Transport of molten liquid for adjustable vaporization in an ion source

Abstract

An ion source having a crucible is disclosed. In some embodiments, the crucible includes a solid dopant material such as a metal. A porous wicking chip is disposed within the crucible so as to contact the solid dopant material. The porous wicking chip can be a tube having one or more internal conduits. Alternatively, the porous chip can be two concentric cylinders. In that case, a plurality of rods are disposed within an annular ring between the two cylinders. Alternatively, the porous chip can be one or more foil layers wound together. In each of these multiple embodiments, the wicking chip can be used to control the flow rate of the molten dopant material to the arc chamber.

Description

Technical Field

[0001] This application claims the priority of U.S. Patent Application No. 17 / 835,107, filed on June 8, 2022, the disclosure of which is incorporated herein by reference in its entirety.

[0002] Embodiments of the present disclosure relate to ion sources, and more particularly to ion sources having a crucible with a porous wicking tip.

Background Art

[0003] Ions used in semiconductor processing apparatuses can be generated using various types of ion sources. 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 thermionic electrons, which are accelerated towards the cathode to heat the cathode, which in turn emits electrons into the arc chamber of the ion source. The cathode is disposed at one end of the arc chamber. A repeller is typically 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 electrons within the arc chamber.

[0004] In certain embodiments, it may be desirable to utilize a solid feed material as a dopant species. However, there are problems with using a solid feed material in an IHC ion source. For example, the vaporizer used in the ion source is difficult to operate at temperatures above 750 degrees Celsius. Additionally, there can be problems with heat insulation and condensation within the tube connecting the vaporizer and the arc chamber. These problems can prevent the use of many solids within the vaporizer, as their vapor pressures are too low at 750 degrees Celsius. There can also be problems with introducing the solid feed material into the ion source, such as spillage and unregulated vaporization.

[0005] Thus, it would be beneficial to have an ion source that can be used with such solid feed materials without such limitations. Further, it may be advantageous if the rate of vaporization can be finely tuned or adjusted. SUMMARY OF THE INVENTION

[0006] An ion source having a crucible is disclosed. In some embodiments, the crucible contains a solid dopant material such as a metal. This material can be a crystal, a mass, a powder, or a compound material. A porous wicking tip is disposed within the crucible so as to be in contact with the solid dopant material. The porous wicking tip can be a tube having one or more internal conduits. Alternatively, the porous tip can be two concentric cylinders. In that case, a plurality of rods are disposed within the annular ring between the two cylinders. Alternatively, the porous tip can be one or more foil layers wound together. In each of these embodiments, the wicking tip is used to control the flow rate of the molten dopant material into the arc chamber.

[0007] According to another embodiment, an apparatus for holding a dopant material within an ion source is disclosed. The apparatus includes a crucible and a wicking tip disposed within the crucible. In that case, the wicking tip includes a body having one or more internal conduits, one or more openings enabling the one or more internal conduits to communicate with the exterior of the body and the interior of the crucible, and a wicking cavity disposed at the front end of the wicking tip, the one or more internal conduits converging into the wicking cavity. In some embodiments, the body includes a cylindrical portion including a plurality of internal conduits. In certain embodiments, a portion of the body is defined to have a defined primary outer diameter such that a plurality of internal conduits are completely contained within a portion having the primary outer diameter. In that case, a transport ring, which is a region having a diameter smaller than the primary outer diameter, is disposed in another portion of the body to form one or more openings. In certain embodiments, the cross-sectional area of the passage where the plurality of internal conduits connect to the wicking cavity is smaller than the total cross-sectional area of the plurality of internal conduits so as to form a choke point.

[0008] In some embodiments, the total cross-sectional area of the plurality of internal conduits is 3 to 12 times larger than the cross-sectional area of the passage where the plurality of internal conduits connect to the wicking cavity. In some embodiments, the body and the one or more internal conduits are curved. In some embodiments, the wicking cavity includes a concave cavity. In some embodiments, the body includes exactly one internal conduit. In some embodiments, the body includes a hollow outer cylinder and a solid inner cylinder. In that case, an annular ring is formed between the hollow outer cylinder and the solid inner cylinder, and the wicking tip further includes a plurality of rods disposed within the annular ring, and the gaps between the plurality of rods within the annular ring include one or more internal conduits. In some embodiments, the body includes a foil wound to form the body. In that case, the gaps between adjacent layers of the foil include one or more internal conduits.

[0009] According to another embodiment, an indirectly heated cathode ion source is disclosed. The IHC ion source includes an arc chamber having a first end and a second end, a cathode disposed at the first end, and the above-described device disposed at the second end.

[0010] According to another embodiment, an indirectly heated cathode ion source is disclosed. The IHC ion source includes an arc chamber having a first end, a second end, and a sidewall connecting the first end and the second end, a cathode disposed at the first end, an actuator extending into the arc chamber and configured to retract from the arc chamber, and the above-described device disposed at one end of the actuator.

[0011] According to another embodiment, a device for holding a dopant material within an ion source is disclosed. The device includes a crucible and a wicking tip disposed within the crucible. In that case, the wicking tip includes a solid inner cylinder disposed within a hollow outer cylinder to form an annular ring, and a plurality of rods disposed within the annular ring. In some embodiments, the gaps between the plurality of rods form internal conduits through which the dopant material moves. In some embodiments, the plurality of rods extend beyond the hollow outer cylinder at the rear end of the wicking tip to provide an opening for enabling the dopant material to enter the internal conduits. In some embodiments, the hollow outer cylinder extends further forward than the plurality of rods to form a cavity into which the dopant material collects from the internal conduits. In some embodiments, the plurality of rods include tantalum, a high melting point metal, or a high temperature wire.

