Indirectly heated cathode ion source and target support

Abstract

The present invention discloses an ion source with a pluggable target holder, which is used to accommodate solid doping materials. Specifically, an indirectly heated cathode ion source and a target holder are disclosed. The pluggable target holder includes a hollow interior, and the solid doping material is arranged in the hollow interior. The target holder has a porous surface at a first end, and vapor from the solid doping material can pass through the porous surface into the arc chamber. The porous surface prevents liquid or molten doping material from passing into the arc chamber. The target holder is also configured so that the target holder can be refilled with doping material when the doping material in the hollow interior has been consumed. The porous surface can be a part of a perforated crucible, a part of a perforated retaining cap, or a porous insert.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an ion source and a target holder, and more specifically to a target holder for accommodating solid-state doping materials, and more particularly to an indirectly heated cathode ion source and a target holder. Background Art

[0002] 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 to 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.

[0003] An extraction orifice is provided along one of the sides, close to the center of the arc chamber, through which ions formed in the arc chamber can be extracted.

[0004] In certain embodiments, it may be desirable to utilize materials in solid form as doping species. However, there are problems associated with using solid doping materials for an indirectly heated cathode ion source. For example, in the high temperature environment of an indirectly heated cathode ion source, metal sputtering targets tend to melt, drip, and generally degrade and damage the arc chamber as liquid metal flows and collects in the arc chamber. Therefore, ceramics containing dopants of interest are commonly used as solid doping materials because ceramics have higher melting temperatures. However, these ceramic materials generally produce less beam current for the dopant of interest. If the metal sputtering target can maintain its shape when melted without dripping or deforming, a significant increase in dopant beam current can be achieved.

[0005] Therefore, a target holder that can be used with solid dopant materials having a low melting temperature (e.g., certain metals) would be beneficial. Furthermore, it would be advantageous if the ion source was not contaminated by the solid dopant material. Additionally, it would be advantageous if the arc chamber could be used to perform other processes without using solid materials. Summary of the invention

[0006] The present invention discloses an ion source having a pluggable target holder for accommodating a solid dopant material. The pluggable target holder includes a hollow interior into which the solid dopant material is disposed. The target holder has a porous surface at a first end through which vapor from the solid dopant material can pass into an arc chamber. The porous surface prevents liquid or molten dopant material from passing into the arc chamber. The target holder is also configured so that the target holder can be refilled with dopant material when the dopant material within the hollow interior has been consumed. The porous surface can be a portion of a perforated crucible, a portion of a perforated retaining cap, or a porous insert.

[0007] According to one embodiment, an indirectly heated cathode ion source is disclosed. The ion source includes: an arc chamber including a plurality of walls; an indirectly heated cathode disposed in the arc chamber; and a target holder for accommodating a solid dopant, wherein the target holder includes: a crucible having a hollow interior suitable for accommodating the solid dopant, a first end, and a second end, wherein the first end includes a porous surface so that vapor from the solid doping material can pass from the hollow interior through the porous surface to the arc chamber. In some embodiments, the second end is closed. In certain other embodiments, the inner surface of the crucible is inclined toward the first end so that the inner diameter adjacent to the first end is greater than the inner diameter adjacent to the second end. In certain other embodiments, the ion source also includes a porous insert and a retaining cap, the retaining cap being disposed near the first end and attached to the crucible to retain the porous insert within the hollow interior, wherein the retaining cap includes an open face and the porous insert serves as the porous surface. In certain other embodiments, the ion source further comprises a perforated retaining cap disposed proximate the first end, wherein the perforated retaining cap is attached to the crucible and serves as the porous surface. In certain embodiments, the ion source comprises a hole and an end plug, wherein the hole is located at the second end, and the end plug is inserted into the hole located at the second end. In certain other embodiments, the hole is a tapped hole and the outer surface of the end plug is threaded so that the end plug is screwed into the second end. In certain other embodiments, the ion source further comprises a porous insert disposed in the hollow interior, wherein a flange is disposed at the first end and protrudes toward the central axis of the crucible so that the flange retains the porous insert in the hollow interior of the crucible and the porous insert serves as the porous surface. In certain other embodiments, the first end comprises a closed face, wherein the closed face comprises a plurality of openings, wherein the closed face serves as the porous surface. In some embodiments, the ion source further comprises: an actuator for moving the target holder into and out of the arc chamber; a target base attached to the actuator, wherein an outer surface of the target base is threaded; and a retaining fastener screwed onto the target base, wherein the retaining fastener holds the crucible against the target base.

