Indirect heating type cathode ion source and target seat

Abstract

The invention discloses an ion source for accommodating a target seat of a solid doping material, and particularly discloses an indirect heating type cathode ion source and a target seat. The ion source includes a thermocouple disposed proximate the target seat to monitor a temperature of the solid doping material. In some embodiments, a controller uses this temperature information to alter one or more parameters of the ion source, such as arc voltage, cathode bias voltage, extracted beam current, or the location of the target seat within the arc chamber. Various embodiments are shown that show a connection between a controller and a thermocouple. In addition, embodiments are also presented that show various placement of the thermocouple on the target seat.

Description

[0001] The present invention is a divisional application of the invention patent application with application number 202080070072.7 filed on September 15, 2020 and invention name “Indirectly Heated Cathode Ion Source and Target Holder”. Technical Field

[0002] The disclosed embodiments relate to an indirectly heated cathode ion source and target support, and more particularly to an ion source having a pluggable target support for receiving solid state dopant material, wherein the temperature of the dopant material or the target support can be measured and optionally controlled. Background Art

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

[0004] Along one of the sides, close to the center of the arc chamber, an extraction aperture is provided through which ions formed in the arc chamber can be extracted.

[0005] In certain embodiments, it may be desirable to utilize a material in solid form as a doping species. For example, a crucible or target holder may be used to contain the metal so that when the metal liquefies, the liquefied metal remains in the target holder. Using pure solid metal directly for ion implantation can increase the beam current available for wafer implantation.

[0006] However, there may be problems associated with using a target holder for solid state dopant materials. For example, when metals with low melting and low boiling temperatures are used in a carrier-type target holder, extremely high temperatures may become a problem. For example, the dopant material may become unstable and susceptible to runaway effects that may cause inconsistent beam performance and lead to undesirable accumulation of dopant material in the arc chamber.

[0007] Therefore, an ion source that can be used with solid-state dopant materials having low melting temperatures (eg, certain metals) and whose internal temperature can be monitored and controlled would be beneficial. Summary of the invention

[0008] An ion source having a target holder for housing a solid state dopant material is disclosed. The ion source includes a thermocouple disposed proximate the target holder to monitor the temperature of the solid state dopant material. In certain embodiments, a controller uses this temperature information to alter one or more parameters of the ion source, such as arc voltage, cathode bias voltage, extracted beam current, or the position of the target holder within the arc chamber. Various embodiments are shown that illustrate the connection between the controller and the thermocouple. In addition, embodiments are presented that illustrate various placements of the thermocouple on the target holder.

[0009] According to one embodiment, an indirectly heated cathode ion source is disclosed. The indirectly heated cathode ion source includes: an arc chamber including a plurality of walls connecting a first end and a second end; an indirectly heated cathode disposed on the first end of the arc chamber; a target holder having a capsule for containing a dopant material; a thermocouple in contact with the target holder; and a controller in communication with the thermocouple, wherein the controller changes a parameter of the ion source based on a temperature measured by the thermocouple. In some embodiments, the ion source also includes an actuator in communication with the target holder to move the target holder between a first position and a second position, and wherein the parameter includes a position of the target holder. In some embodiments, the parameter is selected from the group consisting of: an arc voltage, a filament current, a cathode bias voltage, a flow rate of a feedstock gas, and a beam extraction current. In some embodiments, the ion source also includes a heating element in communication with the target holder, and wherein the parameter includes a current supplied to the heating element. In some embodiments, the ion source further comprises an actuator assembly, the actuator assembly comprising: a wire for electrically connecting the thermocouple to the controller; a housing, comprising a rear housing, a front housing, and an outer housing connecting the rear housing and the front housing; a shaft, attached to the target holder and having a retaining plate disposed in the housing; a bellows, disposed in the housing and attached to the retaining plate at one end and to the rear housing at an opposite end; and an actuator for linearly translating the shaft. In some embodiments, a connector is mounted in the front housing, and the wire passes from the controller through a space between the outer housing and the bellows and terminates at the connector. In some other embodiments, a second connector is fitted to the connector, and a thermocouple wire is disposed between the second connector and the thermocouple. In some embodiments, the thermocouple wire is coiled to enable adjustment of the position of the target holder relative to the arc chamber. In some embodiments, the thermocouple wire is wrapped in an Inconel braid. In some embodiments, the thermocouple wire is wrapped in an alumina tube. In some embodiments, the wire passes through the hollow interior of the shaft. In some embodiments, the target holder includes a target base, a crucible plug, a crucible, and a porous plug. In some embodiments, the thermocouple is disposed on an outer surface of the crucible. In some embodiments, a cavity is disposed on an inner surface of the target holder, and the thermocouple is disposed in the cavity on an outer surface of the crucible plug. In some embodiments, a potting material is used to hold the thermocouple in place. In some embodiments, a set screw is used to hold the thermocouple in place. In some embodiments, a spring is disposed in the cavity to hold the thermocouple in place. In some embodiments, the ion source includes a heating element in communication with the target holder, wherein the heating element includes a resistive wire.In certain embodiments, the resistive wire is in communication with the crucible or the crucible plug.

