Diffusion furnace

Abstract

The utility model discloses a diffusion furnace, and belongs to the technical field of solar cells. The diffusion furnace is used for placing a boat body, the diffusion furnace comprises a furnace tube, a first flow blocking piece and a second flow blocking piece, the furnace tube comprises a gas inlet end arranged at a furnace mouth and a gas outlet end arranged at a furnace tail, and the furnace tube is communicated with the outside through the gas inlet end and the gas outlet end; the first flow blocking piece and the second flow blocking piece are both arranged in the furnace tube, the first flow blocking piece is close to the gas inlet end, the second flow blocking piece is close to the gas outlet end, gaps are formed between the first flow blocking piece and the inner wall of the furnace tube and between the second flow blocking piece and the inner wall of the furnace tube, and the two gaps communicate with the gas inlet end and the gas outlet end; the distance between the first flow blocking piece and the boat body is Y1, the distance between the second flow blocking piece and the boat body is Y2, and Y1 is smaller than Y2, so that the uniformity and stability of airflow are improved, and the uniformity of the thickness of a film on a silicon wafer is ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, in particular to a diffusion furnace. Background Art

[0002] The diffusion furnace includes a furnace tube, which is provided with an air inlet and an air outlet. In the process engineering, the boat used to carry the silicon wafer is located in the furnace tube, and the process gas is introduced into the air inlet so that the surface of the silicon wafer contacts the process gas to achieve coating. However, the process airflow at the air inlet and the air outlet is uneven, resulting in poor film thickness uniformity of the silicon wafers near the air inlet and the air outlet. In the prior art, one solution is to set a perforated flow plate in the furnace tube, so that the process gas flows from the air inlet through the multiple holes of the flow plate into the furnace tube, and then flows out of the furnace tube through the multiple holes of the flow plate, thereby improving the uniformity and stability of the airflow. However, the perforated flow plate does not significantly improve the film thickness uniformity. Another solution is to use waste silicon wafers as dummy wafers (also called companion wafers) when plating the boat to ensure that the airflow is relatively uniform and stable when the silicon wafers on both sides of the furnace tube are diffused. However, the silicon wafer can only be used once. It will be deformed and cannot be restored after the second use, which is costly in the long term. Utility Model Content

[0003] The purpose of the utility model is to provide a diffusion furnace to improve the uniformity and stability of air flow and ensure the uniformity of film thickness on silicon wafers.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] A diffusion furnace for placing a boat, comprising:

[0006] A furnace tube, comprising an air inlet end provided at the furnace mouth and an air outlet end provided at the furnace tail, wherein the furnace tube is connected to the outside through the air inlet end and the air outlet end;

[0007] A first baffle and a second baffle are both disposed in the furnace tube, the first baffle being close to the air inlet end, the second baffle being close to the air outlet end, a gap being provided between the first baffle and the second baffle and the inner wall of the furnace tube, the two gaps being in communication with the air inlet end and the air outlet end;

[0008] The distance between the first flow blocking member and the boat body is Y1, and the distance between the second flow blocking member and the boat body is Y2, where Y1<Y2.

[0009] In some possible implementations, the radius of the first flow blocking member is Z1, the radius of the second flow blocking member is Z2, 15 cm ≤ Y1 < Z1, Z2 < Y2 ≤ 3Z2 / 2.

[0010] In some possible embodiments, the radius of the first baffle is Z1, the turning angle of the airflow at the furnace mouth is α, tanα=Y1 / Z1; the radius of the second baffle is Z2, the turning angle at the furnace tail is β, tanβ=Y2 / Z2, α>β, 56°≥the turning angle at the furnace mouth>45°, 45°>the turning angle at the furnace tail≥34°.

[0011] In some possible implementations, the internal radius of the furnace tube is X, the radius of the first baffle is Z1, X-2≥Z1≥X-4; and / or, the internal radius of the furnace tube is X, the radius of the second baffle is Z2, X-2≥Z2≥X-4.

[0012] In some possible implementations, the first flow baffle and the second flow baffle each include 5 to 8 baffles, and the plurality of baffles are arranged in parallel and spaced apart along the length direction of the furnace tube.

[0013] In some possible implementations, the distance between two adjacent baffles of the first baffle member is 4 cm to 6 cm;

[0014] And / or, a distance between two adjacent baffles of the second baffle member is 10 cm to 15 cm.

