Polysilicon reduction furnace and polysilicon chemical vapor deposition method

Abstract

The present invention discloses a polysilicon reduction furnace and a polysilicon chemical vapor deposition method. The polysilicon reduction furnace comprises: a furnace body; and a furnace top, wherein the furnace top is arranged on the top of the furnace body, and the inner surface of the furnace top is provided with a heat-reflecting coating layer. The inner surface of the furnace top of the polysilicon reduction furnace is provided with a heat-reflecting coating layer, thereby effectively reflecting heat to the top of the silicon rod, thereby increasing the temperature of the top of the silicon rod, making the temperature of this part of the silicon rod consistent with the whole silicon rod, playing a positive role in the deposition of this part of the silicon rod, and thus effectively improving the yield of the product.

Description

Technical Field

[0001] The present invention relates to the technical field of polysilicon production, and in particular to a polysilicon reduction furnace and a polysilicon chemical vapor deposition method. Background Art

[0002] Electronic-grade polysilicon is the basic raw material for the integrated circuit industry. The mainstream production technology in the industry is the modified Siemens process based on trichlorosilane. The core of the process is the process of heterogeneous chemical deposition using trichlorosilane and hydrogen as raw materials. The industry generally refers to this process as the reduction process. A gaseous mixture of trichlorosilane and hydrogen enters the air inlet at the bottom of the equipment at a certain proportion and temperature, and is deposited on the silicon core placed vertically in the furnace. The incompletely reacted chlorosilane exhaust gas will be discharged from the exhaust outlet at the bottom of the equipment.

[0003] During the reduction process, the silicon core and the silicon rods gradually deposited and grown are inverted U-shaped, and the surface temperature is controlled at 1000-1100°C. There is a serious problem of poor surface condition at the top of the silicon rod. This part of the silicon material is generally treated as waste and downgraded, which seriously affects the yield of the product. Therefore, the existing polysilicon production process still needs to be improved. Summary of the invention

[0004] The present invention aims to solve one of the technical problems in the related art at least to a certain extent. To this end, one object of the present invention is to provide a polysilicon reduction furnace and a polysilicon chemical vapor deposition method. By adopting the polysilicon reduction furnace and the polysilicon vapor deposition method, the phenomenon of poor surface state of the top silicon rod can be effectively improved, the single furnace yield can be improved and the cost can be reduced.

[0005] The inventors found in their research that the reason why the surface condition of the top silicon rod is not good is that the temperature inside the reactor is high, the surface temperature uniformity of the top silicon rod is difficult to control, and the fluidity of trichlorosilane and hydrogen at the top of the reactor is poor and stagnant, and there is also an inconsistency in the gas phase concentration. These factors work together to make it difficult to effectively improve the growth condition of the top silicon rod.

[0006] In view of this, in one aspect of the present invention, the present invention provides a polysilicon reduction furnace. According to an embodiment of the present invention, the polysilicon reduction furnace comprises: a furnace body; and a furnace top, the furnace top is arranged on the top of the furnace body, and the inner surface of the furnace top is provided with a heat reflective coating layer.

[0007] According to the polysilicon reduction furnace of the above embodiment of the present invention, a heat-reflecting coating layer is provided on the inner surface of the furnace top, thereby effectively reflecting heat to the top of the silicon rod, thereby increasing the temperature of the top of the silicon rod, making the temperature of this part of the silicon rod consistent with the silicon rod as a whole, playing a positive role in the deposition of this part of the silicon rod, and thus effectively improving the yield of the product.

[0008] In addition, the polysilicon reduction furnace according to the above embodiment of the present invention may also have the following additional technical features:

[0009] In some embodiments of the present invention, the heat reflective coating layer is a gold coating layer or a silver coating layer.

[0010] In some embodiments of the present invention, the heat reflective coating layer covers 60% to 80% of the total area of ​​the inner surface of the furnace roof.

[0011] In some embodiments of the present invention, annular wrinkles are distributed on the surface of the heat reflective coating layer.

[0012] In some embodiments of the present invention, the furnace top is hemispherical or hemispherical.

