Ion implantation system having a resonator, a linear accelerator configuration, and a rotary exciter

Abstract

An exciter for a high frequency resonator.SOLUTION: The exciter may include an exciter coil inner portion extending along an exciter axis and an exciter coil loop disposed at a distal end of the exciter coil inner portion. The exciter may further include a drive mechanism including at least a rotating component to rotate the exciter coil loop about the exciter axis.SELECTED DRAWING: FIGS. 1A-F

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority from U.S. Non-Provisional Patent Application No. 17 / 506,185, entitled "RESONATOR, LINEAR ACCELERATOR CONFIGURATION AND ION IMPLANTATION SYSTEM HAVING ROTATING EXCITER," filed October 20, 2021, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates generally to ion implanters, and more particularly to high energy beamline ion implanters. [Background technology]

[0003] Ion implantation is a process of introducing dopants or impurities into a substrate via ion bombardment. An ion implantation system may include an ion source and a series of beamline components. The ion source may include a chamber in which ions are generated. The ion source may further include a power supply and extraction electrode assembly disposed adjacent to the chamber. The beamline components may include, for example, a mass analyzer, a first acceleration or deceleration stage, a collimator, and a second acceleration or deceleration stage. Similar to a series of optical lenses for manipulating a light beam, the beamline components can filter, focus, and manipulate ions or ion beams having specific species, shapes, energies, and / or other properties. The ion beam may pass through the beamline components and be directed toward a substrate mounted on a platen or clamp.

[0004] Implanters capable of producing ion energies of about 1 MeV or greater are often referred to as high-energy ion implanters or high-energy ion implantation systems. One type of high-energy ion implanter uses a linear accelerator, or linac (LINAC), as the ion acceleration stage. In a linear accelerator, or linac (LINAC), a series of electrodes arranged as a tube conducts the ion beam, accelerating it to increasingly higher energies along the series of tubes. Here, the electrodes receive an RF voltage signal. Known (RF) LINACs are driven by RF voltages applied at frequencies between 13.56 MHz and 120 MHz.

[0005] In known LINACs (for simplicity, the term LINAC as used herein may refer to an RF linac that uses an RF signal to accelerate an ion beam), an ion beam may be accelerated through multiple acceleration stages to reach a target final energy (e.g., 1 MeV, several MeV, or higher). Each successive stage of the LINAC can receive an ion beam at increasingly higher energies and accelerate the ion beam to even higher energies. The acceleration stages of a given LINAC may employ a so-called double-gap configuration with one RF-driven electrode, or may employ a so-called triple-gap configuration with two RF-driven electrodes.

[0006] A given acceleration stage may further include a resonator for driving the RF electrodes with an RF voltage at a selected RF frequency. Known examples of resonator configurations include solenoidal resonators. A solenoidal resonator has a solenoid coil defining a generally circular cylindrical shape, surrounded by an electrically grounded cylindrical resonator can (RF enclosure). From an electromagnetic perspective, a resonator is an RLC oscillator circuit with the coil as the inductive element and the resonator can as the capacitive element. At resonance, energy is periodically converted from magnetic energy stored in the coil to electrostatic energy as a voltage difference between the driven RF electrodes. In such a solenoid configuration, an excitation coil is provided inside the resonator can, while a resonator coil is provided outside, generating an RF signal that is magnetically coupled to the resonator coil. Specifically, in a resonant RF cavity, RF energy is transferred from an RF generator to an RLC oscillator circuit. For a given input RF power, the higher the shunt impedance (Zsh) of the resonator, the higher the available accelerating voltage. The required RF energy is transferred from the RF generator to the RLC circuit by an RF exciter (exciter). In the operation of the resonant cavity, the exciter plays two roles: i) to match the output impedance of the RF generator (this impedance can be 50 Ω) and ii) to maximize the power transfer from the RF generator to the RLC circuit.

