the calculation and judgment of steps that require manual judgment during the feeding process of single crystal silicon.

[0006] This invention provides a method for feeding materials in the circulation section of a single crystal furnace, which may include:

[0007] Based on the actual amount of residual material in the single crystal furnace, the preset preheating adjustment coefficient, the ideal preheating time calibrated for the single crystal furnace, the power deviation value, and the residual material deviation value, a target preheating time matching the actual amount of residual material is determined; the power deviation value is determined by the ideal working power and the actual working power of the single crystal furnace, and the residual material deviation value is determined by the ideal amount of residual material and the actual amount of residual material in the single crystal furnace;

[0008] After the single crystal furnace is preheated according to the target preheating time, the interval between two adjacent feedings is determined based on the preset melting interval adjustment coefficient, the feeding amount deviation value, and the power deviation value when the single crystal furnace is fed in multiple batches; the feeding amount deviation value is determined by the ideal feeding amount of the single crystal furnace, the actual feeding amount, the ideal interval time, and the minimum interval time.

[0009] Add materials at the specified intervals to complete the feeding process.

[0010] Optionally, the operating power of the single crystal furnace includes the preheating power of the preheating stage and the crystal pulling power of the crystal pulling stage;

[0011] The method further includes:

[0012] Obtain the ideal preheating power, ideal crystal pulling power, actual preheating power, and actual crystal pulling power of the single crystal furnace, wherein the actual crystal pulling power is the power of the single crystal furnace during the previous crystal rod pulling process.

[0013] The difference between the ideal preheating power and the ideal crystal-leading power is taken as the ideal difference value, and the difference between the actual preheating power and the actual crystal-leading power is taken as the actual difference value. The ratio of the ideal difference value to the actual difference value is taken as the power deviation value.

[0014] Optionally, the method further includes:

[0015] The bottom heater of the single crystal furnace is turned off after a waiting period, calculated from the moment the material is started to be added.

[0016] Optionally, the step of shutting off the bottom heater of the single crystal furnace after a waiting period includes: multiplying the melting coefficient by the total amount of material added to obtain a first product;

[0017] When the current running time of the single crystal furnace is less than or equal to a first time threshold, the first product is used as the waiting time, and the bottom heater is turned off after the waiting time ends.

[0018] When the current running time of the single crystal furnace is greater than the first time threshold, the difference between the current running time and the first time threshold is taken as the first difference value, and the first difference value is multiplied by a preset correction adjustment coefficient to obtain a second product; the difference between the first product and the second product is taken as the waiting time, and the bottom heater is turned off after the waiting time.

[0019] Optionally, the method further includes: for a preset total feeding amount, calculating the total feeding time corresponding to the single crystal furnace under different feeding conditions;

[0020] Calculate the average feeding time based on the total feeding time mentioned above;

[0021] The ratio of the average feeding time to the preset total feeding amount is used as the melting coefficient.

[0022] Optionally, the method further includes: when the amount of residual material in the current single crystal furnace is within a preset range of residual material, then proceeding to the step of determining a target preheating time that matches the actual amount of residual material based on the actual amount of residual material in the single crystal furnace, a preset preheating adjustment coefficient, an ideal preheating time calibrated for the single crystal furnace, a power deviation value, and a residual material deviation value;

[0023] When the amount of material remaining in the current single crystal furnace is not within the preset range of the amount of material remaining, the preset fixed preheating time is used as the target preheating time.

[0024] Optionally, the method further includes: obtaining a first preheating time for the single crystal furnace with a first amount of residual material under standard thermal conditions, and a second preheating time for the single crystal furnace with a second amount of residual material; wherein the first amount of residual material and the second amount of residual material are different values;

[0025] The preheating adjustment coefficient is determined based on the first preheating time, the first remaining material amount, the second preheating time, and the second remaining material amount.

[0026] Optionally, the method further includes: obtaining a first interval time for the single crystal furnace to feed a first amount of material under standard thermal conditions, and a second interval time for the single crystal furnace to feed a second amount of material; wherein the first amount of material and the second amount of material are different values;

[0027] The value of the melting interval adjustment coefficient is determined based on the second interval time, the first interval time, the first feeding amount, the second feeding amount, and the preset minimum interval time.

[0028] Optionally, after the feeding is completed, the method further includes:

[0029] Obtain a brightness value image of the material inside the single crystal furnace, the material including solids and liquids, the brightness values ​​of the solids and liquids at corresponding positions in the brightness value image are different;

[0030] Based on the brightness value image, the proportion of liquid in the material in the brightness value image is determined, and the bottom heater is turned off when the liquid proportion is greater than or equal to a preset ratio.

[0031] Optionally, the method further includes:

[0032] After shutting down the bottom heater of the single crystal furnace, the temperature inside the single crystal furnace is adjusted.

[0033] The single-crystal silicon rod prepared in the single-crystal furnace is obtained by sequentially performing crystal pulling, shoulder forming, and equal diameter forming operations.

