Double-cathode temperature control multi-cathode ion source

Abstract

And an ion source having a thermionic emission cathode coupled to the plasma chamber and exposed to the plasma chamber environment. The first power source is coupled to a first filament associated with the thermionic emission cathode and is configured to selectively supply a first power to the first filament to heat the first filament to a first temperature and induce thermionic emission from the thermionic emission cathode. A non-thermal electron emission cathode is coupled to the plasma chamber and exposed to the plasma chamber environment. A second power source supplies a second power to a second filament associated with the non-thermal electron emission cathode and heats the second filament and the non-thermal electron emission cathode to a second temperature while not inducing thermal electron emission from the non-thermal electron emission cathode, thereby minimizing condensation within the plasma chamber environment. The controller may control the first power source and the second power source to provide constant power or emission.

Description

[0001] Cross-reference to related applications This application claims the benefit of U.S. Provisional Application No. 63 / 581,160, filed on September 7, 2023, entitled “Dual-Cathode Temperature-Controlled Multi-Cathode Ion Source,” the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present invention relates generally to ion implantation systems, and more specifically to an improved ion source having multiple cathodes that control the temperature of the ion source to improve its lifetime, stability and operation. Background Technology

[0003] In semiconductor device manufacturing, ion implantation is used to dope semiconductors with impurities. Ion implantation systems are used to dope a workpiece (e.g., a semiconductor wafer) with ions from an ion beam to produce n-type or p-type material doping, or to form a passivation layer during integrated circuit manufacturing. This beam treatment is typically used to selectively implant impurities containing specified dopant materials into a wafer at predetermined energy levels and controlled concentrations to produce semiconductor materials during integrated circuit manufacturing. When used to dope semiconductor wafers, the ion implantation system implants selected ion species into the workpiece to produce the desired intrinsic material. For example, implanting ions from source materials such as antimony, arsenic, or phosphorus results in "n-type" intrinsic material wafers, while "p-type" intrinsic material wafers are typically generated from ions from source materials such as boron, gallium, or indium.

[0004] A typical ion implanter includes an ion source, an ion extraction unit, a mass analysis unit, a beam delivery unit, and a wafer processing unit. The ion source generates ions of the desired atomic or molecular dopant species. These ions are extracted from the ion source by an extraction system (typically a set of electrodes) that excites and directs the ion stream from the source, forming an ion beam. In the mass analysis unit, the desired ions are separated from the ion beam, typically by mass dispersion or separation of the extracted ion beam using magnetic dipoles. The beam delivery unit is typically a vacuum system containing a series of focusing devices that transports the ion beam to the wafer processing unit while maintaining the desired characteristics of the ion beam. Finally, the semiconductor wafer is moved into or out of the wafer processing unit via a wafer handling system (which may include one or more robotic arms) to place the wafer to be processed in front of the ion beam and remove the processed wafer from the ion implanter.

[0005] An ion source (commonly referred to as an arc discharge ion source) may include a heated filament cathode for generating ions that are shaped into a suitable ion beam for wafer processing. An example of such an ion source is provided in U.S. Patent No. 5,497,006 to Sferlazzo et al., wherein the ion source has a cathode supported by a base and positioned relative to a gas confinement chamber for generating high-energy electrons that induce ion generation within the gas confinement chamber. The cathode of Sferlazzo et al. is a tubular conductor with an end cap that extends partially into the gas confinement chamber. Summary of the Invention

[0006] Therefore, this disclosure provides systems and apparatus for increasing the productivity of ion sources in ion implantation systems. A simplified overview of this disclosure is thus given below to provide a basic understanding of some aspects of the invention. This overview is not a broad summary of the invention. It is neither intended to identify key or essential elements of the invention nor to depict its scope. Its purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that follows.

[0007] According to one exemplary aspect of this disclosure, an ion source is provided, wherein the ion source includes a plasma chamber defining a plasma chamber environment therein. A thermionic emission cathode, also referred to as a main cathode, is operatively coupled to the plasma chamber, thereby exposing at least a first portion of the thermionic emission cathode to the plasma chamber environment. For example, a first filament is associated with the thermionic emission cathode, and a first power source is electrically coupled to the first filament and configured to selectively supply a first power to the first filament, thereby selectively heating the first filament to a first temperature and inducing thermionic emission from the thermionic emission cathode.

[0008] For example, the secondary cathode is further operatively coupled to the plasma chamber, thereby exposing at least a second portion of the secondary cathode to the plasma chamber environment. For example, a second filament is associated with the secondary cathode, and a second power source is electrically coupled to the second filament. The second power source is, for example, configured to selectively supply a second power to the second filament, thereby selectively heating the second filament to a second temperature and heating the secondary cathode, while not inducing thermionic emission from the secondary cathode.

