Single crystal furnace heating method and device, electronic equipment, medium and product

Abstract

The invention provides a single crystal furnace heating method and device, electronic equipment, a medium and a product, and relates to the technical field of single crystal furnaces, the method comprises the following steps: in response to material hanging operation of an operator, obtaining the residual material amount in a single crystal furnace, and determining the charging power needing to be increased according to the residual material amount; raising the control power to the feeding power, and controlling the single crystal furnace to start preheating; after the single crystal furnace is preheated according to preset time, the position of a charging barrel of the single crystal furnace is controlled to ascend, and the auxiliary chamber is controlled to rotate, descend and be closed tightly; the preset time is related to the time when the main charging power and / or the bottom charging power reaches the charging power and the time before the charging barrel is lifted out; after the auxiliary chamber is tightly descended and meets the preset condition, the auxiliary chamber is purified, and then secondary feeding is performed, so that the whole preheating and feeding process can be automatically completed, the possibility of potential accidents caused by overtime feeding and preheating, insufficient preheating time and the like can be reduced, the safety is ensured, the operation frequency of production staff on a coil base is reduced, and the production efficiency is improved. The operation process is simplified.

Description

Technical Field

[0001] The present application relates to the technical field of single crystal furnaces, and in particular to a single crystal furnace heating method, device, electronic equipment, medium and product. Background Art

[0002] A single crystal furnace is a device used to produce single crystal materials. Single crystal materials are widely used in semiconductors, optoelectronics and other high-tech fields. RCZ (modified Czochralski method) is a common single crystal pulling method, which is a method of gradually forming a single crystal by immersing the seed crystal into the molten raw material, and then slowly pulling and rotating it.

[0003] In the prior art, after the single crystal furnace completes single crystal pulling based on RCZ, the single crystal material needs to be disconnected from the molten raw material. After the wire is disconnected and before adding materials, the single crystal furnace needs to be preheated to ensure that the new raw material can be quickly melted and evenly mixed with the existing molten raw material. During the preheating process, it is necessary to manually monitor the melting condition of the material block, and determine when is the best time to add materials based on the melting condition of the material block. After determining the time to add materials, the furnace needs to be manually operated for preheating and adding materials.

[0004] However, since the above processes require manual operation, it may lead to preheating timeout, insufficient preheating time for adding materials, insufficient interval time for adding materials, failure of secondary crystallization due to low temperature in the furnace, and damage to the quartz crucible. There is a risk of silicon leakage accidents, the operation is complicated, and there is a lack of safety. Summary of the invention

[0005] The present application provides a single crystal furnace heating method, device, electronic equipment, medium and product, which are used to realize automatic heating of the single crystal furnace, simplify the operation process and improve the safety of operation.

[0006] In a first aspect, the present application provides a single crystal furnace heating method, the method comprising:

[0007] In response to the operator's material loading operation, the amount of remaining material in the single crystal furnace is obtained, and the required increased material loading power is determined according to the amount of remaining material;

[0008] Controlling the main adding power and / or the bottom adding power to increase until the feeding power is reached, and controlling the single crystal furnace to start preheating;

[0009] After the single crystal furnace is preheated according to a preset time, the barrel of the single crystal furnace is controlled to rise to a first position, and the auxiliary chamber is controlled to rotate down and close tightly; the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out;

[0010] After the auxiliary chamber is lowered and tightly closed to meet the preset conditions, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary feeding is performed after the auxiliary chamber is purified.

[0011] Optionally, control the secondary chamber to rotate and close tightly, including:

[0012] Identify the current crucible position, heat shield position, and crystal position;

[0013] The crucible is controlled to descend from the crucible position to the charging crucible position, the heat shield is controlled to rise from the heat shield position to the upper limit position of the heat shield, and the crystal is controlled to rise from the crystal position to the first position.

[0014] Optionally, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary charging is performed after the auxiliary chamber purification, including:

[0015] After the barrel of the single crystal furnace rotates back to the auxiliary chamber, collecting liquid level images in the single crystal furnace at predefined time intervals;

[0016] Identify the shape of the material block in the liquid surface image, and draw a material block rectangle according to the material block shape;

[0017] Calculate the solid-liquid ratio in the liquid surface image based on the rectangle of the material block, and when the solid-liquid ratio reaches a preset threshold, determine whether the melting size of the material block in the single crystal furnace meets the feeding conditions;

[0018] If so, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary charging is performed after the auxiliary chamber purification, and the barrel is taken out after the charging is completed.

[0019] Optionally, identifying the shape of the material block in the liquid surface image and drawing a material block rectangle according to the material block shape includes:

[0020] Performing grayscale processing on the liquid surface image;

[0021] Binarize the grayscale processed liquid surface image to obtain a pixel point image;

[0022] The shape of the block is determined by the area of ​​the pixels in the pixel image, and a block rectangle is drawn according to the block shape.

[0023] Optionally, calculating the solid-liquid ratio in the liquid surface image based on the material block rectangle includes:

[0024] Determine the first pixel area occupied by the material block rectangle;

[0025] Determine a second pixel area occupied by the liquid in the liquid surface image based on the first pixel area;

[0026] The solid-liquid ratio is calculated based on the first pixel area and the second pixel area.

[0027] Optionally, the method further includes:

[0028] When a waiting phenomenon occurs, by identifying the solid-liquid ratio in the single crystal furnace, it is determined whether the solid-liquid ratio reaches a parameter setting value;

[0029] If so, the main boost power and / or bottom boost power are controlled to decrease.

