A method for removing gallium metal from a single crystal crucible bottom charge

Abstract

The application discloses a method for removing gallium metal from a single crystal crucible bottom material, comprising the following steps: placing the crucible bottom material in a hot liquid and continuously heating, so that the gallium metal attached to the silicon material of the crucible bottom is converted into a molten state; and applying an external force to the hot liquid or / and the crucible bottom material, so that the gallium metal in the molten state is separated from the silicon material of the crucible bottom. Through the above treatment, the gallium metal in the silicon material of the crucible bottom can be separated out, so that when the silicon material of the crucible bottom is recycled and reused, the problems of subsequent crystal growth difficulty and crystal rod quality decline caused by the gallium metal in the recycled material can be avoided; the separated gallium metal can be recycled and reused, so that the single crystal production cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic product manufacturing technology, and in particular to a method for removing gallium metal from the bottom material of a single crystal crucible. Background Technology

[0002] Because of its green and environmentally friendly nature, photovoltaic power generation is being used more and more widely, but the manufacturing cost of the components used in photovoltaic power generation remains high. Among the components used in photovoltaic power generation, silicon wafers are one of the most critical components. Silicon wafers are obtained by slicing silicon rods; and silicon rods are currently generally pulled out using the Czochralski method.

[0003] Czochralski (CZ) single crystal pulling refers to the process of placing silicon raw material in a crucible and pulling it into a single crystal through a series of steps, including melting, temperature stabilization, crystal pulling, shoulder expansion, diameter equalization, and finishing. After a normal furnace shutdown, there will generally be residual crucible bottom material in the crucible. With the expansion of the hot zone of single crystal furnaces and the increase in the amount of raw material fed into a single furnace, the proportion of raw material cost in the total cost of CZ single crystal pulling has been increasing year by year. In order to reduce costs and increase efficiency, some manufacturers recycle the crucible bottom material, that is, process the crucible bottom material and recycle it to be used in the next batch of silicon raw material. However, some crucible bottom material has gallium attached to it, and there is currently no good way to remove gallium from the crucible bottom material. When this crucible bottom silicon material is reused, it will lead to difficulties in subsequent crystal formation and a decrease in the quality of the crystal rod. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for removing gallium metal from the bottom material of a single crystal crucible. This method can separate the gallium metal attached to the silicon material at the bottom of the crucible, thereby reducing the impact of gallium metal on the subsequent recycling of the silicon material at the bottom of the crucible. Moreover, the separated gallium metal can be recycled and reused.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for removing gallium metal from the bottom of a single-crystal crucible includes the following steps:

[0007] The bottom material of the crucible is placed in a hot liquid and continuously heated, so that the metallic gallium attached to the silicon material at the bottom of the crucible is transformed into a molten state;

[0008] An external force is applied to the hot liquid and / or the bottom material of the crucible, causing the molten gallium metal to separate from the silicon material at the bottom of the crucible.

[0009] Preferably, the hot liquid comprises hot alkaline solution and hot pure water, and the operation steps are as follows:

[0010] First, perform alkaline boiling: Place the bottom material of the crucible into the hot alkaline solution and continue heating the alkaline solution until the metallic gallium on the silicon material at the bottom of the crucible turns into a molten state.

[0011] Then perform pure water heating and cleaning: place the bottom material of the crucible in hot pure water and continue to heat the pure water, apply external force to the pure water and / or the bottom material of the crucible, so that the metallic gallium separates from the silicon material at the bottom of the crucible.

[0012] Preferably, in the above-mentioned alkali boiling step, the bottom material of the crucible is placed in a hot alkali solution at a first set temperature, and the alkali solution is heated further; after the temperature of the alkali solution rises to a second set temperature, the bottom material of the crucible is boiled for a first set time, and during the first set time, the temperature of the hot alkali solution is maintained between the second set temperature and a third set temperature, wherein the third set temperature is higher than the second set temperature.

[0013] Preferably, the first set temperature is set to 60-70 degrees Celsius; the second set temperature is set to 75-85 degrees Celsius; and the third set temperature is set to 80-92 degrees Celsius.

[0014] Preferably, the first set time is set to 30-40 minutes.

