Vapor phase growth equipment

Abstract

To provide a vapor growth device capable of stabilizing attachment of an inner tube that is removably inserted into an exhaust pipe.SOLUTION: A vapor growth device in one embodiment has a reaction vessel in which a film deposition process is performed on a substrate, at least one or more exhaust pipes through which an exhaust gas generated in the film deposition process flows from the reaction vessel, an inner tube that is removably inserted into the exhaust pipe, and a holding section that holds the inner tube attached to the exhaust pipe.SELECTED DRAWING: Figure 2B

Description

[Technical Field]

[0001] FIELD OF THE INVENTION An embodiment of the present invention relates to a vapor deposition apparatus. [Background technology]

[0002] One method for forming high-quality semiconductor films is epitaxial growth, which involves growing a single-crystal film on a wafer (substrate) by vapor phase growth.

[0003] In a vapor phase growth apparatus using this epitaxial growth technology, a wafer is supported and heated on a support within a reaction chamber maintained at atmospheric or reduced pressure. Next, reactive gases, which are the raw materials for film formation, are supplied onto the wafer. Thermal reactions of the reactive gases occur on the wafer surface, resulting in the formation of an epitaxial single crystal film.

[0004] In particular, the exhaust gas after film formation by MOCVD (Metal Organic Chemical Vapor Deposition Method) contains a large amount of reaction by-products. These reaction by-products accumulate in the exhaust pipe connected to the reaction chamber. This requires maintenance work to remove the reaction by-products accumulated in the exhaust pipe. If this maintenance work takes time, the downtime of the vapor phase growth equipment will be extended. Long downtime of the vapor phase growth equipment will result in a decrease in throughput.

[0005] To address this issue, a technology has been proposed in which an inner pipe is attached to the exhaust pipe. In this technology, the inner pipe is detachably inserted into the exhaust pipe. This eliminates the need to remove reaction by-products that have accumulated inside the exhaust pipe, thereby reducing the time required for maintenance work. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 7-283144 Summary of the Invention [Problem to be solved by the invention]

[0007] When the inner pipe is removably inserted into the exhaust pipe as described above, if the inner pipe is not installed stably inside the exhaust pipe, problems such as the inner pipe falling off may occur, for example, if the exhaust pipe is a straight pipe.

[0008] An embodiment of the present invention provides a vapor phase growth apparatus that can stably mount an inner tube that is detachably inserted into an exhaust pipe. [Means for solving the problem]

[0009] A vapor phase growth apparatus according to one embodiment includes a reaction vessel for performing a film formation process on a substrate, at least one exhaust pipe through which exhaust gas generated during the film formation process flows from the reaction vessel, an inner pipe that is removably inserted into the exhaust pipe, and a holding part that holds the inner pipe attached to the exhaust pipe. [Effects of the Invention]

[0010] According to the present invention, it is possible to stably mount an inner pipe that is detachably inserted into an exhaust pipe. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a schematic configuration of a vapor phase growth apparatus according to a first embodiment. [Figure 2A] FIG. 2 is a perspective view showing the appearance of an exhaust unit. [Figure 2B] FIG. 2 is an exploded perspective view of the exhaust unit. [Figure 3] FIG. 2 is a cross-sectional view showing the configuration of an exhaust unit of the vapor phase growth apparatus according to the first embodiment. [Figure 4] FIG. 2 is an enlarged cross-sectional view of a part of the exhaust unit according to the first embodiment. [Figure 5A] FIG. 2 is a plan view of a holding portion according to the first embodiment. [Figure 5B] FIG. 10 is a plan view showing a modified example of the holding portion. [Figure 6]FIG. 10 is a perspective view for explaining the structure of a holding portion 25 according to a second embodiment. [Figure 7A] FIG. 10 is a plan view of a support portion according to a modified example. [Figure 7B] FIG. 10 is a plan view of a support portion according to a modified example. [Figure 7C] FIG. 10 is a plan view of a support portion according to a modified example. [Figure 8] FIG. 11 is a perspective view of a first exhaust pipe according to a third embodiment. [Figure 9A] FIG. 10 is a perspective view of an inner tube according to a third embodiment. [Figure 9B] FIG. 10 is a perspective view of an inner pipe according to a modified example. [Figure 10] FIG. 10 is a perspective view schematically showing an inner tube according to a fourth embodiment. [Figure 11] 10 is a perspective view showing a state in which a part of the inner pipe according to the fourth embodiment is removed from the third exhaust pipe. FIG. [Figure 12] FIG. 10 is a cross-sectional view of an inner tube according to a fourth embodiment. [Figure 13] FIG. 10 is a cross-sectional view showing the shape of the inner tube when the vapor phase growth apparatus according to the fourth embodiment is in operation. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiment.

