Single crystal furnace thermal field capable of increasing crystal pulling rate

Abstract

The invention relates to the technical field of monocrystalline silicon, in particular to a single crystal furnace thermal field capable of increasing the crystal pulling rate. The single crystal furnace thermal field comprises an upper furnace body and a lower furnace body, an outer pipe body and an inner pipe body are arranged in the upper furnace body, an air cavity is formed between the outer pipe body and the inner pipe body, an air inlet is tangentially formed in one side of the top of the outer pipe body, an air outlet is formed in the upper portion of the top of the inner pipe body, and spiral blades are arranged on the outer side wall of the inner pipe body. A gap is formed between the spiral blade and the inner side wall of the outer pipe body, the inner pipe body is provided with a diameter expanding part and a diameter reducing part, the diameter expanding part and the diameter reducing part are arranged in a staggered mode, a flow guiding device is arranged below the inner pipe body, and the flow guiding device is arranged outside the spiral blade and comprises a straight barrel part and an inverted cone part; the diameter of the outer pipe body is gradually increased at the corresponding position of the upper end of the straight cylinder part and is matched with the sealing head to form a dust collection chamber. According to the invention, the control of temperature gradient is facilitated, the crystal pulling speed is increased, and the improvement of dust removal efficiency and the reduction of energy consumption are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon, and in particular to a single crystal furnace thermal field capable of improving the crystal pulling rate. Background Art

[0002] The temperature field of single crystal growth refers to the spatial distribution of temperature in the single crystal furnace, also known as the thermal field. During calcination, the temperature distribution in the thermal system is relatively stable, which is called the static thermal field. During the single crystal growth process, the thermal field will change, which is called the dynamic thermal field.

[0003] Crystals grow from the solid-liquid interface. When single crystal silicon grows, there are two forms, solid and melt, in the thermal field. There are also two temperature gradients, namely the longitudinal temperature gradient and radial temperature gradient in the crystal and the longitudinal temperature gradient and radial temperature gradient in the melt. These are two completely different temperature distributions, but the temperature gradient at the solid-liquid interface is the one that most affects the crystallization state.

[0004] The longitudinal temperature gradient at the crystallization interface is appropriately large to form the necessary supercooling so that the single crystal has sufficient growth momentum, but it cannot be too large, otherwise structural defects will occur, and the radial temperature gradient should be as small as possible to make the crystallization interface tend to be flat; the control of the longitudinal temperature gradient at the crystallization interface has an important influence on the crystallization rate. Traditionally, the temperature gradient is controlled at 10-30℃ / cm, but in order to ensure the quality of the product, it is often controlled not too high, which results in a reduction in the crystal pulling speed.

[0005] Therefore, the present invention optimizes the thermal field in the single crystal furnace to make the temperature gradient more accurately controlled. Thus, a higher crystal pulling speed can be achieved at a higher temperature gradient, thereby improving production efficiency. Summary of the invention

[0006] The purpose of the present invention is to provide a single crystal furnace thermal field that can improve the crystal pulling rate, so as to solve the problem that the temperature gradient control of the existing single crystal furnace is difficult, which affects the crystal pulling speed.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a single crystal furnace thermal field capable of improving the crystal pulling rate, comprising an upper furnace body and a lower furnace body, wherein the upper furnace body comprises an outer tube body, a sealing head is arranged below the outer tube body, and the sealing head is detachably matched with the lower furnace body in a sealed manner, characterized in that: the upper furnace body also comprises an inner tube body, and an air cavity is formed between the inner tube body and the outer tube body;

[0008] An air inlet is tangentially arranged on one side of the top of the outer tube body, the air inlet is connected to the wind cavity, and an air outlet is arranged on the top of the upper furnace body, the air outlet is connected to the inner tube body;

[0009] The inert gas enters the wind cavity from the air inlet, and the flow rate of the inert gas in the wind cavity is staggered at fast and slow speeds. A vent hole is arranged on the side wall of the inner tube body at a faster flow rate, and the inner tube body is connected to the wind cavity through the vent hole;

[0010] A flow guide device is arranged below the inner tube body, which is sealed and connected to the head. The diameter of the outer tube body gradually increases at a position corresponding to the upper end of the flow guide device and is connected to the head. A dust collecting chamber is formed by the outer tube body, the head and the flow guide device.

