Vaporizer and ion source

Abstract

To improve the service life of a vaporizer by suppressing the clogging of a nozzle.SOLUTION: A vaporizer 1 generates metal vapor from a reaction product of a metal-containing solid material 7 and a chlorine-containing gas, and includes a crucible 2 for storing the solid material 7, a heater 5 for heating the crucible 2, and a nozzle 3 fixed to an end of the crucible 2 and having a passage T for discharging the metal vapor to the outside of the crucible 2. The nozzle 3 is made of a carbon material, and has a first surface S forming a side wall of the crucible 2 by being fixed to the crucible 2, and the first surface S has a protrusion P protruding toward the inside of the crucible 2 and having a passage T formed therein.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a vaporizer and an ion source having the vaporizer. [Background technology]

[0002] Silicon carbide (SiC) devices are expected to be used in high-voltage, high-temperature applications such as electric vehicles, railways, and power plants. The manufacturing process for SiC devices is similar to that for conventional silicon devices in that it uses an ion implantation process.

[0003] In the ion implantation process for SiC devices, nitrogen ions or phosphorus ions are implanted as N-type dopants, and aluminum ions or boron ions are implanted as P-type dopants into the SiC wafer to create PN junctions.

[0004] In the generation of nitrogen ions, phosphorus ions, and boron ions, plasma is generally generated using gas as a raw material, but in the generation of aluminum ions, there is no optimal gas as a raw material.

[0005] To generate plasma containing aluminum ions, sputtering of aluminum-containing solid materials (aluminum nitride, alumina, etc.) has been used. Vaporizers have also been used. Specifically, the aluminum-containing solid material is placed in a crucible, and aluminum-containing vapor is generated from the solid material by heating the crucible. Plasma containing aluminum ions is then generated from the vapor.

[0006] In contrast to these prior art vaporizers, new vaporizers have been proposed, as disclosed in Patent Documents 1 and 2. In the vaporizers disclosed in these documents, a reactive gas (such as chlorine gas or hydrogen chloride gas) is supplied to a crucible. A solid material (such as pure aluminum, aluminum nitride, or alumina) is placed in the crucible. In the crucible, the reactive gas reacts with the solid material, generating a reaction product (aluminum chloride) on the solid material. The generated reaction product is vaporized by heating the crucible to a high temperature and supplied to a plasma generation chamber. In the plasma generation chamber, plasma containing aluminum ions is generated from the supplied vapor. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2023-154377 [Patent Document 2] Patent Publication No. 2023-172015 Summary of the Invention [Problem to be solved by the invention]

[0008] To improve the efficiency of aluminum ion generation, it is desirable to increase the crucible temperature. When the crucible temperature is increased, the amount of chlorine radicals generated due to the chlorine component in the reactive gas increases. The chlorine radicals easily bond with aluminum. As a result, the amount of AlCl generated increases.

[0009] In order to increase the volume of solid material during long-term operation of the vaporizer, a long cylindrical crucible is used. Such a crucible has a temperature distribution along the length of the crucible. The temperature distribution tends to be higher in the center of the crucible where the heater is located, and lower at the edges of the crucible than in the center.

[0010] AlCl produced in the center of the crucible, where the temperature is relatively high, is separated into Al and Cl due to the temperature difference when it reaches the end of the crucible, where the temperature is relatively low, due to the flow of reactive gas supplied into the crucible in the longitudinal direction of the crucible.

[0011] The crucible and the nozzle fixed to the end of the crucible are made of a carbon material from the viewpoints of heat resistance, workability, cost, etc. When AlCl is separated, Cl is released as a gas, while the separated Al remains active at the edge of the crucible and reacts with the crucible and nozzle, which are made of carbon materials, to produce Al4C3.

[0012] The aluminum is liquefied in the high-temperature crucible, and the addition of Al4C3 improves the wettability of the liquefied aluminum. If the wettability improves, there is a concern that the molten aluminum may creep up to the entrance of the nozzle that emits the vapor, causing clogging of the nozzle.

