vaporizer

Abstract

This vaporizer 10 comprises a vaporizer body 20, spherical bodies 30, and a heater H. The vaporizer body 20 is composed of a liquid raw material supply part 12 that supplies a liquid raw material LM; a vaporization part 22 that has therein a vaporization space K for vaporizing the liquid raw material LM; and a raw material gas discharge part 40 that sends a vaporized raw material gas VG to the next step. The spherical bodies 30 are filled into the vaporization part 22. The heater H radiates infrared rays. The heater H is disposed at a gap d1 from the vaporization part 22. The vaporization part 22 and the spherical bodies 30 are composed of transparent members capable of transmitting the infrared rays. A liquid reservoir E into which the liquid raw material LM flows is provided in the vaporization part 22 at a position lower than a flow path R of the liquid raw material LM flowing in the vaporization space K.

Description

Vaporizer

[0001] This invention relates to a vaporizer capable of efficiently and stably vaporizing liquid raw materials used in semiconductor manufacturing processes.

[0002] Semiconductor manufacturing processes include equipment that vaporizes liquid raw materials for film formation and supplies the resulting raw material gas to the next processing unit, such as in the oxide film or thin film formation process. A vaporizer is used to vaporize liquid raw materials at a controlled flow rate and supply the resulting raw material gas to the next processing unit. For example, in the oxide film formation process, raw material gas for oxide film formation (specifically, oxidizing gases such as water vapor or hydrogen peroxide vapor) is supplied to a high-temperature oxidation furnace to form an oxide film on the surface of a silicon wafer, and the oxide film formation process is carried out. Examples of organic compounds used include TEOS (tetraethoxysilane) and its derivative PhTES (triethoxyphenylsilane).

[0003] In this film deposition process, it is required that the vaporizer be stably supplied with the raw material gas at the temperature and flow rate required by the processing unit. In the film deposition process, it is common practice to change the flow rate of the raw material gas. The vaporizer needs to change the amount of heat required to vaporize the liquid raw material in accordance with the change in the flow rate of the liquid raw material. To do this, it is necessary to control the power supplied to the heater. In addition, the vaporizer is required to completely vaporize the supplied liquid raw material and supply it to the next processing unit in a steady state. In this case, it is also necessary that the shape of the equipment is not excessive for the complete vaporization of the liquid raw material.

[0004] As a conventional vaporizer (Patent Document 1), there is a cylindrical metal casing extending in the vertical direction, a metal disk provided so as to close the metal casing, and a large number of fine holes penetrating through the front and back surfaces. A liquid raw material supply nozzle that is vertically provided toward the disk and supplies liquid raw material to the disk surface, and a heater that is provided on the outer periphery of the casing and heats the casing and the disk. In this vaporizer, the liquid raw material is dropped from the liquid raw material supply nozzle onto the disk surface, and the dropped liquid raw material spreads over the entire disk surface due to its surface tension and is efficiently vaporized by the heated disk. The vaporized raw material gas flows downward from the fine holes of the disk along with the carrier gas supplied from above to the casing.

[0005] However, in this vaporizer, for example, when vaporizing a liquid raw material using an organic compound, residues remaining on the disk surface without being vaporized gradually block the large number of fine holes provided in the disk. Eventually, due to clogging, the amount of liquid raw material that can be vaporized decreases, and finally, it becomes impossible to vaporize due to clogging. In other words, if clogging occurs, it is impossible to accurately vaporize the entire amount of the supplied liquid raw material within a specified time, and it becomes impossible to stably supply raw material gas to the processing device. Therefore, the vaporizer described in Patent Document 2 was proposed.

[0006] The vaporizer described in Patent Document 2 divides the casing of Patent Document 1 into two inner and outer casings, and houses a large number of opaque ceramics or granular bodies made of corrosion-resistant metal in the inner casing. At the bottom of the inner casing, a large number of holes with a larger diameter than the fine holes provided in the disk of Patent Document 1 are provided. The portion where the granular bodies are housed becomes the vaporization part of the liquid raw material. The entire casing and the granular bodies are mainly heated by heat conduction from the heater.

