Temperature detector for vaporizers

Abstract

The system can flexibly respond to changes in the required amount of raw material gas and supply the raw material gas accordingly, completely vaporize the supplied liquid raw material without clogging, and continuously supply the raw material gas at the required temperature. , a temperature detector for vaporizers that uses infrared radiation as a heat source To provide. [Solution] The temperature detector 70 is for a vaporizer 10 that uses infrared radiation as a heat source. The temperature detector 70 consists of a graphite infrared absorber 78 that absorbs infrared radiation and is heated, and a temperature detection element 71 embedded in the infrared absorber 78 that detects the temperature of the infrared absorber 78.

Description

Technical Field

[0001] The present invention relates to a vaporizer capable of efficiently and stably vaporizing a liquid raw material used in a semiconductor manufacturing process. Temperature detector for use It relates thereto.

Background Art

[0002] In a semiconductor manufacturing process, there is equipment that vaporizes a liquid raw material to perform a film forming process, such as an oxide film or thin film forming process, and supplies the raw material gas to the next processing apparatus. A vaporizer is used to vaporize a liquid raw material controlled to a constant flow rate and supply the raw material gas to the next processing apparatus. For example, in an oxide film forming process, in order to form an oxide film on the surface of a silicon wafer, a raw material gas for oxide film formation (specifically, an oxidizing gas such as water vapor or hydrogen peroxide vapor) is supplied into a high-temperature oxidation furnace, and an oxide film forming process is performed. Also, as examples using organic compounds, there are TEOS (tetraethoxysilane) and its derivative PhTES (triethoxyphenylsilane).

[0003] In this film forming process, it is required to stably send a raw material gas at a flow rate required at a temperature required by the processing apparatus to the vaporizer. In a film forming process, it is generally performed to change the flow rate of the raw material gas. In a vaporizer, it is necessary to change the amount of heat for vaporizing the liquid raw material in accordance with a change in the flow rate of the liquid raw material. For that purpose, it is necessary to control the power supplied to the heater. In addition, it is also required that the vaporizer completely vaporize the supplied liquid raw material and supply it to the next processing apparatus in a steady state. In this case, it is also necessary that the apparatus shape does not become excessive for complete vaporization of the liquid raw material.

[0004] Conventional vaporizers (Patent Document 1) consist of a cylindrical metal housing extending vertically, a metal disc provided to close the metal housing and having numerous micro-holes penetrating both sides, a liquid raw material supply nozzle suspended toward the disc to supply liquid raw material to the disc surface, and a heater provided on the outer circumference of the housing to heat the housing and the disc. In this vaporizer, liquid raw material is dripped from the liquid raw material supply nozzle onto the disc surface, and the dripped liquid raw material spreads across the entire surface of the disc due to its surface tension, and is efficiently vaporized by the heated disc. The vaporized raw material gas flows downward through the micro-holes of the disc, accompanied by a carrier gas supplied to the housing from above.

[0005] However, in this vaporizer, when a liquid raw material using an organic compound is vaporized, the residue remaining on the surface of the disk that is not vaporized gradually clogs the numerous micropores provided in the disk. Eventually, the amount of liquid raw material that can be vaporized decreases due to clogging, and finally, vaporization becomes impossible due to clogging. In other words, if clogging occurs, the entire amount of supplied liquid raw material cannot be accurately vaporized within the specified time, and the raw material gas cannot be stably supplied to the processing device. Therefore, the vaporizer described in Patent Document 2 was proposed.

[0006] The vaporizer described in Patent Document 2 divides the housing of Patent Document 1 into two housings, an inner and an outer one, with numerous opaque ceramic or corrosion-resistant metal granules housed in the inner housing. The bottom of the inner housing has numerous holes with a larger diameter than the micro-holes provided in the disc of Patent Document 1. The part where the granules are housed becomes the vaporization section for the liquid raw material. The entire housing and granules are heated mainly by heat conduction from a heater.

[0007] The liquid raw material is supplied as droplets onto the granular material from a liquid raw material supply nozzle, and flows down through the gaps between the granular material in one or more streams, wetting the surface of the granular material. Since the granular material is heated through the housing, the liquid raw material flowing down while wetting the surface of the granular material gradually vaporizes. A carrier gas is supplied to the enclosure from above and flows downward through the gaps in the granular material. During this process, the vaporized raw material gas flows out from a hole at the bottom of the internal enclosure and flows toward the next processing device. The heater is controlled so that the liquid raw material is completely vaporized by the time it reaches the bottom of the enclosure. This vaporizer uses granular material as the vaporization layer and makes the hole at the bottom larger than the micropores in Patent Document 1, thereby eliminating the problem of micropore clogging that plagued the vaporizer described in Patent Document 1. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] U.S. Patent No. 5711816 [Patent Document 2] Japanese Patent Publication No. 2001-295050 [Overview of the project] [Problems that the invention aims to solve]

[0009] In the vaporizer described in Patent Document 2, the vaporization section is composed of an opaque spherical body, and the holes at the bottom are larger than the micropores in Patent Document 1. Although this eliminates the clogging problem of the vaporizer described in Patent Document 1, it has the problem of not being able to flexibly respond to increases or decreases in the liquid raw material.

