Ion source for generating an ion beam comprising a metal

Abstract

An ion source for generating an ion beam comprising a metal is disclosed. The ion source comprises an arc chamber and a crucible furnace. The arc chamber has an interior for containing a plasma and an extraction aperture for extracting an ion beam. The crucible furnace has a crucible furnace aperture in communication with the interior of the arc chamber. The crucible furnace comprises a path from the interior of the crucible furnace towards the interior of the arc chamber, and the temperature continuously increases along the path.

Description

[0001] This application claims priority to U.S. Patent Application No. 17 / 353,171, filed June 21, 2021, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] Embodiments of this disclosure relate to an ion source for generating an ion beam comprising a metal, and more specifically, to a crucible furnace for a metal in an ion source. Background Technology

[0003] Various types of ion sources can be used to generate ions for use in semiconductor processing devices. For example, an indirectly heated cathode (IHC) ion source operates by supplying current to a filament positioned behind the cathode. The filament emits thermionic electrons that are accelerated toward and heat the cathode, causing the cathode to emit electrons into an arc chamber of the ion source. The cathode is positioned at one end of the arc chamber. A reflector is typically positioned at the end of the arc chamber opposite the cathode. The cathode and reflector can be biased to expel electrons, thereby guiding them back to the center of the arc chamber. In some embodiments, a magnetic field is used to further confine the electrons within the arc chamber.

[0004] In some embodiments, it may be necessary to utilize a feed material in solid form as the dopant material. For example, the solid feed material can serve as a sputtering target. Ions bombard the solid feed material, emitting a neutral component that can then be ionized and energized in the plasma and used for deposition or implantation. However, there are problems associated with using solid feed materials. For example, in the high-temperature environment of an IHC ion source, metal sputtering targets are prone to melting, dripping, and often degrading and damaging the arc chamber as the liquid metal spreads and accumulates within it. Therefore, ceramics containing the dopant of interest are often used as solid dopant materials because of their high melting temperature. However, these ceramic materials typically produce a lower beam current for the dopant of interest. If the metal sputtering target can maintain its shape without dripping or deforming upon melting, a significant increase in the dopant beam current can be achieved.

[0005] Therefore, it would be beneficial to have an advanced crucible furnace design that can be used within an ion source without these limitations. Summary of the Invention

[0006] A crucible furnace is disclosed that utilizes observations of molten metal tending to flow towards its hottest region. The crucible furnace includes an interior in which doped materials can be placed. The crucible furnace has a path leading from the interior to an orifice, along which the temperature continuously increases. The orifice may be located inside or near the arc chamber of an ion source. Liquid metal flows along the path toward the arc chamber, where it is vaporized and subsequently ionized. Overflow can be reduced by controlling the flow rate along the path. In another embodiment, an inverted crucible furnace is disclosed. The inverted crucible furnace includes a closed end communicating with the interior of the ion source, such that the closed end is the hottest region of the crucible furnace. The furnace opening is positioned on a different wall at a lower temperature to allow vapor to exit the crucible furnace.

[0007] According to one embodiment, an ion source for generating an ion beam comprising a metal is disclosed. The ion source includes: an arc chamber having an interior for containing plasma and an extraction orifice for extracting the ion beam; and a crucible furnace having a crucible furnace orifice communicating with the interior of the arc chamber, wherein the crucible furnace includes a path from the interior of the crucible furnace toward the interior of the arc chamber, wherein the temperature continuously increases along the path. In some embodiments, the path extends into the interior of the arc chamber. In some embodiments, the metal includes aluminum, gallium, lanthanum, or indium. In some embodiments, the path includes a wicking rod having a first end disposed within the interior of the crucible furnace and a tip near the crucible furnace orifice. In some embodiments, the path includes a hollow tube.