[0009] In one example, a controller is provided, wherein the controller has a circuit system configured to selectively supply a first power to a first filament and a second power to a second filament, thereby controlling one or more plasma conditions of the plasma within a plasma chamber environment. A feedback device may be further operatively coupled to the controller, wherein control of the first and second power is based on feedback from the feedback device. For example, the feedback device may include one or more of a first power source and a second power source, wherein the feedback device includes one or more of a voltage and a current, respectively provided by the first and second power sources. The feedback may be further associated with one or more plasma conditions of the plasma. For example, the feedback device may include a temperature sensor associated with an ion source.

[0010] In one example, the secondary cathode is configured to maintain a plasma chamber temperature confined within the plasma chamber to minimize condensation within the plasma chamber.

[0011] In another example, the controller may be configured to selectively vary a first power and a second power within a predetermined range, thereby providing control over the arc current within the plasma chamber, which is independent of the total power supplied to the thermionic emission cathode and the secondary cathode. The controller may be configured to selectively vary the first power and the second power to provide substantially constant plasma conditions. These substantially constant plasma conditions may include a maximum arc current when the first power is maximized and the second power is minimized. In another example, these substantially constant plasma conditions include a minimum arc current when the first power equals the second power.

[0012] According to another example, an ion source is provided comprising a plasma chamber and both a thermionic emission cathode and a secondary cathode operably coupled to the plasma chamber. A power source is operably coupled to the thermionic emission cathode and the secondary cathode and configured to selectively power the thermionic emission cathode to form a plasma, and selectively power the secondary cathode while forming the plasma, thereby heating the plasma chamber and minimizing condensation within the plasma chamber. A first filament and a second filament may be associated with the thermionic emission cathode and the secondary cathode, respectively.

[0013] For example, the power source may be configured to selectively provide a first power to a first filament, wherein the first power heats the first filament to a first temperature and induces thermionic emission from the thermionic emission cathode. The power source may be further configured to provide a second power to a second filament, wherein the second power selectively heats the second filament to a second temperature and heats the secondary cathode, while not inducing thermionic emission from the secondary cathode.

[0014] According to yet another example, an ion source is provided, comprising an operably coupled plasma chamber, a first thermionic emission cathode, and a second thermionic emission cathode coupled to the plasma chamber. One or more power sources are operably coupled to the first and second thermionic emission cathodes, respectively, wherein the one or more power sources are configured to selectively excite the first thermionic emission cathode to selectively form a plasma. The one or more power sources are further configured to selectively excite the second thermionic emission cathode to selectively heat the plasma chamber while forming the plasma, thereby minimizing condensation within the plasma chamber.

[0015] The one or more power sources may be configured to supply a first power to a first filament to selectively heat the first filament to a first temperature to induce thermionic emission from a first thermionic emission cathode, and the one or more power sources may be further configured to supply a second power to a second filament to selectively heat the second filament to a second temperature to induce thermionic emission from a second thermionic emission cathode, thereby selectively controlling the arc current of the plasma in the plasma chamber within a predetermined range by controlling the first power and the second power.

[0016] The controller can be configured to selectively control the emission current associated with one or more of the first and second thermionic emission cathodes at a constant power in a first mode. The controller can be further configured to control the first and second power associated with the first and second thermionic emission cathodes at a constant emission current in a second mode.

[0017] To achieve the foregoing and related objectives, this disclosure includes the features fully described below and particularly pointed out in the claims. The following description and drawings illustrate certain illustrative embodiments of the invention in detail. However, these embodiments indicate several of a variety of ways in which the principles of the invention can be employed. Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. Attached Figure Description

[0018] Figures 1A to 1B A cross-sectional view of an exemplary indirect heating ion source having one or more indirect heating cathodes is shown.

[0019] Figure 2 This is a block diagram of an ion source according to several exemplary aspects of this disclosure.

[0020] Figure 3 It is a graph showing the relationship between the arc current and the power supplied to the cathode according to various exemplary aspects of this disclosure.

[0021] Figure 4This is a graph illustrating examples of the effect of forming a phosphorus beam on the tuning stability of a boron ion beam in various configurations of an ion source according to various exemplary aspects of this disclosure.

[0022] Figure 5 This is a graph of a model of a dual-cathode system driven by constant heating power according to various exemplary aspects of this disclosure; Figure 6 This is a schematic diagram of an exemplary ion implantation system according to various aspects of this disclosure.

[0023] Figure 7 It is a graph of the emission current and power of the first thermionic heated cathode according to various aspects of this disclosure.

[0024] Figure 8 It is a graph of the emission current and power of the first thermionic heating cathode and the secondary cathode according to various aspects of this disclosure.