[0010] In other words, this vaporizer is a vaporization section filled with opaque spherical bodies as described above, designed to vaporize the entire amount of supplied liquid raw material as it flows through it. However, if the supply rate of liquid raw material increases and becomes excessive relative to the heat output of the heater, the unvaporized liquid raw material will leak out through the holes at the bottom. The presence of unvaporized liquid results in poor film formation.

[0011] Conversely, if the vaporization section is designed to match the supply rate of the liquid raw material, the size of the vaporization section must be determined to match the maximum supply rate, which could result in the vaporizer itself becoming too large. On the other hand, if the shape of the vaporizer is restricted, the maximum supply rate of the liquid raw material must be restricted. In other words, the vaporizer described in Patent Document 2 could not vaporize large quantities of liquid raw materials, making it difficult to flexibly respond to changes in the required amount of gas.

[0012] In addition, thermocouples are usually installed in the casing to regulate the heater temperature. However, the liquid raw material flowing down the spherical layer flows in one or more streams. If a thermocouple is installed near a flow of lower-temperature liquid raw material, the detected temperature will appear lower, causing the heater to overheat. As a result, the temperature of the raw material gas supplied to the processing device will be higher than the required temperature, and the liquid raw material will also be negatively affected.

[0013] Furthermore, in the vaporizer described in Patent Document 2, the opaque spherical body is heated primarily by heat conduction by the internal casing. As a result, the spherical body in contact with the internal casing becomes hotter, while the spherical body in the center remains cooler due to poor heat transfer, causing temperature unevenness between the inside and outside. As described above, the flow path of the liquid raw material through the spherical body layer is not constant; it may pass through the center or the periphery, causing the vaporization state to fluctuate depending on the flow path of the liquid raw material. Such fluctuations prevent the supply of the raw material gas to the next processing device in a steady state.

[0014] This invention was made in view of the aforementioned conventional problems. The challenge is, To enable flexible supply of raw material gas in response to changes in the required amount of raw material gas in the processing device, and to ensure that the supplied liquid raw material does not clog. By infrared A vaporizer that completely vaporizes the raw material without generating any unvaporized liquid raw materials, and that can continuously supply the raw material gas to the processing device at the required temperature. In the vaporizer A vaporizer in which heater temperature can be measured accurately. Temperature detector for use The purpose is to provide. [Means for solving the problem]

[0015] In order to solve the above problems, the present invention (Claim 1) is Temperature detector 70 structured as follows. A vaporizer body 20 composed of a liquid raw material supply unit 12 that supplies a liquid raw material LM for semiconductor manufacturing, a vaporization unit 22 having a vaporization space K inside that vaporizes the supplied liquid raw material LM, and a raw material gas discharge unit 40 that sends the vaporized raw material gas VG to the next process, spherical bodies 30 filled inside the vaporization unit 22, and The vaporization section 22 is positioned with a gap d1 of width M1 between it and the vaporization section 22. a heater H that emits infrared rays and In the temperature detector 70 used in the above, The temperature detector 70 is characterized by comprising a graphite infrared absorber 78 that is positioned in non-contact with the heater H and the vaporizer body 20 and is heated by absorbing infrared rays from the heater H, and a temperature detection element 71 that is embedded in the infrared absorber 78 and detects the temperature of the infrared absorber 78.

[0016] Deleted

[0026] Deleted

[0027] In the present invention, the vaporizer 10 using infrared radiation as a heat source, As the infrared absorber 78 of the temperature detector 70, graphite having a high absorption rate and high thermal conductivity for infrared rays is adopted. Therefore, the infrared rays incident on the infrared absorber 78 are almost completely absorbed and heat is transferred, and the amount of infrared rays radiated from the heater H can be accurately and quickly measured.