[0008] According to another embodiment, a target holder for use with an ion source is disclosed. The target holder includes: a crucible formed as a cylinder having a hollow interior, a first end, and a second end, wherein the first end includes a porous surface and the second end includes a screw hole, and wherein a solid doping material is configured to be disposed in the hollow interior, wherein vapor from the solid doping material can pass from the hollow interior through the porous surface; and an end plug threaded on an outer surface to be screwed into the screw hole. In certain embodiments, the target holder includes a porous insert disposed in the hollow interior, and wherein the first end of the crucible includes a flange protruding toward a central axis of the cylinder, wherein the flange holds the porous insert and defines an opening at the first end, and the porous insert serves as the porous surface. In certain embodiments, the outer diameter of the porous insert is greater than the inner diameter of the opening. In other embodiments, the first end includes a closed face having a plurality of openings, wherein the closed face serves as the porous surface.

[0009] According to another embodiment, a target holder for use with an ion source is disclosed. The target holder includes: a crucible formed as a cylinder having a hollow interior, a first end, and a second end, wherein the second end is closed, and wherein a solid doping material is configured to be disposed in the hollow interior, and wherein a porous surface is disposed proximate the first end, wherein vapor from the solid doping material can pass through the porous surface from the hollow interior; and a retaining cap disposed proximate the first end. In certain embodiments, an outer surface of the crucible is threaded proximate the first end, and the retaining cap is screwed onto the first end of the crucible. In certain embodiments, the target holder includes a porous insert disposed in the hollow interior, and wherein the retaining cap includes an open face and a flange, wherein the flange protrudes toward a central axis of the crucible at a front edge of the retaining cap to form an opening, wherein an inner diameter of the opening of the retaining cap is smaller than an outer diameter of the porous insert to retain the porous insert. In some embodiments, the retaining cap comprises a closed face having a plurality of openings, wherein the closed face serves as the porous surface. In some embodiments, the inner surface of the crucible is inclined toward the first end so that the inner diameter of the hollow interior adjacent the second end is smaller than the inner diameter of the hollow interior adjacent the first end. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0011] Figure 1 is an indirectly heated cathode (IHC) ion source with a pluggable target holder according to one embodiment.

[0012] Figure 2 The pluggable target holder is retracted Figure 1 An indirectly heated cathode ion source is shown.

[0013] Figure 3 A target holder according to one embodiment is shown.

[0014] Figure 4 A target holder according to another embodiment is shown.

[0015] Figure 5 A target holder according to a third embodiment is shown.

[0016] Figure 6 A target holder according to a fourth embodiment is shown.

[0017] Figure 7 Show Figure 5 to Figure 6 Two possible configurations of the openings of the target holder are shown. DETAILED DESCRIPTION

[0018] As described above, a solid doping material having a low melting point tends to become liquid and drip, and deteriorates the arc chamber as the liquid flows and collects in the arc chamber.

[0019] Figure 1 An indirect heated cathode ion source 10 with a target holder is shown, which can overcome these problems. The indirect heated cathode 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 connected to 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 to accelerate the thermionic electrons from the filament 160 toward the cathode 110 and heat the cathode 110 when the thermionic electrons strike the rear surface of the cathode 110. The cathode bias power supply 115 may bias the filament 160 so that the filament 160 has a voltage, for example, between 200V and 1500V negative of the voltage of the cathode 110. The cathode 110 then emits thermionic electrons into the arc chamber 100 on its front surface.

[0020] 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 more negative value than the cathode 110 so that electrons are attracted 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.

[0021] 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.

[0022] The cathode 110 and the repeller 120 are each made of a conductive material (eg, metal or graphite).

[0023] 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.