[0007] Recently, so-called toroidal resonators have been proposed for use in acceleration stages. In a toroidal resonator, the resonator coil defines a toroidal shape, and the surrounding can (cavity) has a cylindrical shape. This configuration allows for the generation of a closed magnetic field topology within the resonator. In this configuration, the magnetic field is generally contained within the loop of the resonator coil, which may require adjustments to the exciter placement compared to known solenoid designs.

[0008] It is with respect to these and other considerations that the present disclosure is offered. Summary of the Invention

[0009] An exciter for a radio frequency resonator is provided. The exciter may include an exciter coil inner portion extending along an exciter axis and an exciter coil loop disposed at a distal end of the exciter coil inner portion. The exciter may further include a drive mechanism including at least a rotation component for rotating the exciter coil loop about the exciter axis.

[0010] In another embodiment, a resonator for a linear accelerator is provided. The resonator may include a toroidal resonator coil defining a toroidal shape and an exciter at least partially disposed within the toroidal resonator coil. The exciter may include an exciter coil inner portion extending along an exciter axis and an exciter coil loop disposed at a distal end of the exciter coil inner portion. The exciter may further include a drive mechanism including at least a rotation component for rotating the exciter coil loop about the exciter axis.

[0011] In a further embodiment, a method of operating a linear accelerator is provided. The method may include delivering RF power to an exciter of an RF resonator in the linear accelerator, the RF resonator including a toroidal resonator coil and a resonator can, the exciter including an exciter loop disposed within the toroidal resonator coil. The method may further include conducting an ion beam through the linear accelerator and rotating the exciter loop while conducting the ion beam through the linear accelerator, wherein a power coupling between the exciter and the toroidal resonator coil is adjusted. [Brief explanation of the drawings]

[0012] [Figure 1A-F] 1 illustrates an exemplary apparatus according to an embodiment of the present disclosure. [Figure 2A] FIG. 1 is a detailed front view of one embodiment of a toroidal acceleration stage of a linear accelerator. [Figure 2B] The dependence of VSWR (voltage standing wave ratio) on excitation frequency is shown. [Figure 3A] FIG. 2 is a side view of a resonator according to an embodiment of the present disclosure. [Figure 3B]FIG. 2 is an end view of a resonator according to an embodiment of the present disclosure. [Figure 3C] FIG. 10 is a side view of another resonator according to another embodiment of the present disclosure. [Figure 4A-4B] 1 shows the electrical performance of the resonator as a function of the ratio of the exciter loop radius to the minor radius of the toroidal resonator coil. [Figures 5A-5C] 10A-10C illustrate end views of a resonator operated at various rotational orientations of the exciter loop according to an embodiment of the present disclosure for an embodiment of the resonator. [Figures 6A-6B] 1 shows structural details of one embodiment of a rotary exciter. [Figures 7A-7B] 10 illustrates the electrical behavior of a resonator as a function of the orientation angle of the exciter loop, according to an embodiment of the present disclosure. [Figure 8] 1 shows a schematic diagram of an ion implanter according to an embodiment of the present disclosure. [Figure 9] 1 illustrates an exemplary process flow. DETAILED DESCRIPTION OF THE INVENTION

[0013] The drawings are not necessarily to scale. The drawings are merely representational and are not intended to depict specific parameters of the present disclosure. The drawings are intended to illustrate exemplary embodiments of the present disclosure and therefore should not be considered limiting in scope. In the drawings, like numbers represent like elements.

[0014] Apparatus, systems, and methods according to the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the systems and methods are shown. The systems and methods may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Instead, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the systems and methods to those skilled in the art.

[0015] Terms such as "top," "bottom," "upper," "lower," "vertical," "horizontal," "lateral," and "longitudinal" may be used herein to describe the relative placement and orientation of these components and their constituent parts with respect to the geometry and orientation of the components of a semiconductor manufacturing device as seen in the drawings. Terms may include the specifically mentioned words, derivatives thereof, and words of similar import.