Brief Description of the Drawings

[0028] [Figure 1] This is a longitudinal cross-sectional view of the vaporizer of the present invention (Embodiment 1) as seen from the front. [Figure 2] This is a cross-sectional view taken along line A-A' in Figure 3. [Figure 3] This is a cross-sectional view taken along line B-B' in Figure 1. [Figure 4] (a) is a longitudinal cross-sectional view of a heater used in the vaporizer of the present invention, and (b) is a partial longitudinal cross-sectional view of another heater. [Figure 5] (a) is a plan view of the heater, and (b) is a cross-sectional view taken along line C-C' in Figure 4(a). [Figure 6] (a) is a longitudinal cross-sectional view of the temperature detector used in the vaporizer of the present invention, and (b) is a plan view. [Figure 7] (a) is a magnified view of a portion of the gap between the temperature sensor and the vaporizer body and heater, and (b) is a magnified view of a portion of the gap between the vaporizer body and the heater. [Figure 8] (a) is a partially enlarged cross-sectional view of the straight pipe section of the vaporization unit, and (b) is a partially enlarged cross-sectional view of the bent section. [Figure 9] This is a partial longitudinal cross-sectional view of another example of the liquid supply section of the vaporizer of the present invention. [Figure 10] This is a longitudinal cross-sectional view of Embodiment 2 of the vaporizer of the present invention. [Figure 11] This is a cross-sectional view taken along line D-D' in Figure 10. [Figure 12] This is a longitudinal cross-sectional view of Embodiment 3 of the vaporizer body of the present invention. [Figure 13] This is a longitudinal cross-sectional view of Embodiment 4 of the vaporizer body of the present invention. [Figure 14] This is a longitudinal cross-sectional view of Embodiment 5 of the vaporizer body of the present invention. [Figure 15] This is a longitudinal cross-sectional view of Embodiment 6 of the vaporizer body of the present invention. [Modes for carrying out the invention]

[0029] The present invention will be described below with reference to the drawings. The vaporizer 10 is a device that vaporizes the liquid raw material LM supplied from the upstream side to obtain a raw material gas VG, and supplies this raw material gas VG to various semiconductor manufacturing equipment on the downstream side that uses it. The vaporizer 10 is broadly composed of a vaporizer body 20, a heater H, a temperature detector 70, and a reflective member 28 that acts as a casing to house these components. As mentioned above, there are various liquid raw materials (LM), and they are selected appropriately depending on the raw material gas (VG) used in various semiconductor manufacturing equipment. Here, we will take water, hydrogen peroxide, or TEOS (tetraethoxysilane) and PhTES (triethoxyphenylsilane) as representative examples. These liquid raw materials (LM) efficiently absorb mid-infrared rays in the wavelength range of 2.5 μm to 4 μm. In the case of water, if the film thickness is 10 μm or more, it efficiently absorbs mid-infrared rays in the above range. If the film thickness is 1 mm, it absorbs almost 100% of mid-infrared rays in the above range.

[0030] The liquid raw material LM is supplied to the vaporizer body 20 in the form of a mist, droplets, or liquid. The carrier gas CG may be supplied to the vaporizer body 20 together with the liquid raw material LM, or it may be supplied to the vaporizer body 20 alone without the carrier gas CG. When the liquid raw material LM is supplied to the vaporizer body 20 in the form of a mist, an atomizer such as the one in the atomizer 12a is used (Figure 9).

[0031] The vaporizer body 20 is equipped with various structures to achieve the above objectives, and all are characterized in that a liquid reservoir E into which the liquid raw material LM flows is provided in the vaporization section 22 at a position lower than the flow path R of the liquid raw material LM flowing through the vaporization space K. (Embodiment 1: Figures 1-8) In the vaporizer 10 of Embodiment 1, the liquid raw material LM is supplied to the vaporizer body 20 in liquid or droplet form. The vaporizer body 20 consists of a liquid raw material supply unit 12 that supplies the liquid raw material LM to a vaporization space K, a vaporization unit 22 that has a vaporization space K inside for vaporizing the supplied liquid raw material LM, and a raw material gas discharge unit 40 that sends the vaporized raw material gas VG to the next process.

[0032] In Figure 1, the liquid raw material supply unit 12 and the raw material gas discharge unit 40 are integrated into the vaporizer body 20 with the vaporization unit 22. Of course, as will be described later, there are also cases where the liquid raw material supply unit 12, the raw material gas discharge unit 40, and the vaporization unit 22 are separate components (Figure 9). The vaporizer body 20 is a component made by bending a circular cross-section tube material, such as transparent quartz glass, which transmits infrared rays. The vaporization section 22 in this embodiment is a U-shaped bent portion and is composed of a bent portion 22e and straight pipe portions 22f and 22g extending upward from this bent portion 22e.

[0033] The liquid raw material supply section 12 is integrally connected to one of the straight pipe sections 22f and is formed in an inverted L shape, with the inlet section extending horizontally. The raw material gas discharge section 40 is integrally connected to the other straight pipe section 22g and has an outlet section that extends horizontally. The vaporization section 22, which is U-shaped and consists of a bent section 22e and straight sections 22f and 22g, is filled with spherical bodies 30 made of, for example, transparent quartz that are capable of transmitting infrared rays. The spherical bodies 30 are, for example, spheres with a diameter of 2 mm to 5 mm. The portion of the vaporization section 22 that is filled with spherical bodies 30 is the vaporization space K. The spherical bodies 30 are in point contact with each other, and voids P are formed between the spherical surfaces of the spherical bodies 30, which serve as channels for the liquid raw material LM.