[0025] Figure 9 It is a graph showing the emission current and power of the first and second thermionic heated cathodes according to various aspects of this disclosure.

[0026] Figure 10 The graphs are based on various aspects of this disclosure and show the adjustable regions of the first and second thermionic heated cathodes. Detailed Implementation

[0027] This disclosure generally relates to an ion implantation system and an associated ion source. More specifically, this disclosure provides a configuration of an ion source having multiple cathodes to provide control over the associated temperature, emission current, and power. This disclosure relates to components for the ion implantation system that improve the lifetime, stability, and operation of the ion implantation system.

[0028] Therefore, the invention will now be described with reference to the accompanying drawings, wherein like reference numerals may be used throughout to refer to like elements. It should be understood that these descriptions are merely illustrative and should not be construed as limiting. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without these specific details. Furthermore, the scope of the invention is not intended to be limited to the embodiments or examples described below with reference to the accompanying drawings, but is intended to be limited only to the appended claims and their equivalents.

[0029] It should be noted that the accompanying drawings are provided to illustrate some aspects of embodiments of this disclosure, and therefore the drawings are to be considered illustrative only. In particular, the elements shown in the drawings are not necessarily drawn to scale, and the placement of various elements in the drawings is chosen to provide a clear understanding of the respective embodiments and should not be construed as a representation of the actual relative positions of various components in an embodiment according to the invention. Furthermore, features of the various embodiments and examples described herein can be combined with each other unless otherwise specifically stated.

[0030] It should also be understood that, in the following description, any direct connection or coupling between functional blocks, devices, components, elements, or other physical or functional units shown in the figures or described herein may also be achieved through indirect connection or coupling. Furthermore, it should be understood that functional blocks or units shown in the figures may be implemented as separate features in one embodiment, and may also, or alternatively, be implemented wholly or partially in a common feature in another embodiment.

[0031] Figure 1A A cross-section of the ion source 6A used in the ion implantation system is shown. Figure 1B A cross-section of another ion source 6B used in the ion implantation system is shown. A source material supply source 8 provides source material in the gas phase to the arc chamber 10. The filament 12 is resistively heated to a temperature at which thermionic emission occurs. The voltage between the filament 12 and the cathode 14 (the so-called "cathode voltage") accelerates electrons emitted from the filament toward the cathode until the cathode itself thermally emits electrons. This emission scheme is known in the industry as an indirectly heated cathode (IHC). For example, the cathode 14 serves two purposes: it protects the filament 12 from plasma ion bombardment, and it provides electrons for subsequent ionization.

[0032] The cathode 14 is negatively biased relative to the arc chamber 16, residing in the arc chamber as the so-called "arc voltage," and accelerating the emitted electrons toward the center 18 of the arc chamber. A feed gas (not shown) flows into the arc chamber 16, and the emitted electrons subsequently ionize the feed gas, thereby forming a plasma (not shown), from which ions can be extracted via the extraction port 20 or within the arc chamber. Figure 1A The repulsive pole 22, for example, further charges to the negative floating potential of the plasma and repels electrons back into the plasma, thereby increasing the electron mean free path, resulting in enhanced ionization and a denser plasma. Figure 1B In the middle, a second cathode 25 is installed to replace the repeller 22. Parallel to the... Figure 1A Cathode 14 and repulsion electrode 22 or Figure 1BThe magnetic field (not shown) of the central axis 24 defined by the second cathode 25 typically restricts the emitted and repelled electrons to define a so-called "plasma column," thus further improving ionization and plasma density.

[0033] Even if all other failure modes are avoided, the ion source will eventually fail due to sputtering and breakdown of the cathode 14. Breakdown occurs when the cathode material of wall 26 is sufficiently eroded to form a hole, thus exposing the filament 12 to the plasma. The filament 12 typically fails within hours of breakdown. The lifespan of the cathode can be extended by adding more material to the cathode 14. However, the amount of material that can be added to the cathode 14 is limited by the power available for heating the cathode, radiation losses, and the structure of the ion source (e.g., the structure of wall 26 and extraction orifice 20).

[0034] This disclosure recognizes that multi-cathode ion sources can improve ion source lifespan, whereby one or more secondary cathodes can delay ion source failure caused by sputtering erosion of the primary cathode. Further, auxiliary heaters positioned around the arc chamber can be provided to operate the ion source at higher temperatures, thereby reducing material condensation in the arc chamber and allowing for faster transitions between ion species. However, it should also be understood that variations in power dissipation in the ion source can also lead to workpiece scrap due to thermal drift in the ion source and extraction system.

