Oxygen reduction type graphite heater

Abstract

The utility model discloses an oxygen reduction type graphite heater, which is characterized in that a heating part comprises first U-shaped heating petals and second U-shaped heating petals, the first U-shaped heating petals and the second U-shaped heating petals are sequentially connected end to end, so that two adjacent groups of the first U-shaped heating petals and the second U-shaped heating petals are electrified and connected in series, and an annular structure is integrally enclosed; the first U-shaped heating valve is integrally positioned above the liquid level of the monocrystalline silicon, and the second U-shaped heating valve is integrally positioned below the liquid level of the monocrystalline silicon; the radial cross section area of the first U-shaped heating section is smaller than that of the second U-shaped heating section; the supporting leg pieces are symmetrically arranged on the lower portion of the heating part and extend downwards. The device can ensure that the high-temperature heating range of the upper part of the melt is reduced as much as possible, sufficient heat is provided, the temperature gradient of a solid-liquid crystallization surface is ensured, the heat productivity of the lower part is less, and the heat is gradually dispersed from top to bottom, so that the heat convection of the melt can be reduced, the scouring of the silicon melt to the wall of the quartz crucible is weakened, and the secondary crystallization of the melt is avoided.

Description

TECHNICAL FIELD

[0001] The utility model belongs to single crystal manufacturing equipment technical field, concretely relates to a kind of graphite heater of oxygen reduction type. BACKGROUND

[0002] Graphite heater is the core component of the heat field of Czochralski silicon furnace, and the existing heater is cylindrical in shape. The cylinder is slotted axially at both ends to cut the cylinder into several to tens of petals to control the current direction, and the current direction of any two adjacent petals is opposite. Then, the electrode leg is energized to heat.

[0003] The polycrystalline silicon in the quartz crucible is heated and melted in the single crystal furnace, and a stable temperature gradient is maintained. Then, the seed crystal is immersed in the melt. The silicon atoms in the melt will form regular crystals on the solid-liquid crystallization surface along the silicon atom arrangement structure of the seed crystal, becoming a single crystal. The seed crystal is slightly rotated and lifted upward. The silicon atoms in the melt will continue to crystallize on the single crystal formed in front, continuing the regular atomic arrangement structure. If the entire crystallization environment is stable, crystallization can be formed repeatedly, and finally a cylindrical silicon single crystal with regular atomic arrangement is formed.

[0004] Large-size heat field is generally a double-heating system. In addition to the main heater located on the side of the crucible, there is also a bottom heater located at the bottom of the crucible. During the material melting stage, both heaters heat simultaneously, the heating is uniform, and the temperature rises quickly. After the material melting is completed, the bottom heater is turned off, and only the main heater generates heat to maintain the furnace temperature.

[0005] The heating zone height of the cylindrical main heater is generally 200-300 mm, and the liquid level of the silicon melt is generally located in the middle and upper part of the heater heating zone. Within the heater heating zone, heat is concentrated, and the silicon melt in the crucible is heated to produce strong thermal convection. The silicon melt continuously erodes the quartz crucible through thermal convection, causing the oxygen content in the melt to increase, affecting the quality of the single crystal silicon. With the development of the market, higher requirements are put forward for the oxygen content of single crystal silicon. Therefore, reducing the oxygen content of single crystal silicon has become a key problem in the industry.

[0006] Currently, the industry reduces the heating zone height of the heater to reduce the heating range of the silicon melt and reduce the intensity of the thermal convection of the silicon melt. However, if the heating zone height is too low, the side heating range will be small, and the temperature of the area far from the heater at the bottom of the crucible will be too low, which can easily cause secondary crystallization. The silicon material will expand and break the quartz crucible when it undergoes secondary crystallization.

[0007] With the market demand, the silicon single crystal develops to large diameter, the matched thermal field is also larger and larger, and the diameter and height of the quartz crucible are also increased. The bottom of the crucible is farther away from the heater, and directly increasing the heating area will increase the oxygen content of the single crystal. Therefore, designing a heater which can reduce the melt thermal convection and will not cause the melt to crystallize again is an urgent problem for the technical personnel in the industry.

[0008] In the axial direction of the cylindrical heater, the upper half has a small cross-sectional area, a large heating resistance, a high power and a large amount of heat, and the lower half has a large cross-sectional area, a small heating resistance, a low power and a small amount of heat. The lower half of the heating petals is extended in length with intervals to disperse the heat. In this way, when only the main heater is turned on, the upper half has a large amount of heat to ensure the temperature of the liquid surface position, and the lower half has a small amount of heat to maintain the liquid temperature, so that the molten silicon is not caused to crystallize again and the molten silicon is not caused to have violent thermal convection to reduce the oxygen content of the crystal. Practical new type content

[0009] In view of the defects in the prior art, the purpose of the present application is to provide a reduced oxygen type graphite heater, which solves the above technical problems existing in the prior art.

