A polycrystalline silicon ingot casting furnace

Abstract

The present invention discloses a polysilicon ingot furnace, comprising a furnace body and a heat preservation cover arranged in the furnace body, wherein a crucible, a bottom plate, a heater, a heat insulation block and a heat exchange device are arranged in the heat preservation cover; the bottom plate is installed on the heat exchange device, the crucible is placed on the bottom plate, a crucible guard plate is installed on the outer wall of the crucible, an angle adjustment mechanism is installed on the side wall of the bottom plate, the heat insulation block is installed on the angle adjustment mechanism, and the end of the heat insulation block is in contact with the heat preservation cover. The present invention can effectively control the heat dissipation path and method by changing the placement of the carbon felt heat insulation block, that is, adjusting the angle between it and the bottom graphite guard plate, and realizing the regulation of the thermal field to meet the different requirements of various ingot casting processes.

Description

Technical Field

[0001] The invention relates to the technical field of solar photovoltaic industry, and in particular to a polysilicon ingot casting furnace. Background Art

[0002] Directional solidification is the mainstream technology for preparing solar crystalline silicon in the photovoltaic industry. In the ingot furnace, graphite heaters set on the five sides of the top side are usually used as the heating system. The side insulation cages surrounding the side heaters are raised and lowered to dissipate heat from the silicon material in the crucible to the directional heat dissipation blocks, graphite support columns, furnace shell and other components through heat conduction or radiation, so that a specific temperature gradient is formed in the crucible, and the silicon material grows directionally from bottom to top. In order to reduce the dislocation density of silicon ingots and improve the quality of silicon ingots, various new ingot casting technologies are constantly emerging, such as full-melt high-efficiency ingot casting process and semi-melt high-efficiency ingot casting process.

[0003] Regardless of the ingot casting method, the thermal field is the decisive factor affecting the crystal quality during the directional solidification process. In the current ingot casting process, it is difficult to accurately adjust and locally control the thermal field only by raising and lowering the side insulation cage. Therefore, in order to optimize the thermal field, a fixed-position insulation block is added below the side heater and outside the bottom graphite guard plate. This measure can maintain the flatness of the solid-liquid interface and reduce power consumption. However, different ingot casting processes have different requirements for insulation blocks. Ingot casting furnaces equipped with fixed-position insulation blocks will be subject to process limitations. Therefore, fixed insulation blocks are difficult to meet the needs of existing ingot casting processes. Summary of the invention

[0004] The purpose of the present invention is to provide a polysilicon ingot casting furnace to solve the problems existing in the above-mentioned prior art. The placement of the insulation blocks equipped therein can be adjusted to match various process requirements and improve the controllability of the thermal field.

[0005] To achieve the above-mentioned purpose, the present invention provides the following scheme: The present invention provides a polycrystalline silicon ingot casting furnace, comprising a furnace body and a heat-insulating cover arranged in the furnace body, wherein a crucible, a bottom plate, a heater, an insulation block and a heat exchange device are arranged in the heat-insulating cover; the bottom plate is installed on the heat exchange device, the crucible is placed on the bottom plate, a crucible guard plate is installed on the outer wall of the crucible, an angle adjustment mechanism is installed on the side wall of the bottom plate, the insulation block is installed on the angle adjustment mechanism, and the end of the insulation block is in contact with and connected to the heat-insulating cover.

[0006] Preferably, the angle adjustment mechanism is a hinge, which includes a first hinge fixedly connected to the base plate and a second hinge fixedly connected to the insulation block, the first hinge and the second hinge are hinged; a support rod is hinged on the first hinge, a slot is fixedly installed on the second hinge, a slider is slidably connected in the slot, and the support rod and the slider are hinged; a micro electric push rod is fixedly installed at one end of the slot, and the movable end of the micro electric push rod is fixedly connected to the slider.

[0007] Preferably, the heat-insulating cover comprises a heat-insulating cover body, an upper heat-insulating plate and a lower heat-insulating plate, and the upper heat-insulating plate and the lower heat-insulating plate are both openably connected to the cover body; and the heat-insulating block is in contact with and connected to the cover body.

[0008] Preferably, the heater comprises a top heater and a side heater, the top heater is arranged above the crucible, the side heater is arranged on the outside of the crucible guard plate, and the insulation block is located below the side heater.

[0009] Preferably, the heat exchange device comprises a heat sink block and a furnace shell water-cooled wall, the bottom plate is fixedly connected to the heat sink block, and the furnace shell water-cooled wall is fixedly connected to the cover body.