[0013] (First embodiment) FIG. 1 is a schematic diagram of a vapor phase growth apparatus 1 according to a first embodiment. The vapor phase growth apparatus 1 according to this embodiment is, for example, a vertical, single-wafer epitaxial growth apparatus using the MOCVD method. The vapor phase growth apparatus 1 can grow a single crystal film of a III-V group nitride-based semiconductor, such as GaN (gallium nitride), AlN (aluminum nitride), AlGaN (aluminum gallium nitride), or InGaN (indium gallium nitride), on a wafer (substrate) W. Specifically, the vapor phase growth apparatus 1 has a film formation section 100 and an exhaust section 200. The configuration of each section will be described below.

[0014] The film forming section 100 has a reaction vessel 10, a rotating base 11, a rotating ring 12, a rotating mechanism 13, a gas supply mechanism 14, a support section 15, a gas supply port 16, an exhaust port 17, a shower plate 18, and a heating mechanism 19.

[0015] In the vapor phase growth apparatus 1, film growth is performed in a reaction vessel 10. A support 15 is provided in the reaction vessel 10, on which a wafer W can be placed and which rotates the wafer W in the circumferential direction of the wafer W. The wafer W is, for example, a Si (silicon) wafer or a sapphire wafer. The support 15 may be, for example, a holder having an opening in the center and supporting the substrate at its periphery. Alternatively, a susceptor without an opening may be used as the support 15.

[0016] The support part 15 is provided with, for example, a push-up pin (not shown) for attaching and detaching the wafer W from the support part 15. The support part 15 is provided on a rotating ring 12. The rotating ring 12 is connected to a rotating mechanism 13 via a rotating base 11. The rotating mechanism is, for example, a motor.

[0017] The heating mechanism 19 is provided inside the rotating ring 12. The heating mechanism 19 generates heat by receiving power from an external power source (not shown). As a result, the heating mechanism 19 heats the rear surface of the wafer W. The heating mechanism 19 is, for example, a resistance heater.

[0018] The film forming unit 100 is also provided with a substrate loading port (not shown) and a substrate unloading port (not shown). The substrate loading port is used to load the wafer W into the reaction vessel 10. On the other hand, the substrate unloading port is used to unload the wafer W from the reaction vessel 10.

[0019] For example, a robot hand (not shown) is used to carry in and out the wafer W. The wafer W carried in using the robot hand is supported by a support part 15 inside the reaction vessel 10. Note that the method of carrying in and out the wafer W is not limited to this.

[0020] The gas supply mechanism 14 supplies a process gas into the reaction vessel 10. The gas supply mechanism 14 includes, for example, a gas generator, a gas cylinder, an exhaust pipe, a regulating valve, and a flow rate control device (not shown) such as a mass flow controller.

[0021] The process gas may be, for example, trimethylgallium (TMG), trimethylindium (TMI), trimethylaluminum (TMA), ammonia (NH3) gas, nitrogen (N2) gas, or hydrogen (H2) gas.

[0022] The process gas is supplied from a gas supply port 16 provided at the top of the reaction vessel 10. The process gas supplied into the reaction vessel 10 passes through a shower plate 18 and is then supplied onto the wafer W and used for film formation. Thereafter, excess process gas and reaction by-products generated by film formation are exhausted from an exhaust port 17 provided at the bottom of the reaction vessel 10 to an exhaust section 200. Here, the structure of the exhaust section 200 will be described.

[0023] Fig. 2A is a perspective view showing the appearance of exhaust unit 200. Fig. 2B is an exploded perspective view of exhaust unit 200. As shown in Figs. 2A and 2B, exhaust unit 200 has a base plate 20, a quartz tube 21, a first exhaust pipe 22, a second exhaust pipe 23, an inner pipe 24, and a holder 25. Note that, although exhaust unit 200 according to this embodiment is provided with two of each of the components from quartz tube 21 to holder 25, the number of each component is not limited to two and may be at least one.

