Double-layer crucible

Abstract

The utility model relates to the technical field of monocrystalline silicon rod preparation, in particular to a double-layer crucible. The double-layer crucible comprises an outer crucible and an inner crucible which are consistent in opening direction, the inner crucible is arranged in the outer crucible in a sleeving manner, a feeding space is formed between the inner wall of the outer crucible and the outer wall of the inner crucible, and a through hole communicated with the outer crucible is formed in the bottom or the side part of the inner crucible; the outer wall surface of the inner crucible and the inner wall surface of the outer crucible are each coated with at least one anti-corrosion isolation coating in a laid mode. According to the double-layer crucible, the technical problems that in an existing continuous crystal pulling technology, the corrosivity of silicon liquid to the crucible is large, and the oxygen content of a CCZ silicon rod is high are solved while the continuous crystal pulling efficiency is not affected.

Description

Technical Field

[0001] This application relates to the technical field of single-crystal silicon rod preparation, and particularly to a double-layer crucible. Background Art

[0002] Conventional single-crystal preparation techniques generally adopt the recharged Czochralski technique (hereinafter referred to as RCZ). As Figure 1 shown, after a silicon rod is completely drawn by this RCZ technique, charging is required to draw the next silicon rod, resulting in low efficiency. Currently, a new single-crystal preparation technique has emerged, the continuous Czochralski technique (hereinafter referred to as CCZ), as Figure 2 shown. The biggest difference between this CCZ technique and the aforementioned RCZ technique is that it can simultaneously achieve single-crystal drawing and charging and melting, that is, charging can be carried out while single-crystal drawing, without interfering with each other, and the liquid silicon level can be basically kept unchanged, enabling continuous feeding and continuous crystal drawing.

[0003] Based on this, the CCZ technique has the following advantages compared with the RCZ technique: First, the production efficiency is significantly improved. For example, under the condition that the CCZ technique can complete the drawing of 8-10 single-crystal silicon rods within the allowable life cycle of the crucible, the RCZ technique can only draw about 7 rods; Second, the production cost is reduced. The CCZ technique can effectively reduce the crystal drawing time, crucible cost and energy consumption. The single-furnace production cost of the CCZ technique is at least 10% lower than that of the RCZ technique; Third, it is applicable to N-type single crystals. The axial resistivity distribution of the single-crystal silicon products drawn by the CCZ technique is uniform, and its fluctuation is controlled within 15%.

[0004] However, since the CCZ technique uses a double-crucible mode for crystal drawing, the contact area between the liquid silicon and the crucible is greatly increased. At the same time, the crucible is generally made of quartz material, resulting in a greatly increased degree of corrosion of the quartz crucible by the liquid silicon. This will not only greatly reduce the service life of the quartz crucible, but also increase the oxygen content of the silicon rod (and then form a CCZ silicon wafer) prepared by the CCZ technique, restricting the popularization of the CCZ technique. For example: with the existing process level, the oxygen content of most RCZ silicon rods prepared by the RCZ technique is below 12 ppm, and the maximum oxygen content of CCZ silicon wafers prepared by the CCZ technique is 14-15 ppm. Utility Model Content

[0005] The purpose of this application is to provide a double-layer crucible to solve the technical problems of large corrosion of the crucible by liquid silicon and high oxygen content of CCZ silicon rods in the existing continuous crystal drawing technique without affecting the continuous crystal drawing efficiency.

[0006] A double-layer crucible provided by this application includes:

[0007] An outer crucible and an inner crucible with the same opening direction, the inner crucible is sleeved inside the outer crucible, a feeding space is formed between the inner wall of the outer crucible and the outer wall of the inner crucible, and a through hole communicating with the outer crucible is provided at the bottom or side of the inner crucible;

[0008] At least one layer of anti-corrosion isolation coating is respectively coated and laid on the outer wall surface of the inner crucible and the inner wall surface of the outer crucible.

[0009] Further, the anti-corrosion isolation coating is at least one layer of boron nitride layer, zirconia layer, silicon nitride layer, alumina layer, silicon carbide layer.

