Diffusion device

Abstract

The utility model discloses a diffusion device. The diffusion equipment comprises a heating furnace body, a process pipe and a heat insulation structure. And the heating furnace body is sleeved outside the process pipe. The heat insulation structure is fixedly connected with one end of the process pipe. The heat insulation structure comprises a first heat insulation part, a second heat insulation part and a third heat insulation part connected with the first heat insulation part and the second heat insulation part, the first heat-insulating part is connected with the process pipe, and a heat-insulating space is formed between the first heat-insulating part and the second heat-insulating part. In this way, the temperature of the sealing piece can be effectively reduced, and the service life of the sealing piece is prolonged.

Description

Technical Field

[0001] The present application relates to the field of semiconductor technology, and in particular to diffusion equipment. Background Art

[0002] In the process of semiconductor preparation, silicon wafers need to go through processes such as texturing, diffusion, etching, coating and printing. The diffusion process refers to the process of placing silicon wafers into the diffusion equipment with a wafer boat as a carrier, and introducing protective gas and diffusion source into the diffusion equipment at a certain temperature to diffuse and deposit PN junctions on the surface of the silicon wafer. The temperatures at the mouths of annealing furnaces and diffusion furnaces are generally high. In related technologies, for example, during the use of diffusion equipment, technical problems such as process tube movement and sealing ring burnout under long-term high temperature conditions resulting in a short service life may occur, which will affect the working stability of the diffusion equipment. Utility Model Content

[0003] The embodiments of the present application provide a diffusion device that can increase the stability of the diffusion device during operation.

[0004] The embodiment of the present application provides a diffusion device. The device includes a heating furnace body, a process pipe, a first flange and a heat insulation structure, wherein the heating furnace body is sleeved outside the process pipe; the heat insulation structure is fixedly connected to one end of the process pipe, and the heat insulation structure includes a first heat insulation part and a second heat insulation part arranged at intervals, and a third heat insulation part connecting the first heat insulation part and the second heat insulation part; the first heat insulation part is connected to the process pipe, and a heat insulation space is formed between the first heat insulation part and the second heat insulation part; the first flange is sleeved outside the heat insulation structure.

[0005] Optionally, the first flange includes a limiting portion and a fixing portion, the fixing portion abuts against the second thermal insulation portion, the limiting portion abuts against the third thermal insulation portion, and a gasket is further provided between the limiting portion and the third thermal insulation portion.

[0006] Optionally, the fixing portion is provided with a first cooling pipeline, the limiting portion is provided with a second cooling pipeline, and the first cooling pipeline is connected to the second cooling pipeline.

[0007] Optionally, a cooling pipe is provided in the heat-insulating space, and the cooling pipe is used for cooling medium to flow through.

[0008] Optionally, the outer diameter of the first heat insulating portion is greater than the outer diameter of the process tube, and the diffusion device further includes a limiting member arranged on the outside of the heating furnace body, and the first heat insulating portion abuts against the limiting member.

[0009] Optionally, the diffusion device further includes a fixing plate and a second flange, wherein the fixing plate is sleeved outside the heat insulation structure, the second flange is arranged between the first flange and the fixing plate, and the first flange and the second flange are connected to the fixing plate.

[0010] Optionally, the diffusion device further comprises a seal, which is arranged between the second flange and the second insulation part.

[0011] Optionally, the second flange is provided with a protrusion extending toward the second insulation part, and the second insulation part, the second flange and the protrusion are arranged to form an accommodating space, and the accommodating space is used to accommodate the seal; the accommodating space is formed with an opening toward the first flange, and the first flange is provided with an abutting part toward the second flange, and the abutting part extends into the accommodating space from the opening for abutting the seal.

[0012] Optionally, the second flange is provided with a third cooling pipe.

[0013] Optionally, the diffusion device also includes pads and buffer pads stacked in the axial direction of the process tube, the pads and buffer pads are arranged between the second insulation part and the fixed plate, the pads are installed on the fixed plate, the buffer pads are installed on the pads, and the buffer pads are located between the pads and the second insulation part.