[0024] The base plate 20 is an annular plate fixed to the bottom of the reaction vessel 10. Between the inner and outer peripheries of the base plate 20, there are provided a through-hole (not shown) through which the quartz tube 21 passes in the vertical direction, and a screw hole (not shown) for attaching the first exhaust pipe 22.

[0025] The quartz tube 21 is a straight tube that extends vertically from the bottom of the reaction vessel 10 through the base plate 20 to the first exhaust pipe 22. The upper end opening of the quartz tube 21 communicates with the exhaust port 17 of the reaction vessel 10. The lower end opening of the quartz tube 21 communicates with the first exhaust pipe 22.

[0026] The first exhaust pipe 22 is a straight pipe that extends vertically from the quartz pipe 21 to the second exhaust pipe 23. The first exhaust pipe 22 is attached to the base plate 20 by a fixing member such as a threaded bolt. That is, the first exhaust pipe 22 is fixed to the bottom of the reaction vessel 10 via the base plate 20.

[0027] The second exhaust pipe 23 is connected to the first exhaust pipe 22. The second exhaust pipe 23 is a curved pipe that is curved in one direction. Note that the shape of the second exhaust pipe 23 is not limited to a curved pipe, and may be a straight pipe.

[0028] The inner pipe 24 is a straight pipe that is placed inside the first exhaust pipe 22. The outer diameter of the inner pipe 24 is approximately the same as the inner diameter of the first exhaust pipe 22. This allows the outer peripheral surface of the inner pipe 24 to be in close contact with the inner peripheral surface of the first exhaust pipe 22. The inner pipe 24 can be manufactured from, for example, a stainless steel pipe with a fluororesin coating applied to its surface.

[0029] Fig. 3 is a cross-sectional view showing the configuration of the exhaust unit 200 of the vapor phase growth apparatus 1 according to the first embodiment. Fig. 4 is an enlarged cross-sectional view of a portion of the exhaust unit 200 according to the first embodiment.

[0030] 4, a groove 211 is formed in the lower part of the outer periphery of the quartz tube 21. An upper end 241 of the inner tube 24 is fitted into this groove 211. As a result, the inner tube 24 is positioned outside the quartz tube 21 at the connecting portion where the upper end of the inner tube 24 and the lower end of the quartz tube 21 meet. This makes it possible to prevent the exhaust gas G from leaking from the quartz tube 21.

[0031] Fig. 5A is a plan view of the holding portion 25 according to the first embodiment, and Fig. 5B is a plan view showing a modified example of the holding portion 25.

[0032] The holding portion 25 shown in Fig. 5A has a protrusion 253 provided along the periphery of the opening 251. The inner pipe 24 is supported within the first exhaust pipe 22 by this protrusion 253 (see Fig. 5). It is preferable that the protrusion 253 be continuous in order to prevent leakage of the exhaust gas G, as will be described later. However, in the holding portion 25 of this embodiment, multiple protrusions 253 may be provided along the periphery of the opening 251, as shown in Fig. 5B.

[0033] In the vapor phase growth apparatus 1 configured as described above, exhaust gas G containing reaction by-products generated by the film formation process in the film formation section 100 flows through the quartz tube 21, the inner tube 24 disposed within the first exhaust pipe 22, and the second exhaust pipe 23. In this case, the reaction by-products accumulate in the flow path of the exhaust gas G, requiring maintenance work.

[0034] According to the present embodiment described above, the inner pipe 24 is detachably inserted into the first exhaust pipe 22. At this time, the upright position of the inner pipe 24 is held by the holding portion 25. This makes it possible to stabilize the installation state of the inner pipe 24 inside the first exhaust pipe 22.

[0035] Furthermore, in this embodiment, the inner pipe 24 is disposed inside the first exhaust pipe 22. Therefore, during maintenance work, the inner pipe 24 can be pulled out from the quartz pipe 21, eliminating the need to remove the bolts 26 that secure the first exhaust pipe 22 to the base plate 20. In other words, there is no need to remove the first exhaust pipe 22. This reduces the time required for maintenance work.