[0034] In the embodiment shown in Figure 1, the vaporization section 22 is bent into a U-shape. However, the shape of the vaporization section 22 is not limited to a U-shape, as will be described later. The bent portion 22e that constitutes the bottom of the vaporization section 22 becomes the liquid reservoir E of the liquid raw material LM. In this invention, it is sufficient that this liquid reservoir E is located lower than the flow path R of the liquid raw material LM flowing through the vaporization space K. Examples include a bent portion 22e located below horizontally extending straight pipe sections 22f and 22g, as described later (Figure 12), an approximately n-shape (Figure 13), a W-shape (Figure 14), and a spiral pipe installed horizontally (Figure 15).

[0035] A porous filter 23f-23g is installed on top of the spherical body 30 filled in the straight pipe section 22f-22g, as needed. The porous filter 23f-23g can be made of any material that is not affected by the liquid raw material LM and can allow it to pass through smoothly. Here, a porous semi-molten silica glass porous body is used, which is formed by melt-joining the contact points of silica glass powder granules in a semi-molten state, so that infrared rays emitted from the heater H can pass through and the vaporizer body 20 can be welded and fixed. Although not shown in the diagram, a cylindrical heater block with a built-in heating element may be attached to the outer circumference of the tubular raw material gas discharge section 40 in order to maintain a constant temperature of the discharged raw material gas VG.

[0036] Transparent quartz glass is used as the material for the vaporizer body 20 and the spherical body 30 because it allows infrared rays emitted from the heater H to pass through, and these infrared rays can penetrate to the center of the vaporization section 22. In this embodiment, the spherical body 30 is used, but it is not limited to a sphere; for example, granular quartz may also be used. This is preferable because it increases the surface area, thereby improving the vaporization efficiency of the liquid raw material. However, materials that chip due to vibration or other external forces and generate particles should not be used.

[0037] Multiple heaters H (two on each side in this embodiment) are erected on both sides of the vaporizer body 20. The straight pipe sections 22f and 22g of the vaporization section 22 and the heaters H are parallel to each other, and it is preferable that the centerlines of the heaters H and the centerlines of the straight pipe sections 22f and 22g coincide front to back and are parallel to each other. The heaters H are configured to cover at least the straight pipe sections 22f and 22g and the bent section 22e of the vaporization section 22, and to radiate infrared rays evenly to them. A gap d1 with a width M1 is provided between each heater H and the side wall 22h of the vaporizer body 20. This blocks heat transfer from the heater H to the vaporizer body 20. However, since gas (air) is present in this gap d1, heat from the heater H is transferred to the vaporizer body 20. Therefore, as will be described later, it is conceivable to use the gap d1 as a passage for gas exchange.

[0038] A first embodiment of heater H is shown in Figure 4(a). Heater H consists of a pair of transparent quartz tubes 80, occluding insulators 82 and 83 provided at both ends of the transparent quartz tubes 80, a connection terminal 85 provided on the upper occluding insulator 82, a heater coil 88 stretched inside the transparent quartz tubes 80, and an auxiliary reflective member 89. For example, Kanthal wire is used for the heater coil 88. The pair of heater coils 88 are connected inside the occluding insulator 83 at the lower end. The upper ends of the heater coils 88 are each connected to the connection terminal 85. An inert gas is sealed inside the transparent quartz tubes 80. If the heater coil 88 is made of Kanthal wire, its peak wavelength is 2.6 μm. The wavelengths at which Kanthal wire has a specific radiant power of 50% or more are in the mid-infrared region of approximately 1.5 μm to 4 μm. A second embodiment of heater H is shown in Figure 4(b). In this case, the heater coil 88 is formed from graphite that has been processed into a zigzag shape. In the case of graphite, it emits infrared radiation similar to that of Kanthal wire.

[0039] Figure 5(b) shows an example in which an auxiliary reflective member 89 is used in heater H. As will be described later, there is a main reflective member 28 surrounding the vaporizer body 20, so this auxiliary reflective member 89 is not necessarily required. This auxiliary reflective member 89 is provided on the back side of the transparent quartz tube 80, that is, on the entire surface opposite the side wall 22h of the vaporizer body 20. The surface of the auxiliary reflective member 89 facing the vaporizer body 20 is a mirror surface 89k.

[0040] The reflective member 28 is a cylindrical member provided to reflect infrared radiation emitted from the heater H toward the vaporization space K. The inner surface of the reflective member 28 is finished to a mirror surface 28k by means of plating or vapor deposition of a metal with high infrared reflectivity (such as gold), or by attaching aluminum foil to achieve a mirror surface 28k. As shown in Figure 3, the reflective member 28 is provided on the outside of the heater H so as to surround the vaporizer body 20. The upper end of the reflective member 28 is attached to the ceiling plate 21, and the lower end is attached to the bottom plate 27. The inner surfaces of the ceiling plate 21 and the bottom plate 27 are also mirror-finished 28k.

