Electric heater and semiconductor exhaust gas treatment device using same

Abstract

An electric heater (10) of a semiconductor exhaust gas treatment device comprises: a cylindrical protective tube (12) comprising a heat-resistant metal; a heating resistor (14); and an insulating holding member (16). The heating resistor (14) is inserted into the protection tube (12); and an insulating holding member (16) provided at the bottom (12a) of the protective tube (12) and holding the insertion end (14t) of the heating resistor (14) so as to coincide with the center line (CL) of the protective tube (12).

Description

Technical Field

[0001] The present invention relates to an electric heater capable of being used for a long time at a high temperature of 1000° C. or higher and a semiconductor exhaust gas treatment device using the heater. Background Art

[0002] Since the global warming potential (GWP) of various fluorine compound gases (hereinafter referred to as "PFCs, etc.") used in the manufacturing processes of semiconductors, liquid crystals, etc. is thousands to tens of thousands times higher than that of CO2, and their atmospheric lifetime is also thousands to tens of thousands of years longer than that of CO2 (i.e., they are stable compounds that are extremely difficult to decompose), their impact is very large even when emitted into the atmosphere in small amounts.

[0003] Therefore, semiconductor exhaust gas containing such PFCs is thermally oxidized and decomposed by a semiconductor exhaust gas treatment device including an inlet scrubber, an outlet scrubber, and an exhaust gas treatment tower arranged between the inlet scrubber and the outlet scrubber, and then discharged into the atmosphere (for example, refer to Patent Document 1).

[0004] Here, in the conventional electrically heated semiconductor exhaust gas treatment device, Fig. 9 The electric heater 1 shown in the figure performs thermal oxidation decomposition on the semiconductor exhaust gas.

[0005] Conventional electric heater 1 is suspended from the top of the exhaust gas treatment tower so as to surround the exhaust gas inlet passage. Highly oxidizing and highly corrosive semiconductor exhaust gas flowing in the exhaust gas treatment tower flows while contacting the outer surface of electric heater 1 maintained at a high temperature.

[0006] Therefore, in order to protect the heating resistor 4 from the semiconductor exhaust gas, the heating resistor 4 is housed in a metal outer tube 2 having excellent heat resistance and corrosion resistance. In addition, in order to insulate the heating resistor 4 from the metal outer tube 2, a ceramic inner tube 3 is arranged between the two, and the protection tube of the heating resistor 4 is a double tube.

[0007] As the heating resistor 4, a metal wire such as a nickel-chromium alloy wire or a Kanthal wire (registered trademark of Sandvik AB; the same below) wire, or a heating resistor formed by winding SiC into a spiral shape, or a heating resistor formed into a U shape or a W shape formed by combining three heating resistors for use in a three-phase power supply. Fig. 9 In the explanatory diagram of , a spiral heater is shown as a representative example.

[0008] The heating resistor 4 is suspended from the upper end opening toward the bottom in a manner that the center is aligned with the ceramic inner tube 3, and is inserted in a manner that power can be supplied from one side. The insertion end of the heating resistor 4 is free relative to the bottom of the ceramic inner tube 3. Air exists inside the electric heater 1.

[0009] When the heating resistor 4 is made of SiC, when it is kept at a high temperature by passing electricity in an oxygen-containing atmosphere (air), SiO2 formed by oxidation moves from the surface of the SiC heating resistor 4 to the inside, and the resistance value gradually increases until the end of its life (reaches its life).

[0010] The electric heater 1 allows current to flow in the heating resistor 4 through the wires 5, 5 respectively connected to the ends of the spiral heating resistor 4 to generate heat, thereby heating the temperature inside the exhaust gas treatment tower to a high temperature of more than 1000°C (for example, 1300°C to 1450°C), and utilizes the heat to thermally oxidize and decompose PFCs and the like passing through the exhaust gas treatment tower.

[0011] Prior Art Literature

[0012] Patent Literature

[0013] Patent Document 1: Japanese Patent Application Publication No. 2004-349442 Summary of the invention

[0014] Problems to be solved by the invention

[0015] However, in a semiconductor exhaust gas treatment device using such an electric heater 1, when the electric heater 1 is used to generate heat at a temperature far exceeding 1000° C. (for example, 1350° C. or above) or when it is operated for a long time,

[0016] (1) Due to the reflection from the ceramic inner tube 3 arranged close to the heating resistor 4, the heating resistor 4 is overheated, especially in the central part, and the heating resistor 4 is overheated. Fig. 9 In addition, when the center lines of the heating resistor 4 and the ceramic inner tube 3 are slightly offset, the warping occurs particularly significantly. As a result, the portion of the heating resistor 4 is close to the inner tube 3, and therefore, there is a problem that oxidation of the portion progresses to a greater extent than usual.

[0017] (2) Since the ceramic inner tube 3 is weak in thermal shock resistance, it cannot withstand the rapid temperature change of the electric heater 1 caused by the on / off switching of the heating resistor 4 during operation / stop, and may be damaged in a short time.

[0018] (3) In addition, the presence of the ceramic inner tube 3 not only deprives the heat from the heating resistor 4 by an amount corresponding to its heat capacity, but also deteriorates the heat transfer to the outer tube 2.

