Method for controlling resistivity of group v element-doped crystal ingot

Abstract

The present disclosure relates to the technical field of semiconductor material preparation, and provides a method for controlling the resistivity of a Group V element-doped crystal ingot. By differentiating the crystal pulling time according to different crystal pulling stages, and adjusting the volatilization coefficients of a doping element at different times, the volatilization amount of the doping element within each time interval can be calculated more accurately; thus, the amount of doping element required for resistivity control can be calculated more accurately, and the resistivity of a crystal ingot can be adjusted more effectively and accurately, thereby helping to reduce a resistivity difference between the head and tail of the single-crystal ingot. In addition, by means of timely adjustment of the control process for grade and tail-end volatilization amount, supplementary doping conditions required during the crystal pulling process are determined, thereby improving the resistivity target attainment rate of the crystal ingot and reducing resistivity difference between the head and tail, and thus precisely controlling the resistivity of each portion of the crystal ingot to ensure the consistency in the quality of subsequent silicon wafer products.

Description

A method for controlling the resistivity of Group 5 element-doped crystal rods

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510012673.7, filed on January 6, 2025, entitled "A Method for Controlling the Resistivity of a Group 5 Doped Crystal Rod", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of semiconductor material preparation technology, and in particular to a method for controlling the resistivity of a group 5 element-doped crystal rod. Background Technology

[0004] The methods for preparing single-crystal silicon rods provided by related technologies have the following problems: the doping master alloy is added in the same way as the conventional doping method for pulling N-type single crystals. The process stages (including: high temperature stage, shoulder formation stage, shoulder turning stage, and finishing stage) are dynamically adjusted according to the crystal pulling process. The process time of each stage varies. The theoretical calculation of the dopant volatilization coefficient does not match the actual volatilization of the dopant during each stage. The amount of dopant volatilization cannot be accurately predicted and is uncontrollable. The actual volatilization of the dopant added with the silicon material fluctuates greatly, and the dopant addition loss is too large. All of these seriously affect the accurate control of dopant addition, resulting in insufficient precision in resistivity control. Summary of the Invention

[0005] The purpose of this disclosure is to provide a method for controlling the resistivity of group 5 element-doped crystal rods, so as to solve the problem that the resistivity cannot be accurately controlled during the preparation of existing single crystal silicon rods.

[0006] This disclosure provides a method for controlling the resistivity of a group 5 element-doped crystal rod, including:

[0007] S100 controls the time interval ratio of each process stage in the crystal pulling process of the furnace; the process stages include: high temperature stage, shoulder formation stage, shoulder turning stage and finishing stage.

[0008] S200, based on experimental verification of each process stage, determines the volatility coefficient corresponding to different process stages;

[0009] S300 determines the amount of doping volatilization corresponding to each process stage when running a single process stage based on the volatilization coefficient corresponding to each different process stage.

[0010] S400, the amount of dopant to be added is determined based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization in the corresponding process stage; the added dopant is a Group 5 element dopant.

[0011] In the S500 process, dopants and new silicon are added to a crucible containing molten silicon through a feed bucket. After the added materials melt, the crystal is pulled again.

[0012] Optionally, in S100, the specific time interval ratios for each process stage are as follows:

[0013] The high-temperature phase lasts for 300-800 minutes.

[0014] The time interval for the shoulder relaxation phase is 200-350 minutes;

[0015] The shoulder rotation phase should last for 5-10 minutes.

[0016] The time range for the final stage is 100-180 minutes.

[0017] Optionally, in S300, based on the volatility coefficient corresponding to each different process stage, the doping volatility corresponding to the single-stage operation of each process stage is determined, including:

[0018] Based on the experimental verification of the volatilization coefficient table of each process stage over time, the volatilization amount of the corresponding Group 5 dopant element was obtained.

[0019] Optionally, in S400, the amount of dopant to be added is determined based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization at the corresponding process stage, including:

[0020] The doping method is selected based on the broken wire length of the crystal rod in the crystal pulling furnace and the actual head resistance of the produced crystal rod.

