CN220224427U

CN220224427U - Independent graphite crucible for pulling crystal of single crystal furnace

Info

Publication number: CN220224427U
Application number: CN202321591162.8U
Authority: CN
Inventors: 袁玉平; 金胜; 袁佳斌; 朱桂新
Original assignee: Changzhou Yifan Technology Co ltd
Current assignee: Changzhou Yifan Technology Co ltd
Priority date: 2023-06-20
Filing date: 2023-06-20
Publication date: 2023-12-22
Anticipated expiration: 2033-06-20

Abstract

The utility model relates to an independent graphite crucible for pulling crystal of a single crystal furnace, which is provided with a graphite crucible substrate (1) and a high-temperature resistant protective layer (2); the high-temperature resistant protective layer is a coating and is covered and fixed on the inner wall of the graphite crucible matrix, so that the inner wall of the graphite crucible matrix is closed. The graphite crucible base body is a graphite homogeneous integral piece. The high temperature resistant protective layer (2) is a silicon carbide coating, a silicon nitride coating, a graphite coating, or a boron nitride coating. The graphite crucible base body (1) sequentially comprises a pot side section (1-1), a transition section (1-2) and a pot bottom (1-3) from top to bottom, and the thickness of the pot bottom (1-3) is larger than the wall thickness of the pot side section (1-1). The bottom (1-3) of the pot is provided with a positioning mechanism (1-4) which is downwards oriented and is positioned at the center of the graphite crucible base body. When the independent graphite crucible is used as a crystal pulling crucible, the independent graphite crucible is free from infiltration in a state of storing molten silicon, and has longer service life and better stability.

Description

Independent graphite crucible for pulling crystal of single crystal furnace

Technical Field

The present utility model relates to an apparatus for pulling a silicon single crystal rod, and more particularly, to a pulling crucible for a single crystal furnace for pulling a silicon single crystal rod.

The molten silicon referred to herein is also referred to as liquid silicon, molten silicon or silicon melt.

Background

Solar photovoltaic power generation is the cleanest new energy at present, and has good development prospect. The main parts of the solar photovoltaic power generation device are a bracket and a solar panel, and the panels are mainly monocrystalline silicon panels and polycrystalline silicon panels, and currently are mainly monocrystalline silicon panels. The main body of the monocrystalline silicon battery plate is made of monocrystalline rods, and the main cost for manufacturing the monocrystalline rods is mainly quartz crucible, thermal field, electricity cost and labor except silicon material. Wherein the quartz crucible accounts for a large proportion of the total drawing cost of the single crystal rod.

The current crystal pulling crucible for pulling a single crystal rod is a combined crystal pulling crucible, and the structure is formed by sleeving an outer crucible outside an inner crucible. The inner crucible is a quartz crucible and mainly plays roles of filling to provide liquid silicon material for drawing of the monocrystalline silicon rod and preventing leakage, and the outer crucible is a pot support, and the material of the outer crucible is usually graphite material or carbon/carbon composite material and mainly plays a supporting role. The pan support is arranged on a tray component, the tray component is arranged on a supporting rod (also called a tray shaft or a rotating shaft), and the supporting rod is controlled to rotate by a motor. Because the quartz crucible and the outer crucible are unlikely to be tightly matched with each other, a certain gap exists, when the silicon material is heated to 1350 ℃, the quartz crucible begins to soften, the gap between the quartz crucible and the outer crucible is filled along with the rising of the temperature, and the quartz crucible and the outer crucible are tightly attached together after the temperature is high, so that the supporting and protecting effects of the outer crucible are realized. The disadvantage of such a combination crucible is that the quartz crucible reacts with the liquid silicon at high temperature to form silicon monoxide and free oxygen, some of which enters the pulled single crystal silicon rod, causing an increase in its oxygen content, which adversely affects the conversion efficiency of the cell, and the combination crucible is a device which in use reduces the quality of the single crystal rod. Chinese patent document CN 217733358U (chinese patent application No. 202221817303.9, hereinafter referred to as document 5) discloses a graphite crucible apparatus capable of continuously growing single crystal silicon crystal, wherein the graphite crucible is a heat conductive member for holding the quartz crucible in a crystal heating furnace.

The graphite crucible is usually processed by taking natural crystalline flake graphite as a main raw material and taking plastic refractory clay or carbon as a binder, and has the characteristics of high temperature resistance, strong heat conduction performance, good corrosion resistance, long service life and the like. In the high-temperature use process, the thermal expansion coefficient is small, and the alloy has certain strain resistance to quenching and rapid heating. Has strong corrosion resistance to acidic and alkaline solutions, excellent chemical stability and no participation in any chemical reaction in the smelting process. The inner wall of the graphite crucible is smooth, and molten metal liquid is not easy to leak and adhere to the inner wall of the crucible, so that the metal liquid has good fluidity and casting property, and is suitable for casting and forming of various different moulds. Because the graphite crucible has the excellent characteristics, the graphite crucible is widely used for smelting alloy tool steel and nonferrous metals and alloys thereof.

The isostatic pressing technology is one kind of ultrahigh pressure hydraulic equipment with sealed high pressure container and product inside it being molded in equal ultrahigh pressure state. Isostatic pressing technology is divided into three different types of cold isostatic pressing, warm isostatic pressing and hot isostatic pressing according to the temperature during forming and consolidation.

Cold isostatic pressing (Cold Isostatic Pressing, CIP for short) is to use rubber or plastic as a sheath die material and liquid as a pressure medium at normal temperature, and is mainly used for powder material molding, and to provide a blank for further sintering, calcining or hot isostatic pressing processes. The pressure is generally 100 to 630MPa.

The pressing temperature of the temperature isostatic pressing process is generally 80-120 ℃, and also 250-450 ℃, and the pressure of the temperature isostatic pressing process is about 300MPa by using special liquid or gas transmission pressure. The method is mainly used for graphite, polyamide rubber materials and the like which cannot be formed by powder materials at room temperature. So that a solid green body is obtained at an elevated temperature.

