Ion source with different operating modes

Abstract

An ion source capable of operating in different modes. The gasifier is in communication with the ion source. The ion source may have a plurality of gas inlets in communication with different gases. When operating in a first mode, the ion source may supply a first gas (e.g., an inert gas) while heating the gasifier. When operating in a second mode, the ion source may supply a second gas, which may be an organoaluminum gas. When operating in a third mode, the ion source may supply a second gas while heating the gasifier. Ions having a single charge may be formed in the first mode and the second mode, while ions having a multi-charge may be formed in the third mode.

Description

[0001] This application claims priority to U.S. patent application serial number 17 / 834,445 filed on June 7, 2022, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

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

[0003] Various types of ion sources can be used to form ions used in semiconductor processing equipment. For example, an indirectly heated cathode (IHC) ion source operates by supplying an electric current to a filament disposed behind the cathode. The filament emits hot ion electrons, which accelerate toward the cathode and heat the cathode, which in turn causes the cathode to emit electrons into an arc chamber of the ion source. The cathode is disposed at one end of the arc chamber. A repeller may be disposed at an end of the arc chamber opposite the cathode. The cathode and repeller may be biased to repel electrons, thereby directing the electrons back toward 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 provided along one of the sides, near the center of the arc chamber, through which ions formed in the arc chamber can be extracted.

[0005] In some embodiments, it may be desirable to form ions with a single charge. However, in other embodiments, it may be desirable to form multiply charged ions. Unfortunately, for some materials (e.g., aluminum and other metals), the mechanisms used to form singly charged ions may not be effective in forming multiply charged ions. Therefore, different ion sources may be utilized depending on the desired charge of the extracted ions.

[0006] This solution is expensive because it utilizes multiple ion sources. It is also time consuming because of the time required to switch from one ion source to a different one.

[0007] Therefore, a single ion source that can be operated in different modes to produce ions with different charges would be beneficial. Additionally, it would be advantageous to enable the arc chamber to be quickly changed from one mode to another. Summary of the invention

[0008] An ion source capable of operating in different modes is disclosed. A vaporizer is connected to the ion source. The ion source may have a plurality of gas inlets connected to different gases. When operating in a first mode, the ion source may supply a first gas (e.g., an inert gas) while heating the vaporizer. When operating in a second mode, the ion source may supply a second gas (which may be an organic aluminum gas). When operating in a third mode, the ion source may supply a second gas while heating the vaporizer. In the first mode and the second mode, ions with a single charge may be formed, while in the third mode, more ions with a multiply charge may be formed.

[0009] According to one embodiment, an indirectly heated cathode ion source is disclosed. The indirectly heated cathode ion source includes: an arc chamber including a plurality of walls; an indirectly heated cathode disposed in the arc chamber; a vaporizer in communication with the arc chamber; a heater for heating a dopant material disposed in the vaporizer; a first valve in communication with the arc chamber and a first gas source; a second valve in communication with the arc chamber and a second gas source; and a controller in communication with 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 and include a multi-charge mode, the two single charge modes being used to form ions of a species having a single charge, and the multi-charge mode being used to form ions of a species having two or more charges. In some embodiments, the species include a metal. In some embodiments, in the first single charge mode, the controller actuates the heater, opens the first valve, and closes the second valve. In some embodiments, in the second single charge mode, the controller deenergizes the heater and opens the second valve. In some embodiments, in the second single charge mode, the controller opens the first valve. In some embodiments, in the multi-charge mode, the controller actuates the heater and opens the second valve. In some embodiments, 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. In certain embodiments, the metal is aluminum and the dopant material disposed in the vaporizer is aluminum chloride. In certain embodiments, the metal is aluminum and the dopant material disposed in the vaporizer is aluminum iodide. In some embodiments, the metal is aluminum and the first gas source comprises an inert gas and the second gas source comprises dimethylaluminum chloride or trimethylaluminum chloride.