[0012] According to another embodiment, an indirectly heated cathode ion source is disclosed. The IHC ion source includes an arc chamber having a first end and a second end, a cathode disposed at the first end, and the above-described device disposed at the second end.

[0013] According to another embodiment, an indirectly heated cathode ion source is disclosed. The IHC ion source includes an arc chamber having a first end, a second end, and a sidewall connecting the first end and the second end, a cathode disposed at the first end, an actuator configured to extend into the arc chamber and retract from the arc chamber, and the above-described device disposed at one end of the actuator.

[0014] To better understand the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2A

Figure 2B

Figure 3A

Figure 3B

Figure 3C

Figure 3D

Figure 3E

Figure 4A

Figure 4B

Figure 4C

Figure 4D

Figure 4E

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0016] As described above, a crucible having a wicking chip is disclosed. There are several embodiments of the wicking chip.

[0017] There are several embodiments of the IHC ion source that can be used with the wicking chip. One of these embodiments includes a crucible disposed at the second end of the arc chamber. The second embodiment includes a crucible disposed on the side wall. Each of these embodiments will be described in more detail.

[0018] FIG. 1 shows a first embodiment of an IHC ion source 10 having a crucible with a wicking tip. In that case, the crucible is arranged at the second end. The IHC ion source 10 includes an arc chamber 100 including two opposing ends and a wall 101 connecting these ends. The arc chamber 100 also includes a lower wall and an upper wall. The walls of the arc chamber 100 may be constructed of a conductive material and may be electrically connected to each other. A cathode 110 is disposed within 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 pass a current through the filament 160. Thereby, the filament 160 emits thermoelectrons. A cathode bias power supply 115 biases the filament 160 negatively with respect to the cathode 110. Thus, these thermoelectrons are accelerated from the filament 160 toward the cathode 110, and when these thermoelectrons hit the back surface of the cathode 110, the cathode 110 is heated. The cathode bias power supply 115 may bias the filament 160 to have a voltage in the negative direction, for example, between 200V and 1500V lower than the voltage of the cathode 110. Then, the cathode 110 emits the hot ionic electrons on its front surface into the arc chamber 100.

[0019] Therefore, the filament power supply 165 supplies current to the filament 160. The cathode bias power supply 115 biases the filament 160. Thereby, the filament 160 becomes negative relative to the cathode 110. As a result, electrons are attracted from the filament 160 toward the cathode 110. In certain embodiments, the cathode 110 may be biased with respect to the arc chamber 100 by a bias power supply 111 or the like. In other embodiments, the cathode 110 may be electrically connected to the arc chamber 100 such that it has the same voltage as the side wall 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 side wall of the arc chamber 100. In a particular embodiment, the arc chamber 100 is electrically grounded.

[0020] In this embodiment, the crucible 120 is disposed within the arc chamber 100 at the second end 105 of the arc chamber 100 that faces the cathode 110. The crucible 120 may be made of a conductive material and may be electrically connected to the side wall of the arc chamber 100. The upper portion of the crucible 120 may be planar with the second end 105.

[0021] In certain embodiments, a magnetic field 190 is generated within the arc chamber 100. This magnetic field is intended to confine electrons along one direction. The magnetic field 190 typically passes parallel to the side wall 101 from the first end 104 to the second end 105. For example, electrons may be confined within a column parallel to the direction from the cathode 110 to the crucible 120 (i.e., the y direction). Thus, the electrons do not receive any electromagnetic force in the y direction. However, the movement of electrons in other directions may be subject to electromagnetic force.

[0022] In one embodiment shown in FIG. 1, the first electrode 130a and the second electrode 130b can be disposed on respective opposing sidewalls 101 of the arc chamber 100. Thereby, the first electrode 130a and the second electrode 130b are within the arc chamber 100. The first electrode 130a and the second electrode 130b can each be biased by respective power supplies. In certain embodiments, the first electrode 130b and the second electrode 130b may communicate with a common power supply. However, in other embodiments, to allow for maximum flexibility and the ability to adjust the output of the IHC ion source 10, the first electrode 130a may communicate with the first electrode power supply 135a, and the second electrode 130b may communicate with the second electrode power supply 135b.

[0023] The first electrode power supply 135a and the second electrode power supply 135b each serve to bias the first electrode 130a and the second electrode 130b with respect to the sidewall of the arc chamber 100. In certain embodiments, the first electrode power supply 135a and the second electrode power supply 135b can bias the first electrode 130a and the second electrode 130b positively or negatively with respect to the sidewall 101 of the arc chamber 100. In certain embodiments, at least one of the electrodes can be biased between 40 and 500 volts with respect to the sidewall 101 of the arc chamber 100.

[0024] Each of the cathode 110, the crucible 120, and the electrodes is made of a conductive material such as metal or graphite.