[0010] The purpose of the present application can be achieved by the following technical solutions:

[0011] A reduced oxygen type graphite heater comprises a heating part and a leg piece,

[0012] The heating part comprises a first U-shaped heating petal and a second U-shaped heating petal, the first U-shaped heating petal and the second U-shaped heating petal are connected in sequence at the head and tail, the first U-shaped heating petals and the second U-shaped heating petals of adjacent two groups are connected in series by power supply, and the whole is surrounded to form a circular ring structure, the first U-shaped heating petals are located above the single crystal silicon liquid surface as a whole, and the second U-shaped heating petals are located below the single crystal silicon liquid surface as a whole.

[0013] The radial cross-sectional area of the first U-shaped heating petal is smaller than that of the second U-shaped heating petal.

[0014] The leg piece is symmetrically arranged at the lower part of the heating part and extends downward.

[0015] Further, the second U-shaped heating petals of adjacent two groups are distributed in a long-short interval in the up-down direction.

[0016] Further, the first U-shaped heating petals and the second U-shaped heating petals occupy at least 1 / 2 height in the up-down direction.

[0017] Further, the radial thickness of the first U-shaped heating petal is smaller than that of the second U-shaped heating petal, and the radial width of the circular ring is equal.

[0018] Further, the first U-shaped heating petal is located at a radial width smaller than a radial width of the second U-shaped heating petal, and the radial thickness of the circular ring is equal.

[0019] Further, the first U-shaped heating petal and the second U-shaped heating petal are integrally formed.

[0020] Further, the first U-shaped heating petal and the second U-shaped heating petal are integrally formed.

[0021] Further, the first U-shaped heating petal and the second U-shaped heating petal are integrally formed.

[0022] The utility model discloses the beneficial effect:

[0023] 1, the heating part of the device is composed of the first U-shaped heating petal and the second U-shaped heating petal, forms the circular ring structure, and is suitable for different heating demands. The first U-shaped heating petal is located above the monocrystalline silicon liquid surface, and the second U-shaped heating petal is located below the liquid surface, which optimizes heat distribution.

[0024] 2, the radial cross-sectional area of the first U-shaped heating petal of the device is smaller than the second U-shaped heating petal, which enhances the concentration of heat and the conduction efficiency, so that the upper half part has small cross-sectional area, large heating resistance, high power and large heat, the lower half part has large cross-sectional area, small heating resistance, low power and small heat, the upper half part has large heat, can guarantee the temperature of the liquid surface position, the lower half part has small heat, can maintain the liquid temperature, does not make the molten silicon produce secondary crystallization, and also does not make the molten silicon produce violent heat convection, to reduce the oxygen content of the crystal.

[0025] 3, the first U-shaped and the second U-shaped heating petal of the device are integrally formed, which simplifies the processing flow, improves the manufacturing efficiency, simultaneously adopts the four-part type to form the circular ring structure, is convenient for processing and assembly, can use small size graphite raw materials, and reduces the manufacturing cost. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical scheme in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description.

[0027] Figure 1 It is the overall structure schematic diagram of the utility model embodiment 1;

[0028] Figure 2 It is the local structure schematic diagram of the heating part of the utility model embodiment 1;

[0029] Figure 3 It is the overall structure schematic diagram of the utility model embodiment 2;

[0030] Figure 4 is a partial structure schematic diagram of the heating part of the utility model embodiment 2;

[0031] Figure 5 is a whole structure schematic diagram of the utility model embodiment 3;

[0032] Figure 6 is a partial structure schematic diagram of the heating part of the utility model embodiment 3; DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the embodiments of the utility model. Based on the embodiments in the utility model, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the utility model.

[0034] As Figure 1 indicated, the utility model embodiment provides a kind of oxygen-reducing graphite heater, including heating part 1, leg piece 2 and connecting plate piece 3.

[0035] Heating part 1 includes first U-shaped heating petal 11, second U-shaped heating petal 12, first U-shaped heating petal 11 and second U-shaped heating petal 12 are sequentially connected head to tail, and make the whole into annular structure to form heating part 1 whole, when using, first U-shaped heating petal 11 whole is located above single crystal silicon liquid surface, and second U-shaped heating petal 12 whole is located below single crystal silicon liquid surface;

[0036] And the radial cross-sectional area of first U-shaped heating petal 11 is less than the radial cross-sectional area of second U-shaped heating petal 12;Because the upper half section area is small, heating resistance is large, power is high, and heat quantity is more, the lower half section area is large, heating resistance is small, power is low, and heat quantity is less, and the lower half heating petal is extended in length with interval, to disperse heat quantity. Like this, when only main heating part 1 is opened, the upper half heat quantity can guarantee the temperature of liquid surface position, and the lower half heat quantity can maintain liquid temperature, so that secondary crystallization of molten silicon is not caused, and intense thermal convection of molten silicon is not caused, to reduce the oxygen content of crystal.

[0037] Leg piece 2 is symmetrically arranged and extends downward in the lower part of heating part 1, to provide stable support.