[0014] Optionally, the diffusion device further comprises a door body, which is nested and connected with the heat insulation structure to achieve sealing of the pipe opening of the process pipe. At least a portion of the door body abuts against the first flange, a sealing ring is arranged between the door body and the first flange, and the door body is also provided with a fourth cooling pipe for cooling the sealing ring.

[0015] The beneficial effect of the present application is that, different from the prior art, the heat-insulating structure located at the pipe opening of the process pipe forms a heat-insulating space, which can effectively reduce the temperature of the seal and extend the service life of the seal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] It should be noted that there are physical features and virtual features in the drawings of the present application. In the drawing marks of the present application, the lines with arrows point to virtual features such as insulation spaces and cooling pipes, while the lines without arrows point to physical features such as the first flange and the second flange.

[0017] Figure 1 It is a schematic diagram of the local structure of the diffusion device of the present application;

[0018] Figure 2 yes Figure 1 A schematic cross-sectional structure diagram of the diffusion device shown;

[0019] Figure 3 yes Figure 2 A partial enlarged view of the cross-sectional structure shown;

[0020] Figure 4 yes Figure 1 A cross-sectional view of a heat insulation structure in an embodiment of a diffusion device shown;

[0021] Figure 5 yes Figure 1 A schematic diagram of a heat insulation structure in another embodiment of the diffusion device shown;

[0022] Figure 6 yes Figure 1 A schematic structural diagram of the first flange of the diffusion device is shown.

[0023] The reference numerals in the figure represent: diffusion device 1; heating furnace body 11; limiter 111; process pipe 12; insulation structure 13; insulation space 130; first insulation part 131; second insulation part 132; third insulation part 133; support block 134; spacer 135; fixing plate 14; first flange 15; fixing part 151; first cooling pipe 1511; limiter 152; abutment part 153; entry joint 154; discharge joint 155; spacer 156; second cooling pipe 1521; second flange 16; protrusion 161; third cooling pipe 162; partition 163; seal 164; pad 17; buffer pad 18; door body 19; sealing ring 191; fourth cooling pipe 192. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0025] Combination Figures 1 to 3 The embodiment of the present application provides a diffusion device 1. The diffusion device 1 includes a heating furnace body 11, a process tube 12 and a heat insulation structure 13. The heating furnace body 11 is sleeved outside the process tube 12. The heating furnace body 11 can heat the process tube 12 to increase the temperature inside the process tube 12, so as to heat the carrier and the silicon wafer to meet the process conditions required for coating.

[0026] The thermal insulation structure 13 is fixedly connected to one end of the process pipe 12. The process pipe 12 and the thermal insulation structure 13 can be integrally arranged. In some other embodiments, the thermal insulation structure 13 is a part of the process pipe 12. The process pipe 12 may also include a body and a thermal insulation structure 13, and the body and the thermal insulation structure 13 are integrally fixedly connected. The body in this case is equivalent to the process pipe 12 in the aforementioned embodiment.

[0027] In some embodiments, the diffusion device 1 further includes a fixing plate 14 and a first flange 15. The heat insulation structure 13 can play a role of heat insulation on the one hand, and can cooperate with the first flange 15 and the fixing plate 14 on the other hand to limit the axial movement of the process pipe 12, as described in the following embodiments.

[0028] The fixing plate 14 is arranged outside the heat insulation structure 13. The fixing plate 14 is connected to the frame of the equipment (the frame is not marked in the figure). In other words, in the technical solution defined in the present application, the fixing plate 14 can be a frame fixed in a mechanical sense.