[0010] Further, there are multiple layers of the anti-corrosion isolation coating, and the multiple layers of the anti-corrosion isolation coating are coated layer by layer.

[0011] Furthermore, the total thickness of one or more layers of the anti-corrosion isolation coating is 0.5 mm to 2 mm.

[0012] Further, both the inner crucible and the outer crucible adopt a cylindrical structure, and the central axis of the inner crucible coincides with the central axis of the outer crucible.

[0013] Furthermore, the diameter size of the inner crucible is between 659 mm and 920 mm;

[0014] The diameter size of the outer crucible is between 810 mm and 1070 mm;

[0015] The diameter difference between the inner crucible and the outer crucible is greater than or equal to 150 mm.

[0016] Further, the anti-corrosion isolation coating is formed by coating a slurry, and the slurry includes coating material powder, high-temperature binder and water; the coating material powder includes at least one of boron nitride powder, zirconia powder, silicon nitride powder, alumina powder, silicon carbide powder.

[0017] Further, the particle size of the coating material powder is between 0.1 and 5 μm.

[0018] Further, the ratio of the coating material powder, the high-temperature binder and the water in the slurry is: coating material powder: high-temperature binder: water = 1: 0.1 - 0.5: 0.5 - 2.

[0019] Furthermore, the slurry is heated and cured to form the anti-corrosion isolation coating;

[0020] The temperature of the heating is 30 to 150 °C.

[0021] Compared with the prior art, the double-layer crucible provided by the present application includes an outer crucible and an inner crucible with the same opening direction, and the inner crucible is sleeved inside the outer crucible. Crystal pulling is carried out inside the inner crucible, and a feeding space is formed between the inner wall of the outer crucible and the outer wall of the inner crucible to feed silicon liquid into the feeding space. A through hole communicating with the outer crucible is provided at the bottom or side of the inner crucible, so that the silicon liquid in the feeding space can be supplemented into the inner crucible through the through hole, so as to realize feeding while crystal pulling, and the two do not interfere with each other, realizing continuous feeding and continuous crystal pulling. Moreover, at least one anti-corrosion isolation coating is respectively coated and laid on the outer wall surface of the inner crucible and the inner wall surface of the outer crucible to prevent and isolate the direct contact between the silicon liquid and the inner crucible and the outer crucible, avoid the corrosion of the crucible by the silicon liquid, and effectively extend the service life of the quartz crucible. At the same time, since the corrosion of the crucible by the silicon liquid is avoided, the oxygen content of the silicon rod prepared by the CCZ technology is effectively reduced, which is more conducive to the popularization of the CCZ technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 is a schematic diagram of the principle of pulling single crystal by the RCZ technology in the prior art;

[0024] Figure 2 is a schematic diagram of the principle of pulling single crystal by the CCZ technology in the prior art;

[0025] Figure 3 is the cross-sectional view of the double-layer crucible provided by the embodiment of the present application Figure 1 ;

[0026] Figure 4 is the cross-sectional view of the double-layer crucible provided by the embodiment of the present application Figure 2 .

[0027] REFERENCE SIGNS:

[0028] 100 - double-layer crucible;

[0029] 10 - outer crucible;

[0030] 20 - inner crucible;

[0031] 21 - through hole;

[0032] 30 - feeding space;

[0033] 40 - anti-corrosion isolation coating;

[0034] 200 - silicon liquid. Specific embodiments

[0035] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are some, but not all, of the embodiments of the present application. Generally, the components of the embodiments of the present application described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0036] The following will describe in detail some embodiments of the present application with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0037] As Figures 2 to 4 shown, the embodiments of the present application provide a double - layer crucible 100, which is used for the continuous crystal pulling technology (i.e., the CCZ technology). The basic principle of the continuous crystal pulling technology is as Figure 2 shown. It can simultaneously achieve single - crystal pulling and feeding and melting, that is, it can simultaneously achieve continuous single - crystal pulling and continuous feeding, feeding while pulling a single crystal, without interfering with each other, and has a high single - crystal pulling efficiency.

