Cooled sputtering target for ion source

Abstract

An ion source having a target holder for holding a solid dopant material is disclosed. The target holder is mounted on a shaft that can communicate with an actuator, thereby enabling the solid dopant material to be inserted into and retracted from the arc chamber. The shaft and / or target holder are actively cooled so that the solid dopant material is below its melting point. In this way, the solid dopant material can be inserted into the arc chamber without melting. The cooling mechanism used may include gas cooling, liquid cooling, thermoelectric cooling, or other cooling techniques.

Description

Technical Field

[0001] This application claims priority to U.S. Patent Application No. 18 / 232,169, filed Aug. 9, 2023, the entire disclosure of which is incorporated herein by reference.

[0002] Embodiments of the present disclosure relate to an injection device and an ion source, and more particularly to an ion source having a target holder for holding a solid dopant material, wherein the temperature of the dopant material can be maintained below its melting point.

Background Art

[0003] To generate ions for use in semiconductor processing equipment, various types of ion sources can be used. For example, an indirectly heated cathode (IHC) ion source operates by supplying current to a filament disposed behind a cathode. The filament emits thermionic electrons, which are accelerated towards the cathode to heat the cathode, and then the cathode emits electrons into the arc chamber of the ion source. The cathode is disposed at one end of the arc chamber. A repeller can be disposed at the end of the arc chamber opposite the cathode. The cathode and the repeller can be biased to repel electrons and direct them back towards the center of the arc chamber. In some embodiments, a magnetic field is used to further confine electrons within the arc chamber. A plurality of sides are used to connect the two ends of the arc chamber.

[0004] Along one of these sides, an extraction aperture is disposed near the center of the arc chamber, through which ions generated within the arc chamber can be extracted.

[0005] In certain embodiments, it may be desirable to use materials in solid form as dopant species. For example, in some systems, it may be desirable to generate ions of aluminum, gallium, indium, magnesium, antimony, tin, lead, or different metals. Typically, a crucible is used to vaporize these metals or metal-containing compounds. However, these systems may be limited in the beam current that can be produced. Furthermore, using solid pure dopants may result in molten metal leaching into the ion source or being uncontrollably discharged due to the vacuum environment. Alternatively, dopant-containing materials containing the desired dopant material may be used. However, these materials may introduce undesirable species and reduce the effective desired dopant beam current.

[0006] Therefore, an ion source that can be used with solid dopant materials with low melting points, such as certain metals, would be beneficial. [Overview of the project]

[0007] An ion source having a target holder for holding a solid dopant material is disclosed. The target holder is mounted on a shaft that can communicate with an actuator, thereby enabling the solid dopant material to be inserted into and retracted from the arc chamber. The shaft is actively cooled so that the solid dopant material is below its melting point. In this way, the solid dopant material can be inserted into the arc chamber without melting. The cooling mechanism used may include air cooling, liquid cooling, thermoelectric cooling, or other cooling techniques.

[0008] According to one embodiment, an ion source is disclosed. The ion source comprises an arc chamber having a plurality of walls connecting a first end and a second end; a target holder for holding a solid dopant material; a shaft connected to the target holder and extending the target holder toward the arc chamber; and a cooling system for actively cooling the solid dopant material. In some embodiments, the cooling system actively cools the shaft. In some embodiments, the shaft is made of copper and at least a portion of the shaft is covered by a sheath made of a non-copper material. In some embodiments, the shaft is cooled using a cooling fluid.

[0009] In certain embodiments, the shaft includes a hollow cavity with an inlet channel and an outlet channel so that a cooling fluid flows through the inside of the shaft. In certain embodiments, a partition is located within the hollow cavity and separates the inlet channel from the outlet channel. In certain embodiments, the shaft includes two tubes, the hollow cavity defining the outer tube, the inner tube being located within the outer tube and not extending to the distal end of the shaft, and the two tubes forming the inlet channel and the outlet channel.