[0011] Furthermore, spiral blades are arranged on the outer wall of the inner tube body, the diameter and spacing of the spiral blades remain unchanged and are arranged from top to bottom, and a gap is formed between the spiral blades and the inner wall of the outer tube body; the inner tube body includes an expanding diameter portion and a reducing diameter portion, the expanding diameter portion and the reducing diameter portion are arranged alternately, and the vent holes are arranged on the expanding diameter portion.

[0012] Furthermore, the guide device is wrapped around the spiral blades arranged on the outer wall of the end of the inner tube body, and the guide device includes a straight tube part and an inverted cone section. The lower end of the inner tube body is located in the straight tube part, and there is no expanded diameter part in the straight tube part.

[0013] Furthermore, a dust door is provided on one side of the dust collecting chamber, and the dust door is sealed with the dust collecting chamber.

[0014] Furthermore, the gas outlet is connected to a dust collector, and the inert gas is discharged from the gas outlet and exchanges heat with the intake air, and then returns to the gas inlet for recycling after being dusted by the dust collector.

[0015] Furthermore, a seed crystal pulling head is arranged above the upper furnace body, and the seed crystal pulling head pulls the crystal rod to grow upward in the inner tube body.

[0016] Furthermore, one side of the upper furnace body is connected to the cover opening mechanism, a furnace is provided in the furnace body, a crucible support is in the furnace, the crucible support is rotatably sealed and connected to the lower furnace body; the bottom of the crucible support is connected to the crucible lifting and rotating mechanism.

[0017] Furthermore, a crucible tray is arranged on the crucible support, a graphite crucible is arranged on the crucible tray, a quartz crucible is placed in the graphite crucible, a heater is arranged on the outer periphery of the graphite crucible, and an insulation layer is arranged on the inner side wall of the lower furnace body and the head.

[0018] Furthermore, the sealing head is provided with a feed port and an observation port.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention sets a wind cavity and arranges the flow rate of the inert gas flow in the wind cavity in a staggered manner, so that during the flow of the air, a part of the high-temperature airflow returning from the inner tube body can be pulled into the wind cavity, thereby heating the inert gas entering. The temperature gradient is more easily controlled during the process, so that a larger temperature gradient can be controlled, thereby obtaining a larger pulling speed;

[0021] 2. In the process of airflow backflow in the inner tube body, the present invention can separate the dust in the backflow airflow and collect it in the dust collecting chamber through the effect of rotary centrifugation. On the one hand, the dust removal efficiency is improved, and on the other hand, the processing load of the rear dust removal equipment is reduced. The backflow of airflow and the removal of dust play a positive role in reducing the energy consumption of the system.

[0022] 3. The present invention uses a flow guide device to make the airflow have a higher speed after passing through the flow guide device. The airflow diffuses at a higher speed and can entrain the dust generated in the furnace. At the same time, since the airflow is discharged upward through the inner tube body, the action range of the inert gas is more concentrated. On the one hand, unnecessary energy loss is reduced. On the other hand, it is equivalent to isolating the crystal rod from the internal space of the furnace, making the growth environment of the crystal rod more stable, and also helping to improve the speed and quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of a single crystal furnace of the present invention;

[0024] Figure 2 The present invention Figure 1 A partial enlarged schematic diagram of part A;

[0025] Figure 3 It is a schematic structural diagram of the inner tube body in the upper furnace body of the present invention;

[0026] Figure 4 It is a schematic diagram of the principle of the flow state of the airflow in the air cavity of the present invention;

[0027] Figure 5 It is a schematic cross-sectional structure diagram of the connection between the lower furnace body and the upper furnace body of the present invention;

[0028] Figure 6 The present invention Figure 4 Schematic diagram of the cross-sectional structure of part B.

[0029] The names corresponding to the marks in the figure are:

[0030] 1. Lower furnace body; 11. Furnace chamber; 12. Crucible support; 13. Crucible tray; 14. Graphite crucible; 15. Quartz crucible; 16. Heater; 17. Insulation layer; 2. Upper furnace body; 21. Air inlet; 22. Air outlet; 23. Connection part of cover opening mechanism; 24. Sealing head; 241. Feeding port; 242. Observation port; 25. Outer tube body; 26. Inner tube body; 261. Reduced diameter part; 262. Expanded diameter part; 2621. Vent; 27. Spiral blade; 28. Flow guide device; 281. Straight tube part; 282. Inverted cone part; 3. Seed crystal lifting head; 4. Dust collecting chamber; 41. Ash door; 5. Wind cavity; 51. Wind duct; 52. Gap; 6. Crystal rod. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0032] like Figure 1-6 As shown, the thermal field of the single crystal furnace of the present invention includes an upper furnace body 2 and a lower furnace body 1. The lower furnace body 1 includes a furnace chamber 11. A crucible support 12 is arranged in the furnace chamber 11. The bottom of the crucible support 12 is connected to a crucible lifting and rotating mechanism. The crucible lifting and rotating mechanism is movably sealed to the furnace chamber 11. A crucible tray 13 is arranged above the crucible support 12, and a graphite crucible 14 is arranged on the crucible tray 13. At the same time, a quartz crucible 15 is placed in the graphite crucible 14.