[0038] As Figure 3 and Figure 4 shown, the double - layer crucible 100 provided by the embodiments of the present application may include an outer crucible 10 and an inner crucible 20 with the same opening direction. Specifically, the opening directions of the outer crucible 10 and the inner crucible 20 can both face upward. The inner crucible 20 is sleeved inside the outer crucible 10, and a feeding space 30 is formed between the inner wall of the outer crucible 10 and the outer wall of the inner crucible 20. A through - hole 21 communicating with the outer crucible 10 is provided at the bottom or side of the inner crucible 20; at least one anti - corrosion isolation coating 40 is respectively coated and laid on the outer wall surface of the inner crucible 20 and the inner wall surface of the outer crucible 10.

[0039] Compared with the prior art, the double-layer crucible 100 provided by the embodiment of the present application includes an outer crucible 10 and an inner crucible 20 with the same opening direction, and the inner crucible 20 is sleeved inside the outer crucible 10. Crystal pulling is performed inside the inner crucible 20. A feeding space 30 is formed between the inner wall of the outer crucible 10 and the outer wall of the inner crucible 20 to feed silicon liquid 200 into the feeding space 30. A through hole 21 communicating with the outer crucible 10 is provided at the bottom or side of the inner crucible 20, so that the silicon liquid 200 in the feeding space 30 can be supplemented into the inner crucible 20 through the through hole 21, so as to realize feeding while pulling crystals, without interfering with each other, and realize continuous feeding and continuous crystal pulling. Moreover, at least one anti-corrosion isolation coating 40 is respectively coated and laid on the outer wall surface of the inner crucible 20 and the inner wall surface of the outer crucible 10 to prevent and isolate the direct contact between the silicon liquid 200 and the inner crucible 20 and the outer crucible 10, avoid the corrosion of the crucible by the silicon liquid 200, so as to realize greatly reducing or even avoiding the corrosion of the crucible by the silicon liquid 200 without affecting the efficiency of continuous crystal pulling operation, and further effectively reduce the oxygen content of the CCZ silicon wafer prepared by the CCZ technology, and at the same time effectively extend the service life of the quartz crucible, which is more conducive to the popularization of the CCZ technology.

[0040] A specific embodiment is, as Figure 4 shown, the aforementioned anti-corrosion isolation coating 40 can be made of at least one of a boron nitride layer, a zirconia layer, a silicon nitride layer, an alumina layer, and a silicon carbide layer. The boron nitride layer, zirconia layer, silicon nitride layer, alumina layer, and silicon carbide layer are respectively made of boron nitride material, zirconia material, silicon nitride material, alumina material, and silicon carbide material, and have strong anti-corrosion properties.

[0041] A further embodiment is that the aforementioned anti-corrosion isolation coating 40 can be coated with one or more layers. In order to further ensure the isolation reliability of the anti-corrosion isolation coating 40, if the anti-corrosion isolation coating 40 is coated with one layer, the thickness of the one-layer anti-corrosion isolation coating 40 is between 0.5 mm and 2 mm. If the anti-corrosion isolation coating 40 is coated with multiple layers layer by layer, the total thickness of the multiple-layer anti-corrosion isolation coating 40 is between 0.5 mm and 2 mm. With such a setting, the thickness of the anti-corrosion isolation coating 40 cannot be too thin, and the isolation reliability of the anti-corrosion isolation coating 40 needs to be ensured, nor can it be too thick, which will waste materials and occupy too much feeding space 30.

[0042] A preferred embodiment is, as Figure 3 and Figure 4 shown, both the aforementioned inner crucible 20 and the aforementioned outer crucible 10 can adopt a cylindrical structure, and the central axis of the inner crucible 20 coincides with the central axis of the outer crucible 10, as Figure 3 and Figure 4The central axis a shown in [figure]. With such a setting, it is not only convenient for feeding and processing production, but also this structural form is conducive to gravity concentration.