[0010] Preferably, the crucible is a quartz crucible, the bottom plate is a graphite bottom plate, the insulation block is carbon felt, and the crucible guard plate is a graphite guard plate.

[0011] Preferably, the insulation block has a length of 1000 mm, a width of 65 mm and a thickness of 20 mm.

[0012] The present invention discloses the following technical effects: By changing the placement of the carbon felt insulation block, that is, adjusting the angle between it and the bottom graphite guard plate, the present invention can effectively control the heat dissipation path and method, realize the regulation of the thermal field, and meet the different requirements of each ingot casting process. Compared with the prior art, on the one hand, when the insulation block is placed vertically, that is, kept vertically with the bottom graphite guard plate, the insulation plate is close to the bottom of the quartz crucible, which can block part of the heat from the heater and avoid overheating and melting of the seed crystal. On the other hand, when the carbon felt insulation block is placed horizontally, that is, kept parallel to the bottom graphite guard plate, the ingot casting furnace can be divided into a hot zone and a cold zone, the heater is located in the hot zone, and the area where the water-cooled wall below the furnace is located is the cold zone. At this time, the insulation block cuts off the radiation heat dissipation between the hot zone and the cold zone, which helps to reduce unnecessary heat loss and reduce the energy consumption of the ingot casting process. At the same time, it helps to achieve the insulation of the side wall of the crucible and reduce the possibility of crystallization of the side wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0014] Figure 1 This is a schematic diagram of the structure of the polysilicon ingot casting furnace of the present invention.

[0015] Figure 2 A schematic diagram of the layout structure of a heat insulation block provided in an embodiment of the present invention.

[0016] Figure 3 is a structural schematic diagram of the angle adjustment mechanism;

[0017] Among them, 1-top heater, 2-side heater, 3-crucible, 4-bottom plate, 5-insulation block, 6-furnace body, 7-crucible guard plate, 8-insulation cover, 9-upper insulation board, 10-lower insulation board, 11-heat sink block, 12-furnace shell water-cooled wall, 13-hinge, 14-first hinge, 15-second hinge, 16-support rod, 17-slot, 18-slider, 19-micro electric push rod, 20-rotating shaft. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] The present invention provides a polysilicon ingot furnace, comprising a furnace body 6 and a heat-insulating cover arranged in the furnace body 6, wherein a crucible 3, a bottom plate 4, a heater, a heat-insulating block 5 and a heat exchange device are arranged in the heat-insulating cover; the bottom plate 4 is installed on the heat-exchanging device, the crucible 3 is placed on the bottom plate 4, a crucible guard plate 7 is installed on the outer wall of the crucible 3, an angle adjustment mechanism is installed on the side wall of the bottom plate 4, the heat-insulating block 5 is installed on the angle adjustment mechanism, and the end of the heat-insulating block 5 is in contact with and connected to the heat-insulating cover; the angle adjustment mechanism is a hinge 13, The hinge 13 includes a first hinge 14 fixedly connected to the base plate 4 and a second hinge 15 fixedly connected to the insulation block 5, the first hinge 14 and the second hinge 15 are hinged via a rotating shaft 20; a support rod 16 is hinged on the first hinge 14, a card slot 17 is fixedly installed on the second hinge 15, a slider 18 is slidably connected in the card slot 17, and the support rod 16 and the slider 18 are hinged; a micro electric push rod 19 is fixedly installed at one end of the card slot 17, and the movable end of the micro electric push rod 19 is fixedly connected to the slider 18. The position of the slider 18 in the slot is adjusted by the micro-electric push rod 19, so as to realize the angle adjustment of the insulation block 5. When the slider 18 is located at the bottom of the slot 17, the support rod 16 and the rotating shaft 20 are in a vertical state. At this time, the first hinge 14 and the second hinge 15 are in a horizontal state, and the insulation block 5 is placed horizontally; when the slider 18 is located at the top of the slot 17, the support rod 16 and the rotating shaft 20 are in a non-vertical state. At this time, the first hinge 14 and the second hinge 15 are in a vertical state, and the insulation block 5 is placed vertically. The insulation cover comprises an insulation cover body 8, an upper insulation plate 9 and a lower insulation plate 10, and the upper insulation plate 9 and the lower insulation plate 10 are both connected to the cover body in an openable and closable manner; the insulation block 5 is in contact with the cover body; the heater is used to form a temperature field, and the heater comprises a top heater 1 and a side heater 2, the top heater 1 is arranged above the crucible 3, the side heater 2 is arranged on the outer side of the crucible guard plate 7, and the insulation block 5 is located below the side heater 2; the heat exchange device comprises a heat dissipation block 11 and a furnace shell water-cooled wall 12, the bottom plate 4 is fixedly connected to the heat dissipation block 11, and the furnace shell water-cooled wall 12 is fixedly connected to the cover body; the crucible 3 is a quartz crucible, and in order to prevent the quartz crucible from softening at high temperature, the bottom plate 4 is a graphite bottom plate, the insulation block 5 is a carbon felt, and the crucible guard plate 7 is a graphite guard plate; the insulation block 5 has a length of 1000 mm, a width of 65 mm, and a thickness of 20 mm.