[0033] A heater 16 is arranged on the outer periphery of the graphite crucible 14. In the present embodiment, the heater 16 is a graphite heater 16 with an upper limit of the heating temperature of about 1500°C. Both sides of the heater 16 are electrodes fixed in the lower furnace body 1. An insulation layer 17 is arranged on the periphery of the furnace chamber 11.

[0034] The upper furnace body 2 includes an outer tube body 25, an inner tube body 26 and a head 24, wherein the outer tube body 25 is connected to the head 24, a feed port 241 and an observation port 242 are arranged on the head 24, a wind cavity 5 is formed between the outer tube body 25 and the inner tube body 26, an air inlet 21 is arranged above the outer tube body 25, and the air inlet 21 is connected to the wind cavity 5, and an air outlet 22 is arranged above the outer tube body 25, and the air outlet 22 is connected to the inside of the inner tube body 26; a spiral blade 27 is arranged on the inner tube body 26, and the pitch of the spiral blade 27 and The diameter remains unchanged, an air duct 51 is formed between the inner tube body 26 and the outer tube body 25, and a gap 52 is formed between the spiral blades 27 and the outer tube body 25; at the same time, the inner tube body 26 is a reducer, including an enlarged diameter portion 262 and a reduced diameter portion 261, the enlarged diameter portion 262 and the reduced diameter portion 261 are arranged alternately on the inner tube body 26, and the enlarged diameter portion 262 and the reduced diameter portion 261 are both located between the spiral blades 27, and a vent 2621 is provided on the enlarged diameter portion 262, and the vent 2621 connects the ventilation cavity 5 and the inside of the inner tube body 26; the specific implementation method is as follows Figure 4 As shown, during the spiral movement of the gas, in the direction of the airflow, the diameter of the inner tube body 26 first gradually increases and then gradually decreases and is alternately arranged. It should be noted that in the accompanying drawings of the present invention, a reduced diameter portion 261 and an expanded diameter portion 262 are alternately arranged. According to actual production needs, multiple reduced diameter portions 261 and one expanded diameter portion 262 may also be alternately arranged.

[0035] A seed crystal pulling head 3 is arranged above the outer tube body 25, and a cover opening mechanism connecting part 23 is arranged on one side above the outer tube body 25. The cover opening mechanism connecting part 23 is connected to the cover opening mechanism, and is used for transferring and removing the crystal rod 6 after the crystal pulling is completed; at the contact point between the outer tube body 25 and the head 24, the diameter of the outer tube body 25 gradually increases and is fixedly connected to the head 24, and a guide device 28 is arranged on the inner tube body 26 at a position where the diameter of the lower end of the outer tube body 25 begins to increase. The guide device 28 includes a straight tube portion 281, and the spiral blade 27 is included in the straight tube portion 281. The straight tube portion 281 and the head 24 are sealed and fixedly connected, and a dust collecting chamber 4 is formed between the straight tube portion 281 and the expanded diameter section at the lower end of the inner tube body 26, and an ash door 41 is arranged on the dust collecting chamber 4.

[0036] The guide device 28 also includes an inverted cone portion 282, which is connected to the straight tube portion 281. The inner tube body 26 is not provided with an expanded diameter portion 262 inside the guide device 28. The crystal rod 6 grown on the melt surface of the quartz crucible 15 is pulled into the inner tube body 26 by the crystal rod 6 pulling head. The inert circulating gas (argon gas) in the single crystal furnace is disturbed in the furnace chamber 11, entrained with dust, passes through the inner tube body 26, and is then discharged through the gas outlet 22.

[0037] The principle of the present invention is:

[0038] During use of the present invention, high-purity polysilicon (99.9999%) is placed into the quartz crucible 15 through the feed port 241, and then vacuumed and inert gas (argon) is introduced. At this time, the heater 16 is started to heat and melt the polysilicon, and the heating temperature during the process is about 1420°C.