[0015] In some possible embodiments, the second baffle includes a first baffle and a second baffle arranged in parallel and spaced apart, the first baffle is provided with a through hole, the first baffle is arranged between the second baffle and the air outlet, and the through hole connects the air inlet and the air outlet.

[0016] In some possible implementations, there are three first baffles, and there are two second baffles. The three first baffles are arranged on a side of the two second baffles close to the air outlet end.

[0017] In some possible implementations, the first flow blocking member is disposed on a conveying paddle, and the conveying paddle is connected to the furnace door at the furnace opening.

[0018] In some possible implementations, the second baffle is disposed on a bracket, and the bracket is connected to the cover plate at the furnace tail.

[0019] Beneficial effects of the utility model:

[0020] The utility model provides a diffusion furnace, which comprises a first baffle disposed near the inlet end of a furnace tube and a second baffle disposed near the outlet end of the furnace tube. When process gas is introduced from the inlet end, the first baffle guides the process gas along the inner wall of the furnace tube toward the center of the furnace tube, while the second baffle guides the process gas from the center of the furnace tube toward the inner wall of the furnace tube before flowing out from the outlet end. When the process gas flows into and out of the center of the furnace tube, the first baffle and the second baffle cause the process gas to flow perpendicularly to the horizontal direction, generating a component velocity perpendicular to the horizontal direction, thereby reducing the horizontal gas velocity at the furnace mouth and furnace tail. Specifically, the horizontal velocity of the gas flow is reduced by the gas flow diversion in the furnace tube, matching the horizontal velocity reduction in the silicon wafer region (i.e., the center of the furnace tube) caused by surface friction of the silicon wafer, thereby ensuring that the gas velocity at the furnace tube and silicon wafer surfaces is close, improving the uniformity of the gas velocity at the edge region at the junction of the silicon wafer and the furnace tube and in the middle region of the silicon wafer, and thereby improving the uniformity of the film thickness within the silicon wafers on the head and tail boats. The distances between the first baffle and the second baffle and the boat body determine the turning angle of the airflow. The smaller the distances Y1 and Y2 from the boat body, the larger the turning angle, and the more the horizontal flow velocity decreases. Since the furnace tail is close to the pump port, the horizontal flow velocity of the silicon wafer surface on the boat body near the furnace tail outlet end is greater than the horizontal flow velocity of the silicon wafer surface on the boat body near the furnace mouth inlet end. By setting Y1 < Y2, the turning angle at the furnace mouth is greater than the turning angle at the furnace tail, thereby matching the difference in horizontal flow velocity of the silicon wafer surface near the furnace tail and near the furnace mouth, further ensuring the uniformity of the film thickness. No dummy films are set at either the furnace mouth or the furnace tail, and the production capacity is increased by more than 10%, and there is no maintenance cost for replacing dummy films. Compared with the current technology, the uniformity of the film thickness is improved by using the uniform flow plates at the furnace mouth and the furnace tail without increasing the cost of the machine manufacturing end. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the interior of a diffusion furnace provided by a specific embodiment of the present utility model;

[0022] Figure 2 This is a schematic diagram of the furnace mouth of a diffusion furnace provided by a specific embodiment of the present utility model;

[0023] Figure 3 It is a schematic diagram of the tail of a diffusion furnace provided by a specific embodiment of the present utility model.

[0024] In the picture:

[0025] 1. Furnace tube; 2. First baffle; 21. Baffle; 3. Second baffle; 31. First baffle; 311. Through hole; 32. Second baffle; 4. First boat body; 5. Second boat body; 6. Conveying paddle; 7. Bracket; 8. Furnace door; 9. Cover. DETAILED DESCRIPTION

[0026] To make the technical problems solved by the present invention, the technical solutions adopted, and the technical effects achieved more clearly, the technical solutions of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the scope of protection of the present invention.

[0027] In the description of this utility model, unless otherwise specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this utility model based on the specific circumstances.