[0010] According to another embodiment, a method for operating an indirectly heated cathode ion source in multiple modes is disclosed, wherein the indirectly heated cathode ion source includes a controller, an arc chamber, a vaporizer, and a heater, the vaporizer is connected to the arc chamber, and the heater is used to heat the dopant material in the vaporizer. The method includes: selecting a desired mode of operation; and using the controller to configure the indirectly heated cathode ion source to operate in the desired mode, wherein for operation in a multi-charge mode, wherein the multi-charge mode is used to form ions with two or more charges of a species, the heater is actuated so that the vaporized dopant material containing a metal enters the arc chamber, and the controller causes the gas containing the metal to flow into the arc chamber; wherein in a first single charge mode, wherein the first single charge mode is used to form ions with a single charge of a species, the controller enables the heater and causes the inert gas to flow into the arc chamber; and wherein for operation in a second single charge mode, wherein the second single charge mode is used to form ions with a single charge of a species, the controller de-energizes the heater and uses the gas containing the metal to generate plasma. In some embodiments, the metal is aluminum and the dopant material disposed in the vaporizer is aluminum chloride. In some embodiments, the metal is aluminum and the dopant material disposed in the vaporizer is aluminum iodide. In some embodiments, the metal is aluminum and the gas containing the metal comprises dimethylaluminum chloride (DMAC) or trimethylaluminum chloride (TMAC).

[0011] According to another embodiment, an indirectly heated cathode ion source is disclosed. The indirectly heated cathode ion source includes: an arc chamber including a plurality of walls; a vaporizer in communication with the arc chamber; an indirectly heated cathode disposed in the arc chamber, wherein the indirectly heated cathode is used to generate a plasma in the arc chamber; and a controller configured to operate the indirectly heated cathode ion source in one of a plurality of modes, wherein in the multi-charge mode, the controller configures the indirectly heated cathode ion source so that two sources of metal are used to generate the plasma. In some embodiments, the metal is aluminum, the material disposed in the vaporizer comprises aluminum chloride, and wherein when operating in the multi-charge mode, a gas comprising aluminum is introduced into the arc chamber. In some embodiments, in the single charge mode, only one of the two sources is introduced into the arc chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference and in which:

[0013] Figure 1 An indirectly heated cathode (IHC) ion source having multiple operating modes according to one embodiment.

[0014] Figure 2 Show use Figure 1 Operation of the controller of the illustrated embodiment. DETAILED DESCRIPTION

[0015] As discussed above, certain dopants (eg, aluminum and other metals) utilize different mechanisms to form singly and multiply charged ions.

[0016] Figure 1 An IHC ion source 10 that overcomes these problems is shown. The IHC ion source 10 includes an arc chamber 100, which includes two opposite ends and walls 101 connected to the two ends. The walls 101 of the arc chamber 100 can be constructed of a conductive material and can be electrically connected to each other. In some embodiments, a lining can be provided near one or more of the walls 101. A cathode 110 is provided in the arc chamber 100 at a first end 104 of the arc chamber 100. A filament 160 is provided behind the cathode 110. The filament 160 is in communication 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 hot ion electrons. The cathode bias power supply 115 applies a negative bias to the filament 160 relative to the cathode 110 so that the hot ion electrons are accelerated from the filament 160 toward the cathode 110 and the cathode 110 is heated when the hot ions impact the rear surface of the cathode 110. Cathode bias power supply 115 may bias filament 160 so that filament 160 has a voltage, for example, between 200V and 1500V negative of the voltage of cathode 110. Cathode 110 then emits thermionic electrons into arc chamber 100 on its front surface.

[0017] Thus, the filament power supply 165 supplies current to the filament 160. The cathode bias power supply 115 biases the filament 160 so that the filament 160 has a negative value than the cathode 110, thereby attracting electrons from the filament 160 toward the cathode 110. In some embodiments, the cathode 110 may be biased relative to the arc chamber 100, for example, by the bias power supply 111. In other embodiments, the cathode 110 may be electrically connected to the arc chamber 100 to be at the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the bias power supply 111 may not be employed and the cathode 110 may be electrically connected to the wall 101 of the arc chamber 100. In some embodiments, the arc chamber 100 is connected to an electrical ground.

[0018] A repeller 120 may be disposed on a second end 105 opposite the first end 104. The repeller 120 may be biased relative to the arc chamber 100 by a repeller bias power supply 123. In other embodiments, the repeller 120 may be electrically connected to the arc chamber 100 to be at the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the repeller bias power supply 123 may not be employed, and the repeller 120 may be electrically connected to the wall 101 of the arc chamber 100. In still other embodiments, the repeller 120 is not employed.

[0019] The cathode 110 and the repeller 120 are each made of a conductive material (eg, metal or graphite).

[0020] In certain embodiments, a magnetic field is generated in the arc chamber 100. This magnetic field is intended to confine the electrons in one direction. The magnetic field is generally parallel to the wall 101 from the first end 104 to the second end 105. For example, the electrons may be confined in a column parallel to the direction from the cathode 110 to the repeller 120 (i.e., the Y direction). Thus, the electrons will not experience any electromagnetic forces to move in the Y direction. However, the movement of electrons in other directions may experience electromagnetic forces.

