Monocrystalline silicon czochralski thermal field
By using a multi-stage heater system during the direct pulling growth of single crystal silicon, the heating stage and heating power of each heater are independently controlled, and the problem of oxygen atoms entering the silicon melt in the quartz crucible is solved, achieving the effect of reducing the oxygen content of single crystal silicon and improving the quality of single crystal silicon.
Patent Information
- Application Number
- CN202420713756.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-08
- Publication Date
- 2025-05-13
- Estimated Expiration
- 2034-04-08
AI Technical Summary
During the direct pulling growth of single crystal silicon, oxygen atoms in the quartz crucible easily enter the silicon melt, resulting in an increase in the oxygen content in the single crystal silicon, affecting the resistivity and photoelectric conversion rate of the battery cell.
A multi-stage heater system is adopted, including a main heater, a secondary heater and a bottom heater, which are arranged around the sides and bottom of the quartz crucible respectively. By independently controlling the heating stage and heating power of each heater, the heat field of the quartz crucible is regulated to reduce the generation of oxygen elements.
It effectively reduces the amount of oxygen atoms in the quartz crucible entering the silicon melt, reduces the oxygen content in single crystal silicon, improves the quality of single crystal silicon, and avoids silicon material crystallization accidents.
Smart Images
Figure CN222861707U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to a single crystal silicon direct-pull thermal field. Background Art
[0002] In the process of preparing single crystal silicon by Czochralski method, the container for holding silicon raw materials is generally a quartz crucible. During the entire crystal growth process, the quartz crucible is always kept at a high temperature of not less than 1420℃. In the initial stage of equal diameter and melting silicon material, the temperature of the quartz crucible is higher. Under high temperature, the inner surface of the quartz crucible contacts with molten silicon and undergoes chemical reaction to generate silicon monoxide (SiO), and a large number of oxygen atoms enter the silicon melt through convection and diffusion. Although most of the oxygen atoms evaporate in the form of SiO gas on the surface of the silicon melt and are then taken away by the high-purity argon gas in the single crystal furnace, there is still a small part of SiO that will decompose at the solid-liquid interface. Among them, the separated oxygen will enter the single crystal silicon rod through condensation along the solid-liquid interface and form Si-O-Si bonds with adjacent silicon atoms. The oxygen atoms will form oxygen defects in the single crystal silicon in the form of interstitial atoms, which increases the oxygen content in the Czochralski single crystal silicon. These oxygen impurities will precipitate into oxygen precipitates during the subsequent processing and heat treatment of single crystal silicon, thereby forming secondary defects such as bulk micro-defects and oxidation-induced stacking faults in the silicon wafer. These defects will reduce the minority carrier lifetime of silicon-based solar cells, affect the resistivity of the cells, and thus reduce the photoelectric conversion rate of solar cells. Utility Model Content
[0003] In view of this, the utility model provides a single crystal silicon CZ thermal field, which can effectively reduce the oxygen atoms in the quartz crucible entering into the silicon melt, so as to effectively reduce the oxygen content in the growing single crystal silicon rod.
[0004] In order to solve the above technical problems, the utility model provides the following technical solutions:
[0005] In a first aspect, the utility model provides a single crystal silicon direct pull thermal field, comprising:
[0006] Quartz crucible,
[0007] A main heater is arranged around the side of the quartz crucible,
[0008] a secondary heater disposed around the side of the quartz crucible and below the primary heater, and
[0009] The bottom heater is located below the quartz crucible; the auxiliary heater comprises: a heating structure and two accommodating cavities arranged opposite to each other, wherein:
[0010] The two accommodating cavities and the heating structure form a ring structure;
[0011] The accommodating cavity is used to accommodate the heating electrode of the main heater;
[0012] The main heater, the sub-heater, and the bottom heater are each independently controlled.
[0013] In a second aspect, the present invention provides a method for growing single crystal silicon using a single crystal silicon direct-pull thermal field based on the first aspect of the present invention, including:
[0014] Step 1: Before the growth of single crystal silicon enters the equal diameter stage, the main heater and the auxiliary heater arranged around the side of the quartz crucible in the single crystal furnace and the bottom heater arranged at the bottom of the quartz crucible jointly provide heat for the quartz crucible;
[0015] Step 2: When the growth of the silicon single crystal enters the first stage of the equal diameter stage, the auxiliary heater and the bottom heater are turned off, and the main heater alone provides heat for the quartz crucible;
[0016] Step 3: When the growth of single crystal silicon enters the second stage of the equal diameter stage from the first stage, the bottom heater remains closed and the auxiliary heater is turned on, and the main heater and the auxiliary heater jointly provide heat for the quartz crucible.
[0017] The technical solution of the first aspect of the above utility model has the following advantages or beneficial effects:
[0018] The single crystal silicon direct pulling thermal field provided by the embodiment of the utility model is provided with a main heater, a sub-heater and a bottom heater which are independently controlled, wherein the main heater and the sub-heater are arranged around the side of the quartz crucible in the single crystal furnace, and the main heater is located above the sub-heater, and the bottom heater is arranged below the quartz crucible. The sub-heater accommodates the heating electrode of the main heater through the accommodating cavity, so that the main heater and the sub-heater can be arranged on the side of the quartz crucible in a structurally complementary manner without affecting the overall structural design of the single crystal silicon direct pulling thermal field. The main heater, the sub-heater and the bottom heater are independently controlled. Through research, it is found that this structure can reduce the amount of oxygen generated by the quartz crucible by regulating the heating stage and heating power of the main heater, the sub-heater and the bottom heater.