[0010] According to another embodiment, an assembly for use with an ion source is disclosed. The assembly includes a connector; a thermocouple; and a wire disposed between the connector and the thermocouple. In some embodiments, the wire is coiled. In some embodiments, the wire is individually insulated. In some embodiments, the insulated wire is wrapped in an Inconel braid. In some embodiments, the insulated wire is wrapped in an alumina tube.

[0011] According to another embodiment, a target holder for containing doping material in an ion source is disclosed. The target holder includes: a target base; a crucible formed as a hollow cylinder; a crucible plug covering one open end of the crucible and disposed near the target base; a porous plug covering the opposite end of the crucible, wherein gaseous doping material can pass through the porous plug; and a thermocouple in communication with the target holder. In some embodiments, the thermocouple is disposed on the outer surface of the crucible. In other embodiments, the thermocouple is disposed in a channel in the wall of the crucible. In some embodiments, a cavity is disposed in the target base near the crucible plug, and the thermocouple is disposed in the cavity near the crucible plug. In some embodiments, a channel is disposed in the target base, wherein the channel is in communication with the cavity to enable a wire to be laid to the thermocouple. In some embodiments, a potting material is used to hold the thermocouple in place. In some embodiments, a set screw is used to hold the thermocouple in place. In some embodiments, the target holder includes a shaft affixed to the target base. In one embodiment, the interior of the shaft is hollow so that a wire can be routed through the hollow interior of the shaft to the thermocouple.

[0012] According to another embodiment, an indirectly heated cathode ion source is disclosed. The ion source includes: an arc chamber, including a plurality of walls connecting a first end and a second end; an indirectly heated cathode, disposed on the first end of the arc chamber; a target holder, having a capsule for accommodating a dopant material, wherein the target holder is movable within the arc chamber; and a controller, wherein the controller changes the position of the target holder within the arc chamber based on the temperature of the dopant material. In some embodiments, the temperature of the dopant material is determined using optical measurements, pyrometers, color points, thermocouples, wireless thermocouple readers, or resistance temperature detectors (RTDs). In certain embodiments, the temperature of the dopant material is determined using thermocouples. In some embodiments, the temperature of the dopant material is estimated based on the temperature of components within the arc chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] For a better understanding of the present disclosure, reference is made to the accompanying drawings, which are incorporated herein by reference and in which:

[0014] Figure 1 An indirectly heated cathode (IHC) ion source with a pluggable target holder is provided according to one embodiment.

[0015] Figure 2 An actuator assembly and a target mount are shown according to one embodiment.

[0016] Figure 3 An actuator assembly and a target seat according to a second embodiment are shown.

[0017] Figure 4 An actuator assembly and a target seat according to a third embodiment are shown.

[0018] Figure 5 The placement of thermocouples on a target support is shown according to one embodiment.

[0019] Figure 6 The placement of a thermocouple on a target support is shown according to a second embodiment.

[0020] Figure 7 The placement of a thermocouple on a target support is shown according to another embodiment.

[0021] FIG. 8A to FIG. 8B The placement of thermocouples on a target support is shown according to other embodiments.

[0022] FIG. 9A to FIG. 9C The placement of thermocouples on a target support is shown according to other embodiments.

[0023] Fig.10 An actuator assembly and target backing are shown according to one embodiment in which a resistive wire is used to heat the target backing. DETAILED DESCRIPTION

[0024] As described above, at very high temperatures, the solid dopant in the ion source may melt too quickly and form undesirable dopant accumulation in the arc chamber. At low temperatures, the solid dopant may not melt at all.

[0025] Figure 1An IHC ion source 10 with a target holder is shown that overcomes these problems. The IHC ion source 10 includes an arc chamber 100, which includes two opposite ends and walls 101 connected to the two ends. The walls 101 of the arc chamber 100 can be constructed of a conductive material and can be electrically connected to each other. In some embodiments, a liner can be provided near one or more of the walls 101. A cathode 110 is provided in the arc chamber 100 at a first end 104 of the arc chamber 100. A filament 160 is provided behind the cathode 110. The filament 160 is in communication with a filament power supply 165. The filament power supply 165 is configured to pass an electric current through the filament 160 so that the filament 160 emits hot ion electrons. The cathode bias power supply 115 biases the filament 160 negatively relative to the cathode 110 so that the thermionic electrons are accelerated 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 voltage difference between the cathode 110 and the filament 160 may be referred to as the cathode bias voltage. The cathode 110 then emits thermionic electrons on its front surface into the arc chamber 100.