[0007] The liquid raw material is supplied as droplets onto granular material from a liquid raw material supply nozzle, and flows down through the gaps between the granular material in one or more flows, 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 housing from above and flows downward through the gaps between the granular material, and during this process, it flows out downward from a hole at the bottom of the internal housing along with the vaporized raw material gas, and flows toward the next processing device. This heater is controlled so that the liquid raw material is completely vaporized by the time it reaches the bottom of the housing. This vaporizer uses granular material as the vaporization layer and makes the hole at the bottom larger than the micropore in Patent Document 1, thereby eliminating the problem of micropore clogging that occurred in the vaporizer described in Patent Document 1.

[0008] U.S. Patent No. 5,711,816, Japanese Patent Publication No. 2001-295050

[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 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 in Patent Document 2 could not vaporize large quantities of liquid raw material and had difficulty flexibly responding 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] The present invention has been made in view of the aforementioned problems of the conventional invention. The first objective is to provide a vaporizer that can flexibly respond to changes in the amount of raw material gas required by the processing device and supply the raw material gas, completely vaporize the supplied liquid raw material without clogging and without generating unvaporized liquid raw material, and can steadily supply the raw material gas to the processing device at the required temperature. The second objective is to provide a vaporizer in which the heater temperature can be accurately measured in order to achieve the first objective.

[0015] To solve the above problems, the present invention (Claim 1) provides a vaporizer 10 configured as follows: A vaporizer body 20 comprising 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 vaporizes the liquid raw material LM, wherein the heater H is positioned with a gap d1 of width M1 from the vaporization unit 22, the vaporization unit 22 and the spherical body 30 are made of transparent material that transmits infrared rays, and a liquid reservoir E into which the liquid raw material LM flows is provided in the vaporization unit 22 at a position lower than the flow path R of the liquid raw material LM flowing through the vaporization space K.

[0016] Claim 2 is characterized in that, in the vaporizer 10 of Claim 1, the vaporization section 22 is made of a bent pipe.

[0017] Claim 3 is characterized in that the vaporizer 10 of Claim 1 includes a reflective member 28 which is arranged outside the heater H so as to surround the vaporization section 22, and whose inner surface facing the vaporization section 22 is formed as a mirror surface 28k that reflects infrared rays.

[0018] Claim 4 is a heater H provided with an auxiliary reflective member 89 (Figures 3 and 5). In the vaporizer 10 according to claim 1 or 3, the auxiliary reflective member 89 is provided on the side of the heater H opposite to the vaporizer body 20, and the surface of the auxiliary reflective member 89 that reflects infrared rays toward the vaporizer body 20 is a mirror surface 89k.

[0019] Claim 5 relates to the arrangement of the temperature detector 70 (Figure 2). In the vaporizer 10 according to claim 1 or 3, the temperature detector 70 for measuring the amount of infrared radiation is arranged between the vaporization section 22 and the heater H, with gaps d2 and d3 of width M2 and M3 between the vaporizer body 20 and the heater H.

[0020] Claim 6 relates to the specific structure of the temperature detector 70 (Figure 2). In the vaporizer 10 according to claim 5, the temperature detector 70 is characterized by comprising a graphite infrared absorber 78 that absorbs infrared rays and is heated, and a temperature detection element 71 embedded in the infrared absorber 78 for detecting the temperature of the infrared absorber 78.

[0021] According to the present invention (Claim 1), since the vaporization section 22 and the spherical body 30 are made of transparent material that transmits infrared rays, the infrared rays emitted from the heater H pass through them completely. As a result, the liquid raw material LM supplied to the vaporization section 22 is uniformly and directly heated by infrared rays as it flows down between the spherical bodies 30, regardless of the flow path R.

[0022] Furthermore, the vaporization unit 22 is provided with a liquid reservoir E at a position lower than the flow path R of the liquid raw material LM flowing through the vaporization space K. If the amount of liquid raw material LM supplied from the liquid raw material supply unit 12 is large and not all of it vaporizes before reaching the liquid reservoir E, the unvaporized liquid raw material LM will accumulate in the liquid reservoir E. The unvaporized liquid raw material LM accumulated in the liquid reservoir E is heated within it and efficiently vaporizes sequentially without leaking out of the liquid reservoir E. Therefore, a large amount of liquid raw material LM can be efficiently processed in the vaporization unit 22 with a small capacity, and it can flexibly respond to fluctuations in the supply amount of liquid raw material LM.

[0023] In the present invention (Claim 2), since the vaporization section 22 is made of a bent pipe, the bent portion 22e becomes a liquid reservoir E, allowing the vaporizer 10 to flexibly respond to fluctuations in the supply amount of the liquid raw material LM.