[0028] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Moreover, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0029] like Figure 1-Figure 3 As shown, this embodiment provides a diffusion furnace for accommodating a boat. The diffusion furnace includes a furnace tube 1, a first baffle 2, and a second baffle 3. The furnace tube 1 includes an air inlet located at the furnace entrance and an air outlet located at the furnace tail. The furnace tube 1 communicates with the outside world through the air inlet and air outlet. Both baffles are located within the furnace tube 1, with the first baffle 2 located near the air inlet and the second baffle 3 located near the air outlet. A gap is defined between the first baffle 2 and the second baffle 3 and the inner wall of the furnace tube 1, connecting the air inlet and air outlet.

[0030] The boat is arranged between the first baffle 2 and the second baffle 3, that is, the boat is placed at the center of the furnace tube 1. The boat is used to carry silicon wafers. The silicon wafers are arranged on the boat so that the silicon wafers are arranged at the center of the furnace tube 1. The center of the furnace tube 1 is the silicon wafer area.

[0031] By disposing a first baffle 2 near the inlet end of the furnace tube and a second baffle 3 near the outlet end of the furnace tube, process gas is introduced from the inlet end. The first baffle 2 guides the process gas along the inner wall of the furnace tube 1 toward the center of the furnace tube 1. The second baffle 3 guides the process gas from the center of the furnace tube 1 toward the inner wall of the furnace tube 1 and then out of the outlet end. When the process gas flows into and out of the center of the furnace tube 1, the first baffle 2 and the second baffle 3 cause the process gas to flow perpendicular to the horizontal direction. This generates a component velocity perpendicular to the horizontal direction, thereby reducing the horizontal gas flow velocity at the furnace mouth and furnace tail. That is, the airflow of furnace tube 1 is used to reduce the horizontal velocity of the airflow, matching the horizontal velocity reduction of the airflow in the silicon wafer area (i.e., the center of furnace tube 1) caused by the friction of the silicon wafer surface, thereby ensuring that the gas flow rates of furnace tube 1 and the silicon wafer surface are close, improving the uniformity of the gas flow rate in the edge area at the junction of the silicon wafer and furnace tube 1 and the middle area of ​​the silicon wafer, and thus improving the uniformity of the film thickness of the silicon wafers on the head and tail boats. No dummy films are set at the furnace mouth and the furnace tail, the production capacity is increased by more than 10%, and there is no maintenance cost for replacing dummy films. Compared with the current technology, the uniformity of film thickness is improved by using flow plates at the furnace mouth and the furnace tail without increasing the cost of machine manufacturing.

[0032] The distance between the first baffle 2 and the boat is Y1, and the distance between the second baffle 3 and the boat is Y2, where Y1 is less than Y2. The distances between the first baffle 2 and the second baffle 3 and the boat determine the airflow's turning angle. The smaller the distances Y1 and Y2 from the boat, the larger the turning angle, and the greater the reduction in horizontal flow velocity. Because the furnace tail is close to the pump inlet, the horizontal flow velocity of the silicon wafer surface on the boat near the furnace tail outlet is greater than the horizontal flow velocity of the silicon wafer surface on the boat near the furnace inlet. By setting Y1 to less than Y2, the turning angle at the furnace mouth is greater than the turning angle at the furnace tail. This matches the difference in horizontal flow velocity between the silicon wafer surfaces near the furnace tail and the furnace mouth, further ensuring film thickness uniformity.

[0033] In one embodiment, a plurality of boat bodies are provided, including a first boat body 4 and a second boat body 5. The first baffle 2 is adjacent to the first boat body 4, and the distance between the first baffle 2 and the first boat body 4 is Y1. The second baffle 3 is adjacent to the second boat body 5, and the distance between the second baffle 3 and the second boat body 5 is Y2, where Y1 < Y2. In another embodiment, a single boat body may be provided.

[0034] Optionally, the radius of the first baffle 2 and the radius of the second baffle 3 are Z1 and Z2, respectively, and 15 cm ≤ Y1 < Z1, Z2 < Y2 ≤ 3Z2 / 2. When the radius of the first baffle 2 and the radius of the second baffle 3 are the same, that is, Z1 = Z2, the distance between the first baffle 2 and the second baffle 3 and the boat body determines the airflow deflection angle, avoiding an angle that is too large or too small, resulting in the horizontal component velocity of the airflow at the junction of the silicon wafer and the furnace tube 1 not matching the flow velocity on the silicon wafer surface, resulting in a difference in film thickness between the silicon wafer at the junction and the center of the silicon wafer, thereby reducing film thickness uniformity.