[0030] In a second aspect, the present application provides a single crystal furnace heating device, the device comprising:

[0031] A determination module, used to obtain the amount of remaining material in the single crystal furnace in response to the material hanging operation of the operator, and determine the required increase in the feeding power according to the remaining material amount;

[0032] A control module, used for controlling the main adding power and / or the bottom adding power to increase until the feeding power is reached, and controlling the single crystal furnace to start preheating;

[0033] A preheating module is used to control the barrel of the single crystal furnace to rise to the first position and control the auxiliary chamber to rotate down and close after preheating the single crystal furnace according to a preset time; the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out;

[0034] The feeding module is used to control the single crystal furnace to purify the auxiliary chamber after the auxiliary chamber is lowered and tightly closed to meet preset conditions, and to perform secondary feeding after the auxiliary chamber is purified.

[0035] In a third aspect, the present application provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor;

[0036] The memory stores computer-executable instructions;

[0037] The processor executes the computer-executable instructions stored in the memory to implement the method as described in any one of the first aspects.

[0038] In a fourth aspect, the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method as described in any one of the first aspects.

[0039] In a fifth aspect, the present application provides a computer program product, comprising a computer program, which, when executed by a processor, implements the method as described in any one of the first aspects.

[0040] In summary, the present application provides a single crystal furnace heating method, device, electronic equipment, medium and product, which monitors the amount of residual material in the single crystal furnace, determines the main power and / or bottom power that need to be increased, and then realizes automatic preheating, and preheats the single crystal furnace according to a preset time set in advance, and the preset time is related to the time when the main power and / or bottom power reach the feeding power and the time before the barrel is taken out, and then after the single crystal furnace is preheated at the preset time, the barrel is controlled to automatically rise and the auxiliary chamber is automatically rotated and lowered to close, and then after the lowering and closing meet the preset conditions, automatic auxiliary chamber purification is started, and automatic feeding is performed after the auxiliary chamber purification is completed; in this way, the entire preheating and feeding process can be completed automatically, and the possibility of accidents caused by feeding preheating timeout, insufficient preheating time, too large material blocks in the furnace during the feeding process, too little feeding, etc. can be reduced. While ensuring safety, it can also reduce the frequency of operations of production employees at the furnace platform, simplify the operating procedures, and achieve staff reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0042] Figure 1 A schematic diagram of the process of heating an existing single crystal furnace;

[0043] Figure 2 A schematic diagram of an application scenario provided for an embodiment of the present application;

[0044] Figure 3 A schematic diagram of the structure of a pendant provided in an embodiment of the present application;

[0045] Figure 4 A schematic diagram of a single crystal furnace heating method provided in an embodiment of the present application;

[0046] Figure 5 A schematic diagram of a rectangular material block drawn for an embodiment of the present application;

[0047] Figure 6 A schematic flow chart of an optional single crystal furnace heating method provided in an embodiment of the present application;

[0048] Figure 7 A schematic diagram of the structure of a single crystal furnace heating device provided in an embodiment of the present application;

[0049] Figure 8 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0050] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0051] In order to facilitate the clear description of the technical solutions of the embodiments of the present application, in the embodiments of the present application, the words "first", "second" and the like are used to distinguish the same items or similar items with substantially the same functions and effects. For example, the first device and the second device are only used to distinguish different devices, and their order is not limited. Those skilled in the art can understand that the words "first", "second" and the like do not limit the quantity and execution order, and the words "first", "second" and the like do not necessarily limit them to be different.

[0052] It should be noted that, in this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0053] In the present application, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can mean: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0054] The following is an explanation of the professional terms involved in this application:

[0055] Main power: also known as main heater power, refers to the main electrical power used to heat the crucible and molten polysilicon in the single crystal furnace.

[0056] Bottom-added power: also known as bottom heater power, refers to the electric power consumed by the auxiliary heater used to heat the bottom of the crucible or the bottom area of ​​the furnace in the single crystal furnace. The bottom heater is used to assist the main heater.

[0057] Breaking and lifting: refers to the process of lifting the crystal out of the molten silicon by breaking the connection with the liquid surface after defects appear in the crystal during the growth process of single crystal silicon.

[0058] Pulling: refers to the process of gradually pulling out single crystal silicon rods from molten silicon by controlling temperature, pulling speed and other parameters during the single crystal silicon production process.

[0059] Finishing and segmenting: refers to the process of gradually ending the growth process of the crystal through a series of operations and taking the crystal out of the melt after the growth length and the remaining material in the crucible reach the process standards during the pulling process of the single crystal silicon rod.

[0060] Hanging: refers to the process of pulling single crystal silicon. After the broken wire is taken out or the segment is finished, the polysilicon raw material is loaded into the quartz barrel, and the quartz barrel is hung on a heavy hammer and added to the single crystal furnace, ready for the operation of melting and pulling single crystal silicon.

[0061] In one possible implementation, Figure 1 A schematic diagram of the process of heating an existing single crystal furnace is shown below: Figure 1 As shown, after the single crystal rod is pulled, the final section is taken out or the broken wire is removed, the production staff will take out the crystal rod after it has cooled down. Furthermore, after the crystal rod is cooled and taken out, the production staff will unscrew the graphite chuck containing the seed crystal, click the re-feeding step, and notify the hanger to hang the material. Further, after the hanger has finished hanging the material, the barrel is raised to the auxiliary chamber, and then the production staff checks the amount of remaining material in the furnace, and calculates the preheating time according to the preheating process standard based on the amount of remaining material in the furnace. Further, the single crystal furnace is manually controlled to preheat within the preheating time, and the barrel rotation step is clicked after the preset time is reached, and then the barrel can be automatically rotated. Further, after the barrel is automatically rotated, the production staff needs to re-measure the preheating time, and click the auxiliary chamber purification step after confirming that there is no abnormality, so that the furnace table can automatically add material after the automatic auxiliary chamber purification.