[0013] The main object of the present invention is to suppress clogging of the nozzle and improve the life of the vaporizer. [Means for solving the problem]

[0014] 1. A vaporizer for producing metal vapor from reaction products of a metal-containing solid material and a chlorine-containing gas, comprising: a crucible containing the solid material; a heater for heating the crucible; a nozzle fixed to an end of the crucible and having a passage for discharging the metal vapor to the outside of the crucible; the nozzle is made of a carbon material and has a first surface that forms a side wall of the crucible by being fixed to the crucible; The first surface has a protrusion that protrudes toward the inside of the crucible and in which the passage is formed.

[0015] Even if a liquefied metal material with good wettability adheres to the first surface that forms the side surface of the crucible, the protrusions can prevent the metal material from flowing into the nozzle, thereby extending the life of the crucible.

[0016] To secure the internal space of the crucible for placing the solid material and to enhance the effect of suppressing the inflow of the metal material into the nozzle, The protrusion preferably has a tapered portion.

[0017] To improve the effect of preventing metal materials from flowing into the nozzle, The protrusion preferably has a large diameter portion at a position spaced apart from the first surface.

[0018] The ion source is configured as follows: the vaporizer as described above; a plasma generation chamber for generating plasma from the vapor supplied from the vaporizer; and an extraction electrode for extracting an ion beam from the plasma. [Effects of the Invention]

[0019] Even if a liquefied metal material with good wettability adheres to the first surface that forms the side surface of the crucible, the protrusions can prevent the metal material from flowing into the nozzle, thereby extending the life of the crucible. [Brief explanation of the drawings]

[0020] [Figure 1] Schematic cross-sectional view of the ion source [Figure 2] Enlarged view of No. 1 nozzle [Figure 3] Schematic cross-sectional view showing a modified example of the first nozzle [Figure 4] FIG. 10 is a schematic cross-sectional view showing another modified example of the first nozzle; [Figure 5] FIG. 10 is a schematic cross-sectional view showing another modified example of the first nozzle; [Figure 6] FIG. 10 is a schematic cross-sectional view showing another modified example of the first nozzle; [Figure 7] FIG. 10 is a schematic cross-sectional view showing another modified example of the first nozzle; DETAILED DESCRIPTION OF THE INVENTION

[0021] FIG. 1 is a schematic cross-sectional view of an ion source IS. The ion source IS is an indirectly heated cathode (IHC) ion source. In this ion source IS, a filament 16 heats a cathode 15. The heated cathode 15 emits ionization electrons into a plasma generation chamber 14. A reflector 17 is disposed opposite the cathode 15. The reflector 17 repels ionization electrons that approach the reflector 17 toward the cathode 15. An electromagnet (not shown) is disposed outside the plasma generation chamber 14. This electromagnet generates a magnetic field inside the plasma generation chamber 14 along the direction in which the cathode 15 and the reflecting electrode 17 face each other.

[0022] Vapor containing aluminum is supplied from the vaporizer 1 to the plasma generation chamber 14. In the plasma generation chamber 14, plasma, depicted by the dashed line, is generated from the aluminum-containing vapor. An ion beam IB containing aluminum ions is extracted by an extraction electrode E from an ion extraction port 23 of the plasma generation chamber 14.

[0023] 1 shows two extraction electrodes E having a passage hole for the ion beam IB. However, the number of extraction electrodes E shown in FIG. 1 is merely an example. The number of electrodes constituting the extraction electrode E may be three or more, and may be changed depending on the configuration of the ion source.

[0024] The vaporizer 1 includes a crucible 2 that contains an aluminum-containing solid material 7 (for example, a solid material such as pure aluminum, aluminum nitride, or aluminum oxide, including powder).

[0025] The crucible 2 illustrated in Fig. 1 is a cylindrical member that is long in one direction. For example, the axis of the crucible 2 extends along the Z-axis direction in Fig. 1. One end of the crucible 2 in the longitudinal direction is provided with an outlet 2b for supplying aluminum-containing vapor to the plasma generation chamber 14. The other end of the crucible 2 in the longitudinal direction is provided with an inlet 2a for supplying a chlorine-containing gas, which is a reactive gas, to the crucible 2. The chlorine-containing gas is a gas that contains a chlorine component, such as chlorine gas (Cl2) or hydrogen chloride gas (HCl).