[0029] The first flange 15 is sleeved outside the thermal insulation structure 13, and the first flange 15 is fixedly connected to the fixing plate 14. The first flange 15 can limit the thermal insulation structure 13. The first flange 15 is arranged in an annular or circular shape. The thermal insulation structure 13 is arranged in an annular or circular shape. Optionally, the first flange 15, the thermal insulation structure 13 and the process pipe 12 can be coaxially arranged. Specifically, the first flange 15 includes a limiting portion 152 and a fixing portion 151, the fixing portion 151 is connected to the fixing plate 14, and the limiting portion 152 abuts against the thermal insulation structure 13. Among them, the fixing portion 151 and the limiting portion 152 are an integrally arranged structure.

[0030] The fixing portion 151 and the limiting portion 152 are arranged in a direction perpendicular to the axis of the process pipe 12. The fixing portion 151 can be connected to the fixing plate 14 by screwing, riveting or clamping. The fixing portion 151 can be directly or indirectly connected to the fixing plate 14. The fixing portion 151 can be indirectly connected to the fixing plate 14 through the pad 17, the buffer pad 18 or the second flange 16 mentioned later.

[0031] The limiting portion 152 abuts against the thermal insulation structure 13, thereby limiting the movement of the thermal insulation structure 13 and the process tube 12 along the axial direction. The limiting portion 152 may abut against the side of the thermal insulation structure 13 away from the process tube 12, thereby limiting the movement of the process tube 12 and the thermal insulation structure 13 along the direction from the process tube 12 to the thermal insulation structure 13 (that is, the furnace mouth direction or the furnace door direction). In other embodiments, the limiting portion 152 may also abut against the side of the thermal insulation structure 13 close to the process tube 12, thereby limiting the movement of the thermal insulation structure 13 and the process tube 12 along the direction from the thermal insulation structure 13 to the process tube 12 (that is, the furnace tail direction).

[0032] In some embodiments, the thermal insulation structure 13 includes a first thermal insulation portion 131 and a second thermal insulation portion 132 that are spaced apart, and a third thermal insulation portion 133 that connects the first thermal insulation portion 131 and the second thermal insulation portion 132. The first thermal insulation portion 131 is connected to the process pipe 12, and the third thermal insulation portion 133 is disposed at the side ends of the first thermal insulation portion 131 and the second thermal insulation portion 132 that are away from the process pipe 12. In other words, the thermal insulation structure 13 is disposed in a U-shape. Optionally, the first thermal insulation portion 131 and the second thermal insulation portion 132 extend along the axial direction of the process pipe 12.

[0033] On the one hand, the heat insulation structure 13 arranged in the above manner can make the second heat insulation part 132 and the third heat insulation part 133 protrude from the first heat insulation part 131. The second heat insulation part 132 or the third heat insulation part 133 can abut against the first flange 15 or the fixing plate 14, thereby limiting the movement of the heat insulation structure 13 in the axial direction.

[0034] On the other hand, the first insulation part 131 and the second insulation part 132 can separate the insulation space 130 (i.e., the gap in the U-shaped insulation structure 13). The insulation space 130 can extend the heat conduction path from the first insulation part 131 to the second insulation part 132, reduce the heat conduction efficiency, and thus play a heat insulation role, which can effectively reduce the temperature of the sealing member 164 and extend the service life of the sealing member 164.

[0035] In some embodiments, the diffusion device 1 further includes a refrigeration device. The refrigeration device can generate a cooling medium. For example, the cooling medium can be a cooling gas. The cooling gas can be blown into the aforementioned insulation space 130 through a pipeline to take away the heat of the insulation space 130, thereby reducing the temperature of the insulation space 130. In this way, the temperature of the sealing member 164 can be further reduced, and the service life of the sealing member 164 can be extended.

[0036] In some embodiments, the diffusion device 1 further includes a refrigeration device. The refrigeration device can generate a cooling medium. The cooling medium can be a cooling gas or a cooling liquid, which is not specifically limited here. A cooling pipe is provided in the insulation space 130, and the cooling pipe can allow the cooling medium to flow through, thereby reducing the temperature of the insulation space 130 and taking away the heat of the insulation space 130. In the above manner, the temperature of the sealing member 164 can be further reduced, and the service life of the sealing member 164 can be extended.