[0021] If the broken wire length of the crystal rod in the crystal pulling furnace is less than or equal to 200mm, then no additional doping is required.

[0022] If the broken wire length of the crystal rod in the crystal pulling furnace is greater than 200mm, new silicon material and dopant need to be added.

[0023] Optionally, if the broken wire length of the crystal rod in the crystal pulling furnace is greater than 200mm, new silicon material and dopant need to be added, including:

[0024] When it is necessary to add new material and replenish dopant, the amount of dopant added is determined based on the target resistance dopant requirement, the remaining silicon content in the crucible, and the amount of dopant volatilized in the first process.

[0025] The remaining silicon content in the crucible is equal to the difference between the initial total doping amount, the doping amount removed during silicon liquid solidification, and the doping volatilization amount during the second process; wherein, the doping volatilization amount during the first process is the theoretical doping volatilization amount during the process, and the doping volatilization amount during the second process is the actual doping volatilization amount during the process.

[0026] Optionally, the concentration of residual doping in the crucible = NA * Z1 / (resistivity corresponding to the length of the pulled crystal rod / segregation coefficient);

[0027] NA = 6.02 * 10 23 ,Z1=(-3.1083-3.2626*X1-1.2196*X1 2 -0.13923*X1 3 ) / (1+1.0265*X1+0.38755*X1 2 +0.041833*X1 3 ), X1 = log 10 (Resistivity / Segregation Coefficient corresponding to the length of the pulled crystal rod)

[0028] Doping concentration of the pulled crystal rod = NA * initial doping concentration * (1 - solidification ratio) (0.35-1) / (1-initial solidification ratio) (0.35-1) ;

[0029] The doping concentration extracted from the solidified silicon melt is calculated as: doping concentration of the pulled crystal rod / segregation coefficient; segregation coefficient = 0.023.

[0030] Target resistance required doping concentration = NA * Z2 / target resistance;

[0031] NA = 6.02 * 10 23 ,Z2=(-3.1083-3.2626*X2-1.2196*X2 2 -0.13923*X2 3 ) / (1+1.0265*X2+0.38755*X2 2 +0.041833*X2 3 ), X2 = log 10 (Target resistivity / segregation coefficient);

[0032] Initial doping amount = initial doping concentration / segregation coefficient;

[0033] First-stage doping volatilization amount = target time of each process stage * volatilization coefficient;

[0034] The amount of doped volatilization in the second process = the actual time of each process stage * the volatilization coefficient.

[0035] Optionally, in S200, based on experimental verification of each process stage, the volatility coefficients corresponding to different process stages are determined, including:

[0036] The volatility coefficient during the high-temperature stage is 0.05–2.2;

[0037] The volatility coefficient during the shoulder release stage is 0.05-0.35;

[0038] The volatility coefficient during the shoulder transition stage is 0.05–0.1;

[0039] The volatility coefficient in the final stage is 0.1 to 0.25.

[0040] Optionally, in S400, the amount of dopant to be added is determined based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization at the corresponding process stage, and further includes:

[0041] The doping method is selected based on the number of single-stage releases and the actual head resistance of the produced crystal rod.

[0042] If the number of single-segment triggers is less than or equal to 2, then no additional doping is required;

[0043] If the number of single-segment triggers exceeds 2, new silicon material and dopant should be added again.

[0044] Optionally, in S500, the added dopant and new silicon are added to a crucible containing molten silicon via a feed bucket. After the added material melts, the crystal is pulled again, including:

[0045] The dopant addition position is adjusted according to the dosage of the added dopant and the new silicon material. The dopant addition position is quantitatively controlled as a percentage of the total feed amount per barrel, and the added dopant is partially isolated from the molten silicon by the new silicon material. The total feed amount is the sum of the dopant addition amount and the new silicon material addition amount. When the total feed amount is less than or equal to the single-barrel feed amount, the total feed amount equals the single-barrel total feed amount. When the total feed amount is greater than the single-barrel feed amount, the single-barrel total feed amount is the maximum feed amount added to the barrel at one time. The dopant addition position is the surface position of the barrel after adding silicon material accounting for 10-50% of the total single-barrel feed amount. The remaining silicon material is added after the dopant addition.