[0010] In certain embodiments, the shaft is cooled by flowing a cooling gas outwards from the shaft. In some embodiments, the ion source includes a cooling tube that is in fluid communication with a fluid cooler, and the cooling tube is wrapped around a portion of the shaft. In some embodiments, the ion source includes a cooling plate fixed to the proximal end of the shaft, and the cooling plate functions as a heat sink. In certain embodiments, channels are located within the cooling plate, and a cooling fluid flows through the cooling plate to maintain the cooling plate within a predetermined temperature range. In some embodiments, the shaft and / or target holder are actively cooled using a heat pump fixed thereto. In some embodiments, the target holder is actively cooled using a cooling fluid that passes through the target holder. In other embodiments, an ion implantation apparatus is disclosed. The ion implantation apparatus comprises an ion source that generates an ion beam and one or more beamline components that direct the ion beam toward a workpiece, wherein the ion source is an arc chamber having a plurality of walls connecting a first end and a second end; a target holder that holds a solid dopant material; a shaft connected to the target holder and extending the target holder toward the arc chamber; and a cooling system for actively cooling the solid dopant material. In some embodiments, the ion implantation apparatus comprises a thermocouple for measuring the temperature of the solid dopant material and a controller, the controller using information from the thermocouple to maintain the solid dopant material within a desired temperature range. In certain embodiments, the controller actively cools the shaft to maintain the solid dopant material within a desired temperature range. In certain embodiments, the shaft is cooled by a fluid passing through the inside of the shaft or a fluid passing outside the shaft, and the controller controls the temperature of the solid dopant material by controlling the flow rate of the fluid. In certain embodiments, the shaft is cooled by attaching a cooling plate to the proximal end of the shaft, and the controller controls the temperature of the solid dopant material by controlling the temperature of the cooling plate. In some embodiments, the shaft and / or target holder is cooled by attaching one or more heat pumps, and the controller controls the temperature of the solid dopant material by controlling the power supplied to one or more heat pumps. In some embodiments, the target holder is cooled by a fluid passing through the inside of the target holder, and the controller controls the temperature of the solid dopant material by controlling the flow rate of the fluid.

[0011] The accompanying drawings are referenced herein to better understand this disclosure, and such drawings are incorporated herein by reference. [Brief explanation of the drawing]

[0012] [Figure 1]According to one embodiment, this is an indirectly heated cathode (IHC) ion source equipped with a target holder having a cooling system. [Figure 2A-2D] This describes the attachment between a target holder and a solid dopant material according to several embodiments. [Figure 3A-3G] These are different cooling systems for cooling the shaft. [Figure 4] This is a cooling system for cooling the target holder. [Figure 5] This is an ion implantation apparatus that can utilize any of the ion sources described herein. [Modes for carrying out the invention]

[0013] As mentioned above, at very high temperatures, solid dopants in the ion source may melt, potentially leading to undesirable and / or uncontrolled accumulation of dopants in the arc chamber, as well as potential discharge or displacement of material into the chamber.

[0014] Figure 1 shows an ion source that may be an IHC ion source 10 having a target holder that enables sputtering of a solid dopant material without melting. The IHC ion source 10 includes an arc chamber 100 having two opposing ends and walls 101 connected to these ends. The walls 101 of the arc chamber 100 may be constructed of a conductive material and the walls 101 may be electrically connected to each other. In some embodiments, a liner may be located near one or more of the walls 101. A cathode 110 is located within the arc chamber 100, at the first end 104 of the arc chamber 100. A filament 160 is located behind the cathode 110. The filament 160 is in contact 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 thermionic electrons. The cathode bias power supply 115 negatively biases the filament 160 relative to the cathode 110, so that these thermionic electrons are accelerated from the filament 160 toward the cathode 110 and heat the cathode 110 when they strike the back surface of the cathode 110. The cathode bias power supply 115 can bias the filament 160, for example, so that the filament 160 has a voltage that is 200V to 1500V lower in the negative direction than the voltage of the cathode 110. The voltage difference between the cathode 110 and the filament 160 may be called the cathode bias voltage. The cathode 110 then emits thermionic electrons on its front surface into the arc chamber 100.

[0015] Thus, the filament power supply 165 supplies current to the filament 160. The cathode bias power supply 115 biases the filament 160 so that it is negatively biased compared to the cathode 110, thereby inducing electrons from the filament 160 toward the cathode 110. In certain embodiments, the cathode 110 may be biased toward the arc chamber 100 by, for example, a bias power supply 111. The voltage difference between the arc chamber 100 and the cathode 110 may be referred to as the arc voltage. In other embodiments, the cathode 110 may be electrically connected to the arc chamber 100 so that it has the same voltage as the wall 101 of the arc chamber 100. In these embodiments, the bias power supply 111 may not be used, and the cathode 110 may be electrically connected to the wall 101 of the arc chamber 100. In certain embodiments, the arc chamber 100 is connected to electrical ground.

[0016] A repeller 120 may be located at the second end 105 opposite the first end 104. The repeller 120 may be biased 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 so that it is at the same voltage as the walls 101 of the arc chamber 100. In these embodiments, the repeller bias power supply 123 may not be used, and the repeller 120 may be electrically connected to the walls 101 of the arc chamber 100. In some embodiments, a bias power supply 111 may be used to bias the repeller 120. In yet other embodiments, the repeller 120 may not be used or may be electrically floating.

[0017] The cathode 110 and the repeller 120 are each made of a conductive material (such as metal or graphite).