[0025] An extraction opening 140 may be disposed on another side of the arc chamber 100 called the faceplate 103. In FIG. 1, the extraction opening 140 is disposed on a side parallel to the X-Y plane (parallel to the page). Further, the IHC ion source 10 also includes a gas inlet 106 through which the gas to be ionized is introduced into the arc chamber 100.

[0026] Controller 180 may be connected to one or more of the power supplies. Thereby, the voltage or current supplied by these power supplies may be modified. Controller 180 may include a processing unit such as a microcontroller, a personal computer, a dedicated controller, or another suitable processing unit. Controller 180 may also include a non - transient storage element such as a semiconductor memory, a magnetic memory, or another suitable memory. This non - transient storage element may contain instructions and other data that enable Controller 180 to perform the functions described herein.

[0027] A dopant material 125 such as indium, aluminum, antimony, or gallium may be disposed within crucible 120. The dopant material 125 may be in a solid state when disposed within crucible 120. In some embodiments, the dopant material 125 can be a crystal, a lump, a powder, or a compound material. However, in certain embodiments, the dopant material 125 may melt and become a liquid. Thus, in certain embodiments, ion source 10 is configured such that crucible 120 is disposed on its lowest side (i.e., the side closest to the ground). Thereby, the melted dopant material does not flow from crucible 120 into arc chamber 100, but rather remains within crucible 120. In other words, ion source 10 is oriented such that dopant material 125 is held within crucible 120 by gravity.

[0028] The wicking tip 170 is disposed within the crucible 120. The wicking tip 170 extends into the crucible 120. In some embodiments, the wicking tip 170 extends to the bottom of the crucible. Thereby, the dopant material 125 is maintained in contact with the wicking tip 170 even as it is consumed. The crucible 120 may include a front face that forms a crucible cavity 121. This crucible cavity 121 may be a recess or another inwardly directed depression. The front face refers to the face that communicates with the interior of the arc chamber 100. In certain embodiments, the wicking tip 170 includes a wicking cavity 171. The wicking cavity 171 may be a recess. However, it will be understood that other shapes may also be used. For example, the wicking cavity 171 may be a counterbore having various shapes. Any inwardly directed depression or hole in the front face may serve as the wicking cavity 171. In some embodiments, both the crucible 120 and the wicking tip 170 have concave cavities. In each of a plurality of embodiments, heat from the plasma draws the molten dopant material towards the arc chamber. As the dopant material 125 rises up the wicking tip 170, it fills the wicking cavity 171. If an excess amount of dopant material fills the wicking cavity 171, a meniscus may form. With the introduction of additional dopant material, the dopant material may flow from the wicking cavity 171 into the crucible cavity 121. Both of these cavities may be in direct contact with the interior of the arc chamber 100. Thereby, vaporization of the dopant material within the crucible cavity 121 and the wicking cavity 171 is promoted. Further, the design of the wicking tip 170 may control the rate at which the dopant material 125 rises up the wicking tip 170 and thus the rate at which the dopant material 125 vaporizes.

[0029] During operation, the filament power supply 165 passes current through the filament 160, causing the filament 160 to emit thermionic electrons. These electrons strike the back surface of the cathode 110, which can be positive relative to the filament 160, heating the cathode 110, which then in turn causes the cathode 110 to emit 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 106. A carrier gas such as argon, or an etching gas such as a halogen-containing gas, can be introduced into the arc chamber 100 through the appropriately positioned gas inlet 106. The combination of electrons from the cathode 110, the gas, and the positive potential generates the plasma 145. The plasma 145 can be confined and manipulated by the electric field generated by the first electrode 130a and the second electrode 130b. Further, in certain embodiments, the electrons and positive ions can be somewhat confined by the magnetic field 190. In certain embodiments, the plasma 145 is confined near the center of the arc chamber 100, near the extraction aperture 140. In some embodiments, the plasma 145 can be biased at a voltage close to the average of the voltages applied to the first electrode 130a and the second electrode 130b. The heat within the plasma 145 melts the dopant material 125 within the crucible 120 to produce a liquid. The heat draws the liquid towards the arc chamber. Thereby, the liquid rises up the wicking tip 170 and flows into the wicking cavity 171. Upon entering the wicking cavity 171, the liquid dopant material vaporizes, ions are generated from the dopant material, and become part of the plasma 145. Alternatively, a portion of the liquid dopant material may flow from the wicking cavity 171 into the crucible cavity 121 and vaporize there.

[0030] In certain embodiments, the voltage of the cathode 110 is not more positive than the voltage of the plasma 145. For example, in one embodiment, the cathode 110 can have the same voltage as the sidewall of the arc chamber 100. The first electrode 130a is biased to 150V, while the second electrode 130b can be biased to 0V or 20V. Thus, the electrons generated by the cathode 110 are drawn towards the plasma 145. In some embodiments, these emitted electrons or other particles can also collide with the dopant material 125, causing sputtering.

[0031] Although FIG. 1 shows two electrodes, it will be understood that one of these electrodes, such as the second electrode 130b, and the associated second electrode power supply 135b can be eliminated in some embodiments. In another embodiment, the second electrode 130b is disposed within the arc chamber 100 but is electrically connected to the sidewall 101 of the arc chamber 100. Thus, in this embodiment, the second electrode power supply 135b can be eliminated.