[0034] Optionally, the temperature control process within the single crystal furnace includes:

[0035] Obtain the brightness value of the liquid inside the single crystal furnace;

[0036] Compare the brightness value with a preset brightness value range;

[0037] When the brightness value is within the preset brightness value range, the temperature adjustment process is controlled to enter the temperature stabilization process;

[0038] When the brightness value is not within the preset brightness value range, the power of the main heater is increased;

[0039] When the brightness value exceeds the upper limit of the preset brightness value range, the power of the main heater is automatically adjusted, thereby regulating the liquid surface temperature.

[0040] In summary, this invention discloses a method for feeding materials in the circulation section of a single crystal furnace. Before feeding, the preheating time is determined by calculation based on the amount of material remaining in the furnace before feeding. This preheating time is correlated with the ideal preheating time, power deviation, and remaining material deviation, ensuring that the obtained preheating time matches the current amount of remaining material and the operating power. Furthermore, the interval between two consecutive feedings corresponding to the current feeding amount is calculated and correlated with the power deviation and feeding amount deviation, making the interval for each feeding more accurate. This avoids inconsistencies in the furnace's state or silicon leakage accidents caused by manually controlling the preheating time and feeding interval or setting fixed feeding and preheating times. The method automatically calculates the time to shut down the bottom heater using the melt coefficient or automatically determines the timing of shutting down the bottom heater based on the brightness value, making the method of shutting down the bottom heater more consistent and timely. Compared to manually shutting down the bottom heater, this saves time and manpower. Attached Figure Description

[0041] Figure 1 This is a flowchart of a single crystal furnace circulation section feeding method provided in an embodiment of the present invention;

[0042] Figure 2 This is a flowchart of another method for feeding materials in the circulation section of a single crystal furnace provided in this embodiment of the invention;

[0043] Figure 3 This is a comparison chart of the waiting time for shutting down the bottom heater provided in an embodiment of the present invention;

[0044] Figure 4 This is a complete process diagram of preparing a single-crystal silicon rod provided in an embodiment of the present invention;

[0045] Figure 5 This is a comparison chart of the brightness values ​​of solids and liquids provided in an embodiment of the present invention. Detailed Implementation

[0046] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0047] Figure 1 This is a flowchart illustrating the steps of a single crystal furnace circulation section feeding method provided in an embodiment of the present invention, including:

[0048] Step 101: Based on the actual amount of residual material in the single crystal furnace, the preset preheating adjustment coefficient, the ideal preheating time calibrated for the single crystal furnace, the power deviation value, and the residual material deviation value, determine the target preheating time that matches the actual amount of residual material; the power deviation value is determined by the ideal working power and the actual working power of the single crystal furnace, and the residual material deviation value is determined by the ideal amount of residual material and the actual amount of residual material in the single crystal furnace.

[0049] In this embodiment of the invention, after the initial feeding of the single crystal furnace and the extraction of the crystal rod, the furnace is at a low temperature. At this point, the power needs to be increased to raise the furnace temperature to meet the melting conditions for subsequent feedings. Without preheating, crystallization within the furnace could lead to silicon leakage. During the cyclic feeding process, preheating is only performed before the first feeding; subsequent feedings do not require preheating. The target preheating time represents the preheating time before the first feeding.

[0050] The preheating time required before adding material varies depending on the amount of material remaining in the single crystal furnace, the furnace's heat preservation performance (reflected by the crystal pulling power), and the furnace's preheating power. Since the heat required to preheat different weights of material remaining in the furnace differs, the target preheating time corresponding to the current actual amount of material remaining in the single crystal furnace can be calculated using a preset preheating adjustment coefficient, the ideal preheating time calibrated for the single crystal furnace, the power deviation value, and the material remaining amount deviation value.

[0051] Specifically, the target preheating time required for the current amount of material remaining in the furnace can be calculated using the following first preset formula:

[0052]

[0053] Where t1 is the target preheating time, α1 is the preheating adjustment coefficient, T is the ideal preheating time, m is the actual remaining material amount, M is the ideal remaining material amount, P1 is the rational preheating power under the ideal working power, P2 is the rational crystal-leading power under the ideal working power, P3 is the actual preheating power under the actual working power, and P4 is the actual crystal-leading power under the actual working power. If the preset coefficient α1 is 0.9, the ideal preheating time T is 30 minutes, the ideal remaining material amount M is 235 kg, the ideal preheating power P1 is 150 kW, the rational crystal-leading power P2 is 63 kW, the actual remaining material amount m is 285 kg, the actual preheating power P3 is 150 kW, and the actual preheating power P4 is 64 kW, then the target preheating time t1 corresponding to the actual remaining material amount m of 285 kg can be calculated to be 33.1 minutes.

[0054] Furthermore, the ideal preheating time and ideal working power are reference values ​​obtained under standard thermal field conditions. By calculating the deviation between the actual residual material amount and the ideal residual material amount and the actual working power and ideal working power, and combining the preset preheating adjustment coefficient, the target preheating time corresponding to the actual residual material amount is determined, making the determination of the target preheating time corresponding to the actual residual material amount more accurate and solving the uncertainty of human judgment of preheating time based on experience.