[0041] A hole is provided in the bottom plate 27, which serves as the displacement gas supply section 25. A hole is also provided in the top plate 21, which serves as the displacement gas discharge section 26. These allow displacement gas (air) to flow into the internal space of the reflector member 28 where the heater H is located. As a result, the gas (air) surrounding the heater H rises and is discharged from the displacement gas discharge section 26, and ambient air at room temperature flows in from the displacement gas supply section 25, maintaining the space where the heater H is located at the temperature of the displacement gas (air). Consequently, as will be described later, most of the thermal influence of the heater H on the vaporizer body 20 and temperature detector 70 within the internal space of the reflector member 28 is eliminated.

[0042] Figures 1 to 3 show an example considering heat transfer to the vaporizer body 20 within the space where the heater H is located. When the heater H is heated, the temperature of the surrounding gas (air) rises. The side wall 22h of the vaporizer body 20 is heated through this heated gas (air). Therefore, the width M1 of the gap d1 was devised, and the gap d1 was used as a passage for the displacement gas. This can be applied to all embodiments.

[0043] In this case, the width M1 of the gap d1 becomes the issue. As described above, the ambient air flowing in from the displacement gas supply unit 25 rises along the heater H and gradually increases in temperature. If the space between the heater H and the side wall 22h of the vaporizer body 20 (width M1) is close and smaller than the thickness δ of the thermal boundary layer T, the displacement gas that flows along the heater H and is heated by the heater H will come into contact with the side wall 22h of the vaporizer body 20. As a result, the temperature of the side wall 22h will be affected by the heater H. Therefore, as shown in Figure 7(b), if the space between the heater H and the side wall 22h of the vaporizer body 20 (width M1) is greater than the thickness δ of the thermal boundary layer T, then the unheated displacement gas will flow along the side wall 22h between the heated thermal boundary layer T and the side wall 22h, blocking the thermal influence of the heated thermal boundary layer T. This ensures that the influence of the heated thermal boundary layer T in the space where the heater H is located is reliably eliminated.

[0044] The temperature detector 70 consists of a temperature sensing element 71 and an infrared absorber 78. The temperature sensing element 71 has a pair of thermocouple wires 71a and 71b embedded in a stainless steel sheath 74 via an insulating layer 72. In this embodiment, a sheath-shaped infrared absorber 78 is placed over the joint 73 of the thermocouple wires 71a and 71b and in close contact with the sheath 74. Graphite, which has better thermal conductivity than metal, is used for the infrared absorber 78. It is preferable that the infrared absorber 78 be as thin as possible to be sensitive to changes in the infrared radiation it absorbs.

[0045] As shown in Figure 2, the temperature sensor 70 is positioned between the vaporizer body 20 and the heater H, with gaps d2 and d3 of width M2 and M3, such that it does not come into contact with the vaporizer body 20 and the heater H. In the vaporizer body 20, particularly in the straight pipe section 22f on the inlet side of the vaporization section 22, the liquid raw material LM that has passed through the porous filter 23f flows down between the spherical bodies 30 in one or more meandering channels (flow paths R). If the amount of infrared heat from the heater H is sufficient for the liquid raw material LM, the entire amount of liquid raw material LM vaporizes in the straight pipe section 22f on the inlet side. Conversely, if the amount of infrared heat from the heater H is insufficient for the liquid raw material LM, the entire amount of liquid raw material LM does not vaporize in the straight pipe section 22f on the inlet side, and the unvaporized liquid raw material LM accumulates in the bent section 22e.

[0046] The areas where the liquid raw material LM flows or accumulates have a lower temperature than other areas, so if a temperature detector 70 is installed in these areas, the detected temperature will appear lower. If the temperature sensor 70 is installed so as not to be in contact with the vaporizer body 20 and the heater H, it will not be affected by either, will absorb infrared radiation from the heater H and be heated, and will detect the amount of infrared radiation emitted from the heater H.

[0047] Strictly speaking, the widths M2 and M3 of the gaps d2 and d3 are the issue here. As described above, the reflective member 28 incorporates the vaporizer body 20 and the heater H into its interior. The internal temperature of the reflective member 28 and the temperature of the side wall 22h of the vaporizer body 20 rise along the heater H and gradually increase in temperature. As described above, even if cooler outside air flows into the reflective member 28 from the displacement gas supply section 25, passes through the gaps d2 and d3, and exits from the displacement gas discharge section 26 at the ceiling, if the distance (widths M2 and M3) between the infrared absorber 78 of the temperature detector 70 and the heater H or the side wall 22h of the vaporizer body 20 is close and smaller than the thickness δ of the thermal boundary layer T, the heated displacement gas will come into contact with the infrared absorber 78. This will affect the temperature measurement of the temperature detector 70.

[0048] As shown in Figure 7(a), when the gaps d2 and d3 (widths M2 and M3) are larger than the thickness δ of the thermal boundary layer T, the unheated displacement gas flows along the infrared absorber 78 between the heated thermal boundary layer T and the infrared absorber 78, blocking the thermal influence of the heated thermal boundary layer T on the temperature detector 70. This ensures that the influence of the heated thermal boundary layer T within the space where the infrared absorber 78 is located is reliably eliminated. As a result, accurate temperature measurement of the heater H becomes possible.