[0024] An extraction aperture 140 may be provided on one side of the arc chamber 100 (referred to as the extraction plate 103). Figure 1 In FIG. 1 , the extraction orifice 140 is arranged on one side parallel to the YZ plane (perpendicular to the page). In addition, the indirect-heated cathode ion source 10 also comprises a gas inlet 106 through which the gas to be ionized can be introduced into the arc chamber 100 .

[0025] In some embodiments, the first electrode and the second electrode can be disposed on respective opposing walls 101 of the arc chamber 100 such that the first electrode and the second electrode are located within the arc chamber 100 on a wall adjacent to the extractor plate 103. The first electrode and the second electrode can each be biased by a respective power supply. In some embodiments, the first electrode and the second electrode can be in communication with a common power supply. However, in other embodiments, to maximize the flexibility and ability to tune the output of the indirect-heated cathode ion source 10, the first electrode can be in communication with a first electrode power supply and the second electrode can be in communication with a second electrode power supply.

[0026] 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 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 contain instructions and other data that enable the controller 180 to perform the functions described herein.

[0027] The indirect-heated cathode ion source 10 also includes a target holder 190 that can be inserted into and retracted from the arc chamber 100. Figure 1 In some embodiments, the target holder 190 enters the arc chamber along one of the walls 101 of the arc chamber 100. In some embodiments, the target holder 190 may enter the arc chamber 100 at a mid-plane between the first end 104 and the second end 105. In another embodiment, the target holder 190 may enter the arc chamber 100 at a location different from the mid-plane. Figure 1 In the embodiment shown in , the target holder 190 enters the arc chamber 100 through the side opposite the extraction aperture 140. However, in other embodiments, the target holder 190 may enter through the side adjacent to the extractor plate 103.

[0028] The target holder 190 has a hollow interior 191 into which a doping material 195 may be disposed. The hollow interior 191 may be defined as the interior of a hollow cylindrical crucible.

[0029] A doping material 195 (e.g., indium, aluminum, antimony, or gallium) may be disposed within the hollow interior 191 of the target holder 190. The doping material 195 may be in a solid form when placed within the hollow interior 191. The doping material 195 may be in the form of blocks of material, filings, shavings, balls, or other shapes. In certain embodiments, the doping material 195 may be melted and become a liquid.

[0030] During operation, the filament power supply 165 passes an electric current through the filament 160, which causes the filament 160 to emit thermionic electrons. These electrons strike the rear surface of the cathode 110, which may have a more positive value than the filament 160, causing the cathode 110 to heat, which in turn causes the cathode 110 to emit electrons into the arc chamber 100. These electrons collide with molecules of the gas fed into the arc chamber 100 through the gas inlet 106. A carrier gas (e.g., argon) or an etching gas (e.g., fluorine) may be introduced into the arc chamber 100 through the gas inlet 106 located at a suitable location. The combination of the electrons from the cathode 110, the gas, and the positive potential forms a plasma. In certain embodiments, the electrons and positive ions may be slightly confined by a magnetic field. In certain embodiments, the plasma is confined near the center of the arc chamber 100, near the extraction orifice 140. Chemical etching, elevated temperatures, or sputtering by the plasma transforms the doping material 195 into a gas phase and achieves ionization. The ionized feedstock material may then be extracted through extraction orifice 140 and used to prepare an ion beam.

[0031] Because the plasma is maintained at a more positive voltage than the target holder 190, vapor, negative ions, and neutral atoms sputtered or otherwise released from the dopant material 195 are attracted toward the plasma.

[0032] In some embodiments, due to the heat of the plasma formation, the doping material 195 is heated and vaporized. However, in other embodiments, the doping material 195 can also be heated by additional means. For example, a heating element can be provided in the target holder 190 to further heat the doping material 195. The heating element can be a resistive heating element or some other type of heater.

[0033] In some embodiments, the target holder 190 can be made of a conductive material and can be grounded. In different embodiments, the target holder 190 can be made of a conductive material and can be electrically floating. In different embodiments, the target holder 190 can be made of a conductive material and can be maintained at the same voltage as the wall 101 or the actuator 200. In other embodiments, the target holder 190 can be made of an insulating material.

