Ion sources with different operating modes

Abstract

An ion source capable of different operation modes is disclosed. A vaporizer communicates with the ion source. The ion source can have a plurality of gas inlets communicating with different gases. When operating in the first mode, the ion source can supply a first gas, such as an inert gas, while heating the vaporizer. When operating in the second mode, the ion source can supply a second gas, and the second gas can be an organoaluminum gas. When operating in the third mode, the ion source can supply the second gas while heating the vaporizer. Ions having a single charge can be generated in the first and second modes, while ions having multiple charges can be generated in the third mode.

Description

Technical Field

[0001] This application claims priority to U.S. Patent Application No. 17 / 834,445, filed Jun. 7, 2022, the entire disclosure of which is hereby incorporated by reference in its entirety.

[0002] Embodiments of the present disclosure relate to ion sources, and more particularly, to ion sources having multiple modes for generating ions of species having different charges.

Background Art

[0003] To generate ions for use in semiconductor processing equipment, various types of ion sources can be used. For example, an indirectly heated cathode (IHC) ion source operates by supplying current to a filament disposed behind the cathode. The filament emits thermoelectrons, which are accelerated towards the cathode, heating the cathode, whereby the cathode emits electrons into the arc chamber of the ion source. The cathode is disposed at one end of the arc chamber. A repeller can be disposed at the end of the arc chamber opposite the cathode. The cathode and the repeller can be biased to repel electrons and return them towards the center of the arc chamber. In some embodiments, a magnetic field is used to further confine the electrons within the arc chamber. Multiple sides are used to connect the two ends of the arc chamber.

[0004] An extraction aperture is disposed along one of these sides proximate to the center of the arc chamber, and ions generated within the arc chamber can be extracted through the extraction aperture.

[0005] In certain embodiments, it may be desirable to generate ions with a single charge. However, in other embodiments, it may be desirable to generate polyvalent ions. Unfortunately, in certain materials such as aluminum and other metals, the mechanism used to generate monovalent ions may not be effective when generating polyvalent ions. Therefore, different ion sources may be used depending on the desired charge of the extracted ions.

[0006] This solution is costly because it utilizes multiple ion sources. Furthermore, it is time-consuming because it takes time to switch from one ion source to another.

[0007] Therefore, a single ion source that can operate in different modes to generate ions with different charges would be beneficial. Furthermore, the ability to quickly switch the arc chamber from one mode to another would be advantageous. [Overview of the Initiative]

[0008] An ion source capable of different operating modes is disclosed. A vaporizer communicates with the ion source. The ion source may have multiple gas inlets communicating with different gases. When operating in the first mode, the ion source can supply a first gas, such as an inert gas, while heating the vaporizer. When operating in the second mode, the ion source can supply a second gas, which may be an organoaluminum gas. When operating in the third mode, the ion source can supply a second gas while heating the vaporizer. Ions with a single charge can be produced in the first and second modes, but ions with multiple charges can be produced in larger quantities in the third mode.

[0009] According to one embodiment, an indirectly heated cathode ion source is disclosed. The indirectly heated cathode ion source comprises an arc chamber having a plurality of walls, an indirectly heated cathode disposed within the arc chamber, a vaporizer communicating with the arc chamber, a heater for heating a dopant material disposed within the vaporizer, a first valve communicating with the arc chamber and a first gas source, a second valve communicating with the arc chamber and a second gas source, and a controller communicating the first valve, the second valve, and the heater to operate the indirectly heated cathode ion source in one of a plurality of modes. In some embodiments, the plurality of modes include two single-charge modes that produce ions of a species having a single charge, and a multi-charge mode that produces ions of a species having two or more charges. In some embodiments, the species include metals. In some embodiments, in the first single-charge mode, the controller activates the heater, opens the first valve, and closes the second valve. In some embodiments, in a second single-charge mode, the controller deactivates the heater and opens a second valve. In certain embodiments, in a second single-charge mode, the controller opens a first valve. In some embodiments, in a multi-charge mode, the controller activates the heater and opens a second valve. In some embodiments, the dopant material placed in the vaporizer comprises a solid compound containing a metal, and the metal is also a component of the second gas contained in the second gas source. In certain embodiments, the metal is aluminum, and the dopant material placed in the vaporizer is aluminum chloride. In certain embodiments, the metal is aluminum, and the dopant material placed in the vaporizer is aluminum iodide. In some embodiments, the metal is aluminum, the first gas source contains an inert gas, and the second gas source contains dimethylaluminum chloride or trimethylaluminum chloride.