[0055] Step 102: After the single crystal furnace is preheated according to the target preheating time, the interval between two adjacent feedings is determined according to the preset melting interval adjustment coefficient, the feeding amount deviation value and the power deviation value. The feeding amount deviation value is determined by the ideal feeding amount of the single crystal furnace, the actual feeding amount, the ideal interval time and the minimum interval time.

[0056] In this embodiment of the invention, during a single cycle of feeding, silicon material is added to the crucible in small increments. Furthermore, the next feeding can only proceed after the previous batch of silicon material has melted. The interval between two feedings is the melting interval time. For different feeding amounts, the time interval between each feeding is different. Moreover, the time interval between two feedings is also affected by the operating power of the single-crystal furnace. Therefore, when calculating the melting interval adjustment, the interval time between two adjacent feedings during the single-crystal furnace's multi-stage feeding can be determined based on a preset melting interval adjustment coefficient, feeding amount deviation value, and power deviation value.

[0057] Specifically, the interval between two consecutive feedings can be calculated using the second preset formula below:

[0058]

[0059] Where t2 is the interval between two feedings, α2 is the preset melting interval adjustment coefficient, t0 is the ideal interval, t1 is the minimum interval, m0 is the ideal feeding amount, m1 is the actual feeding amount, and the definitions of P1, P2, P3, and P4 are the same as those in step 102. Based on the preset α2, t1, m0, t0, P1, P2 and the actual m1, P3, and P4, the interval corresponding to the feeding amount of m1 can be calculated using the second preset formula.

[0060] Furthermore, under standard thermal conditions, the ideal interval time is the average interval between two actual feedings during multiple feedings, and the ideal feeding amount is the average feeding amount per feeding during multiple feedings. The preset ideal interval time and ideal feeding amount are obtained through statistical analysis. The minimum interval time is the minimum interval between two actual feedings, which ensures that the previous feeding melts during multiple feedings. Using the values ​​under ideal conditions as reference values ​​for calculating the interval time, by calculating the deviation between the actual feeding amount and the ideal feeding amount, as well as the power deviation, and combining this with the preset melting interval adjustment coefficient, the interval time corresponding to the actual feeding amount can be determined. This makes the determination of the interval time corresponding to the actual feeding amount more accurate, solving the problem of inaccurate feeding interval determination caused by manual feeding based on experience. With the melting interval adjustment coefficient α2 set to a preset value of 0.9, the ideal interval time t0 being 35 min, the minimum interval time t1 being 25 min, the ideal feed amount m0 ​​being 70 kg, the actual feed amount m1 being 65 kg, the ideal preheating power P1 being 150 KW, the ideal crystal-leading power P2 being 63 KW, the actual remaining material amount m being 285 kg, the actual preheating power P3 being 150 KW, and the actual preheating power P4 being 64 KW, it can be calculated that when the feed amount is 65 kg, the interval time is approximately 31 min.

[0061] Step 103: Add material according to the specified interval to complete the material addition.

[0062] In this embodiment of the invention, the feeding of the cyclic section is automatically performed according to the calculated interval time. After multiple feedings are completed, the bottom heater is turned off according to preset conditions. After the bottom heater is turned off, the subsequent preparation process such as temperature adjustment and crystal pulling is entered.

[0063] In summary, this invention discloses a method for feeding a single crystal furnace. Before feeding, the preheating time is determined by calculating the amount of material remaining in the single crystal furnace before feeding. The preheating time is correlated with the ideal preheating time, the power deviation value, and the deviation value of the amount of material remaining, so that the obtained preheating time can conform to the current amount of material remaining and the working power. Furthermore, the interval time between two adjacent feedings corresponding to the current feeding amount is calculated. The interval time is also correlated with the power deviation value and the feeding amount deviation value, making the interval time corresponding to each feeding more accurate. This avoids the inconsistency of the state inside the single crystal furnace or silicon leakage accidents caused by manually controlling the preheating time and feeding interval time or setting a fixed feeding interval time and preheating time.

[0064] Figure 2 This is a flowchart illustrating the steps of another method for feeding a single crystal furnace in a circulating section, as provided in this embodiment of the invention, including:

[0065] Step 201: Based on the actual amount of residual material in the single crystal furnace, the preset preheating adjustment coefficient, the ideal preheating time calibrated for the single crystal furnace, the power deviation value, and the residual material deviation value, determine the target preheating time that matches the actual amount of residual material; the power deviation value is determined by the ideal working power and the actual working power of the single crystal furnace, and the residual material deviation value is determined by the ideal amount of residual material and the actual amount of residual material in the single crystal furnace.

[0066] This step can be referred to in step 101, and will not be repeated here.

[0067] Optionally, the operating power of the single crystal furnace includes the preheating power of the preheating stage and the crystal pulling power of the crystal pulling stage. Step 201 specifically includes:

[0068] Sub-step 2011: Obtain the ideal preheating power, ideal crystal pulling power, actual preheating power, and actual crystal pulling power of the single crystal furnace, wherein the actual crystal pulling power is the power of the single crystal furnace during the previous crystal rod pulling.