[0018] In certain embodiments, a magnetic field is generated within the arc chamber 100. This magnetic field is intended to confine electrons along one direction. The magnetic field typically runs parallel to the wall 101 from the first end 104 to the second end 105. For example, electrons can be confined within a column parallel to the direction from the cathode 110 to the repeller 120 (i.e., the y-direction). Thus, the electrons are not affected at all by electromagnetic forces moving in the y-direction. However, electron movement in other directions may be affected by electromagnetic forces.

[0019] An extraction opening 140 may be located on one side of the arc chamber 100 (referred to as the extraction plate 103). In Figure 1, the extraction opening 140 is located on the side parallel to the XY plane (perpendicular to the plane of the paper). Furthermore, the IHC ion source 10 also includes a gas inlet 106 through which the gas to be ionized can be introduced into the arc chamber 100. In some embodiments, multiple gases may be combined and enter the arc chamber 100 through the gas inlet 106. In other embodiments, multiple gas inlets may be used to introduce different gases.

[0020] In certain embodiments, the first and second electrodes may be positioned on opposite walls 101 of the arc chamber 100, such that the first and second electrodes are located within the arc chamber 100 on the wall adjacent to the extraction plate 103. The first and second electrodes may each be biased by their respective power supplies. In certain embodiments, the first and second electrodes may be connected to a common power supply. However, in other embodiments, to allow for maximum flexibility and the ability to adjust the output of the IHC ion source 10, the first electrode may be connected to a first electrode power supply and the second electrode to a second electrode power supply.

[0021] The controller 180 can communicate with one or more power supplies, thereby modifying the voltage or current supplied by these power supplies. 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-temporary storage element such as semiconductor memory, magnetic memory, or another suitable memory. This non-temporary storage element may contain instructions and other data that enable the controller 180 to perform the functions described herein.

[0022] The IHC ion source 10 also includes a target holder 190 that can be inserted into and retracted from the arc chamber 100. In the embodiment shown in Figure 1, the target holder 190 enters the arc chamber along one of the walls 101 of the arc chamber 100. In certain embodiments, the target holder 190 may enter the arc chamber 100 in a central plane between a first end 104 and a second end 105. In other embodiments, the target holder 190 may enter the arc chamber 100 at a location other than the central plane. In the embodiment shown in Figure 1, the target holder 190 enters the arc chamber 100 on the side opposite to the extraction opening 140. However, in other embodiments, the target holder 190 may enter through a side adjacent to the extraction plate 103. The target holder 190 can move between a first position and a second position.

[0023] The target holder 190 includes a first surface facing the arc chamber 100. The solid dopant material 195 can be fixed to the first surface of the target holder 190. The solid dopant material can be a pure metal such as indium, aluminum, magnesium, antimony, gallium, tin, lead, or a different metal, or a dopant-containing material. The solid dopant material 195 can be in the form of a block of material. In some embodiments, the solid dopant material may be a pure metal, with more than 95% of the dopant material containing metal. In other embodiments, the solid dopant material 195 can be a compound containing a dopant material such as an alloy or a ceramic material. For example, if aluminum is the desired dopant, the solid dopant material can be pure aluminum, an Al-X alloy (where X is B, Cr, Co, Cu, Fe, Mo, Sc, Ti, Zn, Mg, Zr, Dy, Er, Gd, Mn, Nd, Ni, Sm, Ag, Ta, V), or a ceramic such as Al2O3, AlF3, AlN, AlP, Al2Se3, Al2S3, Al2Te3, and Al2TiO5.

[0024] In some embodiments, a thermocouple 198 may be proximate to the target holder 190 or the solid dopant material 195 to measure the temperature of the solid dopant material 195. This thermocouple 198 can communicate with the controller 180. The thermocouple 198 can include one or more wires 199 that electrically connect the thermocouple 198 to the controller 180.

[0025] The target holder 190 is located at the distal end of the shaft 200. In certain embodiments, the target holder 190 can be a separate component fixed to the distal end of the shaft 200. In other embodiments, the target holder can be the distal end of the shaft 200 such that the distal end of the shaft 200 is directly fixed to the solid dopant material 195. In some embodiments, the target holder 190 can have a larger diameter than the rest of the shaft to increase the surface area in contact with the solid dopant material 195.

[0026] The shaft 200 can be constructed from a thermally conductive material such as aluminum, stainless steel, tungsten, copper, or another material.

[0027] The proximal end of the shaft 200 can be connected to an actuator 210. The operation of the actuator 210 can move the target holder 190 linearly into or out of the arc chamber 100. The shaft 200 passes through a vacuum seal 197 such that a first portion of the shaft 200 is located in a cavity 196 that communicates with the arc chamber 100, and a second portion of the shaft is located under atmospheric conditions. The lengths of the first and second portions vary based on the position of the target holder 190.