[0026] 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, thereby attracting electrons from the filament 160 toward the cathode 110. In some embodiments, the cathode 110 can be biased relative to the arc chamber 100, for example, by the bias power supply 111. The voltage difference between the arc chamber 100 and the cathode 110 can be referred to as the arc voltage. In other embodiments, the cathode 110 can 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 can 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.

[0027] 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.

[0028] The cathode 110 and the repeller 120 are each made of a conductive material (eg, metal or graphite).

[0029] In certain embodiments, a magnetic field is generated in the arc chamber 100. This magnetic field is intended to confine electrons in one direction. The magnetic field 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 do not experience any electromagnetic forces to move in the Y direction. However, the movement of electrons in other directions may experience electromagnetic forces.

[0030] An extraction aperture 140 may be provided on one side of the arc chamber 100, which is referred to as an 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). Furthermore, the IHC ion source 10 also comprises a gas inlet 106 through which a gas to be ionized can be introduced into the arc chamber 100 .

[0031] 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 flexibility and enable tuning of the output of the IHC 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.

[0032] 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.

[0033] The IHC ion source 10 further includes a target holder 190 that can be inserted into and removed 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 1In 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 extraction plate 103. The target holder 190 is movable between a first position and a second position.

[0034] The target holder 190 has a cavity or capsule 191 into which a doping material 195 can be disposed. The capsule 191 can have a bottom surface and sidewalls extending upward from the bottom surface. In some embodiments, the sidewalls can be vertical. In other embodiments, the sidewalls can be inclined outward from the bottom surface. In some embodiments, the sidewalls and the bottom surface meet at a rounded edge. The bottom surface and the sidewalls form a cavity that is closed at the bottom. In other words, much like a conventional cup, the doping material 195 is inserted or removed through the open top, while the sidewalls and the bottom surface form a sealed structure from which the doping material 195 cannot exit. In another embodiment, the capsule 191 can be enclosed so that the doping material 195 is disposed within the capsule 191. For example, a hollow cylindrical crucible can be used to form the capsule 191. A porous plug 192 can be used to keep the doping material within the capsule 191 and allow vapor to exit the capsule 191. For example, the porous plug 192 can be graphite foam. The feed rate of dopant material from the target backing 190 may also be controlled by adding patterned holes of various sizes to the porous plug 192 or any other wall of the target backing 190. Any of the walls of the target backing 190 may be a porous material and used to control the feed of dopant material into the arc chamber 100.

[0035] A doping material 195, such as indium, aluminum, antimony, or gallium, may be disposed within a capsule 191 of the target holder 190. The doping material 195 may be in a solid form when placed within the capsule 191. The doping material 195 may be in the form of a block of material, filings, shavings, spheres, or in other shapes. In certain embodiments, the doping material 195 may melt and become a liquid. Thus, in certain embodiments, the target holder 190 is configured to enter the arc chamber 100 such that the open end faces upward and the sealed bottom faces downward such that the molten doping material 195 cannot flow from the target holder 190 into the arc chamber 100, but rather remains within the target holder 190. In other words, the IHC ion source 10 and the target holder 190 are oriented such that the doping material 195 is held within the capsule 191 by gravity.

[0036] A thermocouple 198 may be proximate to the target holder 190 or the dopant material 195. This thermocouple 198 may be in communication with the controller 180. The thermocouple 198 may include one or more wires 199 that electrically connect the thermocouple 198 to the controller 180.

[0037] In some embodiments, the thermocouple 198 may be secured to the outside of the target holder 190. In other embodiments, the thermocouple 198 may include a rigid sheath that can be used to position it relative to the target holder. In another embodiment, the thermocouple measurement point may be located directly within the capsule 191 containing the dopant material 195. In these embodiments, a ceramic insulator sheath may be used to protect the thermocouple wires to prevent corrosion of the thermocouple 198.

[0038] 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 be more positive 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 in a suitable position. The electrons, gas, and positive potential from the cathode 110 combine to form 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 and near the extraction orifice 140. Chemical etching 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 the extraction orifice 140 and used to prepare an ion beam.

[0039] The plasma is maintained at a more positive voltage than the target holder 190, thereby attracting negative ions and neutral atoms that are sputtered or otherwise released from the dopant material 195 toward the plasma.

[0040] 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 may be heated by additional means. For example, a heating element 170 may be disposed in or on the target holder 190 to further heat the doping material 195. The heating element 170 may be a resistive heating element or some other type of heater.

[0041] In some embodiments, target holder 190 may be made of a conductive material and may be grounded. In different embodiments, target holder 190 may be made of a conductive material and may be electrically floating. In different embodiments, target holder 190 may be made of a conductive material and may be maintained at the same voltage as wall 101. In other embodiments, target holder 190 may be made of an insulating material.