[0032] Figures 2A - 2B show a second embodiment of the IHC ion source 12 utilizing the crucible 120 with the wicking tip 170. Many of the components within this IHC ion source 12 are the same as those in the first embodiment and are given the same reference numerals. Different from the IHC ion source 10 shown in FIG. 1, in this embodiment, the reflection electrode 150 is disposed at the second end 105. The second end 105 is opposite to the first end 104. The reflection electrode 150 can be biased with respect to the arc chamber 100 by the reflection electrode bias power supply 153. In other embodiments, the reflection electrode 150 can be electrically connected to the arc chamber 100 such that it has the same voltage as the wall of the arc chamber 100. In these embodiments, the reflection electrode bias power supply 153 may not be employed, and the reflection electrode 150 can be electrically connected to the wall of the arc chamber 100. In still other embodiments, the reflection electrode 150 is not employed. The reflection electrode 150 is made of a conductive material such as metal or graphite.

[0033] In this embodiment, the crucible 120 communicates with one end of the actuator 195. FIG. 2A shows the actuator 195 in an extended position such that the crucible 120 is disposed inside the arc chamber 100. The other end of the actuator 195 may communicate with the support 197. In certain embodiments, this support 197 can be the housing of the IHC ion source 12. In certain embodiments, the actuator 195 can change its entire displacement. For example, the actuator 195 can have a telescopic design.

[0034] FIG. 2B shows the IHC ion source 12 with the actuator 195 in a retracted position. In this position, the crucible 120 is completely outside the arc chamber 100. In certain embodiments, the dopant material 125 is cooled when the crucible 120 is outside the arc chamber 100. In this way, when the actuator 195 is in the retracted position, the dopant material 125 does not enter the arc chamber 100 at all.

[0035] The crucible 120 enters the interior of the arc chamber 100 through one of the plurality of sidewalls 101 that connect the first end 104 and the second end 105. In certain embodiments, the crucible 120 can enter the interior of the arc chamber 100 through the sidewall facing the extraction opening 140. In other embodiments, the crucible 120 can enter the interior of the arc chamber 100 through the sidewall adjacent to the faceplate 103.

[0036] The wicking chip 170 is disposed within the crucible 120. The wicking chip 170 extends into the crucible 120. In some embodiments, the wicking chip 170 extends to the bottom of the crucible. Thereby, the dopant material 125 is maintained in contact with the wicking chip 170 even as it is consumed. The crucible 120 may include a front face that forms the crucible cavity 121. In certain embodiments, the wicking chip 170 includes a wicking cavity 171. In some embodiments, both the crucible and the wicking chip have cavities. In each of the embodiments, when the dopant material 125 rises on the wicking chip 170, it fills the wicking cavity 171. If an excess amount of dopant material fills the wicking cavity 171, a meniscus may form. With the introduction of further dopant material, the dopant material may flow from the wicking cavity 171 into the crucible cavity 121. Both of these cavities may be in direct contact with the interior of the arc chamber 100. Thereby, the vaporization of the dopant material within the crucible cavity 121 and the wicking cavity 171 is promoted. Further, the design of the wicking chip 170 can control the rate at which the dopant material 125 rises on the wicking chip 170 and thus the rate at which the dopant material 125 vaporizes.

[0037] Figures 3A - 3E show a first embodiment of the wicking chip 170. In this embodiment, the wicking chip 170 includes a wicking tube 200. As seen in FIGS. 3A - 3B, the wicking tube 200 can be a cylindrical body having a length and a primary outer diameter. One or more transport rings 210 are included along the length of the wicking tube 200. The transport ring 210 is a region having an outer diameter smaller than the primary outer diameter. In some embodiments, the primary outer diameter 231 (see FIG. 3D) is between 0.125 and 0.75 inches. On the other hand, the outer diameter of the transport ring 210 is between 0.087 and 0.62 inches. The height of the transport ring 210 is not limited and can be between 0.25 and 2.0 inches depending on the desired flow rate. Specifically, increasing the height of the transport ring 210 increases the size of the opening connecting the outside of the wicking tube 200 to the conduit 220.

[0038] One or more conduits 220 are present within the wicking tube 200. The diameters of these conduits 220 can vary and, in some embodiments, can be between 0.062 and 0.250 inches. These conduits 220 are completely contained within the primary outer diameter 231 as shown in the top view of FIG. 3B and in FIG. 3D. In other words, if the entire wicking tube 200 has a diameter equal to the primary outer diameter 231, the conduit 220 can fit completely within the cylinder. However, the outer diameter of the transport ring 210, shown as diameter 232 in FIG. 3E, is smaller than the diameter required to contain the conduit 220. Eventually, the transport ring 210 bites into the conduit 220, forming an opening 250 that secures a path from the outside of the wicking tube 200 to the conduit 220.

[0039] Figures 3D - 3E also show the wicking cavity 230. Where the wicking cavity 230 overlaps with the conduit 220, a passage from the conduit 220 to the wicking cavity 230 is formed. Since the cross-sectional area of these passages is smaller than the total cross-sectional area of the plurality of conduits 220, a choke point is formed. The size of the choke point and the ratio of the cross-sectional area of the passages to the total cross-sectional area of the plurality of conduits 220 can determine the flow rate of the dopant material into the wicking cavity 230.

[0040] There may be two or more conduits 220 within the wicking tube 200. In this way, a portion of the wicking tube 200 is also within the area of the transport ring 210.