[0010] According to another embodiment, a method is disclosed for operating an indirectly heated cathode ion source in multiple modes, wherein the indirectly heated cathode ion source comprises a controller, an arc chamber, a vaporizer communicating with the arc chamber, and a heater for heating a dopant material in the vaporizer. The method includes selecting a desired operating mode and configuring the indirectly heated cathode ion source to operate in the desired mode using the controller, wherein to operate in a multi-charge mode, the multi-charge mode is used to generate ions of species having two or more charges, the heater is activated to allow vaporized dopant material containing a metal to enter the arc chamber, the controller allows the flow of a metal-containing gas into the arc chamber, in a first single-charge mode, the first single-charge mode is used to generate ions of species having a single charge, the controller activates the heater and allows the flow of an inert gas into the arc chamber, and to operate in a second single-charge mode, the second single-charge mode is used to generate ions of species having a single charge, the controller deactivates the heater and generates a plasma using the metal-containing gas. In some embodiments, the metal is aluminum, and the dopant material placed in the vaporizer is aluminum chloride.

[0011] In some embodiments, the metal is aluminum, and the dopant material placed in the vaporizer is aluminum iodide. In some embodiments, the metal is aluminum, and the metal-containing gas includes DMAC or TMAC.

[0012] According to another embodiment, an indirectly heated cathode ion source is disclosed. The indirectly heated cathode ion source comprises an arc chamber having a plurality of walls, a vaporizer communicating with the arc chamber, an indirectly heated cathode disposed within the arc chamber, the indirectly heated cathode being used to generate plasma within the arc chamber, and a controller configured to operate the indirectly heated cathode ion source in one of a plurality of modes, in multi-charge mode, the controller configures the indirectly heated cathode ion source so that two sources of metal are used to generate plasma. In some embodiments, the metal is aluminum, the material disposed within the vaporizer contains aluminum chloride, and an aluminum-containing gas is introduced into the arc chamber when operating in multi-charge mode. In some embodiments, the metal is aluminum, the material disposed within the vaporizer contains aluminum iodide, and an aluminum-containing gas is introduced into the arc chamber when operating in multi-charge mode. In certain embodiments, in single-charge mode, only one of the two sources is introduced into the arc chamber.

[0013] For a better understanding of this disclosure, refer to the accompanying drawings incorporated herein by reference. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram of an indirectly heated cathode (IHC) ion source having multiple operating modes according to one embodiment. [Figure 2] This figure shows the operation of the controller using the embodiment shown in Figure 1. [Modes for carrying out the invention]

[0015] As mentioned above, certain dopants, such as aluminum and other metals, utilize different mechanisms to generate monovalent and polyvalent ions.

[0016] Figure 1 shows an IHC ion source 10 that solves these problems. The IHC ion source 10 includes an arc chamber 100 having two opposing ends and a wall 101 connecting these ends. The wall 101 of the arc chamber 100 can be made of a conductive material and can be electrically connected to each other. In some embodiments, a liner may be positioned adjacent to one or more of the walls 101. A cathode 110 is positioned within the arc chamber 100 at a first end 104 of the arc chamber 100. A filament 160 is positioned behind the cathode 110. The filament 160 communicates with a filament power supply 165. The filament power supply 165 is configured to pass an electric current through the filament 160 so that the filament 160 emits thermionic electrons. The cathode bias power supply 115 applies a negative bias to the filament 160 relative to the cathode 110, so that these thermionic electrons are accelerated from the filament 160 toward the cathode 110, heating the cathode 110 when the thermionic electrons strike the rear surface of the cathode 110. The cathode bias power supply 115 can bias the filament 160 so that it has a voltage that is, for example, 200V to 1500V negative than the voltage of the cathode 110. The cathode 110 then emits thermionic electrons on the front surface of the cathode into the arc chamber 100.

[0017] Therefore, the filament power supply 165 supplies current to the filament 160. The cathode bias power supply 115 biases the filament 160 so that it is more negative than the cathode 110, and thus electrons are attracted from the filament 160 toward the cathode 110. In certain embodiments, the cathode 110 can be biased toward the arc chamber 100 by a bias power supply 111, for example. In other embodiments, the cathode 110 may be electrically connected to the arc chamber 100 so that it has the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the bias power supply 111 may not be used, and the cathode 110 may be electrically connected to the wall 101 of the arc chamber 100. In certain embodiments, the arc chamber 100 is connected to electrical ground.