[0015] Preferably, the bottom material of the crucible is placed in hot pure water at the fourth set temperature, and then the pure water is heated to the second set time, while the temperature of the pure water is maintained at the fifth set temperature.

[0016] Preferably, the fourth set temperature is 65-70 degrees Celsius, and the fifth set temperature is 75-85 degrees Celsius.

[0017] Preferably, the second set time is 20-30 minutes.

[0018] Preferably, during the continued heating of the pure water, stirring generates centrifugal force in the pure water, causing the metallic gallium to transform into liquid droplets and separate from the silicon material 1 at the bottom of the crucible.

[0019] Preferably, the following steps are performed sequentially after the alkaline boiling and before the pure water heating and rinsing:

[0020] Acid cleaning at room temperature;

[0021] Clean with pure water at room temperature.

[0022] Preferably, the acid solution is HF with a concentration of 1-3%; the bottom material of the crucible after the alkali boiling step is immersed in the HF for 5-10 minutes for cleaning.

[0023] Because the present invention adopts the above-mentioned technical solution, it has the following beneficial effects:

[0024] 1. It can completely separate the silicon material at the bottom of the crucible from the metallic gallium, so that when the silicon material at the bottom of the crucible is recycled and reused, it can avoid the problems of subsequent crystal formation difficulties and crystal rod quality degradation caused by the gallium metal in the recycled material; moreover, the separated gallium metal can be recycled and reused, thereby further reducing the cost of single crystal production and making it more environmentally friendly.

[0025] 2. In the process of this invention, a better balance is achieved between temperature, time and safety, so that not only can the separation and recycling of silicon material and metallic gallium at the bottom of the crucible be completed efficiently, but also the problem of alkaline solution penetrating deeply into the silicon material at the bottom of the crucible is avoided.

[0026] 3. Because the present invention initially selects alkaline boiling, and after alkaline boiling, acid cleaning at room temperature and pure water cleaning at room temperature are carried out, organic impurities and other metal impurities on the surface of silicon material at the bottom of the crucible can be removed, thereby greatly improving the quality of silicon material at the bottom of the crucible, making the silicon material at the bottom of the crucible fully meet the requirements for recycling and reuse, and reducing the raw material cost of Czochralski single crystal. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the crucible bottom material with gallium metal coated on its surface.

[0028] Figure 2 This is a schematic diagram showing how gallium metal becomes molten after being boiled in alkali.

[0029] Figure 3 These are the separated gallium particles. Detailed Implementation

[0030] The present invention will now be described in detail with reference to specific embodiments and the accompanying drawings. In the embodiments of this application, the terms "first," "second," "third," "fourth," and "fifth" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features.

[0031] The reason gallium is present in the crucible bottom material is to enable certain silicon wafers to possess specific functions. During the single-crystal pulling process, special metal elements, such as gallium, are doped as needed. Therefore, the remaining bottom material in the crucible, besides silicon material 1, also contains gallium 2 attached to the surface of silicon material 1. Furthermore, the gallium is continuously and extensively adhered to the bottom silicon material (e.g., ...). Figure 1 (As shown).

[0032] However, current recycling methods for bottom-fill material generally involve acid etching to remove metallic impurities from the silicon material. However, this method is not very effective at removing gallium impurities adhering to the surface of the bottom-fill silicon material. As a result, a significant amount of gallium remains on the bottom-fill silicon material after this recycling process. When this bottom-fill silicon material is reused, it can lead to difficulties in subsequent crystal formation and a decline in crystal rod quality. Furthermore, the fact that the gallium is not isolated is also a waste of resources.

[0033] To address the above problems, this invention discloses a method for removing gallium metal from the bottom material of a single-crystal crucible, comprising the following steps:

[0034] The bottom material of the crucible is placed in a hot liquid and continuously heated, so that the metallic gallium 2 attached to the silicon material 1 at the bottom of the crucible is transformed into a molten state;

[0035] An external force is applied to the hot liquid and / or the bottom material of the crucible, causing the molten gallium 2 to separate from the silicon material 1 at the bottom of the crucible.