[0019] (4) In addition, since the interior of the electric heater 1 is an atmosphere containing oxygen (air), there is also a problem that the life of the SiC heating resistor 4 is shortened due to the above-mentioned oxidation. In addition, since the interior of the electric heater 1 is an atmosphere containing oxygen (air), the inner surface of the outer tube 2 exposed to high temperature for a long time is oxidized, and metal oxide powder is generated and accumulated at the bottom of the outer tube 2. This may also cause a short circuit or disconnection by contacting the SiC heating resistor 4.

[0020] The main object of the present invention is to solve the above-mentioned problems and to provide an electric heater that can be used stably for a long period of time at a high temperature exceeding 1000°C.

[0021] Solutions to Solve Problems

[0022] The invention described in claim 1 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, characterized in that:

[0023] The electric heater 10 of the semiconductor exhaust gas treatment device 22 is composed of a cylindrical protection tube 12, a heating resistor 14 and an insulating holding member 16.

[0024] The cylindrical protection tube 12 is made of heat-resistant metal;

[0025] The heating resistor 14 is inserted into the protection tube 12;

[0026] The insulating holding member 16 is provided at the bottom portion 12 a of the protection tube 12 , and holds the insertion end portion 14 t of the heating resistor 14 aligned with the center line CL of the protection tube 12 .

[0027] As the rod-shaped heating resistor 14, there is a heating resistor wound in a spiral shape ( Figure 1 (a)) A heating resistor formed into a U shape ( Figure 1 (b)), or a heating resistor for a three-phase power supply formed by connecting three rod-shaped members at the ends, etc., a heating resistor of a shape corresponding to the application ( Figure 4 (b)).

[0028] Technical solution 2 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, which is the holding member 16 that can adapt to the heating resistor 14 wound in a spiral shape. According to the "holding member 16" of technical solution 1 (embodiment 1: Figure 1 (a) Figure 2 , Figure 3 (a), (b)), characterized in that

[0029] The heating resistor 14 has a rod-like shape in which the heating portion 14a extending from the non-heating portion 14a is wound in a spiral shape.

[0030] The retaining member 16 is composed of a base portion 16a and an end position retaining portion 16b, wherein the base portion 16a has an outer diameter substantially equal to the inner diameter of the bottom portion 12a of the protective tube 12, and the end position retaining portion 16b extends upward from the base portion 16a, is thinner than the inner diameter of the heating resistor 14, and is inserted into the insertion end portion 14t of the heating resistor 14.

[0031] Technical solution 3 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, which is applicable to a heating resistor 14 ( Figure 1 (a)) The heating resistor 14 is formed into a U shape ( Figure 1 (b)), or a heating resistor 14 for a three-phase power supply formed by connecting three rod-shaped members at the ends ( Figure 4 (b) The holding member 16 of various heating resistors 14, according to the "holding member 16" of claim 1 (embodiment 2: Figure 4 (a), (b)), characterized in that

[0032] The retaining member 16 is composed of a cup-shaped member with a bottom whose upper surface is open, and has an outer diameter substantially equal to the inner diameter of the bottom 12a of the protective tube 12, and an inner diameter larger than the outer diameter of the insertion end 14t of the heating resistor 14, and has a side wall 16s that accommodates and retains the insertion end 14t of the heating resistor 14 to form an end position retaining portion 16b.

[0033] in addition, Figure 4 This is a diagram of a heating resistor 14 wound in a spiral shape, and as described above, it can also correspond to a heating resistor 14 formed in a U shape or a heating resistor 14 for a three-phase power supply formed by connecting three rod-shaped members at the ends. The same is true for the holding member 16 described in the technical solutions 4, 6, and 7 described later.

[0034] Technical solution 4 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, according to embodiment 3 of the "holding member 16" of technical solution 1 ( Figure 5 ), characterized in that

[0035] The retaining member 16 is composed of a cylindrical member with an open upper surface and a bottom, and the cylindrical member has an outer diameter substantially equal to the inner diameter of the bottom 12a of the protective tube 12, and an inner diameter larger than the outer diameter of the insertion end 14t of the heating resistor 14, and accommodates and retains the insertion end 14t of the heating resistor 14 to form an end position retaining portion 16b.

[0036] Technical solution 5 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, according to embodiment 4 of the "holding member 16" of technical solution 1 ( Figure 6 (a)), characterized in that

[0037] The heating resistor 14 has a rod-like shape in which the heating portion 14a extending from the non-heating portion 14a is wound in a spiral shape.

[0038] The holding member 16 is composed of a base portion 16a having an outer diameter substantially equal to the inner diameter of the bottom portion 12a of the protection tube 12 and an end position holding portion 16b extending upward from the base portion 16a and having a smaller inner diameter than the heating resistor 14 and inserted into an insertion end portion 14t of the heating resistor 14.

[0039] The electric heater 10 of the semiconductor exhaust gas treatment device 22 is also provided with a metal inner tube 13, which has an outer diameter substantially equal to the inner diameter of the protective tube 12, is arranged on the base 16a, covers the inner surface of the protective tube 12, and has better heat resistance than the protective tube 12.