[0018] A repeller 120 may be positioned on a second end 105 opposite the first end 104. The repeller 120 can be biased to the arc chamber 100 using a repeller bias power supply 123. In other embodiments, the repeller 120 may be electrically connected to the arc chamber 100 so that it is at the same voltage as the walls 101 of the arc chamber 100. In these embodiments, the repeller bias power supply 123 may not be used, and the repeller 120 may be electrically connected to the walls 101 of the arc chamber 100. In yet another embodiment, the repeller 120 is not used.

[0019] The cathode 110 and repeller 120 are made of conductive materials such as metal or graphite, respectively.

[0020] In certain embodiments, a magnetic field is generated within the arc chamber 100. This magnetic field is intended to confine electrons along one direction. Typically, the magnetic field runs parallel to the wall 101 from the first end 104 to the second end 105. For example, electrons can be confined in a cylinder parallel to the direction from the cathode 110 to the repeller 120 (i.e., the y-direction). Thus, electrons are not subject to any electromagnetic forces moving in the y-direction. However, movement of electrons in other directions may be subject to electromagnetic forces.

[0021] An extraction opening 140 may be located on one side of the arc chamber 100, called the extraction plate 103. In Figure 1, the extraction opening 140 is located on a side parallel to the YZ plane (perpendicular to the page).

[0022] Furthermore, the IHC ion source 10 can communicate with at least two gas sources. The first gas source 170 may contain a first gas, which may be an inert gas such as argon. A first valve 171 may be used to control the flow of the first gas from the first gas source 170 to the IHC ion source 10. The second gas source 175 may contain a second gas, which is an organoaluminum compound, a compound in which an aluminum atom is bonded to a carbon atom. In certain embodiments, the organoaluminum compound contains halogens and aluminum. In certain embodiments, the second gas may be dimethylaluminum chloride (DMAC, (CH3)2AlCl) or trimethylaluminum chloride (TMAC, (CH3)3AlCl). Other gases containing metal atoms bonded to carbon atoms may also be used. In some embodiments, this second gas contains carbon, metals and halogens. The second gas source 175 may also contain various diluent gases, such as hydrogen, argon, or other gases. In other words, the second gas source 175 contains the second gas, but may also contain other gases. The second valve 176 can be used to control the flow of the second gas from the second gas source 175 to the ion source 10. The first valve 171 and the second valve 176 can be made into a mass flow controller (MFC) so that the flow rate can be controlled.

[0023] The vaporizer 190 can communicate with the arc chamber 100. For example, the vaporizer can be disposed outside the arc chamber 100, but can include a conduit 191 that connects the output of the vaporizer to the arc chamber 100. The heater 195 can be disposed proximate to the vaporizer 190 to heat and vaporize the dopant material 197 disposed within the vaporizer 190. The heater 195 can be a resistive heater or another type. The design of the heater is implementation-specific and not limited by the present disclosure. In certain embodiments, the dopant material 197 within the vaporizer 190 can be a solid compound containing a metal. For example, the dopant material 197 can be aluminum chloride or aluminum iodide. In other embodiments, the dopant material 197 within the vaporizer 190 can be gallium iodide, indium iodide, aluminum iodide, lanthanum fluoride, or another solid compound containing a metal and a halogen. The metal contained in the dopant material 197 is the same metal as that contained in the second gas.

[0024] The controller 180 can communicate with one or more of the power supplies such that the voltage or current supplied by these power supplies can be changed. The controller 180 can also communicate with the first valve 171, the second valve 176, and the heater 195. The controller 180 can include a processing device, such as a microcontroller, a personal computer, a dedicated controller, or another suitable processing device. The controller 180 can also include a non-transitory storage element, such as a semiconductor memory, a magnetic memory, or another suitable memory. This non-transitory storage element can include instructions and other data that enable the controller 180 to perform the functions described herein.

[0025] In the embodiment shown in FIG. 1, the controller 180 is configured to enable the ion source 10 to operate in a plurality of different modes. These modes include a first single-charge operation mode, a second single-charge operation mode, and a multi-charge operation mode. Each of these modes will be described in more detail.