[0042] In yet another embodiment, the target holder 190 can be electrically biased relative to the arc chamber 100. For example, the target holder 190 can be made of a conductive material and can be biased by an independent power supply (not shown) to be at a different voltage than the wall 101. This voltage can have a more positive value or a more negative value than the voltage applied to the wall 101. As such, the dopant material 195 can be sputtered using an electrical bias.

[0043] The controller 180 may monitor the temperature of the doping material 195 using the thermocouple 198. In certain embodiments, the controller 180 may be in communication with the thermocouple 198 and with the heating element 170. Thus, the controller 180 may control the heating element 170 to maintain the doping material 195 at a desired or predetermined temperature. In other words, the controller 180 may vary the current through the heating element 170 to maintain the desired temperature as measured by the thermocouple 198. This may enable the controller 180 to control the feed rate of the doping material 195 into the arc chamber 100. In other embodiments, the controller 180 may measure the temperature of the doping material 195 indirectly, such as by measuring the temperature of the target holder 190 or some other component.

[0044] Target holder 190 is in communication with one end of shaft 200. The opposite end of shaft 200 may be in communication with actuator assembly 300. Actuator assembly 300 may be directly attached to one of walls 101. In other embodiments, actuator assembly 300 may be retracted from wall 101 to enable removal of target holder 190 from the main cylinder of arc chamber 100. The action of actuator assembly 300 enables target holder 190 to move linearly within arc chamber 100.

[0045] Figure 2 One embodiment of an actuator assembly 300 is shown. In this embodiment, the actuator assembly 300 includes a rear housing 310 and a front housing 340. The front housing 340 may be latched or otherwise connected to one of the walls 101 of the arc chamber 100. Alternatively, the front housing 340 may be set back from the wall 101. An outer housing 360 may be used to connect the rear housing 310 and the front housing 340.

[0046] The rear housing 310 has an actuator 320 within it. The actuator 320 may have a drive shaft 325. In some embodiments, the actuator 320 is an electric motor, but other types of actuators may be used. In one embodiment, the drive shaft 325 has a threaded distal end 326. A corresponding threaded member 330 may be in communication with the threaded distal end 326. The threaded member 330 may be attached to the shaft 200. As such, when the drive shaft 325 rotates, the threaded member 330 is pulled toward the actuator 320 or moved away from the actuator 320 depending on the direction of rotation. Since the shaft 200 is attached to the threaded member 330, the rotational movement of the drive shaft 325 causes the shaft 200 to similarly translate linearly in the X direction. This allows the target holder 190 to be disposed in different locations within the arc chamber 100.

[0047] In this embodiment, the shaft 200 includes a retaining plate 210. The retaining plate 210 is disposed within the actuator assembly 300 behind the front housing 340. The retaining plate 210 is welded or otherwise connected to the bellows 350. In some embodiments, the bellows 350 can be metal. The bellows 350 can also be welded or otherwise attached to the rear housing 310. The bellows 350 and the retaining plate 210 form a barrier between the vacuum conditions in the arc chamber 100 and the atmospheric conditions side outside the arc chamber 100. Therefore, when the drive shaft 325 rotates, the bellows 350 expands and contracts based on the direction of movement of the shaft 200.

[0048] Note that the thermocouple 198 is placed within the arc chamber 100 while maintaining the integrity of the vacuum conditions and that the wire 199 needs to exit the arc chamber 100. Figure 2 In an embodiment of the present invention, a first connector 390 is mounted within the arc chamber 100 on the front housing 340. The wire 199 extends from outside the actuator assembly 300 to the first connector 390. In this embodiment, a channel 311 can be formed in the rear housing 310 to enable the wire 199 to pass out of the actuator assembly 300. The wire 199 can then pass through the space between the bellows 350 and the outer housing 360. This space is part of the vacuum environment, and therefore a vacuum feedthrough 370 is used to maintain the vacuum. The vacuum feedthrough is a component that enables the wire 199 to pass but maintains a pressure difference between the two sides of the feedthrough. Therefore, the wire 199 passes through the channel 311 in the rear housing 310 and then passes through the vacuum feedthrough 370. The wire 199 then passes through the space between the outer housing 360 and the bellows 350 and finally terminates at the first connector 390.

[0049] The second connector 391 is mated with the first connector 390. The thermocouple wire 197 extends from the second connector 391 to the thermocouple 198. The thermocouple 198 may be a K-type thermocouple. In addition, the thermocouple wire 197 attached to the thermocouple 198 may be insulated. For example, in one embodiment, each of the two thermocouple wires 197 is individually coated with an insulating material. Then, the two thermocouple wires 197 may be wound together in an Inconel braid. In other words, the thermocouple wires 197 are individually coated to achieve electrical insulation and then the thermocouple wires 197 are wound in pairs to protect them from the harsh environment in the arc chamber 100. In another embodiment, the thermocouple wires 197 may be packaged in an alumina tube.