[0035] Therefore, this disclosure provides, for example, independent control of the heating power and arc current generated separately by the multiple cathodes in a multi-cathode ion source, thereby allowing the heating power supplied to the multi-cathode ion source to be controlled independently of the electron current supplied to the plasma by the multiple cathodes. Thus, the arc current and plasma density can be varied or otherwise controlled while providing a substantially constant heating power to the multi-cathode ion source. Alternatively, the substantially constant arc current can be maintained while varying the heating power of the multiple cathodes, thereby varying the temperature of the multi-cathode ion source while maintaining its desired output.

[0036] In addition to providing a constant heating power or a constant arc current to multiple cathodes, this disclosure also envisions, for example, utilizing one or more variable heating power and arc current profiles. In another example, a first cathode may be configured individually or primarily to control the arc current, while a second cathode may be primarily configured to maintain a predetermined total heating power.

[0037] Figure 2An example of an ion source 100 (e.g., a multi-cathode ion source) in one embodiment of this disclosure is shown, the ion source 100 including a first cathode 102 (e.g., a thermionic emission cathode, also referred to as a main cathode) and one or more second cathodes 104. It should be understood that the one or more second cathodes (e.g., one or more secondary cathodes) may be configured as thermionic emission or non-thermal emission cathodes. For example, the one or more second cathodes 104 may include one or more cathodes associated with one or more sidewalls 106 of the ion source 100. Figure 2 Any one of one or more second cathodes 104 can, for example, be in a similar manner to Figure 1B The second cathode 25 is arranged relative to the ion source 100. The first cathode 102 is positioned, for example, in front of the first filament 108, whereby the power supply 110 is configured to selectively apply a first voltage 112 between the first filament and the second cathode to guide and accelerate electrons from the first filament to the first cathode, thereby heating the first cathode. One or more of the first cathode 102 and one or more of the second cathodes 104 comprise refractory material.

[0038] It should be understood that the first cathode 102 and one or more second cathodes 104 may have similar or different geometries and may be made of similar or different materials having various emission characteristics associated therewith. For example, the first cathode 102 may be made of a first material, and one or more second cathodes 104 may be made of one or more second materials, whereby the first cathode is configured to initiate thermionic emission at a power different from that at which the one or more second cathodes initiate thermionic emission.

[0039] One or more second cathodes 104 may be further positioned, for example, in front of one or more second filaments 114. Thus, the power supply 110 may be further configured, for example, to selectively apply a second voltage 116 between the respective second filaments and second cathodes, so as to guide and accelerate electrons from the second filaments to the second cathodes, thereby heating the respective second cathodes. It should also be noted that the power supply 110 may be configured as any number of individual or collective power supplies, configured to selectively supply any amount of power, current, or voltage to any one of the first filament 108, the first cathode 102, one or more second filaments 114, and one or more second cathodes 104.

[0040] When the first cathode reaches the predetermined temperature, electrons emit current. j Thermionic electrons are emitted into plasma chamber 118 (e.g., an arc chamber), where they collide with gas molecules within the plasma chamber to form plasma 120. For example, the emission current from the first cathode 102... jThe measured current is the arc current. Although not explicitly stated, it should be understood that the power supply 110 may be further configured, for example, to supply arc current to any one of the first cathode 102, one or more second cathodes 104, and plasma chamber 118.

[0041] Emission current from the first cathode j It is a strong function of temperature T, and its form is: (1), Where A is a constant related to the fundamental physical constants and the area of ​​the first cathode, and K is the Boltzmann constant. Φ Let be the work function of the first cathode. In one example, the first cathode 102 is composed of tungsten, whereby thermionic emission from the first cathode occurs at temperatures greater than approximately 2300 K. For example, Figure 3 A graph 150 shows the arc current relative to the power input to the first cathode 102 within a limited range of heating power. As shown, for typical cathode geometry and mass, the heating power can be transmitted through the first cathode 102 within... Figure 2 The ion is dissipated in the ion source 100, and essentially no emission occurs. For example, a controller 151 may be provided to provide control over the power supply 110 and corresponding control over the first cathode 102 and the second cathode 104.

[0042] For example, when multiple purification formulations are used to vary between arsenic (As) and boron (B) plasmas for injection, the heating power can be dissipated in the ion source 100 for the arsenic and boron plasmas. For example, the multiple purification formulations include low-power, medium-power, and high-power formulations, thereby the heating power difference between the highest and lowest power can be as high as several hundred watts.