[0021] An extraction aperture 140 may be provided on one side of the arc chamber 100 (referred to as the extraction plate 103). Figure 1 , the extraction orifice 140 is arranged on the side parallel to the YZ plane (perpendicular to the page).

[0022] In addition, the IHC ion source 10 may be connected to at least two gas sources. The first gas source 170 may include a first gas, which may be an inert gas (e.g., argon). The flow of the first gas from the first gas source 170 to the IHC ion source 10 may be controlled by a first valve 171. The second gas source 175 may include a second gas that is an organoaluminum compound, which is a compound in which an aluminum atom is bonded to a carbon atom. In certain embodiments, the organoaluminum compound includes a halogen and aluminum. In certain embodiments, the second gas may be dimethylaluminum chloride (DMAC; (CH3)2AlCl) or trimethylaluminum chloride (TMAC; (CH3)3AlCl). Other gases including metal atoms bonded to carbon atoms may also be used. In some embodiments, the second gas includes carbon, a metal, and a halogen. The second gas source 175 may also include various diluent gases, such as hydrogen, argon, or other gases. In other words, the second gas source 175 includes the second gas, but may also include other gases. The flow of the second gas from the second gas source 175 to the ion source 10 may be controlled by a second valve 176. The first valve 171 and the second valve 176 may be mass flow controllers (MFCs) so that the flow rate can be controlled.

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

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

[0025] exist Figure 1 In the embodiment shown in , 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 multiple charge operation mode. Each of these modes will be described in more detail.

[0026] In a first single charge mode, filament power supply 165 passes current through filament 160, which causes filament 160 to emit thermionic electrons. These electrons strike the rear surface of cathode 110, which may have a more positive value than filament 160, causing cathode 110 to heat, which in turn causes cathode 110 to emit electrons into arc chamber 100. These electrons collide with molecules of a gas fed into arc chamber 100 through a gas inlet.

[0027] The controller 180 opens the first valve 171 to allow the first gas to flow into the arc chamber 100. The first gas may be an inert gas. The controller 180 also controls the heater 195 to heat the dopant material 197 in the vaporizer 190 to a temperature such that the dopant material 197 is vaporized and the vaporized dopant material enters the arc chamber 100 through the conduit 191. The combination of the electrons from the cathode 110, the first gas, and the vaporized dopant material forms a plasma. The ions in the plasma may be mainly singly charged ions, such as Al + In some embodiments, the electrons and positive ions may be confined to some extent by the magnetic field. In some embodiments, the plasma is confined near the center of the arc chamber 100, near the extraction orifice 140. Thus, in this first single charge mode, the metal is introduced only by the vaporized dopant material.

[0028] Therefore, when it is desired to form singly charged ions (such as Al + ), the operator may transmit this preference to the controller 180. Alternatively, the controller 180 may determine the desired mode based on the desired charge state and beam current. In response, the controller 180 may implement the above-described sequence of operations.

[0029] In the second single charge mode, the controller opens the second valve 176 to allow the second gas, which is a gas including the same metal as the dopant material 197, to flow into the arc chamber 100. The controller 180 also deenergizes the heater 195 so that no vapor from the vaporizer 190 enters the arc chamber 100. The second gas is ionized to produce metal ions that are primarily singly charged. In addition, if the second gas contains a halogen, the halogen in the second gas is used to recover the metal from the wall of the arc chamber 100. Therefore, in this second single charge mode, the metal is introduced only by the second gas. In some embodiments, the first valve 171 may be opened to allow the first gas to flow into the arc chamber 100. In other embodiments, the first valve 171 is closed.

[0030] In the multi-charge mode, the controller 180 opens the second valve 176 to allow the second gas to flow into the arc chamber 100. As described above, the second gas may be a gas that includes the same metal as the dopant material 197. For example, if the metal is aluminum, the second gas may be DMAC or TMAC. These gases may be used because they are efficient in recovering metal from the walls of the arc chamber 100. The controller also enables 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 as the 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 formed. Due to the density of the metal in the plasma, many of the ions formed in the plasma may be multiply charged ions, such as Al ++ or Al +++ The ions may then be extracted through extraction aperture 140 and used as an ion beam.

[0031] In some 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 the enhancement mode, the second valve 176 is opened, and the first valve 171 may be opened or closed.