[0039] When the polysilicon is completely melted, the seed crystal is lowered to the surface of the melt through a pulling head and seeded. During the process, the temperature gradient is controlled (10-30°C / cm). The molten liquid begins to crystallize at the end of the seed crystal. The rotation speed of the seed crystal and the melt is controlled (in the opposite direction, the rotation speed is 5-20rpm). The pulling speed is controlled to shrink the neck, and then the pulling speed is reduced and the shoulder is released to the required diameter, and then the diameter is equalized and the end is completed.

[0040] In the present invention, during the growth of the crystal rod 6, since the inert gas is introduced from the top and rotates downward, and also passes through the expansion part 262 and the reduction part 261, during the operation of the equipment, when passing through the expansion part 262, the cross-sectional area of ​​the gas flow decreases, so the gas flow rate increases and the pressure decreases, thereby partially pulling the high-temperature gas in the inner tube body 26 back into the wind cavity 5. On the one hand, the dust entrained in the high-temperature gas in the inner tube body 26 can be separated (the dust is thrown onto the inner wall of the outer tube body 25 under the action of centrifugal force, and then falls into the dust collecting chamber 4). On the other hand, the high-temperature gas is mixed with the intake air and can also heat the inert gas. The process is beneficial to reducing energy consumption and controlling the temperature gradient, and also plays a positive role in increasing the speed of crystal pulling.

[0041] The heated gas passes through the guide device 28 and then ejected from the inverted cone 282 of the guide device 28. During the process, the inverted cone 282 is reduced in diameter, thereby increasing the flow rate of the gas. When the gas flow is ejected from the inverted cone 282, it diffuses outward due to its own centrifugal force. During the process, the dust (SiO) generated under high temperature conditions can be cleaned. At the same time, the inert gas is discharged through the inner tube body 26 via the surface of the crystal rod 6, which is equivalent to isolating the crystal rod 6 from other spaces in the furnace 11, thereby helping to ensure the quality of the product. In addition, since the gas is heated, it helps to control the temperature gradient. Under a stable temperature gradient, a more efficient crystal pulling process can be achieved.

[0042] During the process of the gas flow being discharged through the inner tube body 26, a part of the gas is drawn into the wind cavity 5, and the other part of the gas is discharged to exchange heat with the intake air to preheat the intake air, and then recycled after being processed by the dust removal device. In the process, part of the dust is removed, which helps to reduce the energy consumption of the rear-end dust removal device, is more energy-saving and convenient for use in production.

[0043] After the crystal pulling is completed, the cover opening mechanism lifts the sealing head 24 and rotates it to one side, so that the manufactured crystal rod 6 can be lowered and transported through the seed crystal pulling head 3, thereby realizing the entire production process. The cover opening mechanism, pulling head and crucible lifting and rotating mechanism involved in the process are existing mature technical solutions. The present invention does not make any improvements on this and will not be described in detail. In addition, although the conventional settings in existing single crystal furnaces such as water-cooled screens are not elaborated in the present invention, the conventional settings based on this by those skilled in the art should belong to the protection scope of the present invention.

[0044] Example 1

[0045] In this embodiment, a conventional single crystal furnace is used for comparison with the single crystal furnace of the present invention.

[0046] The single crystal furnace has a furnace diameter of 1000mm and is used to prepare crystal rods with a diameter of 300mm. The crystal pulling speed of a traditional single crystal furnace is 1.5mm / min.

[0047] In this embodiment, the diameter of the expanded portion of the inner tube body is 500mm, the diameter of the reduced portion is 350mm, the pitch of the spiral blade is 100mm, the outlet diameter of the inverted cone is 200mm, the flow rate of argon gas is controlled to be 60-80L / min, the inlet temperature is controlled at 300°C, and the inner tube body is evenly divided into three sections, namely, upper, middle and lower sections. The opening rates of the vent holes relative to the expanded portion in the upper, middle and lower sections are 18% (aperture 6mm), 12% (aperture 4mm) and 7% (aperture 2.5mm), respectively. According to measurement, the wind speed in the wind cavity is 2-4m / s, the wind speed at the outlet of the guide device is 10-15m / s, and the outlet temperature is 800-900°C.

[0048] During operation, the heater temperature is controlled at 1420-1450°C, the seed crystal rotation speed is 15-20rpm (counterclockwise), and the crucible rotation speed is 10-15rpm. According to measurement, the longitudinal temperature gradient at the crystallization interface can be stably controlled at 20-25°C / cm, the gradient fluctuation is less than ±2°C / cm, the radial temperature difference is <3°C, the crystal pulling speed can reach 2.5mm / min, the oxygen content of the crystal rod is <15ppma, and the crystal pulling efficiency is improved by more than 60%.