[0041] In another embodiment, exactly one conduit 220 may be utilized. In this embodiment, instead of using a transport ring, radial openings 250 may be formed along the length of the wicking tube 200 to connect the outside of the wicking tube 200 to the conduit 220, as shown in Figure 4D. These openings 250 may be tapered to increase the amount of material that can enter each opening 250.

[0042] A variation of the wicking tube of Figure 4D is shown in Figure 4E. In this figure, there are a plurality of lower wicking tubes 201 that merge into an upper wicking tube 202. The lower wicking tubes 201 have openings 250 as shown in Figure 4D. In addition, the lower wicking tubes 201 also have one or more conduits 220 similar to those of Figure 4D. These conduits 220 then enter the upper wicking tube 202 and may remain as separate conduits within the upper wicking tube 202. In other embodiments, the conduits 220 may merge into one of the conduits within the upper wicking tube 202. At the upper part of the upper wicking tube 202, the conduits 220 connect to the wicking cavity 230.

[0043] The wicking tube 200 can be made of any suitable material such as graphite or a high melting point metal (such as tungsten, tantalum, or molybdenum). The length of the wicking tube 200 can be determined based on the depth of the crucible 120. The diameter of the conduit 220 can be selected to control the rate at which the liquid dopant material moves into the wicking cavity 230. A larger diameter allows more material to be transported and also increases the size of the opening connecting the outside of the wicking tube 200 to the conduit 220. Further, the number of conduits can be adjustable.

[0044] As seen in FIG. 3C, in all of these multiple embodiments, the front face of the wicking tube 200 can include the wicking cavity 230. The term "front face" refers to the face that communicates with the arc chamber 100. The wicking cavity 230 can be a recess. However, it will be understood that other shapes can also be used. For example, the wicking cavity 230 can be a counterbore having various shapes. Any inward depression or hole in the front face can serve as the wicking cavity 230. When the molten dopant material 125 rises through the conduit 220, it collects within the wicking cavity 230. The depth, shape, and radius of the wicking cavity 230 can be selected based on the amount of molten dopant material to be exposed to the plasma. The deeper the wicking cavity 230, the more dopant material can be held and the higher the concentration of dopant ions in the plasma can be.

[0045] In certain embodiments, the conduit 220 can extend distally from the wicking cavity 230 over the entire length of the wicking tube 200. In other embodiments, the rear end of the wicking tube 200 may be closed. Thereby, the conduit 220 is not exposed at the rear end. The term "rear end" refers to the end of the wicking tube 200 opposite the front face. However, in all embodiments, the wicking tube 200 comprises a structure having one or more conduits 220 disposed therein. These conduits 220 communicate with a wicking cavity 230 disposed on the front face of the wicking tube 200. Along the length of the wicking tube 200, one or more openings 250 may be disposed. The one or more openings 250 connect the exterior of the wicking tube 200 to the conduit 220. The number and size of the conduits 220 and openings can help determine the rate at which the dopant material moves into the wicking cavity 230.

[0046] Further, FIGS. 3A - 3E show the wicking tube 200 as having a cylindrical body, but other shapes are possible. For example, the wicking tube 200 may be a rectangular prism or another shape.

[0047] Figure 4A shows the wicking tube 200 of FIGS. 3A-3E disposed within crucible 120. Crucible 120 is partially filled with dopant material 125. It should be noted that during operation, the dopant material 125 melts, enters the opening 250 along the transport ring 210, and rises through conduit 220 to reach the wicking cavity 230. The wicking cavity 230 communicates with the arc chamber 100. The direction shown in FIG. 4A is appropriate for the ion source shown in FIG. 1. In that case, crucible 120 is maintained in an upright or vertical position. In this embodiment, the central axis of the wicking tube 200 can be coaxial with the central axis of crucible 120. Thereby, the wicking tube 200 is at the radial center of crucible 120. In these embodiments, crucible 120 can be a hollow cylinder or a hollow parallelepiped. In a plurality of other embodiments, crucible 120 can be tapered. Thereby, the upper portion of the crucible is wider than the lower portion of crucible 120.

[0048] Figure 4B shows the wicking tube 200 disposed within the crucible 120. The crucible 120 is oriented horizontally as performed in the embodiments shown in FIGS. 2A - 2B. In this embodiment, it may be beneficial to offset the wicking tube 200 from the central axis of the crucible 120. In this way, the dopant material 125 can be maintained in contact with the wicking tube 200 even as it is consumed. The wicking tube 200 can be disposed within the crucible 120. Thereby, the wicking tube 200 contacts or is near the lowest side surface of the crucible 120 if desired. In these embodiments, the crucible 120 can be a hollow cylinder or a hollow parallelepiped. In a plurality of other embodiments, the crucible 120 can be tapered. Thereby, the upper portion of the crucible is wider than the lower portion of the crucible 120. By using the taper, the dopant material 125 can be drawn towards the upper portion of the crucible 120 by the inclined walls of the crucible 120. The front surface of the crucible 120 can have a cavity. The cavity can be a recess, a protrusion, or a detailed surface. Thereby, any overflow of the dopant material 125 from the wicking cavity 230 can be retained.