The hot isostatic pressing (Hot Isostatic Pressing, HIP) process is to place a product in a closed container, apply a high temperature while applying equal pressure to the product, and sinter or densify the product under the action of the high temperature and high pressure. The method is not only used for consolidation of powder, and completes two steps of molding and sintering of the traditional powder metallurgy process, but also used for diffusion bonding of workpieces, elimination of casting defects, manufacturing of parts with complex shapes and the like. In hot isostatic pressing, inert gases such as argon and ammonia are generally used as pressure transmission media, and the sheath material is generally metal or glass. The working temperature is generally 900-2200 ℃, and the working pressure is generally 100-200 MPa.

Chinese patent document CN 103286850A (chinese patent application No. 201210360456.X, hereinafter referred to as document 1) discloses a method for forming a graphite crucible at one time and a dedicated mold thereof, wherein the steps of cold isostatic pressing, roasting, graphitization and the like are adopted for forming the graphite crucible.

As a technique of forming a coating layer on a graphite crucible as a base, chinese patent document CN 115819119A (chinese patent application No. 202211672659.2, hereinafter referred to as document 2) discloses a "coating layer forming method of an isostatic pressure graphite crucible". The method comprises the steps of taking an isostatic pressing graphite crucible as a graphite crucible substrate for coating forming, firstly dissolving SiC powder, yttrium oxide and phenolic resin in absolute ethyl alcohol to prepare uniform SiC-yttrium oxide slurry during forming, then forming the slurry into a transition layer by using an impregnation method, mixing Si powder, siC powder and graphite powder by using deionized water, adding polyvinyl alcohol, and heating in a water bath to obtain coating slurry; and then spraying the coating slurry on the surface of the transition layer in a pressure spraying mode, and then sending the coating slurry into a roasting furnace, and sintering at a high temperature under a protective gas environment to obtain a finished product isostatic pressing graphite crucible with a coating. Document 2 shows that the invention can effectively improve the high temperature resistance and oxidation resistance of the isostatic pressing graphite crucible and can ensure the durability of the isostatic pressing graphite crucible. The literature considers that the coating prepared by the chemical vapor deposition method has higher density and better uniformity, but the technical process is complex, the production cost is higher, the binding force between the coating and the matrix is weaker, and the cracking is easy to occur; the brushing method is simple to operate, but the prepared coating is not compact enough and has poor oxidation resistance; the embedding method is similar to the liquid phase dipping method in operation process, has simple process and high processing efficiency, is suitable for industrial production, but the prepared coating has uneven thickness and higher preparation temperature, and can obtain a compact coating by secondary treatment, thereby having complex process. "

For the chemical vapor deposition method, chinese patent document CN108977795a (chinese patent application No. 201710396960.8, hereinafter referred to simply as document 3) discloses "an apparatus and method for producing a silicon carbide coating by an electrically coupled chemical vapor deposition method". Document 3 discloses a method for preparing a silicon carbide coating on a C/C composite material or a graphite substrate by using a specific apparatus and applying an electrically coupled chemical vapor deposition (E-CVD), which shortens the preparation period of the coating, and simultaneously reduces the preparation cost of the material, wherein the preparation period of the coating is shortened from tens of hours to even tens of hours to within 10 hours, and the thickness of the coating is 30-200 μm. The examples of this document show that there is no secondary treatment step.

Graphite crucibles are mainly used for melting metallic materials, and no information has been found in the prior art that a graphite crucible was successfully used for a crystal pulling crucible. Although chinese patent document CN202643902U (chinese patent application No. 201220192925.7, hereinafter referred to as document 4) discloses a single crystal furnace graphite crucible lifting device. The device comprises a split graphite crucible serving as an outer crucible, a graphite crucible serving as an inner crucible and a graphite crucible tray serving as a support for the split graphite crucible. Document 4 indicates in its background art that "single crystal silicon is generally produced by the CZ method". The CZ method is to dissolve raw material silicon in a graphite crucible by means of a heater, and then immerse a seed crystal mounted on a seed crystal chuck in the solution. However, according to the CZ method, the raw material silicon should not be dissolved but should be melted, and further, the seed crystal is immersed in the melt instead of the solution. After the correction, if the graphite crucible is used for melting the silicon material, first, since the graphite crucible is obtained by sintering graphite powder through hot isostatic pressing, a certain gap exists, so that liquid silicon permeates into the graphite internal gap of the graphite crucible, and when the single crystal furnace is cooled down, the graphite crucible bursts due to the effect of thermal expansion and cold contraction. And a certain gap is formed between the second graphite crucible and the split graphite crucible, so that a good supporting and protecting effect cannot be achieved, namely, the stability is poor. Therefore, the graphite crucible of document 1 has no practical applicability.

In addition, no separate graphite crucible for pulling a crystal in a single crystal furnace has been found in the prior art.

Disclosure of Invention

The utility model aims to provide an independent graphite crucible which is free from infiltration in a state of storing molten silicon, long in service life and good in stability and is used for pulling a single crystal silicon rod by a single crystal furnace.

The technical scheme for realizing the aim of the utility model is as follows: the independent graphite crucible for pulling the crystal of the single crystal furnace provided by the utility model is provided with a graphite crucible substrate and a high-temperature resistant protective layer. The high-temperature resistant protective layer is a coating and is covered and fixed on the inner wall of the graphite crucible matrix, so that the inner wall of the graphite crucible matrix is closed. The structure is characterized in that: the graphite crucible substrate is a graphite homogeneous integrated piece. The high temperature resistant protective layer is a silicon carbide coating or a silicon nitride coating, or a graphite coating or a boron nitride coating. The graphite crucible base body is provided with a pot side section, a transition section and a pot bottom in sequence from top to bottom, and the thickness of the pot bottom is larger than the wall thickness of the pot side section. The wall thickness of the upper part of the transition section is the same as the wall thickness of the lower part of the pot side section, and the wall thickness of the lower part of the transition section is the same as the wall thickness of the upper part of the bottom of the pot. The bottom of the pot is provided with a positioning mechanism which faces downwards and is positioned in the center of the graphite crucible base body.

In the scheme, the melting point of silicon is below 1420 ℃, and the high temperature resistance means that the material has the functions of not decomposing and not softening at the working temperature of 1600 ℃. The melting point of the graphite crucible is 3527 ℃, and the corresponding working temperature is 1800 ℃. When the single crystal furnace performs the operation of drawing the single crystal silicon rod, the independent graphite crucible provided with the high-temperature resistant protective layer is stable and durable. Namely, when the independent graphite crucible in the scheme is used for containing liquid silicon materials and carrying out crystal pulling operation, the independent graphite crucible not only can replace a quartz crucible, but also can greatly prolong the service life.