[0046] Optionally, the silicon material below the dopant is called the lower silicon particles, and the new silicon material above the dopant is called the upper silicon particles; wherein, the particle size of the lower silicon particles is smaller than that of the upper silicon particles, the particle size of the lower silicon particles is 8-30mm, and the particle size of the upper silicon particles is 9-50mm.

[0047] The embodiments disclosed herein have at least the following technical effects:

[0048] The method for controlling the resistivity of Group 5 element-doped crystal rods provided in this disclosure clearly divides the crystal pulling time for different crystal pulling stages. Through experiments, the actual volatilization coefficient within the clearly defined fixed intervals of the crystal pulling time for different crystal pulling stages is obtained. This determines the amount of dopant volatilization corresponding to each process stage during single-stage operation, thereby more accurately calculating the amount of dopant volatilization within each time interval. This allows for a more accurate calculation of the amount of dopant required to control the resistance, enabling more effective and precise adjustment of the crystal rod resistance. This avoids issues arising during process stages (including: high-temperature stage, shoulder formation stage, shoulder turning stage, and...). The final stage of the process is dynamically adjusted according to the crystal pulling process. The process time of each stage varies. The theoretical calculation of the dopant volatilization coefficient does not match the actual volatilization of the dopant during each stage. The amount of dopant volatilization cannot be accurately predicted, and the amount of volatilization is uncontrollable. This helps to better reduce the resistance difference between the beginning and end of the single crystal rod. At the same time, by adjusting the control process of equal diameter and the amount of volatilization at the end, the conditions for supplementary doping during the crystal pulling process are clarified, the crystal rod resistance hit rate is improved and the resistance difference between the beginning and end is reduced, thereby accurately controlling the resistivity of each part of the crystal rod and ensuring the consistency of parameters of the subsequent silicon wafer products as much as possible.

[0049] Furthermore, the dopant addition position is quantitatively controlled based on the proportion of the total feed amount in a single tank. Specifically, the dopant is added above the surface of the silicon material after adding 10-50% of the total feed amount in the tank. After adding the dopant, the remaining silicon material is added on top of the dopant. This method allows the dopant volatilization to be determined experimentally. By using a fixed dopant addition position, the volatilization of the dopant is reduced and controlled, avoiding large fluctuations in the actual volatilization of the dopant added with the silicon material and excessive dopant loss, which seriously affect the accurate control of dopant addition. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the specific embodiments of this disclosure or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0051] Figure 1 is a flowchart of a method for measuring the resistivity of a group 5 element-doped crystal rod according to an embodiment of this disclosure. Detailed Implementation

[0052] The technical solutions of this disclosure will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of this disclosure, not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0053] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless specifically defined as herein.

[0054] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this disclosure means the presence of the stated feature, integer, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The term “and / or” as used herein includes all or any unit and all combinations of one or more associated listed items.

[0055] In the preparation method of single-crystal silicon rods provided by related technologies, the resistance of the single-crystal rods is adjusted by using dopants such as antimony, phosphorus, arsenic, and bismuth. By controlling the concentration of dopants in the single-crystal silicon rods, single-crystal silicon rods with excellent resistivity range and resistivity concentration are obtained, thereby improving the overall quality of the single-crystal silicon rod products.

[0056] However, the inventors discovered the following problems with the above preparation method: the doping master alloy addition method is the same as the conventional N-type single crystal pulling doping addition method. The process stages (including: high temperature stage, shoulder formation stage, shoulder turning stage, and finishing stage) are dynamically adjusted according to the crystal pulling process. The process time of each stage varies. The theoretical calculation of the dopant volatilization coefficient does not match the actual volatilization of the dopant during each stage. The amount of dopant volatilization cannot be accurately predicted and is uncontrollable. The actual volatilization of the dopant added with silicon fluctuates greatly, and the dopant addition loss is too large. All of these seriously affect the accurate control of dopant addition, resulting in insufficient precision in resistivity control.