[0028] During operation, the filament power supply 165 supplies current to the filament 160, causing the filament 160 to emit thermionic electrons. These electrons strike the back surface of the cathode 110, which may be more positive than the filament 160, heating the cathode 110, which in turn releases electrons into the arc chamber 100. These electrons collide with molecules of the gas supplied into the arc chamber 100 through the gas inlet 106 under the influence of a magnetic field. A carrier gas such as argon and / or an etching gas such as nitrogen fluoride or chlorine may be introduced into the arc chamber 100 through a appropriately located gas inlet 106. The combination of electrons from the cathode 110, the gas, and the positive potential creates a plasma. In certain embodiments, the electrons and positive ions may be partially confined by the magnetic field. In certain embodiments, the plasma is confined near the center of the arc chamber 100, near the extraction opening 140. Plasma-induced chemical etching or physical sputtering converts the solid dopant material 195 into a gas phase, causing ionization. The ionized feed material can then be extracted through the extraction opening 140 and used to generate an ion beam.

[0029] Negative ions and neutral atoms emitted from the solid dopant material 195 by sputtering or other means are attracted towards the plasma because the plasma is maintained at a more positive voltage than the target holder 190.

[0030] The controller 180 can control the actuator 210 so that the outermost surface of the solid dopant material 195 is coplanar with the wall 101. Once the solid dopant material 195 is sputtered, the controller 180 can move the shaft 200 of the actuator 210 in parallel so that the surface of the solid dopant material extends further toward the arc chamber 100 in order to maintain this position. In other embodiments, the solid dopant material 195 may extend into the arc chamber 100 to expose more of the solid dopant material 195 to the plasma.

[0031] In particular, in some embodiments, the shaft 200 is actively cooled using a cooling system 215. In this way, the temperature of the target holder 190 is reduced by physical contact with the cooled shaft. Furthermore, since the solid dopant material 195 is in physical contact with the target holder 190, its temperature is also reduced by the cooling system 215. In other embodiments, the cooling system 215 actively cools the target holder 190. For example, in certain embodiments, a thermal paste is used to fix the solid dopant material 195 to the first surface of the target holder 190. Furthermore, the shape and / or contour of the first surface of the target holder 190 and the solid dopant material 195 may be configured to maximize the surface area of ​​the target holder 190 in contact with the solid dopant material 195.

[0032] For example, Figures 2A to 2D show various configurations of the target holder 190 and the solid dopant material 195 to increase the surface area of ​​the contact area of ​​these components. In Figure 2A, the solid dopant material 195 is formed to extend along the outer edge of the target holder 190 such that a portion of the solid dopant material surrounds the outer circumference of the target holder 190. Furthermore, one or more protrusions 193 may be generated on the first surface of the target holder 190. These protrusions 193 increase the contact area and also provide a more secure attachment. In Figure 2B, the target holder 190 has a larger diameter than the rest of the shaft 200. This makes it possible to fix a larger amount of solid dopant material 195 to the target holder 190 and also creates a larger contact area between these components. One or more protrusions 193 may also be located on the first surface of the target holder 190. Figure 2C shows an embodiment in which the protrusions 193 comprise an annular ring arranged along the outer edge of the first surface. Similar to Figure 2B, the target holder 190 has a larger diameter than the rest of the shaft 200. Note that the embodiments shown in Figures 2B and 2C may be combined such that the projection 193 is located inside the first surface, as well as projections located along the outer circumference. Figure 2D shows an embodiment similar to Figure 2B. However, in this embodiment, the target holder 190 has the same diameter as the rest of the shaft 200.

[0033] As described above, the shaft 200 or the target holder 190 is actively cooled by the cooling system 215. This can be achieved in several different ways.

[0034] Figures 3A–3G show various embodiments in which the shaft 200 is actively cooled. These figures show a shaft 200 having a first portion located within the cavity 196 and a second portion located in the atmospheric environment, the two portions separated by a vacuum seal 197. Note that the sizes of the first and second portions change as the shaft 200 moves. The rest of the IHC ion source 10 is shown in Figure 1.

[0035] Figure 3A shows a first embodiment. In this embodiment, a cooling channel is formed within the shaft 200. The shaft 200 may be made of a material having appropriate mechanical strength, thermal stability, and thermal conductivity, such as copper, tungsten, stainless steel, aluminum, or another material. Specifically, an inlet channel 301 is located within the shaft 200 and may extend to or near the distal end of the shaft 200. A fluid cooler 300 can be used to allow the circulation of a cooling fluid, such as water or gas, through the shaft 200. An outlet channel 302 is also located within the shaft 200 and attached to the inlet channel 301, allowing the cooling fluid to flow from the fluid cooler 300 through the inlet channel 301 and the outlet channel 302 back to the fluid cooler 300. Conduits 304 and 305 can be used to connect the fluid cooler 300 to the inlet channel 301 and the outlet channel 302, respectively. These conduits 304 and 305 may be flexible so that the shaft 200 can be moved in parallel while the fluid cooler 300 remains stationary.