[0040] Technical solution 6 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, according to embodiment 5 of the "holding member 16" of technical solution 1 ( Figure 6 (b), (c)), characterized in that

[0041] The holding member 16 is composed of a cup-shaped member with an open top and a bottom, and has an outer diameter smaller than the inner diameter of the bottom 12a of the protection tube 12 and an inner diameter larger than the outer diameter of the insertion end 14t of the heating resistor 14, and has a side wall 16s that accommodates and holds the insertion end 14t of the heating resistor 14 to form an end position holding portion 16b.

[0042] The electric heater 10 of the semiconductor waste gas treatment device 22 is also provided with a metal inner tube 13, which is inserted between the side wall 16s of the retaining member 16 and the inner surface of the protective tube 12, or is arranged on the side wall 16s of the retaining member 16, has an outer diameter approximately equal to the inner diameter of the protective tube 12, covers the inner surface of the protective tube 12, and has better heat resistance than the protective tube 12.

[0043] Technical solution 7 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, according to embodiment 6 of the "holding member 16" of technical solution 1 ( Figure 7 (a), (b)), characterized in that

[0044] The holding member 16 is composed of a cylindrical member with an open top and bottom, and the cylindrical member has an outer diameter smaller than the inner diameter of the bottom 12a of the protection tube 12 and an inner diameter larger than the outer diameter of the insertion end 14t of the heating resistor 14, and is formed as an end position holding portion 16b for accommodating and holding the insertion end 14t of the heating resistor 14.

[0045] The electric heater 10 of the semiconductor exhaust gas treatment device 22 is also provided with a metal inner tube 13, which is inserted between the retaining member 16 and the inner surface of the protective tube 12, or is arranged on the retaining member 16, has an outer diameter approximately equal to the inner diameter of the protective tube 12, covers the inner surface of the protective tube 12, and has better heat resistance than the protective tube 12.

[0046] Technical solution 8 is an electric heater 10 of a semiconductor exhaust gas treatment device 22, which relates to an improvement of the electric heater 10 described in technical solution 1, and is characterized in that:

[0047] The atmosphere in the protection tube 12 is an inert atmosphere.

[0048] The invention described in claim 9 relates to a semiconductor exhaust gas treatment device 22 ( Figure 8 ), characterized in that

[0049] The semiconductor waste gas treatment device 22 is composed of a waste gas treatment tower 26, an inlet scrubber 24 and an outlet scrubber 28.

[0050] The exhaust gas treatment tower 26 is equipped with an electric heater 10 described in any one of technical solutions 1 to 8 to thermally decompose the semiconductor exhaust gas G;

[0051] The inlet scrubber 24 cleans the semiconductor waste gas G supplied to the waste gas treatment tower 26 with a chemical solution in advance to remove soluble components and dust;

[0052] The outlet scrubber 28 removes harmful components in the semiconductor exhaust gas G decomposed in the exhaust gas treatment tower 26 .

[0053] Effects of the Invention

[0054] according to Figure 1 to Figure 5 In the electric heater 10 (without the metal inner tube 13), the insertion end 14t of the heating resistor 14 is always held at the center CL of the protection tube 12 due to the function of the holding member 16, and the ceramic inner tube 3 for insulation required in the past is not required. As a result, the distance between the heating resistor 14 and the metal protection tube 12 is widened. When the distance between the two is widened, the reflection from the protection tube 12 is weaker than that of the conventional ceramic inner tube 3, and the reheating of the heating resistor 4 caused by the reflection from the protection tube 12 is greatly alleviated, and warping does not occur.

[0055] Furthermore, as described above, since the ceramic inner tube 3 which was required in the past is not required, there is also the advantage of eliminating the damage failure of the inner tube 3 caused by thermal shock, and the radiant heat from the heating resistor 4 is directly transferred to the metal protection tube 12, thereby reducing the heat loss.

[0056] In addition, if Figure 6 , Figure 7 In the case of an electric heater 10 in which a metal inner tube 13 covering the inner surface of a protective tube 12 is provided in place of the ceramic inner tube 3 required in the past, the heat resistance of the material of the metal inner tube 13 is made better than that of the protective tube 12 serving as the outer tube, and in consideration of the cost, the corrosion resistance of the material of the protective tube 12 can be given priority over the heat resistance.

[0057] Furthermore, by making the atmosphere in the protection tube 12 an inert atmosphere, oxidation of the protection tube 12 and the metal inner tube 13 can be significantly suppressed, and the oxides accumulated in the protection tube 12 can be significantly reduced. Furthermore, oxidation of the heating resistor 14 can also be suppressed.

[0058] In the semiconductor exhaust gas treatment device 22 , by using the electric heater 10 as described above, it is possible to significantly reduce malfunctions associated with the electric heater 10 . BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 (a) is a longitudinal sectional view showing an electric heater according to a first embodiment of the present invention, and (b) is a bottom longitudinal sectional view showing an electric heater according to a second embodiment of the present invention.

[0060] Figure 2 yes Figure 1 (a) Cross-sectional view.