[0034] In yet another embodiment, the target holder 190 may be electrically biased relative to the arc chamber 100. For example, the target holder 190 may be made of a conductive material and may be biased by an independent power source (not shown) to be at a different voltage than the wall 101. This voltage may have a more positive value or a more negative value than the voltage applied to the wall 101. As such, the electrical bias may be used to sputter the dopant material 195 or as an additional means of heating the dopant material.

[0035] The target holder 190 is in communication with one end of the actuator 200. The opposite end of the actuator 200 may be in communication with a support 210. In some embodiments, this support 210 may be the housing of the indirectly heated cathode ion source 10. In some embodiments, the actuator 200 may be capable of varying its total displacement. For example, the actuator 200 may be a telescopic design.

[0036] Figure 2 The indirectly heated cathode ion source 10 is shown with the actuator 200 in the retracted position. In this position, the hollow interior 191 is completely outside the arc chamber 100. In certain embodiments, the dopant material 195 cools when the target holder 190 is outside the arc chamber 100. As such, the dopant material 195 does not enter the arc chamber when the actuator 200 is in the retracted position.

[0037] Although Figure 1 The hollow interior 191 is shown completely within the arc chamber 100 and Figure 2 The hollow interior 191 is shown completely outside of the arc chamber 100, but other locations are possible. By controlling the distance the target holder 190 is inserted into the arc chamber 100, the temperature of the target holder 190 and the temperature of the dopant material 195 can be controlled.

[0038] These factors can determine the amount of dopant beam current obtained by the dopant material 195. In addition, if the target holder 190 is fully retracted, the dopant beam current can be reduced to zero. This enables the use of other dopant species in the indirect heated cathode ion source 10 without any risk of cross contamination. In other words, when the actuator 200 is retracted, different dopant species can be introduced through the gas inlet 106 and ionized without contamination by the dopant material 195 disposed in the hollow interior 191.

[0039] In some embodiments, the target holder 190 may not be inserted into the arc chamber 100, but rather positioned close enough so that the dopant material 195 is heated and vapor enters the arc chamber 100. For example, the target holder 190 may be made of a material having a high thermal conductivity. As such, if the target holder 190 is close to the arc chamber 100, the dopant material 195 may be heated and vapor enters the arc chamber 100. Figure 2 ), heat from the plasma can still be transferred to the doping material 195 and the vaporized doping material can enter the arc chamber 100.

[0040] In this embodiment, there may be a first retracted position in which the target holder 190 is still in thermal communication with the arc chamber 100 and the dopant material 195 is vaporized. There may also be a second retracted position in which the target holder 190 is moved away from the arc chamber 100 so that the dopant material 195 is not vaporized. In this second retracted position, different dopants may be introduced into the arc chamber without the risk of cross contamination.

[0041] In other words, in certain embodiments, target holder 190 can be disposed in at least three different positions: a first position, in which at least a portion of hollow interior 191 is disposed within arc chamber 100; a second position, in which hollow interior 191 is disposed outside arc chamber 100; and a third position, in which hollow interior 191 is disposed outside arc chamber 100 but is still thermally connected to arc chamber 100 to allow dopant material 195 to be vaporized.

[0042] Figure 3 One embodiment of the target holder 190 is shown in more detail. In this embodiment, the target holder 190 includes a crucible 300. The crucible 300 can be a hollow cylinder having an open face on a first end 301 and a hole 303 on a second end 302. The open face at the first end 301 can have a flange 304 that extends toward a central axis 305 of the cylinder. Thus, the opening 306 on the first end 301 can be smaller than the inner diameter of the hollow cylinder due to the flange 304. The diameter of the opening 306 can also be smaller than the diameter of the hole 303 on the second end 302. The crucible 300 can be constructed of graphite, a refractory material, alumina, carbide, or another suitable material.