[0016] As used herein, elements or operations described in the singular following the words "one" or "an" are understood to also include a plurality of elements or operations. Furthermore, references to "one embodiment" of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0017] Provided herein are approaches for improved high-energy ion implantation systems and components based on a beamline architecture using RF resonators, specifically, linear accelerators. For simplicity, the ion implantation system may further be referred to herein as an "ion implanter." Various embodiments involve a novel approach that provides the ability to flexibly adjust the effective drift length within the acceleration stage of the linear accelerator.

[0018] FIGS. 1A through 1F show various views of an exemplary device referred to herein as exciter 10. Specifically, in addition to FIGS. 1A and 1B, which are discussed below, FIG. 1C shows a detail of a portion of exciter 10, FIG. 1D shows an end view of exciter 10, FIG. 1E shows a perspective view of exciter 10, and FIG. 1F shows a side view of exciter 10. The exciter 10 may be suitable for use in high-frequency resonators (excitation frequencies may range into the MHz range), such as the RF resonators of a LINAC. As shown in FIG. 1A, exciter 10 includes an exciter coil 12 formed of a suitable conductor, such as a highly conductive metal or metal alloy, as well as an exciter shaft 17. As detailed in FIG. 1B, exciter shaft 17 includes a powered leg, shown as exciter coil inner portion 14, an insulating sleeve 18, and a grounded leg, shown as conductive sleeve 20.

[0019] The exciter shaft 17 may extend along an exciter axis, which in this case is defined as being parallel to the Y-axis of the illustrated Cartesian coordinate system. The exciter coil 12 may further include an exciter loop 16 disposed at a distal end of the exciter coil inner portion 14. Thus, a portion of the exciter coil 12 is formed in the shaft 17, including the exciter coil inner portion 14 and the conductive sleeve 20, while a portion of the exciter coil (exciter coil loop 16) extends beyond the exciter shaft 17.

[0020] The exciter coil loop 16 may define a circular shape that lies in a given plane, e.g., the XY plane. As shown, a first end of the exciter coil loop 16 is connected to the distal end of the exciter coil inner portion 14, while a second end of the exciter coil loop 16 is connected to a conductive sleeve 20. This configuration allows the insulating sleeve 18 and the exciter coil inner portion to pass through a chamber wall 22. The chamber wall 22 may house the exciter coil 12 and associated hardware of the resonator.

[0021] As further shown in FIG. 1A , the exciter 10 may include a stage 24. This stage may incorporate a drive mechanism. The drive mechanism includes at least a rotation component (not shown separately) for rotating the exciter coil loop 16 about the exciter axis (Y-axis). In some embodiments, the drive mechanism of the stage 24 may further include a translation component (not shown separately) for moving the exciter coil loop 16 along a first direction parallel to the exciter axis, i.e., along the Y-axis. Thus, the orientation and position of the exciter coil loop 16 may be adjusted relative to the resonator coil within the housing that contains the exciter coil loop 16. The benefits of this adjustability are discussed further below.

[0022] 2A is a detailed front view of one embodiment of a linear accelerator acceleration stage 100. The acceleration stage 100 includes a drift tube assembly 102 and an associated resonator, shown as resonator 110, for accelerating an ion beam 104 in the linear accelerator. As shown in FIG. 8 , described below, the resonator 110 may be implemented in multiple acceleration stages of a linear accelerator 314 for accelerating an ion beam 306 in an ion implanter 300.

[0023] 2A, drift tube assembly 102 includes an upstream grounded drift tube and a downstream grounded drift tube, similarly labeled as grounded drift tube electrode 102B. Drift tube assembly 102 further includes a pair of RF drift tube electrodes separated by a gap, designated RF drift tube electrode 102A. RF drift tube electrode 102A and grounded drift tube electrode 102B collectively define a triple gap configuration.