[0032] Thus, when formation of multiply charged ions is desired, the operator may communicate this preference to the controller 180. Alternatively, the controller 180 may determine the desired mode based on the desired charge state and beam current. In response, the controller 180 may implement the above described sequence of operations.

[0033] Therefore, about Figure 1 In the embodiment shown in FIG. 1 , the present application describes three different operating modes that can be used to produce different charge states of desired dopants. In addition, by combining the first gas, the second gas, and the vaporizer 190 in communication with the arc chamber 100, the ion source 10 can be easily switched from one mode to another without operator intervention. Figure 2 1 shows the operation of the controller 180 controlling the mode of the ion source 10 when the vaporizer 190 is connected to the arc chamber 100. As shown in the box 200, the desired mode of operation can be selected depending on the recipe being used. This mode can be selected by an operator or user. Alternatively, the controller 180 can automatically select the most appropriate mode based on the desired beam current and 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 mode of operation. Typically, due to the limited loading of dopant material in the vaporizer 190, the second gas source will be used primarily for Al +Operation is to conserve dopant material in the gasifier 190 and effectively extend the life of the source.

[0034] As shown in box 210, a multi-charge mode can be selected in which plasma conditions are optimized for producing multi-charged metal ions. In response, the controller 180 opens the second valve 176 to allow the second gas (which is a gas including the same metal as the dopant material 197) to flow into the arc chamber 100. The controller 180 can open or close the first valve 171 as needed. The controller 180 also enables the heater 195 so that the 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. Because there are two sources of metal, the plasma is rich in metal ions. This metal-rich plasma efficiently forms multi-charged ions and can achieve more multi-charged ion current than using either metal source alone.

[0035] Alternatively, a first singly charged mode in which a majority of the metal ions have a single charge may be selected, as shown in box 220. In response, the controller 180 opens the first valve 171 to allow a first gas (which may be an inert gas, such as argon) to flow into the arc chamber 100. In this mode, the controller 180 enables the heater 195 so that vaporized dopant material enters the arc chamber 100 through the conduit 191. The inert gas is ionized in a plasma using the vaporized dopant material, wherein a majority of the ions formed are singly charged ions.

[0036] As shown in the grid 230, a second single charge mode can be selected in which most of the metal ions have a single charge. In the second single charge mode, the controller 180 de-energizes the heater 195 so that the vaporized dopant material does not enter the arc chamber 100. In addition, in this mode, the controller controls the second valve 176 to flow the second gas into the arc chamber 100. The second gas is ionized to produce metal ions that are mainly singly charged. In some embodiments, the first valve 171 is also opened to flow the first gas into the arc chamber 100. In other embodiments, the first valve is closed. In addition, the halogen in the second gas is used to recover the metal from the wall of the arc chamber 100. Therefore, in this second single charge mode, the metal is introduced only by the second gas.

[0037] Therefore, to operate in the multiple charge mode, the controller 180 configures the ion source 10 so that the metal is introduced by the second gas and the vaporized dopant material. To operate in the 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 the vaporized dopant material.

[0038] Although the above disclosure describes the use of a dopant material comprising aluminum as the solid compound in the vaporizer 190 and the use of a second gas comprising aluminum, other metals may 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 an 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 an 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 an organic lanthanum gas. Other metals may also be used.

[0039] The embodiments described above in this application may have many advantages. First, since the same ion source can be used to form singly charged ions and multiply charged ions, it is advantageous to form an ion source that can operate in multiple modes. In addition, the combination of a gasifier with a solid metal compound and a gas containing a metal has additional benefits.

[0040] First, the organoaluminum gas is available in a gas container, which is long-lived and easily replaceable. The organoaluminum gas also efficiently forms singly charged aluminum ions. Finally, the halogen in the organoaluminum gas also acts as an etchant to prevent aluminum from accumulating on the walls of the arc chamber 100.

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

[0042] Thus, this ion source is capable of producing singly or multiply charged ions of a selected species, where the species is a metal, such as aluminum, gallium, indium, or lanthanum.

[0043] The scope of the present disclosure is not limited by the specific embodiments described herein. In fact, from the foregoing description and the accompanying drawings, various other embodiments of the present disclosure and various modifications to the present disclosure in addition to the embodiments and modifications described herein will also be apparent to those skilled in the art. Therefore, these other embodiments and modifications are intended to fall within the scope of the present disclosure. In addition, although the present disclosure has been described herein in the context of a specific embodiment in a specific environment for a specific purpose, it should be recognized by those skilled in the art that its validity is not limited thereto and that the present disclosure can be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims set forth above should be interpreted in light of the full scope and spirit of the invention as described herein.