[0026] A first nozzle 3 is detachably attached to the crucible 2. In the configuration example of Fig. 1, a second nozzle 4 for supplying a reactive gas into the crucible 2 is integrally formed with the crucible 2. Various methods (for example, fitting and / or screwing) can be used to attach the first nozzle 3 to the crucible 2. The first nozzle 3, the second nozzle 4, and the crucible 2 are made of a carbon material from the viewpoints of heat resistance, workability, cost, and the like.

[0027] 1, arrow J indicates the flow of chlorine-containing gas supplied to crucible 2. The chlorine-containing gas flows from gas supply source 11 through valve 12, passes through second nozzle 4, crucible 2, and first nozzle 3 in this order, and then flows into plasma generation chamber 14. When the chlorine-containing gas flows into the crucible 2, it reacts with the aluminum-containing solid material 7 heated to a high temperature. This reaction generates reaction products such as aluminum chloride (AlCl). The generated reaction products are vaporized in the high-temperature crucible 2, generating aluminum-containing vapor containing aluminum particles. The aluminum-containing vapor and chlorine-containing gas are supplied from the crucible 2 to the plasma generation chamber 14 via the first nozzle 3.

[0028] In some embodiments, the aluminum-containing solid material 7 is pure aluminum having a purity of 99.90% or more. Pure aluminum increases the proportion of aluminum in the aluminum-containing vapor compared to other materials. The use of such pure aluminum increases the ion beam current of the ion beam IB containing aluminum ions extracted from the ion source IS. However, the aluminum-containing solid material 7 is not limited to pure aluminum, and in some embodiments, aluminum nitride, aluminum oxide, and / or other aluminum-containing solid materials may be used.

[0029] The chlorine-containing gas may be supplied to the second nozzle 4 via a connecting member 9 fitted inside the second nozzle 4. Alternatively, a mass flow controller may be connected to a pipe 13 connecting the gas supply source 11 and the connecting member 9 to control the flow rate of the chlorine-containing gas. However, the specific configuration for the gas supply is not particularly limited as long as it can supply the chlorine-containing gas to the connecting member 9.

[0030] An end 3a of the first nozzle 3 opposite to the end attached to the crucible 2 protrudes into the plasma generation chamber 14. The end 3a is provided with vapor supply holes in four orthogonal directions. This configuration makes it possible to diffuse and supply aluminum-containing vapor in multiple directions inside the plasma generation chamber 14. However, the number of vapor supply holes formed in the end 3a is not limited to four. It may be less than four or more than four.

[0031] A heater 5 is disposed around the periphery of the crucible 2. The heater 5 is, for example, a coil heater or a sheet heater. However, various other heaters may also be used. A first heat shield 6a is disposed around the periphery of the heater 5 to block heat radiation from the heater 5. Similarly, a second heat shield 6b is disposed between the plasma generation chamber 14 and the first nozzle 3 to prevent heat transfer from the plasma generation chamber 14 to the crucible 2.

[0032] The second nozzle 4 may have a larger diameter portion 4a. A flange 8 is provided for attaching the vaporizer 1 to an ion source flange 18. In FIG. 1, the ion source flange 18 supports components not shown, thereby indirectly supporting the plasma generation chamber 14 and other components such as the filament 16 and cathode 15 around the plasma generation chamber 14.

[0033] A coil spring 10 is provided between the flange 8 and the large diameter portion 4a of the second nozzle 4. The coil spring 10 urges the vaporizer 1 against the side wall of the plasma generation chamber 14 to keep the space between the first nozzle 3 and the plasma generation chamber 14 airtight and to prevent the inflow of aluminum-containing vapor and / or chlorine-containing gas from between the members. Furthermore, the elastic member that biases the vaporizer 1 against the side wall of the plasma generation chamber 14 is not limited to the coil spring 10, and other alternative means such as a leaf spring may be used.