[0038] Further, when second U-shaped heating petal 12 between adjacent two groups presents equal height trend in up-down direction, first U-shaped heating petal 11 and second U-shaped heating petal 12 occupy 1 / 2 equal height in up-down direction at this time;When second U-shaped heating petal 12 between adjacent two groups presents interval distribution of one long and one short in up-down direction, the heating petal (second U-shaped heating petal 12) in the lower part of heater is extended in length with interval, so that the heat quantity of lower heating area gradually decreases from top to bottom.

[0039] Embodiment 1

[0040] As shown in Figure 1 , Figure 2 , on the basis of the original cylindrical heating part 1, a thinning heating section (i.e. the first U-shaped heating lobe 11) is arranged in the upper half of the axial direction of the heating part 1, the radial cross-sectional area of the thinning heating section is smaller than that of the remaining part (the second U-shaped heating lobe 12); the proportion of the thinning heating section in the height direction is about 1 / 2; the thinning heating section has the same slot width as the remaining part, and the radial thickness of the thinning heating section is smaller than the slot width of the remaining part (the second U-shaped heating lobe 12) of the heater.

[0041] Embodiment 2

[0042] As shown in Figure 3 , Figure 4 , on the basis of the original cylindrical heater, a thinning heating section (i.e. the first U-shaped heating lobe 11) is arranged in the upper half of the axial direction of the heater, the radial cross-sectional area of the thinning heating section is smaller than that of the remaining part (the second U-shaped heating lobe 12); the proportion of the thinning heating section in the height direction is about 1 / 2; the slot width of the thinning heating section is greater than that of the remaining part of the heater, and the radial thickness of the thinning heating section is smaller than the slot width of the remaining part of the heater.

[0043] Embodiment 3

[0044] As shown in Figure 5 , Figure 6 , at this time, the radial thickness of the first U-shaped heating lobe 11 can be smaller than that of the second U-shaped heating lobe 12, and the radial width of the first U-shaped heating lobe 12 can be smaller than that of the second U-shaped heating lobe 12, and the radial thickness of the circular ring is equal. This design scheme can realize the

[0045] The slot width of the first U-shaped heating lobe 11 and the second U-shaped heating lobe 12 is equal, which is convenient for machining operation.

[0046] Further, the first U-shaped heating lobe 11 and the second U-shaped heating lobe 12 are integrally formed. The 1 / 4 circular arcs surrounded by the first U-shaped heating lobe 11 and the second U-shaped heating lobe 12 are connected by the connecting plate 3, so that each time of machining only needs to machine 1 / 4 circular arc structure, and then the annular connection can be carried out, adopting a four-part structure. This design method can use non-integral graphite material for machining, can use small size graphite raw materials, or even lower corner materials for machining, so as to reduce the size limitation of graphite raw materials, greatly reduce the manufacturing cost, and further realize the cost control of the photovoltaic industry.

[0047] The basic principle, main features and advantages of the present application are shown and described above. Those skilled in the art should understand that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A reducing oxygen type graphite heater, comprising a heating part (1) and a leg part (2), characterized in that: the heating part (1) comprises first U-shaped heating petals (11) and second U-shaped heating petals (12), the first U-shaped heating petals (11) and the second U-shaped heating petals (12) are connected in sequence from head to tail, the first U-shaped heating petals (11) and the second U-shaped heating petals (12) of adjacent two groups are connected in series in power supply, the whole forms a circular ring structure, the first U-shaped heating petals (11) are located above the monocrystalline silicon liquid surface, and the second U-shaped heating petals (12) are located below the monocrystalline silicon liquid surface; the radial cross-sectional area of the first U-shaped heating petals (11) is smaller than that of the second U-shaped heating petals (12); the leg part (2) is symmetrically arranged at the lower part of the heating part (1) and extends downward.

2. The oxygen-reducing graphite heater according to claim 1, wherein The second U-shaped heating petals (12) between adjacent two groups are arranged in a long-short interval in the up-down direction.

3. The oxygen-reducing graphite heater according to claim 2, wherein The first U-shaped heating petals (11) and the second U-shaped heating petals (12) occupy at least 1 / 2 height in the up-down direction.

4. The oxygen-reducing graphite heater according to claim 1, wherein The radial thickness of the first U-shaped heating petals (11) is smaller than that of the second U-shaped heating petals (12), and the radial width of the circular ring is equal.

5. The oxygen-reducing graphite heater according to claim 1, wherein The radial width of the first U-shaped heating petals (11) is smaller than that of the second U-shaped heating petals (12), and the radial thickness of the circular ring is equal.

6. The oxygen-reducing graphite heater according to claim 1, wherein The slot width of the middle part of the first U-shaped heating petals (11) and the second U-shaped heating petals (12) is equal.

7. The oxygen-reducing graphite heater according to claim 1, wherein The first U-shaped heating petals (11) and the second U-shaped heating petals (12) are integrally formed.

8. The oxygen-reducing graphite heater according to claim 1, wherein The first U-shaped heating petals (11) and the second U-shaped heating petals (12) are connected by connecting plates (3) between 1 / 4 arcs.

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