[0050] In some embodiments, the thermocouple wire 197 is coiled, such as Figure 2 As shown in . Thus, when the target holder 190 is extended and removed, the thermocouple wire 197 is coiled and uncoiled to compensate for the change in length.

[0051] In one embodiment, the thermocouple 198, the thermocouple wire 197, and the second connector 391 can be replaceable components. In addition, as described above, the thermocouple wire 197 in this embodiment can be individually insulated and then wrapped in a braid. In addition, the thermocouple wire 197 can be coiled to enable the length to be changed without kinking or interference.

[0052] A heating element 170 may be disposed within or on the target holder 190 to further heat the dopant material 195. In some embodiments, wires associated with the heating element 170 are routed together with the thermocouple wires 197.

[0053] Thermocouple 198 may be attached to target holder 190 in a variety of ways, which are described below.

[0054] Figure 3 A second embodiment of an actuator assembly 300 is shown. Many of the components are similar to Figure 2 190 and have been given identical reference designators. In this embodiment, shaft 200 may be hollow so that thermocouple wire 197 may be routed through the interior of shaft 200. Shaft 200 also has an opening 201 leading to the hollow interior. Opening 201 may be located on a side of holding plate 210 away from target holder 190. As such, opening 201 is exposed to atmospheric conditions. If thermocouple 198 is located within the hollow interior of shaft 200, a vacuum feedthrough may not be required. However, if thermocouple 198 is located on an outer surface of target holder 190 (e.g., Figure 4), a vacuum feedthrough 370 may be used to maintain the vacuum within the arc chamber 100. The vacuum feedthrough 370 will be provided at the entrance to the hollow interior of the shaft 200.

[0055] The thermocouple wire 197 passes through the opening 201 and can exit through the channel 311 in the rear housing 310. In some embodiments, one or more cable holders 351 can be used to hold the thermocouple wire 197 in place. In some embodiments, the wire 199 that communicates with the controller 180 is the same as the thermocouple wire 197 that passes through the hollow interior of the shaft 200. In other embodiments, a connector can be provided between the thermocouple 198 and the controller 180 to form two separate wire sections. For example, the portion of the thermocouple wire that is exposed to the plasma may need to be replaced more often. Therefore, this section of the wire can be formed as a replaceable unit by inserting a connector between the thermocouple 198 and the controller 180.

[0056] Thus, in this embodiment, the shaft has a hollow interior for routing the thermocouple wire 197 from the thermocouple 198 to the interior of the actuator assembly 300. As described, if the thermocouple 198 is disposed under vacuum conditions, a vacuum feedthrough 370 may be employed at the entrance to the interior of the shaft 200, such as Figure 4 as shown in .

[0057] In certain embodiments, the thermocouple wires 197 are individually insulated and then wound together in an Inconel braid or an alumina tube. In other embodiments, the Inconel braid is not employed because the shaft 200 protects the thermocouple wires.

[0058] Figures 2 to 4 Several systems are described that may be used to run wires from the controller 180 to the thermocouple 198 . Figures 5 to 9C Various embodiments are shown with respect to placing thermocouple 198 on target holder 190 .

[0059] Figure 5An enlarged view of the target holder 190 is shown. In certain embodiments, the target holder 190 includes a target base 193 that is affixed or otherwise attached to the shaft 200. The target holder 190 may also include a crucible 196. The crucible 196 contains a doping material 195. In certain embodiments, the crucible 196 may be made of graphite. In some embodiments, the crucible 196 may be a hollow cylinder with two open ends. A crucible plug 194 may be disposed between the crucible 196 and the target base 193. The crucible plug 194 is used to plug one of the open ends of the crucible 196. The target base 193 may be secured to the crucible 196 using a clamp 410. As described above, a porous plug 192 may be used to plug the second open end of the crucible 196. As described above, this porous plug 192 may be made of graphite foam or another suitable material.

[0060] exist Figure 5 In the embodiment of the present invention, the thermocouple 198 is mounted on the outer surface of the crucible 196. A potting material 400 can be used to hold the thermocouple 198 in place. Thermocouple wires 197 can be run along the outside of the target holder 190.

[0061] Figure 6 Another embodiment of a target holder 190 is shown. Many of the components are similar to Figure 5 196 and have been given identical reference designators. In this embodiment, a conduit 420 is formed in the target base 193 and optionally in the crucible plug 194. Thermocouple wires 197 pass through the conduit 420 and thermocouples 198 are mounted on the outer surface of the crucible 196, just as Figure 5 A potting material 400 may be used to hold the thermocouple 198 in place.

[0062] Figure 7 Another embodiment of a target holder 190 is shown. Many of the components are similar to Figure 6 196 and have been given identical reference designators. In this embodiment, rather than using a potting material, a set screw 430 is used to hold the thermocouple 198 in place. The set screw 430 can be screwed into a threaded shallow hole in the crucible 196. In some embodiments, the threaded shallow hole does not pass through the interior of the crucible 196.