[0008] According to another embodiment, an ion source for generating an ion beam comprising a metal is disclosed. The ion source includes: an arc chamber having an interior for containing plasma and an extraction orifice for extracting the ion beam; a crucible furnace having a crucible furnace orifice communicating with the interior of the arc chamber; and a wicking rod having a first end disposed within the interior of the crucible furnace and a tip proximate to the crucible furnace orifice. In some embodiments, the tip extends beyond the crucible furnace orifice and into the interior of the arc chamber. In some embodiments, the first end of the wicking rod is attached to a rear wall of the crucible furnace. In some embodiments, the ion source includes a porous material disposed within the interior of the crucible furnace and prior to the crucible furnace orifice, wherein the porous material has an opening through which the wicking rod passes. In some embodiments, the wicking rod comprises a straight, solid cylinder. In some embodiments, the wicking rod includes at least one bend. In some embodiments, the wicking rod includes at least one upwardly inclined portion, wherein the inclination of the at least one upwardly inclined portion allows liquid metal to flow from the interior of the crucible furnace toward the tip. In some embodiments, the crucible furnace includes a front wall containing a crucible furnace orifice, and a wicking rod rests on an inner surface of the crucible furnace, inclined upwards, and resting on the front wall. In some embodiments, a first end of the wicking rod is not attached to the inner surface of the crucible furnace. In some embodiments, the wicking rod rests on the inner surface of the crucible furnace, inclined upwards, and resting on a porous material.

[0009] According to another embodiment, an ion source for generating an ion beam comprising a metal is disclosed. The ion source includes: an arc chamber having an interior for containing plasma and an extraction orifice for extracting the ion beam; and a crucible furnace having a closed end communicating with the interior of the arc chamber, wherein the crucible furnace includes a crucible furnace opening on a wall different from the closed end, through which metal vapor exits and enters the arc chamber. In some embodiments, the crucible furnace opening is disposed on a wall having a lower temperature than the closed end. In some embodiments, the crucible furnace opening is disposed on a wall opposite the closed end. In some embodiments, the ion source includes a channel communicating with both the crucible furnace opening and the interior of the arc chamber, such that vapor passes through the channel into the arc chamber. In some embodiments, the ion source includes a porous material disposed within the interior of the crucible furnace near the crucible furnace opening, such that vapor passes through the porous material before exiting through the crucible furnace opening. Attached Figure Description

[0010] For a better understanding of this disclosure, reference will be made to the accompanying drawings, which are incorporated herein by reference, and in the drawings:

[0011] Figure 1 An IHC source electrode with a crucible furnace is shown according to one embodiment;

[0012] Figure 2A A crucible furnace according to a second embodiment is shown;

[0013] Figure 2B A crucible furnace according to a third embodiment is shown;

[0014] Figure 2C A crucible furnace according to a fourth embodiment is shown;

[0015] Figure 2D A crucible furnace according to a fifth embodiment is shown; and

[0016] Figure 3 An inverted crucible furnace according to one embodiment is shown. Detailed Implementation

[0017] As described above, if the temperature inside the arc chamber or other processing chamber exceeds the melting point of the metal, there can be problems with the metal sputtering target. In this case, the metal sputtering target can become molten and drip into the arc chamber, potentially damaging the arc chamber and reducing its lifespan.

[0018] Furthermore, tests have revealed an unexpected tendency for liquid metal to migrate towards the region of highest temperature. Therefore, in some embodiments, liquid metal can effectively overcome gravity and travel towards hotter regions.

[0019] This behavior makes it difficult to effectively contain liquid metal while simultaneously exposing it to plasma to make the metal ionizable.

[0020] Therefore, in some embodiments, crucible furnaces can be designed to take this behavior into account. Figure 1 The diagram shows such a crucible furnace combined with an indirect-heated cathode (IHC) ion source. Although an IHC ion source is described, it should be understood that the crucible furnace can be used in conjunction with a Bernas ion source, a plasma chamber, or another ion source.