[0049] Figure 4C shows a different wicking tube 240 that can be used with the crucible shown in FIG. 4B. In this embodiment, rather than moving the position of the wicking cavity 230 within the crucible 120 to correspond to the horizontal direction, the shape of the wicking tube 240 is changed. In this embodiment, the body of the wicking tube 240 is curved. The conduit 220 within the body can be curved as well. With this configuration, the front surface of the wicking tube 200 (i.e., the wicking cavity 230) can be disposed along the central axis of the crucible 120. On the other hand, it also allows at least a portion of the wicking tube to approach the lowest side surface of the crucible 120.

[0050] FIG. 4D shows a different configuration of the wicking tube 200. In this embodiment, rather than using a transport ring 210, the cross-sectional area of the body of the wicking tube can be constant through at least a portion of its length. An opening 250 is disposed within the wicking tube 200. The opening 250 is in communication with one or more conduits 220. The one or more conduits 220 are disposed within the cylinder of the wicking tube 200. As described above, these openings can be tapered to increase the amount of material that can enter each opening 250.

[0051] Figures 5A - 5C show a wicking chip according to another embodiment. In this embodiment, the wicking chip is constructed as a wicking wire assembly 300. Figure 5C shows a cross - sectional view of the wicking wire assembly 300. The wicking wire assembly 300 includes a solid inner cylinder 320 disposed within an outer hollow cylinder 310. The cylinder (cylindrical column) can be constructed from graphite, ceramic, high - temperature material, or high - melting - point material. Within the annular ring 340, a plurality of rods 330 are disposed between the outer hollow cylinder 310 and the solid inner cylinder 320. In one embodiment, the diameter of each of the plurality of rods 330 is substantially equal to the width of the annular ring 340. In other embodiments, the plurality of rods 330 can be disposed radially within the annular ring 340. The plurality of rods 330 are constructed from graphite or high - melting - point materials (such as tantalum or tungsten). The plurality of rods 330 can have a circular cross - section, but other shapes are possible as long as a gap is provided between the plurality of rods 330. The gaps between the plurality of rods 330 within the annular ring 340 provide a conduit for the molten dopant material to move towards the upper end of the wicking wire assembly 300. In one embodiment, the upper ends of the plurality of rods 330 terminate at the front end before the end of the outer hollow cylinder 310. Thereby, a wicking cavity is formed at the front end of the wicking wire assembly 300. Molten dopant material 125 can be collected into the wicking cavity. In certain embodiments, the solid inner cylinder 320 can extend beyond the outer hollow cylinder 310 at the front end. Thereby, the solid inner cylinder 320 extends into the arc chamber 100. This allows the solid inner cylinder 320 to be further heated and helps to melt the dopant material 125. In this embodiment, the wicking cavity can be ring - shaped. In some embodiments, the plurality of rods 330 and the solid inner cylinder 320 extend further downward than the outer hollow cylinder 310. By terminating the outer hollow cylinder 310 downwardly before the plurality of rods 330 and the solid inner cylinder 320, the surface area available for the molten dopant material 125 to enter the annular ring 340 is increased.The region where the outer hollow cylinder 310 is absent allows the plurality of rods 330 to be in direct contact with the dopant material. In that case, the dopant material is outside the wicking assembly 300. Thus, this region serves as an opening that allows the molten dopant material to enter the inner conduit.

[0052] In some embodiments, the plurality of rods 330 can be tantalum wires. During operation, the dopant material 125 melts, enters the gaps between the plurality of rods 330, moves between the plurality of rods 330 within the annular ring 340, and reaches the cavity. The cavity communicates with the arc chamber 100. The plurality of rods 330 can have a diameter between 0.005 and 0.125 inches. The annular ring 340 can have a width between 0.125 and 0.750 inches. In some embodiments, between 3 and 100 rods 330 can be disposed within the annular ring 340. The plurality of rods 330 can be of the same length or the lengths can vary. The length can be between 0.5 and 2.0 inches.

[0053] The direction shown in FIG. 5A is appropriate for the ion source shown in FIG. 1. In that case, the crucible 120 is maintained in an upright or vertical position. As described above, the crucible 120 can include a crucible cavity 121 on the front face of the crucible 120. The plurality of rods 330 can extend over the entire length or most of the length to the lower part of the crucible 120 so that the plurality of rods 330 remain in contact even as the dopant material is consumed.

[0054] The direction shown in FIG. 5B is appropriate for the ion source shown in FIGS. 2A-2B. In that case, the crucible 120 is maintained in a horizontal position. In this embodiment, the wicking wire assembly 300 is disposed within the crucible 120. Thereby, the lower portion of the wicking wire assembly 300 contacts the lowest wall of the crucible 120. Thus, the wicking wire assembly 300 can be disposed obliquely. This enables the molten dopant material to contact the plurality of rods 330 of the wicking wire assembly 300 even after a portion of the dopant material has been consumed.

[0055] Accordingly, in this embodiment, the gap within the annular ring 340 between the plurality of rods 330 acts as a conduit through which the molten dopant material can move. The width of the annular ring as well as the size and type of the plurality of rods determine the rate at which the molten dopant material moves to the front of the wicking wire assembly 300.