[0062] It can be seen from this that after the single crystal furnace is pulling, finishing or breaking the wire based on RCZ, it is necessary to manually calculate the preheating time, pay attention to the melting of the material block, determine the timing of adding materials, and manually operate the furnace of the single crystal furnace for preheating and adding materials before adding materials.

[0063] However, manual calculation and manual operation may result in differences and errors in human operation, which may lead to preheating timeout, feeding interval timeout, long-term high-power baking of quartz crucible, insufficient preheating time for feeding, insufficient feeding interval time, and low temperature in the furnace causing secondary crystallization and damage to the quartz crucible. There is a risk of silicon leakage accidents, lack of safety, and manual operation is relatively complicated.

[0064] In response to the above problems, the present application provides a single crystal furnace heating method, which monitors the amount of residual material in the single crystal furnace, determines the main power and / or bottom power that need to be increased, and then realizes automatic preheating, and preheats the single crystal furnace according to a preset time set in advance, and the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out, and then after the single crystal furnace is preheated at the preset time, the barrel is controlled to automatically rise and the auxiliary chamber is automatically rotated to descend and close, and then after the descent and closing meet the preset conditions, automatic auxiliary chamber purification is started, and automatic feeding is performed after the auxiliary chamber purification is completed; in this way, the entire preheating and feeding process can be completed automatically, and the possibility of potential accidents caused by feeding preheating timeout, insufficient preheating time, too large material blocks in the furnace during the feeding process, too little feeding, etc. can be reduced. While ensuring safety, it can also reduce the frequency of operations of production employees at the furnace platform, simplify the operating procedures, and achieve staff reduction.

[0065] For example, Figure 2 A schematic diagram of an application scenario provided in an embodiment of the present application, such as Figure 2 As shown, this application scenario can be applied to the process of charging a single crystal furnace, especially before secondary charging. The application scenario includes: a single crystal furnace 203, a furnace table system 202 and a display device 201 corresponding to the furnace table system 202. The furnace table system 202 is used to support and operate components such as crucibles, heaters, heat shields, and provide necessary movement, monitoring and control functions, such as rotating the crucible, controlling the lifting and lowering of the barrel, monitoring the temperature of the crucible and the melt, and collecting and recording key parameters such as temperature and pulling speed.

[0066] The single crystal furnace 203 includes a main heater, a bottom heater and a quartz crucible; the quartz crucible contains seeding liquid; the main heater and the bottom heater are used to provide thermal energy.

[0067] For example, after the crystal rod is cooled and taken out, the production staff unscrews the graphite chuck containing the seed crystal and places it safely, and then notifies the hanger worker by intercom to prepare the hangers for hanging materials. Since the temperature in the single crystal furnace 203 is relatively low after the rod is taken out and does not meet the material chemistry standard, the main power and / or bottom power must be increased to the feeding power to complete the preheating before feeding.

[0068] Therefore, in response to the hanging operation of the hanging worker, the furnace table system 202 can obtain the remaining material in the single crystal furnace 203, and then determine the required increasing feeding power according to the remaining material, and further, control the main feeding power and / or bottom feeding power to increase according to the feeding power, and start preheating after increasing to the feeding power, and further, after preheating the single crystal furnace 203 within the preset time, control the barrel to automatically rise and the auxiliary chamber to automatically rotate and descend and close, and then after the descent and closing meet the preset conditions, start automatic auxiliary chamber purification, so as to automatically add material after the auxiliary chamber purification is completed; in this way, the furnace table system 202 can realize the automatic preheating and automatic feeding functions of the single crystal furnace 203.

[0069] Among them, the hanging piece is a threaded device. Figure 3 A schematic diagram of the structure of a pendant provided in an embodiment of the present application is shown in FIG. Figure 3 As shown, the pendant is screwed onto the weight 205, the weight 205 is suspended at the end of the upper shaft tungsten wire rope 204, the graphite chuck is screwed onto the weight 205, and the seed crystal is installed in the graphite chuck.

[0070] Optionally, production staff and operators such as hangers can perform a series of selection operations based on the display device 201 corresponding to the furnace system 202 to trigger corresponding processes, such as the operator clicking the re-feeding operation based on the display device 201 corresponding to the furnace system 202. The embodiment of the present application does not specifically limit the process corresponding to the selection operation.

[0071] Optionally, the display device 201 corresponding to the furnace system 202 is also used to display the processing results, monitoring results and photographed pictures of each process, such as the real-time display of the main power and / or bottom power, the temperature in the furnace, the collected pictures of the material blocks in the furnace, etc., for relevant employees or operators to view.

[0072] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0073] Figure 4 A schematic diagram of a single crystal furnace heating method provided in an embodiment of the present application is shown in FIG. Figure 4 As shown, the single crystal furnace heating method comprises the following steps:

[0074] S401. In response to the material hanging operation of the operator, the amount of remaining material in the single crystal furnace is obtained, and the required increased material adding power is determined according to the amount of remaining material.

[0075] In the embodiment of the present application, the amount of polysilicon raw material remaining in the single crystal furnace can be detected by a sensor or other monitoring equipment. The embodiment of the present application does not specifically limit the method for obtaining the amount of residual material in the single crystal furnace.

[0076] In this step, the feeding power that needs to be increased, including the main heater power and / or the bottom heater power, can be calculated based on the detected amount of residual material to ensure that the melt temperature reaches a level suitable for crystal growth; wherein the feeding power is a set parameter threshold value, which is used to ensure that the temperature in the furnace reaches the required temperature threshold value.

[0077] Optionally, after completing the operations of single-wire pulling end segmentation or equal-diameter wire cutting according to the quality requirements of the single crystal furnace, the crystal rod is controlled to be taken out after cooling; in response to the second operator's operation of unscrewing the chuck of the crystal rod, a prompt message is generated to prompt the first operator to perform the hanging operation, and then S401 can be executed.