[0019] Furthermore, the main heater can heat the quartz crucible alone, so that heat convection can be generated between the hot silicon melt in the upper part of the quartz crucible and the cold silicon melt in the lower part. The heat convection can inhibit the flow of oxygen elements to the surface of the silicon melt, so as to further reduce the oxygen content on the surface of the silicon melt, so that the oxygen content of the head of the single crystal silicon can be controlled. In addition, when the growth of single crystal silicon enters the second stage of the equal diameter stage from the first stage, the bottom heater remains closed, and the auxiliary heater is turned on. The main heater and the auxiliary heater jointly heat the quartz crucible, so that the heated area of the quartz crucible moves downward, avoiding the crystallization accident of silicon material caused by the reduction of silicon material and the slowdown of heat convection in the quartz crucible, and can ensure the quality of the grown single crystal silicon. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a schematic diagram of a partial cross-sectional structure of a single crystal silicon CZ thermal field provided by the prior art;
[0021] Figure 2 It is a schematic diagram of a partial cross-sectional structure of an existing quartz crucible after it is raised in the equal diameter stage in the single crystal silicon CZ thermal field provided by the prior art;
[0022] Figure 3 It is a schematic diagram of a partial cross-sectional structure of a single crystal silicon CZ thermal field according to an embodiment of the utility model;
[0023] Figure 4 It is a partial cross-sectional structural schematic diagram of the relative position relationship between the quartz crucible, the main heater and the auxiliary heater in the material-forming stage of the single crystal silicon CZ thermal field according to the embodiment of the utility model;
[0024] Figure 5 It is a partial cross-sectional structural schematic diagram of the relative positional relationship between the quartz crucible, the main heater and the auxiliary heater after the quartz crucible is raised in the equal diameter stage of Czochralski single crystal silicon pulling thermal field according to an embodiment of the utility model;
[0025] Figure 6 This is a schematic diagram of a first three-dimensional structure of a secondary heater according to an embodiment of the utility model;
[0026] Figure 7 is a schematic diagram of a second three-dimensional structure of a secondary heater according to an embodiment of the utility model;
[0027] Figure 8 According to the embodiment of the utility model Figure 6 The schematic diagram of the structure of the auxiliary heater and the main heater shown;
[0028] Fig. 9 According to the embodiment of the utility model Figure 7 The schematic diagram of the structure of the auxiliary heater and the main heater shown;
[0029] Fig.10 It is a schematic diagram of the main process of a single crystal silicon Czochralski process based on a single crystal silicon Czochralski thermal field according to an embodiment of the utility model.
[0030] The reference numerals are as follows:
[0031] 1-main heater; 2-secondary heater; 21-heating structure; 211-heating body; 212-connecting assembly;
[0032] 2121-additional connecting strip; 2122-additional connecting plate; 213-heating electrode; 22-accommodating cavity; 3-bottom heater; 40-single crystal furnace; 41-quartz crucible; 50-existing side heater; 60-existing bottom heater. DETAILED DESCRIPTION
[0033] In order to control the oxygen impurities in the silicon melt from the quartz crucible into the single crystal silicon, the following methods are generally used to solve the problem:
[0034] 1. Accelerate the speed at which oxygen impurities evaporate and are carried away by argon gas. This method generally improves the space distance of the hot field airflow channel such as the guide tube and the insulation tube, or increases the argon gas flow rate to increase the vacuum pump's pumping speed.
[0035] 2. Slow down the speed of oxygen impurities in the silicon melt entering the single crystal silicon from the crystal growth interface. This method is generally adjusted from the crystal pulling process, and the parameters such as the crucible position, crystal rotation, and crucible rotation of the quartz crucible are adjusted to improve the form of convection in the quartz crucible, so that the concentration of oxygen impurities entering the single crystal silicon changes, thereby reducing the oxygen content.
[0036] 3. Reduce the oxygen content in the silicon liquid from the quartz crucible. Currently, the main way to reduce the oxygen content in the silicon liquid from the quartz crucible is in the process of producing single crystal silicon, such as Figure 1 and Figure 2 As shown, an existing side heater 50 is arranged on the side of the quartz crucible and an existing bottom heater 60 is arranged on the bottom of the quartz crucible. In the initial stage of material fusion, by adjusting the height of the quartz crucible, the existing bottom heater 60 heats the bottom area of the quartz crucible, and the existing side heater 50 heats the upper area of the quartz crucible, that is, the length of the heating zone of the existing side heater 50 is reduced, thereby reducing the heating area of the quartz crucible by the existing side heater 50, reducing the melting area of the inner layer of the quartz crucible, and reducing the oxygen impurities entering the silicon melt.
[0037] However, although the above-mentioned method of "accelerating the rate at which oxygen impurities evaporate and are carried away by argon gas" can alleviate the oxygen content in the single crystal silicon rod, it does not essentially weaken the amount of oxygen elements entering the silicon melt, that is, the oxygen content in the silicon melt is not actually reduced. Therefore, the impact of this method of accelerating the evaporation of oxygen impurities is limited, and when the price of argon gas rises, it will also cause an increase in costs.
[0038] Regarding the above-mentioned method of "slowing down the speed at which oxygen impurities in the silicon melt enter the single crystal silicon from the crystal growth interface", due to the limitations of the process itself, it requires a high level of technical skills from the personnel who adjust the process. If the process is not adjusted properly, it may have the opposite effect, causing the oxygen content in the single crystal silicon to increase instead of decrease.