[0061] Figure 3 (a) Yes Figure 1 A bottom longitudinal sectional view of a modification example 1, (b) is Figure 1 Bottom longitudinal sectional view of variant example 2.

[0062] Figure 4 (a) is a bottom longitudinal sectional view of an electric heater showing a first modification of the second embodiment of the present invention, and (b) is a bottom longitudinal sectional view of a second modification.

[0063] Figure 5 It is a bottom longitudinal sectional view showing an electric heater according to a third embodiment of the present invention.

[0064] Figure 6 (a) is a bottom longitudinal sectional view of an electric heater showing a fourth embodiment of the present invention, (b) is a bottom longitudinal sectional view of a first modification, and (c) is a bottom longitudinal sectional view of a second modification.

[0065] Figure 7 (a) is a bottom longitudinal sectional view of an electric heater showing a fifth embodiment of the present invention, and (b) is a bottom longitudinal sectional view of a modification of the fifth embodiment.

[0066] Figure 8 This is a schematic diagram showing the semiconductor exhaust gas treatment device of the present invention.

[0067] Fig. 9 This is a longitudinal sectional view showing a conventional electric heater in which warping occurs. DETAILED DESCRIPTION

[0068] Hereinafter, the present invention will be described with reference to the accompanying drawings. Figure 1 (a) is a longitudinal sectional view schematically showing an electric heater 10 according to Embodiment 1 of the present invention. As shown in the figure, the electric heater 10 of the present invention is roughly composed of a protection tube 12, a heating resistor 14, a cap member 15, a holding member 16, and the like.

[0069] The protection tube 12 is made of a heat-resistant metal (eg, SUS310, HASTELLOY), and is a rod-shaped cylindrical member having an open top and a bottom and accommodating the heating resistor 14 therein to protect the heating resistor 14.

[0070] The heating resistor 14 is a heat source of the electric heater 10 and is made of a metal wire such as a nickel-chromium alloy wire or a Kanthal wire or SiC. Taking the heating resistor 14 formed of SiC as an example, two heating portions 14b extending from a pair of non-heating portions 14a in a strip shape are spirally wound at intervals, and the winding ends 14c of the heating portions 14b are connected.

[0071] In other words, the heat generating portion 14b extending in a strip shape from a pair of non-heat generating portions 14a is folded back at the center portion in its longitudinal direction (i.e., the winding end 14c) so that the strip-shaped heat generating portions 14b are substantially parallel to each other and then wound into a spiral shape.

[0072] In addition, as the heating resistor 14, it is also possible to use Figure 1 As shown in (b), a SiC heater formed into a U shape, such as Figure 4 As shown in (b), three rod-shaped resistors are arranged in parallel and their ends are short-circuited to form a three-phase heating resistor 14.

[0073] The non-heating portion 14a of the heating resistor 14 is fixed to the opening 12b of the protection tube 12 at a distance through a pipe head member 15 made of an insulator. Lead wires 18, 18 are connected to the ends of the non-heating portion 14a on the pipe head member 15 side. A power source (not shown) is connected to the heating resistor 14 via the lead wires 18, 18.

[0074] As described above, the holding member 16 holds the insertion end portion 14 t of the heating resistor 14 having various shapes so as to be aligned with the center CL of the protection tube 12 , and various shapes that can be aligned with the heating resistor 14 are conceivable.

[0075] Figure 1 (a) Figure 2 , Figure 3 (a) and (b) are the first embodiment and its modified examples 1 and 2. Figure 1 In the case of (a), the holding member 16 is composed of a disk-shaped base portion 16a and an end position holding portion 16b extending upward from the center of the upper surface of the base portion 16a.

[0076] The outer diameter of the base portion 16a is substantially equal to the inner diameter of the bottom of the protection tube 12. Therefore, if the holding member 16 is provided at the bottom of the protection tube 12, the holding member 16 is fixed to the bottom of the protection tube 12 and radial movement is suppressed.

[0077] The end position holding portion 16b is formed into a conical shape ( Figure 1 (a)), truncated cone (not shown) or cylindrical ( Figure 3 (a)) is inserted into the inner peripheral surface of the insertion end portion 14t of the heating resistor 14. The insertion portion of the end position holding portion 16b is slightly smaller than the inner diameter of the heating resistor 14.

[0078] When the end position holding portion 16 b is conical (truncated cone), a certain portion of the end position holding portion 16 b is formed so as to be in contact with or close to the inner peripheral edge of the insertion end portion 14 t of the heating resistor 14 .

[0079] When the end position holding portion 16b is cylindrical, it is formed to be slightly thinner than the inner diameter of the insertion end portion 14t of the heating resistor 14, and the outer peripheral surface of the end position holding portion 16b is close to the thickness of the inner peripheral surface of the insertion end portion 14t of the heating resistor 14, thereby assuming that warping is suppressed even if it occurs.

[0080] Therefore, the insertion end portion 14 t of the heating resistor 14 is held by the holding member 16 so as to coincide with the center CL of the protection tube 12 .