[0057] As shown in Figure 1, this disclosure provides a method for controlling the resistivity of a doped crystal rod, including:

[0058] S100 controls the time interval ratio of each process stage in the crystal pulling process of the furnace; the process stages include the following in sequence: high temperature stage, shoulder formation stage, shoulder turning stage and finishing stage.

[0059] Optionally, in S100, the specific time interval ratios for each process stage are as follows:

[0060] The high-temperature phase lasts for 300-800 minutes. Specifically, the high-temperature phase refers to the time between the end of the last batch of material added and the start of crystal development.

[0061] The shoulder formation stage takes 200-350 minutes. The shoulder formation time is the time between the start of crystal pulling and the start of shoulder rotation.

[0062] The shoulder rotation phase lasts for 5-10 minutes.

[0063] The time range for the final stage is 100-180 minutes.

[0064] S200 determines the volatility coefficient corresponding to different process stages based on experimental verification of each process stage.

[0065] Optionally, when the dopant is antimony, in S200, based on experimental verification of each process stage, the volatility coefficient corresponding to different process stages is determined, including:

[0066] The volatility coefficient during the high-temperature stage is 0.05–2.2;

[0067] The volatility coefficient during the shoulder release stage is 0.05-0.35;

[0068] The volatility coefficient during the shoulder transition stage is 0.05–0.1;

[0069] The volatility coefficient in the final stage is 0.1 to 0.25.

[0070] This step stabilizes the dopant volatilization amount corresponding to each process stage by stabilizing the operation time of each process stage. This helps to reduce resistance and control anomalies, and improve the resistance hit rate. The calculation of dopant volatilization amount is carried out separately for the high temperature stage, shoulder formation stage, shoulder turning stage and finishing stage of different process stages, so as to monitor the volatilization amount of antimony in different process stages individually.

[0071] S300 determines the amount of doping volatilization corresponding to each process stage during single-stage operation based on the volatilization coefficient corresponding to each different process stage.

[0072] Optionally, in S300, based on the volatility coefficient corresponding to each different process stage, the doping volatility corresponding to the single-stage operation of each process stage is determined, including:

[0073] Based on the experimental verification table of volatilization coefficients changing over time at each process stage, the volatilization coefficient corresponding to each process stage is obtained. From the volatilization coefficient, the volatilization amount of the corresponding Group 5 dopant element is obtained. Dopant element volatilization amount = time of each process stage * volatilization coefficient. That is, first, the volatilization coefficient corresponding to the time of each process stage is obtained by looking up the time, thus obtaining the dopant element volatilization amount for each process stage. Finally, the dopant element volatilization amounts of each process stage are summed to obtain the total dopant element volatilization amount. The correspondence between the volatilization coefficient and volatilization amount for each process stage is shown in Tables 1 to 4 below:

[0074] Table 1. Correspondence of volatilization coefficients at high temperature stage

[0075] Table 2. Correspondence of volatilization coefficients during the shoulder release stage.

[0076] Table 3. Correspondence of volatilization coefficients during the shoulder rotation stage.

[0077] Table 4. Correspondence of volatilization coefficients in the final stage

[0078] S400, the amount of dopant to be added is determined based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization in the corresponding process stage; the added dopant is a Group 5 element dopant.

[0079] The dopant in this embodiment is illustrated using metallic antimony as an example. Elements from the same group (Group 5) can be used as substitutes. The volatility coefficients corresponding to different element substitutions will change accordingly. Based on the selection of different elements from the same group, the corresponding volatility coefficients are adjusted according to different stages and time points to control and adjust the head and tail resistance and distribution of the single crystal silicon rod, and to control the uniformity of the head and tail resistance of the crystal rod. The calculation method for the doping amount of other elements is not specifically described here.

[0080] In some embodiments, in S400, the amount of dopant to be added is determined based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization in the corresponding process stage, including:

[0081] The doping method is selected based on the broken wire length of the crystal rod in the crystal pulling furnace and the actual head resistance of the produced crystal rod.