[0056] Figures 6A - 6F illustrate another embodiment of the wicking chip 170. In this embodiment, a foil 400 is wound to form a porous cylinder. When wound, the foil 400 includes a plurality of foil layers. The term "foil" is used to designate a sheet of material having a thickness between about 0.005 and 0.050 inches. The material used to form the "foil" or "foil layer" can be a high melting point material. The foil 400 can be a rectangular piece having a plurality of holes 410 as shown in FIG. 6A. The holes 410 allow the molten dopant material to move between adjacent layers within the foil 400. Alternatively, the foil 400 can have a rectangular piece having holes 410 and protrusions 420 as shown in FIG. 6B. The protrusions 420 tend to ensure a minimum separation or gap between adjacent layers when the foil is wound. In this way, the layers of the foil 400 can be further separated when the foil includes the protrusions 420. The protrusions 420 can be utilized with a metal foil that tends to be very smooth to introduce a minimum gap between the layers. In another embodiment, the foil 400 can have the protrusions 420 and may not have holes. The protrusions 420 extend outwardly from the foil 400 and can have a height that is 0.5 to 4.0 times the thickness of the foil 400. The protrusions 420 can be circular, or can be rectangular, triangular, or another shape. The holes 410 can be circular as shown in FIGS. 6A - 6C. However, in a plurality of other embodiments, the holes can be oval (including elliptical, the same hereinafter), hexagonal, square, or another shape.

[0057] Alternatively, one side of the foil 400 can be inclined as shown in FIG. 6C. When the foil of FIG. 6C is wound, starting with the smaller side, a cavity is formed at the front end of the foil 400. This enables the formation of a wicking cavity, similar to a plurality of other embodiments.

[0058] The foil 400 can be folded and wound in a plurality of different ways. In one embodiment shown in FIG. 6E, the foil 400 is wound in a spiral. When the foil is shaped as shown in FIG. 6C, a wicking cavity is formed. In another embodiment shown in FIG. 6D, the foil 400 is folded as a triangle. In this embodiment, a solid cylinder 450 can be disposed inside the triangular foil to control the size of the conduit. The solid cylinder 450 can terminate above, up to, or in front of the upper surface of the foil 400. When the solid cylinder 450 terminates in front of the foil, a cavity is formed in the upper part inside the foil 400. In that case, the gaps between the layers of the foil all flow into the cavity. In another embodiment shown in FIG. 6F, the foil 400 is folded as a hexagon. In this embodiment, a solid cylinder 450 can be disposed inside the hexagonal foil to control the size of the conduit. Of course, the foil 400 can be folded into any desired shape, including square, pentagon, hexagon, octagon, and oval. In all of these embodiments, the molten dopant material moves within the gaps between adjacent layers of the foil 400. The holes 410 in the foil 400 allow the molten material to move from between one set of layers to between another set of layers. Thereby, a more uniform flow through each of the gaps can be achieved.

[0059] The gaps between adjacent layers of the foil act as conduits. The gaps between adjacent layers of the foil, as well as the surface roughness of the foil, can determine the rate at which the molten dopant material moves to the front of the foil 400. Further, the holes 410 act as openings that allow the molten dopant material to enter the internal conduit.

[0060] A wound foil, such as that shown in FIGS. 6D - 6F, can be inserted into the crucible 120. In another embodiment, a hollow outer cylinder and a solid inner cylinder can be used to form an annular ring. A wound foil such as that shown in FIGS. 6D - 6F can be disposed within this annular ring. The combination of the hollow outer cylinder, the solid inner cylinder, and the wound foil creates a wicking tip. In another embodiment, holding the wound foil can be done by clamping a ring or tube around the shape, whether the shape is cylindrical, triangular, hexagonal, or another shape. The ring or tube is mechanically compressed around the wound foil. In another embodiment, the ring or tube may similarly be abeam tacked. The shape can be an organic shape or a geometric shape as long as there is a back - to - front passage.

[0061] In each of the plurality of embodiments shown in FIGS. 3 - 6, the wicking tip 170 includes a body having one or more internal conduits through which a molten dopant material can flow. In one embodiment shown in FIGS. 3A - 3E, this internal conduit is the plurality of conduits 220. In one embodiment shown in FIGS. 5A - 5C, this internal conduit is the gap between the plurality of rods 330 within the annular ring 340. In one embodiment shown in FIGS. 6A - 6F, this internal conduit is the gap between adjacent layers of the wound foil. Further, in each embodiment, there are one or more openings that allow the internal conduit to communicate with the exterior of the wicking tip. Finally, each embodiment also includes a wicking cavity that is used to collect the molten dopant material flowing through the internal conduit. Additionally, the wicking tip 170 is disposed within the crucible in each of these embodiments. This crucible can have a crucible cavity on its front surface to collect the molten dopant material that has flowed out of the wicking cavity.

[0062] The plurality of embodiments described above in this application can have many advantages.

[0063] First, the use of the wicking tip described herein allows the molten dopant material to move across the front of the crucible at a controlled rate. This rate is determined based on the size of the conduits within the wicking tip that lead to the wicking cavity. Additionally, the size and number of openings that connect the conduits to the exterior of the wicking tip 170 also contribute to the flow rate.

[0064] Next, the configuration of the wicking tip in FIGS. 3A - 3E includes choke points. There are a plurality of conduits 220 that communicate with the wicking cavity 230. In some embodiments, the cross-sectional area of the passage where the conduits 220 merge into the wicking cavity 230 is smaller than the total cross-sectional area of the conduits 220. As best seen in FIG. 3D, the cross-sectional area of the passage is significantly smaller than the combined area of the three conduits 220. This forms a choke point that restricts the flow of dopant material into the wicking cavity 230. In some embodiments, the total cross-sectional area of the conduits 220 is 1 to 12 times larger than the cross-sectional area of the passage connecting the conduits 220 to the wicking cavity 230. In some embodiments, the total cross-sectional area of the conduits 220 is 3 to 12 times larger than the cross-sectional area of the passage connecting the conduits 220 to the wicking cavity 230.