[0081] As described above, the heating resistor 14 is supported at two points, namely, the non-heating portion 14a is fixed to the opening 12b of the protection tube 12 by the cap member 15, and the insertion end portion 14t is fixed to the bottom of the protection tube 12 via the holding member 16. The entirety of the heat-generating portion 14b faces the inner surface of the protection tube 12 at an equal distance. In addition, since the gap between the outer surface of the heating resistor 14 and the inner surface of the protection tube 12 does not exist as in the conventional ceramic inner tube 3, it is correspondingly widened.

[0082] The interior of the protection tube 12 is filled with an inert gas such as nitrogen or argon, and the atmosphere surrounding the heating resistor 14 is an inert atmosphere. The inert gas may be supplied into the protection tube 12 through a supply pipe (not shown).

[0083] Next, for the above structure Figure 1 (a) Figure 3 (b) The operation of the electric heater 10 of the first embodiment and its modification 1 described above will be described. When the electric heater 10 of this embodiment is used, the lead wires 18, 18 are connected to a power source (not shown) to supply power to the heating resistor 14. Then, the heating resistor 14 starts to generate heat.

[0084] In addition, since the heating resistor 14 is suspended by the pipe head member 15 while maintaining the shape when inserted in the protection tube 12, and its insertion end portion 14t is held by only the holding member 16 in accordance with the center CL of the protection tube 12, the heating portion 14b directly faces the inner surface of the protection tube 12. That is, there is no ceramic inner tube 3 as in the past. Therefore, the distance between the heating portion 14b and the inner surface of the protection tube 12 directly facing each other is longer than the distance between the ceramic inner tube 3 and the heating portion 14b in the past, and the reflection from the separated protection tube 12 is weak, and the warping of the heating resistor 14 does not occur.

[0085] Furthermore, as described above, since there is no ceramic inner tube 3 as in the related art, the heat of the heating resistor 14 directly heats the protection tube 12 , so that heat loss is reduced compared to the related art, and thermal efficiency is improved.

[0086] Furthermore, if the interior of the protection tube 12 is set to an inert atmosphere (eg, a nitrogen atmosphere or an argon atmosphere), oxidation of the heating resistor 14 or oxidation of the inner surface of the protection tube 12 is greatly suppressed, and generation of oxides accumulated at the bottom of the protection tube 12 is greatly reduced.

[0087] Figure 3 (b) Yes Figure 1 In the second modification of the retaining member 16 shown, when the entire structure is conical or pyramidal (or truncated cone or prism shape; not shown), the outer diameter of the bottom surface is substantially equal to the inner diameter of the protection tube 12, and this portion plays the same role as the base portion 16a. Figure 1 (a) The same.

[0088] Figure 1 (b) Figure 4 (a) and (b) are examples in which a cup-shaped member having an open top and a bottom is used in the second embodiment and its first and second modifications of the holding member 16 . Figure 1The holding member 16 of (b) is composed of a disk-shaped base portion 16a and an end position holding portion 16b extending upward from the center of the upper surface of the base portion 16a.

[0089] The outer diameter of the base portion 16 a is substantially equal to the inner diameter of the bottom portion of the protection tube 12 , and the base portion 16 a is fixed to the bottom portion of the protection tube 12 in the same manner as described above to suppress movement in the radial direction.

[0090] The inner diameter of the end position holding portion 16b is formed to match the width of the insertion end portion 14t of the heating resistor 14, and the insertion end portion 14t is fixed to the end position holding portion 16b. Figure 4 The same applies to the case of the three-phase heating resistor 14 in (b).

[0091] Figure 4 The outer diameter of the holding member 16 shown in (a) is substantially equal to the inner diameter of the bottom 12a of the protection tube 12, and the inner diameter of the holding member 16 is formed to be slightly larger than the outer diameter of the insertion end portion 14t of the heating resistor 14, and the insertion end portion 14t of the heating resistor 14 is accommodated in the holding member 16. Therefore, the inner peripheral surface of the side wall 16s of the holding member 16 is close to the outer peripheral surface of the insertion end portion 14t of the heating resistor 14, and forms an end position holding portion 16b that holds the insertion end portion 14t of the heating resistor 14 at the center CL of the protection tube 12.

[0092] In the embodiment of the figure, the inner peripheral surface of the holding member 16 is formed to be parallel to the outer peripheral surface, but it can also be formed into a morning glory shape (not shown) whose inner diameter decreases as it approaches the bottom surface. In this case, a certain part of the inner peripheral surface of the holding member 16 is close to or in contact with the outer peripheral surface of the insertion end portion 14t of the heating resistor 14.

[0093] Figure 5 This is an example of using a cylindrical member in Embodiment 3 of the holding member 16. The outer diameter of the holding member 16 is substantially equal to the inner diameter of the bottom 12a of the protection tube 12, and the inner diameter of the holding member 16 is formed to be slightly larger than the outer diameter of the insertion end 14t of the heating resistor 14. The insertion end 14t of the heating resistor 14 is accommodated and held in the holding member 16. Therefore, in this case, the holding member 16 becomes the end position holding portion 16b.