[0043] Based on the foregoing embodiments, a specific embodiment is that the diameter dimension of the inner crucible 20 can be between 659 mm and 920 mm, and the diameter dimension of the outer crucible 10 can be between 810 mm and 1070 mm. Further, the diameter difference between the inner crucible 20 and the outer crucible 10 can be greater than or equal to 150 mm, that is, the distance between the outer wall of the inner crucible 20 and the inner wall of the outer crucible 10 is greater than or equal to 75 mm, so as to leave as much space as possible for feeding.

[0044] Another preferred embodiment is that the anti-corrosion isolation coating 40 can be specifically formed by coating with a slurry. The slurry can be made by mixing a high-temperature binder, coating material powder, and water; preferably, after coating, it is heated and quickly cured.

[0045] With such a setting, using a high-temperature binder, coating material powder, and water to mix and make the slurry required for the anti-corrosion isolation coating 40 can increase the viscosity, conformability, and coating reliability of the slurry. And preferably, it is coated layer by layer evenly. And while coating the slurry, the inner crucible 20 and the outer crucible 10 are heated to immediately volatilize the moisture of the slurry, so as to quickly cure the slurry and form the anti-corrosion isolation coating 40; then after the anti-corrosion isolation coating 40 is made, the inner crucible 20 can be placed and sleeved inside the outer crucible 10, and the bottom of the inner crucible 20 is placed on the bottom of the outer crucible 10, and the central axes of the inner crucible 20 and the outer crucible 10 are aligned and coincident, then the double-layer crucible 100 of the embodiment of the present application can be made.

[0046] Using the powdered coating material powder as described above can improve the uniformity and denseness of the anti-corrosion isolation coating 40. And preferably, the particle size of the coating material powder is between 0.1 and 5 μm. And according to which one or more of the coating layers of boron nitride layer, zirconia layer, silicon nitride layer, alumina layer, and silicon carbide layer are actually selected for the anti-corrosion isolation coating 40, the coating material powder specifically may include one or more of boron nitride powder, zirconia powder, silicon nitride powder, alumina powder, and silicon carbide powder.

[0047] A further embodiment is that the ratio of the coating material powder, high-temperature binder, and water in the prepared slurry is preferably: coating material powder: high-temperature binder: water = 1: 0.1 - 0.5: 0.5 - 2. With such a ratio, the slurry will not be too thin nor too viscous, which can not only enable the slurry to be well coated on the surface of the crucible (including the inner surface of the outer crucible 10 and the outer surface of the inner crucible 20), but also make the thickness of the coated slurry more uniform and the flow rate of the slurry easier to control.

[0048] Another further embodiment is that while coating the aforementioned slurry, it is preferably heated to rapidly cure and form the anti-corrosion isolation coating 40; wherein, the heating temperature is preferably 30 to 150 °C. This heating temperature can well play the role of rapidly volatilizing the moisture in the slurry without affecting the use function of the crucible.

[0049] Correspondingly, an embodiment of the present application also provides a preparation method for the aforementioned double-layer crucible 100, and this preparation method may include:

[0050] Manufacturing the anti-corrosion isolation coating 40, first mixing a high-temperature binder and coating material powder with water to make a slurry, and then coating the slurry on the outer wall surface of the aforementioned inner crucible 20 and the inner wall surface of the aforementioned outer crucible 10, and simultaneously heating the inner crucible 20 and the outer crucible 10 to volatilize the moisture in the slurry, so as to rapidly cure the slurry to form the aforementioned anti-corrosion isolation coating 40;

[0051] Manufacturing the double-layer crucible 100, after manufacturing the anti-corrosion isolation coating 40, placing the inner crucible 20 sleeved inside the outer crucible 10, and placing the bottom of the inner crucible 20 on the bottom of the outer crucible 10, and making the central axes of the inner crucible 20 and the outer crucible 10 coincide in alignment, that is, forming the double-layer crucible 100 provided by the embodiment of the present application.