[0036] In one embodiment shown in Figure 3A, a large channel is created within the shaft 200, and a partition 303 is inserted to separate the large channel into an inlet channel 301 and an outlet channel 302. A cross-section of this shaft 200 is also shown. In this embodiment, the shaft 200 may be made of tungsten, while the partition 303 is made of stainless steel.

[0037] Figure 3B shows a cross-section of the shaft 200 according to another embodiment utilizing a cooling fluid. The rest of the system is shown in Figure 3A. In this embodiment, the inlet and outlet channels may be implemented using two concentric tubes having different diameters, and the shaft 200 is hollow and forms the outer tube. The inner tube 202 is located within this outer tube but does not extend to the distal end of the shaft 200. In this embodiment, the cooling fluid flows from the fluid cooler 300 through the inner tube 202 toward the end of the shaft 200, and then returns to the fluid cooler 300 through the gap 203 between the outer diameter of the inner tube 202 and the inner diameter of the outer tube. Alternatively, the cooling fluid can flow from the fluid cooler 300 through the gap 203 and then return to the fluid cooler 300 through the inner tube 202.

[0038] It should be noted that, if desired, there may be more than two channels within the shaft 200. In another embodiment, the shaft 200 having the cooling channels may be formed using additive manufacturing. The cooling fluid may be any suitable fluid, such as deionized water or a cooled gas such as nitrogen or air. In some embodiments, the flow rate of the cooling fluid may be 1 L / min or more. It should be noted that the fluid cooler 300 is placed in an atmospheric environment by a vacuum seal 197.

[0039] Figure 3C shows a second embodiment. In this embodiment, the shaft 200 is actively cooled using a fan 320. The fan 320 blows a cooling gas, such as air which may be at room temperature, toward the shaft 200 at a flow rate of up to 10 m / s. In some embodiments, such as shown in Figure 3D, instead of a fan blowing the cooling gas, the shaft 200 is cooled by a cooling gas flowing toward the shaft 200 from a tube or several tubes 340, and the cooling gas is collected by an exhaust port or several exhaust ports 341. The exhaust ports 341 may include one or more pumps to draw the cooling gas past the shaft 200. This design allows for a greater cooling gas flow and increases cooling power. In both embodiments, the cooling gas flows past the outside of the shaft 200. In these embodiments, the shaft 200 may be aluminum, tungsten, stainless steel, or different metal alloys, or another material. In another embodiment, the shaft 200 may be copper due to its excellent thermal conductivity. In this embodiment, a sheath 201 made from a non-copper material may be placed on the outer surface of the shaft 200. Note that in some embodiments, the sheath 201 extends along the entire length of the shaft 200. In other embodiments, the sheath 201 may be applied only to the portion of the shaft 200 located within the cavity 196. The sheath 201 may be approximately 1 mm thick and may be made from tungsten or another non-copper material. Note that if a metal other than copper is used for the shaft 200, the sheath 201 may also be applied. Furthermore, this sheath 201 may also be used in the embodiments shown in Figures 3A, 3B, 3E, 3F, and 3G, as needed.

[0040] To further enhance heat conduction, the portion of the shaft 200 to which the air is directed may include fins or other structures to increase its surface area.

[0041] Other cooling systems 215 may be used to cool the outside of the shaft 200. For example, Figure 3E shows an embodiment in which a cooling tube 360 ​​is wrapped around a second portion of the shaft 200, the second portion of which is located in the atmospheric environment. The cooling tube 360 ​​may be in fluid communication with conduits 304, 305 that connect the cooling tube 360 ​​to a fluid cooler 300. A cooling fluid may pass through this cooling tube 360 ​​to cool the shaft 200. In some embodiments, the cooling fluid may be a gas. Alternatively, the cooling fluid may be a liquid.

[0042] In some embodiments, the conduits 304, 305 and the cooling tube 360 ​​are fixed in place so that the shaft 200 slides relative to the cooling tube 360. Thus, the section of the shaft 200 that contacts the cooling tube 360 ​​changes based on the position of the target holder 190. In another embodiment, the cooling tube 360 ​​is fixed to the shaft 200 and can be thermally bonded by an interfacial medium such as a thermal paste. In this embodiment, the conduits 304, 305 can be flexible so that the cooling tube 360 ​​can be moved in parallel while the fluid cooler 300 remains stationary.