[0078] The first operator performing the material hanging operation may be that the first operator clicks the step of "re-feeding" according to the process standard requirements, so that after clicking the step, the furnace table system automatically captures the real-time remaining material amount in the furnace.

[0079] S402, controlling the main adding power and / or the bottom adding power to increase until the feeding power is reached, and controlling the single crystal furnace to start preheating.

[0080] Exemplarily, the power of the main heater and / or the bottom heater is gradually increased through the furnace system until the calculated feeding power is reached, and then after the heater power reaches the required level, the single crystal furnace is preheated to ensure that the melt temperature is uniform and stable.

[0081] S403, after preheating the single crystal furnace according to the preset time, control the barrel of the single crystal furnace to rise to the first position, and control the auxiliary chamber to rotate down and close; the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out.

[0082] In the embodiment of the present application, the preheating time can be pre-set based on experience and process requirements to ensure that the melt reaches a temperature suitable for feeding. The embodiment of the present application does not specifically limit the length of the preheating time. The preheating time = the time from the main power and / or bottom power rising to the feeding power to the time before the material enters the barrel and is taken out.

[0083] Illustratively, after preheating is completed, the furnace system controls the barrel to rise to a first position, ready for feeding operation, wherein the first position is a preset position away from the crystal, such as 4650 mm from the crystal position. The embodiment of the present application does not specifically limit the first position, and the first position may correspond to different crystal positions based on different process requirements.

[0084] Furthermore, after the barrel of the single crystal furnace rises to the first position, the auxiliary chamber is controlled to rotate, descend and close tightly, wherein the auxiliary chamber is a sealed feeding chamber, therefore, it is necessary to control the auxiliary chamber to rotate, descend and seal to prevent outside air from entering the furnace.

[0085] It should be noted that, in the present application, the preset time not only includes the preheating time, but also takes into account the time for the heater power to reach the required level and the time for the barrel to rise and the secondary chamber to seal, thereby ensuring the stability of the preheating process.

[0086] S404, after the auxiliary chamber is lowered and tightly closed to meet preset conditions, the single crystal furnace is controlled to purify the auxiliary chamber, and secondary feeding is performed after the auxiliary chamber is purified.

[0087] In the embodiment of the present application, the preset condition refers to confirming that the auxiliary chamber has been completely sealed and meets the preset sealing condition, which can be set by the length of time. For example, if the time for the auxiliary chamber to be lowered and closed is greater than the time threshold, it is determined that the auxiliary chamber has been lowered and closed to meet the preset condition. The embodiment of the present application does not specifically limit the content corresponding to the preset condition, and it can also be set by checking the sealing degree of the auxiliary chamber.

[0088] In this way, after the sub-chamber purification is completed, a secondary feeding operation can be carried out to add new polysilicon raw materials into the melt to ensure the continuous supply and stability of the melt; the sub-chamber purification refers to the atmosphere purification after the sub-chamber is sealed, usually by filling inert gases such as argon to remove oxygen and other impurities in the sub-chamber to prevent oxidation of the melt.

[0089] Therefore, the embodiment of the present application provides a single crystal furnace heating method, which can quickly and accurately obtain the remaining material amount and calculate the required feeding power by responding to the operator's hanging operation, reduce human intervention and operation time, and then accurately calculate and control the feeding power according to the remaining material amount, ensure that the melt temperature is uniform and stable, reduce temperature fluctuations and defects in the crystal growth process, and preheat according to the preset time, so as to ensure that the melt quickly reaches a temperature suitable for melting silicon material, avoid the failure of secondary crystallization and damage to the quartz crucible caused by low temperature in the furnace, and improve the overall production efficiency; in the present application, the time coordination between each operation step and the satisfaction of the preset conditions ensure the continuity and stability of the process, ensure a reasonable feeding interval time, reduce the uncertainty and risk in the operation process, and the entire process is automated and precisely controlled to ensure that each step is accurately executed, and improve the operation safety by reducing the participation of operators.

[0090] Optionally, after preheating the single crystal furnace according to a preset time, controlling the barrel of the single crystal furnace to rise to a first position includes:

[0091] After the crystal is hung, the crystal is controlled to rise to a second position, and the single crystal furnace is controlled to be preheated within the preset time;

[0092] After the preheating is completed, the barrel of the single crystal furnace is controlled to rise to the first position.

[0093] Exemplarily, after hanging the material, the crystal position can be first raised to the second position, such as more than 2750mm away from the crystal position, so that the furnace system executes the preheating time set by the parameters. After the preheating time is reached, the barrel is controlled to automatically rise to the first position, such as 4650mm away from the crystal position.

[0094] Among them, the second position is usually an intermediate position, which is convenient for preheating operations, and the first position is usually the starting position of crystal growth, which is convenient for subsequent crystal pulling operations. The embodiment of the present application does not specifically limit the second position, which can be determined based on process requirements.

[0095] Therefore, the embodiment of the present application adopts preheating in stages, that is, first rising to the second position for preheating, and then rising to the first position. After controlling the crystal to rise to the second position, the system can identify the crystal position, and then control the automatic rotation of the sub-chamber to reduce manual operation. Further, the barrel of the single crystal furnace is controlled to rise to the first position, which can ensure that the isolation valve is in a safe position when opened or closed.

[0096] Optionally, control the secondary chamber to rotate and close tightly, including:

[0097] Identify the current crucible position, heat shield position, and crystal position;

[0098] The crucible is controlled to descend from the crucible position to the charging crucible position, the heat shield is controlled to rise from the heat shield position to the upper limit position of the heat shield, and the crystal is controlled to rise from the crystal position to the first position.