In the scheme, the graphite crucible substrate is an extension product of high-purity graphite and is mainly processed by the method of isostatic compaction of the high-purity graphite, has the characteristics of the high-purity graphite, and has the main characteristics of small thermal expansion rate, excellent thermal conductivity after heating and the like, and the thermal conductivity coefficient of the graphite crucible substrate is 151W/m.K. Of course, the graphite crucible base body of the high purity graphite material has a certain internal pore when being molded.

In the scheme, the high-temperature-resistant protective layer is arranged on the inner wall of the graphite crucible substrate, and the high-temperature-resistant protective layer plays a role in sealing the inner pores of the inner wall surface of the graphite crucible substrate, so that when liquid silicon is contained in the graphite crucible substrate, the liquid silicon cannot permeate into the inner pores of the graphite crucible substrate, and the production safety of the crystal pulling container when a monocrystalline silicon rod is pulled is ensured.

In the above-described embodiments, the silicon carbide coating layer or the silicon nitride coating layer is a coating layer obtained by an MOCVD method (MOCVD method refers to a metal organic chemical vapor deposition method) among chemical vapor deposition methods. The graphite coating is a coating obtained by a PG method of pyrolytic graphite. The boron nitride coating is a coating obtained by adopting a Pyrolytic Boron Nitride (PBN) method.

In the scheme, the bottom of the pot is thicker than the pot side section, so that the independent graphite crucible can rotate stably during crystal pulling, and heat conduction is not affected basically. Positioning means at the bottom of the pot may allow the individual graphite crucible to be positioned on the tray member (which may be of graphite material) of the single crystal furnace.

Further, in the independent graphite crucible for pulling a single crystal furnace according to the present utility model, the thickness of the high temperature resistant protective layer is 1 to 40 microns, preferably 1 to 29 microns, and more preferably 3 to 10 microns.

Furthermore, in the independent graphite crucible for pulling the crystal of the single crystal furnace, the wall thickness of the side section of the graphite crucible substrate is 12 to 25 mm. The thickness of the bottom of the pot is 2 to 5 times of the wall thickness of the pot side section. The wall thickness of the pot side section is preferably 15 to 25 mm.

In the above-described embodiment, the wall thickness W of the rim section of the graphite crucible base body is a determined value, and may be selected from the range of 12.+ -.1 to 25.+ -.1 mm (preferably 15.+ -. 1 to 25.+ -. 1 mm), for example, 20.+ -. 1 mm. The wall thickness has a certain value, and the material of the wall thickness is high-purity graphite, so that the independent graphite crucible has a certain strength, and excellent mechanical properties at high temperature can be ensured; the upper limit of the thickness is limited, namely, when the thickness is thinner, the cost of the product is controlled within a certain range, and the heat radiated by a thermal field is favorably transferred to the contained silicon material in the process of melting the contained silicon material or maintaining the temperature of the contained liquid silicon material.

In the above solution, the thickness of the bottom of the pan is 2 to 5 times the wall thickness of the rim section, said multiple being a variable value, e.g. 2 times the thickness of the rim section in the upper part of the bottom of the pan and 3.5 times the thickness of the rim section in the lower part of the bottom of the pan, etc. The thickness of the bottom of the pot is larger, so that the pot bottom can generate larger friction resistance when passively rotating in the crystal pulling process, and the stable rotation of the independent graphite crucible in the crystal pulling process is facilitated; in addition, because the thermal field in the single crystal furnace is arranged around the pot side part, the increased thickness of the pot bottom can also play a certain role in heat preservation, and the design plays a positive role in maintaining the temperature stability of the contained liquid silicon although the increase of the weight can lead to the increase of the cost.

Furthermore, in the independent graphite crucible for pulling the crystal of the single crystal furnace, the outer diameter of the pot side section of the graphite crucible base body is 500-1050 mm, and the height-diameter ratio of the graphite crucible base body is 0.6-0.8.

In the scheme, the height of the graphite crucible base body is smaller than the outer diameter, and the height-diameter ratio is 0.6-0.8. The graphite crucible in the prior art is specified by China national Standard (standard No. GB/T26979-2010), wherein the graphite crucible is divided into 40 types of No. 1, no. 1.5 and No. … … in sequence from small to large in the outer diameter of the upper opening of the graphite crucible, the outer diameters of the upper openings of the graphite crucible and the graphite crucible are 67, 78 and … 880 millimeters in sequence, the heights of the graphite crucible and the graphite crucible are 65, 80 and … … 1150 millimeters in sequence, and the height-diameter ratio of the graphite crucible and the graphite crucible is 0.97, 1.025 and … … 1.30.30 in sequence; wherein, except that the height of the No. 1 graphite crucible is smaller than the outer diameter, the heights of the graphite crucibles of the other 39 types are all larger than the outer diameter. As the graphite crucible size increases, their aspect ratio increases gradually. In addition, the graphite crucible in the prior art has a round pot shape in the whole shape, namely, the upper part and the middle part of the graphite crucible are round pot shapes with the outer diameters ranging from large to small and the wall thicknesses ranging from small to large, the lower part serving as the bottom of the graphite crucible is a part with thicker thickness, and the bottom surface of the graphite crucible is in the shape of a horizontal plane.

Furthermore, in the independent graphite crucible for pulling the crystal of the single crystal furnace, the positioning mechanism at the bottom of the crucible is a cylindrical positioning boss and an upper contact surface, the diameter of the positioning boss is 150-300 mm, and the height of the positioning boss is 5-20 mm. The upper side contact surface is located above and around the positioning boss, and the outer diameter of the upper side contact surface is 1.5 to 2 times the diameter of the positioning boss.

In the above scheme, when in use, the independent graphite crucible is placed on a tray member (which can be made of graphite) provided with a matching mechanism matched with the positioning mechanism. The engagement means is an engagement recess and an upwardly facing engagement contact surface disposed about the engagement recess. When the graphite crucible positioning device is used, the independent graphite crucible is located on the tray component, the matched contact surface of the tray component is in contact with the upper side contact surface of the positioning mechanism, so that surface-to-surface friction resistance is formed between the matched contact surface and the upper side contact surface, and the positioning boss and the matched groove are in clearance fit, so that the independent graphite crucible is positioned on the tray component.