[0036] In this embodiment, the hot liquid includes hot alkaline solution and hot pure water, and the operation method is as follows:

[0037] First, perform alkaline boiling: Place the bottom material of the crucible into the hot alkaline solution and continue heating the alkaline solution until the metallic gallium 2 attached to the silicon material 1 at the bottom of the crucible turns into a molten state.

[0038] Then perform pure water heating and cleaning: place the bottom material of the crucible in hot pure water and continue to heat the pure water, apply external force to the pure water and / or the bottom material of the crucible, so that the gallium metal 2 separates from the silicon material 1 at the bottom of the crucible.

[0039] In the above step "alkali boiling", the alkali solution is sodium hydroxide with a concentration of 20%-30%. The bottom material of the crucible is placed in the hot alkali solution at a first set temperature and the alkali solution is heated. After the temperature of the alkali solution rises to a second set temperature, the bottom material of the crucible is boiled for a first set time. During the first set time, the temperature of the hot alkali solution is maintained between the second set temperature and a third set temperature, where the third set temperature is higher than the second set temperature.

[0040] Preferably, the first set temperature is set to 60-70 degrees Celsius. More preferably, it can be 60, 62, 66, 68, or 70 degrees Celsius.

[0041] The second set temperature is set to 75-85 degrees Celsius. Preferably, it can be 75, 76, 78, 80, 82, 84 or 85 degrees Celsius.

[0042] The third set temperature is set to 80-92 degrees Celsius. Preferably, it can be 80, 82, 85, 88, 90, 91 or 92 degrees Celsius.

[0043] The first set time is set to 30-40 minutes. Preferably, it can be 30, 32, 34, 35, 36, 38 or 40 minutes.

[0044] Specifically, the bottom material of the crucible is placed in a hot alkaline solution at the first set temperature, and the alkaline solution is heated. After the temperature of the hot alkaline solution rises to the second set temperature, heating continues. When the temperature of the hot alkaline solution rises to the third set temperature, heating is stopped. After heating is stopped, the alkaline solution will naturally cool down slowly. When the temperature of the hot alkaline solution drops to the second set temperature, it is heated again until the temperature of the hot alkaline solution rises to the third set temperature, and then heating is stopped. In this way, the cycle is repeated for 30-40 minutes from the first time the temperature of the alkaline solution rises to the second set temperature, so that the temperature of the hot alkaline solution is maintained between the second set temperature and the third set temperature during these 30-40 minutes.

[0045] After the above treatment, the gallium 2 that was extensively adhered to the surface of the silicon material 1 at the bottom of the crucible changed from a solid state to a molten state (e.g., Figure 2 As shown, although the molten gallium 2 still adheres to the silicon material 1 at the bottom of the crucible due to its stickiness, the bonding force between it and the bottom material is greatly reduced, which is equivalent to achieving the initial separation of the gallium 2 from the silicon material 1 at the bottom of the crucible.

[0046] Moreover, the reason for choosing alkaline boiling instead of acid washing, pure water washing or other chemical washing is that alkaline solution can also remove organic matter such as silica mud, oil stains and other dirt from the surface of the crucible bottom material. Thus, after the alkaline boiling step, the crucible bottom material can also achieve the goal of looking clean to the naked eye.

[0047] In this invention, controlling the maximum temperature of the hot alkali solution to not exceed 95 degrees Celsius can prevent the dangerous splashing of the hot alkali solution. Because alkali solution is highly corrosive, splashing could damage nearby people and property. Therefore, during the alkali boiling step, after placing the crucible material into the hot alkali solution, stirring is prohibited, as is ultrasonic vibration. No external force should be applied to the hot alkali solution or the crucible material within it, to avoid safety issues caused by splashing. Furthermore, during alkali boiling, a three-tiered temperature gradient of first, second, and third set temperatures is used, instead of a two-tiered gradient of "second set temperature + third set temperature" (i.e., directly heating the alkali solution to the second set temperature before placing the crucible material). The temperature of the alkali solution is kept between the second and third set temperatures because the second set temperature of 75-85 degrees Celsius is relatively high. When the bottom material of the crucible is placed into the alkali solution at the second set temperature, it is very likely that the alkali solution will splash out and cause safety problems. Therefore, the three-layer temperature gradient setting is safer. In the first set time, the hot alkali solution is kept between the second and third set temperatures, which are relatively high but do not exceed 95 degrees Celsius. That is, the minimum temperature is not lower than 75 degrees Celsius and the maximum temperature is not higher than 92 degrees Celsius. This allows the gallium metal 2 that is attached to the surface of the silicon material 1 at the bottom of the crucible to transform from a solid state to a molten state more quickly. Therefore, the first set time for this temperature only needs to be 30-40 minutes. Thus, the present invention can achieve a better balance between temperature, time and safety, so that after the alkaline boiling step, in addition to the above-mentioned changes, the alkaline solution will only adhere to the surface of the silicon material at the bottom of the crucible and will not penetrate deeply into it; moreover, the first set time only needs to be a relatively short 30-40 minutes, which can also shorten the time of the entire process and improve the finishing efficiency.