[0037] Combination Figure 4 In some embodiments, a support block 134 is provided between the first insulation part 131 and the second insulation part 132, and the support blocks 134 are arranged at intervals in the circumferential direction (the circumference is centered on the axial direction of the process tube 12). The support block 134 can support the second insulation part 132 and improve the structural strength of the insulation structure 13. For example, the support block 134 can be located between the first insulation part 131 and the second insulation part 132 and away from the third insulation part 133. Since one end of the first insulation part 131 and the second insulation part 132 can be supported by the third insulation part 133, the second insulation part 132 forms a cantilever beam relatively speaking. By providing the support block 134, both ends of the second insulation part 132 can be supported, which can fully increase the structural strength of the insulation structure 13. The support block 134 can be formed by welding or turning, etc., which is not specifically limited here.

[0038] Combination Figure 5In some embodiments, a spacer 135 is provided between the first insulation part 131 and the second insulation part 132. The spacers 135 are spaced apart in the circumferential direction (the circumference is centered on the axial direction of the process tube 12). The spacers 135 extend from the opening of the insulation space 130 to the third insulation part 133. In other words, the spacers 135 extend from the opening of the U-shaped structure to the third insulation part 133. The mechanical strength of the insulation structure 13 can be increased in the above manner.

[0039] It should be noted that the embodiment of the spacer 135 does not conflict with the embodiment of the support block 134. The two can be combined and arranged between the first insulation part 131 and the second insulation part 132. For example, the spacer 135 and the support block 134 can be arranged alternately and spaced in the circumferential direction.

[0040] In some embodiments, the fixing portion 151 of the first flange 15 abuts against the second heat insulating portion 132, and the limiting portion 152 of the first flange 15 abuts against the third heat insulating portion 133. The fixing portion 151 abuts against the second heat insulating portion 132, and can seal the fixing portion 151 and the second heat insulating portion 132 to a certain extent. The limiting portion 152 abuts against the third heat insulating portion 133, and can seal the limiting portion 152 and the third heat insulating portion 133 to a certain extent. Among them, since the heat insulating structure 13 is the aforementioned "U-shaped" structure, when the fixing portion 151 abuts against the second heat insulating portion 132 and the limiting portion 152 abuts against the third heat insulating portion 133, the first flange 15 is set in an "L-shaped" shape. In other words, the contact surface between the fixing portion 151 and the second heat insulating portion 132 is set at an angle with the contact surface between the limiting portion 152 and the third heat insulating portion 133 (for example, the two are set vertically in the figure). In this case, if there is a gap between the first flange 15 and the thermal insulation structure 13, a bend will occur, which can increase the difficulty of gas leakage from the gap, thereby optimizing the sealing effect of the first flange 15 sealing the thermal insulation structure 13. Optionally, a sealing element can be provided between the first flange 15 and the thermal insulation structure 13 to further ensure the sealing effect.

[0041] In some embodiments, a gasket is further provided between the limiting portion 152 and the third thermal insulation portion 133. In some embodiments, the limiting cooperation between the limiting portion 152 and the third thermal insulation portion 133 is used to limit the circumferential movement of the process tube 12. When the third thermal insulation portion 133 directly abuts against the limiting portion 152, the third thermal insulation portion 133 or the entire thermal insulation structure 13, or even the process tube 12, is easily broken under the action of the abutment force. By providing a gasket, a buffering effect can be played when the third thermal insulation portion 133 and the limiting portion 152 abut, so as to reduce the damage to the thermal insulation structure 13 and the process tube 12.