[0034] To maintain an airtight seal between the first nozzle 3 and the plasma generation chamber 14, one or more gaskets (not shown) may be provided between the vaporizer 1 and the sidewall of the plasma generation chamber 14. Furthermore, in order to prevent excessive pressure due to the elastic force of the coil spring 10, a damper, for example, a spring clip in the shape of a snap ring, may be attached to the first nozzle 3. Similarly, in order to prevent excessive pressure due to the elastic force of the coil spring 10, a damper (for example, a spring clip) may be provided between the large diameter portion 4a of the second nozzle 4 and the inner wall of the first heat shield plate 6a.

[0035] The cross section of the aluminum-containing solid material 7 in the XY plane is semicircular. Since the chlorine-containing gas flows along the surface of the aluminum-containing solid material 7, the chlorine-containing gas and the solid material 7 can react with each other efficiently.

[0036] Ion species other than aluminum ions are also used to fabricate PN junctions in SiC devices. To generate other ion species, gases such as PH3, PF3, BF3, and N2 are supplied to the plasma generation chamber 14. The supply path for these gases may be shared with the flow path for the chlorine-containing gas. However, since mixing with residual gas may cause unexpected discharge or other inconveniences, a separate gas supply path may be provided. In FIG. 1, a gas inlet 22 for supplying other gas species is provided on the wall surface on the X-axis side of the plasma generation chamber 14.

[0037] In the embodiment shown in FIG. 1, an IHC ion source is exemplified as the configuration of the ion source IS, but other configurations such as a Bernas type or a high frequency type may also be employed.

[0038] Instead of projecting the end 3a of the first nozzle 3 into the plasma generation chamber , the tip of the end 3a provided on the first nozzle 3 may be flush with the wall of the plasma generation chamber . In this case, the number of holes for supplying steam formed in the end portion 3a of the first nozzle 3 is one in the Z direction.

[0039] A protrusion P is provided at the end of the first nozzle 3 on the side of the crucible 2. By providing this protrusion P, the aluminum with improved wettability is prevented from flowing into the passage T of the first nozzle 3.

[0040] In the crucible 2 heated to a high temperature, a large amount of chlorine radicals are generated from the chlorine-containing gas. The chlorine radicals easily combine with aluminum to generate AlCl. AlCl produced in the center of crucible 2, which is at a relatively high temperature, is separated into Al and Cl due to the temperature difference when it reaches the end of the crucible, which is at a relatively low temperature, due to the flow of reactive gas supplied to crucible 2 in the longitudinal direction of crucible 2.

[0041] When AlCl is separated, Cl is discharged as a gas, while the separated Al remains active at the end of the crucible 2 and reacts with the carbon crucible 2 and first nozzle 3 to produce Al4C3.

[0042] In the crucible 2 heated to a high temperature, the aluminum is liquefied. The addition of Al4C3 improves the wettability of the liquefied aluminum. The aluminum with improved wettability travels through the crucible and reaches the vicinity of the first nozzle 3.

[0043] FIG. 2 is an enlarged view of the first nozzle 3 shown in FIG. The aluminum with improved wettability adheres to the first surface S of the first nozzle 3 shown in FIG. 2. The first surface S forms the side wall of the crucible 2 on the plasma generation chamber 14 side. Over time, the amount of aluminum adhering to the first surface S increases, and at a certain point, it flows into the passage T of the first nozzle 3. As a result, the first nozzle 3 becomes clogged. However, as shown in Figures 1 and 2, by providing a protrusion P on the first surface S of the first nozzle 3 forming the side wall of the crucible 2, it is possible to suppress the inflow of aluminum into the passage T. This improves the life of the vaporizer 1.

[0044] There is a concern that the aluminum that has flowed into the passage T may be carried by the reactive gas flow into the plasma generation chamber 14. Components with different potentials are arranged in the plasma generation chamber 14. If aluminum flows into the plasma generation chamber 14, there is a concern that a short circuit may occur between the components. However, by providing a protrusion P on the first surface S of the first nozzle 3 that forms the side wall of the crucible 2, it is possible to suppress the flow of aluminum into the passage T, thereby alleviating such concerns.