[0082] If the broken wire length of the crystal rod in the crystal pulling furnace is less than or equal to 200mm, then no additional doping is required.

[0083] If the broken wire length of the crystal rod in the crystal pulling furnace is greater than 200mm, new silicon material and dopant need to be added.

[0084] Optionally, if the broken wire length of the crystal rod in the crystal pulling furnace is greater than 200mm, new silicon material and dopant need to be added, including:

[0085] When it is necessary to add new material and replenish dopant, the amount of dopant to be added is determined based on the target resistor's required dopant amount, the remaining silicon content in the crucible, and the amount of dopant volatilized in the first process. That is, the required dopant amount = target resistor's required dopant amount - remaining silicon content in the crucible - amount volatilized in the first process.

[0086] The remaining silicon content in the crucible = the difference between the initial total doping amount - the doping amount removed during silicon liquid solidification - the doping amount volatilized in the second process; where the doping amount volatilized in the first process is the theoretical doping amount volatilized in the process, and the doping amount volatilized in the second process is the actual doping amount volatilized in the process.

[0087] The specific calculation for the required dopant dosage is as follows:

[0088] The concentration of residual doping in the crucible = NA * Z1 / (resistivity corresponding to the length of the pulled crystal rod / segregation coefficient);

[0089] NA = 6.02 * 10 23 ,Z1=(-3.1083-3.2626*X1-1.2196*X1 2 -0.13923*X1 3 ) / (1+1.0265*X1+0.38755*X1 2 +0.041833*X1 3 ), X1 = log 10 (Resistivity / Segregation Coefficient corresponding to the length of the pulled crystal rod)

[0090] Doping concentration of the pulled crystal rod = NA * initial doping concentration * (1 - solidification ratio) (0.35-1) / (1-initial solidification ratio) (0.35-1) ;

[0091] The doping concentration extracted from the solidified silicon melt is calculated as: doping concentration of the pulled crystal rod / segregation coefficient; segregation coefficient = 0.023.

[0092] Target resistance required doping concentration = NA * Z2 / target resistance;

[0093] NA = 6.02 * 10 23 ,Z2=(-3.1083-3.2626*X2-1.2196*X2 2 -0.13923*X23 ) / (1+1.0265*X2+0.38755*X2 2 +0.041833*X2 3 ), X2 = log 10 (Target resistivity / segregation coefficient);

[0094] Initial doping amount = initial doping concentration / segregation coefficient;

[0095] First-stage doping volatilization amount = target time of each process stage * volatilization coefficient;

[0096] Second process doping volatilization amount = time of each process stage * volatilization coefficient;

[0097] The subsequent doping dosage can be calculated from this. It should be noted that the doping volatilization amount in the first process is the theoretical doping volatilization amount in the theoretical process, and the doping volatilization amount in the second process is the actual doping volatilization amount in the actual process. The time of each process stage is the theoretical process time (for example, the theoretical process time of the high-temperature stage is the time between the end of the last batch of material feeding and the start of crystal pulling, which is theoretically the ideal process time for one successful crystal pulling without considering crystal pulling failure, etc., stored in the control system). The actual time of each process stage is the actual process time (for example, the actual process time between the end of the last batch of material feeding and the start of crystal pulling in the high-temperature stage, which includes the time lost due to process operations such as re-crystallization after crystal pulling failure, which is greater than or equal to the theoretical process time). There is a certain difference between the two.

[0098] In other embodiments, in S400, determining the amount of dopant to be added based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization at the corresponding process stage further includes:

[0099] The doping method is selected based on the number of single-stage releases and the actual head resistance of the produced crystal rod.

[0100] If the number of single-segment triggers is less than or equal to 2, then no additional doping is required;

[0101] If the number of single-segment triggers exceeds 2, new silicon material and dopant should be added again.