[0043] A porous insert 310, which may be in the shape of a disk, is inserted into the interior of the crucible 300 through a hole 303 on the second end 302. The outer diameter of the porous insert 310 may be approximately the same as the inner diameter of the crucible 300 and larger than the diameter of the opening 306. In certain embodiments, the inner diameter of the crucible 300 may be slightly smaller than the outer diameter of the porous insert 310 to form an interference fit. In some embodiments, the outer diameter of the porous insert 310 may be 0.1 inches larger than the diameter of the opening 306. Thus, once the porous insert 310 is inserted, the porous insert 310 is held in place by the flange 304 so that the porous insert 310 cannot be removed or dropped through the opening 306. The porous insert 310 may be graphite foam, graphite or refractory mesh, silicon carbide, alumina foam, or another suitable material. The pore size and porosity may be selected to allow vapor to pass through while blocking liquid from flowing through the porous insert 310. It has been found that liquid metals, such as liquid aluminum, have extremely high surface tension. Thus, while vapor from the molten aluminum is able to pass through the porous insert 310, liquid material is unable to pass through the porous insert 310 due to surface tension.

[0044] An end plug 320 is mounted on the second end 302 of the crucible 300. In some embodiments, the hole 303 may be a screw hole and the end plug 320 may be threaded so that the end plug 320 is screwed into the second end 302 of the crucible 300. The end plug 320 may be constructed of graphite or another suitable material. The end plug 320 is used to prevent liquid material from leaving through the hole 303 and to enable the crucible 300 to be refilled.

[0045] The target holder 190 may also include a target base 330. The target base 330 may be attached to the actuator 200. The target base 330 is attached to the crucible by a retaining fastener 340. For example, in one embodiment, a portion of the end plug 320 has a larger diameter than the outer diameter of the crucible 300. As such, when the end plug 320 is screwed into the second end 302 of the crucible, a portion of the end plug 320 extends outward from the central axis further than the crucible 300, thereby forming a protrusion 321.

[0046] In another embodiment, the crucible 300 has a protrusion along the outer diameter of the crucible 300 proximate the second end 302 .

[0047] The crucible 300 may be fixed to the target base 330 using a retaining fastener 340. The retaining fastener 340 may be ring-shaped and threaded on its inner surface. In addition, the retaining fastener 340 has a flange 341 having a smaller diameter than the protrusion 321. Therefore, the retaining fastener 340 may then be installed over the first end 301 of the crucible 300. The retaining fastener 340 may be screwed onto the target base 330, which may be threaded on its outer surface. The retaining fastener 340 is continued to be rotated until the flange 341 contacts the protrusion 321. This pressure attaches the crucible 300 to the target base 330.

[0048] In this embodiment, the doping material 195 may be inserted into the target holder 190 as follows. First, the porous insert 310 is inserted into the hole 303 in the second end 302 of the crucible 300. The porous insert 310 is moved through the interior of the crucible 300 so that the porous insert 310 is pressed against the flange 304. Next, the doping material 195 may be disposed in the crucible 300 through the hole 303 in the second end 302. The presence of the porous insert 310 can retain the doping material 195 in the crucible and prevent the doping material 195 from passing through the opening 306. Once the doping material 195 has been added, the crucible 300 may be closed by screwing the end plug 320 into the second end 302. The crucible assembly including the crucible 300, the end plug 320, and the porous insert 310 is then positioned against the target base 330. The retaining fastener 340 is slid over the first end 301 of the crucible 300 and moved toward the second end 302, thus screwing the retaining fastener 340 onto the target base 330. The target holder 190 is now ready for use.

[0049] Thus, in this embodiment, a first end 301 of the crucible 300 includes an open face, wherein a porous insert 310 is disposed proximate the open face. This porous insert 310 serves as a porous surface that allows vapor to pass from the hollow interior to the arc chamber. A second end 302 includes a hole 303 so that an end plug 320 can be removably attached to the crucible 300. For example, the end plug 320 can be screwed into a screw hole at the second end 302. In this way, the solid dopant 195 can be refilled after the material within the target holder 190 has been consumed. In other words, the crucible 300 can be refilled by unscrewing the retaining fastener 340 to remove the crucible assembly from the target base 330. Once this is done, the end plug 320 can be unscrewed from the crucible 300. Additional doping material 195 can then be deposited in the crucible 300.