[0039] Regarding the above existing method of "reducing the oxygen content in the silicon liquid entering the quartz crucible", as Figure 2 As shown, in the initial stage of the melting, the upper wall of the quartz crucible is severely burned, and the local heat is large, which reduces the service life of the quartz crucible. At the same time, as the silicon material is pulled less and less, the crucible rises, and the distance from the existing bottom heater 60 increases. The bottom of the crucible is less radiated by the existing bottom heater 60, and the silicon melt at the bottom of the crucible is prone to crystallization, thereby causing serious production accidents.
[0040] In order to solve the above problems existing in the prior art, the embodiments of the present invention provide a single crystal silicon Czochralski thermal field and a single crystal silicon Czochralski process.
[0041] The single crystal silicon CZ thermal field involved in the embodiment of the utility model generally includes a combination of equipment, components and other structures required for producing single crystal silicon through CZ technology. For example, the single crystal silicon CZ thermal field may include: a single crystal furnace, a quartz crucible containing silicon material located in the single crystal furnace, a thermal system for heating silicon material, a water cooling system arranged around the single crystal furnace, a water cooling heat shield located in the single crystal furnace, a CZ control device located outside the single crystal furnace, a monitoring component, etc. The embodiment of the utility model is mainly aimed at improving the thermal system, which cooperates with the quartz crucible to effectively reduce the oxygen element in the quartz crucible from entering the silicon melt and suppress the oxygen content on the surface of the silicon melt, thereby ensuring the quality of the single crystal silicon.
[0042] Among them, the cross-section involved in the embodiment of the utility model refers to a partial cutting surface obtained by cutting the single crystal furnace parallel to the axis of the single crystal furnace included in the single crystal silicon direct pulling hot place.
[0043] in, Figures 3 to 5 The cross-sectional structure of the single crystal silicon CZ thermal field provided by the utility model embodiment is shown; Figures 3 to 5 A schematic diagram showing the relative position relationship between the main heater and the auxiliary heater in the single crystal silicon direct pulling thermal field.
[0044] like Figures 3 to 5 As shown, the single crystal silicon direct pull thermal field provided by the embodiment of the utility model may include:
[0045] Quartz crucible 41,
[0046] The main heater 1 is arranged around the side of the quartz crucible 41,
[0047] a secondary heater 2 disposed around the side of the quartz crucible 41 and located below the primary heater 1, and
[0048] The bottom heater 3 is located below the quartz crucible 41; the auxiliary heater 2 includes: a heating structure 21 and two accommodating cavities 22 arranged opposite to each other, wherein:
[0049] The two accommodating chambers 22 and the heating structure 21 form a ring structure;
[0050] The accommodating cavity 22 is used to accommodate the heating electrode of the main heater 1;
[0051] The main heater 1 , the sub-heater 2 and the bottom heater 3 are each independently controlled.
[0052] It can be understood that the main heater 1, the auxiliary heater 2 and the bottom heater 3 involved in the embodiment of the utility model are the main parts of the thermal system in the single crystal silicon direct pull thermal field, which is only a part of the single crystal silicon direct pull thermal field.
[0053] Among them, the main heater 1 and the auxiliary heater 2 are arranged around the side of the quartz crucible 21, which generally means that the cross-sections of the main heater 1 and the auxiliary heater 2 perpendicular to the axis direction of the quartz crucible 21 are both circular ring structures, and the centers of the circular ring structures are both located on the axis of the quartz crucible 21.
[0054] Among them, in the single crystal silicon direct pulling thermal field provided by the embodiment of the utility model, in the process of producing single crystal silicon rods by direct pulling, as Figure 4 and Figure 5 As shown, as the amount of molten silicon in the quartz crucible 41 decreases, the quartz crucible 41 will move upward to ensure that the distance between the interface of the molten silicon and the lower end of the single crystal silicon rod can remain substantially unchanged.
[0055] The single crystal silicon involved in the embodiments of the present utility model generally refers to a single crystal silicon rod obtained by the single crystal silicon direct pulling hot field direct pulling provided by the embodiments of the present utility model.
[0056] The auxiliary heater 2 includes a heating structure 21 and two accommodating cavities 22 arranged opposite to each other, wherein the two accommodating cavities 22 and the heating structure 21 form a ring structure; the accommodating cavity 22 accommodates the heating electrode of the main heater 1. Figure 6 and Figure 7 The structure of the auxiliary heater can ensure the coordination between the main heater 1 and the auxiliary heater 2, wherein, during the use of the auxiliary heater 2, Figure 6 and Figure 7The direction A→D shown is from the upper part of the sub-heater 2 to the bottom part of the sub-heater 2. That is, when the sub-heater is in use, the two heating electrodes 213 of the sub-heater 2 face downward.
[0057] The two accommodating cavities 22 and the heating structure 21 forming a ring structure means that the two accommodating cavities 22 and the heating structure 21 are both part of the ring structure.
[0058] By setting the accommodating cavity 22, the auxiliary heater 2 and the main heater 1 can be well matched without increasing the space occupied in the silicon crystal furnace.
[0059] The above-mentioned single crystal silicon direct pulling thermal field is achieved by setting up a main heater, a sub-heater and a bottom heater which are independently controlled, wherein the main heater and the sub-heater are arranged around the side of the quartz crucible in the single crystal furnace, and the main heater is located above the sub-heater, and the bottom heater is arranged below the quartz crucible. The sub-heater accommodates the heating electrode of the main heater through the accommodating cavity, so that the main heater and the sub-heater can be arranged on the side of the quartz crucible in a structurally complementary manner without affecting the overall structural design of the single crystal silicon direct pulling thermal field. The main heater, the sub-heater and the bottom heater are independently controlled. Through research, it is found that this structure can reduce the amount of oxygen generated in the quartz crucible by regulating the heating stage and heating power of the main heater, the sub-heater and the bottom heater.