[0063] Note that set screw 430 may be used with Figure 5 In other words, the thermocouple wire 197 can be laid around the outside of the target holder 190 and secured to the crucible 196 using the set screws 430 .

[0064] In conclusion, Figures 5 to 7A different target holder 190 is shown with a thermocouple 198 in contact with the outer surface of a crucible 196. This thermocouple 198 may be attached to the crucible 196 using a potting material 400 or a set screw 430. Other fastening techniques may also be employed.

[0065] Additionally, a thermocouple 198 may be embedded in the wall of the crucible 196 . Fig. 8A An embodiment is shown in which a channel 440 is formed in the wall of the crucible. Many of the components are similar to Figure 6 196 and have been given identical reference designators. Channel 440 is narrower than the width of the wall of crucible 196. Thermocouple 198 is inserted into channel 440. A potting material (not shown) may be used to hold thermocouple 198 in place. In this embodiment, channel 440 may extend through target base 193 and optionally through crucible plug 194. Figure 8B In another embodiment shown in FIG. 4 , the passage 440 exits on the outer surface of the crucible 196. In this embodiment, the passage does not extend through the target base 193 or the crucible plug 194.

[0066] In another embodiment, channel 440 may extend into capsule 191 so that thermocouple 198 is actually in contact with the interior of capsule 191 and / or doping material 195. In these embodiments, a ceramic insulator sheath may be employed to protect thermocouple 198 and thermocouple wires 197.

[0067] Thermocouple 198 may also be in contact with crucible plug 194, such as FIG. 9A to FIG. 9C Many of the components in the component are similar to Figure 6 198 and have been given identical reference designators. In these embodiments, a cavity 450 is provided in the target base 193. The cavity 450 provides a location where a thermocouple 198 can be placed. A passage 460 is formed in the target base 193 from the outside of the target base 193 to the cavity 450. Thermocouple wire 197 enters the cavity 450 via passage 460. Fig. 9A Thermocouple 198 is shown held in place through the use of potting material 400 . Fig. 9B Thermocouple 198 is shown held in place using set screw 430. Fig. 9C The thermocouple 198 is shown being held in place using a spring 470. Of course, other force-based means of holding the thermocouple 198 in place may also be used.

[0068] Although the above disclosure describes various means for applying the wires of the thermocouple 198 to the target holder 190, the same techniques can also be used to apply the resistive wires to the target holder 190. These resistive wires can be used as the heating element 170. For example, the resistive wires can be in contact with all or a portion of the outer surface of the crucible 196, such as Figures 1 to 4As shown in . Figures 2 to 7 Alternatively, the resistance wire may be embedded in the wall of the crucible, with FIG. 8A to FIG. 8B In another embodiment, the resistive wire may be in contact with the crucible plug 194, for example FIG. 9A to FIG. 9C As shown in . When current passes through the resistive wire, heat is generated. This allows the controller 180 to control the temperature of the doping material 195 by another mechanism.

[0069] In some embodiments, the resistor wire is bundled with the thermocouple wire 197. In these embodiments, the resistor wire is routed together with the thermocouple wire 197.

[0070] In other embodiments, the resistor wires are disposed in a separate braid or bundle and traverse the same path as the thermocouple wires 197 .

[0071] In still other embodiments, the resistive wire may be in contact with a portion of the target holder 190 (eg, the crucible 196 ) while the thermocouple 198 is in contact with another portion of the target holder 190 (eg, the crucible plug 194 ). Fig.10 An embodiment is shown in which the resistor wire 500 is separated from the thermocouple wire 197. This embodiment is similar to Figure 2 , but includes a third connector 510 and a fourth connector 520. The third connector 510 can be mounted to the front housing 340. The wire 540 is routed from the controller 180 to the third connector 510. In some embodiments, the components for routing the wire 540 are similar to the components for routing the wire 199. For example, the channel 311 and the vacuum feedthrough 370 can be used. The resistive wire 500 can be coiled so that the length can be changed and can be connected to the outer surface of the crucible or the crucible plug.

[0072] although Fig.10 A third connector and a fourth connector are shown, but it should be understood that the resistor wire 500 can also be routed with the wire 199 and larger connectors can be used.

[0073] Alternatively, a resistive wire 500 may be routed through the shaft 200, similar to Figure 3 to Figure 4 The laying of the wire 199 shown in FIG.

[0074] The above disclosure sets forth various embodiments that enable controller 180 to use thermocouple 198 to measure the temperature of a component (ie, crucible, crucible plug, etc.) to monitor the temperature of doping material 195. Controller 180 may use this information in various ways.

[0075] It may be advantageous to heat the doping material 195 to a temperature within a predetermined range. For example, at low temperatures, the doping material 195 may not melt and therefore may not release dopant vapor from the target holder 190. However, at too high a temperature, the melting rate of the doping material may be too great. This may cause the doping material to accumulate in the arc chamber 100. Additionally, changes in the melting rate may also affect the beam current and other parameters.