[0052] Compared with the prior art, the above preparation method for the double-layer crucible 100 provided by the embodiment of the present application specifically mixes a high-temperature binder and coating material powder with water to make the slurry required for manufacturing the anti-corrosion isolation coating 40, which can increase the viscosity, adhesiveness and coating reliability of the slurry, and while uniformly coating the slurry, heating the inner crucible 20 and the outer crucible 10 to immediately volatilize the moisture in the slurry, so as to rapidly cure the slurry to form the anti-corrosion isolation coating 40; then after manufacturing the anti-corrosion isolation coating 40, placing the inner crucible 20 sleeved inside the outer crucible 10, and placing the bottom of the inner crucible 20 on the bottom of the outer crucible 10, and making the central axes of the inner crucible 20 and the outer crucible 10 coincide in alignment, that is, manufacturing the double-layer crucible 100.

[0053] The preparation method for the double-layer crucible 100 can not only effectively block the direct contact between the silicon liquid 200 and the inner crucible 20 and the outer crucible 10, avoid the corrosion of the crucible by the silicon liquid 200, reduce the oxygen content of the silicon rod prepared by the CCZ technology, and extend the service life of the quartz crucible, but also improve the viscosity, adhesiveness and reliability of the anti-corrosion isolation coating 40, and further improve the service life of the quartz crucible.

[0054] One specific embodiment is that in the step of heating the inner crucible 20 and the outer crucible 10 to volatilize the moisture in the slurry so as to rapidly solidify the slurry to form the anti-corrosion isolation coating 40, preferably the heating temperature can be specifically 30 to 150 °C. This heating temperature can well play the role of rapidly volatilizing the moisture in the slurry without affecting the use function of the crucible.

[0055] Another specific embodiment is that the aforementioned slurry can be uniformly coated on the outer wall surface of the aforementioned inner crucible 20 and the inner wall surface of the aforementioned outer crucible 10 by spraying or brushing.

[0056] A further embodiment is that in the step of fabricating the anti-corrosion isolation coating 40, according to different target coating thickness requirements for fabricating the anti-corrosion isolation coating 40, coating can be carried out layer by layer until the target coating thickness is reached to improve the coating uniformity. The target coating thickness can be specifically 0.5 mm to 2 mm according to actual requirements.

[0057] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A double-layer crucible, characterized in that, Comprising: An outer crucible and an inner crucible with the same opening direction. The inner crucible is sleeved inside the outer crucible. A feeding space is formed between the inner wall of the outer crucible and the outer wall of the inner crucible, and a through hole communicating with the outer crucible is provided at the bottom or side of the inner crucible; At least one anti-corrosion isolation coating is respectively coated and laid on the outer wall surface of the inner crucible and the inner wall surface of the outer crucible.

2. The double-layer crucible according to claim 1, wherein The anti-corrosion isolation coating is at least one of a boron nitride layer, a zirconia layer, a silicon nitride layer, an alumina layer, and a silicon carbide layer.

3. The double-layer crucible according to claim 1 or 2, wherein There are multiple layers of the anti-corrosion isolation coating, and the multiple layers of the anti-corrosion isolation coating are coated layer by layer.

4. The double-layer crucible according to claim 3, wherein The total thickness of one or more layers of the anti-corrosion isolation coating is 0.5 mm to 2 mm.

5. The double-layer crucible according to claim 1 or 2, wherein Both the inner crucible and the outer crucible adopt a cylindrical structure, and the central axis of the inner crucible coincides with the central axis of the outer crucible.

6. The double-layer crucible according to claim 5, wherein The diameter of the inner crucible is between 659 mm and 920 mm; The diameter of the outer crucible is between 810 mm and 1070 mm; The diameter difference between the inner crucible and the outer crucible is greater than or equal to 150 mm.

7. The double-layer crucible according to claim 1, wherein The anti-corrosion isolation coating is formed by coating a slurry. The slurry includes coating material powder, a high-temperature binder, and water; the coating material powder includes one of boron nitride powder, zirconia powder, silicon nitride powder, alumina powder, and silicon carbide powder.

8. The double-layer crucible according to claim 7, wherein The particle size of the coating material powder is between 0.1 and 5 μm.

9. The double-layer crucible according to claim 7 or 8, wherein The slurry is heated and cured to form the anti-corrosion isolation coating; The heating temperature is 30 to 150 °C.

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