[0026] In the first single charge operation mode, the filament power supply 165 passes current through the filament 160, which causes the filament 160 to emit thermoelectrons. These electrons strike the back of the cathode 110, which can be positive relative to the filament 160, heating the cathode 110, whereby the cathode 110 emits electrons into the arc chamber 100. These electrons collide with the molecules of the gas supplied into the arc chamber 100 through the gas inlet.

[0027] The controller 180 opens the first valve 171 to allow the flow of the first gas into the arc chamber 100. The first gas can be an inert gas. The controller 180 also controls the heater 195 so as to heat the dopant material 197 in the vaporizer 190 to a temperature at which the dopant material 197 is vaporized and the vaporized dopant material enters the arc chamber 100 through the conduit 191. By combining the electrons from the cathode 110, the first gas, and the vaporized dopant material, a plasma is generated. The ions in this plasma are mostly monovalent ions such as Al + etc. In certain embodiments, the electrons and positive ions can be somewhat confined by a magnetic field. In certain embodiments, the plasma is confined near the center of the arc chamber 100, close to the extraction aperture 140. Thus, in this first single charge mode, the metal is introduced only by the vaporized dopant material.

[0028] Thus, when it is desired to generate monovalent ions such as Al + etc., the operator can send this preference to the controller 180. Alternatively, the controller 180 can determine the desired mode based on the desired charge state and beam current. Accordingly, the controller 180 can execute the sequence described above.

[0029] In the second single-charge mode, the controller opens the second valve 176 to allow the flow of a second gas, which is a gas containing the same metal as the dopant material 197, into the arc chamber 100. The controller 180 also deactivates the heater 195 to prevent vapor from the vaporizer 190 from entering the arc chamber 100. The second gas is ionized to produce metal ions, usually with a single charge. Furthermore, if the second gas contains halogens, the halogens in the second gas act to reclaim metal from the walls of the arc chamber 100. Thus, in this second single-charge mode, metal is introduced only by the second gas. In certain embodiments, the first valve 171 can be opened to allow the flow of the first gas into the arc chamber 100. In other embodiments, the first valve 171 is closed.

[0030] In multi-charge mode, the controller 180 opens the second valve 176 to allow the flow of the second gas into the arc chamber 100. As described above, the second gas can be a gas containing the same metal as the dopant material 197. For example, if the metal is aluminum, the second gas can be DMAC or TMAC. These gases are useful in that the gas effectively reuses the metal from the walls of the arc chamber 100. The controller also operates the heater 195 so that the vaporized dopant material from the vaporizer 190 also enters the arc chamber 100 via the conduit 191. As described above, the metal in the vaporized dopant material is the same metal that is a component of the second gas. Since both the second gas and the vaporized dopant material contain the same metal, a plasma rich in this metal is generated. Due to the density of metal in the plasma, many of the ions generated in the plasma are Al ++ Ya Al +++ These can be polyvalent ions. The ions are then extracted through the extraction opening 140 and can be used as an ion beam.

[0031] In certain embodiments, the controller 180 may also open the first valve 171 to allow some of the first gas to flow into the arc chamber 100. Thus, in enhanced mode, the second valve 176 is open and the first valve 171 can be opened or closed.

[0032] Therefore, when it is desired to generate polyvalent ions, the operator can transmit this preference to the controller 180. Alternatively, the controller 180 can determine the desired mode based on the desired charge state and beam current. Accordingly, the controller 180 can perform the sequence described above.

[0033] Accordingly, with respect to the embodiment shown in Figure 1, this application describes three different operating modes that can be used to generate different charge states of a desired dopant. Furthermore, by incorporating a vaporizer 190 communicating with a first gas, a second gas, and an arc chamber 100, the ion source 10 can be easily switched from one mode to another without operator intervention. Figure 2 shows the operation of a controller 180 that controls the mode of the ion source 10 when the vaporizer 190 communicates with the arc chamber 100. A desired operating mode is selected as shown in box 200, and this selection may depend on the policy being used. This mode may be selected by the operator or the user. Alternatively, the controller 180 may automatically select the optimal mode based on the desired beam current or charge state. Based on this selection, the controller 180 operates the first valve 171, the second valve 176, and the heater 195 to achieve the desired operating mode. Normally, the charge of the dopant material in the vaporizer 190 is limited, so the second gas source contains most of the Al in order to conserve the dopant material in the vaporizer 190 and effectively extend the source life. + It will be used for operation.