[0024] According to the present invention (Claim 3), the infrared radiation emitted from the heater H is reflected repeatedly in countless random directions by the reflective member 28 surrounding the vaporization section 22, so that the transparent vaporizer body 20 and the spherical body 30 are uniformly exposed to infrared radiation throughout. The liquid raw material LM that flows down in streaks through the gaps in the transparent spherical body 30 is then smoothly vaporized by the efficient absorption of mainly infrared radiation.

[0025] According to the present invention (Claim 4), infrared radiation emitted from the heater H to the opposite side of the vaporizer body 20 is reflected towards the vaporizer body 20 by the auxiliary reflecting member 89, and the infrared radiation emitted from the heater H is concentrated towards the vaporizer body 20 by that amount.

[0026] According to the present invention (claim 5), since the temperature detector 70 is positioned in a non-contact manner with respect to the vaporization section 22 and the heater H, the temperature detector 70 can detect temperature without being affected by the vaporization section 22 or the heater H. Temperature detection by the temperature detector 70 relies solely on infrared radiation absorbed by the temperature detector 70, improving the accuracy of temperature detection.

[0027] According to the present invention (claim 6), since graphite, which has a high absorption rate and high thermal conductivity for infrared rays, is used as the infrared absorber 78 of the temperature detector 70, the infrared rays incident on the infrared absorber 78 are almost entirely absorbed and transferred as heat, and the amount of infrared radiation from the heater H can be measured accurately and quickly.

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

[0029] The present invention will now be described 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 generally 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 described above, there are various types of liquid raw materials LM, and they are appropriately selected according to the raw material gas VG used in various semiconductor manufacturing equipment. Here, as representative examples, we will take up water, hydrogen peroxide, or TEOS (tetraethoxysilane) or PhTES (triethoxyphenylsilane). 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 the 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 only the liquid raw material LM may be supplied to the vaporizer body 20 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 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 to 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 is composed of a liquid raw material supply section 12 that supplies the liquid raw material LM to the vaporization space K, a vaporization section 22 that has a vaporization space K inside for vaporizing the supplied liquid raw material LM, and a raw material gas discharge section 40 that sends the vaporized raw material gas VG to the next process.

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

[0033] The liquid raw material supply section 12 is integrally connected to one straight pipe section 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 is drawn out horizontally. The vaporization section 22, which is formed in a U shape by the bent section 22e and the straight pipe sections 22f and 22g, is filled with spherical bodies 30 made of, for example, transparent quartz that are transparent to infrared rays. The spherical bodies 30 are, for example, spheres with a diameter of 2 mm to 5 mm. The part of the vaporization section 22 where the spherical bodies 30 are filled is the vaporization space K. The spherical bodies 30 are in point contact with each other, and a gap P is formed between the spherical surfaces of the spherical bodies 30, which serves as a flow path 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 for 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 sections 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 made by melt-joining the contact parts 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 figure, 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 the discharged raw material gas VG at a constant temperature.

[0036] Transparent quartz glass is used as the material for the vaporizer body 20 and the spherical body 30 because it allows infrared radiation emitted from the heater H to pass through, and the infrared radiation can penetrate to the center of the vaporization section 22. In this embodiment, a sphere is used for the spherical body 30, 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 are not 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 to position them so 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 these. 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 heaters H to the vaporizer body 20. However, since gas (air) is present in this gap d1, heat from the heaters 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] The 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 reflecting 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. When the heater coil 88 is Kanthal wire, its peak wavelength is 2.6 μm. The wavelength at which Kanthal wire has a specific radiant output of 50% or more is the mid-infrared region of approximately 1.5 μm to 4 μm. The second embodiment of heater H is shown in Figure 4(b). In this case, the heater coil 88 is made of graphite that has been processed into a zigzag pattern. Graphite also 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 rays 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 (for example, gold), or by attaching aluminum foil to it. 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. A ceiling plate 21 is attached to the upper end of the reflective member 28, and a bottom plate 27 is attached to its lower end. The inner surfaces of the ceiling plate 21 and the bottom plate 27 are also mirror surfaces 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 at room temperature that flows 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 made larger than the thickness δ of the thermal boundary layer T, 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. As a result, the influence of the heated thermal boundary layer T in the space where the heater H is located will be reliably eliminated.