[0036] Furthermore, when the inner tube 24 from which the reaction by-products have been removed is inserted back into the first exhaust pipe 22, the upper end 241 of the inner tube 24 is fitted into the groove 211 of the quartz tube 21, thereby preventing leakage of the exhaust gas G. Furthermore, the upper end 241 of the inner tube 24 is fixed to the quartz tube 21, and the lower end of the inner tube 24 is supported by the protrusion 253 of the holder 25. This further strengthens the holding function of the inner tube 24.

[0037] Therefore, according to this embodiment, in addition to improving the mounting stability of the inner pipe 24 in the first exhaust pipe 22, it is also possible to prevent the exhaust gas G from leaking from the quartz pipe 21.

[0038] (Second embodiment) Fig. 6 is a perspective view for explaining the structure of a holding portion 25 according to the second embodiment. In Fig. 6, the same components as those in the first embodiment described above are given the same reference numerals, and redundant explanations will be omitted.

[0039] As shown in Fig. 6, the retaining portion 25 according to this embodiment is disposed at the connecting portion between the first exhaust pipe 22 and the second exhaust pipe 23. The retaining portion 25 has an opening 251 through which exhaust gas G passes, and two wires 252 that cross each other so as to divide the internal space of the opening 251. The inner pipe 24 disposed within the first exhaust pipe 22 is supported by the two wires 252. Note that the retaining portion 25 need only have a structure that can hold the inner pipe 24 attached within the first exhaust pipe 22, and is not limited to the structure shown in Fig. 6.

[0040] 7A to 7C are plan views of holding portion 25 according to modified examples. In holding portion 25A shown in Fig. 7A, one wire 252 is provided in opening 251. In holding portion 25B shown in Fig. 7B, multiple wires 252 are strung in stripes within opening 251. Furthermore, in holding portion 25C shown in Fig. 7C, multiple wires 252 are strung in a lattice (mesh) pattern within opening 251.

[0041] In the vapor phase growth apparatus according to this embodiment configured as described above, exhaust gas G also flows through quartz tube 21, inner tube 24 disposed within first exhaust pipe 22, and second exhaust pipe 23. As a result, reaction by-products accumulate in the flow path of exhaust gas G, requiring maintenance work.

[0042] In this embodiment, as in the first embodiment, the inner pipe 24 is disposed inside the first exhaust pipe 22. Therefore, during maintenance work, the inner pipe 24 can be easily removed from the first exhaust pipe 22 by removing the second exhaust pipe 23 and the holding portion 25. In other words, there is no need to remove the first exhaust pipe 22. This reduces the time required for maintenance work.

[0043] In addition, in this embodiment, the surface of the inner pipe 24 is coated with a fluororesin. Therefore, during maintenance work, reaction by-products deposited on the surface can be easily removed, further shortening the maintenance work time.

[0044] The inner pipe 24 from which the reaction by-products have been removed is reinserted into the first exhaust pipe 22. At this time, the inner pipe 24 attached to the inside of the first exhaust pipe 22 is held by the holding portion 25.

[0045] According to the present embodiment described above, the inner pipe 24 is detachably inserted into the first exhaust pipe 22. At this time, the upright position of the inner pipe 24 is held by the holding portion 25. This makes it possible to stabilize the installation state of the inner pipe 24 inside the first exhaust pipe 22.

[0046] (Third embodiment) A vapor phase growth apparatus according to a third embodiment will now be described. In the vapor phase growth apparatus according to this embodiment, the holding mechanism for the inner pipe 24 in the first exhaust pipe 22 is different from those of the first and second embodiments. The holding mechanism for the inner pipe 24 in this embodiment will be described below.

[0047] Fig. 8 is a perspective view of the first exhaust pipe 22 according to the third embodiment. As shown in Fig. 8, in this embodiment, a notch 221 is formed at the lower end of the first exhaust pipe 22. Note that, although two notch portions 221 facing each other are formed in Fig. 8, the number of notch portions 221 is not particularly limited.