[0076] By monitoring the temperature at or near the target holder 190, the controller 180 may be able to better regulate the temperature of the doping material 195. For example, the controller 180 may monitor the temperature of the doping material 195. If the temperature is not within a predetermined range, the controller may change the current through the filament power supply 165, change the arc voltage, change the cathode bias voltage, change the rate at which gas flows into the arc chamber 100, change the position of the target holder 190 in the arc chamber 100, change the beam extraction current, or perform a combination of these actions. In addition, if the first and second electrodes are disposed on the wall 101, the voltage applied to these electrodes may also be changed by the controller 180 based on the temperature of the doping material 195. Additionally, in embodiments that employ a heater (e.g., by using the resistive wire 500), the controller 180 may change the current through the heater to change the temperature of the doping material 195.

[0077] In certain embodiments, the controller 180 can move the position of the target holder 190 within the arc chamber 100 based on the temperature of the dopant material 195. For example, when the target holder 190 is directly disposed in a cylindrical region defined between the cathode 110 and the repeller 120, the target holder 190 can be heated to a higher temperature. To slow down the heating of the dopant material, the target holder 190 can be linearly moved out of the cylindrical region. Conversely, to increase the temperature of the dopant material 195, the target holder 190 can be moved into the cylindrical region.

[0078] The controller 180 may employ various closed-loop algorithms to determine parameters associated with the IHC ion source 10 based on the temperature obtained by the thermocouple 198 .

[0079] Although the above disclosure describes the use of thermocouples 198, other temperature sensors may be used. For example, optical measurements, pyrometers, and color points are all indirect methods of detecting the temperature of the target holder 190. Resistance temperature detectors (RTDs) and wireless thermocouple readers may also be used. Therefore, the above disclosure is not limited to the use of thermocouples.

[0080] Furthermore, while the above disclosure describes the thermocouple 198 as being in contact with the target holder 190 or the dopant material 195, other embodiments are possible. For example, the thermocouple 198 (or other temperature sensor) may measure the temperature of another component within the arc chamber 100 and estimate the temperature of the dopant material based on this measured temperature. Such other component may be a wall of the arc chamber 100, the shaft 200, the repeller 120, the front housing 340, or another component.

[0081] In addition, the control described above may be performed using an open loop technique. For example, empirical data may be collected to determine the temperature of the doping material based on various parameters (e.g., cathode bias voltage, arc voltage, feed gas flow rate, and position of the target holder). The empirical data may also determine the temperature of the doping material based on time. Using a table or equation, the controller 180 may change one or more of the parameters to maintain the doping material 195 within a predetermined range. For example, the controller 180 may move the target holder 190 over time to maintain its temperature within a desired range.

[0082] Although the above disclosure describes the use of a target holder in an indirectly heated cathode ion source, the present disclosure is not limited to this embodiment. The target holder, actuator assembly, and thermocouple may also be used in other ion sources or plasma sources, such as a capacitively coupled plasma source, an inductively coupled plasma source, a Bernas source, or another suitable source.

[0083] The embodiments of the present application described above may have many advantages. The use of a pluggable target holder enables the use of pure metal dopants as sputtering targets in environments that exceed the melting temperature of the pure metal dopant. Conventionally, oxides / ceramics or other solid composites containing dopants with melting temperatures greater than 1200°C are used. Using composites containing dopants instead of pure materials can severely dilute the available doping material. For example, when using Al 2 O 3 As a substitute for pure aluminum, the stoichiometry of the ceramic components not only introduces impurities into the plasma, which may introduce undesirable masses that coincide with the dopant of interest, but also results in lower beam currents than pure elemental targets. 2 O 3 It can also result in the production of undesirable byproducts such as oxides and nitrides, which can deposit along the beam line and impair the operation of the ion implanter. 2 O 3 The beam optics are then chemically cleaned to maintain the stability of the ion beam.

[0084] In one experiment, beam currents as high as 4.7 mA were achieved using a pure aluminum sputtering target, while 2 O3 The maximum beam current achievable with the target is less than 2 mA. Using pure metals will also increase multi-charge beam current by 50% to 75% compared to beam currents obtained from oxides / ceramics of the same metal species. Large volumes of pure metals can be accessed when needed through pluggable containers, and solid targets can be safely removed from the arc chamber to utilize other species.

[0085] In addition, by monitoring the temperature of the dopant material, the ion source can be controlled to ensure that the melting rate of the dopant material is within a predetermined range. Specifically, without temperature control, the dopant feedstock may become unstable and prone to runaway effects, which may cause inconsistent beam performance and undesirable accumulation of dopant material in the arc chamber. Therefore, temperature control can prevent the exponential growth of dopant vapor in the arc chamber. It also enables faster tuning of the ion source.