[0043] In another example, each formulation can operate at the highest heating power and different emission currents without interfering with plasma conditions, thereby enabling... Figure 2 The condensation within the plasma chamber 118 of the ion source 100 is minimized or eliminated. In one example, feedback for controlling plasma conditions may be obtained directly from a power supply 110 supplying power to each of the first cathode 102 and the second cathode 104 (e.g., voltage and current reported by the power supply). In another example, closed-loop feedback for controlling plasma conditions may be obtained via a temperature sensor 152 associated with the ion source 100. For example, the temperature sensor 150 may be thermally coupled to, located on, or within the plasma chamber 118, and configured to measure the plasma chamber temperature on or within the plasma chamber 118.

[0044] Multiple cathodes (such as a first cathode 102 and one or more second cathodes 104) may include, for example, one or more thermionic emission cathodes and one or more non-thermal electron emission cathodes. For example, multiple cathodes may include four cathodes, whereby up to three cathodes include non-thermal electron emission cathodes configured to heat the ion source, thereby minimizing condensation.

[0045] In another example, the ion source 100 includes a source body 154 associated with a plasma chamber 118, whereby the source body is thermally stable. For example, the source body 154 includes the plasma chamber 118 and a cooling device 156 operatively coupled to the plasma chamber. The cooling device 156 includes, for example, a cooling plate 158 operatively coupled to the plasma chamber 118, wherein the cooling plate includes one or more cooling channels 160 defined therein. The cooling device 156 further includes a cooling fluid source 162 in fluid communication with the one or more cooling channels 160 of the cooling plate 158, whereby a pump 164 is configured to pump or flow cooling fluid (e.g., water) from the cooling fluid source 162 through the one or more cooling channels 160 defined in the cooling plate 158. Thus, the cooling plate 158 provides thermal stability to the plasma chamber 118, whereby the thermally stable source body 154 allows for lower tolerances in the control of the heating power of one or more second cathodes 104.

[0046] Figure 4 Example graph 170 is shown, illustrating various effects on the tuning stability of the boron (B+) ion beam in the ion source after the formation of a phosphorus (P+) ion beam in multiple configurations of the ion source. For example, various tuning cup current measurements during tuning of various boron ion beams after the formation of a phosphorus ion beam in ion sources having first and second configurations are shown. In the first configuration of the ion source, a first cathode including a thermionic emission cathode and a second cathode including a non-thermionic emission cathode are provided, whereby both the first and second cathodes are powered during the formation of the phosphorus ion beam, thereby supplementing the heating of the ion source in the manner described above. In the second configuration of the ion source, the second cathode is not powered during the formation of the phosphorus ion beam, thereby not providing supplemental heat to the ion source during the formation of the phosphorus ion beam.

[0047] The first tuning cup measurement 172 and the second tuning cup measurement 174 show the current measured at the tuning cup during tuning of the ion source in the first configuration. The third tuning cup measurement 176 shows the current measured at the tuning cup during tuning of the ion source in the second configuration. For example, the first tuning cup measurement 172 and the second tuning cup measurement 174 clearly show the higher stability of the tuning current when the second cathode is powered in the second configuration, while the third tuning cup measurement 176 shows greater instability when the second cathode is not powered, thus not providing supplemental heating.

[0048] This disclosure further illustrates that electron emission is a strongly nonlinear function of the heating power delivered to the cathode (e.g., and the heating power delivered to the ion source). Thus, changing the arc current while maintaining a constant heating power can be achieved by altering or otherwise controlling the heating ratio supplied to each cathode in a multi-cathode arrangement, as described above.

[0049] Figure 5 For example, graph 180 shows a model of a dual-cathode system driven by a constant heating power of 1100W. Therefore, Figure 5 The total electron emission current 182 in the model shown (e.g., equal to the arc current) can be varied between approximately 1.5A and 8.5A to provide a constant total power by varying or otherwise controlling the power distribution between the thermionic emission cathode and the non-thermal electron emission cathode. For example, the maximum arc current (shown by line 184) can be achieved when all power is delivered to a single cathode, while the minimum arc current (shown by line 186) can be achieved when the power is evenly distributed between the thermionic emission cathode and the non-thermal electron emission cathode.

[0050] One or more systems, apparatuses and / or methods disclosed herein may be practiced or otherwise implemented, for example, in association with an ion implantation system. Figure 6 For example, an ion implantation system 200 is shown, which includes an ion source 202 for generating an ion beam 204 along a beam path 206. A beamline assembly 210 is disposed downstream of the ion source 202 to receive the beam therefrom. The beamline assembly 210 may include (not shown) a mass analyzer, an acceleration structure (which may include, for example, one or more gaps), and an angular energy filter. The mass analyzer includes field generating components (e.g., a magnet) and operates to provide a field across the beam path 206 to deflect ions from the ion beam 204 in varying trajectories according to mass (e.g., mass-to-charge ratio). Ions traveling through the magnetic field are subjected to a force that guides individual ions with desired masses along the beam path 206 and deflects ions with undesirable masses away from the beam path.