[0099] In the embodiment of the present application, the current positions of the crucible, heat shield and crystal are detected in real time by sensors or other monitoring devices. The embodiment of the present application does not specifically limit the type of device for identifying the current positions of the crucible, heat shield and crystal, and may be a camera, a visual sensor, etc.

[0100] In this step, the sub-chamber rotation process includes: the furnace system automatically identifies and grasps the current crucible position, heat shield position and crystal position, and automatically lowers the crucible position to the charging crucible position, automatically raises the heat shield position to the upper limit, and controls the crystal to automatically rise to the first position after identifying the crystal position, such as 4650mm away from the crystal position.

[0101] Among them, the feeding crucible position is usually a location convenient for adding polysilicon raw materials to ensure the smooth progress of the feeding operation.

[0102] In this way, the embodiments of the present application ensure that the positions of the crucible, heat shield and crystal are accurately adjusted through real-time monitoring and adjustment, thereby reducing position errors, and by accurately controlling the positions of the crucible, heat shield and crystal, safety hazards caused by abnormal positions of the crucible, heat shield and crystal can be effectively avoided; among them, lowering the crucible to the feeding position facilitates the system to perform feeding operations and improves feeding efficiency.

[0103] Optionally, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary charging is performed after the auxiliary chamber purification, including:

[0104] After the barrel of the single crystal furnace rotates back to the auxiliary chamber, collecting liquid level images in the single crystal furnace at predefined time intervals;

[0105] Identify the shape of the material block in the liquid surface image, and draw a material block rectangle according to the material block shape;

[0106] Calculate the solid-liquid ratio in the liquid surface image based on the rectangle of the material block, and when the solid-liquid ratio reaches a preset threshold, determine whether the melting size of the material block in the single crystal furnace meets the feeding conditions;

[0107] If so, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary charging is performed after the auxiliary chamber purification, and the barrel is taken out after the charging is completed.

[0108] In an embodiment of the present application, the predefined duration is a time interval set in advance for collecting images of the liquid level in the furnace. The predefined duration can be determined based on process requirements or can be modified manually. The embodiment of the present application does not specifically limit the predefined duration, such as a predefined duration of 6 minutes.

[0109] In the present application, a liquid level image of the liquid surface in the furnace can be collected based on a visual system, such as a camera, a camera or other visual sensors. The liquid surface includes molten silicon liquid and unmelted material blocks. The present application embodiment does not specifically limit the visual system for collecting the liquid level image. Furthermore, the furnace table system can collect the liquid level image in the single crystal furnace from the visual system at predefined time intervals; optionally, the visual system can also be a part of the furnace table system, and then the furnace table system can obtain the liquid level image in the single crystal furnace in real time, and then summarize the liquid level images in the single crystal furnace within the predefined time for subsequent processing. The present application embodiment does not specifically limit the deployment of the visual system.

[0110] For example, after the first barrel of material is added, the furnace system automatically lifts the barrel and hangs the second barrel of material back to the auxiliary chamber and closes it. At this time, the liquid level pictures in the furnace can be collected by the camera at a rate of about 23 pictures / min. Further, every 6 minutes, the furnace system draws a material block rectangle based on the collected liquid level pictures and the shape of the material block in the liquid level pictures. For example, Figure 5This is a schematic diagram of a material block rectangle drawn in an embodiment of the present application, taking the material block rectangle drawn at different times as an example, such as Figure 5 As shown in A, it is the material block rectangle drawn at the first moment. Figure 5 As shown in B, it is the material block rectangle drawn at the second moment, and more material blocks are melted at the second moment than at the first moment.

[0111] It is understandable that image processing algorithms, such as edge detection, shape recognition and other methods, can be used to draw the shape of the material block in the liquid surface image. The embodiment of the present application does not specifically limit the method of drawing the shape of the material block in the liquid surface image.

[0112] Furthermore, for each liquid surface picture, the proportion of solid (material block) and liquid (silicon liquid) in the entire picture is calculated based on the drawn material block rectangle to form a solid-liquid ratio. When the solid-liquid ratio reaches the preset threshold set by the parameters, it is determined that the melting size of the material block in the furnace meets the feeding conditions. At this time, automatic sub-chamber purification is started, and secondary feeding is carried out after the sub-chamber purification, and the barrel is lifted out after feeding.

[0113] Among them, the preset threshold is a solid-liquid ratio threshold pre-set according to the process requirements, which is used as a standard for judging the melt state. The embodiment of the present application does not specifically limit the size of the preset threshold, such as 1:3.

[0114] In this way, by regularly collecting liquid surface images and performing image analysis, the solid-liquid state in the melt can be monitored in real time to ensure the accuracy of the feeding operation, and the image processing method can be used to automatically judge the melt state, reduce human intervention and misjudgment, and improve the accuracy and automation of the operation; among them, by calculating the solid-liquid ratio, the melting degree of the material blocks in the melt can be accurately judged to ensure that the feeding operation is carried out at the best time and the feeding process is optimized. Accurate judgment of the feeding timing helps to reduce raw material waste and improve the utilization rate of polysilicon raw materials.

[0115] Optionally, identifying the shape of the material block in the liquid surface image and drawing a material block rectangle according to the material block shape includes:

[0116] Performing grayscale processing on the liquid surface image;

[0117] Binarize the grayscale processed liquid surface image to obtain a pixel point image;

[0118] The shape of the block is determined by the area of ​​the pixels in the pixel image, and a block rectangle is drawn according to the block shape.

[0119] In the embodiment of the present application, the grayscale processing is to simplify the image information and reduce the computational complexity; the binarization processing is to further simplify the image information so that the objects (such as material blocks) in the image are more clearly separated from the background, which facilitates subsequent shape recognition and analysis.