[0049] Furthermore, as described above, the heater coil 88 of heater H is covered by a transparent quartz tube 80, so the temperature sensor 70 cannot be installed on the heater coil 88. Installing the temperature sensor 70 on the transparent quartz tube 80 would damage the transparent quartz tube 80, so the temperature sensor 70 cannot be installed on the transparent quartz tube 80.

[0050] The temperature sensor 70 is connected to an external infrared heater temperature controller 90. The infrared heater temperature controller 90 is connected to a power supply 91 and controls the power supplied to the heater H according to the output from the temperature sensor 70.

[0051] Next, a method for vaporizing the liquid raw material LM using the vaporizer 10 of the present invention will be described. When the heater H is energized, infrared radiation is emitted radially from the heater coil 88, which has a peak wavelength of 2.6 μm and includes mid-infrared radiation in the region of approximately 1.5 μm to 4 μm, and is shaped like a mountain with a peak wavelength of 2.6 μm. On the side of heater H facing the vaporizer body 20, a considerable portion of the infrared radiation travels toward the vaporizer body 20. The infrared radiation emitted from the rear side is reflected by the auxiliary reflective member 89 on the back of heater H (or by the cylindrical main reflective member 28 if the auxiliary reflective member 89 is not present) and travels toward the vaporizer body 20.

[0052] Since the vaporizer body 20 is made of transparent quartz glass that transmits infrared rays, infrared rays traveling toward the vaporizer body 20 are refracted and pass through the side wall 22h of the vaporizer body 20. Since the inside of the vaporizer body 20 is filled with spherical bodies 30, infrared rays that reach the vaporization space K inside the vaporizer body 20 are refracted and pass through these spherical bodies 30 to the opposite side wall 22h, and are refracted and passed through there as well. To avoid complexity in the diagram, infrared rays are shown as straight lines.

[0053] Most of the infrared radiation that passes through the vaporizer body 20 is reflected by the mirror surface 28k on the opposite side of the cylindrical reflector 28 and passes through the vaporizer body 20 again. The remaining infrared radiation is reflected by the auxiliary reflector 89. The infrared radiation repeats this process instantaneously and infinitely within the cylindrical reflector 28.

[0054] The state of infrared radiation within the vaporization space K of the vaporizer body 20 is uniform because it is the result of an infinite number of instantaneous reflections as described above. When the vaporization space K heats up and reaches a uniform temperature at the set temperature, and the liquid raw material LM becomes ready to vaporize, the liquid raw material LM is supplied to the liquid raw material supply unit 12. The liquid raw material LM flows down through the liquid raw material supply unit 12 onto the porous filter 23f on the inlet side. The flowing liquid raw material LM soaks into the porous filter 23f and seeps out from its underside. A spherical body 30 is in contact with the underside of the porous filter 23f, and the seeped-out liquid raw material LM flows randomly down the surface of the spherical body 30 in one or more streams (flow channels R).

[0055] The spherical bodies 30 support each other through point contact with adjacent spherical bodies 30, forming a roughly triangular void P in plan view, composed of complex concave spherical surfaces between them (Figure 8(a)). Most of the flowing liquid raw material LM wets the surface of the spherical bodies 30 as it flows down, and the remaining liquid raw material LM accumulates in the void P due to the surface tension of the liquid raw material LM, forming a liquid film of the liquid raw material LM. When the film thickness of the liquid raw material LM is 10 μm or more, it efficiently absorbs mid-infrared rays in the 2.5 μm to 4 μm range. In particular, when the film thickness is 1 mm or more, it absorbs almost 100% of the mid-infrared rays.

[0056] The infrared radiation used here is mostly mid-infrared, with wavelengths of 2.5 μm to 4 μm, as described above, including the absorption peak wavelength (3 μm) of the liquid raw material LM. Therefore, some of the mid-infrared radiation that reaches the vaporization section 22 is absorbed by the thin film of liquid raw material LM formed on the surface of the spherical body 30, or by the liquid film of liquid raw material LM accumulated in the void P, and is converted into heat, causing the liquid raw material LM to vaporize. If the thickness of the thin film of liquid raw material LM is insufficient, the infrared radiation will pass through unimpeded. Since the spherical body 30 is made of transparent quartz glass that transmits infrared radiation, the infrared radiation that is not absorbed by the liquid raw material LM passes through the spherical body 30 and exits to the other side.

[0057] Infrared rays that are not absorbed by the liquid raw material LM pass through the spherical bodies 30 filled inside the vaporizer body 20 one after another, and are emitted to the outside by passing through the side wall 22h on the opposite side of the vaporizer body 20. The infrared rays emitted from the vaporizer body 20 are reflected by the mirror surface 28k (or part thereof by the auxiliary reflective member 89) on the opposite side of the reflective member 28, and are directed back towards the vaporizer body 20. In this way, the liquid raw material LM flowing down the vaporization space K (i.e., the straight tube section 22f on the inlet side) is heated mainly by uniform mid-infrared rays, and the liquid raw material LM that has been heated by absorbing these mid-infrared rays gradually vaporizes. On the other hand, the heating of the liquid raw material LM by heat transfer from the spherical bodies 30 through point contact is small.