[0043] Figure 3F shows another embodiment of the cooling system 215. In this embodiment, a cooling plate 330 is fixed to the proximal end of the shaft 200. Note that in this embodiment, the actuator 210 can linearly move the cooling plate 330 and the shaft 200. The cooling plate 330 functions as a heat sink and can be maintained within a predetermined temperature range. For example, channels are arranged within the cooling plate 330 so that a cooling fluid can flow through it, and the cooling plate 330 can be maintained within a predetermined temperature range. This cooling fluid may be deionized water or a cooled gas such as nitrogen or air. Conduits 304, 305 connecting the fluid cooler 300 to the channels in the cooling plate 330 may be flexible so that they can expand and contract as the cooling plate 330 and the shaft 200 move toward and away from the arc chamber 100. In certain embodiments, the shaft 200 is further cooled through the use of a fan 320 that provides air cooling. In other embodiments, the fan 320 may not be present. In certain embodiments, the shaft 200 is further cooled through the use of a tube 340 having a complementary exhaust port 341. In some embodiments, the cooling plate 330 is also positioned around a portion of the shaft 200, thus increasing the cooling contact area and efficiency without hindering the movement of the shaft 200.

[0044] Accordingly, Figures 3A to 3F show several embodiments of a cooling system 215 that may be used to cool the shaft 200, including flowing a fluid to the outside of the shaft 200 by means of gas cooling (Figure 3C) or cooling tubes (Figures 3D to 3E), and flowing a cooling fluid through the inside of the shaft 200 using channels within the shaft 200 (Figures 3A to 3B) and the attachment of a cooling plate 330 fixed to the proximal end of the shaft 200 (Figure 3F). Note that in each of these embodiments, the means for cooling are placed in an atmospheric environment.

[0045] However, other techniques may also be used to cool the shaft 200. For example, the shaft 200 can also be cooled using thermoelectric cooling, such as the use of a heat pump 350, which may be a Peltier heat pump, as shown in Figure 3G. In some embodiments, the heat pump 350 circles around the shaft 200. In other embodiments, the heat pump 350 is placed at various locations along the shaft 200. The heat pump 350 may be connected to a heat pump power supply 351 using wires 352. These wires 352 may be long enough to allow the heat pump 350 to move with the shaft 200. Thermoelectric cooling can be implemented around the shaft 200, at the proximal end of the shaft 200, at or near the target holder 190, or a combination thereof. In some embodiments, the use of a thermal siphon or heat pipe within or attached to the shaft 200 is used, along with a suitable combination of materials such as copper and water.

[0046] In some embodiments, cooling of the solid dopant material 195 is achieved by directly cooling the target holder 190. Figure 4 shows one such embodiment. In this embodiment, conduits 304, 305 pass through the vacuum seal 197 and are located within the cavity 196. These conduits 304, 305 bring the cooling fluid directly to the target holder 190. Channels may be present within the target holder 190 that allow the cooling fluid to pass through its interior. In certain embodiments, bellows 370 can be used to isolate the conduits 304, 305 from the conditions within the arc chamber 100.

[0047] In another embodiment, the heat pump 350 in Figure 3G is placed on or near the target holder. When the heat pump 350 is placed near the target holder 190, it should be noted that the wire 352 passes through the vacuum seal 197 and enters the cavity 196. The amount of wire 352 placed in the cavity 196 can be such that the wire 352 is fixed in place by the vacuum seal 197 so that there is no relative movement between the wire 352 and the vacuum seal 197 even if the shaft 200 moves in parallel. As shown in Figure 4, a bellows 370 can be used to protect the wire 352. Alternatively, a protective covering (cladding) may be placed around the wire 352.

[0048] This embodiment simplifies the design of the shaft 200 by sacrificing the use of a flexible bellows to cool the target holder 190. The temperature control and other features of the design are the same as those described herein.

[0049] Therefore, in each of these embodiments, there is a cooling system 215 that functions to cool the solid dopant material 195. In some embodiments, this cooling system 215 is configured to cool the shaft 200, while in other embodiments, the cooling system 215 is configured to cool the target holder. However, in all embodiments, the solid dopant material is actively cooled by the cooling system 215.

[0050] In some embodiments, the amount of cooling provided to the shaft 200 and / or target holder 190 by the cooling system 215 may be predetermined or established based on one or more parameters. For example, in the embodiments shown in Figures 3A-3B and 4, the flow rate of the cooling fluid through the shaft 200 or target holder 190 may be fixed. In other embodiments, the flow rate may be set based on a desired temperature range of the solid dopant material 195, the power applied to the cathode 110, the magnetic field power, a desired beam current, and / or other parameters. In some embodiments, the speed of the fan 320 (see Figure 3C) or the flow of the cooling gas in the tube 340 (see Figure 3D) may be fixed. In other embodiments, the speed of the fan 320 or the flow of the cooling gas in the tube 340 may be set based on a desired temperature range of the solid dopant material 195, the power applied to the cathode 110, the magnetic field power, a desired beam current, and / or other parameters. Similarly, the flow rate of the cooling fluid passing through the cooling tube 360 ​​in Figure 3E and the cooling plate 330 in Figure 3F can be fixed or set based on a desired temperature range of the solid dopant material 195, the power applied to the cathode 110, the magnetic field power, a desired beam current, and / or other parameters. Likewise, the power applied to the heat pump 350 in Figure 3G can be controlled in the same manner.