[0042] Furthermore, combined with Figure 3, the fixing portion 151 of the first flange 15 is provided with a first cooling pipe 1511, and the limiting portion 152 of the first flange 15 is provided with a second cooling pipe 1521, and the first cooling pipe 1511 and the second cooling pipe 1521 are connected. In other words, the first cooling pipe 1511 and the second cooling pipe 1521 are different parts of the same water channel. The first cooling pipe 1511 and the second cooling pipe 1521 can allow the cooling medium to flow through, and the cooling medium can take away the heat, thereby reducing the temperature of the insulation space 130 and the seal 164. In some embodiments, the wall thickness of the fixing portion 151 between the first cooling pipe 1511 and the second insulation portion 132 is the same as the wall thickness of the limiting portion 152 between the second cooling pipe 1521 and the third insulation portion 133. In this way, the heat can be conducted from the insulation structure 13 to the first flange 15 in a more uniform path, thereby increasing the uniformity of heat dissipation. In some embodiments, the cross section of the whole composed of the first cooling pipe 1511 and the second cooling pipe 1521 is set in an "L-shape".

[0043] In some embodiments, the outer diameter of the first thermal insulation part 131 is larger than the outer diameter of the process tube 12, and the diffusion device 1 further includes a stopper 111 disposed on the heating furnace body 11, and the first thermal insulation part 131 abuts against the stopper 111. The outer diameter of the first thermal insulation part 131 is larger than the outer diameter of the process tube 12, and a step structure can be formed at the connection between the process tube 12 and the first thermal insulation part 131. The step structure can abut against the stopper 111, thereby limiting the movement of the process tube 12 toward the furnace tail of the heating furnace body 11. Since the aforementioned first flange 15 can limit the movement of the process tube 12 toward the furnace mouth of the heating furnace body 11. Therefore, the above method can limit the movement of the process tube 1 toward both the furnace mouth and the furnace tail of the heating furnace body 11, which is beneficial to improving the working stability of the diffusion device 1.

[0044] In some embodiments, the diffusion device 1 further includes a second flange 16, which is disposed between the first flange 15 and the fixing plate 14, and is connected to the fixing plate 14. The second flange 16 and the fixing plate 14 may be directly connected or indirectly connected, which is not specifically limited herein. For example, the second flange 16 may be indirectly connected to the fixing plate 14 through a pad 17 or a buffer pad 18 described later.

[0045] In some embodiments, the diffusion device 1 further includes a seal 164, which is disposed between the second flange 16 and the second thermal insulation portion 132. The seal 164 between the second flange 16 and the second thermal insulation portion 132 can increase the sealing effect of the second flange 16.

[0046] Specifically, in some embodiments, the second flange 16 is provided with a convex portion 161 extending toward the second heat insulating portion 132, and the second heat insulating portion 132, the second flange 16 and the convex portion 161 are surrounded to form an accommodation space, and the accommodation space is used to accommodate the seal 164. The seal 164 can seal the space between the second flange 16 and the second heat insulating portion 132. On the one hand, the convex portion 161 can limit the position of the seal 164 to prevent it from escaping from the accommodation space; on the other hand, the convex portion 161 can squeeze the seal 164, thereby reducing the elongation deformation of the seal 164 in the axial direction of the process pipe 12, and try to make the elongation deformation more located between the second heat insulating portion 132 and the second flange 16, thereby improving the sealing effect of the seal 164.

[0047] In some embodiments, the accommodating space is formed with an opening toward the first flange 15. In other words, the convex portion 161, the second heat insulating portion 132 and the second flange 16 form a "U-shaped" structure with an opening toward the first flange 15. The first flange 15 is provided with an abutting portion 153 toward the second flange 16, and the abutting portion 153 extends from the opening into the accommodating space for abutting the sealing member 164. The abutting portion 153 can compress the sealing member 164 in the accommodating space, so that the sealing member 164 undergoes contraction deformation in the axial direction of the process pipe 12, so that the sealing member 164 can generate more elongation deformation between the second heat insulating portion 132 and the second flange 16, thereby playing a better role in sealing the gap between the second flange 16 and the second heat insulating portion 132. In summary, the abutting portion 153 can cooperate with the convex portion 161, so that the sealing member 164 produces more elongation deformation between the second flange 16 and the second heat insulating portion 132, thereby better sealing the gap and improving the sealing effect.