[0048] FIG. 9A is a perspective view of an inner pipe 24 according to the third embodiment. As shown in FIG. 9A, in this embodiment, a key-shaped protrusion 242 is formed on the lower part of the outer periphery of the inner pipe 24. When the inner pipe 24 is inserted into the first exhaust pipe 22, the protrusion 242 fits into the notch 221. That is, the protrusion 242 and the notch 221 function as a fitting portion that fits the end of the first exhaust pipe 22 and the outer periphery of the inner pipe 24 together. This allows the inner pipe 24 to be attached to the first exhaust pipe 22. On the other hand, the inner pipe 24 can be removed from the first exhaust pipe 22 by pulling the inner pipe 24 with a force in the vertical direction (the direction of gravity).

[0049] 9B is a perspective view of an inner pipe 24 according to a modified example. A pin-shaped protrusion 243 is formed on the lower part of the outer periphery of the inner pipe 24 shown in FIG. 9B. In this case, the cutout portion 221 of the first exhaust pipe 22 is shaped to fit onto the protrusion 243.

[0050] It is also possible to provide a protrusion at the upper end of the first exhaust pipe 22 and a notch at the end of the inner pipe 24 for fitting. In this case, the protrusion and the notch function as a fitting portion that fits the end of the first exhaust pipe 22 and the outer periphery of the inner pipe 24. The notch may be hook-shaped, and the inner pipe 24 may be held in place by rotating the first exhaust pipe 22 and the inner pipe 24. In this case, the inner pipe 24 can be removed from the first exhaust pipe 22 by rotating it and pulling it with a force in the vertical direction (the direction of gravity).

[0051] According to the present embodiment described above, the cutout 221 provided in the first exhaust pipe 22 fits into the protrusion 242 provided on the inner pipe 24, thereby maintaining the inner pipe 24 in an attached state within the first exhaust pipe 22. That is, the cutout 221 and the protrusion 242 function as a retainer that maintains the attached state of the inner pipe 24. Therefore, in this embodiment, the retainer 25 described in the first and second embodiments is not necessary. As a result, the number of parts to be removed during maintenance is reduced, making it even easier to attach and detach the inner pipe 24. As a result, maintenance time can be further shortened. Furthermore, because there is no part (retainer 25) at the connection portion between the first exhaust pipe 22 and the second exhaust pipe 23, exhaust gas G can flow more smoothly from the inner pipe 24 to the second exhaust pipe 23.

[0052] In this embodiment, the inner pipe 24 is inserted into the first exhaust pipe 22, which is disposed in the vertical direction, but it may also be inserted into a horizontal pipe, which is disposed in the horizontal direction. In this case, the position of the inner pipe 24 can be stabilized by forming a notch in the horizontal pipe that fits into the protrusion of the inner pipe 24.

[0053] (Fourth embodiment) 10 is a perspective view that schematically shows an inner pipe 24 according to a fourth embodiment. In this embodiment, the inner pipe 24 is detachably inserted into a third exhaust pipe 27. The third exhaust pipe 27 is a junction pipe connected to a plurality of second exhaust pipes 23, and is arranged horizontally. The inner pipe 24 according to this embodiment is inserted into the third exhaust pipe 27 in the form of a rolled-up elastic plate. The elastic plate has a thickness of, for example, several mm, and is made of an elastic material to which reaction by-products contained in the exhaust gas G adhere.

[0054] Fig. 11 is a perspective view showing a state in which a portion of the inner pipe 24 according to the fourth embodiment has been removed from the third exhaust pipe 27. As shown in Fig. 11, the inner pipe 24 has an opening 244 formed at the portion where it connects to the second exhaust pipe 23. The exhaust gas G that flows out of the second exhaust pipe 23 flows into the inner pipe 24 through the opening 244.

[0055] FIG. 12 is a cross-sectional view of the inner pipe 24 according to the fourth embodiment. In this embodiment, the inner pipe 24 is inserted into the third exhaust pipe 27 in a rolled shape so that its outer diameter d is smaller than the inner diameter D of the third exhaust pipe 27. The rolled shape of the elastic plate is maintained by a retaining portion 254. The retaining portion 254 connects both ends of the elastic plate. The retaining portion 254 is made of, for example, a shape memory alloy. Note that the retaining portion 254 is not shown in FIGS. 10 and 11.