[0051] However, in other embodiments, closed-loop control may be used. As described above, in some embodiments, there may be a thermocouple 198 in contact with the shaft 200 or the target holder 190. The output of this thermocouple 198 may be used by the controller 180 to control the speed of the fan 320, the flow of cooling gas in the tube 340, the flow rate of cooling fluid through the shaft 200 or the target holder 190, the flow rate of cooling fluid through the cooling tube 360 ​​or the cooling plate 330, or the power supplied to the heat pump 350 in order to achieve a desired temperature range for the solid dopant material 195.

[0052] The above disclosure describes the cooling of a target holder and / or shaft in an indirectly heated cathode ion source, but the disclosure is not limited to this embodiment. The cooling system 215 may also be used with other ion sources or plasma sources such as capacitively coupled plasma sources, inductively coupled plasma sources, Bernas sources, or other suitable sources.

[0053] Figure 5 shows an ion implantation apparatus that may utilize any of the ion sources described herein. The ion implantation apparatus includes an ion source 500, which may be any of the ion sources described above. As described above, in certain embodiments, the ion source 500 may be an IHC ion source. In other embodiments, the ion source 500 may be an RF ion source. In this embodiment, an RF antenna may be positioned in contact with a dielectric window. This dielectric window may include part or all of one of the chamber walls. The RF antenna may include a conductive material (such as copper). An RF power source is electrically connected to the RF antenna. The RF power source may supply an RF voltage to the RF antenna. The power supplied by the RF power source may be 0.1 kW to 10 kW and may be at any suitable frequency (such as 1 MHz to 100 MHz). Furthermore, the power supplied by the RF power source may be pulsed. Other embodiments are also possible. For example, plasma may be generated in various ways by a Vernus ion source, a capacitively coupled plasma (CCP) source, a microwave, or an ECR (electron cyclotron resonance) ion source, etc. This disclosure does not limit the manner in which plasma is generated.

[0054] One chamber wall (referred to as the extraction plate) includes an extraction opening. The extraction opening may be an opening through which ions 501 generated in the ion source chamber are extracted and directed toward the workpiece 590. The extraction opening can be any suitable shape. In certain embodiments, the extraction opening may be elliptical or rectangular.

[0055] The extraction optics system 510 is positioned near the outside of the extraction opening of the ion source 500. In certain embodiments, the extraction optics system 510 includes one or more electrodes. In certain embodiments, the extraction optics system 510 includes a suppression electrode 511 negatively biased to the plasma to attract ions through the extraction opening. The suppression electrode 511 may be electrically biased using a suppression power supply. The suppression electrode 511 may be biased to be more negative than the extraction plate of the ion source 500.

[0056] In some embodiments, the extraction optical system 510 includes a second electrode 512. The second electrode 512 may be located near the suppression electrode 511. The second electrode 512 may be electrically connected to a second electrode power supply. In other embodiments, the second electrode 512 may be electrically grounded so that the second electrode power supply is not used.

[0057] In other embodiments, the extraction optical system 510 may include more than two electrodes, such as three or four electrodes. In these embodiments, the electrodes may be functionally and structurally similar to those described above, but may be biased with different voltages.

[0058] Downstream of the extraction optical system 510 is a mass spectrometer 520. The mass spectrometer 520 uses a magnetic field to guide the path of the extracted ions 501. The magnetic field influences the ion's flight path according to its mass and charge. A mass-dissolving device 530 having a dissolution opening 531 is located at the output (or distal end) of the mass spectrometer 520. By appropriately selecting the magnetic field, only ions 501 with selected mass and charge are directed to pass through the dissolution opening 531. Other ions hit the walls of the mass-dissolving device 530 or the mass spectrometer 520 and do not proceed further into the system.

[0059] One or more beamline components may be located downstream of the mass-resolving device 530. For example, a collimator 540 may be located downstream of the mass-resolving device 530. The collimator 540 receives the extracted ions 501 that have passed through the resolving opening 531, generating a ribbon ion beam. This ribbon ion beam is formed by a plurality of parallel or nearly parallel beamlets. In other embodiments, the ion beam may be a spot beam. In this embodiment, an electrostatic scanner is used to move the spot beam in a first direction, as defined below.

[0060] Downstream of the collimator 540, an acceleration / deceleration stage 550 may be located. The acceleration / deceleration stage 550 may be an electrostatic filter. The electrostatic filter is a beamline lens component configured to independently control the deflection, deceleration, and focus of the ion beam. Downstream of the acceleration / deceleration stage 550, a workpiece holder 560 is located.

[0061] For example, a workpiece 590, which may be a silicon wafer, a silicon carbide wafer, or a gallium nitride wafer, is placed on a workpiece holder 560.