[0060] Further, with respect to the single crystal silicon CZ thermal field provided in the embodiment of the utility model, before the growing single crystal silicon enters the equal diameter stage, the main heater 1, the auxiliary heater 2 and the bottom heater 3 jointly provide heat for the quartz crucible 41;
[0061] In the first stage when the growth of single crystal silicon enters the equal diameter stage, the auxiliary heater 2 and the bottom heater 3 are turned off, and the main heater 1 alone provides heat for the quartz crucible 41;
[0062] When the growth of single crystal silicon enters the second stage of the equal diameter stage from the first stage, the bottom heater 3 remains closed, and the auxiliary heater 2 is turned on. The main heater 1 and the auxiliary heater 2 jointly provide heat for the quartz crucible 41 .
[0063] It is worth noting that the single crystal silicon direct pulling thermal field provided in the embodiment of the utility model mainly involves several growth stages (material-making stage, seed crystal contact stage, thin neck stage, shoulder release stage, equal diameter stage and finishing stage) in the process of producing single crystal silicon by direct pulling, and these growth stages are basically consistent with the prior art. Among them, since the duration of the seed crystal contact stage, the thin neck stage and the finishing stage is relatively short, and the consumption of silicon melt in the seed crystal contact stage, the thin neck stage and the finishing stage is relatively small, therefore, the material-making stage and the equal diameter stage are the main stages affecting the growth of single crystal silicon. The combined regulation of the main heater 1, the auxiliary heater 2 and the bottom heater 3 designed in the embodiment of the utility model cooperates with the material-making stage and the equal diameter stage, which can effectively reduce the oxygen element in the quartz crucible 41 from entering the silicon melt.
[0064] For the seed crystal contact stage, the thin neck stage, the shoulder release stage and the finishing stage, the regulation of the main heater 1, the auxiliary heater 2 and the bottom heater 3 can be merged into the material stage or the equal diameter stage according to the needs. For example, the seed crystal contact stage, the thin neck stage and the shoulder release stage are merged into the material stage, and the finishing stage is merged into the equal diameter stage. In addition, based on the regulation of the main heater 1, the auxiliary heater 2 and the bottom heater 3 in the equal diameter stage provided by the embodiment of the utility model, the main heater 1, the auxiliary heater 2 and the bottom heater 3 can be adaptively regulated in the seed crystal contact stage, the thin neck stage, the shoulder release stage and the finishing stage.
[0065] Specifically, the combined regulation of the main heater 1, the auxiliary heater 2 and the bottom heater 3 provided by the embodiment of the utility model is specifically implemented in coordination with the material stage and the equal diameter stage as described above. Before the growing single crystal silicon enters the equal diameter stage, the main heater 1, the auxiliary heater 2 and the bottom heater 3 jointly supply heat to the quartz crucible 41. Specifically, in the material chemical stage, the heating power ranges of the main heater 1, the auxiliary heater 2 and the bottom heater 3 can be: the heating power of the main heater 1 can be controlled at 60-100kw (for example, the heating power of the main heater 1 can be 80kw, 85kw, 88kw, 90kw, 92kw, 95kw, 100kw, etc.), the heating power of the auxiliary heater 2 can be controlled at 60-100kw (for example, the heating power of the auxiliary heater 2 can be 60kw, 65kw, 70kw, 75kw, 85kw, 90kw, 95kw, 100kw, etc.), and the heating power of the bottom heater 3 can be controlled at 60-100kw (for example, the heating power of the bottom heater 3 can be 60kw, 65kw, 70kw, 75kw, 80kw, 85kw, 95kw, 100kw, etc.). Generally speaking, in the stage of material formation, the heating power of the auxiliary heater 2 and the bottom heater 3 is not less than the heating power of the main heater 1. On the one hand, it can ensure that the silicon material in the quartz crucible 41 can be quickly and completely melted to form silicon melt; on the other hand, it can ensure that the quartz crucible 41 is evenly heated to avoid deformation of the quartz crucible caused by local overheating of the quartz crucible 41. In addition, in this material formation stage, since the heating area is relatively large, the time used for material formation can be shortened. And through the cooperation of the main heater, the auxiliary heater and the bottom heater, the problem of excessively high local temperature of the outer layer of the quartz crucible in the material formation stage is solved, thereby reducing the influence of high temperature on the inner wall of the quartz crucible, thereby improving the life of the quartz crucible.
[0066] After the chemical reaction is completed, the single crystal silicon grown in the single crystal silicon direct pulling thermal field is in a stable stage and a necking stage, the bottom heater 3 is turned off, and the heating powers of the main heater 1 and the auxiliary heater 2 are reduced to a total heating power of the main heater 1 and the auxiliary heater 2 controlled at 60-70 kW. For example, the heating power of the main heater is 50 kW, and correspondingly, the heating power of the auxiliary heater 2 needs to be controlled at 10-20 kW (for example, 10 kW, 15 kW, 20 kW, etc.); for another example, the heating power of the main heater is 55 kW, and correspondingly, the heating power of the auxiliary heater 2 needs to be controlled at 5-15 kW (for example, 5 kW, 8 kW, 10 kW, 15 kW, etc.).