[0050] Figure 4 A target holder 190 according to another embodiment is shown. In this embodiment, the second end 302 of the crucible is closed so that only the first end 301 is open. The crucible 300 has a protrusion 309 near the second end 302. This protrusion 309 is used by a retaining fastener 340 to attach the crucible 300 to a target base 330. As described above, the retaining fastener 340 can be screwed onto the target base 330.

[0051] In this embodiment, a holding cap 350 is provided near the first end 301 of the crucible 300. The holding cap 350 is in the shape of a ring with an open face, and the holding cap 350 has a flange 351 on its front edge protruding toward the center of the ring. The inner surface of the holding cap 350 may be threaded. In addition, in this embodiment, the outer surface of the crucible 300 may also be threaded near the first end 301. In this way, the holding cap 350 can be screwed onto the first end 301 of the crucible 300.

[0052] The porous insert 310 is inserted through the opening in the first end 301. For example, the diameter of the porous insert 310 may be approximately the same size as the inner diameter of the crucible 300, but may be larger than the inner diameter of the open face of the retaining cap 350 adjacent the flange 351. In certain embodiments, the inner diameter of the crucible 300 may be slightly smaller than the outer diameter of the porous insert 310 to form an interference fit. In some embodiments, the outer diameter of the porous insert 310 may be 0.1 inches larger than the inner diameter of the open face.

[0053] 301 . Thus, in this embodiment, the first end 301 is both the location where the porous insert 310 is located and the location where solid doping material is added to the crucible 300. Specifically, in this embodiment, the doping material 195 can be inserted into the target holder 190 as follows. First, the doping material 195 can be deposited in the crucible 300 through the first end 301. Once the doping material 195 has been added, the crucible can be closed by positioning the porous insert 310 adjacent to the opening of the first end 301. Then, the retaining cap 350 is screwed onto the first end of the crucible 300, thereby holding the porous insert 310 in place. Then, the crucible assembly including the crucible 300, the retaining cap 350, and the porous insert 310 is positioned against the target base 330. The retaining fastener 340 is inserted over the first end 301 of the crucible 300 and slid toward the second end 302, thereby screwing the retaining fastener 340 onto the target base 330. The target holder 190 is now ready for use.

[0054] By using the retaining cap 350, the interior of the crucible can be accessed to refill with doping material 195 after the material within the target holder 190 has been consumed. In other words, the crucible 300 can be refilled by optionally unscrewing the retaining fasteners 340 to remove the crucible assembly from the target base 330. Once this is done, the retaining cap 350 can be unscrewed from the crucible 300. Additional doping material 195 can then be deposited in the crucible 300.

[0055] In addition, if Figure 4, the interior surface of the crucible 300 may be inclined or may be sloped so that the inner diameter of the crucible 300 adjacent the first end 301 is greater than the inner diameter adjacent the second end 302. This enables the doping material to flow toward the first end 301 of the crucible. This may be used to increase the temperature of the doping material to enhance the formation of vapor adjacent the porous insert 310.

[0056] Figure 3 and Figure 4 The embodiment of the present invention utilizes a porous insert 310 that allows vapor to pass but not liquid to pass. In other words, the porous insert 310 acts as a porous surface disposed on the first end of the crucible and separates the hollow interior of the crucible 300 from the arc chamber 100. Other ways of forming this porous surface may be used.

[0057] For example, Figure 5 The porous insert 310 is not used. Figure 3 A variation of the target holder 190 is shown. Instead, a perforated crucible 400 is used instead. Figure 3 The perforated crucible 400 may be a hollow cylinder having a closed face 405 on a first end 401 and a hole 403 on a second end 402. The closed face 405 may include a plurality of openings 410 extending through the closed face 405, thereby enabling the interior of the perforated crucible 400 to communicate with the outside of the perforated crucible 400. In other words, the closed face of the perforated crucible 400 acts as a porous surface. The size of the openings 410 may be selected so that the surface tension of the liquid dopant prevents the liquid from passing through the openings 410 but allows the vapor to pass through. The perforated crucible 400 may be constructed of graphite, a refractory material, alumina, carbide, or another suitable material.