[0062] The embodiments described in this application may have numerous advantages. Aluminum has a melting point of about 660°C, which can be reached within the arc chamber 100. The temperature of the solid dopant material 195 can be controlled by actively cooling the shaft 200 and / or the target holder 190. In several simulations, the temperature of the solid dopant material reached a maximum temperature of less than 400°C with a plasma output of 800 W. This maximum temperature can be further reduced through the selection of the cooling system and shaft material. Thus, it is possible to insert the solid dopant material 195 into the arc chamber 100 and reduce or eliminate the possibility of melting through the use of active cooling.

[0063] This disclosure is not limited in scope by the specific embodiments described herein. In fact, a number of other embodiments and modifications to this disclosure will be obvious to those skilled in the art from the foregoing description and accompanying drawings, in addition to the embodiments of this disclosure described herein. Therefore, such other embodiments and modifications are intended to be included within the scope of this disclosure. Furthermore, while this disclosure is described herein in the context of a specific implementation in a specific environment for a specific purpose, a person skilled in the art will recognize that the usefulness of this disclosure is not limited to this context, and that it can be beneficially implemented in many environments for many purposes. Accordingly, the claims set forth below should be interpreted in light of the entire scope and essence of this disclosure as described herein.

Claims

1. An ion source for generating an ion beam, An arc chamber comprising a plurality of walls connecting a first end and a second end, A target holder that holds a solid dopant material, A shaft connected to the target holder and extending the target holder toward the arc chamber, A cooling system for actively cooling the solid dopant material and An ion source equipped with these features.

2. The ion source according to claim 1, wherein the cooling system actively cools the shaft.

3. The ion source according to claim 2, wherein the shaft is made of copper and at least a portion of the shaft is covered by a sheath made of a non-copper material.

4. The ion source according to claim 2, wherein the shaft is cooled using a cooling fluid.

5. The ion source according to claim 4, wherein the shaft includes a hollow cavity having an inlet channel and an outlet channel so that the cooling fluid flows through the inside of the shaft.

6. The ion source according to claim 5, wherein the partition is located within the hollow cavity and separates the inlet channel from the outlet channel.

7. The ion source according to claim 5, wherein the shaft includes two tubes, the hollow cavity defining the outer tube, the inner tube positioned within the outer tube and not extending to the distal end of the shaft, and the two tubes forming the inlet channel and the outlet channel.

8. The ion source according to claim 2, wherein the shaft is cooled by flowing a cooling gas to the outside of the shaft.

9. The ion source according to claim 2, further comprising a fluid cooler and a cooling tube in fluid communication, wherein the cooling tube is wrapped around a portion of the shaft.

10. The ion source according to claim 2, further comprising a cooling plate fixed to the proximal end of the shaft, wherein the cooling plate functions as a heat sink.

11. The ion source according to claim 10, wherein a channel is arranged within the cooling plate, and a cooling fluid flows through the cooling plate to maintain the cooling plate within a predetermined temperature range.

12. The ion source according to claim 1, wherein the shaft and / or target holder is actively cooled using a heat pump fixed thereto.

13. The ion source according to claim 1, wherein the target holder is actively cooled using a cooling fluid passing through the target holder.

14. An ion implantation device, An ion source that generates an ion beam, One or more beamline components that direct the ion beam toward the workpiece, The ion source is equipped with, An arc chamber comprising a plurality of walls connecting a first end and a second end, A target holder that holds a solid dopant material, A shaft connected to the target holder and extending the target holder toward the arc chamber, A cooling system for actively cooling the solid dopant material and An ion implantation device equipped with the following features.

15. A thermocouple for measuring the temperature of the solid dopant material, Controller and The ion implantation apparatus according to claim 14, further comprising the controller using information from the thermocouple to maintain the solid dopant material within a desired temperature range.

16. The ion implantation apparatus according to claim 15, wherein the controller actively cools the shaft in order to maintain the solid dopant material within the desired temperature range.

17. The ion implantation apparatus according to claim 15, wherein the shaft is cooled by a fluid passing through the inside of the shaft or a fluid passing through the outside of the shaft, and the controller controls the temperature of the solid dopant material by controlling the flow rate of the fluid.

18. The ion implantation apparatus according to claim 15, wherein the shaft is cooled by attaching a cooling plate to the proximal end of the shaft, and the controller controls the temperature of the solid dopant material by controlling the temperature of the cooling plate.

19. The ion implantation apparatus according to claim 15, wherein the shaft and / or target holder is cooled by mounting one or more heat pumps, and the controller controls the temperature of the solid dopant material by controlling the power supplied to the one or more heat pumps.

20. The ion implantation apparatus according to claim 15, wherein the target holder is cooled by a fluid passing through the inside of the target holder, and the controller controls the temperature of the solid dopant material by controlling the flow rate of the fluid.

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