[0067] Furthermore, by supplying heat to the quartz crucible 41 solely through the main heater 1 during the first stage of the growing single crystal silicon entering the equal diameter stage, and turning off the auxiliary heater 2 and the bottom heater 3, the hot silicon melt in the upper part of the quartz crucible 41 convects with the silicon melt in the lower part with a relatively low temperature. On the one hand, it can ensure that the silicon material in the quartz crucible 41 remains in a molten state to avoid crystallization of the silicon material; on the other hand, it can reduce the heating of the quartz crucible 41, reduce the oxygen content generated by melting in the middle and lower parts and the bottom of the quartz crucible, thereby reducing the generation of oxygen in the quartz crucible 41; in addition, the convection between the hot silicon melt in the upper part of the quartz crucible 41 and the silicon melt in the lower part with a relatively low temperature can inhibit the flow of oxygen to the surface of the silicon melt, effectively reduce the oxygen content on the surface of the silicon melt, and thus effectively control the oxygen content in the growing single crystal silicon.
[0068] Compared with the heating power of the main heater 1 before the growth of single crystal silicon enters the equal diameter stage, the heating power of the main heater 1 in the first stage of the equal diameter stage of the growth of single crystal silicon increases. In the first stage of the equal diameter stage, the heating power of the main heater 1 is generally 55kw to 65kw. For example, the heating power of the main heater 1 can be 55kw, 58kw, 60kw, 62kw, 65kw, etc. Among them, compared with the growth of single crystal silicon before entering the equal diameter stage, the heating power of the main heater 1 in the first stage increases by no more than 5kw. For example, before the growth of single crystal silicon enters the equal diameter stage, the heating power of the main heater 1 is 50kw, and the heating power of the main heater 1 in the first stage can be 52kw, 53kw, 54kw, 55kw, etc. For another example, before the growth of single crystal silicon enters the equal diameter stage, the heating power of the main heater 1 is 55kw, and the heating power of the main heater 1 in the first stage can be 56kw, 57kw, 58kw, 59kw, etc. That is, in the first stage when the growth of silicon single crystal enters the equal diameter stage, the heating power of the main heater 1 is gradually increased to make the silicon single crystal grow with equal diameter. Among them, the increase frequency and increase trend of the heating power of the main heater 1 are related to the single crystal silicon CZ rate or the diameter of the single crystal silicon growth. For example, when the single crystal silicon diameter remains unchanged, the single crystal silicon CZ rate increases, indicating that the silicon melt crystallizes faster, and the increase frequency of the heating power of the main heater 1 can be accelerated; when the single crystal silicon CZ rate remains unchanged, but the single crystal silicon diameter increases, it means that the silicon melt crystallizes faster, and the increase frequency of the heating power of the main heater 1 can be accelerated.
[0069] In addition, after the growth of single crystal silicon enters the second stage in the equal diameter stage from the first stage, by turning on the auxiliary heater 2, the main heater 1 and the auxiliary heater 2 jointly supply heat to the quartz crucible 41. Among them, the heating power of the second stage exceeds the heating power of the first stage, and in the second stage, the heating power of the auxiliary heater is not higher than 10kw. Compared with the first stage, as the silicon melt decreases, by turning on the auxiliary heater 2, the heated area of the quartz crucible 41 moves downward, which can avoid crystallization accidents caused by the low temperature of the silicon material at the bottom of the quartz crucible 40. In addition, since the silicon liquid becomes less significantly in the second stage, resulting in a faster heat dissipation of the silicon liquid, by turning on the auxiliary heater 2, the silicon liquid can also be prevented from recrystallizing in the quartz crucible 41, thereby improving the safety of the equal diameter process.
[0070] In the second stage, the heating power of the main heater 1 can be gradually reduced, and the heating power of the auxiliary heater 2 can be gradually increased, and the heating power of the main heater 1 is still higher than the heating power of the auxiliary heater 2. Among them, the difference between the heating power of the auxiliary heater 2 and the heating power of the auxiliary heater 2 before the growth of the single crystal silicon enters the equal diameter stage generally does not exceed 5kw. That is, in the second stage when the growth of the single crystal silicon enters the equal diameter stage, the heating power of the auxiliary heater 2 is gradually increased so that the single crystal silicon continues to grow in equal diameter. Among them, the increase frequency and increase trend of the heating power of the auxiliary heater 2 are related to the single crystal silicon vertical pulling rate or the diameter of the single crystal silicon growth. For example, when the single crystal silicon diameter remains unchanged, the single crystal silicon vertical pulling rate increases, indicating that the silicon melt crystallizes faster, and the increase frequency of the heating power of the auxiliary heater 2 can be accelerated; when the single crystal silicon vertical pulling rate remains unchanged, but the single crystal silicon diameter increases, it means that the silicon melt crystallizes faster, and the increase frequency of the heating power of the auxiliary heater 2 can be accelerated.
[0071] In summary, in the embodiment of the present utility model, in the first stage and the second stage, the heating power of the main heater 1 and the heating power of the auxiliary heater 2 can be automatically regulated according to the growth conditions of the single crystal silicon.
[0072] Specifically, the first stage in which the single crystal silicon involved in the embodiment of the utility model enters the equal diameter stage generally refers to the stage in which the growing single crystal silicon enters the equal diameter stage after the shoulder release stage is completed (for example, if you want to obtain a single crystal silicon with a diameter of 260 mm, then when the diameter of the growing single crystal silicon reaches about 250 mm, it can be considered that the single crystal silicon enters the equal diameter stage).
[0073] The first and second stages of the isodiameter stage can be determined according to the actual length of the single crystal silicon to be produced. Generally speaking, the first stage refers to the period from when the growing single crystal silicon enters the isodiameter stage to when the length of the single crystal silicon grown in the isodiameter stage reaches 500 mm. The second stage refers to when the length of the single crystal silicon grown in the isodiameter stage exceeds 500 mm.