[0049] During the operation of the present invention, effective dust removal is achieved, and good energy-saving effect is achieved, wherein the removal rate of SiO dust reaches more than 90%, while reducing the system energy consumption by more than 20%, bringing a significant promotion effect to industrial production.

[0050] The present invention is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, all technical solutions that are the same or similar to those of the present application fall within the protection scope of the present invention.

Claims

1. A single crystal furnace thermal field capable of improving the crystal pulling rate, comprising an upper furnace body (2) and a lower furnace body (1), wherein the upper furnace body (2) comprises an outer tube body (25), a sealing head (24) is arranged below the outer tube body (25), and the sealing head (24) is detachably matched with the lower furnace body (1), characterized in that: The upper furnace body (2) further comprises an inner tube body (26), and an air cavity (5) is formed between the inner tube body (26) and the outer tube body (25); An air inlet (21) is tangentially arranged on one side of the top of the outer tube body (25), the air inlet (21) is connected to the wind cavity (5), and an air outlet (22) is arranged on the top of the upper furnace body (2), the air outlet (22) is connected to the inner tube body (26); The inert gas enters the wind chamber (5) through the air inlet (21), and the flow speed of the inert gas in the wind chamber (5) is arranged in a staggered manner, and a vent hole (2621) is arranged on the side wall of the inner tube body (26) when the flow speed is faster, and the inner tube body (26) is connected to the wind chamber (5) through the vent hole (2621); A flow guide device (28) is provided below the inner tube body (26), the flow guide device (28) is sealedly connected to the sealing head (24), the outer tube body (25) gradually increases in diameter at a position corresponding to the upper end of the flow guide device (28) and is connected to the sealing head (24), and a dust collecting chamber (4) is formed by the outer tube body (25), the sealing head (24) and the flow guide device (28).

2. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 1, characterized in that: The outer wall of the inner tube body (26) is provided with spiral blades (27), the diameter and spacing of the spiral blades (27) remain unchanged and are arranged from top to bottom, and a gap (52) is formed between the spiral blades (27) and the inner wall of the outer tube body (25); the inner tube body (26) includes an expanded diameter portion (262) and a reduced diameter portion (261), the expanded diameter portion (262) and the reduced diameter portion (261) are arranged alternately, and the vent hole (2621) is arranged on the expanded diameter portion (262).

3. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 2, characterized in that: The flow guide device (28) is wrapped around the spiral blade (27) arranged on the outer side wall of the end of the inner tube body (26), and the flow guide device (28) includes a straight tube portion (281) and an inverted cone portion (282). The lower end of the inner tube body (26) is located in the straight tube portion (281), and there is no expanded diameter portion (262) in the straight tube portion (281).

4. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 1, characterized in that: A dust door (41) is provided on one side of the dust collecting chamber (4), and the dust door (41) and the dust collecting chamber (4) are sealed.

5. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 1, characterized in that: The gas outlet (22) is connected to a dust collector. The inert gas is discharged from the gas outlet (22) and then exchanges heat with the intake air. After being dusted by the dust collector, the inert gas returns to the gas inlet (21) for recycling.

6. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 1, characterized in that: A seed crystal pulling head (3) is arranged above the upper furnace body (2), and the seed crystal pulling head (3) pulls the crystal rod (6) to grow upward in the inner tube body (26).

7. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 1, characterized in that: One side of the upper furnace body (2) is connected to a cover opening mechanism, a furnace chamber (11) is arranged in the furnace body, a crucible support (12) is arranged in the furnace chamber (11), and the crucible support (12) is rotatably and hermetically connected to the lower furnace body (1); the bottom of the crucible support (12) is connected to a crucible lifting and rotating mechanism.

8. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 7, characterized in that: The crucible support (12) is provided with a crucible tray (13), a graphite crucible (14) is provided on the crucible tray (13), a quartz crucible (15) is placed in the graphite crucible (14), a heater (16) is provided on the outer periphery of the graphite crucible (14), and a heat-insulating layer (17) is provided on the inner side walls of the lower furnace body (1) and the sealing head (24).

9. The single crystal furnace thermal field capable of improving the crystal pulling rate according to claim 1, characterized in that: The sealing head (24) is provided with a feed port (241) and an observation port (242).

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