[0035] In one embodiment, X=24, Z1=22, Z2=21, Y1=20, Y2=30.

[0036] In one embodiment, a first baffle 2 is located near a first boat 4, the distance between the first baffle 2 and the first boat 4 is Y1, the radius of the first baffle 2 is Z1, and the airflow deflection angle at the furnace mouth is α, where tanα = Y1 / Z1. A second baffle 3 is located near a second boat 5, the distance between the second baffle 3 and the second boat 5 is Y2, the radius of the second baffle 3 is Z2, and the deflection angle at the furnace tail is β, where tanβ = Y2 / Z2, where α>β. Because the furnace tail is close to the pump port, the horizontal velocity of the airflow on the silicon wafer surface on the boat near the furnace tail outlet is greater than the horizontal velocity of the airflow on the silicon wafer surface on the boat near the furnace inlet. By setting the deflection angle at the furnace mouth to be greater than the deflection angle at the furnace tail, the difference in horizontal flow velocity between the silicon wafer surface near the furnace tail and the furnace mouth is matched, further ensuring film thickness uniformity. Optionally, the turning angle at the furnace mouth is 56°≥45°, and the turning angle at the furnace tail is 45°≥34°, to avoid the angle being too large or too small, which may cause the horizontal component velocity of the airflow at the junction of the silicon wafer and the furnace tube 1 to be unable to match the flow velocity on the surface of the silicon wafer, resulting in a difference in the film thickness of the silicon wafer at the junction and the film thickness of the silicon wafer at the center position, thereby reducing the uniformity of the film thickness.

[0037] In another embodiment, the internal radius of the furnace tube 1 is X, the radius of the first baffle 2 is Z1, and X-2 ≥ Z1 ≥ X-4; and / or, the internal radius of the furnace tube 1 is X, the radius of the second baffle 3 is Z2, and X-2 ≥ Z2 ≥ X-4. When Z1 or Z2 is greater than X-2, taking the first baffle 2 as an example, the distance between the first baffle 2 and the inner wall of the furnace tube 1, i.e., the gap, is too large, resulting in excessive vertical and horizontal component velocities of the airflow at that location, poor airflow uniformity and stability, and thus reduced film thickness uniformity. When Z1 or Z2 is less than X-4, taking the first baffle 2 as an example, the distance between the first baffle 2 and the inner wall of the furnace tube 1, i.e., the gap, is too small, resulting in excessive vertical and horizontal component velocities of the airflow at that location, resulting in insufficient gas concentration at the center of the furnace tube 1 and a thin film thickness, thereby reducing film thickness uniformity.

[0038] The first baffle 2 includes 5 to 8 baffles 21, specifically 5, 6, 7, or 8. Multiple baffles 21 are spaced parallel to each other along the length of the furnace tube 1. The baffles 21 provide thermal insulation, and increasing the number of baffles 21 improves thermal insulation. However, an excessive number of baffles 21 occupies more space and increases the overall structural complexity. The spacing between adjacent baffles 21 of the first baffle 2 is 4 to 6 cm. Exemplarily, the spacing can be 4 cm, 5 cm, or 6 cm, etc., without limitation. The spacing between adjacent baffles of the second baffle 3 is 10 to 15 cm. Exemplarily, the spacing can be 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, or 15 cm, etc., without limitation.

[0039] Similarly, the second baffle 3 includes five to eight baffles, specifically five, six, seven, or eight, arranged in parallel and spaced relation along the length of the furnace tube 1. Furthermore, the multiple baffles of the second baffle 3 are divided into first baffles 31 and second baffles 32, arranged in parallel and spaced relation. For example, three first baffles 31 and two second baffles 32 are provided. The first baffle 31 has a through hole 311, located between the second baffle 32 and the gas outlet. The through hole 311 connects the gas inlet and gas outlet. Process gas can flow through the through hole 311 of the first baffle 31 or through the gap between the first baffle 31 and the furnace tube 1, increasing the ventilation flow rate and preventing insufficient gas discharge at the furnace tail. Optionally, multiple first baffles 31 and multiple second baffles 32 are provided, with multiple first baffles 31 located between the multiple second baffles 32 and the gas outlet. Exemplarily, three first baffles 31 are provided, and two second baffles 32 are provided. The three first baffles 31 are provided on a side of the two second baffles 32 close to the air outlet end.