[0044] The temperature detector 70 is composed of a temperature detection element 71 and an infrared absorber 78. The temperature detection element 71 is one in which a pair of thermocouple element wires 71a and 71b, which are the temperature detection element 71, are embedded in a stainless sheath 74 via an insulating layer 72. In this embodiment, a sheath-shaped infrared absorber 78 is covered so as to surround the joint portion 73 of the thermocouple element wires 71a and 71b and to be in close contact with the sheath 74. The infrared absorber 78 is made of graphite, which has a better thermal conductivity than metal. The infrared absorber 78 preferably has a thinner thickness so as to be more sensitive to changes in the absorbed infrared rays.

[0045] As shown in FIG. 2, the temperature detector 70 is arranged such that gaps d2 and d3 having widths M2 and M3 are provided between the vaporizer body 20 and the heater H so as to be non-contact with the vaporizer body 20 and the heater H. In the straight pipe portion 22f on the inlet side of the vaporizer body 20, particularly the vaporization portion 22, the liquid raw material LM that has passed through the porous filter 23f becomes one or more meandering streaks (flow paths R) and flows down between the spherical bodies 30. When the amount of heat of the infrared rays from the heater H is sufficient for the liquid raw material LM, the entire amount of the liquid raw material LM vaporizes in the straight pipe portion 22f on the inlet side. On the other hand, when the amount of heat of the infrared rays from the heater H is insufficient for the liquid raw material LM, the entire amount of the liquid raw material LM does not vaporize in the straight pipe portion 22f on the inlet side, and the unvaporized liquid raw material LM accumulates in the bent portion 22e.

[0046] Since the portion where the liquid raw material LM flows or accumulates has a lower temperature than other portions, if the temperature detector 70 is installed in this portion, the detected temperature will appear to be low. When the temperature detector 70 is installed so as to be non-contact with the vaporizer body 20 and the heater H, it will not be affected by both of them, absorb the infrared rays from the heater H and be heated, and detect the amount of infrared ray radiation from the heater H.

[0047] Here, to be precise, the widths M2 and M3 of the gaps d2 and d3 become a problem. As described above, the reflecting member 28 incorporates the vaporizer body 20 and the heater H inside. The internal temperature of the reflecting member 28 and the temperature of the side wall 22h of the vaporizer body 20 gradually increase as the temperature rises along the heater H. Even if the low-temperature outside air flows into the reflecting member 28 from the replacement gas supply portion 25 of the reflecting member 28 as described above, passes through the gaps d2 and d3, and exits from the replacement gas discharge portion 26 of the ceiling portion, 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 temperature boundary layer T, the heated replacement gas will touch the infrared absorber 78. As a result, the temperature measurement of the temperature detector 70 will be affected.

[0048] As shown in Fig. 7(a), when the gaps d2 and d3 (widths M2 and M3) are made larger than the thickness δ of the temperature boundary layer T, the unheated replacement gas flows along the infrared absorber 78 between the heated temperature boundary layer T and the infrared absorber 78, blocking the thermal influence of the heated temperature boundary layer T on the temperature detector 70. As a result, the influence of the heated temperature boundary layer T in the space where the infrared absorber 78 is arranged is surely removed. As a result, accurate temperature measurement of the heater H becomes possible.

[0049] Since the heater H is covered with the heater coil 88 by the transparent quartz tube 80 as described above, the temperature detector 70 cannot be installed on the heater coil 88. If the temperature detector 70 is to be installed on the transparent quartz tube 80, it will damage the transparent quartz tube 80, so the temperature detector 70 cannot be installed on the transparent quartz tube 80.

[0050] The temperature detector 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 is configured to control the supply power to the heater H according to the output from the temperature detector 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, forming a bell-shaped curve that extends to both the short-wavelength and long-wavelength sides. On the surface of the heater H facing the vaporizer body 20, a considerable portion of the infrared radiation travels toward the vaporizer body 20. The infrared radiation emitted on the rear side is reflected by the auxiliary reflector 89 on the back of the heater H (or by the cylindrical main reflector 28 if there is no auxiliary reflector 89) 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] As described above, 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. 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 lower surface. A spherical body 30 is in contact with the lower surface 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 flows down while wetting the surface of the spherical bodies 30, 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 range of 2.5 μm to 4 μm. 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 directly. 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, the auxiliary reflective member 89) on the opposite side of the reflecting 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 pipe 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 the liquid raw material LM is high, or if the supply rate of the liquid raw material LM fluctuates during the vaporization process and exceeds the heat supplied by the heater H, the entire amount of liquid raw material LM will not vaporize in the straight pipe section 22f at the inlet, 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 exposure to infrared radiation and vaporizes in the narrow gap 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 for efficient and rapid vaporization to continue.