[0102] This embodiment controls the volatilization of dopant elements during each process stage of the crystal pulling process by controlling the time interval ratio of each process stage. Based on experimental verification of volatilization coefficients at different operating times in different process stages, the volatilization of dopant elements is calculated for each process stage, distinguishing between high-temperature time, shoulder formation time, shoulder turning time, and finishing time. This allows for precise prediction of the dopant content at each process stage, enabling individual monitoring and supplementary doping of the volatilization of dopant elements at different process stages. This achieves reasonable control of antimony doping in crystal rods under high-volatility conditions such as antimony. By obtaining experimentally verified volatilization coefficients at different operating times in different process stages, an experimentally verified volatilization coefficient table is established to show the time-varying process stages, resulting in more accurate antimony volatilization. This improves the accuracy of antimony doping calculation and avoids problems such as inaccurate antimony doping calculations due to large deviations between the selected volatilization coefficient and the actual antimony volatilization under high-volatility conditions, which can lead to inconsistent volatilization at different process stages and thus ineffective control of antimony doping. It also avoids the problem of large errors in theoretically calculated volatilization coefficients that significantly deviate from reality.

[0103] In S500, the added dopant and new silicon material are added to a crucible containing molten silicon through a material bucket. After the added material melts, the crystal is pulled again. The amount of new silicon material added is determined according to the actual process stage where the doping needs to be added.

[0104] Optionally, in S500, the added dopant and new silicon are added to a crucible containing molten silicon via a feed bucket. After the added material melts, the crystal is pulled again, including:

[0105] Adjust the location of the added dopant based on the dosage of the added dopant and the new silicon material.

[0106] Optionally, the location of the added dopant is adjusted according to the dosage of the added dopant and the new silicon material, including:

[0107] The dopant addition is quantitatively controlled based on the proportion of the total feed amount in a single tank, and the added dopant is isolated from the molten silicon by a portion of the new silicon material. The total feed amount is the sum of the dopant addition amount and the amount of new silicon material added. When the total feed amount is less than or equal to the feed amount in a single tank, the total feed amount is equal to the total feed amount in a single tank. When the total feed amount is greater than the feed amount in a single tank, the total feed amount in a single tank is the maximum feed amount added to the tank at one time. The dopant addition point is the surface of the tank after adding silicon material accounting for 10-50% of the total feed amount in a single tank. The remaining silicon material is added after the dopant addition.

[0108] Table 5 Dopant Addition Rules

[0109] This embodiment uses quantitative control of the dopant position based on the proportion of the total feed amount in a single tank. This ensures that the dopant does not directly contact the molten silicon after being added from the feed tank. The dopant is placed on top of the bottom silicon after partially covering the molten silicon surface. The dopant is preheated during the melting of the bottom silicon, preventing direct melting and thus creating a delayed melting process. This reduces excessive dopant evaporation and improves dopant utilization. Furthermore, more silicon is placed on top of the dopant. During the feeding process, the upper silicon covers the top and surrounding areas of the dopant, extending to the molten silicon surface. This provides comprehensive coverage of the dopant, excluding the bottom and sides, further reducing dopant concentration. The dopant can directly contact the molten silicon surface, thus reducing the rapid volatilization of the dopant and improving its utilization rate. Furthermore, with appropriate silicon material covering the upper part, the volatilized antimony condenses as it passes through the silicon material upwards. As the upper silicon material melts subsequently, it remains in the molten silicon, further improving the utilization rate of antimony. The dopant position is quantitatively controlled based on the proportion of the total amount added per barrel. When adding the dopant, a sandwich-type feeding structure is formed where the dopant is protected by silicon material all around it during feeding into the molten silicon surface. This effectively solves the problem of high antimony volatility and low utilization rate, preventing the dopant from melting directly and thus creating a delayed melting process, reducing rapid volatilization and improving dopant utilization. In addition, the dopant is a metal and is located in the middle layer of the material in the addition tank (the upper and lower layers of the dopant are both silicon material). This can reduce the phenomenon of silicon jumping during the fall of the upper silicon particles, that is, small-diameter silicon particles rebound due to impact (adhere to the crucible wall and feeding device, affecting the precise control of the feeding amount and causing equipment contamination), improve the utilization rate of raw materials and avoid contamination of the material tank, etc.