[0069] In this embodiment of the invention, the ideal preheating power and ideal crystal-leading power of the single crystal furnace are the power under a standard thermal environment, while the actual preheating power and actual crystal-leading power are the actual preheating power and actual crystal-leading power of the current single crystal furnace.

[0070] Sub-step 2012: The difference between the ideal preheating power and the ideal crystal-leading power is taken as the ideal difference value, and the difference between the actual preheating power and the actual crystal-leading power is taken as the actual difference value. The ratio of the ideal difference value to the actual difference value is taken as the power deviation value.

[0071] In this embodiment of the invention, the difference between the ideal preheating power and the ideal crystal-driving power is used to represent the power difference under ideal conditions, and the difference between the actual preheating power and the actual crystal-driving power is used to represent the power difference under actual working conditions. The ratio of the ideal difference to the actual difference is used as the power deviation value, which reflects the deviation of the actual working power of the single crystal furnace from the ideal state.

[0072] Optionally, step 201 specifically includes:

[0073] Sub-step 2013: When the amount of remaining material in the current single crystal furnace is within the preset range of remaining material, proceed to step 201;

[0074] In this embodiment of the invention, in order to prevent silicon leakage accidents caused by excessively short preheating time or crucible bulging accidents caused by excessively long preheating time, a preset range of residual material is set when automatically calculating the preheating time. The calculation method of the preheating time is determined by comparing the residual material with the preset range of residual material.

[0075] Specifically, if the amount of remaining material is within a preset range, the target preheating time is calculated using step 101. The preset range of remaining material can be 300KG to 400KG.

[0076] Sub-step 2014: If the amount of material remaining in the current single crystal furnace is not within the preset amount of material remaining, then the preset fixed preheating time shall be used as the target preheating time.

[0077] In this embodiment of the invention, if the amount of remaining material is not within the preset range, that is, if the amount of remaining material is less than 300, the preset fixed preheating time, such as 30 minutes, is used as the target preheating time.

[0078] If the amount of remaining material is not within the preset range and the amount of remaining material is greater than 400, the preset fixed preheating time, such as 40 minutes, will be used as the target preheating time.

[0079] By setting a preset range for the amount of residual material, the method of calculating the target preheating time using the first preset formula becomes more adaptable and automated.

[0080] Optionally, step 201 specifically includes:

[0081] Sub-step 2015: Obtain the first preheating time of the single crystal furnace for the first remaining material amount and the second preheating time of the single crystal furnace for the second remaining material amount under the same thermal field conditions; the first remaining material amount and the second remaining material amount are different values;

[0082] In this embodiment of the invention, in order to determine the preheating adjustment coefficient, the preheating time corresponding to the first amount of residual material and the second amount of residual material can be obtained under the same thermal field conditions, and then calculated in combination with the first preset formula.

[0083] Sub-step 2016: Determine the preheating adjustment coefficient based on the first preheating time, the first remaining material amount, the second preheating time, and the second remaining material amount.

[0084] Specifically, the ratio of the product of the first preheating time and the amount of remaining material to the product of the first amount of remaining material and the second preheating time is used as the preheating adjustment coefficient.

[0085] The formula for calculating the preheating adjustment coefficient is as follows:

[0086]

[0087] Where α1 is the preheating adjustment coefficient, t1 is the second preheating time, t2 is the first preheating time, M is the first residual material amount, and m is the second residual material amount.

[0088] In this embodiment of the invention, since it is under standard thermal field conditions, there is no power deviation value. Substituting the product of the first preheating time and the second remaining material amount and the product of the first remaining material amount and the second preheating time into the above formula, the preheating adjustment coefficient can be obtained. The calculation of the target preheating time is corrected by the preheating adjustment coefficient. For example, if the second preheating time t1 is 35 min, the first preheating time t2 is 30 min, the first remaining material amount M is 235, and the second remaining material amount m is 300, the preheating adjustment coefficient α1 is calculated to be 0.9.

[0089] Step 202: After the single crystal furnace is preheated according to the target preheating time, the interval between two adjacent feedings is determined according to the preset melting interval adjustment coefficient, the feeding amount deviation value and the power deviation value. The feeding amount deviation value is determined by the ideal feeding amount of the single crystal furnace, the actual feeding amount, the ideal interval time and the minimum interval time.

[0090] This step can be referred to as step 102, and will not be repeated here.

[0091] Optionally, step 202 specifically includes:

[0092] Sub-step 2021: Obtain the first interval time for the single crystal furnace to feed the first amount of material and the second interval time for the single crystal furnace to feed the second amount of material under the same thermal field conditions; the first amount of material and the second amount of material are different values;

[0093] Sub-step 2022: Determine the value of the melting interval adjustment coefficient based on the second interval time, the first interval time, the first feeding amount, the second feeding amount, and the preset minimum interval time.

[0094] Specifically, the formula for calculating the melting interval adjustment coefficient is as follows:

[0095]

[0096] Wherein, α2 is the melting interval adjustment coefficient, t2 is the second interval time, t0 is the first interval time, t1 is the preset minimum interval time, m0 is the first feeding amount, and m1 is the second feeding amount.