[0120] In the present application, by drawing a material block rectangle, the shape and position of the material block can be more intuitively represented, and basic data can be provided for subsequent solid-liquid ratio calculation.

[0121] Exemplarily, the liquid surface image is gray-processed and converted into a gray-scale image. Further, the gray-scale image is converted into a binary image. Each pixel in the binary image has only two possible values: 0 (black) or 1 (white). Furthermore, in the binary image, the shape of the material block is identified by analyzing the distribution and color of the pixels. Then, based on the identified shape of the material block, a rectangle surrounding the material block is drawn. The rectangle can be used to calculate the area of ​​the material block.

[0122] In this way, grayscale processing converts the liquid surface image into a single-channel grayscale image, reducing the amount of data and computational complexity and improving image processing efficiency; binarization processing makes the objects in the image more clearly separated from the background, and the image after binarization processing has clear object boundaries, which helps to accurately identify the shape and position of the material block; grayscale processing and binarization processing can also effectively reduce noise interference in the image and improve the accuracy of shape recognition. In this application, by drawing a material block rectangle, the shape and position of the material block can be intuitively represented, which is convenient for subsequent solid-liquid ratio calculation and analysis.

[0123] Optionally, calculating the solid-liquid ratio in the liquid surface image based on the material block rectangle includes:

[0124] Determine the first pixel area occupied by the material block rectangle;

[0125] Determine a second pixel area occupied by the liquid in the liquid surface image based on the first pixel area;

[0126] The solid-liquid ratio is calculated based on the first pixel area and the second pixel area.

[0127] It should be noted that, in the above embodiment, the shape of the material block in the liquid surface image is identified by image processing technology, and a rectangle surrounding the material block is drawn. Furthermore, the number of pixels within the rectangle of the material block can be counted. These pixels represent the area of ​​the material block, which is called the first pixel area.

[0128] Furthermore, by counting the total number of pixels in the entire liquid surface image and subtracting the first pixel area from the total pixel area, the pixel area occupied by the liquid can be obtained. This area is called the second pixel area. Then, based on the first pixel area / the second pixel area, the solid-liquid ratio can be obtained. The solid-liquid ratio reflects the ratio of solid material blocks to liquid silicon in the melt. By calculating the solid-liquid ratio, the degree of melting of the material blocks in the melt can be determined, and then it can be decided whether adding material is needed.

[0129] Therefore, the embodiment of the present application can accurately monitor the melt state by determining the first pixel area occupied by the material block rectangle, calculating the second pixel area occupied by the liquid, and calculating the solid-liquid ratio based on these two areas, and timely and accurately judge the melting degree of the material block in the melt to ensure that the feeding operation is performed at the best time.

[0130] Optionally, the method further includes:

[0131] When a waiting phenomenon occurs, by identifying the solid-liquid ratio in the single crystal furnace, it is determined whether the solid-liquid ratio reaches a parameter setting value;

[0132] If so, the main boost power and / or bottom boost power are controlled to decrease.

[0133] In the embodiment of the present application, the waiting phenomenon refers to the phenomenon that the raw materials cannot be delivered to the furnace in time. Therefore, when the waiting phenomenon occurs in the feeding furnace, the furnace system identifies the solid-liquid ratio in the furnace and determines whether the solid-liquid ratio reaches the parameter setting value. If so, the main power and / or bottom power are automatically reduced to avoid high-power long-term baking of the crucible, which may cause safety hazards.

[0134] Among them, the parameter setting value may refer to a solid-liquid ratio threshold value pre-set according to the process requirements as a standard for judging the melt state. The embodiment of the present application does not specifically limit the parameter setting value. When the solid-liquid ratio reaches or exceeds the preset parameter setting value, it means that the material blocks in the melt have melted to a degree that meets the process requirements.

[0135] It should be noted that the embodiments of the present application do not specifically limit the values ​​of the main power addition and / or bottom power reduction, which can be determined based on process requirements. It only needs to ensure that the power is reduced and the crucible is not baked at high power for a long time.

[0136] Therefore, when the phenomenon of waiting for material occurs, the heating power can be adjusted in time to avoid high-power and long-term crucible baking, prevent excessive consumption and damage of crucible materials, extend the service life of the crucible, and reduce the heating power in time. It can also reduce the thermal stress in the crucible and melt and avoid the generation of cracks and defects. In this way, by automatically monitoring the solid-liquid ratio in real time and adjusting the main power and / or bottom power, the production efficiency can be improved, and the downtime and the workload of operators can be reduced.

[0137] In combination with the above embodiments, Figure 6 A schematic diagram of an optional single crystal furnace heating method provided in an embodiment of the present application is shown in FIG. Figure 6 As shown, the single crystal furnace heating method comprises the following steps:

[0138] Step A: After the single crystal furnace completes single-wire pulling, finishing and segmenting, or equal-diameter wire cutting according to quality requirements, the crystal rod is taken out after cooling, and then the production staff unscrews the chuck and notifies the hanger to hang the material.

[0139] Step B: In response to the hanging operation of the hanging worker, the amount of remaining material in the furnace is obtained, and the required increase in the charging power is determined according to the remaining material amount, and then the main adding power and / or the bottom adding power are controlled to increase to the charging power to start preheating.

[0140] Step C: After the preheating time set by the parameters is reached, the furnace system automatically lifts the barrel and rotates it back to the auxiliary chamber. After the auxiliary chamber is automatically closed for 1 minute, the furnace automatically purifies the auxiliary chamber and automatically adds material after the auxiliary chamber is purified.

[0141] Therefore, through the above automated operations, the frequency of production staff operating the furnace is greatly reduced, making the operation safer and more efficient.