[0021] Specifically, the placement angle of the heat insulation block 5 can be adjusted according to the actual thermal field conditions and different requirements for heat dissipation and heat preservation during the ingot casting process. Figure 1 FIG. 4 shows the situation when the heat insulation block 5 is placed horizontally, that is, the first hinge 14 and the second hinge 15 are in a horizontal state. Figure 2The figure shows the situation when the heat insulating block 5 is placed vertically, that is, the first hinge 14 and the second hinge 15 are in a vertical state, which does not represent the fixed setting position of the heat insulating block 5.

[0022] In the process of high-performance polysilicon ingot casting, the silicon material in the quartz crucible undergoes heating, melting, crystal growth, annealing and cooling processes in sequence. During the heating process, the temperature in the furnace rises rapidly under the action of the heater. When the temperature of the silicon material rises to the melting point, the top heater 1 and the side heater 2 continue to heat to 1500°C and keep warm for a period of time, entering the melting stage. In different processes, the order and degree of melting of silicon materials are different. At this time, the insulation block 5 with adjustable placement angle will effectively help the thermal field in the ingot furnace adapt to the needs of various processes.

[0023] Embodiment 1:

[0024] In the semi-melting high-efficiency multi-crystalline ingot casting process, the crystalline silicon fragments are laid on the bottom of the quartz crucible as seed crystals during the charging process. During the melting stage, the silicon material cannot be completely melted, and a seed crystal retention layer of a certain height needs to be ensured at the bottom. Therefore, the first implementation scheme of the heat insulation block 5 is as follows: during the heating stage, the furnace temperature needs to be increased rapidly, the first hinge 14 and the second hinge 15 are in a horizontal state, and the heat insulation block 5 is placed horizontally, such as Figure 1 As shown. The ingot furnace is divided into two areas, upper and lower. The area above the insulation block 5, including the top heater 1 and the side heater 2, is the hot zone, and the area below the insulation block 5, including the directional heat dissipation block 11 and the furnace shell water-cooled wall 12, is the cold zone. Since the thermal conductivity of the carbon felt material is very small, it can effectively cut off the radiation heat dissipation channel of the upper and lower furnace bodies 6, avoid unnecessary heat loss, and reduce power consumption in the heating stage.

[0025] The heater continues to work, the furnace temperature continues to rise, and the melting stage is entered. Considering the problem of seed crystal retention, the silicon material should be melted from top to bottom, that is, the temperature of the upper part of the crucible 3 is higher and the temperature of the bottom is lower. Especially at the end of the melting, it is necessary to avoid excessive heat from the side heater 2 radiating to the bottom of the side wall of the quartz crucible, causing the seed crystal to melt completely. Therefore, the insulation block 5 is kept vertically placed at the end of the melting and the beginning of the crystal growth, and the first hinge 14 and the second hinge 15 are in a vertical state, such as Figure 2 The heat insulating block 5 is close to the bottom of the side wall of the quartz crucible, which can effectively isolate the heat from the heater and protect the seed crystal.

[0026] As crystal growth begins, the solid-liquid crystal growth interface should be kept as straight as possible. However, due to structural problems in the ingot casting furnace, the side wall of the quartz crucible dissipates more heat than the center, and the molten silicon near the wall of the quartz crucible is more likely to crystallize. Therefore, the insulation block 5 should be returned to a horizontal position again, and the first hinge 14 and the second hinge 15 should be restored to a horizontal state again to reduce the radiation heat dissipation between the side wall of the quartz crucible and the water-cooled wall to avoid side wall crystallization. Figure 1 shown.