[0094] In the embodiment of the figure, the inner peripheral surface of the holding member 16 is formed to be parallel to the outer peripheral surface, but in this case, it can also be formed into a morning glory shape (not shown) whose inner diameter decreases as it approaches the bottom surface. In this case, a certain part of the inner peripheral surface of the holding member 16 is close to or in contact with the outer peripheral surface of the insertion end portion 14t of the heating resistor 14.

[0095] Figure 6(a) to (c) are examples of the fourth embodiment and the first and second modifications of the holding member 16. Figure 1 (a) Figure 4 Examples (a) and (b) further include a metal inner tube 13. The metal inner tube 13 is made of a metal material (eg, INCONEL, iron or nickel material containing aluminum alloy steel) having better heat resistance than the protection tube 12 (eg, HASTELLOY, SUS310).

[0096] The retaining member 16 and Figure 1 (a) Figure 4 (a) and (b) are similarly constituted by a cup-shaped member with an open top and a bottom.

[0097] exist Figure 6 In the case of (a), the metal inner tube 13 is provided on the disc-shaped base 16a to cover the entire inner surface of the protection tube 12. The outer diameter of the metal inner tube 13 is substantially equal to the inner diameter of the protection tube 12, and the metal inner tube 13 does not move in the radial direction. Therefore, a sufficient gap is provided between the metal inner tube 13 and the heating resistor 14.

[0098] exist Figure 6 In the case of (b), the outer diameter of the holding member 16 is smaller than the inner diameter of the bottom 12 a of the protection tube 12 , and a gap is formed between the two. The gap is substantially equal to the wall thickness of the metal inner tube 13 .

[0099] The inner diameter of the holding member 16 is slightly larger than the outer diameter of the insertion end portion 14t of the heating resistor 14, and accommodates and holds the insertion end portion 14t of the heating resistor 14. The side wall 16s of the holding member 16 serves as an end position holding portion 16b that holds the insertion end portion 14t of the heating resistor 14 at the center of the protection tube 12. A sufficient gap is provided between the metal inner tube 13 and the heating resistor 14.

[0100] like Figure 4 As described above, the inner surface shape of the holding member 16 may be formed in a tapered shape in which the inner diameter decreases toward the bottom.

[0101] The upper end portion of the metal inner tube 13 is inserted between the tube head member 15 and the protection tube 12 (not shown), and the lower end portion of the metal inner tube 13 is inserted into the gap between the retaining member 16 and the protection tube 12, so that the entire inner surface of the protection tube 12 is protected as described above.

[0102] The holding member 16 holds the heating resistor 14 via the lower end insertion portion of the metal inner tube 13 so as to coincide with the center CL of the protection tube 12 .

[0103] exist Figure 6 (c) is the case when Figure 4In the case of the example where the metal inner tube 13 is added. The outer diameter of the retaining member 16 is substantially equal to the inner diameter of the bottom 12a of the protection tube 12, and no gap is formed between the two. Figure 6 (b) The same.

[0104] The metal inner tube 13 is provided on the side wall 16s of the retaining member 16, covering the entire inner surface of the protection tube 12. The outer diameter of the metal inner tube 13 is substantially equal to the inner diameter of the protection tube 12, and the metal inner tube 13 does not move in the radial direction. A sufficient gap is provided between the metal inner tube 13 and the heating resistor 14.

[0105] Likewise, the inner surface of the holding member 16 may be formed into a tapered shape in which the inner diameter decreases toward the bottom.

[0106] When the metal inner tube 13 is further provided, the material of the protection tube 12 can be selected with priority to corrosion resistance rather than heat resistance in consideration of cost. Furthermore, since the reflection of the metal inner tube 13 is milder than that of the ceramic inner tube 3, even if the metal inner tube 13 is provided, the heating resistor 14 will not be warped. This point will be described later. Figure 7 The same applies to the cases (a) and (b).

[0107] Figure 7 (a) and (b) are the embodiments of the fifth embodiment and the first modification of the holding member 16. Figure 5 In the example, a metal inner tube 13 is further provided. As the metal inner tube 13, as described above, a metal material (for example, alloy steel containing aluminum in INCONEL, iron or nickel material) having better heat resistance than the protection tube 12 (for example, HASTELLOY, SUS310) is used.

[0108] The retaining member 16 and Figure 5 Likewise, it is composed of a cylindrical member with an open top and bottom.

[0109] exist Figure 7 In the case of (a), the outer diameter is smaller than the inner diameter of the bottom 12a of the protection tube 12, and a gap is formed between the two. The gap is substantially equal to the wall thickness of the metal inner tube 13 in the same manner as described above.

[0110] The inner diameter of the holding member 16 is slightly larger than the outer diameter of the insertion end portion 14t of the heating resistor 14, and the insertion end portion 14t of the heating resistor 14 is accommodated and held in the center CL of the protection tube 12. Therefore, the holding member 16 serves as an end position holding portion 16b.

[0111] Moreover, the upper end portion of the metal inner tube 13 is inserted between the pipe head member 15 and the protection tube 12 in the same manner as described above (not shown), and the lower end insertion portion of the metal inner tube 13 is inserted between the retaining member 16 and the protection tube 12 to protect the entire inner surface of the protection tube 12.