[0056] 13 is a cross-sectional view showing the shape of the inner pipe 24 when the vapor phase growth apparatus according to the fourth embodiment is operating. When the vapor phase growth apparatus is operating, high-temperature exhaust gas G flows through the inner pipe 24, heating the holding portion 254. If the holding portion 254 is made of a shape-memory alloy, the shape of the holding portion 254 is memorized in advance so that the inner pipe 24 adheres closely to the inner surface of the third exhaust pipe 27 at high temperatures. In other words, at high temperatures, the holding portion 254 deforms so as to return to its original shape.

[0057] As the retaining portion 254 deforms, the inner pipe 24 elastically deforms and expands inside the third exhaust pipe 27. As a result, as shown in Fig. 13, the gap between the outer circumferential surface of the inner pipe 24 and the inner circumferential surface of the third exhaust pipe 27 narrows, and the two come into close contact with each other.

[0058] On the other hand, when the vapor phase growth apparatus is stopped and maintenance work is performed, the temperature of the inner pipe 24 drops to room temperature, and the force tending to deform the holder 254 is lost. As a result, as shown in Fig. 12, the inner pipe 24 is released from tight contact with the third exhaust pipe 27. This allows the inner pipe 24 to be smoothly inserted and removed.

[0059] According to the present embodiment described above, both ends of the inner pipe 24, which has a shape of a rolled elastic plate, are connected by thermally deformable holding portions 254. This makes it possible to maintain a stable installation state of the inner pipe 24 inside the third exhaust pipe 27, and also makes it possible to easily attach and detach the inner pipe 24.

[0060] Furthermore, in this embodiment, by making the inner pipe 24 a spiral spring-like elastic plate, it can also serve as the retaining portion 254. That is, the inner pipe 24 may be elastically deformed and inserted into the third exhaust pipe 27, and after insertion, the inner pipe 24 may expand into the third exhaust pipe 27 to be held in close contact with the inside of the third exhaust pipe 27.

[0061] Although an embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. This embodiment can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. This embodiment and its modifications are included within the scope and spirit of the invention, as well as the invention described in the claims and their equivalents. [Explanation of symbols]

[0062] 1, 2: Vapor phase growth equipment 10: Reaction vessel 21:Quartz tube 22: First exhaust pipe 23: Second exhaust pipe 24: Inner tube 25, 25A, 25B, 25C, 254: Holding part 27: Third exhaust pipe 211: Groove 221: Notch 242, 243:Protrusion 241: Upper end

Claims

1. a reaction vessel for performing a film formation process on a substrate; at least one exhaust pipe through which exhaust gas generated in the film formation process flows from the reaction vessel; an inner pipe that is detachably inserted into the exhaust pipe; a holding portion that holds the inner pipe installed in the exhaust pipe; Equipped with the exhaust pipe includes a first exhaust pipe fixed to the reaction vessel and a second exhaust pipe connected to the first exhaust pipe, the inner pipe is inserted into the first exhaust pipe, The vapor phase growth apparatus, wherein the holding portion is disposed at a connection portion between the first exhaust pipe and the second exhaust pipe.

2. a quartz tube provided between the reaction vessel and the first exhaust pipe; A groove is formed at the end of the outer periphery of the quartz tube, 2. The vapor phase growth apparatus according to claim 1, wherein an end of said inner tube is fitted into said groove.

3. A reaction vessel for performing a film formation process on a substrate; at least one exhaust pipe through which exhaust gas generated in the film formation process flows from the reaction vessel; an inner pipe that is detachably inserted into the exhaust pipe; a holding portion that holds the inner pipe installed in the exhaust pipe; Equipped with the exhaust pipe includes a first exhaust pipe fixed to the reaction vessel and a second exhaust pipe connected to the first exhaust pipe, the inner pipe is inserted into the first exhaust pipe, The holding portion has a fitting portion that fits an end of the first exhaust pipe and an outer periphery of the inner pipe.

4. A reaction vessel for performing a film formation process on a substrate; at least one exhaust pipe through which exhaust gas generated in the film formation process flows from the reaction vessel; an inner pipe that is detachably inserted into the exhaust pipe; a holding portion that holds the inner pipe installed in the exhaust pipe; Equipped with the inner tube is constructed by connecting both ends of a rolled elastic plate with the holding portion, and is inserted into the exhaust pipe in a rolled shape so that the outer diameter of the inner tube is smaller than the inner diameter of the exhaust pipe.

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