[0086] Additionally, by monitoring the temperature of the dopant material, this information can be used during the beam tuning process, thus making the beam performance more reliable.

[0087] The scope of the present disclosure is not limited by the specific embodiments described herein. In fact, by reading the foregoing description and drawings, in addition to the embodiments and modifications described herein, a person skilled in the art will also understand various other embodiments of the present disclosure and various modifications to the present disclosure. Therefore, these other embodiments and modifications are intended to be 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, a person skilled in the art should recognize that its validity is not limited thereto and that the present disclosure can be beneficially implemented in any number of environments for any number of purposes. Therefore, the claims set forth above should be interpreted in light of the full breadth and spirit of the invention described herein.

Claims

1. A target holder for accommodating doping materials in an ion source, the target holder comprising: Target base; The crucible is formed into a hollow cylinder; as well as A porous plug covers an open end of the crucible, wherein a gaseous doping material can pass through the porous plug.

2. The target holder according to claim 1, further comprising a crucible plug, the crucible plug covering an opposite open end of the crucible and disposed adjacent to the target base. 3 . The target base according to claim 1 , further comprising a thermocouple, wherein the thermocouple is in communication with the target base.

4. The target holder of claim 3, wherein the thermocouple is attached to an outer surface of the crucible.

5. The target holder of claim 3, wherein the thermocouple is disposed in a channel in a wall of the crucible.

6. The target holder of claim 3, further comprising a crucible plug covering an opposite open end of the crucible and disposed proximate to the target base, wherein a cavity is disposed in the target base proximate to the crucible plug, and the thermocouple is disposed in the cavity proximate to the crucible plug.

7. The target base of claim 6, wherein a passage is provided in the target base, the passage communicating with the cavity to allow wires to be routed to the thermocouple.

8. The target backing of claim 3, further comprising a shaft affixed to the target base, wherein an interior of the shaft is hollow to allow a wire to be routed through the hollow interior of the shaft to the thermocouple.

9. The target backing of claim 1, further comprising a heating element in communication with the target backing, wherein the heating element comprises a resistive wire.

10. The target backing of claim 1, wherein the porous plug comprises graphite foam.

11. The target holder of claim 1 , further comprising a clamp, wherein the clamp secures the target holder to the crucible.

12. The target mount of claim 1, wherein the target base is attached to a shaft.

13. An indirect heating cathode ion source, comprising: an arc chamber including a plurality of walls connecting the first end and the second end; an indirectly heated cathode disposed on the first end of the arc chamber; as well as The target seat as claimed in claim 1.

14. The indirectly heated cathode ion source of claim 13, wherein the target support is attached to a shaft.

15. The indirectly heated cathode ion source of claim 14, further comprising an actuator in communication with the target holder for moving the target holder within the arc chamber.

16. An indirect heating cathode ion source, comprising: an arc chamber including a plurality of walls connecting the first end and the second end; an indirectly heated cathode disposed on the first end of the arc chamber; a shaft extending into the arc chamber; as well as Target mount, including: a target base attached to the shaft; a crucible shaped as a hollow cylinder, wherein one end of the crucible is disposed adjacent to the target base; and A porous plug covers an open end of the crucible, wherein a gaseous doping material can pass through the porous plug.

17. The indirectly heated cathode ion source of claim 16, further comprising a crucible plug covering an opposite open end of the crucible and disposed adjacent to the target base.

18. The indirectly heated cathode ion source of claim 16, further comprising a thermocouple in communication with the target support.

19. The indirectly heated cathode ion source of claim 18, wherein the thermocouple is attached to an outer surface of the crucible.

20. The indirectly heated cathode ion source of claim 18, wherein the thermocouple is disposed in a channel in a wall of the crucible.

21. The indirect heated cathode ion source according to claim 18, further comprising a crucible plug, which covers an opposite open end of the crucible and is arranged near the target base, wherein a cavity is arranged in the target base near the crucible plug, and the thermocouple is arranged in the cavity near the crucible plug.

22. The indirectly heated cathode ion source of claim 21, wherein a channel is provided in the target support, the channel communicating with the cavity to allow wires to be routed to the thermocouple.

23. The indirectly heated cathode ion source of claim 18, wherein the interior of the shaft is hollow to allow wires to be routed through the hollow interior of the shaft to the thermocouple.

24. The indirectly heated cathode ion source of claim 16, further comprising a heating element in communication with the target support, wherein the heating element comprises a resistive wire.

25. The indirectly heated cathode ion source of claim 16, wherein the porous plug comprises graphite foam.

26. The indirectly heated cathode ion source of claim 16, further comprising a clamp, wherein the clamp secures the target pedestal to the crucible.

27. The indirectly heated cathode ion source of claim 16, further comprising an actuator in communication with the shaft to move the target holder within the arc chamber.

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