[0097] In this embodiment of the invention, the melting interval adjustment coefficient can be calculated using the formula for calculating the melting interval adjustment coefficient. The obtained first feeding amount, first interval time, second feeding amount, and second interval time are substituted into the formula to calculate the melting interval adjustment coefficient. The melting interval adjustment coefficient is a correction coefficient for calculating the interval time.

[0098] Furthermore, if the first feeding amount is 70kg and the first interval is 35min, the second feeding amount is 60kg and the second interval is 30min, the preset minimum interval is 25min.

[0099] Based on the above formula, the melting interval adjustment coefficient can be calculated to be 0.9.

[0100] Step 203: Calculate from the start of feeding time, and shut down the bottom heater of the single crystal furnace after the waiting time.

[0101] In this embodiment of the invention, a certain time interval is required between the start of feeding and the shutdown of the bottom heater to allow the material in the single crystal furnace to fully melt. The waiting time is the melting time of the molten material in the single crystal furnace.

[0102] Step 203 specifically includes:

[0103] Sub-step 2031: Multiply the melting coefficient by the total amount of material added to obtain a first product; when the current running time of the single crystal furnace is less than or equal to a first time threshold, use the first product as the waiting time, and turn off the bottom heater after the waiting time ends;

[0104] In this embodiment of the invention, since the temperature inside the single crystal furnace rises after the single crystal furnace has been running for longer than the first time threshold, there will be a delay in the timing of shutting down the bottom heater. Therefore, the timing when the delay in shutting down the bottom heater will occur can be determined as the first time threshold.

[0105] When the single crystal furnace running time is less than the first time threshold, the timing for shutting down the bottom heater will not be delayed. Therefore, the waiting time for shutting down the bottom heater can be determined by calculating the product of the melting coefficient and the total charge. If the melting coefficient is 0.5 and the total charge is 200, then the waiting time for shutting down the bottom heater is 100 minutes.

[0106] Sub-step 2032: When the current running time of the single crystal furnace is greater than the first time threshold, the difference between the current running time and the first time threshold is taken as the first difference value, and the first difference value is multiplied by a preset correction adjustment coefficient to obtain a second product; the difference between the first product and the second product is taken as the waiting time, and the bottom heater is turned off after the waiting time.

[0107] In this embodiment of the invention, when the current running time of the single crystal furnace is greater than a first time threshold, a delay in shutting down the bottom heater occurs. This indicates that the waiting time calculated solely based on the melting time and total feeding time is longer than the actual time required to shut down the bottom heater. In this case, a preset correction adjustment coefficient is introduced to determine the waiting time for the bottom heater.

[0108] Specifically, the preset correction adjustment coefficient can be obtained by statistically analyzing the time when the bottom heater is turned off when the actual running time exceeds the first time threshold. For example, if in reality, when the running time exceeds the first time threshold, the time when the bottom heater is turned off will be delayed by four minutes for every additional 100 hours, then the preset correction adjustment coefficient can be calculated as 4 / 100 = 0.04.

[0109] Further, Table 1 below shows the values ​​corresponding to the following when the charge amount changes: unadjusted melting time (calculated based on the melting coefficient and total charge amount), partially slope-adjusted melting time (obtained by adjusting the melting coefficient corresponding to certain total charge amounts in practice), and the corrected melting time after reaching 200 hours. The values ​​in the table are calculated based on a melting coefficient of 0.5, a first time threshold of 200, and an actual single-crystal furnace running time of 250. The calculated waiting times corresponding to each total charge amount are shown in Table 1. In practice, when calculating the waiting time corresponding to a portion of the total charge amount, the melting coefficient corresponding to that portion of the total charge amount is adjusted accordingly. The adjusted value is shown in the column for waiting times with partially slope adjustments in Table 1. The specific adjustment magnitude of the melting coefficient can be set according to the actual situation, and this embodiment of the invention does not limit this.

[0110]

[0111] Table 1

[0112] refer to Figure 3 , Figure 3The graph shows a comparison of waiting time (melting time) under different calculation methods. The graph does not show the case where the single crystal furnace running time is less than the first time threshold, and the graph shows the case where the single crystal furnace running time is greater than the first time threshold after correction. The slope of the graph corresponds to the case after adjusting the melting coefficient. It can be seen that after correction, the waiting time corresponding to the total amount of material added is reduced, thus avoiding the situation where the waiting time is unduly extended.

[0113] Optionally, after step 203, the method further includes:

[0114] Step 204: After turning off the bottom heater of the single crystal furnace, adjust the temperature inside the single crystal furnace.

[0115] In this embodiment of the invention, after shutting down the bottom heater of the single crystal furnace, the crucible rotation speed inside the furnace is increased, and the heat exchanger is reduced to its lower limit. The operator then positions the liquid outlet according to standard procedures. Temperature adjustment is then performed, including pre-adjustment and formal temperature adjustment. The purpose of temperature adjustment is to determine the seed crystal's welding temperature. Pre-adjustment stabilizes the temperature before formal temperature adjustment, while formal temperature adjustment ensures a stable and uniform temperature inside the furnace, thus determining suitable temperature conditions for subsequent crystal pulling operations.