[0048] The time the silicon material 1 at the bottom of the crucible spends in the alkaline solution significantly impacts its performance after recycling. If the time is too long, the solution will not only corrode some of the silicon material 1, but also allow a large amount of alkali to penetrate deeply into it. Currently, there is no feasible method to remove this deeply penetrated alkali. However, even if gallium 2 is removed, the remaining silicon material 1 cannot be recycled. If recycled, the alkali in the silicon material 1 (and its content is not low) will severely affect the quality of the single crystal, potentially preventing successful crystal pulling. More seriously, the alkali in the silicon material 1 can react with the crucible, causing silicon leakage and resulting in significant damage to the thermal field and the single crystal furnace.

[0049] Furthermore, this invention sets the first set temperature to 60-70 degrees Celsius and selects to add the bottom material of the crucible after the alkaline solution has been heated to the first set temperature, rather than placing the bottom material in the alkaline solution at room temperature or other temperatures lower than the first set temperature and then heating it together to the second or third set temperature. This is also to reduce the time the bottom material of the crucible is in the alkaline solution. If the latter were followed, the time the bottom silicon material 1 of the crucible would be in the alkaline solution to make the gallium 2 turn into a molten state would inevitably be greatly prolonged, resulting in a large amount of alkaline solution deeply penetrating into the bottom silicon material 1 of the crucible. Moreover, this application operates in this way, which can further reduce the overall processing time and thus improve the processing efficiency, because the alkaline solution can be preheated to the first set temperature, and the bottom material of the crucible can be placed into the hot alkaline solution that has reached the required temperature immediately after it is taken out, instead of having to wait for the alkaline solution at room temperature to be heated temporarily, or placing the bottom material of the crucible in the alkaline solution at room temperature for heating together. The first set temperature is also not suitable to be higher, because there are concerns about the safety problem of alkaline solution splashing out when the bottom material of the crucible is placed in.

[0050] Furthermore, this invention does not involve directly boiling the bottom material in the alkaline solution until the gallium 2 becomes a liquid metal droplet and completely separates from the bottom material. Instead, it achieves complete separation of the gallium 2 through multiple steps. This is not only because stirring is prohibited, but also because it reduces the time the bottom material spends in the alkaline solution, thus preventing too much alkaline solution from seeping into the bottom silicon material 1 and avoiding the aforementioned problems caused by excessive alkaline solution seeping into the bottom silicon material 1.

[0051] In the pure water heating and cleaning process, the bottom material of the crucible is placed in hot pure water at a fourth set temperature, and then the pure water is heated for a second set time, while the temperature of the pure water is maintained at a fifth set temperature.

[0052] The fourth set temperature is 65-70 degrees Celsius, preferably 65, 66, 68, 69 or 70 degrees Celsius.

[0053] The fifth setting temperature is 75-85 degrees Celsius, preferably 75, 76, 78, 80, 82, 83 or 85 degrees Celsius. The temperature of 75-85 degrees Celsius is higher than the melting point of gallium 2, which facilitates the separation of gallium 2 from the silicon material 1 at the bottom of the crucible.

[0054] The second set time is 20-30 minutes, preferably 20, 22, 25, 26, 28, 29 or 30 minutes.