[0074] It is worth noting that in the embodiment of the present invention, the amount of molten silicon contained in the quartz crucible 41 matches the amount of molten silicon required to produce a single single crystal silicon rod. Therefore, the first stage and the second stage involved in the embodiment of the present invention can be determined based on the length of the single crystal silicon.
[0075] Among them, the bottom heater 3 provided in the embodiment of the utility model is only used as a device to ensure the safety of the material stage. In the above-mentioned second stage, the auxiliary heater 2 can ensure the control of oxygen content and the regulation of non-crystallization of the silicon melt. Therefore, there is no need to turn on the bottom heater 3 in the above-mentioned second stage to effectively control the energy consumption of single crystal silicon production.
[0076] It is worth noting that in each stage of single crystal silicon growth (chemical reaction stage, stabilization stage, necking stage, the first stage in the equal-diameter stage and the second stage in the equal-diameter stage), the change trend of controlling the heating power of the main heater 1, the auxiliary heater 2 and the bottom heater 3 is consistent with the present application. For example, in the chemical reaction stage, the heating power of the auxiliary heater 2 and the bottom heater 3 is not less than the heating power of the main heater 1; in the stabilization stage and the necking stage, the bottom heater 3 is turned off, and the main heater 1 and the auxiliary heater 2 are heated together; in the first stage of the equal-diameter stage, the quartz crucible 41 is heated by the main heater 1 alone, and compared with before the equal-diameter stage, the heating power of the main heater 1 in the first stage is increased, and the auxiliary heater 2 and the bottom heater 3 are turned off; in the second stage of the equal-diameter stage, the main heater 1 and the auxiliary heater 2 jointly heat the quartz crucible 41, the heating power of the second stage exceeds the heating power of the first stage, and in the second stage, the heating power of the auxiliary heater will not be higher than the heating power of the main heater, etc., all of which are obtained through a series of studies. The heating power ranges of the main heater 1, the auxiliary heater 2 and the bottom heater 3 involved in the embodiments of the present invention are merely exemplary ranges applicable to the ranges required for most single crystal silicon production, and do not constitute a limitation on the heating power of the main heater 1, the auxiliary heater 2 and the bottom heater 3. For those skilled in the art, the heating power of the main heater 1, the auxiliary heater 2 and the bottom heater 3 can be adaptively adjusted up or down based on the heating power given in this application according to the crucible size, the amount of silicon material, the size of the single crystal silicon produced, etc.
[0077] In view of the single crystal silicon direct pulling thermal field provided by the embodiment of the utility model, a main heater, an auxiliary heater and a bottom heater which are independently controlled are provided, wherein the main heater and the auxiliary heater are provided around the side of the quartz crucible in the single crystal furnace, and the main heater is located above the auxiliary heater, and the bottom heater is provided below the quartz crucible, and before the growth of the single crystal silicon enters the equal-diameter stage, the main heater, the auxiliary heater and the bottom heater jointly supply heat to the quartz crucible so that the crystalline silicon used for growing the single crystal silicon can be completely melted into silicon liquid, and further in the first stage of the growth of the single crystal silicon entering the equal-diameter stage, the auxiliary heater and the bottom heater are turned off, and the main heater alone supplies heat to the quartz crucible, reducing the heat supply to the quartz crucible, which can reduce the amount of oxygen generated by the quartz crucible, and in addition, the main heater alone supplies heat to the quartz crucible, which can generate thermal convection between the hot silicon melt in the upper part of the quartz crucible and the cold silicon melt in the lower part, and the thermal convection can inhibit the oxygen element from flowing to the surface of the silicon melt, so as to further reduce the oxygen content on the surface of the silicon melt, so that the oxygen content at the head of the single crystal silicon is controlled. In addition, when the growth of single crystal silicon enters the second stage of the equal diameter stage from the first stage, the bottom heater remains closed and the auxiliary heater is turned on. The main heater and the auxiliary heater jointly supply heat to the quartz crucible, so that the heated area of the quartz crucible moves downward, avoiding silicon material crystallization accidents caused by the reduction of silicon material and the slowdown of heat convection in the quartz crucible, and can ensure the quality of the grown single crystal silicon.
[0078] Furthermore, in order to enable the main heater 1, the sub-heater 2 and the bottom heater 3 to cooperate better, the main heater 1 provided in the embodiment of the utility model is arranged corresponding to the upper half of the quartz crucible 41. Preferably, the lower edge of the main heater 1 (the lower edge of the main heater 1 refers to the lower edge of the heating body of the main heater 1) is located at one-half of the quartz crucible 41.
[0079] Furthermore, the auxiliary heater 2 is located in the lower half of the quartz crucible 41 , and the distance from the lower edge of the auxiliary heater 2 to the bottom of the quartz crucible 41 is one third of the height of the quartz crucible 41 , so as to further enhance the auxiliary heating effect of the auxiliary heater 2 as the main heater 1 .
[0080] Further, with respect to the heating structure 21 of the auxiliary heater 2, as Figure 6 and Figure 7 As shown, the heating structure 21 may include: two heating bodies 211, two connecting components 212 and two heating electrodes 213, wherein:
[0081] The cross-section of the two heating bodies 211 is an arc-shaped structure;
[0082] The two ends of the two heating bodies 211 are fixedly connected to the two connecting components 212 respectively;
[0083] Each connecting assembly 212 and the ends of the two heating bodies 211 connected thereto enclose a receiving cavity 22;
[0084] The two heating electrodes 213 are fixedly connected to the two heating bodies 211 respectively.