Furthermore, in the independent graphite crucible for pulling the crystal of the single crystal furnace, the positioning mechanism at the bottom of the crucible is a cylindrical positioning groove and a lower contact surface. The positioning groove has a diameter of 150 to 300 mm and a height of 5 to 20 mm. The lower side contact surface is located below and around the positioning groove, and the outer diameter of the lower side contact surface is 1.5 to 2 times the diameter of the positioning groove.

In the above scheme, when in use, the independent graphite crucible is placed on a tray member, and the tray member is provided with a matching mechanism matched with the positioning mechanism. The engagement means is an engagement projection and an upwardly facing engagement contact surface disposed about the engagement projection. When the graphite crucible positioning device is used, the independent graphite crucible is located on the tray component, the matched contact surface of the tray component and the contact surface of the lower side of the positioning mechanism are in contact with each other, so that surface-to-surface friction resistance is formed between the matched contact surface and the contact surface, and the mutual relation between the positioning groove and the matched boss is clearance fit, so that the independent graphite crucible is positioned on the tray component.

Furthermore, in the independent graphite crucible for pulling the crystal of the single crystal furnace, the high-temperature resistant protective layer is preferably a graphite coating obtained by adopting a PG method of pyrolytic graphite or a boron nitride coating.

In the above proposal, the silicon melting point is below 1420 ℃, and the components of the high temperature resistant protective layer are silicon carbide, silicon nitride, graphite or boron nitride, preferably graphite or boron nitride, and the working temperatures of the four high temperature resistant protective layers are 1800 ℃, 1600 ℃, 1800 ℃ and 1800 ℃ which are far higher than 1420 ℃, so that the high temperature resistant protective layer of the independent graphite crucible is stable and durable and does not soften or melt when the single crystal furnace performs the operation of drawing the single crystal silicon rod. The graphite crucible substrate is formed by an isostatic pressing method, preferably a hot isostatic pressing method. The high temperature resistant protective layer is a graphite coating obtained by a PG method of pyrolytic graphite or a boron nitride coating obtained by a PBN method of pyrolytic boron nitride.

The independent graphite crucible is a brand new product, and the positive effects of the utility model can be reflected in the following aspects.

(1) The use of the self-contained graphite crucible of the present utility model not only overcomes the technical prejudice in the art that only quartz crucibles have been considered as crystal pulling crucibles, but also achieves unexpected technical results.

For quartz crucible as the pull crucible, those skilled in the art generally consider: "A crystal pulling crucible for preparing a silicon single crystal rod must be a quartz crucible. This is because the quartz crucible has high temperature stability and chemical inertness, can withstand chemical corrosion and mechanical stress at high temperature, and does not affect the purity and quality of single crystal silicon. Meanwhile, the quartz crucible has good heat conduction performance, can rapidly and uniformly transfer heat, and is beneficial to the growth and formation of monocrystalline silicon. Therefore, a quartz crucible is one of the necessary devices for preparing a single crystal silicon rod. The above-mentioned viewpoints are almost common knowledge to the person skilled in the art.

However, the inventors of the present utility model found that: although the quartz crucible has high temperature stability and chemical inertness, the single crystal silicon rod being pulled has a certain oxygen content, which is disadvantageous for further improvement of the quality of the single crystal silicon rod. In addition, although the quartz crucible has lower cost, the service life of the quartz crucible is limited, 5 to 7 single crystal silicon rods (about 20 days) can be pulled at high temperature, and the quartz crucible cannot be reused after the single crystal furnace is cooled.

The independent graphite crucible provided by the utility model can be repeatedly used, and the service life of the independent graphite crucible can reach 1-2 years or more. In the industry, the cost of a high-purity quartz crucible used as an inner crucible seriously affects the cost of a solar photovoltaic power generation panel, and is controlled abroad, so that the constraint of the quartz crucible is eliminated, and the problem which is urgently needed to be solved currently. The independent graphite crucible of the utility model can solve the problem of urgent need of the development of the restriction industry.

(2) When the independent graphite crucible is used as a crystal pulling crucible, the quartz crucible is not used any more, the oxygen content in the high-temperature silicon melt is obviously reduced compared with that of the quartz crucible, and the high-temperature resistant protective layer cannot react with the high-temperature silicon melt at high temperature, so that the reaction of the quartz crucible and the high-temperature silicon melt in the prior art to generate trace free oxygen is avoided, and the quality of the monocrystalline silicon rod is improved.

(3) The independent graphite crucible of the utility model has the same shape as the conventional graphite crucible and the quartz crucible, and is a completely new crucible.

According to the specification of the national building material industry standard JC/T1048-2018 quartz crucible for growing monocrystalline silicon, the standard is applicable to the quartz crucible for growing monocrystalline silicon materials by adopting high-purity quartz sand as a raw material and adopting an arc method production process. The standard gives a schematic outline of the quartz crucible. From this schematic view, the quartz crucible has substantially the same wall thickness in each portion, and a cylindrical main portion and a bowl-shaped lower portion. Thus, it is known that the quartz crucible can be divided into a straight-walled cylindrical portion, a curved-arc wall transition portion, and a bowl-shaped bottom portion in this order from top to bottom. It is also known from this schematic view that the outer diameter and the height of the quartz crucible are close.

Since the independent graphite crucible of the present utility model is used as a crystal pulling crucible, and the quartz crucible is also used as a main crucible for the crystal pulling crucible, if the rim section, the transition section, and the bottom of the crucible of the present utility model are compared with the straight-walled cylindrical portion, the curved-wall transition portion, and the bowl-shaped bottom of the quartz crucible in this order, there are the following aspects, the same and different:

the shape of the side section of the pot is basically the same as that of the straight-wall cylindrical part of the quartz crucible, and the height-diameter ratio of the side section and the straight-wall cylindrical part is basically the same, so that common factors are considered when a single crystal silicon rod is pulled, wherein the common factors include that the liquid level of liquid silicon under rotation should be ensured to be stable as much as possible during pulling, the height of the crystal pulling crucible cannot be too high, the ratio of the diameter of the single crystal silicon rod to the outer diameter of the crystal pulling crucible is about 1/3, and the like, so that the outer diameter of the crystal pulling crucible cannot be too small, and the outer diameter of the crystal pulling crucible is always larger than the height.