[0116] Optionally, step 204 specifically includes:

[0117] Sub-step 2041: Obtain the brightness value of the liquid inside the single crystal furnace.

[0118] In this embodiment of the invention, a CCD (charge coupled device) camera can be used to globally capture and scan images inside the single crystal furnace. The pixel values ​​of the obtained images can be determined, and the pixel values ​​of the images can be converted into brightness values ​​to obtain the brightness values ​​of the liquid inside the single crystal furnace. The brightness values ​​can be used as reference values ​​for temperature adjustment.

[0119] Sub-step 2042: Compare the brightness value with a preset brightness value range.

[0120] In this embodiment of the invention, during the preparation stage before the crystal pulling operation, it is necessary to ensure that the liquid temperature inside the single crystal furnace is within a suitable range, and that the brightness value of the liquid inside the furnace reflects its temperature. If the brightness value deviates from the preset range, the power of the main heater is adjusted accordingly to bring the liquid temperature within the appropriate range. Specifically, a predetermined temperature range can be obtained according to actual needs, and then converted into a corresponding brightness value range, which can then be used as the predetermined brightness value range. This embodiment of the invention does not limit the preset brightness value range.

[0121] Furthermore, the actual measured brightness value is compared with the preset brightness value range, and the power of the main heater can be adjusted based on the difference.

[0122] Sub-step 2043: When the brightness value is within the preset brightness value range, control the temperature adjustment process to enter the temperature stabilization process.

[0123] In this embodiment of the invention, when the brightness value is within the preset brightness value range, it indicates that the pre-temperature adjustment temperature has reached the preset value. At this time, it will not immediately enter the formal temperature adjustment stage, but will enter the pre-temperature stabilization stage. Only when the rate of change of liquid surface temperature is less than the preset value within a fixed time will it enter the formal temperature adjustment stage. For example, when the rate of change of brightness within 3 minutes is less than 0.3, the formal temperature adjustment will be performed.

[0124] Sub-step 2044: When the brightness value is not within the preset brightness value range, automatically adjust the power of the main heater, thereby adjusting the liquid surface temperature.

[0125] In this embodiment of the invention, when the brightness value is less than the preset brightness value range, the power of the main heater is automatically adjusted, thereby adjusting the liquid surface temperature and controlling the liquid surface temperature to reach the preset temperature value range.

[0126] The obtained brightness value allows for automated and accurate adjustment of the main heater power, improving temperature stability.

[0127] Optionally, after step 204, the method further includes:

[0128] Step 205: After turning off the bottom heater of the single crystal furnace, the temperature inside the single crystal furnace is adjusted; the crystal pulling operation, shoulder forming operation, and equal diameter operation are performed in sequence to obtain the single crystal silicon rod prepared by the single crystal furnace.

[0129] In this embodiment of the invention, after temperature adjustment, crystal pulling, shoulder forming, and equal diameter forming operations can be performed until a single crystal silicon rod is obtained.

[0130] refer to Figure 4 , Figure 4To illustrate the complete process of preparing single-crystal silicon rods, the preheating time of the single-crystal furnace is calculated and preheating is performed before the first feeding in the circulating section. After preheating, the circulating feeding begins. Preheating only occurs before the first feeding; subsequent feedings do not require preheating. After preheating, feeding begins, and each subsequent feeding is performed at intervals. Once the total feeding amount is reached, feeding is complete, and the heat exchanger automatically lowers to the middle position. The bottom heater is automatically shut off based on the calculated melting coefficient or brightness value. The melting coefficient judgment or the brightness value calculation is performed simultaneously. When either condition is met, the bottom heater is shut off. Based on the brightness value calculation, the crucible is rotated, the heat exchanger is lowered to the lower limit, and the manual placement of the liquid outlet distance, pre-temperature adjustment (automatically adjusting power based on the liquid surface temperature to stabilize the temperature before formal temperature adjustment), formal temperature adjustment, crystal pulling, shoulder formation, and equal diameter measurement are performed to obtain the prepared single-crystal silicon. Alternatively, the process can be completed by removing the single-crystal furnace and continuing feeding, repeating the above preparation process.

[0131] This invention automates the process of preparing monocrystalline silicon by automatically calculating preheating time, interval time, and bottom heater shutdown time, thereby improving the efficiency and quality of the preparation process and saving manpower.

[0132] Referring to Table 2, which presents the experimental results obtained using the method of this invention, it can be seen that the method of this invention yields good results, with an automatic execution rate of 95.2%, significantly reducing the workload of manual control. Furthermore, the accuracy rate of identifying the bottom heater shutdown is 75.1%, achieving effective automatic shutdown of the bottom heater.