[0013] In another aspect of the present invention, the present invention proposes a polysilicon chemical vapor deposition method implemented by the polysilicon reduction furnace of the above embodiment. According to the embodiment of the present invention, the polysilicon chemical vapor deposition method includes: (1) supplying trichlorosilane and hydrogen into the polysilicon reduction furnace to carry out a first stage reaction; (2) continuing to supply trichlorosilane and hydrogen into the polysilicon reduction furnace to carry out a second stage reaction; (3) repeating steps (1) and (2) multiple times in sequence to obtain a polysilicon product; wherein the trichlorosilane flow rate in the first stage reaction is higher than the trichlorosilane flow rate in the second stage reaction.

[0014] According to the polysilicon chemical vapor deposition method of the above embodiment of the present invention, on the one hand, by adopting the polysilicon reduction furnace of the above embodiment, the growth state of the top silicon rod can be effectively improved. On the other hand, the method regulates the flow rate of trichlorosilane in the reaction in stages. By controlling the flow rate of trichlorosilane in the second stage reaction to be lower than that of the first stage reaction, the problem of inconsistent trichlorosilane concentrations at the upper and lower positions in the reactor can be effectively improved. The reason may be that the second stage reaction gives the adjustment time for deposition at the position where the gas phase trichlorosilane concentration is high in the middle position of the furnace. At the same time, the second stage reaction is also the adjustment time for self-crystal growth optimization of the popcorn surface that is easy to appear on the upper and top of the silicon rod. As a result, the polysilicon product prepared by this method is in a better state, has a higher yield rate, and has a lower production cost.

[0015] In addition, the polysilicon chemical vapor deposition method according to the above embodiment of the present invention may also have the following additional technical features:

[0016] In some embodiments of the present invention, the first stage reaction is carried out for 300s to 600s, and the second stage reaction is carried out for 120s to 300s.

[0017] In some embodiments of the present invention, in the first stage reaction, the flow rate of trichlorosilane is 1200kg / h to 1800kg / h, and the flow rate of hydrogen is 38kg / h to 92kg / h.

[0018] In some embodiments of the present invention, in the second stage reaction, the flow rate of trichlorosilane is 720 kg / h to 1440 kg / h, and the flow rate of hydrogen is 38 kg / h to 92 kg / h.

[0019] In some embodiments of the present invention, the voltage used in the first stage reaction and the second stage reaction is 50V to 120V.

[0020] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0022] Figure 1 is a schematic structural diagram of a polysilicon reduction furnace according to an embodiment of the present invention;

[0023] Figure 2 FIG. 4 is a flow curve diagram of trichlorosilane in a polysilicon chemical vapor deposition method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below, and the examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by reference to the accompanying drawings are exemplary, are intended to be used to explain the present invention, and are not to be construed as limitations of the present invention. In the embodiments, if specific techniques or conditions are not indicated, the techniques or conditions described in the literature in this area or the product specifications are carried out. The reagents used or the instruments that are not indicated by the manufacturer are all conventional products that can be obtained commercially.

[0025] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0026] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0027] In one aspect of the present invention, the present invention provides a polysilicon reduction furnace. Figure 1 According to an embodiment of the present invention, the polysilicon reduction furnace includes: a furnace body 100 and a furnace top 200 , the furnace top 200 is arranged on the top of the furnace body 100 , and a heat reflective coating layer 210 is provided on the inner surface of the furnace top 200 .

[0028] The polysilicon reduction furnace according to an embodiment of the present invention is further described in detail below.

[0029] According to an embodiment of the present invention, the polysilicon reduction furnace of the present invention is suitable for being used as a chemical vapor deposition (CVD) reactor for preparing polysilicon by a modified Siemens method. The polysilicon reduction furnace has a reaction space in which a silicon core suitable for depositing crystalline silicon generated by reduction of trichlorosilane and hydrogen is arranged. The inner surface of the furnace top 200 of the polysilicon reduction furnace is provided with a heat-reflecting coating layer 210, thereby effectively reflecting heat to the top of the silicon rod, thereby increasing the temperature of the top of the silicon rod, making the temperature of this part of the silicon rod consistent with the whole silicon rod, playing a positive role in the deposition of this part of the silicon rod, and thus effectively improving the yield of the product.

[0030] The specific material of the heat reflective coating layer 210 is not particularly limited, and can be formed by coating with a high heat reflectivity material commonly used in the art. According to some embodiments of the present invention, the heat reflective coating layer 210 can be a gold coating layer or a silver coating layer. The inventors have found that gold and silver have high heat reflectivity, can effectively increase the temperature of the top of the silicon rod, and are stable under the temperature and chemical conditions of the polysilicon reduction reaction, and will not adversely affect the polysilicon reduction reaction.