[0051] A processing chamber 212 is disposed within the ion implantation system 200. This processing chamber includes a target location that receives an ion beam 204 from a beamline assembly 210 and supports one or more workpieces 214 (e.g., semiconductor wafers) along a beam path 206 for implantation using an ion beam that has undergone final quality analysis. The processing chamber 212 then receives the ion beam 204 directed toward the workpiece 214.

[0052] Ion source 202 generates ion beam 204, for example, by ionizing source material (e.g., source gas) containing desired dopant elements within the ion source. Subsequently, the ionized source gas is extracted from ion source 202 in the form of ion beam 204.

[0053] This disclosure understands that emission from the thermionic cathode is essentially a nonlinear function of temperature, as provided in equation (1) above. The temperature of the thermionic cathode is also essentially a nonlinear function of the power supplied to the cathode, and a complex function based on the relative extent of reaction conduction and radiation losses. However, this disclosure understands that radiation dominates at the temperature at which emission occurs, and therefore, assuming T... P 0.25 This is acceptable, which means that the emission current j will change as follows: (2) 。

[0054] While the exact form of the transmit current / power curve is not of substantial importance, this disclosure understands that the nonlinear relationship between transmit current and power is of substantial importance.

[0055] For example, under the above rough assumptions, and using the typical dimensions of the tungsten cathode used in IHC, Figure 7 The diagram shows graph 300, from which graph 302 illustrates the relationship between emission current and power. For example, the emission current from the cathode determines the arc current in the ion source. However, the emission current and the arc current are not typically equal. For example, a higher emission current results in a denser plasma and a higher beam current. For example, the arc current can be set for a given process formulation, and thus the arc current can be further used as a feedback signal to control the cathode power.

[0056] For a single cathode operating under given source parameters, such as the arc current (which in turn determines the emission current), the power that needs to be supplied to the ion source is determined, and thus largely determines the temperature of the ion source (e.g., not limited to the cathode).

[0057] This disclosure recognizes that, for some species (e.g., carbon), operating the ion source at high temperatures may be advantageous to prevent or otherwise improve deposit formation, even if other more desirable plasma conditions may require lower arc currents, cathode power, and ion source temperatures. In other cases, temperature variations in the ion source (e.g., due to switching between various ion beams requiring different plasma conditions and power levels) can cause mechanical displacement within the ion source, resulting in excessively long switching times between different ion beams. One method, for example, to decouple source power and temperature from the arc current is to supply auxiliary heat via an external heater that may be located on the side of the plasma chamber.

[0058] In some examples, this disclosure envisions an ion source having two cathodes (e.g., a first cathode and a second cathode), wherein the second cathode is provided instead of a conventional repeller, which is typically positioned relative to the first cathode along the axis of the plasma chamber and aligned with the applied magnetic field. One motivation for providing two cathodes, for example, is to allow switching between the two cathodes, thereby switching erosion caused by ion sputtering from the plasma from one to the other, thus extending the lifetime of the ion source when erosion of one or more cathodes is the primary failure mechanism of the ion source. For example, in a strip injector, emission from the two cathodes (e.g., including emission from different lengths from the respective first and second cathodes) can produce more uniform ion emission along the length of the ion source.

[0059] This disclosure therefore recognizes that, for example, providing a second cathode allows for the decoupling of the arc current from the source power without the need for an external heater. As shown in curve 302, for example, a cathode supplied with less than about 300 W of power will not emit a considerable number of electrons. Thus, this disclosure envisions advantageously powering the second cathode and injecting up to 300 W of additional power into the ion source without harmfully altering the plasma conditions.

[0060] Therefore, as Figure 8 As shown in the diagram 400, this disclosure provides additional flexibility in the setup and operation of the ion source. For example, without heating, there is no decoupling of the arc current and power, and the ion source can only operate along the first curve 402 (e.g., line A-A'). For example, providing a second cathode (e.g., a non-emitting cathode) can define a second curve 404 (e.g., line B-B'). Thus, the ion source can now operate anywhere within a first region 406 (e.g., the shaded area between A-A' and B-B') between the first curve 402 and the second curve 404.

[0061] This disclosure envisions further increasing power by advantageously driving the second cathode into an emission state. Since the emission current is a superlinear function of power, halving the emission current would reduce the power by less than half. Therefore, if each of the two cathodes provides half the emission current, the source power is further increased. For example, Figure 9 Curve 500 is shown, which illustrates the first emitter current / source power current curve 502 for a single cathode (e.g., with also...). Figure 8 The first curve alignment is shown, and the second emitter current / source power curve 504 is used for the two cathodes, each of which provides half of the current.