[0133]

[0134] Table 2

[0135] Optionally, the method further includes:

[0136] Step 206: For a preset total feeding amount, calculate the total feeding time corresponding to the single crystal furnace under different feeding conditions;

[0137] Step 207: Calculate the average feeding time based on the total feeding time of the multiple calculations;

[0138] In this embodiment of the invention, under the same feeding process and the same total feeding amount, the melting rate of the single crystal furnace is the same, and the deviation in time from the start of feeding to the shutdown of the bottom heater is very small. By statistically analyzing the time from the start of feeding to the shutdown of the bottom heater under a preset total feeding amount, the range of the bottom heater shutdown time under different total feeding amounts can be determined.

[0139] Specifically, by statistically analyzing the total feeding time obtained from different feeding cycles under the preset total feeding amount, the average total feeding time corresponding to the preset total feeding amount can be determined.

[0140] Step 208: The ratio of the average feeding time to the preset total feeding amount is used as the melting coefficient.

[0141] In this embodiment of the invention, the melting coefficient can be obtained based on the ratio of the average feeding time to the preset total feeding amount.

[0142] The specific melting coefficient can be obtained through the formula Calculate, where β represents the melting coefficient. The average feeding time is represented by , and M represents the preset total feeding amount. If the average feeding time is 150 minutes and the preset total feeding amount is 300 kg, then the calculated melting coefficient is 0.5.

[0143] Optionally, after the feeding is completed, the method further includes:

[0144] Step 209: Obtain a brightness value image of the material in the single crystal furnace. The material includes solids and liquids, and the brightness values ​​of the solids and liquids at corresponding positions in the brightness value image are different.

[0145] In an embodiment of the present invention, reference is made to Figure 5 , Figure 5 A comparison chart of different brightness values ​​for liquids and solids is shown. The difference in brightness values ​​between solids and liquids in the image is significant. Therefore, a CCD camera can be used to globally capture and scan the image inside the single crystal furnace. Based on the obtained image, the brightness values ​​of solids and liquids in the image can be determined. Different brightness values ​​in the image can distinguish between solids and liquids, i.e., unmelted material and molten silicon. The respective proportions of solids and liquids can be further calculated based on the brightness values.

[0146] 210. Based on the brightness value image, determine the proportion of liquid in the material in the brightness value image, and turn off the bottom heater when the liquid proportion is greater than or equal to a preset ratio.

[0147] In this embodiment of the invention, the proportion of the liquid in the brightness value image can be determined based on the obtained brightness value of the liquid, and the time to turn off the bottom heater can be determined based on the proportion.

[0148] Specifically, the preset ratio is set according to actual needs. For example, the preset ratio can be set to 40%, which means that when the ratio of the brightness value of the liquid to the total brightness value (solid area and liquid area) contained in the brightness value image reaches 40%, the bottom heater can be turned off.

[0149] It should be noted that the method for determining the shutdown of the bottom heater in step 210 can be performed synchronously with the methods of sub-steps 2031 and 2032. If, before the waiting time determined by the methods of sub-steps 2031 and 2032, the ratio of the liquid's brightness value to the total brightness value of the solid and liquid is greater than or equal to a preset ratio, then the bottom heater is shut down. If the ratio of the liquid's brightness value to the total brightness value of the solid and liquid is not yet greater than or equal to the preset ratio, but the calculated waiting time has been reached, the bottom heater can also be shut down. That is, shutting down the bottom heater can be performed synchronously in two ways, and the bottom heater is shut down when either of the two conditions is met. Determining the shutdown time of the bottom heater synchronously using two methods makes the determination of the shutdown time of the bottom heater more accurate.

[0150] In summary, this invention discloses a method for feeding a single crystal furnace. Before feeding, the preheating time is determined by calculating the amount of material remaining in the furnace before feeding. The preheating time is correlated with the ideal preheating time, power deviation, and remaining material deviation, ensuring that the obtained preheating time matches the current amount of remaining material and the operating power. Furthermore, the interval between two consecutive feedings corresponding to the current feeding amount is calculated and correlated with the power deviation and feeding amount deviation, making the interval for each feeding more accurate. This avoids inconsistencies in the furnace's state or silicon leakage accidents caused by manually controlling the preheating time and feeding interval or setting fixed feeding and preheating times. The method automatically calculates the time to shut down the bottom heater using the melt coefficient or automatically determines the timing of shutting down the bottom heater based on the brightness value, making the method of shutting down the bottom heater more consistent and timely. Compared to manually shutting down the bottom heater, this method saves time and manpower.

[0151] It should be noted that, for the sake of simplicity, the method embodiments are all described as a series of actions. However, those skilled in the art should understand that the embodiments of this application are not limited to the described order of actions, because according to the embodiments of this application, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also understand that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily essential to the embodiments of this application.