[0048] In some embodiments, a partition 163 is further provided in the accommodation space, and the partition 163 can separate the accommodation space into two parts. The space between the partition 163 and the protrusion 161 can be used to accommodate the seal 164. The space between the partition 163 and the abutment portion 153 can also be used to accommodate the seal 164. In the above manner, multiple sealing effects can be achieved. In addition, the partition 163 is not connected to the second flange 16 or the second heat insulation portion 132, so that the extrusion of the abutment portion 153 can be transmitted through the partition 163, so that both seals 164 can be squeezed, further achieving the aforementioned technical effects.

[0049] In some embodiments, the second flange 16 is provided with a third cooling pipe 162. The third cooling pipe 162 can accommodate a cooling medium, so that the aforementioned sealing member 164 can be cooled, thereby extending the service life of the sealing ring 191.

[0050] In some embodiments, the diffusion device 1 further includes a pad 17 and a buffer pad 18 stacked in the axial direction of the process tube 12, the pad 17 and the buffer pad 18 are arranged between the second heat insulation part 132 and the fixed plate, the pad 17 is installed on the fixed plate 14, the buffer pad 18 is installed on the pad 17, and the buffer pad 18 is located between the pad 17 and the second heat insulation part 132. A plurality of pads 17 can be arranged at intervals around the axial direction of the process tube 12. A plurality of buffer pads 18 can be arranged at intervals around the axial direction of the process tube 12. The pad 17 can realize the connection between the fixed plate 14 and the first flange 15 or the second flange 16. By adjusting the size of the pad 17, the installation position of the first flange 15 and the second flange 16 can also be adjusted, thereby ensuring a better sealing effect. The second heat insulation part 132 abuts against the buffer pad 18. The buffer pad 18 can allow the second heat insulation part 132 to produce a small amount of displacement, thereby reducing the second heat insulation part 132 from breaking during the movement.

[0051] In other embodiments, the cushion block 17 may be arranged in an annular shape. In other words, the cushion block 17 may be an annular flange structure. Optionally, the buffer pad 18 may also be arranged in an annular shape.

[0052] In some embodiments, the diffusion device 1 further includes a door body 19, which is nested and connected with the heat insulation structure 13 to achieve the sealing of the pipe mouth of the process pipe 12. At least a portion of the door body 19 abuts against the first flange 15, and a sealing ring 191 is provided between the door body 19 and the first flange 15. The door body 19 is also provided with a fourth cooling pipe 192, and the fourth cooling pipe 192 is used to cool the sealing ring 191. The sealing ring 191 can seal the gap between the door body 19 and the first flange 15. The fourth cooling pipe 192 can pass a cooling medium, thereby cooling the sealing ring 191 and extending the service life of the sealing ring 191.

[0053] In some embodiments, the door body 19 is provided with a heat insulation cover extending into the heat insulation structure 13. The heat insulation cover may be filled with heat insulation material. The heat insulation cover and the heat insulation material can reduce the heat loss from the process pipe 12 from the heat insulation structure 13 and the door body 19, so as to reduce the temperature of the heat insulation structure 13, the first flange 15, the second flange 16 and the door body 19.

[0054] Combination Figure 6, description of the first cooling pipe 1511, the second cooling pipe 1521, the third cooling pipe 162 and the fourth cooling pipe 192. Take the first cooling pipe 1511 as an example. The first cooling pipe 1511 is arranged in the first flange 15. The first flange 15 is also provided with an inlet joint 154 and a discharge joint 155. The cooling medium can enter the first cooling pipe 1511 from the inlet joint 154, and the cooling medium can be discharged from the first cooling pipe 1511 from the discharge joint 155. In the first cooling pipe 1511, a spacer 156 is arranged at a position between the inlet joint 154 and the discharge joint 155. The spacer 156 can separate the cooling medium entering the first cooling pipe 1511 from the heated medium discharged from the first cooling pipe 1511, so as to realize the circulation of the cooling medium in the first cooling pipe 1511. The structure and design of the second cooling pipe 1521, the third cooling pipe 162 and the fourth cooling pipe 192 are similar to those of the first cooling pipe 1511, and will not be repeated here.