Second, the wall thickness of the transition section of the present utility model increases gradually, while the wall thickness of the curved wall transition section of the quartz crucible is substantially unchanged. The quartz crucible (also called as inner crucible) for conventional crystal pulling is positioned in the graphite crucible (also called as graphite pot support or outer crucible) when in use, and the inner crucible and the outer crucible are mutually matched for normal use, so that the wall thickness of the quartz crucible serving as the inner crucible only needs to meet the strength requirement, and basically adopts the scheme that the wall thickness is the same everywhere, thereby not only being convenient to operate, but also having lower cost.

Thirdly, the thickness of the bottom of the pot is 2 to 5 times of the thickness of the wall of the pot side section, and the thickness of the bowl-shaped bottom of the quartz crucible is the same as the thickness of the rest parts, for the same reason as the second point. The wall thicknesses of the bottom part, the transition section and the side section of the pot are different, and the reason is that the independent graphite crucible is independently used, so that the independent graphite crucible not only plays a role of a crystal pulling crucible, but also plays a role of a pot support, namely plays a dual role of an inner crucible and an outer crucible, and breaks through the structure of the combined crystal pulling crucible in the prior art. The independent graphite crucible is used as the crystal pulling crucible and the pot support, so that the quality of the monocrystalline silicon rod is improved, the service life of the crystal pulling crucible is prolonged, and the cost is greatly reduced.

(4) The crystal pulling crucible is an independent crystal pulling crucible, and no pot support (or outer crucible) is needed, so that on the premise of keeping the volume of the original single crystal furnace not increased, various embodiments can be realized, firstly, the form of the positioning mechanism can have various structures, for example, an elliptic cylindrical positioning boss or a multi-prismatic (for example, triangular prism, quadrangular prism or hexagonal prism) positioning boss and the like can also be adopted, and the positioning groove adopts a corresponding shape. The shape of the independent crucible itself may be deformed within a certain range, and for example, the independent graphite crucible of the present utility model may be manufactured into the shape of the graphite crucible in document 5 (but the aspect ratio is redesigned), and may be combined with a corresponding support member.

Drawings

FIG. 1 is a schematic view showing a structure of a self-contained graphite crucible of the present utility model.

Fig. 2 is a schematic view (reference numerals are different) of the structure of the independent graphite crucible shown in fig. 1.

FIG. 3 is a schematic view showing another structure of the independent graphite crucible of the present utility model. Fig. 4 is a schematic view (reference numerals are different) of the structure of the independent graphite crucible shown in fig. 3.

The reference numerals in the above figures are as follows: the graphite crucible base body 1, the high temperature resistant protective layer 2, the crucible side section 1-1, the transition section 1-2, the bottom of the pot 1-3, the positioning mechanism 1-4, the positioning boss 1-4-1, the upper side contact surface 1-4-2, the positioning groove 1-4-3, the lower side contact surface 1-4-4, the outer diameter A of the side section, the height H of the base body, the wall thickness W of the side section, the radius of curvature R1 of the inner wall of the bottom of the pot, the radius of curvature R2 of the inner wall of the transition section, the radius of curvature R3 of the outer wall of the lower half of the transition section, the radius of curvature R4 of the outer wall of the bottom of the pot, the diameter B of the positioning boss, the outer diameter C of the upper side contact surface, the height D of the positioning boss, the secondary lower position E of the positioning groove, the diameter B 'of the outer diameter C' of the lower side contact surface, the height D 'of the positioning groove and the lowest position E' of the bottom of the pot.

Detailed Description

Example 1

Referring to fig. 1 and 2, the independent graphite crucible for pulling a crystal in a single crystal furnace according to the present embodiment is a pulling crucible which is in direct contact with molten silicon in use, and has a graphite crucible base body 1 and a high temperature resistant protective layer 2.

The graphite crucible substrate 1 is a graphite homogeneous integrated piece prepared by a hot isostatic pressing method, and is made of high-purity graphite.

The graphite crucible base body 1 is sequentially provided with a pot side section 1-1, a transition section 1-2 and a pot bottom 1-3 from top to bottom. The bottom 1-3 of the pot is provided with a positioning mechanism 1-4 which is oriented downwards and is positioned in the center of the graphite crucible base body 1. The positioning mechanism 1-4 is part of the graphite crucible base body 1. The height H of the graphite crucible base body 1 was 300 mm, the outer diameter A of the rim section 1-1 (this outer diameter is also generally regarded as the outer diameter of the base body 1) was 500 mm, and the aspect ratio was 0.6.

The shape of the boiler side section 1-1 is a cylinder, and the wall thickness W is 12 mm.

The transition section 1-2 is cylindrical in shape with an inner diameter gradually decreasing from top to bottom and an outer diameter gradually decreasing from the middle to bottom. The upper wall thickness of the transition section 1-2 is 12 mm and the lower wall thickness is 36 mm, and the wall thickness gradually increases with decreasing height. The inner wall surface of the transition section 1-2 has a spherical band shape with a radius R2 of 94 mm. The upper part of the outer wall surface of the transition section 1-2 is cylindrical, the lower part is spherical, and the radius R3 is 80 mm.

The whole shape of the pan bottom 1-3 is pan-shaped, the shape of the inner wall is spherical crown shape, and the radius R1 is 368 mm. The upper part of the outer wall of the pot bottom 1-3 is a spherical belt shape with the radius smaller than that of the inner wall, and the lower part is a part provided with the positioning mechanism 1-4.

The radius R4 of the spherical belt-shaped part of the outer wall of the pan bottom 1-3 is 278 mm, and the joint of the spherical belt-shaped part and the outer wall of the transition section 1-2 is in smooth transition. The upper part of the thickness of the pot bottom 1-3 is 36 mm, the thickness of the pot bottom 1-3 is gradually increased along with the descending of the height, and the thickness of the secondary lower part E of the pot bottom is 60 mm. The thickness of the bottom 1-3 of the pan is slightly smaller than or close to the thickness of the lower E because of the need of the positioning mechanism 1-4.

The positioning mechanism 1-4 of the bottom 1-3 of the pot is a cylindrical positioning boss 1-4-1 and an upper contact surface 1-4-2, the diameter B of the positioning boss 1-4-1 is 150 mm, and the height D is 5 mm. The upper side contact surface 1-4-2 is located above the positioning boss 1-4-1 and disposed around the positioning boss 1-4-1, and the outer diameter C of the upper side contact surface 1-4-2 is 300 mm, which is 2 times the diameter B of the positioning boss 1-4-1. The inner diameter of the upper side contact surface 1-4-2 is 150 mm, which is the same as the diameter B of the positioning boss 1-4-1.