[0062] For example, this disclosure envisions that by controlling the ratio of the emission current supplied by each of the at least two cathodes, the emission current / source power can be advantageously controlled selectively to provide a wide range of power in the region between the first emission current / source power curve 502 and the second emission current / source power curve 504. For example, as Figure 10 As shown, a graph 600 is provided, which illustrates a first region 406 and a second region 602 (e.g., the shaded area between B-B' and C'-C). Accordingly, an extended adjustable region 604 (e.g., the shaded area between A-A' and C'-C) is thus defined, where it can be seen that the extended adjustable region is larger than the single first region 406.

[0063] like Figure 10 As shown, vertical arrow 606, for example, represents a constant power operating mode (e.g., the first mode), whereby the emitter current can be controlled between 1 and 6 amps in this example while maintaining constant source power and temperature. For example, the constant power operating mode can be advantageous for improving switchover time. Horizontal arrow 608, for example, represents a constant emitter current operating mode over a wide power range (e.g., the second mode), which is advantageous for operating under hotter process formulations. For example, by dividing the emitter current between the two cathodes, additional process flexibility is provided in terms of the arc current / source power parameter. It should be noted that, for simplicity, Figures 8 to 10 An example is shown in which at least two cathodes are substantially identical. However, it should be understood that the at least two cathodes may differ in their structural geometry and / or material composition.

[0064] It should be noted that the assumption that plasma conditions remain unchanged when switching the emission current between the first and second cathodes relies on the first and second cathodes being positioned at opposite ends of the ion source chamber, such as... Figure 1B As shown in the diagram (e.g., the second cathode is positioned relative to the first cathode along a cathode / repellent axis defined in a single cathode ion source). For example, such an assumption may not hold for a cathode positioned along the side of the ion source. While a side cathode may emit electrons, it may not be able to couple effectively into the plasma, thus altering the plasma, for example, by changing the cathode power.

[0065] While the invention has been shown and described with respect to one or more specific embodiments, it should be noted that the above embodiments are merely examples of some embodiments of implementing the invention, and the application of the invention is not limited to these embodiments. In particular, with respect to the different functions performed by the components (assemblies, devices, circuits, etc.) described above, unless otherwise specified, the terminology used to describe these components (including references to "device") is intended to correspond to any component that performs the specified function of the described component (i.e., functionally equivalent), even if structurally not equivalent to the disclosed structure that performs the function described in the exemplary embodiments of the invention herein. Furthermore, while a particular feature of the invention may be disclosed only with respect to one of several embodiments, such a feature may be combined with one or more other features of other embodiments when it may be desirable and advantageous for any given or particular application. Therefore, the invention is not limited to the above-described embodiments, but is intended to be limited only by the appended claims and their equivalents.

Claims

1. An ion source, comprising: A plasma chamber, which defines the plasma chamber environment; A thermionic emission cathode operatively coupled to the plasma chamber, wherein at least a first portion of the thermionic emission cathode is exposed to the plasma chamber environment; A first filament, which is associated with the thermionic emission cathode; A first power source, electrically coupled to the first filament and configured to selectively supply a first power to the first filament, thereby selectively heating the first filament to a first temperature and inducing thermionic emission from the thermionic emission cathode; A nonthermal electron emission cathode, operatively coupled to the plasma chamber, wherein at least a second portion of the nonthermal electron emission cathode is exposed to the plasma chamber environment; The second filament is associated with the nonthermal electron emission cathode; and A second power source, electrically coupled to the second filament, is configured to selectively supply a second power to the second filament, thereby selectively heating the second filament to a second temperature and heating the non-thermal electron emission cathode, while not inducing thermionic emission from the non-thermal electron emission cathode.

2. The ion source of claim 1, further comprising a controller having a circuit system configured to selectively supply a first power to the first filament and selectively supply a second power to the second filament, thereby controlling one or more plasma conditions of the plasma within the plasma chamber environment.

3. The ion source of claim 2, further comprising a feedback device operatively coupled to the controller, wherein the first power and the second power are based on feedback from the feedback device.

4. The ion source according to claim 3, wherein, The feedback device includes one or more of the first power source and the second power source, wherein the feedback includes one or more of the voltage and current provided by one or more of the first power source and the second power source, respectively.

5. The ion source according to claim 4, wherein, The feedback is further associated with one or more plasma conditions of the plasma.

6. The ion source according to claim 3, wherein, The feedback device includes a temperature sensor associated with the ion source.

7. The ion source of claim 6, wherein the temperature sensor is configured to measure the plasma chamber temperature on or inside the plasma chamber.

8. The ion source of claim 1, further comprising a source body associated with the plasma chamber, wherein the source body includes a cooling device operatively coupled to the plasma chamber and configured to selectively cool the plasma chamber.