[0065] Thirdly, these wicking tips allow the crucible to be oriented in a vertical or horizontal configuration. Since the flow rate is controlled, there is little risk of the molten dopant material spilling into the arc chamber 100.

[0066] Furthermore, the wicking chip includes a wicking cavity. The wicking cavity is a location that provides a greater amount of surface area inside the arc chamber for use as a dopant material supplied to that point (inside the arc chamber) by heat. This greater amount of surface area can be in the form of recesses, protrusions, counterbores, single or multi-ports, and any geometric or organic shape having depth and shape. These shapes are used to supply an amount of dopant material that can be used, and this dopant material is then vaporized. The cavity can also hold the dopant material, thereby preventing the dopant material from dripping or spilling into the arc chamber.

[0067] The present disclosure is not limited in scope by the specific embodiments described herein. Indeed, in addition to what has been described herein, various other embodiments and modifications of the present disclosure will be apparent to those of ordinary skill in the art from the foregoing description and the accompanying drawings. Accordingly, such other embodiments and modifications are intended to be within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of particular embodiments for a particular purpose in a particular environment, those of ordinary skill in the art will recognize that its usefulness is not limited thereto, and that the present disclosure can be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below are to be construed in view of the broadest scope and spirit of the present disclosure described herein.

Claims

1. An apparatus for holding a dopant material within an ion source, comprising a crucible, and a wicking tip disposed within the crucible, the wicking tip comprising a body having one or more internal conduits, one or more openings enabling the one or more internal conduits to communicate between an exterior of the body and an interior of the crucible, and a wicking cavity disposed at a front end of the wicking tip, the one or more internal conduits merging into the wicking cavity.

2. The apparatus of claim 1, wherein the body comprises a cylindrical portion including a plurality of internal conduits.

3. A transport ring having a defined primary outer diameter is disposed in another part of the body to form the one or more openings, such that a portion of the body has the defined primary outer diameter and a region having a diameter smaller than the primary outer diameter, within which the plurality of internal conduits are completely enclosed. The apparatus of claim 2.

4. The apparatus of claim 2, wherein a cross-sectional area of a passage through which the plurality of internal conduits connect to the wicking cavity is smaller than a total cross-sectional area of the plurality of internal conduits so as to form a choke point.

5. The apparatus of claim 4, wherein the total cross-sectional area of the plurality of internal conduits is 3 to 12 times larger than the cross-sectional area of the passage through which the plurality of internal conduits connect to the wicking cavity.

6. The apparatus of claim 3, wherein the body and the one or more internal conduits are curved.

7. The apparatus of claim 2, wherein the wicking cavity includes a concave cavity.

8. The apparatus of claim 1, wherein the body includes exactly one internal conduit.

9. The body comprises a hollow outer cylinder and a solid inner cylinder, an annular ring is formed between the hollow outer cylinder and the solid inner cylinder, the wicking tip further comprises a plurality of rods disposed within the annular ring, and a gap between the plurality of rods within the annular ring includes the one or more internal conduits. The apparatus of claim 1.

10. The body comprises a foil wound to form the body, and a gap between adjacent layers of the foil includes the one or more internal conduits. The apparatus of claim 1.

11. An indirectly heated cathode ion source, comprising an arc chamber having a first end and a second end, A cathode disposed at the first end, and An indirectly heated cathode ion source comprising the device according to claim 1 disposed at the second end.

12. An indirectly heated cathode ion source, An arc chamber having a first end, a second end, and a side wall connecting the first end and the second end, A cathode disposed at the first end, An actuator extending into the arc chamber and configured to retract from the arc chamber, and An indirectly heated cathode ion source comprising the device according to claim 1 disposed at one end of the actuator.

13. A device for holding a dopant material within an ion source, A crucible, and A wicking tip disposed within the crucible, the wicking tip comprising A solid inner cylinder disposed within a hollow outer cylinder to form an annular ring, and A plurality of rods disposed within the annular ring.

14. The device according to claim 13, wherein a gap between the plurality of rods forms an internal conduit through which the dopant material moves.

15. The device according to claim 14, wherein the plurality of rods extend beyond the hollow outer cylinder at a rear end of the wicking tip so as to provide an opening for enabling the dopant material to enter the internal conduit.

16. A cavity, wherein the hollow outer cylinder extends further forward than the plurality of rods to form a cavity into which the dopant material collects from the internal conduit.

17. The device according to claim 13, wherein the plurality of rods comprise tantalum, a high melting point metal, or a high temperature wire.

18. An indirectly heated cathode ion source, An arc chamber having a first end and a second end, A cathode disposed at the first end, and An indirectly heated cathode ion source comprising the device according to claim 13 disposed at the second end.

19. An indirectly heated cathode ion source, An arc chamber having a first end, a second end, and a side wall connecting the first end and the second end, A cathode disposed at the first end, An actuator extending into the arc chamber and configured to retract from the arc chamber, and An indirectly heated cathode ion source comprising the device according to claim 13 disposed at one end of the actuator.

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