[0031] According to some embodiments of the present invention, the heat reflective coating layer 210 may cover 60% to 80% of the total area of ​​the inner surface of the furnace roof 200, such as 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, 80%, etc. Specifically, the coverage area of ​​the heat reflective coating layer 210 may be adjusted and modified according to the specific layout and quantity of silicon rods, so as to achieve a heating effect on the tops of all silicon rods in the furnace.

[0032] According to some embodiments of the present invention, the surface of the heat reflective coating layer 210 is distributed with annular folds (not shown in the drawings). Specifically, the annular folds may include a plurality of annular folds, similar to a corrugated plate. Thus, the gas phase flow in the stagnant area at the top of the reactor can be further improved, and the growth state of the silicon rod top can be improved.

[0033] In addition, the specific shape of the furnace roof 200 is not particularly limited. According to some embodiments of the present invention, the furnace roof 200 may be hemispherical or hemispherical.

[0034] In another aspect of the present invention, the present invention proposes a polysilicon chemical vapor deposition method implemented by the polysilicon reduction furnace of the above embodiment. According to the embodiment of the present invention, the polysilicon chemical vapor deposition method includes: (1) supplying trichlorosilane and hydrogen into the polysilicon reduction furnace to carry out a first-stage reaction; (2) continuing to supply trichlorosilane and hydrogen into the polysilicon reduction furnace to carry out a second-stage reaction; (3) repeating steps (1) and (2) multiple times (for example, twice, three times, four times, eight times, ten times, etc.) in sequence to obtain a polysilicon product; wherein the trichlorosilane flow rate in the first-stage reaction is higher than the trichlorosilane flow rate in the second-stage reaction.

[0035] The inventors have found that the state and yield of the prepared polysilicon products can be further improved by using the polysilicon reduction furnace of the above embodiment in combination with the polysilicon chemical vapor deposition method, and the production cost can be further reduced. Specifically, on the one hand, by using the polysilicon reduction furnace of the above embodiment, the growth state of the top silicon rod can be effectively improved. On the other hand, the method regulates the flow rate of trichlorosilane in the reaction in stages. By controlling the flow rate of trichlorosilane in the second stage reaction to be lower than that of the first stage reaction, the problem of inconsistent trichlorosilane concentrations at the upper and lower positions in the reactor can be effectively improved. The reason may be that the second stage reaction gives the adjustment time for deposition at the position where the gas phase trichlorosilane concentration is high in the middle position of the furnace. At the same time, the second stage reaction is also the adjustment time for self-crystal growth optimization of the popcorn surface that is easy to appear on the upper and top of the silicon rod. As a result, the polysilicon product prepared by this method is in a better state, has a higher yield, and has a lower production cost.

[0036] The polysilicon chemical vapor deposition method according to an embodiment of the present invention is further described in detail below.

[0037] According to some embodiments of the present invention, the first stage reaction may be performed for 300s to 600s, such as 300s, 400s, 500s, 600s, etc.; the second stage reaction may be performed for 120s to 300s, such as 120s, 180s, 240s, 300s, etc. The inventors have found that if the second stage reaction is performed for too short a time, it may lead to insufficient adjustment of the concentration in the furnace and the growth morphology of the crystal itself, and the uniformity of the upper and lower parts is still unsatisfactory.