9. The ion source according to claim 8, wherein the cooling device comprises: A cooling plate operatively coupled to the plasma chamber, wherein the cooling plate includes one or more cooling channels defined therein; A cooling fluid source, which is in fluid communication with the one or more cooling channels; and A pump configured to pump cooling fluid from the cooling fluid source through the one or more cooling passages.

10. The ion source according to claim 1, comprising: Multiple non-thermal electron emission cathodes are operatively coupled to the plasma chamber; and A plurality of second filaments are associated with the plurality of non-thermal electron emission cathodes, and wherein the second power supply is electrically coupled to the plurality of second filaments.

11. The ion source according to claim 1, wherein, The thermionic emission cathode and the non-thermal electron emission cathode have similar dimensions.

12. The ion source according to claim 1, further comprising a repeller positioned substantially opposite the thermionic emission cathode within the plasma chamber.

13. The ion source according to claim 12, wherein, The nonthermal electron emission cathode is further positioned generally relative to the repeller within the plasma chamber.

14. The ion source according to claim 1, wherein, One or more of the thermionic emission cathode and the non-thermal electron emission cathode include refractory materials.

15. The ion source according to claim 1, wherein, The nonthermal electron emission cathode is configured to maintain a plasma chamber temperature limited within the plasma chamber to minimize condensation within the plasma chamber.

16. The ion source of claim 1, further comprising a controller configured to selectively change the first power and the second power within a predetermined range, thereby providing independent control of the arc current and power within the plasma chamber.

17. The ion source according to claim 16, wherein, The controller is configured to selectively change the first power and the second power to provide substantially constant plasma conditions.

18. The ion source according to claim 17, wherein, The essentially constant plasma conditions include the maximum arc current when the first power is maximized and the second power is minimized.

19. The ion source according to claim 18, wherein, The essentially constant plasma conditions include the minimum arc current when the first power equals the second power.

20. An ion source, comprising: Plasma chamber; A thermionic emission cathode, which is operatively coupled to the plasma chamber; A non-thermal electron emission cathode, which is operatively coupled to the plasma chamber; as well as A power source, operably coupled to the thermionic emission cathode and the non-thermal electron emission cathode, is configured to selectively supply power to the thermionic emission cathode to form a plasma, and selectively supply power to the non-thermal electron emission cathode while forming the plasma, thereby heating the plasma chamber and minimizing condensation within the plasma chamber.

21. The ion source according to claim 20, further comprising: A first filament, which is associated with the thermionic emission cathode, wherein the power supply is electrically coupled to the first filament; as well as A second filament is associated with the non-thermal electron emission cathode, wherein the power supply is electrically coupled to the second filament.

22. The ion source of claim 21, wherein the power source is configured to selectively provide a first power to the first filament, wherein the first power heats the first filament to a first temperature and induces thermionic emission from the thermionic emission cathode, and the power source is further configured to provide a second power to the second filament, wherein the second power selectively heats the second filament to a second temperature and heats the non-thermal electron emission cathode, while not inducing thermionic emission from the non-thermal electron emission cathode.

23. An ion source, comprising: Plasma chamber; A first thermionic emission cathode is operatively coupled to the plasma chamber; A second thermionic emission cathode is operatively coupled to the plasma chamber; and One or more power sources are operatively coupled to the first and second thermionic emission cathodes, respectively, wherein the one or more power sources are configured to selectively excite the first thermionic emission cathode to selectively form a plasma, and wherein the one or more power sources are further configured to selectively excite the second thermionic emission cathode to heat the plasma chamber while forming the plasma, thereby minimizing condensation within the plasma chamber.

24. The ion source according to claim 23, further comprising: A first filament electrically coupled to one or more power sources, wherein the first filament is associated with a first thermionic emission cathode; and A second filament electrically coupled to one or more of the power sources, wherein the second filament is associated with the second thermionic emission cathode.

25. The ion source according to claim 24, wherein, The one or more power sources are configured to supply a first power to the first filament to selectively heat the first filament to a first temperature to induce thermionic emission from the first thermionic emission cathode, and wherein the one or more power sources are further configured to supply a second power to the second filament to selectively heat the second filament to a second temperature to induce thermionic emission from the second thermionic emission cathode, thereby selectively controlling the plasma arc current in the plasma chamber within a predetermined range by controlling the first power and the second power.

26. The ion source of claim 25, further comprising a controller configured to selectively control, in a first mode, an emission current associated with one or more of the first and second thermionic emission cathodes at a constant power, wherein, The controller is configured to control, in a second mode, a first power and a second power associated with the first and second thermionic emission cathodes with a constant emission current.

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