[0045] Figure 3 shows a modified example of the first nozzle 3. The protrusion P in Figures 1 and 2 has a conical shape with the top cut off, but it may also have a cylindrical shape like the protrusion P in Figure 3. Even when the protrusion P shown in Figure 3 is employed, the life of the carburetor 1 can be improved, just like the protrusion P in Figures 1 and 2. However, in order to increase the effect of expanding the internal space of the crucible 2 and suppressing the inflow of aluminum into the passage T, the configuration shown in FIGS. 1 and 2 in which the protruding portion P has the tapered portion V is preferable.

[0046] 4 may be employed for the configuration of the protrusion P having the tapered portion V. In the configuration example of FIG. If the protruding portion P protrudes toward the center inside the crucible 2, the temperature of the end surface Sa of the protruding portion P will be sufficiently higher than the temperature of the first surface S. If the end surface Sa of the protruding portion P can be kept at a high temperature, the generation of Al4C3 on the end surface Sa is suppressed, and the wettability of aluminum on the end surface Sa is low. Therefore, as long as there is no excessive flow of aluminum from the first surface S to the end surface Sa, even if liquefied aluminum adheres to the end surface Sa of the protruding portion P, it can be kept at the end surface Sa.

[0047] As in the configuration example of Fig. 4, a protrusion P consisting of a double cylinder structure (C1, C2) with different diameters as shown in Fig. 5 may be employed. If the temperature of the large-diameter cylinder C1 is sufficiently higher than that of the first surface S, even if liquefied aluminum adheres to the end surface of the cylinder C1, it can be kept on the cylinder C1, just like the end surface Sa described in Fig. 4. As shown in Figures 4 and 5, by providing a large-diameter portion at a position away from the first surface S, this portion acts as a return hole, effectively suppressing the inflow of aluminum, which has good wettability, from the first surface S.

[0048] The configuration shown in Fig. 6 may be employed to provide a large diameter portion at a position spaced apart from the first surface S. In Fig. 6, the protrusion P is provided with two large diameter portions with different diameters.

[0049] The first nozzle 3 shown in FIGS. 1 to 6 is made up of one member, but may be made up of a plurality of members as shown in FIG. In FIG. 7, the first nozzle 3 is composed of a first member 3-1 and a second member 3-2. The respective parts are assembled by fitting, screwing, or other methods. The first member 3-1 may have the same configuration as the embodiments described so far. In other words, the first member 3-1 forming part of the first nozzle 3 may have a first surface S forming the side wall of the crucible 2, and the first surface S may have a protruding portion P that protrudes toward the inside of the crucible 2 and has a passage T formed therein for releasing vapor.

[0050] In the above embodiment, the solid-state material 7 is described as containing aluminum, but the solid-state material 7 of the present invention is not limited to this. For example, the solid-state material 7 may contain other metals such as titanium, nickel, molybdenum, and tungsten. These metal-containing solid materials may be reacted with a chlorine-containing gas to produce reaction products from which metal vapors may be produced.

[0051] Even if the type of solid material 7 is changed, there is a concern about nozzle clogging, just as when an aluminum-containing solid material 7 is used.However, by using the first nozzle 3 equipped with the protrusion P of the present invention, such concerns can be alleviated and the life of the vaporizer 1 can be extended.

[0052] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Explanation of symbols]

[0053] 1. Vaporizer 2 Crucible 5 Heater 7 Solid materials 3 No. 1 nozzle P protrusion S First Side T aisle V-tapered section IS ion source

Claims

1. 1. A vaporizer for producing metal vapor from reaction products of a metal-containing solid material and a chlorine-containing gas, comprising: a crucible containing the solid material; a heater for heating the crucible; a nozzle fixed to an end of the crucible and having a passage for discharging the metal vapor to the outside of the crucible; the nozzle is made of a carbon material and has a first surface that forms a side wall of the crucible by being fixed to the crucible; The first surface of the vaporizer has a protrusion that protrudes toward the inside of the crucible and has the passage formed therein.

2. The carburetor of claim 1 , wherein the protrusion has a tapered portion.

3. The carburetor according to claim 1 , wherein the protrusion has a large diameter portion spaced apart from the first surface.

4. A vaporizer according to any one of claims 1 to 3; a plasma generation chamber for generating plasma from the vapor supplied from the vaporizer; an extraction electrode for extracting an ion beam from the plasma;

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