[0021] Figure 1 An ion source utilizing a crucible furnace is illustrated. The IHC ion source 10 includes an arc chamber 100 comprising two opposing ends and walls 101 connected to these ends. The walls 101 of the arc chamber 100 may be constructed of a conductive material and may be electrically connected to each other. In some embodiments, a liner may be disposed close to one or more of the walls 101. The liner may cover all of one or more of the walls 101, such that one or more walls 101 are not subjected to the harsh environment within the arc chamber 100. A cathode 110 is disposed in the arc chamber 100 at a first end 104 of the arc chamber 100. A filament 160 is disposed behind the cathode 110. The filament 160 is connected to a filament power supply 165. The filament power supply 165 is configured to allow current to flow through the filament 160, causing the filament 160 to emit thermionic electrons. The cathode bias power supply 115 negatively biases the filament 160 relative to the cathode 110, causing the thermionic electrons to accelerate from the filament 160 toward the cathode 110 and heat the cathode 110 as they impact its back surface. The cathode bias power supply 115 can bias the filament 160 such that it has a voltage more negative than that of the cathode 110, for example, between 200 volts and 1500 volts. The cathode 110 then emits thermionic electrons from its front surface into the arc chamber 100.

[0022] Therefore, 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 is more negative 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 an arc power supply 111. In other embodiments, the cathode 110 may be electrically connected to the arc chamber 100 so as to be at the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the arc 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 some embodiments, the arc chamber 100 is connected to electrical ground.

[0023] A reflector 120 may be disposed on a second end 105 opposite to the first end 104. The reflector 120 may be biased relative to the arc chamber 100 by means of a reflector bias power supply 123. In other embodiments, the reflector 120 may be electrically connected to the arc chamber 100 so as to be at the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the reflector bias power supply 123 may not be used, and the reflector 120 may be electrically connected to the wall 101 of the arc chamber 100. In still other embodiments, the reflector 120 is not used.

[0024] The cathode 110 and the reflector 120 are each made of a conductive material, such as metal or graphite.

[0025] In some embodiments, a magnetic field is generated in the arc chamber 100. This magnetic field is intended to confine electrons in one direction. The magnetic field typically extends parallel to the wall 101 from the first end 104 to the second end 105. For example, electrons can be confined in a column parallel to the direction from the cathode 110 to the reflector 120 (i.e., the y-direction). Therefore, electrons do not experience any electromagnetic force to move in the y-direction. However, movement of electrons in other directions may be subject to electromagnetic forces.

[0026] An extraction port 140 may be located on one side of the extraction plate 103, which is placed in the arc chamber 100. Figure 1 In this configuration, the extraction port 140 is positioned on a side parallel to the YZ plane (perpendicular to the page). Furthermore, the IHC ion source 10 also includes an inlet 106 through which the source gas to be ionized is introduced into the arc chamber 100.

[0027] The controller 180 may be connected to one or more power supplies, enabling modification of the voltage or current supplied by these power supplies. The controller 180 may include a processing unit, such as a microcontroller, personal computer, dedicated controller, or other suitable processing unit. The controller 180 may also include a non-transitory storage element, such as semiconductor memory, magnetic memory, or other suitable memory. This non-transitory storage element may contain instructions and other data that allow the controller 180 to perform the functions described herein.

[0028] The IHC ion source 10 also includes a crucible furnace 200. The crucible furnace 200 protrudes through one of the walls 101 into the arc chamber 100. This allows for... Figure 1 The wall 101 shown is opposite to the extraction port 140, or it may be a different wall 101.

[0029] The crucible furnace 200 includes outer walls 210. These outer walls 210 may be made of a material relatively unaffected by the plasma generated in the IHC ion source 10. Furthermore, the material used for the outer walls 210 may be compatible with liquid metals. For example, in one embodiment, the outer walls 210 may be graphite. These outer walls 210 define a cavity 212 in which the metal to be ionized is disposed. In some embodiments, the cavity 212 may have an inner diameter of 1 inch or less. In some embodiments, the length of the cavity 212 may be 1 inch or greater. However, other dimensions may also be utilized. The crucible furnace may be cylindrical, may be rectangular prism-shaped, or may have different shapes. Furthermore, the front wall 216 of the crucible furnace 200 includes a crucible furnace orifice 211. In this embodiment, this crucible furnace orifice 211 allows direct communication between the cavity 212 and the interior of the IHC ion source 10. In other words, the end of the crucible furnace with the crucible furnace orifice 211 may define a portion of one of the walls 101 of the IHC ion source 10.