[0055] Specifically, after placing the crucible bottom material into hot pure water at a temperature of 65-70 degrees Celsius, the pure water is heated until it reaches a temperature of 85 degrees Celsius or lower but higher than 75 degrees Celsius. Heating is then stopped, and the pure water temperature is allowed to drop to 75 degrees Celsius before heating resumes, repeating this cycle. The second set time of 20-30 minutes refers to the time from the start of heating the pure water after placing the crucible bottom material into the hot pure water at the fourth set temperature until completion. Therefore, the overall time spent in the "pure water heating and cleaning" step is shorter than that of the alkaline boiling step, and the maximum temperature of the fifth set temperature is also lower than the maximum temperature of the third set temperature. This is because, initially, solid gallium metal 2 is rigidly attached to the silicon material 1 at the bottom of the crucible, and the two are bonded very firmly. Therefore, to transform gallium metal 2 into a molten state, the crucible bottom material needs to be placed in a hotter alkaline solution for a longer period. In the "pure water heating and cleaning" step, gallium metal 2 is already in a molten state, and external force is applied; therefore, the required liquid temperature can be slightly lower, and the duration can be shorter. These settings are based on the state of gallium 2.

[0056] The aforementioned application of external force to the hot liquid and / or the bottom material of the crucible is because molten gallium 2 is viscous. If simply immersed in hot pure water, molten gallium 2 would only continue to adhere to the silicon material 1 at the bottom of the crucible and would not separate from it. Therefore, in the alkaline boiling step, even though the temperature of the hot alkaline solution is much higher than the melting point of gallium 2, and gallium 2 turns into a molten state, the molten gallium 2 will only adhere to the silicon material 1 at the bottom of the crucible and will not detach.

[0057] In one embodiment, stirring can be performed during the continued heating of pure water to generate centrifugal force in the pure water, causing the gallium 2 to transform into metal droplets and separate from the silicon material 1 at the bottom of the crucible. Specifically, during stirring, centrifugal force is generated in the pure water. Under the action of centrifugal force, the originally molten gallium 2 will form droplets and be thrown off the silicon material 1 at the bottom of the crucible into the pure water, thereby completing the complete separation of the gallium 2 and the silicon material 1.

[0058] During stirring, a non-metallic stirring element should be used to avoid metal ions from the metal stirring element adhering to the surface of the bottom material of the crucible and becoming impurities, which would affect the quality of subsequent recovery of silicon material 1 from the bottom of the crucible. In this embodiment, a PTFE rod is preferably used for stirring. Stirring can be done continuously during heating or every 5-10 minutes.

[0059] Preferably, the bottom material of the crucible can be cleaned by simultaneously subjecting it to ultrasonic vibration, which makes it easier and faster for the droplets of metallic gallium 2 to detach from the silicon material 1 at the bottom of the crucible and fall into pure water. Specifically, pure water is added to the ultrasonic vibration tank and heated, and the bottom material of the crucible is placed inside the ultrasonic vibration tank. Ultrasonic vibration is also a type of external force.

[0060] After the above treatment, the gallium metal 2 falls into the pure water in the form of droplets, while the bottom material of the crucible still maintains its initial solid shape. This is because neither the highest temperature of the alkali solution in the alkali boiling step nor the highest temperature of the pure water in the pure water heating and cleaning step reaches the melting point of silicon, so the silicon material 1 at the bottom of the crucible remains in a solid shape.

[0061] In another embodiment, the water tank for holding hot pure water can be configured with two layers, separated by a mesh partition. The bottom material of the vessel is placed in the upper layer; the lower layer is equipped with an on / off adsorption device. By activating the adsorption device, gallium metal is adsorbed, causing it to detach from the silicon material at the bottom of the vessel. Preferably, multiple adsorption devices can be spaced apart for better adsorption effect. The adsorption device and its connection to the water tank can be any known and feasible structure, as long as it achieves the above function and does not contaminate the bottom material of the vessel and the gallium metal. Since this is not an innovation of the present invention, it will not be elaborated here. The adsorption force is also a type of external force.