[0034] As shown in box 210, a multi-charge mode can be selected, optimizing the plasma conditions for the generation of multivalent metal ions. Accordingly, the controller 180 opens a second valve 176 to allow the flow of a second gas, which is a gas containing the same metal as the dopant material 197, into the arc chamber 100. The controller 180 can optionally open or close the first valve 171. The controller 180 also operates a heater 195 so that vaporized dopant material from the vaporizer 190 also enters the arc chamber 100 through the conduit 191. This vaporized dopant material contains the same metal as the second gas. With two sources of metal present, the plasma is rich in metal ions. This metal-rich plasma is effective in generating multivalent ions and can achieve multivalent ion currents that would be possible using either metal source separately.

[0035] Alternatively, as shown in box 220, a first single-charge mode can be selected, in which the majority of metal ions have a single charge. Accordingly, the controller 180 opens the first valve 171 to allow the flow of the first gas, which may be an inert gas such as argon, into the arc chamber 100. In this mode, the controller 180 operates the heater 195 so that the vaporized dopant material enters the arc chamber 100 through the conduit 191. The inert gas is ionized by the vaporized dopant material in the plasma, and the majority of the ions produced are monovalent ions.

[0036] As shown in box 230, a second single-charge mode can be selected, in which the majority of metal ions have a single charge. In the second single-charge mode, the controller 180 deactivates the heater 195 to prevent vaporized dopant material from entering the arc chamber 100. Furthermore, in this mode, the controller controls the second valve 176 to allow the flow of the second gas into the arc chamber 100. The second gas is ionized to produce metal ions, mostly having a single charge. In some embodiments, the first valve 171 is also opened to allow the flow of the first gas into the arc chamber 100. In other embodiments, the first valve is closed. Furthermore, halogens in the second gas serve to reclaim metal from the walls of the arc chamber 100. Thus, in this second single-charge mode, metal is introduced only by the second gas.

[0037] Therefore, to operate in multi-charge mode, the controller 180 configures the ion source 10 so that the metal is introduced by a second gas and a vaporized dopant material. To operate in single-charge mode, the controller 180 configures the ion source 10 so that the metal is introduced by only one of the second gas or a vaporized dopant material.

[0038] The above disclosure describes the use of an aluminum-containing dopant material and an aluminum-containing second gas as the solid compound in the vaporizer 190, but other metals may also be used. For example, the metal may be gallium. In this embodiment, the solid compound in the vaporizer 190 may be gallium iodide and the second gas may be organic gallium gas. In another embodiment, the metal may be indium. In this embodiment, the solid compound in the vaporizer 190 may be indium iodide and the second gas may be organic indium gas. In another embodiment, the metal may be lanthanum. In this embodiment, the solid compound in the vaporizer 190 may be lanthanum fluoride and the second gas may be organic lanthanide gas. Other metals may also be used.

[0039] The embodiments described in this application can have many advantages. First, the generation of an ion source that can operate in multiple modes is advantageous because the same ion source can be used to generate monovalent and polyvalent ions. Furthermore, there are additional benefits to combining the vaporizer with solid metal compounds and metal-containing gases.

[0040] Firstly, organoaluminum gas is available in gas containers, allowing for long service life and easy replacement. Organoaluminum also effectively generates monovalent aluminum ions. Finally, the halogens in the organoaluminum gas act as etchants, preventing aluminum from accumulating on the walls of the arc chamber 100.

[0041] Secondly, the use of vaporizer 190 is well known, and the amount of steam introduced into the arc chamber 100 can be precisely controlled based on the temperature of vaporizer 190.

[0042] Therefore, this ion source can produce monovalent or polyvalent ions of selected species, such as metals like aluminum, gallium, indium, and lanthanum.

[0043] This disclosure should not be limited in scope by the specific embodiments described herein. In fact, various other embodiments and modifications of this disclosure will be apparent to those skilled in the art from the foregoing description and accompanying drawings, in addition to those described herein. Accordingly, such other embodiments and modifications are within the scope of this disclosure. Furthermore, although this disclosure has been described herein in the context of a specific implementation in a specific environment for a specific purpose, those skilled in the art will understand that the usefulness of this disclosure is not limited to a specific implementation, and that this disclosure can be advantageously implemented in any number of environments for any number of purposes. Accordingly, the claims described below should be interpreted in light of the entirety and spirit of this disclosure as described herein.