[0058] The end plug 320, the target base 330 and the retaining fastener 340 are similar to those described above. Figure 3 The contents described are the same.

[0059] In this embodiment, the doping material 195 may be inserted into the target holder 190 as follows. First, the doping material 195 may be disposed in the perforated crucible 400 through the hole 403 in the second end 402. The closed face present at the first end 401 holds the doping material 195 in the perforated crucible 400. Once the doping material 195 has been added, the perforated crucible 400 may be closed by screwing the end plug 320 into the second end 402. The crucible assembly including the perforated crucible 400 and the end plug 320 is then positioned against the target base 330. The retaining fastener 340 is slid over the first end 401 of the perforated crucible 400 and moved toward the second end 402, screwing the retaining fastener 340 onto the target base 330. The target holder 190 is now ready for use.

[0060] Figure 6 The porous insert 310 is not used. Figure 4 A variation of the target holder 190 is shown. Instead, a perforated retaining cap 450 is used instead. Figure 4 Retaining cap 350.

[0061] In this embodiment, a perforated retaining cap 450 is disposed proximate to the first end 301 of the crucible 300. The perforated retaining cap 450 is a cylinder having a closed face. The closed face includes a plurality of openings 410. The inner surface of the cylindrical portion of the perforated retaining cap 450 may be threaded. Additionally, in this embodiment, the outer surface of the crucible 300 may also be threaded proximate to the first end 301. In this way, the perforated retaining cap 450 may be screwed onto the first end 301 of the crucible 300.

[0062] Thus, in this embodiment, the first end 301 is both the site where the porous surface is located and the site where the solid doping material is added to the crucible 300. Specifically, in this embodiment, the doping material 195 can be inserted into the target holder 190 as follows. First, the doping material 195 can be deposited in the crucible 300 through the first end 301. Once the doping material 195 has been added, the crucible can be closed by screwing the perforated retaining cap 450 onto the first end of the crucible 300. Then, the crucible assembly including the crucible 300 and the perforated retaining cap 450 is positioned against the target base 330. The retaining fastener 340 is inserted over the first end 301 of the crucible 300 and slid toward the second end 302, thus screwing the retaining fastener 340 onto the target base 330. The target holder 190 is now ready.

[0063] By using the perforated retaining cap 450, the interior of the crucible can be accessed to refill with doping material 195 after the material within the target holder 190 has been consumed. In other words, the crucible 300 can be refilled by optionally unscrewing the retaining fasteners 340 to remove the crucible assembly from the target base 330. Once this is done, the perforated retaining cap 450 can be unscrewed from the crucible 300. Additional doping material 195 can then be deposited in the crucible 300.

[0064] In addition, if Figure 6 As shown in , the interior surface of the crucible 300 may be inclined or may be sloped so that the inner diameter of the crucible 300 near the first end 301 is larger than the inner diameter near the second end 302. This enables the doping material to flow toward the first end 301 of the crucible. This can be used to increase the temperature of the doping material to enhance the formation of vapor near the perforated retaining cap 450.

[0065] The openings in the perforated retaining cap 450 and the openings in the perforated crucible 400 can be arranged in a variety of configurations. Figure 7Two such configurations are shown for openings 410. The present disclosure is not limited to these embodiments.

[0066] The above-described embodiments in the present application may have many advantages. The crucible is formed as a hollow cylinder and thus protects the doping material from directly facing the hot cathode. The target support also includes a porous surface that separates the interior of the crucible from the external environment. This porous surface enables vapor from the vaporized doping material to pass from the interior of the crucible to the arc chamber. However, due to the high surface tension of the molten doping material, the porous surface prevents the liquid dopant from passing into the arc chamber. In addition, in some embodiments, the interior surface of the crucible is inclined toward the porous surface to transport the liquid doping material toward the hotter end of the crucible like a funnel. This can enhance the vaporization of the doping material.

[0067] In addition, the crucible is designed to be reusable. In some embodiments, a threaded end plug is used to seal the second end of the crucible. The end plug can be removed to refill the crucible with doping material when desired. In other embodiments, the retaining cap can be removed to enable refilling with doping material. Thus, the target holder can be reused multiple times.