[0030] The wicking rod 220 is disposed within the cavity 212. In some embodiments, the wicking rod 220 may be attached to the rear wall 213 of the crucible furnace 200 opposite the wall receiving the crucible furnace orifice 211. Alternatively, it may not be attached to the crucible furnace 200 and may be held in place by gravity. The wicking rod 220 may be made of graphite or tungsten. Other materials, such as carbides and nitrides, may also be used. Figure 1 In the illustrated embodiment, the wicking rod 220 is a straight, solid cylindrical structure. However, in other embodiments explained below, the wicking rod 220 may have different shapes. The length of the wicking rod 220 may be longer than the depth of the cavity 212, such that the tip 221 of the wicking rod 220 may extend beyond the crucible furnace 200 and into the IHC ion source 10. The diameter of the wicking rod 220 may be adjusted based on the application and the desired flow rate of the liquid metal. In some embodiments, a larger diameter may result in a higher flow rate.

[0031] For example, a metal dopant material 230 is disposed in the cavity 212. In one embodiment, the dopant material 230 is a solid metal, such as aluminum, gallium, lanthanum, or indium. This solid material can be extruded and wound onto the wick rod 220 in the form of a wire. In other embodiments, the solid material can be in the form of beads or hollow cylinders assembled around the wick rod 220.

[0032] During operation, the filament power supply 165 applies current through the filament 160, causing the filament 160 to emit thermionic electrons. These electrons strike the back surface of the cathode 110, which may be more orthogonal than the filament 160, causing the cathode 110 to heat up, which in turn causes the cathode 110 to emit electrons into the arc chamber 100. These electrons collide with molecules of the source gas fed into the arc chamber 100 through the inlet 106. The source gas may be, for example, a carrier gas such as argon, or an etching gas such as BF3, or other halogen species. The combination of electrons from the cathode 110, the source gas, and the positive potential generates plasma. In some embodiments, the electrons and positive ions may be confined to some extent by a magnetic field. In some embodiments, the plasma is confined near the center of the arc chamber 100 close to the extraction orifice 140. This plasma heats the tip 221 of the wicking rod 220, which is used to melt the dopant material 230 in the cavity 212. Because the tip 221 of the wicking rod 220 is at its highest temperature, the dopant material 230 tends to flow toward the tip 221 after melting. Since the tip 221 is located within the IHC ion source 10, the dopant material 230 is converted into a gaseous phase and ionized by chemical etching or sputtering with plasma. The ionized feed material can then be extracted through the extraction orifice 140 and used to generate an ion beam.

[0033] In some embodiments, the thermal conductivity between the wicking rod 220 and the rear wall 213 can be increased. For example, the cross-sectional area of ​​the wicking rod 220 may be smaller near the rear wall 213. This is done to ensure that the tip 221 is the hottest spot and that the dopant material 230 flows outward through the crucible furnace orifice 211.

[0034] Although Figure 1 An example of a crucible furnace is shown, but other variations are possible. For example, such as... Figure 2A As shown, porous material 240 may be contained within cavity 212 to accommodate dopant material 230. This porous material 240 may be sized such that it has the same outer dimensions as the inner dimensions of cavity 212. Furthermore, porous material 240 may have holes 241 passing through it. Porous material 240 may be positioned such that it is disposed between dopant material 230 and crucible furnace orifice 211. A wicking rod 220 may pass through the holes 241 in porous material 240. In this way, porous material 240 holds dopant material 230 within cavity 212 while allowing molten material to flow along wicking rod 220 toward tip 221. As... Figure 1 Similarly, the tip 221 can extend into the arc chamber 100 of the IHC ion source 10.

[0035] Figure 2B Show Figure 2AThe crucible furnace 200 shown is a variation. In this embodiment, the wicking rod 220 is supported closer to the bottom of the crucible furnace 201. For example, Figure 1 and Figure 2A A wicking rod 220 is shown positioned at or near the center of crucible furnace 200 and attached to the rear wall 213. This embodiment allows for greater utilization of the dopant material 230 disposed in cavity 212. Porous material 240 with orifice 241 is also disposed in cavity 212. In this embodiment, outer wall 210 may be formed such that bottom portion 215 of outer wall 210 extends outward beyond top portion of outer wall 210 and includes front wall 216 to form an open container 214 with crucible furnace orifice 211 adapted to hold any molten material falling from wicking rod 220. In some embodiments, bottom portion 215 of outer wall 210 extends beyond wall 101 of IHC ion source 10. Wicking rod 220 may extend into the volume defined by this open container 214, and also into the volume defined by wall 101.