[0110] Optionally, the silicon material below the dopant is called lower silicon particles, and the new silicon material above the dopant is called upper silicon particles. The particle size of the lower silicon particles is smaller than that of the upper silicon particles, with a particle size of 8-30mm. This avoids the impact of large silicon particles on the high-temperature quartz crucible during the fall, thus protecting the high-temperature quartz crucible. The smaller particle size and weight of the lower silicon particles allow them to float on the surface of the molten silicon and cover it, preventing them from sinking into the molten silicon too quickly. This provides better isolation between the dopant and the molten silicon, delays direct contact between the dopant and the molten silicon, reduces the rapid volatilization of the dopant, and improves utilization. The upper silicon particles have a larger diameter, ranging from 9 to 50 mm. This larger particle size results in greater gravity, preventing small-diameter silicon particles from "jumping" (adhering to the crucible wall and feeding device, affecting precise control of the feeding amount and contaminating the equipment). This improves raw material utilization and avoids contamination of the feed container. The greater gravity also facilitates the downward melting of silicon into the molten silicon. Furthermore, the larger particle size and wider gaps between particles allow for more dopants, such as antimony, to evaporate and condense as they pass through the silicon material. This prevents dopants from failing to evaporate due to smaller gaps, improving their dispersion and retention within the upper silicon particles. This further enhances the subsequent melting of the upper silicon material and ensures the dopants remain in the molten silicon.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure. Industrial applicability

[0112] The method disclosed herein for controlling the resistivity of group 5 element-doped crystal rods can precisely control the resistivity of different parts of the crystal rod, ensuring the consistency of parameters in subsequent silicon wafer products as much as possible. At the same time, it can also improve the problem of large fluctuations and losses in actual dopant volatilization, which is beneficial to the accurate control of dopant addition.

Claims

1. A method for controlling the resistivity of a group 5 element-doped crystal rod, characterized in that, include: S100 controls the time interval ratio of each process stage in the crystal pulling process of the furnace. The process stages include, in sequence: high temperature stage, shoulder formation stage, shoulder turning stage, and finishing stage. S200, based on experimental verification of each process stage, determines the volatility coefficient corresponding to different process stages; S300 determines the amount of doping volatilization corresponding to each process stage when running a single process stage based on the volatilization coefficient corresponding to each different process stage. S400, the amount of dopant to be added is determined based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization in the corresponding process stage; wherein, the dopant to be added is antimony; In S500, the added dopant and new silicon material are added to a crucible containing molten silicon through a material bucket. After the added material melts, the crystal is pulled again. The amount of new silicon material added is determined according to the actual process stage where the doping needs to be added. In S400, determining the amount of dopant to be added based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization in the corresponding process stage includes: The doping method is selected based on the broken wire length of the crystal rod in the crystal pulling furnace and the actual head resistance of the produced crystal rod. If the broken wire length of the crystal rod in the crystal pulling furnace is less than or equal to 200mm, then no additional doping is required. If the broken wire length of the crystal rod in the crystal pulling furnace is greater than 200mm, new silicon material and dopant need to be added again. When new material and dopant need to be added, the amount of dopant added is determined based on the target resistance requirement, the remaining silicon material content in the crucible, and the amount of dopant volatilized in the first process. The remaining silicon material content in the crucible is equal to the difference between the initial total dopant amount, the dopant amount removed during silicon liquid solidification, and the dopant volatilization amount in the second process. The first process dopant volatilization amount is the theoretical process dopant volatilization amount, and the second process dopant volatilization amount is the actual process dopant volatilization amount. The dopant is added to the surface of the material after adding 10-50% of the total amount of silicon material in the container. The remaining silicon material is added after the dopant is added. The silicon material below the dopant is the lower silicon particle, and the new silicon material above the dopant is the upper silicon particle. The lower silicon particle has a smaller particle size than the upper silicon particle, with a particle size of 8-30 mm and a particle size of 9-50 mm.