[0058] If the supply amount of liquid raw material LM is small, as described above, the entire amount of liquid raw material LM vaporizes in the straight pipe section 22f on the inlet side before reaching the bent section 22e. The vaporized raw material gas VG rapidly increases in volume and passes through the bent section 22e and the straight pipe section 22g on the outlet side, and is discharged from the raw material gas discharge section 40 toward the next process.

[0059] If the supply rate of liquid raw material LM is high, or if the supply rate of liquid raw material LM fluctuates during the vaporization process and exceeds the heat supplied by heater H, the liquid raw material LM will not be completely vaporized in the straight pipe section 22f on the inlet side, and the remaining unvaporized liquid raw material LM will accumulate in the bent section 22e. This section is referred to as the liquid reservoir E. The liquid raw material LM accumulated in the liquid reservoir E is heated by infrared radiation and vaporizes in the narrow void P between the spherical bodies 30. Meanwhile, the unvaporized liquid raw material LM continues to flow into the bent section 22e. The presence of the liquid reservoir E prevents leakage of the unvaporized liquid raw material LM, allowing it to vaporize efficiently and rapidly.

[0060] Furthermore, there is a straight pipe section 22g on the outlet side between the liquid reservoir E and the outlet 40d of the vaporizer body 20, and since there is a distance between them, the raw material gas VG rising from the liquid reservoir E will be uniformly heated in this section, regardless of its quantity.

[0061] Next, we will explain temperature measurement. As described above, the liquid raw material LM that flows down the surface of the spherical body 30 gradually vaporizes and flows down the straight pipe section 22f on the inlet side as one or more flows. If the flow rate is high and the liquid raw material LM accumulates in the liquid reservoir E, which is the bent section 22e, the temperature of that part is lower than that of the spherical body 30 and the bent section 22e, so the temperature of the part in contact with the liquid raw material LM will naturally be lower than that of the part not in contact with it. In other words, temperature unevenness will occur in the straight pipe section 22f and the bent section 22e on the inlet side.

[0062] Since the temperature detector 70 is held in a non-contact position (at least at a distance of the thermal boundary layer δ or greater) with respect to the vaporization section 22 and the heater H, it is not affected by temperature variations or the heater H. The temperature detector 70 has a graphite infrared absorber 78 as a sheath-like outer layer. Therefore, infrared radiation incident on the infrared absorber 78 is almost entirely absorbed and converted into heat, and the temperature of this infrared absorber 78 is detected. Since the amount of absorbed infrared radiation is proportional to the amount of infrared radiation emitted by the heater H, the amount of infrared radiation emitted by the heater H can be accurately measured by measuring the temperature of the infrared absorber 78.

[0063] In other words, since temperature detection by this temperature detector 70 relies solely on infrared radiation absorbed by the infrared absorber 78 and not on heat transfer, it is not affected by temperature unevenness in the vaporization section 22 or the heater H, enabling accurate temperature measurement. Furthermore, by making the thickness of the infrared absorber 78 as thin as possible, heat transfer to the joint 73 of the temperature detector 70 becomes faster, improving the responsiveness of temperature control.

[0064] (Modification 1 of Embodiment 1: Figure 9) The above example shows the liquid raw material LM being supplied directly to the vaporizer body 20, but it may also be supplied in mist form. In this case, the main part of the liquid raw material supply unit 12 consists of an atomizer 12a. A liquid raw material supply pipe 12b is provided in the center of the atomizer 12a, and its tip is narrowed into a cone shape to form a spray nozzle 12d. A carrier gas supply pipe 12c is provided on the side of the atomizer 12a. A carrier gas supply passage 12e, which is connected to the spray nozzle 12d and produces a Venturi effect, is provided on the outer circumference of the liquid raw material supply pipe 12b. The space from the spray nozzle 12d to the porous filter 23f on the inlet side is the atomization space S. The atomization space S is not filled with spherical bodies 30.

[0065] When the liquid raw material LM is supplied to the liquid raw material supply pipe 12b and the carrier gas CG is supplied to the carrier gas supply pipe 12c, a Venturi effect occurs, causing the liquid raw material LM to be uniformly dispersed in a mist form from the spray nozzle 12d into the atomization space S. The mist of liquid raw material LM dispersed into the atomization space S is evenly distributed onto the porous filter 23f and flows down towards the spherical body 30 in one or more streams. The process thereafter is the same as in Embodiment 1.