Claims

1. An indirect heating cathode ion source, comprising: an arc chamber comprising a plurality of walls; An indirectly heated cathode is disposed in the arc chamber; a vaporizer, connected to the arc chamber; a heater, for heating a dopant material disposed in the gasifier; a first valve in communication with the arc chamber and a first gas source; a second valve in communication with the arc chamber and a second gas source; and A controller is in communication with the first valve, the second valve, and the heater to operate the indirectly heated cathode ion source in one of a plurality of modes.

2. An indirect heated cathode ion source according to claim 1, wherein the multiple modes include two single charge modes and a multiple charge mode, the two single charge modes are used to form ions of species with a single charge, and the multiple charge mode is used to form ions of the species with two or more charges.

3. The indirectly heated cathode ion source of claim 2, wherein the species comprises a metal.

4. The indirectly heated cathode ion source of claim 2, wherein in a first single charge mode, the controller actuates the heater, opens the first valve, and closes the second valve.

5. The indirectly heated cathode ion source of claim 2, wherein in a second single charge mode, the controller deenergizes the heater and opens the second valve.

6. The indirectly heated cathode ion source of claim 5, wherein in the second single charge mode, the controller opens the first valve.

7. The indirectly heated cathode ion source of claim 2, wherein in the multiple charge mode, the controller actuates the heater and opens the second valve.

8. The indirectly heated cathode ion source of 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 a second gas contained in the second gas source.

9. The indirectly heated cathode of claim 8, wherein the metal is aluminum and the dopant material disposed in the gasifier is aluminum chloride.

10. The indirectly heated cathode of claim 8, wherein the metal is aluminum and the dopant material disposed in the gasifier is aluminum iodide.

11. The indirectly heated cathode ion source of claim 8, wherein the metal is aluminum, and the first gas source comprises an inert gas and the second gas source comprises dimethylaluminum chloride or trimethylaluminum chloride.

12. A method of 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, and a heater, wherein the vaporizer is in communication with the arc chamber, and the heater is used to heat a dopant material in the vaporizer, the method comprising: Select the desired mode of operation; as well as configuring the indirectly heated cathode ion source to operate in the desired mode using the controller, wherein operating in a multiple charge mode, wherein the multiple charge mode is used to form ions of species having two or more charges, the heater is actuated to cause vaporized dopant material containing a metal to enter the arc chamber, and the controller causes a gas containing the metal to flow into the arc chamber; wherein in a first single charge mode, wherein the first single charge mode is used to form ions of the species having a single charge, the controller enables the heater and causes the inert gas to flow into the arc chamber; and Wherein to operate in a second single charge mode, wherein the second single charge mode is used to form ions of the species having a single charge, the controller deenergizes the heater and generates a plasma using the gas containing the metal.

13. The method of claim 12, wherein the metal is aluminum and the dopant material disposed in the gasifier is aluminum chloride.

14. The method of claim 12, wherein the metal is aluminum and the dopant material disposed in the gasifier is aluminum iodide.

15. The method of claim 12, wherein the metal is aluminum and the gas containing the metal comprises dimethylaluminum chloride or trimethylaluminum chloride.

16. An indirect heating cathode ion source, comprising: an arc chamber comprising a plurality of walls; a vaporizer, connected to the arc chamber; an indirectly heated cathode disposed in the arc chamber, wherein the indirectly heated cathode is used to generate plasma in the arc chamber; as well as A controller is configured to operate the indirectly heated cathode ion source in one of a plurality of modes, wherein in a multiple charge mode, the controller configures the indirectly heated cathode ion source such that two sources of metal are used to generate a plasma.

17. An indirectly heated cathode ion source according to claim 16, wherein the metal is aluminum, the material disposed in the vaporizer comprises aluminum chloride, and wherein when operating in the multiple charge mode, a gas comprising aluminum is introduced into the arc chamber.

18. The indirectly heated cathode ion source of claim 16, wherein the metal is aluminum, the material disposed in the vaporizer comprises aluminum iodide, and wherein when operating in the multiple charge mode, a gas comprising aluminum is introduced into the arc chamber.

19. The indirectly heated cathode ion source of claim 16, wherein in a single charge mode, only one of the two sources is introduced into the arc chamber.

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