[0062] In another embodiment, multiple air pipes can be arranged in different directions on the upper and / or lower layers, with the outlets of all air pipes facing the bottom material of the crucible. The inlet of the air pipe extends outside the water tank and connects to the air supply device. A sealing structure is provided where the air pipe passes through the wall of the water tank to prevent water leakage. When the air supply device is turned on, it supplies air to the air pipes. The gas exits from the outlet of the air pipe and blows the bottom material of the crucible, thereby blowing the metallic gallium away from the silicon material at the bottom of the crucible. Similarly, the sealing structure and the air supply device can be any known and feasible structure, as long as they can achieve the above functions and do not contaminate the bottom material of the crucible and the metallic gallium. Since this is not an innovation of the present invention, it will not be described in detail here. The blowing force of the gas is also a type of external force.

[0063] Furthermore, vibration or stirring can be combined with the above-mentioned adsorption or blowing.

[0064] In this embodiment, preferably, the following steps are performed sequentially after the alkaline boiling and before the pure water heating and washing;

[0065] Acid cleaning at room temperature;

[0066] Clean with pure water at room temperature.

[0067] The acid solution is HF with a concentration of 1-3%. The bottom material of the pot after boiling is immersed in the HF for soaking and cleaning for 5-10 minutes. Preferably, the soaking and cleaning time can be 6, 8 or 9 minutes.

[0068] The acid solution not only neutralizes the alkaline solution on the surface of the bottom material, but also reacts with other metallic impurities on the surface of silicon material 1, thereby removing these impurities. Therefore, this step can further improve the quality of the recovered bottom silicon material 1.

[0069] In the pure water room temperature cleaning step, the cleaning can be carried out by rinsing with pure water at room temperature or by direct immersion combined with overflow, and the cleaning time is 2-3 minutes. This pure water room temperature cleaning can not only more effectively remove the acid and alkali solutions adhering to the surface of the crucible bottom material, avoiding the acid and alkali solutions being carried into the next step (i.e., the pure water heating cleaning step), but also more effectively wash away other metallic impurities that have reacted with the acid solution adhering to the crucible bottom material. As a result, the treated crucible bottom material, except for the gallium 2 metal still adhering to it, meets the requirements for recycling and reuse in other aspects.

[0070] In the subsequent acid cleaning at room temperature and pure water cleaning at room temperature, since both are carried out at room temperature and for a short time, the gallium 2 metal in the bottom of the crucible after the alkali boiling treatment is still in a molten state and will not return to the initial solidified state.

[0071] Furthermore, the present invention selects to place the crucible bottom material, which has been cleaned with pure water at room temperature, into hot pure water at a fourth set temperature for further heating, instead of placing the crucible bottom material into pure water at room temperature and heating them together. This operation allows the pure water to be heated to the fourth set temperature simultaneously during the preceding steps, thereby reducing the overall processing time and improving the overall processing efficiency.

[0072] After separating the metallic gallium from the silicon material at the bottom of the pot, the separated liquid metallic gallium 2 and the silicon material at the bottom of the pot 1 are collected separately.

[0073] A fine-mesh mesh can be used to collect droplet-shaped gallium 2. The fine-mesh mesh should be made of plastic or rubber to avoid reacting with the gallium 2 and affecting its recycling.

[0074] The collected liquid gallium 2 is placed in a refrigerator. At low temperatures, the liquid gallium 2 will solidify again, allowing it to be reused later. The container used to hold the gallium 2 particles must be made of plastic or rubber; glass or metal containers cannot be used to avoid corrosion caused by the reaction.

[0075] After the liquid gallium 2 turns back into a solid state, it can be kept in a refrigerator or stored in a different environment, but the temperature should be 5-10 degrees Celsius, because only under this temperature can the solid state of gallium 2 be preserved.

[0076] The silicon material 1 obtained after processing by the method of this invention is collected, dried, and packaged for recycling. The heating and packaging methods can be any known and feasible methods, and since they are not innovative points of this invention, they will not be described in detail here.

[0077] In this embodiment, preferably, before performing the above-mentioned alkaline boiling step, the bottom material of the crucible can be crushed into blocks, such as blocks with a particle size of 50mm-60mm, and then the crushed bottom material of the crucible can be processed in the above-mentioned steps. Such small-particle-size blocks of bottom material of the crucible will make it easier to process and separate the metallic gallium 2 and the bottom silicon material 1 of the crucible.