[0085] By designing two connection components 212 , the two connection components 212 connect the two heating bodies 211 , so that the heating structure 21 can form a closed loop.
[0086] The design of two heating bodies 211 , two connecting components 212 and two heating electrodes 213 facilitates assembly and disassembly of the auxiliary heater 2 .
[0087] Among them, Figure 6 and Figure 7 As shown, the connection assembly 212 may include: an additional connection bar 2121 of a frame-shaped structure and two additional connection plates 2122, wherein:
[0088] The two additional connecting plates 2122 respectively fix the two ends of the additional connecting strip 2121 to the ends of the two heating bodies 211;
[0089] The frame-shaped structure and the ends of the two heating bodies 211 surround an accommodating cavity 22 .
[0090] The frame structure can be Figure 7 The rectangular frame structure shown in FIG. 1 may also be Figure 5 The frame structure formed by the semicircular ring and the rod shown. In addition, the frame structure can also be in other shapes, and the specific shape of the frame structure is not limited here, as long as the accommodating cavity 22 formed by the end of the frame structure and the two heating bodies 211 can accommodate the heating electrode of the main heater 1.
[0091] It is worth noting that in the structure of the auxiliary heater 2 provided in the embodiment of the utility model, except for the bolts which are made of carbon-carbon (CC) material, the remaining materials such as the heating structure, connecting components, etc. are all made of isostatic graphite.
[0092] Among them, for Figure 6 The structure of the auxiliary heater 2 shown in the figure is as follows after being spliced with the main heater 1 Figure 8 shown.
[0093] against Figure 7 The structure of the auxiliary heater 2 shown in the figure is as follows after being spliced with the main heater 1 Fig. 9 shown.
[0094] In the process of using the main heater 1 and the auxiliary heater 2, Figure 8 and Fig. 9The direction A→D shown is the upper part of the main heater 1→the lower part of the heating structure of the main heater 1→the upper part of the sub-heater 2→the bottom of the sub-heater 2. That is, during the use of the main heater 1 and the sub-heater 2, the heating electrodes of the main heater 1 and the sub-heater 2 are both facing downward.
[0095] Furthermore, if Figure 8 and Fig. 9 As shown, the lower surface of the heating electrode of the main heater 1 and the lower surface of the heating electrode 213 included in the sub-heater 2 are located in the same plane, so as to facilitate the connection of the heating electrode of the main heater 1 and the heating electrode 213 included in the sub-heater 2 with an external power source.
[0096] Furthermore, if Figures 6 to 9 As shown, the heating body 211 is designed as a serpentine structure to increase the resistance of the heating body 211 and provide heat better, so as to facilitate the subsequent regulation of the heat provided by the auxiliary heater 2 by regulating the heating power of the auxiliary heater 2.
[0097] Furthermore, if Figures 6 to 9 As shown, the heating body of the main heater 1 can also be designed as a serpentine structure to increase the resistance of the heating body of the main heater 1 and provide heat better, so as to facilitate the subsequent regulation of the heat provided by the main heater 1 by regulating the heating power of the main heater 1.
[0098] Furthermore, the embodiment of the utility model provides a single crystal silicon Czochralski process implemented by a single crystal silicon Czochralski thermal field based on any of the above embodiments. Fig.10 As shown, the single crystal silicon Czochralski process may include the following steps:
[0099] Step S1001: before the growth of single crystal silicon enters the equal diameter stage, the main heater 1 and the auxiliary heater 2 arranged around the side of the quartz crucible 41 in the single crystal furnace 40 and the bottom heater 3 arranged at the bottom of the quartz crucible 41 jointly provide heat for the quartz crucible 41;
[0100] Step S1002: when the growth of single crystal silicon enters the first stage of the equal diameter stage, the auxiliary heater 2 and the bottom heater 3 are turned off, and the main heater 1 alone provides heat for the quartz crucible 41;
[0101] Step S1003 : when the growth of single crystal silicon enters the second stage of the equal diameter stage from the first stage, the bottom heater 3 remains closed, and the auxiliary heater 2 is turned on. The main heater 1 and the auxiliary heater 2 jointly provide heat for the quartz crucible 41 .
[0102] The first stage of the equal diameter stage is generally from the time when the single crystal silicon starts to enter the equal diameter stage to the time when the length of the single crystal silicon growth reaches 500 mm.
[0103] The second stage in the equal diameter stage generally starts after the length of the single crystal silicon growth exceeds 500 mm.
[0104] Among them, in the single crystal silicon direct pulling process provided by the above embodiment, the heating power of the main heater 1 and the auxiliary heater 2 is determined according to the monitored diameter of the single crystal silicon and the growth stage of the single crystal silicon. Specifically, in the first stage of the equal diameter stage, the auxiliary heater 2 and the bottom heater 3 are turned off, and the main heater 1 alone supplies heat to the quartz crucible 41. If the diameter of the single crystal silicon is monitored to exceed the diameter required in the equal diameter stage, it means that the molten silicon crystallizes too quickly and it is necessary to increase the heating power of the main heater 1. If the diameter of the single crystal silicon is monitored to be smaller than the diameter required in the equal diameter stage, it means that the molten silicon crystallizes too slowly and it is necessary to reduce the heating power of the main heater 1. In the second stage of the equal diameter stage, if the diameter of the single crystal silicon is monitored to exceed the diameter required in the equal diameter stage, it means that the molten silicon crystallizes too quickly and it is necessary to increase the heating power of the auxiliary heater 2. If the diameter of the single crystal silicon is monitored to be smaller than the diameter required in the equal diameter stage, it means that the molten silicon crystallizes too slowly and it is necessary to reduce the heating power of the auxiliary heater 2 or the main heater 1. Among them, the parameters for specific regulation of the heating power can be determined according to experiments.