[0112] The holding member 16 holds the heating resistor 14 at the center CL of the protection tube 12 via the lower end insertion portion of the metal inner tube 13 .

[0113] Figure 7 (b) is the case when Figure 5 In the case of adding a metal inner tube 13. The retaining member 16 is used Figure 5 Description.

[0114] The outer diameter of the metal inner tube 13 is substantially equal to the inner diameter of the protection tube 12 , and the wall thickness of the metal inner tube 13 is the same as or thinner than the side wall 16 s of the holding member 16 .

[0115] The metal inner tube 13 is provided on the side wall 16 s of the holding member 16 , covering the entire inner surface of the protection tube 12 .

[0116] Next, a semiconductor exhaust gas treatment device 22 using the above-described electric heater 10 will be described.

[0117] The semiconductor exhaust gas treatment device 22 using the electric heater 10 of the present invention is a device for thermally oxidizing and decomposing PFCs and the like in the semiconductor exhaust gas G discharged from a semiconductor, liquid crystal, etc. manufacturing device (not shown). Figure 8 As shown, it is generally composed of an inlet scrubber 24, an exhaust gas treatment tower 26 and an outlet scrubber 28.

[0118] Here, for the semiconductor exhaust gas G introduced into the semiconductor exhaust gas treatment device 22 via the piping 30 from the manufacturing equipment of semiconductors, liquid crystals, etc., most of it is composed of gases other than PFCs, such as N2 and Ar used as carrier gas, purge gas, etc., or O2, H2, NH3, CH4, etc. used as additive gas, and a small amount of various PFCs, etc. are added thereto. As described above, the proportion of PFCs, etc. in the semiconductor exhaust gas G is very small compared to other gases, but as described in the "Background Art", the global warming potential (GWP) of PFCs, etc. is thousands to tens of thousands times that of CO2, which is very large, and the atmospheric lifetime is thousands to tens of thousands of years compared to CO2, so even in the case of a small amount of discharge into the atmosphere, its impact is very large.

[0119] The inlet scrubber 24 is used to remove dust, acidic gases (such as SiH4, SiHF3) and water-soluble PFCs (for example, COF2 expected as a substitute gas) contained in the semiconductor waste gas G introduced into the waste gas treatment tower 26 from the waste gas G. It consists of a straight tube type scrubber body 24a and a nozzle 24b arranged near the top of the scrubber body 24a and spraying alkaline solution, acidic solution or water into a mist.

[0120] The exhaust gas treatment tower 26 is a device for thermally oxidizing and decomposing PFCs and the like in the semiconductor exhaust gas G by electric heating, and is provided with an exhaust gas decomposition treatment chamber 26a having an electric heater 10 disposed therein. In addition, a gas discharge portion 26b is provided at the lower portion of the exhaust gas treatment tower 26, and the gas discharge portion 26b discharges the semiconductor exhaust gas G thermally decomposed in the exhaust gas decomposition treatment chamber 26a.

[0121] The outlet scrubber 28 is used to clean the semiconductor waste gas G that has passed through the waste gas treatment tower 26 and remove dust, acidic gases (such as HF), etc. generated by the thermal decomposition of the waste gas G. It consists of a short tube type scrubber body 28a whose internal space is divided by a plurality of meshes, and a nozzle 28b arranged near the top of the scrubber body 28a and spraying alkaline solution, acidic solution or water into a mist.

[0122] Furthermore, an exhaust gas conveying pipe 32 is installed at the top of the outlet scrubber 28 , and the treated semiconductor exhaust gas G is discharged from the outlet scrubber 28 into the atmosphere through a fan 34 provided in the middle of the exhaust gas conveying pipe 32 .

[0123] According to the semiconductor waste gas treatment device 22 constructed as described above, since the above device is used as the electric heater 10, the temperature in the waste gas treatment tower 26 can be maintained at a high temperature of about 1200°C and continuously operated, and compounds that are particularly difficult to decompose, such as perfluorocarbons, can be decomposed and detoxified. In addition, since the highly durable electric heater 10 is used as described above, the maintenance cycle of the semiconductor waste gas treatment device 22 (especially the maintenance cycle of the electric heater 10) can be extended.

[0124] Description of Reference Numerals

[0125] 1... conventional electric heater, 2... metal outer tube, 3... ceramic inner tube, 4... heating resistor, 5... lead wire, 10... electric heater of the present invention, 12... protection tube, 12a... bottom portion, 12b... opening portion, 13... metal inner tube, 14... heating resistor, 14a... non-heating portion, 14b... heating portion, 14c... winding end, 14t... insertion end portion, 15... pipe head member, 16... holding member, 16a... base portion, 16 b…end position holding portion, side wall…16s, 18…conducting wire, 22…semiconductor exhaust gas treatment device, 24…inlet scrubber, 24a…scrubber body, 24b…nozzle, 26…exhaust gas treatment tower, 26a…exhaust gas treatment chamber, 26b…gas exhaust portion, 28…outlet scrubber, 28a…scrubber body, 28b…nozzle, 30…piping, 32…exhaust gas transport piping, 34…fan, G…semiconductor exhaust gas, CL…center line.