[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 that is in contact with the liquid raw material LM will naturally be lower than that of the part that is 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. Furthermore, since the temperature detector 70 has a graphite infrared absorber 78 as a sheath-like outer shell, 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 the 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) In the above example, the liquid raw material LM is 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 is composed 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 is provided on the outer circumference of the liquid raw material supply pipe 12b, which is connected to the spray nozzle 12d and produces a Venturi effect. 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, 11) This embodiment 2 differs from embodiment 1 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, the heater H is erected at the front and rear of the vaporizer body 20. In contrast, in this modified example, the heater H is erected on both sides of the vaporizer body 20. As a result, the front-to-back width of the vaporizer 10 is reduced, and the reflector member 28 can be made into a thin rectangle in the front-to-back width in horizontal cross-section, thereby making the vaporizer 10 thinner. With 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 up beyond the ceiling plate 21. The temperature detector 70 is installed between the inlet or outlet straight pipe section 22f and 22g and one of the heater H. Everything else is the same as embodiment 1.

[0067] (Embodiment 3: Figure 12) In Embodiment 3, the vaporizer body 20 has a bent portion 22e located below the horizontally extending straight pipe portions 22f and 22g. If the flow rate is high, the liquid raw material LM that has flowed through the gap P of the spherical body 30 in the straight pipe portion 22f on the inlet side flows into the liquid reservoir E, which is the bent portion 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, and it may be connected to the straight pipe portions 22f and 22g, with the lower surface of the boundary portion bulging downward in a hemispherical shape, and this bulging portion may be the liquid reservoir E. Excess liquid raw material LM that has flowed 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, and 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 made longer than in Embodiment 1, so uniform heating of the raw material gas VG can be further promoted. Everything else is the same as in Embodiment 1.

[0069] (Embodiment 6: Figure 15) The vaporizer body 20 of Embodiment 6 is made 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 can further promote 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 can further promote uniform heating of the raw material gas VG. Everything else is the same as in Embodiment 1.

[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 path, S: Atomization space, T: Thermal boundary layer, VG: Raw material gas, δ: Thickness of thermal boundary layer 10: Vaporizer, 12: Liquid raw material supply section, 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 section, 22e: Bent section, 22f, 22g: Straight section, 22h: Side wall, 23f, 23g: Porous filter, 25: Replacement gas supply section, 26: Replacement gas discharge section, 27: Bottom plate 28: Reflective member, 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 member, 89k: Mirror surface, 90: Infrared heater temperature controller, 91: Power supply

Claims

1. A vaporizer comprising a vaporizer body 20 comprising 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 vaporizes the liquid raw material LM, wherein the heater H is positioned with a gap d1 of width M1 from the vaporization unit 22, the vaporization unit 22 and the spherical body 30 are made of transparent material that transmits infrared rays, and a liquid reservoir E into which the liquid raw material LM flows is provided in the vaporization unit 22 at a position lower than the flow path R of the liquid raw material LM flowing through the vaporization space K.

2. The vaporizer according to claim 1, characterized in that the vaporization section 22 is made of a bent pipe.

3. The vaporizer according to claim 1, characterized in that it includes a reflective member 28 which is arranged outside the heater H so as to surround the vaporization section 22, and whose inner surface facing the vaporization section 22 is formed as a mirror surface 28k that reflects infrared rays.

4. The vaporizer according to claim 1 or 3, characterized in that the auxiliary reflective member 89 is provided on the side of the heater H opposite to the vaporizer body 20, and the surface of the auxiliary reflective member 89 that reflects infrared rays toward the vaporizer body 20 is a mirror surface 89k.

5. The vaporizer according to claim 1 or 3, characterized in that a temperature detector 70 for measuring the amount of infrared radiation is positioned between the vaporization section 22 and the heater H, with gaps d2 and d3 of width M2 and M3 between the vaporizer body 20 and the heater H.

6. The vaporizer according to claim 5, characterized in that the temperature detector 70 comprises a graphite infrared absorber 78 that absorbs infrared rays and is heated, and a temperature detection element 71 embedded in the infrared absorber 78 for detecting the temperature of the infrared absorber 78.

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