[0036] It should be noted that this figure illustrates dopant material 230 configured as beads wound around wick 220 and positioned above the wire. However, dopant material 230 may be in any shape or multiple shapes.

[0037] also, Figure 1 , Figures 2A to 2B The wicking rod 220 is shown parallel to the main axis of the crucible furnace and perpendicular to the wall 101 of the IHC ion source 10. However, other variations are possible. For example, the wicking rod 220 may be attached to the rear wall 213 near the bottom of the crucible furnace and tilted upward as it moves toward the crucible furnace orifice 211. This tilt can be set to allow liquid metal to flow upward along the wicking rod 220 toward the tip 221.

[0038] In another embodiment, shown in Figure 2C In this embodiment, the wicking rod 220 may not be directly attached to the outer wall 210 of the crucible furnace 202, but rather remains unattached within the cavity 212 of the crucible furnace 202 and can be held in place by gravity. This allows the tip 221 of the wicking rod 220 to become hotter, as it no longer directly heat-sinks onto the rear wall 213. If the furnace orifice 211 of the furnace 202 is near the top of the furnace 202, this also allows the wicking rod 220 to naturally position itself on an upward slope. Thus, the wicking rod 220 rests on the inner surface of the furnace 202, angled upward through the furnace orifice 211, and rests on the front wall 216. In some embodiments, the wicking rod 220 is not attached to the inner surface. A porous material 240 with holes 241 is also disposed in the cavity 212. Figure 2BAs described, in this embodiment, the outer wall 210 may be formed such that the bottom portion 215 of the outer wall 210 extends outward beyond the top portion of the outer wall 210 to form an open container 214 having a crucible furnace orifice 211. In some embodiments, the bottom portion 215 of the outer wall 210 extends beyond the wall 101 of the IHC ion source 10. The wicking rod 220 may extend into the volume defined by this open container 214 and rest on the front wall 216 of the crucible furnace 202.

[0039] In another embodiment, the holes 241 in the porous material 240 can be positioned such that the wicking rod 220 is supported by the inner surface of the crucible furnace 202 and the porous material 240 and does not contact the front wall 216.

[0040] Although Figure 2C The crucible furnace 202 is shown to include a bottom portion 215 that extends further than the remainder of the outer wall 210; however, the embodiment is not limited to this one. For example, Figure 2A The crucible furnace shown can be used with Figure 2C The inclined wicking rod 220 shown is used together, wherein the crucible furnace orifice 211 may be located near the top of the front wall 216, such that the wicking rod 220 is inclined upward and rests on the front wall 216.

[0041] Furthermore, in another embodiment, the wicking rod 220 may be attached to the inner surface of the crucible furnace 202 and inclined upward toward the crucible furnace orifice 211, extending into the IHC ion source 10. In one embodiment, the wicking rod 220 may rest on the front wall 216, such as... Figure 2C As shown in the illustration. However, in other embodiments, similar to... Figure 2A In the embodiment shown, the core suction rod 220 can be separated from the front wall 216.

[0042] Figure 2D Another embodiment of the crucible furnace 203 is shown. In this embodiment, the outer wall 210 may be as described regarding... Figure 2B As described. However, in this embodiment, the wicking rod 260 is not a straight cylinder; instead, it may have a bend 263. For example, the wicking rod 260 may be positioned close to the bottom of the crucible furnace 202, but may be inclined upwards after passing through holes 241 in the porous material 240. This upward slope 262 allows the tip 221 of the wicking rod 220 to become hotter, thereby increasing the thermal gradient. This upward slope 262 may be at an angle that allows liquid metal to flow upwards toward the tip 261.

[0043] Of course, the wicking rod can be any suitable shape, such that it contacts the dopant material 230 and has a tip placed in or near the IHC ion source 10.