[0040] Optionally, the first baffle 2 is provided on the conveying paddle 6, and the conveying paddle 6 is connected to the furnace door 8 at the furnace mouth. When the boat is placed in the diffusion furnace, the boat is provided on the conveying paddle 6, and the furnace door 8 is opened, and the conveying paddle 6, the boat and the first baffle 2 can be simultaneously moved out of the furnace tube 1. When the conveying paddle 6 is sent into the furnace tube 1, when the furnace door 8 is closed, the boat is transported to a preset position to ensure accurate positioning. The overall transportation is convenient for operation. It also avoids the first baffle 2 being separately provided from the boat, and structural interference with the first baffle 2 during the transportation of the boat.

[0041] The second baffle 3 is arranged on a bracket 7, and the bracket 7 is connected to the cover plate 9 at the tail of the furnace for easy installation.

[0042] Obviously, the above embodiments of the present invention are merely examples for the purpose of clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the claims of the present invention.

Claims

1. A diffusion furnace for placing a boat, characterized in that: include: A furnace tube (1) comprises an air inlet end provided at a furnace mouth and an air outlet end provided at a furnace tail, wherein the furnace tube (1) is connected to the outside world through the air inlet end and the air outlet end; A first baffle (2) and a second baffle (3) are both arranged in the furnace tube (1), the first baffle (2) being close to the air inlet end, the second baffle (3) being close to the air outlet end, a gap being provided between the first baffle (2) and the second baffle (3) and the inner wall of the furnace tube (1), the two gaps being in communication with the air inlet end and the air outlet end; The distance between the first flow blocking member (2) and the boat body is Y1, and the distance between the second flow blocking member (3) and the boat body is Y2, where Y1<Y2.

2. The diffusion furnace according to claim 1, characterized in that The radius of the first flow blocking member (2) and the radius of the second flow blocking member (3) are Z1 and Z2 respectively, 15cm≤Y1<Z1, Z2<Y2≤3Z2 / 2.

3. The diffusion furnace according to claim 1, characterized in that The radius of the first baffle (2) is Z1, the turning angle of the airflow at the furnace mouth is α, tanα=Y1 / Z1; the radius of the second baffle (3) is Z2, the turning angle at the furnace tail is β, tanβ=Y2 / Z2, α>β, 56°≥the turning angle at the furnace mouth>45°, 45°>the turning angle at the furnace tail≥34°.

4. The diffusion furnace according to claim 1, wherein: The internal radius of the furnace tube (1) is X, the radius of the first baffle (2) is Z1, and X-2≥Z1≥X-4; and / or the internal radius of the furnace tube (1) is X, the radius of the second baffle (3) is Z2, and X-2≥Z2≥X-4.

5. The diffusion furnace according to claim 1, wherein: The first baffle (2) and the second baffle (3) each comprise 5 to 8 baffles, and the plurality of baffles are arranged in parallel and at intervals along the length direction of the furnace tube (1).

6. The diffusion furnace according to claim 5, characterized in that The distance between two adjacent baffles of the first baffle member (2) is 4 cm to 6 cm; And / or, the distance between two adjacent baffles of the second baffle member (3) is 10 cm to 15 cm.

7. The diffusion furnace according to claim 1, characterized in that The second baffle member (3) comprises a first baffle plate (31) and a second baffle plate (32) arranged in parallel and spaced apart from each other, the first baffle plate (31) being provided with a through hole (311), the first baffle plate (31) being arranged between the second baffle plate (32) and the air outlet, and the through hole (311) communicating with the air inlet end and the air outlet end.

8. The diffusion furnace according to claim 7, characterized in that There are three first baffles (31) and two second baffles (32), and the three first baffles (31) are arranged on one side of the two second baffles (32) close to the air outlet end.

9. The diffusion furnace according to any one of claims 1 to 8, characterized in that: The first flow blocking member (2) is arranged on a conveying paddle (6), and the conveying paddle (6) is connected to a furnace door (8) at the furnace opening.

10. The diffusion furnace according to any one of claims 1 to 8, characterized in that: The second baffle (3) is arranged on a bracket (7), and the bracket (7) is connected to the cover plate (9) at the furnace tail.

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