The graphite crucible substrate 1 of the present embodiment is a graphite crucible substrate manufactured by a cold isostatic pressing method or a hot isostatic pressing method, and the working temperature thereof can reach more than 1800 ℃. The graphite crucible base body 1 of the cold isostatic pressing method can be obtained by the method of reference 1. The hot isostatic pressing method is a common process for preparing graphite crucibles in the prior art, and specific implementation steps have a certain difference.

The first method for manufacturing the graphite crucible base body 1 by the hot isostatic pressing method is as follows: firstly, raw materials are prepared. High purity natural graphite or artificial graphite powder, a binder and a lubricant are uniformly mixed to form a compressible graphite blank. And secondly, pressing into a blank. Loading graphite blanks into a mould, wherein the shape of the mould can be determined according to the shape of the graphite crucible substrate 1 to be prepared; and then pressed under high pressure to form a graphite blank having a certain shape and density. Thirdly, heat treatment. And carrying out heat treatment on the graphite blank at a certain temperature and pressure to ensure that the structure is more compact, and the strength and the hardness of the graphite blank are increased to form a solid graphite blank. Fourthly, machining. The heat treated solid graphite body is machined (e.g., cut, drilled, ground, etc.) to achieve the desired shape and size. Fifthly, hot isostatic pressing. After the machining is completed, the graphite blank is placed in a high-pressure container, and isostatic pressing treatment is carried out at a certain temperature and pressure, namely, a high-temperature sintering treatment mode under high pressure is adopted, so that the solid graphite blank is sintered into the graphite crucible substrate 1. The method not only ensures that the density is more compact and the internal defects are reduced, thereby prolonging the service life and improving the high temperature resistance.

The second method for manufacturing the graphite crucible base body 1 by the hot isostatic pressing method is as follows: adding graphite powder into the mixture, and uniformly stirring to form slurry; pouring the slurry into a crucible type (a mold referring to a graphite crucible matrix), and vibrating the slurry in a vacuum environment; placing the crucible after compaction in a hot isostatic pressing machine, applying high pressure, heating, preserving heat, reducing temperature and releasing pressure, thereby obtaining a semi-finished product of the high-density graphite crucible substrate 1. And then carrying out related mechanical processing, such as polishing, processing the positioning mechanism 1-4 and the like, so as to obtain the graphite crucible base body 1. The method directly adopts the hot isostatic pressing method to prepare the graphite crucible substrate 1, so that the crucible has the advantages of uniform density, higher density, better thermal stability, longer service life and lower cost. The second method is preferred in this embodiment.

The isostatic pressing method has the advantages that the isostatic pressing method can be used for preparing products with the characteristics of complex shape, accurate size, uniform density, excellent mechanical properties, smooth surface layer and the like. Meanwhile, due to the strict control of compression conditions, the internal structure and physical properties of the graphite crucible substrate 1 can be ensured to be uniform, so that the graphite crucible substrate has higher quality stability.

Still referring to fig. 1 and 2, the high temperature resistant protective layer 2 is a coating layer, and is fixed on the inner wall of the graphite crucible base body 1 in a covering manner, so as to play a role in sealing the inner wall of the graphite crucible base body 1. The high temperature resistant protective layer 2 is a graphite coating obtained by a PG method using pyrolytic graphite (in other embodiments, it may be a boron nitride coating obtained by a pyrolytic boron nitride PBN method, or a silicon carbide coating or a silicon nitride coating obtained by an MOCVD method in a chemical vapor deposition method).

The thickness of the high temperature resistant protective layer 12 is 6+ -1 micrometers (in other embodiments, the thickness may be 1+ -1 micrometer, 3+ -1 micrometer, 5+ -1 micrometer, 10+ -1 micrometer, 29+ -1 micrometer, or 40+ -1 micrometer).

The graphite coating layer as the high temperature resistant protective layer 12 in this embodiment is obtained according to the PG method of pyrolytic graphite. The method is also in the prior art, and the graphite coating is coated on the surface of the graphite crucible, and the following steps are adopted: firstly, preparing a graphite source material: the graphite source material may be graphite powder or the like. Secondly, the graphite crucible is subjected to surface treatments, such as cleaning, polishing or etching, to increase the surface roughness and increase the surface area to which acceptable coatings adhere. Thirdly, powder metal tungsten or other metal catalysts are mixed in the graphite source material to obtain a mixture, so as to promote the pyrolysis reaction. And fourthly, adding an organic adhesive into the mixture and uniformly mixing to obtain a viscous graphite coating, and coating the graphite coating on the graphite crucible by using methods such as brushing. The coating should be uniformly distributed during coating and ensure adequate contact between the coating and the crucible surface. Fifth, pyrolyzing the graphite source material: the pyrolysis conditions are PG pyrolysis at normal pressure. In the pyrolysis process, the graphite source material is decomposed into carbon gas under the action of a metal catalyst such as tungsten, and then deposited as a graphite coating layer serving as a high-temperature resistant protective layer 12 on the surface of a graphite crucible.

Example 2

Referring to fig. 3 and 4, the rest of the present embodiment is the same as embodiment 1 except that: the thickness of the lowest part E' of the bottom of the pot in the embodiment is 60 mm. The positioning mechanism 1-4 is composed of a cylindrical positioning groove 1-4-3 and a lower contact surface 1-4-4. The diameter B 'of the positioning groove 1-4-3 is 150 mm and the height D' is 5 mm. The lower side contact surface 1-4-4 is located below the positioning groove 1-4-3 and disposed around the positioning groove 1-4-3, and the outer diameter C 'of the lower side contact surface 1-4-4 is 300 mm, which is 2 times the diameter B' of the positioning groove 1-4-3. The inner diameter of the lower contact surface 1-4-4 is 150 mm, which is the same as the diameter of the positioning groove 1-4-3.

The present embodiment also differs from embodiment 1 in respect of the high temperature resistant protective layer 2 in that: the high temperature resistant protective layer 2 is a boron nitride coating, a silicon carbide film or a silicon nitride coating.