[0044] Furthermore, the flow rate of liquid metal along the wicking rod can be controlled by changing one or more of the following parameters: diameter, length, shape, surface finish, material, and porosity. For example, a larger diameter can support a higher flow rate of liquid material because of the larger surface area on the wicking rod 220. Additionally, a textured surface finish can slow down the flow rate of liquid material compared to a smooth surface finish.

[0045] Furthermore, the cross-section of the wicking rod 220 can vary along its length. For example, the tapered shape at the tip 221 can be used to limit the amount of liquid material that can flow into the arc chamber 100 and thereby control the vaporization rate of the liquid material.

[0046] Therefore, in each of these embodiments, the crucible furnace is designed to utilize observations of liquid metal flowing towards the hottest region, even against gravity, to do so. Thus, dopant material 230 is disposed within a cavity, providing a path to the interior of the IHC ion source 10, along which the temperature can be continuously increased to cause the liquid material to follow the path. Furthermore, the path can be designed such that the amount of material capable of flowing through it can be controlled. In other words, the flow rate through the path can be controlled. This allows for better control of the ionization rate and also reduces the possibility of overflow.

[0047] While wicking rods can be used to achieve these goals, other techniques can also be used that provide a path in which the temperature increases continuously. For example, hollow rods or tubes can be arranged such that the temperature gradient increases and the dopant material 230 travels through the interior of the rod.

[0048] The observation that liquid metal tends to flow towards hotter regions can also be used in other ways. For example, although... Figure 1 and Figures 2A to 2D Using this observation, liquid metal can be extracted into IHC ion source 10; other embodiments are also possible.

[0049] Figure 3 An inverted crucible furnace 300 is shown. In this embodiment, the inverted crucible furnace 300 is positioned such that the closed end 311 is disposed within the IHC ion source 10. The IHC ion source 10 is as described above.

[0050] In this way, since the closed end 311 is in communication with the interior of the arc chamber 100 of the IHC ion source 10, the closed end 311 can be the hottest surface. Therefore, the dopant material 330 will tend to flow toward the closed end 311. Since this closed end 311 has no opening, overflow is avoided. However, the heat from the closed end 311 can cause the dopant material 330 to vaporize. This vapor is then released and exits through the crucible furnace opening 312 at the cooler end of the inverted crucible furnace 300. The crucible furnace opening 312 can be positioned on the wall at a temperature lower than that of the closed end 311, so that the dopant material 330 is not drawn to the crucible furnace opening 312. In some embodiments, such as Figure 3 As shown, the furnace opening 312 is opposite the closed end 311. However, in other embodiments, the furnace opening 312 may be on a different wall 310, such as the top wall. Furthermore, a porous material 340 may be disposed near the furnace opening 312. The porous material 340 may be disposed between the furnace opening 312 and the dopant material 330 to minimize the flow of liquid material from the inverted furnace 300. Additionally, a channel 350 may be directed from the furnace opening 312 to the IHC ion source 10, allowing vapor to flow into the arc chamber 100. In some embodiments, the channel 350 is on the outside of the inverted furnace 300. Therefore, in this embodiment, the closed end 311 is used to extract liquid from the furnace opening 312, allowing vapor to exit the inverted furnace 300, but the liquid material is not extracted to the furnace opening 312.

[0051] Although Figure 1 The IHC ion source is disclosed herein, but it should be understood that any of the crucible furnaces described in the accompanying drawings can be used in conjunction with any ion source having an interior for containing plasma and having an extraction orifice. For example, the ion source can be a plasma chamber, a Berners-Stokes ion source, or another type of ion source.

[0052] The embodiments described above in this application have many advantages. First, this system allows solid metallic materials to be used as dopant materials without the problems associated with the prior art.

[0053] Specifically, in some embodiments, a path is formed from the cavity holding the dopant material to the IHC ion source 10, wherein the temperature increases continuously along the path. Because liquid metal tends to flow towards the hottest region, liquid material is drawn towards the IHC ion source. However, with proper design of this path, the flow rate of the liquid material towards the IHC ion source can be controlled, thus controlling the ionization rate and minimizing the possibility of overflow.