[0105] That is, in step 2, the power of the main heater is increased, wherein the power increase trend of the main heater is regulated based on the diameter of the single crystal silicon.
[0106] In step 3, the power of the main heater is gradually reduced, and the power of the auxiliary heater is gradually increased, wherein the power reduction trend of the main heater and the power increase trend of the auxiliary heater are regulated based on the diameter of the single crystal silicon.
[0107] The control equipment of the single crystal furnace can automatically monitor the diameter of the single crystal silicon, and then automatically control the power of the main heater according to the diameter of the single crystal silicon. The whole process can be automatically controlled.
[0108] The single crystal silicon growth process realized by the single crystal silicon direct pulling thermal field mentioned above, before the growing single crystal silicon enters the equal diameter stage, the main heater, the auxiliary heater and the bottom heater jointly heat the quartz crucible so that the crystalline silicon used for growing the single crystal silicon can be completely melted into silicon liquid, that is, in the material stage, due to the large heating area, the time used for material synthesis can be shortened. And through the cooperation of the main heater, the auxiliary heater and the bottom heater, the problem of excessively high local temperature of the outer layer of the quartz crucible in the material synthesis stage is solved, thereby reducing the influence of high temperature on the inner wall of the quartz crucible, thereby improving the life of the quartz crucible.
[0109] Furthermore, in the first stage of the growing single crystal silicon entering the equal diameter stage, the auxiliary heater and the bottom heater are turned off, and the main heater alone supplies heat to the quartz crucible. Reducing the heat supply to the quartz crucible can reduce the amount of oxygen generated by the quartz crucible. In addition, by supplying heat to the quartz crucible alone through the main heater, thermal convection can be generated between the hot silicon melt in the upper part of the quartz crucible and the cold silicon melt in the lower part. The thermal convection can inhibit the flow of oxygen elements to the surface of the silicon melt, so as to further reduce the oxygen content on the surface of the silicon melt and control the oxygen content at the head of the single crystal silicon.
[0110] In addition, when the growth of single crystal silicon enters the second stage of the equal diameter stage from the first stage, the bottom heater remains closed and the auxiliary heater is turned on. The main heater and the auxiliary heater jointly supply heat to the quartz crucible, so that the heated area of the quartz crucible moves downward, avoiding silicon material crystallization accidents caused by the reduction of silicon material and the slowdown of heat convection in the quartz crucible, thereby ensuring the safety of single crystal silicon production.
[0111] Therefore, the single crystal silicon production process provided by the embodiment of the utility model can effectively improve the quality of the grown single crystal silicon.
[0112] The introduction provided in the above steps is only used to help understand the method, structure and core idea of the utility model. For ordinary technicians in this technical field, the utility model can also be improved and modified without departing from the principle of the utility model, and these improvements and modifications also fall within the scope of protection of the claims of the utility model.
Claims
1. A single crystal silicon direct pull thermal field, characterized in that: include: Quartz crucible (41), a main heater (1) arranged around the side of the quartz crucible (41), a secondary heater (2) disposed around the side of the quartz crucible (41) and located below the primary heater (1), and A bottom heater (3) located below the quartz crucible (41); the auxiliary heater (2) comprises: a heating structure (21) and two accommodating cavities (22) arranged opposite to each other, wherein: The two accommodating cavities (22) and the heating structure (21) form a ring structure; The accommodating cavity (22) is used to accommodate the heating electrode of the main heater (1); The main heater (1), the sub-heater (2) and the bottom heater (3) are each independently controlled.
2. The single crystal silicon CZ thermal field according to claim 1, characterized in that: The main heater (1) is arranged corresponding to the upper half of the quartz crucible (41).
3. The single crystal silicon CZ thermal field according to claim 1, characterized in that: The sub-heater (2) is located in the lower half of the quartz crucible (41), and the distance from the lower edge of the sub-heater (2) to the bottom of the quartz crucible (41) is one third of the height of the quartz crucible (41).
4. The single crystal silicon CZ thermal field according to claim 1, characterized in that: The heating structure (21) comprises: two heating bodies (211), two connecting components (212) and two heating electrodes (213), wherein: The cross-sections of the two heating bodies (211) are arc-shaped structures; Two ends of the two heating bodies (211) are fixedly connected to the two connecting components (212) respectively; Each of the connecting components (212) and the ends of the two heating bodies (211) connected thereto enclose the accommodating cavity (22); The two heating electrodes (213) are fixedly connected to the two heating bodies (211) respectively.
5. The single crystal silicon CZ thermal field according to claim 4, characterized in that: The connection assembly (212) comprises: an additional connection strip (2121) of a frame-shaped structure and two additional connection plates (2122), wherein: The two additional connecting plates (2122) respectively fix the two ends of the additional connecting strip (2121) to the ends of the two heating bodies (211); The frame-shaped structure and the ends of the two heating bodies (211) enclose the accommodating cavity (22).
6. The single crystal silicon CZ thermal field according to claim 4, characterized in that: The lower surface of the heating electrode of the main heater (1) and the lower surface of the heating electrode (213) included in the auxiliary heater (2) are located in the same plane.
7. The single crystal silicon CZ thermal field according to claim 4, characterized in that: The heating body (211) is a serpentine structure; and / or, The heating body of the main heater (1) is a serpentine structure.
8. The single crystal silicon CZ thermal field according to claim 2, characterized in that: The lower edge of the main heater (1) is located at one half of the quartz crucible (41).