When the high temperature resistant protective layer 2 of the present embodiment is a boron nitride coating, the boron nitride coating can be obtained according to a pyrolytic boron nitride PBN method. The method is also in the prior art, and comprises the following specific steps of: firstly, preparing a boron nitride precursor: boric acid, boron oxide and sol-gel method are used as raw materials, and BN precursor material is prepared by high-temperature sintering or high-temperature precipitation method. Secondly, surface treatment of the graphite crucible: the graphite crucible is subjected to chemical or physical treatments, such as ultrasonic cleaning, sand blasting, or electrochemical treatments, to increase the roughness of the crucible surface and increase the surface area to which acceptable coatings adhere. Thirdly, high temperature reaction: the graphite crucible is placed in a reaction chamber, and a precursor material is placed in a sub-chamber of the reaction chamber, so that the reaction chamber becomes a high-temperature atmosphere to perform a pyrolysis reaction. By choosing a suitable atmosphere, temperature and time, the precursor material can be decomposed into BN, which is then deposited as a coating on the graphite crucible surface. Fourthly, heat post treatment: after the coating is formed, the subsequent treatments such as temperature reduction, atmosphere switching and the like are carried out so as to eliminate possible crystallization defects and residues and ensure the quality and performance of the coating.

It should be noted that the PBN method requires the reaction of the graphite crucible in a high temperature atmosphere, which requires the selection of appropriate reaction parameters such as reaction temperature, reaction time, reaction atmosphere, etc., to control the BN deposition process.

When the high temperature resistant protective layer 2 of the present embodiment is a silicon carbide film, the silicon carbide film is obtained by an MOCVD method (belonging to the prior art), that is, a metal organic chemical vapor deposition method, in which a metal organic compound is sublimated into a metal vapor under a vacuum or inert atmosphere at a certain temperature, and then reacts with other gases to form a solid material. The MOCVD method for forming the silicon carbide coating on the inner wall surface of the graphite crucible comprises the following specific steps: firstly, cleaning the surface of the inner wall of a graphite crucible, removing impurities and dust, and placing the graphite crucible in a vacuum furnace for deoxidizing treatment to ensure that the surface of the graphite crucible is bright and clean. Secondly, for the MOCVD method, specific metal organic compounds and gases are required to be used. First, an appropriate amount of Trimethylsilane (TMS) and ammonia (NH 3) are mixed together, heated to a certain temperature to sublimate it into metal vapor, and then introduced into a graphite crucible. Thirdly, controlling the temperature and atmosphere of the graphite crucible, and realizing the deposition of the coating by controlling the parameters such as the temperature, the gas mass ratio, the flow and the like in the silicon carbide deposition process. Fourthly, in the process of forming the coating, components and structures of the silicon carbide coating are monitored by means of detection of geometrical morphology (SEM), physical and chemical analysis and the like, so that the quality and uniformity of the coating are ensured. And fifthly, after the silicon carbide coating is deposited, the graphite crucible needs to be subjected to subsequent treatment, such as heat treatment or cooling, so as to ensure that the hardness and the density of the coating meet the requirements and improve the chemical and mechanical resistance of the coating.

The silicon carbide film is obtained by adopting an MOCVD method, and proper gas flow, nozzle temperature and medium atmosphere are required to be selected according to specific coating requirements so as to carry out reasonable parameter regulation and control.

When the high temperature resistant protective layer 2 of the present embodiment is a silicon nitride coating, the silicon nitride coating can also be obtained according to the MOCVD method. The method is also in the prior art, mainly utilizes metal organic compounds, nitrogen and inert gas as reaction gases, and mainly comprises the following steps of the process of generating a silicon nitride coating through the gas phase reaction of depositing the metal organic compounds and the nitrogen on the surface of graphite: one is to select suitable metal organic compounds as precursors, such as SiH4, NH3, TMS, DMAH, etc., which can chemically react at elevated temperatures on the graphite surface. Secondly, placing the graphite crucible into an MOCVD reaction furnace, pre-treating, cleaning and drying to remove impurities and moisture on the surface. Thirdly, the deposition of the silicon nitride coating on the surface of the graphite is realized by injecting reaction gases such as metal organic compounds, nitrogen and the like into a reaction chamber of the reaction furnace. In the process, metal atoms generated by decomposition of the metal organic compound react with nitrogen to generate silicon nitride material which is deposited on the surface of graphite to form a uniform silicon nitride coating. And fourthly, after the reaction is finished, cooling treatment is carried out, and the graphite crucible is taken out of the reaction furnace, so that the silicon nitride coating with good oxidation and corrosion performances can be obtained.

Example 3

Still referring to fig. 1 and 2, the remainder of this embodiment is the same as embodiment 1 except that: the height H of the graphite crucible base body 1 was 500 mm, the outer diameter A of the rim section 1-1 (this outer diameter is also generally regarded as the outer diameter of the base body 1) was 750 mm, and the aspect ratio was 0.67. The wall thickness W of the boiler side section 1-1 is 18 mm.

The upper wall thickness of the transition section 1-2 is 18 mm and the lower wall thickness is 54 mm. The radius R2 of the spherical band on the inner wall surface of the transition section 1-2 was 141 mm, and the radius R3 of the spherical band portion on the lower portion of the outer wall surface of the transition section 1-2 was 120 mm.

The radius R1 of the spherical crown-shaped inner wall of the pot bottom 1-3 is 552 mm, and the radius R4 of the spherical belt-shaped part of the outer wall of the pot bottom 1-3 is 417 mm. The upper part of the thickness of the pot bottom 1-3 is 54 mm, and the thickness of the secondary lower part E of the pot bottom is 81 mm.

The diameter B of the positioning boss 1-4-1 of the positioning mechanism 1-4 of the pan bottom 1-3 is 225 mm, the height D is 12.5 mm, and the outer diameter C of the upper contact surface 1-4-2 is 400 mm.

Example 4

Still referring to fig. 1 and 2, the remainder of this embodiment is the same as embodiment 1 except that: the height H of the graphite crucible base body 1 was 700 mm, the outer diameter A of the rim section 1-1 (which is also generally regarded as the outer diameter of the base body 1) was 1050 mm, and the aspect ratio was 0.67. The wall thickness W of the boiler side section 1-1 is 25 mm.