[0054] In other embodiments, the cavity containing the dopant material may have one end maintained at the highest temperature to attract the liquid. This serves to divert the liquid away from openings at different ends of the crucible furnace. In this way, vapor can escape from the openings while minimizing the possibility of the liquid leaving through the openings.

[0055] This disclosure should not be limited to the specific embodiments described herein. In fact, those skilled in the art will recognize various other embodiments and modifications of the invention besides those described herein, based on the foregoing description and drawings. Therefore, such other embodiments and modifications are intended to fall within the scope of this disclosure. Furthermore, although this disclosure has been described in the context of a specific implementation for a particular purpose and environment, those skilled in the art will recognize that its usefulness is not limited thereto, and that it can be advantageously implemented for any number of purposes and in any number of environments. Therefore, the claims set forth above should be interpreted in light of the full breadth and spirit of the disclosure as described herein.

Claims

1. An ion source for generating an ion beam comprising a metal, comprising: An arc chamber having an interior for containing plasma and an extraction port for extracting the ion beam; as well as A crucible furnace for containing the metal and having a crucible furnace orifice communicating with the interior of the arc chamber, wherein the crucible furnace includes a path along which liquid metal travels from the interior of the crucible furnace toward the interior of the arc chamber, wherein the temperature continuously increases along the path.

2. The ion source of claim 1, wherein the path extends into the interior of the arc chamber.

3. The ion source according to claim 1, wherein the metal comprises aluminum, gallium, lanthanum or indium.

4. The ion source of claim 1, wherein the path includes a wicking rod having a first end disposed within the interior of the crucible furnace and a tip near the orifice of the crucible furnace.

5. The ion source according to claim 1, wherein the path includes a hollow tube.

6. An ion source for generating an ion beam comprising a metal, comprising: An arc chamber having an interior for containing plasma and an extraction port for extracting the ion beam; A crucible furnace having a crucible furnace orifice communicating with the interior of the electric arc chamber; as well as The wicking rod has a first end disposed inside the crucible furnace and a tip near the orifice of the crucible furnace.

7. The ion source of claim 6, wherein the tip extends beyond the crucible furnace orifice and into the interior of the arc chamber.

8. The ion source of claim 6, wherein the first end of the wicking rod is attached to the rear wall of the crucible furnace.

9. The ion source of claim 6 further comprises a porous material disposed inside the crucible furnace and before the orifice of the crucible furnace, wherein the porous material has an opening through which the wicking rod passes.

10. The ion source according to claim 6, wherein the wicking rod comprises a straight solid cylinder.

11. The ion source according to claim 6, wherein the wicking rod includes at least one bent portion.

12. The ion source of claim 6, wherein the wicking rod includes at least one upwardly inclined portion, wherein the inclination of the at least one upwardly inclined portion causes liquid metal to flow from the interior of the crucible furnace toward the tip.

13. The ion source of claim 6, wherein the crucible furnace includes a front wall containing the orifice of the crucible furnace, and the wicking rod rests on the inner surface of the crucible furnace, is inclined upward, and rests on the front wall.

14. The ion source of claim 13, wherein the first end of the wicking rod is not attached to the inner surface of the crucible furnace.

15. The ion source according to claim 9, wherein the wicking rod rests on the inner surface of the crucible furnace, is inclined upward, and rests on the porous material.

16. An ion source for generating an ion beam comprising a metal, comprising: An arc chamber having an interior for containing plasma and an extraction port for extracting the ion beam; as well as A crucible furnace having a closed end communicating with the interior of the electric arc chamber, wherein the crucible furnace includes a crucible furnace opening on a wall different from the closed end, through which metal vapor exits and enters the electric arc chamber.

17. The ion source of claim 16, wherein the crucible furnace opening is disposed on a wall having a lower temperature than the closed end.

18. The ion source of claim 17, wherein the crucible furnace opening is disposed on a wall opposite to the closed end.

19. The ion source of claim 16, further comprising a channel communicating with the crucible furnace opening and the interior of the arc chamber, such that vapor passes through the channel to the arc chamber.

20. The ion source of claim 16 further comprises a porous material disposed within the interior of the crucible furnace near the furnace opening, such that the vapor passes through the porous material before exiting through the furnace opening.

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