[0027] Embodiment 2:

[0028] In the process of fully melted high-efficiency polycrystalline ingot casting, amorphous silicon / silicon-containing materials are fixed to the bottom of the quartz crucible to form a nucleation layer with a rough surface. After all the silicon materials are melted, the erosion time and intensity of the silicon melt on the nucleation layer are controlled. During crystal growth, it is necessary to control the degree of supercooling to grow high-quality polycrystalline silicon ingots. Therefore, the second implementation scheme of the insulation block 5 is as follows: During the heating stage, the furnace temperature needs to be increased rapidly, the insulation block 5 is placed horizontally, and the first hinge 14 and the second hinge 15 are in a horizontal state, such as Figure 1 As shown. The ingot furnace is divided into two areas, upper and lower. The area above the insulation block 5, including the top heater 1 and the side heater 2, is the hot zone, and the area below the insulation block 5, including the directional heat dissipation block 11 and the furnace shell water-cooled wall 12, is the cold zone. Since the thermal conductivity of the carbon felt material is very small, it can effectively cut off the radiation heat dissipation channel of the upper and lower furnace bodies 6, avoid unnecessary heat loss, and reduce power consumption in the heating stage.

[0029] The heater continues to work, the furnace temperature continues to rise, and the melting stage is entered. The full melting process does not need to consider the seed crystal retention problem. Before the silicon material is completely melted, the insulation block 5 is always kept horizontally placed, and the first hinge 14 and the second hinge 15 are in a horizontal state. Figure 1 shown.

[0030] In the early stage of crystal growth, nucleation needs to have a suitable range of undercooling, and the focus of the full melt process is to control the temperature within a suitable range. The insulation block 5 can be opened to a certain angle to match the process requirements for heat dissipation and heat preservation.

[0031] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0032] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A polycrystalline silicon ingot casting furnace, comprising a furnace body (6) and a heat preservation cover arranged in the furnace body (6), characterized in that: The heat-insulating cover is provided with a crucible (3), a bottom plate (4), a heater, a heat-insulating block (5) and a heat-exchanging device; the bottom plate (4) is mounted on the heat-exchanging device, the crucible (3) is placed on the bottom plate (4), a crucible guard plate (7) is mounted on the outer wall of the crucible (3), an angle adjustment mechanism is mounted on the side wall of the bottom plate (4), the heat-insulating block (5) is mounted on the angle adjustment mechanism, and the end of the heat-insulating block (5) is in contact with and connected to the heat-insulating cover; The angle adjustment mechanism is a hinge (13), the hinge (13) comprising a first hinge (14) fixedly connected to the base plate (4) and a second hinge (15) fixedly connected to the heat insulation block (5), the first hinge (14) and the second hinge (15) being hinged; a support rod (16) being hingedly connected to the first hinge (14), a slot (17) being fixedly mounted on the second hinge (15), a slider (18) being slidably connected in the slot (17), the support rod (16) and the slider (18) being hingedly connected; a micro electric push rod (19) being fixedly mounted at one end of the slot (17), the movable end of the micro electric push rod (19) being fixedly connected to the slider (18); The heat-insulating cover comprises a heat-insulating cover body (8), an upper heat-insulating plate (9) and a lower heat-insulating plate (10), wherein the upper heat-insulating plate (9) and the lower heat-insulating plate (10) are both openably connected to the cover body; the heat-insulating block (5) is in contact with and connected to the cover body; The heater comprises a top heater (1) and a side heater (2), wherein the top heater (1) is arranged above the crucible (3), the side heater (2) is arranged outside the crucible guard plate (7), and the heat insulation block (5) is located below the side heater (2).

2. The polycrystalline silicon ingot casting furnace according to claim 1, characterized in that: The heat exchange device comprises a heat sink block (11) and a furnace shell water-cooled wall (12); the bottom plate (4) is fixedly connected to the heat sink block (11); and the furnace shell water-cooled wall (12) is fixedly connected to the cover body.

3. The polycrystalline silicon ingot casting furnace according to claim 1, characterized in that: The crucible (3) is a quartz crucible, the bottom plate (4) is a graphite bottom plate, the heat insulation block (5) is carbon felt, and the crucible guard plate (7) is a graphite guard plate.

4. The polycrystalline silicon ingot casting furnace according to claim 1, characterized in that: The heat insulation block (5) has a length of 1000 mm, a width of 65 mm and a thickness of 20 mm.

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