[0142] In the above embodiments, the single crystal furnace heating method provided by the embodiment of the present application is introduced. In order to realize the functions in the method provided by the embodiment of the present application, the electronic device as the execution subject may include a hardware structure and / or a software module, and realize the above functions in the form of a hardware structure, a software module, or a hardware structure plus a software module. Whether one of the above functions is executed in the form of a hardware structure, a software module, or a hardware structure plus a software module depends on the specific application and design constraints of the technical solution.

[0143] For example, Figure 7 A schematic diagram of the structure of a single crystal furnace heating device provided in an embodiment of the present application is shown in FIG. Figure 7 As shown, the device includes: a determination module 701, which is used to obtain the amount of remaining material in the single crystal furnace in response to the material hanging operation of the operator, and determine the required increase in the feeding power according to the remaining material;

[0144] The control module 702 is used to control the main adding power and / or the bottom adding power to increase until the feeding power is reached, and control the single crystal furnace to start preheating;

[0145] The preheating module 703 is used to control the barrel of the single crystal furnace to rise to the first position and control the auxiliary chamber to rotate down and close after preheating the single crystal furnace according to a preset time; the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out;

[0146] The feeding module 704 is used to control the single crystal furnace to perform sub-chamber purification after the sub-chamber is lowered and tightly closed to meet preset conditions, and to perform secondary feeding after the sub-chamber is purified.

[0147] Optionally, the preheating module 703 is specifically used for:

[0148] Identify the current crucible position, heat shield position, and crystal position;

[0149] The crucible is controlled to descend from the crucible position to the charging crucible position, the heat shield is controlled to rise from the heat shield position to the upper limit position of the heat shield, and the crystal is controlled to rise from the crystal position to the first position.

[0150] Optionally, the feeding module 704 includes a collection unit, an identification unit, a determination unit and a feeding unit;

[0151] The collecting unit is used to collect liquid level images in the single crystal furnace at predefined time intervals after the barrel of the single crystal furnace rotates back to the auxiliary chamber;

[0152] The recognition unit is used to recognize the shape of the material block in the liquid surface image and draw a material block rectangle according to the material block shape;

[0153] The determination unit is used to calculate the solid-liquid ratio in the liquid surface image based on the material block rectangle, and when the solid-liquid ratio reaches a preset threshold, determine whether the melting size of the material block in the single crystal furnace meets the feeding conditions;

[0154] The feeding unit is used to control the single crystal furnace to perform sub-chamber purification when the melting size of the material block in the single crystal furnace meets the feeding conditions, and to perform secondary feeding after the sub-chamber purification, and to take out the barrel after the feeding is completed.

[0155] Optionally, the identification unit is specifically used to:

[0156] Performing grayscale processing on the liquid surface image;

[0157] Binarize the grayscale processed liquid surface image to obtain a pixel point image;

[0158] The shape of the block is determined by the area of ​​the pixels in the pixel image, and a block rectangle is drawn according to the block shape.

[0159] Optionally, the determination unit is specifically configured to:

[0160] Determine the first pixel area occupied by the material block rectangle;

[0161] Determine a second pixel area occupied by the liquid in the liquid surface image based on the first pixel area;

[0162] The solid-liquid ratio is calculated based on the first pixel area and the second pixel area.

[0163] Optionally, the device further includes a judgment module, wherein the judgment module is configured to:

[0164] When a waiting phenomenon occurs, by identifying the solid-liquid ratio in the single crystal furnace, it is determined whether the solid-liquid ratio reaches a parameter setting value;

[0165] If so, the main boost power and / or bottom boost power are controlled to decrease.

[0166] It should be noted that the specific implementation principle and effects of the above-mentioned single crystal furnace heating device can be found in the relevant descriptions and effects corresponding to the above-mentioned embodiments, and will not be elaborated here.

[0167] The present application also provides a schematic diagram of the structure of an electronic device. Figure 8 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application is shown in FIG. Figure 8 As shown, the electronic device may include: a processor 801 and a memory 802 communicatively connected to the processor; the memory 802 stores a computer program; the processor 801 executes the computer program stored in the memory 802, so that the processor 801 executes the method described in any of the above embodiments.

[0168] The memory 802 and the processor 801 may be connected via a bus 803 .

[0169] An embodiment of the present application further provides a computer-readable storage medium, which stores computer-executable instructions. When the computer-executable instructions are executed by a processor, they are used to implement the method described in any of the aforementioned embodiments of the present application.

[0170] An embodiment of the present application further provides a chip for executing instructions, wherein the chip is used to execute the method described in any of the aforementioned embodiments as executed by an electronic device in any of the aforementioned embodiments of the present application.

[0171] An embodiment of the present application further provides a computer program product, which includes a computer program. When the computer program is executed by a processor, the method described in any of the aforementioned embodiments of the present application executed by an electronic device can be implemented.

[0172] In the several embodiments provided in the present application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of modules is only a logical function division. There may be other division methods in actual implementation, such as multiple modules or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or modules, which can be electrical, mechanical or other forms.

[0173] The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the modules may be selected according to actual needs to implement the solution of this embodiment.

[0174] In addition, each functional module in each embodiment of the present application can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The above-mentioned module-composed unit can be implemented in the form of hardware or in the form of hardware plus software functional units.

[0175] The above-mentioned integrated module implemented in the form of a software function module can be stored in a computer-readable storage medium. The above-mentioned software function module is stored in a storage medium, including a number of instructions for causing a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to perform some steps of the method described in each embodiment of the present application.

[0176] It should be understood that the processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), etc. A general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the application may be directly implemented as being executed by a hardware processor, or may be implemented by a combination of hardware and software modules in the processor.