Claims

1. An indirectly heated cathode ion source, An arc chamber with multiple walls, An indirect heating cathode arranged within the arc chamber, A vaporizer in communication with the aforementioned arc chamber, A heater for heating the dopant material placed inside the vaporizer, The arc chamber and the first gas source are connected by a first valve, The arc chamber and a second valve communicating with the second gas source, A controller communicating with the first valve, the second valve, and the heater is used to operate the indirect heating cathode ion source in one of several modes. Equipped with, An indirectly heated cathode ion source wherein the plurality of modes include at least one single-charge mode that generates a certain type of ion having a single charge, and a multi-charge mode that generates the certain type of ion having two or more charges.

2. The indirect heating cathode ion source according to claim 1, wherein the aforementioned species includes a metal.

3. The indirect heating cathode ion source according to claim 1, wherein there are two single-charge modes, and in the first single-charge mode, the controller operates the heater, opens the first valve, and closes the second valve.

4. The indirect heating cathode ion source according to claim 1, wherein there are two single charge modes, and in the second single charge mode, the controller prevents the heater from operating and opens the second valve.

5. The indirectly heated cathode ion source according to claim 4, wherein in the second single-charge mode, the controller opens the first valve.

6. In the multi-charge mode, the controller operates the heater and opens the second valve, as described in claim 1, an indirectly heated cathode ion source.

7. The indirectly heated cathode ion source according to claim 1, wherein the dopant material disposed in the vaporizer comprises a solid compound containing a metal, and the metal is also a component of the second gas contained in the second gas source.

8. The indirect heating cathode ion source according to claim 7, wherein the metal is aluminum and the dopant material disposed in the vaporizer is aluminum chloride.

9. The indirect heating cathode ion source according to claim 7, wherein the metal is aluminum and the dopant material disposed in the vaporizer is aluminum iodide.

10. The indirectly heated cathode ion source according to claim 7, wherein the metal is aluminum, the first gas source contains an inert gas, and the second gas source contains dimethylaluminum chloride or trimethylaluminum chloride.

11. A method for operating an indirectly heated cathode ion source in multiple modes, wherein the indirectly heated cathode ion source comprises a controller, an arc chamber, a vaporizer communicating with the arc chamber, and a heater for heating a dopant material in the vaporizer, and the method is Select the desired operating mode, Using the controller, set the indirect heating cathode ion source to operate in the desired mode. Includes, In operation in multi-charge mode, the multi-charge mode is used to generate certain ions having two or more charges, the heater is operated so that vaporized dopant material containing a metal enters the arc chamber, and the controller enables the flow of the metal-containing gas into the arc chamber. In operating in a first single-charge mode, the first single-charge mode is used to generate certain ions having a single charge, and the controller operates the heater to allow the flow of inert gas into the arc chamber. A method for operating in a second single-charge mode, wherein the second single-charge mode is used to generate certain ions having a single charge, the controller is kept from operating the heater, and the gas containing the metal is used to generate a plasma.

12. The method according to claim 11, wherein the metal is aluminum and the dopant material disposed in the vaporizer is aluminum chloride.

13. The method according to claim 11, wherein the metal is aluminum and the dopant material disposed in the vaporizer is aluminum iodide.

14. The method according to claim 11, wherein the metal is aluminum, and the gas containing the metal includes DMAC or TMAC.

15. An indirectly heated cathode ion source, An arc chamber with multiple walls, A vaporizer in communication with the aforementioned arc chamber, An indirect heating cathode disposed within the arc chamber, wherein the indirect heating cathode is used to generate plasma within the arc chamber, A controller configured to operate the indirectly heated cathode ion source in one of several modes, wherein in a multi-charge mode, the controller is configured to use two sources of the same metal for plasma generation, and in a single-charge mode, the controller is configured to use one of the two sources for plasma generation. An indirectly heated cathode ion source equipped with [a specific feature].

16. The indirectly heated cathode ion source according to claim 15, wherein the metal is aluminum, the material placed in the vaporizer contains aluminum chloride, and the aluminum-containing gas is introduced into the arc chamber when operating in the multi-charge mode.

17. The indirect heating cathode ion source according to claim 15, wherein the metal is aluminum, the material placed in the vaporizer contains aluminum iodide, and the aluminum-containing gas is introduced into the arc chamber when operating in the multi-charge mode.

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