Claims

1. An electric heater for a semiconductor waste gas treatment device, characterized in that: The electric heater of the semiconductor waste gas treatment device is composed of a cylindrical protection tube (12), a heating resistor (14) and an insulating holding member (16). The cylindrical protection tube (12) is made of heat-resistant metal; The heating resistor (14) is inserted into the protection tube (12); The insulating holding member (16) is provided at the bottom (12a) of the protection tube (12) to hold the insertion end (14t) of the heating resistor (14) aligned with the center line (CL) of the protection tube (12).

2. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The heating resistor (14) has a rod-like shape formed by winding a heating portion (14) led out from a non-heating portion (14a) into a spiral shape. The retaining member (16) is composed of a base portion (16a) and an end position retaining portion (16b), the base portion (16a) having an outer diameter substantially equal to the inner diameter of the bottom portion (12a) of the protective tube (12), and the end position retaining portion (16b) extending upward from the base portion (16a), being thinner than the inner diameter of the heating resistor (14) and being inserted into an insertion end portion (14t) of the heating resistor (14).

3. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The retaining member (16) is composed of a cup-shaped member with a bottom whose upper surface is open, and has an outer diameter that is approximately equal to the inner diameter of the bottom (12a) of the protective tube (12), an inner diameter that is larger than the outer diameter of the insertion end (14t) of the heating resistor (14), and a side wall (16s) that accommodates and retains the insertion end (14t) of the heating resistor (14) to form an end position retaining portion (16b).

4. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The retaining member (16) is composed of a cylindrical member with an open upper surface and a bottom, and the cylindrical member has an outer diameter substantially equal to the inner diameter of the bottom (12a) of the protective tube (12), and an inner diameter larger than the outer diameter of the insertion end (14t) of the heating resistor (14), and accommodates and retains the insertion end (14t) of the heating resistor (14) to form an end position retaining portion (16b).

5. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The heating resistor (14) has a rod-like shape formed by winding a heating portion (14) led out from a non-heating portion (14a) into a spiral shape. The retaining member (16) is composed of a base portion (16a) and an end position retaining portion (16b), the base portion (16a) having an outer diameter substantially equal to an inner diameter of a bottom portion (12a) of the protection tube (12), and the end position retaining portion (16b) extending upward from the base portion (16a), being thinner than an inner diameter of the heating resistor (14) and being inserted into an insertion end portion (14t) of the heating resistor (14), The electric heater of the semiconductor waste gas treatment device is also provided with a metal inner tube (13), which has an outer diameter substantially equal to the inner diameter of the protective tube (12), is arranged on the base (16a), covers the inner surface of the protective tube (12), and has better heat resistance than the protective tube (12).

6. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The retaining member (16) is composed of a cup-shaped member with a bottom and an opening on the upper surface, has an outer diameter smaller than the inner diameter of the bottom (12a) of the protection tube (12), has an inner diameter larger than the outer diameter of the insertion end (14t) of the heating resistor (14), and has a side wall (16s) that accommodates and retains the insertion end (14t) of the heating resistor (14) to form an end position retaining portion (16b), The electric heater of the semiconductor waste gas treatment device is also provided with a metal inner tube (13), which is inserted between the side wall (16s) of the retaining member (16) and the inner surface of the protective tube (12), or is arranged on the side wall (16s) of the retaining member (16), has an outer diameter substantially equal to the inner diameter of the protective tube (12), covers the inner surface of the protective tube (12), and has better heat resistance than the protective tube (12).

7. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The holding member (16) is composed of a cylindrical member with an upper surface and a bottom opening, the cylindrical member having an outer diameter smaller than the inner diameter of the bottom (12a) of the protection tube (12) and an inner diameter larger than the outer diameter of the insertion end (14t) of the heating resistor (14), and accommodating and holding the insertion end (14t) of the heating resistor (14) to form an end position holding portion (16b). The electric heater of the semiconductor waste gas treatment device is also provided with a metal inner tube (13), which is inserted between the retaining member (16) and the inner surface of the protective tube (12), or is arranged on the retaining member (16), has an outer diameter substantially equal to the inner diameter of the protective tube (12), covers the inner surface of the protective tube (12), and has better heat resistance than the protective tube (12).

8. The electric heater of the semiconductor exhaust gas treatment device according to claim 1, characterized in that: The atmosphere in the protection tube (12) is an inactive atmosphere.

9. A semiconductor waste gas treatment device, characterized in that: The semiconductor waste gas treatment device is composed of a waste gas treatment tower (26), an inlet scrubber (24) and an outlet scrubber (28). The exhaust gas treatment tower (26) comprises an electric heater (10) according to any one of claims 1 to 8, and thermally decomposes the semiconductor exhaust gas (G); The inlet scrubber (24) cleans the semiconductor waste gas (G) supplied to the waste gas treatment tower (26) with a chemical solution in advance to remove soluble components and dust; The outlet scrubber (28) removes harmful components from the semiconductor waste gas (G) decomposed in the waste gas treatment tower (26).

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