[0024] The RF drift tube electrode 102A is driven by a resonator 110. The resonator 110 includes an RF enclosure 112 that houses a toroidal resonator coil, referred to as a toroidal coil 114. The toroidal coil 114 and similar resonator coils are described in more detail in later embodiments. Briefly, the excitation coil 112 may be arranged to receive RF power as part of an RF power supply assembly, shown as an RF circuit 124, including an RF generator 120 and an impedance element 122. Although not shown in the figures, the resonator 110, or similar resonators described below, may include a capacitive tuner. The capacitive tuner is positioned external to the toroidal coil 114 but within the resonator can (RF enclosure 112). In various non-limiting embodiments, the capacitive tuner may be movable in a manner to adjust the total capacitance of the RLC circuit formed by the toroidal coil 114 and the resonator can (RF enclosure 112).

[0025] 2A and the following figures, according to various non-limiting embodiments, resonator 110 and similar resonators can be applied to a triple-gap accelerator configuration. In addition to the novel configuration of exciter 10, these embodiments differ from known LINACs in that resonator 110, resonator 110A, and resonator 110B (which are shown in FIGS. 3A-C) supply voltage to drift tube assembly 102 via toroidal coil 114, as opposed to the solenoidal (or helical) coils of known triple-gap accelerator stages.

[0026] The exciter coil 12 and the toroidal coil 114, together with the RF enclosure 112, operate to generate an RF voltage at the RF drift tube electrode 102A. To determine the relationship between the input RF power and the voltage generated at the accelerating electrode (RF drift tube electrode 102A), the resonant cavity including the exciter coil 12, the toroidal coil 114, and the RF enclosure 112 is modeled as a lumped element circuit. Using Thévenin's theorem, the RF generator circuit and the resonator circuit can be transformed into a single circuit. The equivalent mutual impedance Z Mcan be written out as follows: Similarly, the equivalent RF voltage V M becomes: TIFF2026035587000003.tif20170where i 2 =-1, ω=2πf is the angular frequency, V0 and Z0 are the output voltage and impedance of the RF generator, and M is the mutual inductance of the excitation and resonator coils. As can be seen from equation (2), the power transfer efficiency (which scales with the square of the voltage) depends on the coupling between the coils, which is a function of the size, structure, physical spacing, relative position, and properties of the environment surrounding the coils. In its simplest form, the mutual inductance of two concentric coils is given by Maxwell's equations: TIFF2026035587000004.tif20170 and TIFF2026035587000005.tif20170Here, A and a are the radii of the circular coils, s is the distance between their centers, and F and E are the complete elliptic integrals of the first and second kind, respectively.

[0027] Because the coupling between the excitation coil and the resonator coil depends on the amount of magnetic flux linkage between them, for a given size of the resonator coil, there exists an optimal dimension of the excitation coil that maximizes the coupling effect. To cover a wide range of frequencies, the excitation coil has a high operating bandwidth. Therefore, according to an embodiment of the present disclosure, the excitation coil 12 is designed as a low-Q-factor coil, i.e., a low-inductance coil. Therefore, as shown in FIGS. 1A-1F, the excitation coil 12 may be designed as a one-loop circular coil with a radius r0. In particular, the exciter coil loop 16 may be formed of a conductive metal, such as silver-plated copper wire, with a diameter d. Similar to a coaxial cable, the conductive sleeve 20 provides a return path to ground and further shields the exciter coil inner portion 14 from RF interference. According to an embodiment of the present disclosure, the diameters of the excitation coil inner portion 14, the insulating sleeve 18, and the conductive sleeve 20 are selected so that the characteristic impedance of the excitation coil 12 matches the output impedance of the RF generator. So for an RF generator with an impedance of 50 ohms (the most common), the following applies: TIFF2026035587000006.tif20170Here, μ0 and ε0 represent the permeability and permittivity of free space, and ε r represents the relative permittivity of the insulating sleeve material. Depending on the geometry of the exciter, suitable materials can be selected for insulation (air (ε r =1), PTFE(ε r =2), quartz (ε r =3.7), alumina (ε r = 9.8), or other). Generally, in RF electronics, the efficiency of power transfer from a generator to a load is characterized by the voltage standing wave ratio (VSWR). This parameter is the ratio between the amplitude of the reflected voltage wave and the forward voltage wave. As shown in Figure 2B, VSWR is a sharp function of frequency and can be a value between 1 (perfect transmission) and ∞ (zero transmission). This parameter is related to power transfer. TIFF2026035587000007.tif20170 where Pr and Pf represent reflected power and forward power, respectively. In one embodiment, by properly designing the excitation coil, the VSWR can be minimized to a value approaching unity. In the case of Figure 2B, Equation 6 gives a VSWR of 1.08, but the value of the reflected power represents only 0.15% of the forward power.