[0038] According to some embodiments of the present invention, in the first stage reaction, the flow rate of trichlorosilane can be 1200kg / h to 1800kg / h, for example, 1200kg / h, 1300kg / h, 1400kg / h, 1500kg / h, 1600kg / h, 1800kg / h, etc.; the flow rate of hydrogen can be 38kg / h to 92kg / h, for example, 38kg / h, 48kg / h, 58kg / h, 68kg / h, 78kg / h, 88kg / h, 92kg / h, etc. In the second stage reaction, the flow rate of trichlorosilane can be 720kg / h to 1440kg / h, such as 720kg / h, 840kg / h, 960kg / h, 1080kg / h, 1200kg / h, 1320kg / h, 1440kg / h, etc.; the flow rate of hydrogen can be 32kg / h to 85kg / h, such as 32kg / h, 42kg / h, 52kg / h, 62kg / h, 72kg / h, 82kg / h, etc. Thus, the flow rate of trichlorosilane in the second stage reaction is about 60% to 80% of the normal value, or the flow rate of trichlorosilane in the second stage reaction is about 60% to 80% of the flow rate of trichlorosilane in the first stage reaction, thereby effectively improving the problem of inconsistent trichlorosilane concentrations at the upper and lower positions in the reactor. If the trichlorosilane flow rate in the second stage reaction is too low, the concentration of trichlorosilane in the furnace may drop too quickly, the overall silicon rod growth rate is low, the yield is insufficient, and it is not conducive to maintaining the temperature of the silicon rod. In addition, it can be understood by those skilled in the art that in each stage of the reaction, the flow rate of hydrogen should be adapted to the flow rate of trichlorosilane to meet the needs of polysilicon production.

[0039] As mentioned above, the trichlorosilane flow curves for the first and second stage reactions are as follows: Figure 2 Thus, the state and yield rate of the prepared polysilicon product can be further improved, and the production cost can be further reduced.

[0040] In addition, according to some embodiments of the present invention, in the first stage reaction and the second stage reaction, the voltage used can be 50V to 120V, such as 50V, 60V, 70V, 80V, 90V, 100V, 110V, 120V, etc. During the whole reaction process, the current passed into the silicon rod is about 3% to 5% higher than the normal value, thereby slightly increasing the surface temperature of the silicon rod by about 10°C to 15°C, thereby increasing the deposition rate of the silicon rod, compensating for the decrease in growth rate caused by the lower trichlorosilane feed amount in the second stage reaction, and taking into account both production capacity and production uniformity. If the current used in the reaction process is too large, the surface temperature of the silicon rod may be uncontrollable, causing some over-temperature points to appear on the surface, and the deposition rate is too fast, resulting in deterioration of the surface state.

[0041] According to some embodiments of the present invention, the polysilicon reduction furnace and the polysilicon chemical vapor deposition method proposed in the present invention are used to produce polysilicon, which can effectively improve the surface state of the top of the silicon rod from coral-like to smooth, and the portion of the silicon rod that can be used for electronic-grade polysilicon is increased from about 74% to 80% in the traditional process to more than 84%.

[0042] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0043] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A polysilicon reduction furnace, characterized in that: include: Furnace body; A furnace roof, the furnace roof is arranged on the top of the furnace body, and the inner surface of the furnace roof is provided with a heat reflecting coating layer; The heat reflective coating layer is a gold coating layer or a silver coating layer; The heat reflective coating layer covers 60% to 80% of the total area of ​​the inner surface of the furnace roof; The furnace top is hemispherical or hemispherical.

2. The polysilicon reduction furnace according to claim 1, characterized in that: The surface of the heat reflective coating layer is distributed with annular wrinkles.

3. A polycrystalline silicon chemical vapor deposition method implemented by the polycrystalline silicon reduction furnace according to claim 1 or 2, characterized in that: include: (1) supplying trichlorosilane and hydrogen into the polysilicon reduction furnace to carry out a first stage reaction; (2) continuing to supply trichlorosilane and hydrogen into the polysilicon reduction furnace to carry out a second stage reaction; (3) Repeating steps (1) and (2) multiple times to obtain a polycrystalline silicon product; The trichlorosilane flow rate in the first stage reaction is higher than the trichlorosilane flow rate in the second stage reaction.

4. The polysilicon chemical vapor deposition method according to claim 3, characterized in that: The first stage reaction is carried out for 300s to 600s, and the second stage reaction is carried out for 120s to 300s.

5. The polysilicon chemical vapor deposition method according to claim 3, characterized in that: In the first stage reaction, the flow rate of trichlorosilane is 1200kg / h to 1800kg / h, and the flow rate of hydrogen is 38kg / h to 92kg / h.

6. The polysilicon chemical vapor deposition method according to claim 3, characterized in that: In the second stage reaction, the flow rate of trichlorosilane is 720kg / h to 1440kg / h, and the flow rate of hydrogen is 32kg / h to 85kg / h.

7. The polysilicon chemical vapor deposition method according to claim 3, characterized in that: In the first stage reaction and the second stage reaction, the voltage used is 50V to 120V.

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