[0066] (Embodiment 2: Figures 10 and 12) This second embodiment differs from the first embodiment in the shape of the vaporizer body 20 and the reflector member 28, and in the position of the heater H relative to the vaporizer body 20. In Figure 3, heaters H are erected at the front and rear of the vaporizer body 20. In contrast, in this modified example 2, heaters H are erected on both sides of the vaporizer body 20. This reduces the front-to-back width of the vaporizer 10, allowing the reflective member 28 to be a thin rectangle in horizontal cross-section, thus making the vaporizer 10 thinner. As a result of this change, the liquid raw material supply section 12 and raw material gas discharge section 40 connected to the straight pipe sections 22f and 22g extend straight upwards beyond the ceiling plate 21. The temperature measuring instrument 70 is installed between the inlet or outlet straight pipe sections 22f and 22g and one of the heaters H. Otherwise, it is the same as in Embodiment 1.

[0067] (Embodiment 3: Figure 12) In Embodiment 3, the vaporizer body 20 has a bent section 22e located below the horizontally extending straight pipe sections 22f and 22g. When the flow rate is high, the liquid raw material LM that has flowed through the gap P of the spherical body 30 in the inlet-side straight pipe section 22f flows into the liquid reservoir E, which is the bent section 22e. There it is heated and vaporized. This is the same as in Embodiment 1. In Figure 12, the bent portion 22e is formed in a small U-shape, but Embodiment 2 is not limited to this shape. It may be connected to the straight pipe portions 22f and 22g, with the lower surface of the boundary portion bulging downwards in a hemispherical shape, and this bulging portion may be used as a liquid reservoir E. Excess liquid raw material LM flowing in from the straight pipe portion 22f on the inlet side will accumulate in this liquid reservoir E.

[0068] (Embodiments 4 and 5: Figures 13 and 14) The vaporizer body 20 of Embodiment 4 is made by bending a transparent quartz tube into a roughly n-shape, while the vaporizer body 20 of Embodiment 5 is made by bending a transparent quartz tube into a W-shape. In this case, the path from the liquid reservoir E to the outlet 40d can be longer than in Embodiment 1, which further promotes uniform heating of the raw material gas VG. Otherwise, it is the same as Embodiment 1.

[0069] (Embodiment 6: Figure 15) The vaporizer body 20 of Embodiment 6 is constructed by bending a transparent quartz tube into a spiral shape, arranging the spiral portion horizontally, and placing a heater H at its center. In this case as well, multiple bends 22e are provided in the spiral portion, which further promotes uniform heating of the raw material gas VG. In this case, the liquid reservoir E is the first bend 22e. In this case as well, the path from the liquid reservoir E to the outlet 40d can be made longer than in Embodiment 1, which further promotes uniform heating of the raw material gas VG. Everything else is the same as in Embodiment 1. [Explanation of Symbols]

[0070] CG: Carrier gas, d1, d2, d3: Gap, E: Liquid reservoir, H: Heater, K: Vaporization space, LM: Liquid raw material, M1, M2, M3: Gap width, P: Void, R: Flow channel, S: Atomization space, T: Thermal boundary layer, VG: Raw material gas, δ: Thickness of thermal boundary layer 10: Vaporizer, 12: Liquid raw material supply unit, 12a: Atomizer, 12b: Liquid raw material supply pipe, 12c: Carrier gas supply pipe, 12e: Carrier gas supply path, 12d: Spray nozzle, 20: Vaporizer body, 21: Ceiling plate, 22: Vaporization unit, 22e: Bent section, 22f·22g: Straight pipe section, 22h: Side wall, 23f·23g: Porous filter, 25: Replacement gas supply unit, 26: Replacement gas discharge unit, 27: Bottom plate, 28: Reflective material, 28k: Mirror surface, 30: Spherical body, 40: Raw material gas discharge section, 40d: Outlet, 70: Temperature detector, 71: Temperature detection element, 71a / 71b: Thermocouple wire, 72: Insulating layer, 73: Joint, 74: Sheath, 78: Infrared absorber, 80: Transparent quartz tube, 82 / 83: Blocking insulator, 85: Connection terminal, 88: Heater coil, 89: Auxiliary reflective material, 89k: Mirror surface, 90: Infrared heater temperature controller, 91: Power supply

Claims

[Claim 1] A temperature detector 70 used in a vaporizer 10, which comprises a vaporizer body 20 composed of a liquid raw material supply unit 12 for supplying liquid raw material LM for semiconductor manufacturing, a vaporization unit 22 having a vaporization space K inside for vaporizing the supplied liquid raw material LM, and a raw material gas discharge unit 40 for sending the vaporized raw material gas VG to the next process, a spherical body 30 filled in the vaporization unit 22, and a heater H that emits infrared rays and is positioned with a gap d1 of width M1 from the vaporization unit 22 for vaporizing the liquid raw material LM, A temperature detector for a vaporizer is characterized by comprising a graphite infrared absorber 78 that is positioned in non-contact with the heater H and the vaporizer body 20 and is heated by absorbing infrared rays from the heater H, and a temperature detection element 71 that is embedded in the infrared absorber 78 and detects the temperature of the infrared absorber 78.

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