[0177] The memory may include high-speed random access memory (RAM), and may also include non-volatile memory (NVM), such as at least one disk storage, and may also be a USB flash drive, a mobile hard disk, a read-only memory, a disk or an optical disk, etc.

[0178] The bus may be an Industry Standard Architecture (ISA) bus, a Peripheral Component Interconnect (PCI) bus, or an Extended Industry Standard Architecture (EISA) bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. For ease of representation, the bus in the drawings of the present application is not limited to only one bus or one type of bus.

[0179] The above storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, magnetic disk or optical disk. The storage medium can be any available medium that can be accessed by a general or special computer.

[0180] An exemplary storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the storage medium can also exist as discrete components in an electronic device or a main control device.

[0181] It should be noted that, for the aforementioned method embodiments, for the sake of simplicity, they are all expressed as a series of action combinations, but those skilled in the art should be aware that the present application is not limited by the described order of actions, because according to the present application, certain steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also be aware that the embodiments described in the specification are all optional embodiments, and the actions and modules involved are not necessarily required by the present application.

[0182] It should be further noted that, although the various steps in the flowchart are displayed in sequence according to the indication of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless there is a clear description in this article, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowchart may include multiple sub-steps or multiple stages, and these sub-steps or stages are not necessarily executed at the same time, but can be executed at different times, and the execution order of these sub-steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

[0183] In the above embodiments, the description of each embodiment has its own emphasis. For the part not described in detail in a certain embodiment, please refer to the relevant description of other embodiments. The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0184] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the invention disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the claims.

[0185] The above is only a specific implementation of the embodiment of the present application, but the protection scope of the embodiment of the present application is not limited thereto, and any changes or replacements within the technical scope disclosed in the embodiment of the present application should be included in the protection scope of the embodiment of the present application. Therefore, the protection scope of the embodiment of the present application should be based on the protection scope of the claims.

Claims

1. A single crystal furnace heating method, characterized in that: The method comprises: In response to the operator's material loading operation, the amount of remaining material in the single crystal furnace is obtained, and the required increased material loading power is determined according to the amount of remaining material; Controlling the main adding power and / or the bottom adding power to increase until the feeding power is reached, and controlling the single crystal furnace to start preheating; After the single crystal furnace is preheated according to a preset time, the barrel of the single crystal furnace is controlled to rise to a first position, and the auxiliary chamber is controlled to rotate down and close tightly; the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out; After the auxiliary chamber is lowered and tightly closed to meet the preset conditions, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary feeding is performed after the auxiliary chamber is purified.

2. The method according to claim 1, characterized in that Control the auxiliary chamber to rotate and descend tightly, including: Identify the current crucible position, heat shield position, and crystal position; The crucible is controlled to descend from the crucible position to the charging crucible position, the heat shield is controlled to rise from the heat shield position to the upper limit position of the heat shield, and the crystal is controlled to rise from the crystal position to the first position.

3. The method according to claim 1, characterized in that Control the single crystal furnace to perform auxiliary chamber purification, and perform secondary charging after the auxiliary chamber purification, including: After the barrel of the single crystal furnace rotates back to the auxiliary chamber, collecting liquid level images in the single crystal furnace at predefined time intervals; Identify the shape of the material block in the liquid surface image, and draw a material block rectangle according to the material block shape; Calculate the solid-liquid ratio in the liquid surface image based on the rectangle of the material block, and when the solid-liquid ratio reaches a preset threshold, determine whether the melting size of the material block in the single crystal furnace meets the feeding conditions; If so, the single crystal furnace is controlled to perform auxiliary chamber purification, and secondary charging is performed after the auxiliary chamber purification, and the barrel is taken out after the charging is completed.

4. The method according to claim 3, characterized in that Identifying the shape of the material block in the liquid surface image and drawing a material block rectangle according to the material block shape, including: Performing grayscale processing on the liquid surface image; Binarize the grayscale processed liquid surface image to obtain a pixel point image; The shape of the block is determined by the area of ​​the pixels in the pixel image, and a block rectangle is drawn according to the block shape.

5. The method according to claim 4, characterized in that Calculating the solid-liquid ratio in the liquid surface image based on the material block rectangle includes: Determine the first pixel area occupied by the material block rectangle; Determine a second pixel area occupied by the liquid in the liquid surface image based on the first pixel area; The solid-liquid ratio is calculated based on the first pixel area and the second pixel area.

6. The method according to any one of claims 1 to 5, characterized in that: The method further comprises: When a waiting phenomenon occurs, by identifying the solid-liquid ratio in the single crystal furnace, it is determined whether the solid-liquid ratio reaches a parameter setting value; If so, the main boost power and / or bottom boost power are controlled to decrease.

7. A single crystal furnace heating device, characterized in that: The device comprises: A determination module, used to obtain the amount of remaining material in the single crystal furnace in response to the material hanging operation of the operator, and determine the required increase in the feeding power according to the remaining material amount; A control module, used for controlling the main adding power and / or the bottom adding power to increase until the feeding power is reached, and controlling the single crystal furnace to start preheating; A preheating module is used to control the barrel of the single crystal furnace to rise to the first position and control the auxiliary chamber to rotate down and close after preheating the single crystal furnace according to a preset time; the preset time is related to the time when the main power and / or bottom power reaches the feeding power and the time before the barrel is taken out; The feeding module is used to control the single crystal furnace to purify the auxiliary chamber after the auxiliary chamber is lowered and tightly closed to meet preset conditions, and to perform secondary feeding after the auxiliary chamber is purified.

8. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 6.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method according to any one of claims 1 to 6.

10. A computer program product, characterized in that The invention comprises a computer program, which implements the method according to any one of claims 1 to 6 when being executed by a processor.

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