[0078] In summary, the method of this invention is proposed based on the characteristics of each substance in the crucible bottom material and in combination with the characteristics of acid, alkali, and pure water. Through the processing method of this invention, not only can organic impurities and other metallic impurities present on the surface of the crucible bottom silicon material be removed, but the crucible bottom silicon material can also be completely separated from metallic gallium, thereby greatly improving the quality of the crucible bottom silicon material and making it fully compliant with the requirements for recycling and reuse, thus reducing the raw material cost of Czochralski single crystal production. Furthermore, when the crucible bottom silicon material is recycled and reused, the problems of subsequent crystal formation difficulties and reduced crystal rod quality caused by gallium metal in the recycled material can be avoided. The separated gallium metal can be recycled and reused, further reducing the cost of single crystal production and making it more environmentally friendly. Moreover, the overall processing time is short and the efficiency is high.

[0079] The specific embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for removing gallium metal from the bottom material of a single-crystal crucible, characterized in that: Includes the following steps: The bottom material of the crucible is placed in a hot liquid and continuously heated, so that the metallic gallium attached to the silicon material at the bottom of the crucible is transformed into a molten state; An external force is applied to the hot liquid and / or the bottom material of the crucible, causing the molten gallium metal to separate from the silicon material at the bottom of the crucible.

2. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 1, characterized in that: The hot liquid includes hot alkaline solution and hot pure water. The operation steps are as follows: First, perform alkaline boiling: Place the bottom material of the crucible into the hot alkaline solution and continue heating the alkaline solution until the metallic gallium on the silicon material at the bottom of the crucible turns into a molten state. Then perform pure water heating and cleaning: place the bottom material of the crucible in hot pure water and continue to heat the pure water, apply external force to the pure water and / or the bottom material of the crucible, so that the metallic gallium separates from the silicon material at the bottom of the crucible.

3. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 2, characterized in that: In the above-mentioned alkali boiling step, the bottom material of the crucible is placed in a hot alkali solution at a first set temperature, and the alkali solution is heated. After the temperature of the alkali solution rises to a second set temperature, the bottom material of the crucible is boiled for a first set time. During the first set time, the temperature of the hot alkali solution is maintained between the second set temperature and the third set temperature, wherein the third set temperature is higher than the second set temperature.

4. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 3, characterized in that: The first set temperature is set to 60-70 degrees Celsius; the second set temperature is set to 75-85 degrees Celsius; and the third set temperature is set to 80-92 degrees Celsius.

5. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 4, characterized in that: The first set time is set to 30-40 minutes.

6. The method for removing gallium metal from the bottom material of a single-crystal crucible according to any one of claims 2 to 5, characterized in that: Place the bottom material of the crucible into hot pure water at the fourth set temperature, then continue heating the pure water for the second set time, and keep the temperature of the pure water at the fifth set temperature.

7. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 6, characterized in that: The fourth set temperature is 65-70 degrees Celsius, and the fifth set temperature is 75-85 degrees Celsius.

8. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 7, characterized in that: The second set time is 20-30 minutes.

9. The method for removing gallium metal from the bottom material of a single-crystal crucible according to any one of claims 2 to 5 and 7 to 8, characterized in that: During the continued heating of pure water, stirring is performed to generate centrifugal force in the pure water, causing the metallic gallium to transform into metallic droplets and separate from the silicon material 1 at the bottom of the crucible.

10. The method for removing gallium metal from the bottom material of a single-crystal crucible according to any one of claims 2 to 5 and 7 to 8, characterized in that: After the alkaline boiling and before the pure water heating and rinsing, the following steps shall be performed in sequence: Acid cleaning at room temperature; Clean with pure water at room temperature.

11. The method for removing gallium metal from the bottom material of a single-crystal crucible according to claim 10, characterized in that: The acid solution is HF with a concentration of 1-3%; the bottom material of the crucible after the alkali boiling step is immersed in the HF for 5-10 minutes for cleaning.

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