2. The method for controlling the resistivity of a group 5 element-doped crystal rod according to claim 1, characterized in that, In S100, the time interval ratio of each process stage is specifically as follows: The time interval for the high-temperature phase is 300 min - 800 min; The time interval for the shoulder relaxation phase is 200min-350min; The time interval for the shoulder rotation phase is 5-10 minutes. The time range for the closing phase is 100min-180min.

3. The method for controlling the resistivity of a group 5 element-doped crystal rod according to claim 1 or 2, characterized in that, In S300, determining the doping volatilization amount corresponding to each process stage during single-stage operation based on the volatilization coefficient corresponding to each different process stage includes: Based on the experimental verification table of volatilization coefficients for each process stage over time, the volatilization coefficients corresponding to each process stage are obtained, and the volatilization amount of the corresponding Group 5 element dopant is obtained from the volatilization coefficients.

4. The method for controlling the resistivity of a group 5 element-doped crystal rod according to any one of claims 1-3, characterized in that, The concentration of residual doping in the crucible = NA * Z1 / (resistivity corresponding to the length of the pulled crystal rod / segregation coefficient); NA = 6.02 * 10 23 ,Z1=(-3.1083-3.2626*X1-1.2196*X1 2 -0.13923*X1 3 ) / (1+1.0265*X1+0.38755*X1 2 +0.041833*X1 3 ), X1 = log 10 (Resistivity / Segregation Coefficient corresponding to the length of the pulled crystal rod) Doping concentration of the pulled crystal rod = NA * initial doping concentration * (1 - solidification ratio) (0.35-1) / (1-initial solidification ratio) (0.35-1) ; The doping concentration extracted from the solidified silicon melt is calculated as: doping concentration of the pulled crystal rod / segregation coefficient; segregation coefficient = 0.

023. Target resistance required doping concentration = NA * Z2 / target resistance; NA = 6.02 * 10 23 ,Z2=(-3.1083-3.2626*X2-1.2196*X2 2 -0.13923*X2 3 ) / (1+1.0265*X2+0.38755*X2 2 +0.041833*X2 3 ), X2 = log 10 (Target resistivity / segregation coefficient); Initial doping amount = initial doping concentration / segregation coefficient; First-stage doping volatilization amount = target time of each process stage * volatilization coefficient; The amount of doped volatilization in the second process = the actual time of each process stage * the volatilization coefficient.

5. The method for controlling the resistivity of a group 5 element-doped crystal rod according to claim 4, characterized in that, In S200, based on experimental verification of each process stage, the volatility coefficients corresponding to different process stages are determined, including: The volatility coefficient during the high-temperature stage is 0.05 to 2.2; The volatility coefficient during the shoulder-setting stage is 0.05-0.35; The volatility coefficient during the shoulder-turning stage is 0.05 to 0.1; The volatility coefficient of the final stage is 0.1 to 0.

25.

6. The method for controlling the resistivity of a group 5 element-doped crystal rod according to any one of claims 1-5, characterized in that, In S400, determining the amount of dopant to be added based on the actual process stage where the doping needs to be supplemented and the amount of dopant volatilization in the corresponding process stage further includes: The doping method is selected based on the number of single-stage releases and the actual head resistance of the produced crystal rod. If the number of single-segment triggers is less than or equal to 2, then no additional doping is required; If the number of single-segment triggers exceeds 2, new silicon material and dopant should be added again.

7. The method for controlling the resistivity of a group 5 element-doped crystal rod according to any one of claims 1 to 6, characterized in that, In S500, the process of adding dopant and new silicon material to a crucible containing molten silicon via a feed bucket, and then re-pulling the crystal after the added material has melted, includes: The dopant addition location is adjusted according to the dosage of the added dopant and the new silicon material. The dopant addition location is quantitatively controlled as a percentage of the total amount added to a single tank. The added dopant is partially isolated from the molten silicon by the new silicon material. The total amount added is the sum of the dopant addition amount and the amount of new silicon material added. When the total amount added is less than or equal to the amount added to a single tank, the total amount added is equal to the total amount added to a single tank. When the total amount added is greater than the amount added to a single tank, the total amount added to a single tank is the maximum amount added to the tank in a single batch.

Images