[0055] Through the above method, on the one hand, the movement of the process pipe 12 in the axial direction can be limited, higher fixation can be achieved, and the risk of cavity fragmentation can be reduced; on the other hand, the insulation structure 13, the seal 164, the first flange 15, the second flange 16 and the sealing ring 191 can be cooled, thereby extending the service life of the seal 164 and the sealing ring 191.

[0056] The above are merely embodiments of the present application and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A diffusion device, characterized in that: include: Heating the furnace body; A process pipe, the heating furnace body is sleeved outside the process pipe; a heat-insulating structure fixedly connected to one end of the process pipe, the heat-insulating structure comprising a first heat-insulating portion and a second heat-insulating portion arranged at intervals, and a third heat-insulating portion connecting the first heat-insulating portion and the second heat-insulating portion; the first heat-insulating portion is connected to the process pipe, and a heat-insulating space is formed between the first heat-insulating portion and the second heat-insulating portion; A first flange is sleeved outside the thermal insulation structure.

2. The diffusion device according to claim 1, characterized in that: The first flange includes a limiting portion and a fixing portion, the fixing portion abuts against the second heat insulating portion, the limiting portion abuts against the third heat insulating portion, and a gasket is further provided between the limiting portion and the third heat insulating portion.

3. The diffusion device according to claim 2, characterized in that: The fixing portion is provided with a first cooling pipeline, the limiting portion is provided with a second cooling pipeline, and the first cooling pipeline is communicated with the second cooling pipeline.

4. The diffusion device according to claim 1, characterized in that: A cooling pipeline is arranged in the heat-insulating space, and the cooling pipeline is used for cooling medium to flow through.

5. The diffusion device according to claim 1, characterized in that: The outer diameter of the first heat insulating portion is greater than the outer diameter of the process tube. The diffusion device further includes a stopper disposed outside the heating furnace body, and the first heat insulating portion abuts against the stopper.

6. The diffusion device according to claim 1, characterized in that: The diffusion device also includes a fixing plate and a second flange. The fixing plate is sleeved outside the thermal insulation structure. The second flange is arranged between the first flange and the fixing plate. The first flange and the second flange are connected to the fixing plate.

7. The diffusion device according to claim 6, characterized in that: The diffusion device further includes a seal disposed between the second flange and the second thermal insulation portion.

8. The diffusion device according to claim 7, characterized in that: The second flange is provided with a convex portion extending toward the second thermal insulation portion, and the second thermal insulation portion, the second flange and the convex portion are arranged to form an accommodating space, and the accommodating space is used to accommodate the sealing member; the accommodating space is formed with an opening toward the first flange, and the first flange is provided with an abutting portion toward the second flange, and the abutting portion extends from the opening into the accommodating space for abutting against the sealing member.

9. The diffusion device according to claim 6, characterized in that: The second flange is provided with a third cooling pipeline.

10. The diffusion device according to any one of claims 6 to 9, characterized in that: The diffusion device also includes a pad and a buffer pad stacked in the axial direction of the process tube, the pad and the buffer pad are arranged between the second thermal insulation part and the fixed plate, the pad is installed on the fixed plate, the buffer pad is installed on the pad, and the buffer pad is located between the pad and the second thermal insulation part.

11. The diffusion device according to claim 1, characterized in that: The diffusion device also includes a door body, which is nested and connected to the insulation structure to achieve sealing of the pipe mouth of the process pipe; at least a portion of the door body is in contact with the first flange, a sealing ring is arranged between the door body and the first flange, and the door body is also provided with a fourth cooling pipe for cooling the sealing ring.

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