[0068] 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 may 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 disposed in the arc chamber; as well as A target support for accommodating a solid-state dopant, wherein the target support comprises: A crucible having a hollow interior suitable for containing the solid dopant, a first end and a second end, wherein the first end includes a porous surface to enable vapor from the solid dopant material to pass from the hollow interior through the porous surface to the arc chamber, wherein the solid dopant material can melt and become a liquid that does not pass through the porous surface.

2. An indirectly heated cathode ion source according to claim 1, wherein the second end is closed, and the indirectly heated cathode ion source also includes a porous insert and a retaining cap, wherein the retaining cap is arranged near the first end and is attached to the crucible to retain the porous insert in the hollow interior, wherein the retaining cap includes an open face and the porous insert is used as the porous surface.

3. An indirectly heated cathode ion source according to claim 1, wherein the second end is closed and the indirectly heated cathode ion source further comprises a perforated retaining cap disposed proximate to the first end, wherein the perforated retaining cap is attached to the crucible and serves as the porous surface.

4. The indirectly heated cathode ion source of claim 1, further comprising a hole and an end plug, wherein the hole is located at the second end and the end plug is inserted into the hole located at the second end.

5. The indirectly heated cathode ion source of claim 4, further comprising a porous insert disposed in the hollow interior, wherein a flange is disposed at the first end and protrudes toward the central axis of the crucible so that the flange holds the porous insert in the hollow interior of the crucible, and the porous insert serves as the porous surface.

6. The indirectly heated cathode ion source of claim 4, wherein the first end comprises a closed face comprising a plurality of openings, wherein the closed face serves as the porous surface.

7. The indirectly heated cathode ion source of claim 1, further comprising: an actuator to move the target holder into and out of the arc chamber; a target base attached to the actuator, wherein an outer surface of the target base is threaded; as well as A retaining fastener is threaded onto the target base, wherein the retaining fastener holds the crucible against the target base.

8. A target holder for use with an ion source, comprising: a crucible formed as a cylinder having a hollow interior, a first end and a second end, wherein the first end includes a porous surface and the second end includes a screw hole, and wherein a solid doping material is configured to be disposed in the hollow interior, wherein vapor from the solid state doping material is able to pass from the hollow interior through the porous surface; and An end plug is threaded on an outer surface to be screwed into the screw hole, wherein the solid doping material can be melted and become a liquid that does not pass through the porous surface.

9. The target holder of claim 8, further comprising a porous insert disposed in the hollow interior, and wherein the first end of the crucible comprises a flange protruding toward a central axis of the cylinder, wherein the flange holds the porous insert and defines an opening at the first end, and the porous insert serves as the porous surface.

10. The target holder of claim 8, wherein the first end comprises a closed face having a plurality of openings, wherein the closed face serves as the porous surface.

11. A target holder for use with an ion source, comprising: a crucible formed as a cylinder having a hollow interior, a first end and a second end, wherein the second end is closed, and wherein a solid doping material is configured to be disposed in the hollow interior, and wherein a porous surface is disposed proximate the first end, wherein vapor from the solid state doping material is able to pass from the hollow interior through the porous surface; and A retaining cap is disposed proximate the first end, wherein the solid doping material can be melted and become a liquid that does not pass through the porous surface.

12. The target holder of claim 11, wherein an outer surface of the crucible is threaded proximate the first end, and the retaining cap is screwed onto the first end of the crucible.

13. The target holder of claim 11 , further comprising a porous insert disposed in the hollow interior, and wherein the retaining cap comprises an open face and a flange, the flange protruding toward the central axis of the crucible at a front edge of the retaining cap to form an opening, wherein an inner diameter of the opening of the retaining cap is smaller than an outer diameter of the porous insert to retain the porous insert.

14. The target holder of claim 11, wherein the retaining cap comprises a closed face having a plurality of openings, wherein the closed face serves as the porous surface.

15. The target holder of claim 11, wherein an inner surface of the crucible slopes toward the first end such that an inner diameter of the hollow interior adjacent the second end is smaller than an inner diameter of the hollow interior adjacent the first end.

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