The upper wall thickness of transition section 1-2 is 25 mm and the lower wall thickness is 75 mm. The radius R2 of the spherical band of the inner wall surface of the transition section 1-2 is 188 mm, and the radius R3 of the spherical band portion of the lower portion of the outer wall surface of the transition section 1-2 is 160 mm.

The radius R1 of the spherical crown-shaped inner wall of the pot bottom 1-3 is 735 mm, and the radius R4 of the spherical belt-shaped part of the outer wall of the pot bottom 1-3 is 555 mm. The upper part of the thickness of the pot bottom 1-3 is 75 mm, and the thickness of the secondary lower part E of the pot bottom is 125 mm.

The diameter B of the positioning boss 1-4-1 of the positioning mechanism 1-4 of the pan bottom 1-3 is 300 mm, the height D is 20 mm, and the outer diameter C of the upper contact surface 1-4-2 is 500 mm.

Example 5

Still referring to fig. 3 and 4, the remainder of this embodiment is the same as embodiment 2, except that: the height H of the graphite crucible base body 1 was 500 mm, the outer diameter A of the rim section 1-1 (this outer diameter is also generally regarded as the outer diameter of the base body 1) was 750 mm, and the aspect ratio was 0.67. The wall thickness W of the boiler side section 1-1 is 18 mm.

The radius R1 of the spherical crown-shaped inner wall of the pot bottom 1-3 is 552 mm, and the radius R4 of the spherical belt-shaped part of the outer wall of the pot bottom 1-3 is 417 mm. The upper part of the thickness of the pot bottom 1-3 is 54 mm, and the thickness of the lowest part E' of the pot bottom is 81 mm.

The diameter B ' of the positioning groove 1-4-3 of the positioning mechanism 1-4 of the pan bottom 1-3 is 225 mm, the height D ' is 12.5 mm, and the outer diameter C ' of the lower side contact surface 1-4-4 is 400 mm.

Example 6

Still referring to fig. 3 and 4, the remainder of this embodiment is the same as embodiment 2, except that: the height H of the graphite crucible base body 1 was 700 mm, the outer diameter A of the rim section 1-1 (which is also generally regarded as the outer diameter of the base body 1) was 1050 mm, and the aspect ratio was 0.67. The wall thickness W of the boiler side section 1-1 is 25 mm.

The radius R1 of the spherical crown-shaped inner wall of the pot bottom 1-3 is 735 mm, and the radius R4 of the spherical belt-shaped part of the outer wall of the pot bottom 1-3 is 555 mm. The upper part of the thickness of the pot bottom 1-3 is 75 mm, and the thickness of the lowest part E' of the pot bottom is 125 mm.

The diameter B ' of the positioning groove 1-4-3 of the positioning mechanism 1-4 of the pan bottom 1-3 is 300 mm, the height D ' is 20 mm, and the outer diameter C ' of the lower contact surface 1-4-4 is 500 mm.

Claims

1. An independent graphite crucible for pulling crystal of a single crystal furnace is provided with a graphite crucible base body (1) and a high-temperature resistant protective layer (2); the high-temperature resistant protective layer (2) is a coating and is covered and fixed on the inner wall of the graphite crucible base body (1), so as to play a role in sealing the inner wall of the graphite crucible base body (1); the method is characterized in that: the graphite crucible base body (1) is a graphite homogeneous integrated piece; the high-temperature resistant protective layer (2) is a silicon carbide coating or a silicon nitride coating, or a graphite coating or a boron nitride coating; the graphite crucible base body (1) sequentially comprises a pot side section (1-1), a transition section (1-2) and a pot bottom (1-3) from top to bottom, wherein the thickness of the pot bottom (1-3) is larger than the wall thickness of the pot side section (1-1); the wall thickness of the upper part of the transition section (1-2) is the same as that of the lower part of the pot upper section (1-1), and the wall thickness of the lower part of the transition section (1-2) is the same as that of the upper part of the pot bottom (1-3); the bottom (1-3) of the pot is provided with a positioning mechanism (1-4) which is downward and is positioned in the center of the graphite crucible base body (1).

2. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 1, wherein: the thickness of the high-temperature resistant protective layer (2) is 1-40 micrometers.

3. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 2, wherein: the thickness of the high-temperature resistant protective layer (2) is 1-29 microns.

4. A self-contained graphite crucible for single crystal furnace crystal pulling as defined in claim 3, wherein: the thickness of the high-temperature resistant protective layer (2) is 3-10 micrometers.

5. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 1, wherein: the wall thickness of the pot side section (1-1) of the graphite crucible base body (1) is 12 to 25 mm; the thickness of the bottom (1-3) is 2 to 5 times of the wall thickness of the side section (1-1).

6. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 5, wherein: the wall thickness of the pot side section (1-1) of the graphite crucible base body (1) is 15 to 25 mm.

7. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 1, wherein: the outer diameter of the pot side section (1-1) of the graphite crucible base body (1) is 500-1050 mm, and the height-diameter ratio of the graphite crucible base body (1) is 0.6-0.8.

8. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 7, wherein: the positioning mechanism (1-4) of the bottom (1-3) of the pot is a cylindrical positioning boss (1-4-1) and an upper contact surface (1-4-2), the diameter of the positioning boss (1-4-1) is 150 to 300 mm, and the height is 5 to 20 mm; the upper side contact surface (1-4-2) is positioned above the positioning boss (1-4-1) and around the positioning boss (1-4-1), and the outer diameter of the upper side contact surface (1-4-2) is 1.5 to 2 times the diameter of the positioning boss (1-4-1).

9. The free standing graphite crucible for single crystal furnace crystal pulling as defined in claim 7, wherein: the positioning mechanism (1-4) of the bottom (1-3) of the pan is a cylindrical positioning groove (1-4-3) and a lower contact surface (1-4-4), the diameter of the positioning groove (1-4-3) is 150-300 mm, and the height is 5-20 mm; the lower side contact surface (1-4-4) is positioned below the positioning groove (1-4-3) and around the positioning groove (1-4-3), and the outer diameter of the lower side contact surface (1-4-4) is 1.5 to 2 times the diameter of the positioning groove (1-4-3).

10. The free standing graphite crucible for single crystal furnace crystal pulling according to one of claims 1 to 9, wherein: the high temperature resistant protective layer (2) is a graphite coating or a boron nitride coating.