[0152] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0153] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for feeding materials in the circulation section of a single crystal furnace, characterized in that, The method includes: Based on the actual amount of residual material in the single crystal furnace, the preset preheating adjustment coefficient, the ideal preheating time calibrated for the single crystal furnace, the power deviation value, and the residual material deviation value, a target preheating time matching the actual amount of residual material is determined; the power deviation value is determined by the ideal working power and the actual working power of the single crystal furnace, and the residual material deviation value is determined by the ideal amount of residual material and the actual amount of residual material in the single crystal furnace; After the single crystal furnace is preheated according to the target preheating time, the interval between two adjacent feedings is determined based on the preset melting interval adjustment coefficient, the feeding amount deviation value, and the power deviation value when the single crystal furnace is fed in multiple batches; the feeding amount deviation value is determined by the ideal feeding amount of the single crystal furnace, the actual feeding amount, the ideal interval time, and the minimum interval time. The feeding was completed according to the calculated interval. The power deviation value is determined by the ideal operating power and the actual operating power of the single crystal furnace, specifically including: obtaining the ideal preheating power, ideal crystal pulling power, actual preheating power, and actual crystal pulling power of the single crystal furnace, wherein the actual crystal pulling power is the power of the single crystal furnace during the previous crystal rod pulling; using the difference between the ideal preheating power and the ideal crystal pulling power as the ideal difference value, using the difference between the actual preheating power and the actual crystal pulling power as the actual difference value, and using the ratio of the ideal difference value to the actual difference value as the power deviation value; Wherein, under standard thermal field conditions, the single crystal furnace has a first preheating time for a first amount of residual material and a second preheating time for a second amount of residual material; the first amount of residual material and the second amount of residual material are different values; the single crystal furnace has a first interval time for a first amount of material added and a second interval time for a second amount of material added; the first amount of material added and the second amount of material added are different values. The preheating adjustment coefficient is the ratio of the product of the second preheating time and the first remaining material amount to the product of the second remaining material amount and the first preheating time. The melting interval adjustment coefficient is the ratio of the difference between the second interval time and the first interval time minus the first interval time, to the product of the difference between the first interval time and the preset minimum interval time and the ratio of the difference between the first feeding amount and the second feeding amount to the first feeding amount. The target preheating time is the product of the preheating adjustment coefficient, the ideal preheating time, the power deviation value, and the residual material deviation value. The deviation value of the remaining material amount is the ratio of the actual remaining material amount to the ideal remaining material amount; The power deviation value is the difference between the rational preheating power and the rational crystal-leading power under the ideal working power, and the ratio of the difference between the actual preheating power and the actual crystal-leading power under the actual working power. The interval between two adjacent feedings is the product of the preset melting interval adjustment coefficient, the power deviation value, the ideal interval minus the difference between the ideal interval and the minimum interval, and the product of the difference between the ideal feeding amount and the actual feeding amount and the ratio of the ideal feeding amount.

2. The method according to claim 1, characterized in that, The method further includes: The bottom heater of the single crystal furnace is shut off after a waiting period, calculated from the moment the material is started to be added.

3. The method according to claim 2, characterized in that, The step of shutting down the bottom heater of the single crystal furnace after a waiting period includes: multiplying the melting coefficient by the total amount of material added to obtain a first product; When the current running time of the single crystal furnace is less than or equal to a first time threshold, the first product is used as the waiting time, and the bottom heater is turned off after the waiting time ends. When the current running time of the single crystal furnace is greater than the first time threshold, the difference between the current running time and the first time threshold is taken as the first difference value, and the first difference value is multiplied by a preset correction adjustment coefficient to obtain a second product; the difference between the first product and the second product is taken as the waiting time, and the bottom heater is turned off after the waiting time.

4. The method according to claim 3, characterized in that, The method further includes: For a preset total feeding amount, the total feeding time of the single crystal furnace under different feeding conditions is calculated. Calculate the average feeding time based on the total feeding time mentioned above; The ratio of the average feeding time to the preset total feeding amount is used as the melting coefficient.

5. The method according to claim 1, characterized in that, The method further includes: When the amount of residual material in the current single crystal furnace is within the preset residual material range, the process proceeds to the step of determining the target preheating time that matches the actual residual material amount based on the actual residual material amount in the single crystal furnace, the preset preheating adjustment coefficient, the ideal preheating time calibrated for the single crystal furnace, the power deviation value, and the residual material amount deviation value. When the amount of residual material in the current single crystal furnace is not within the preset residual material range, the preset fixed preheating time is used as the target preheating time.

6. The method according to claim 1, characterized in that, After the feeding is completed, the method further includes: Obtain a brightness value image of the material inside the single crystal furnace, the material including solids and liquids, the brightness values ​​of the solids and liquids at corresponding positions in the brightness value image are different; Based on the brightness value image, determine the proportion of liquid in the material within the brightness value image, and turn off the bottom heater when the liquid proportion is greater than or equal to a preset ratio.

7. The method according to claim 6, characterized in that, The method further includes: After shutting down the bottom heater of the single crystal furnace, the temperature inside the single crystal furnace is adjusted. The single-crystal silicon rod prepared in the single-crystal furnace is obtained by sequentially performing crystal pulling, shoulder forming, and equal diameter forming operations.

8. The method according to claim 7, characterized in that, The temperature control process inside the single crystal furnace includes: Obtain the brightness value of the liquid inside the single crystal furnace; Compare the brightness value with a preset brightness value range; When the brightness value is within the preset brightness value range, the temperature adjustment process enters the temperature stabilization process. When the brightness value is not within the preset brightness value range, the power of the main heater is automatically adjusted, thereby adjusting the liquid surface temperature.

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