[0028] While the exciter coil 12 can be used to drive a resonator coil of any shape, in this embodiment, such as FIG. 2A , the resonator coil is a toroidal resonator. Therefore, the magnetic flux 130 generated by, for example, the toroidal coil 114 is completely surrounded by the resonator coil. In other words, the magnetic flux is confined within the coil loop. Therefore, according to embodiments of the present disclosure, an excitation coil must be inserted between the loops of the toroidal resonator coil to power it and provide the necessary magnetic flux linkage between the magnetic flux generated by the excitation coil and the magnetic flux of the toroidal resonator coil. However, the toroidal resonator configuration benefits from the fact that the magnetic flux is contained within the toroidal coil 114. This geometry prevents magnetic field lines from leaking outside the toroidal coil 114, thereby reducing induced eddy currents within the resonator's RF enclosure 112. Fewer eddy currents results in a lower resistance in the RLC circuit and potentially higher shunt impedance.

[0029] To illustrate example configurations of excitation coil insertion within a resonator coil, FIGS. 3A, 3B, and 3C provide examples of two different resonators according to embodiments of the present disclosure. Specifically, FIGS. 3A and 3B show side and end views, respectively, of a resonator 110A according to one embodiment of the present disclosure, and FIG. 3C shows a side view of another resonator according to another embodiment of the present disclosure. Each of these resonators employs a toroidal coil. As used herein, the term "toroidal coil" may refer to two separate coils arranged relative to one another to define a toroidal shape, where the individual coils may form portions of the toroidal shape (e.g., similar halves of a toroid). As more clearly shown in FIG. 3B, the toroidal coil 114 includes multiple loops or turns. The toroidal coil 114 includes two coils arranged as two sections, each with N turns, and is constructed of a suitable conductor, such as silver-plated copper tubing. The turns on each half of the toroidal coil 114 are wound in the same direction, resulting in a 180° (out-of-phase) phase difference between the voltages on the powered drift tube. At the top of the toroidal coil 114, both ends of the toroidal coil 114 are extended a length 10 and passed through openings in the RF enclosure (not shown) to connect separately to the two separate powered RF drift tube electrodes (RF electrodes 102A) mentioned above. At the bottom, a loop of the toroidal coil 114 can be connected to the grounded enclosure wall (see chamber wall 22).

[0030] Turning first to FIG. 3 , a first insertion configuration is shown. The exciter coil 12 is inserted toward the bottom of the toroidal coil 114, with the loop centered on the azimuthal axis of the toroid and equidistant from the toroidal legs. In other words, the long axis of the exciter coil 12 extends along the Z-axis, which is perpendicular to the XY plane. Because the bottom leg of the toroidal coil is grounded, this configuration reduces the risk of arcing between the exciter coil 12 and the toroidal coil 114. Furthermore, the symmetrical placement of the exciter coil loops 16 can balance the voltages on the two halves of the toroidal coil 114. A disadvantage of this configuration is that a conductive sleeve 20 must be threaded through the loop of the toroidal coil 114 and connected to the grounded chamber wall 1. Although this configuration is functional, in this configuration, the exciter coil 12 (particularly the exciter coil inner portion 14) is relatively long to ensure that it is long enough to reach the chamber wall 22, which causes a voltage drop along the exciter coil 12 and therefore reduces the efficiency of power transfer.

[0031] A more advantageous insertion configuration for the exciter coil 12 is shown in Figures 3A and 3B. In this case, the exciter coil 12 is inserted at the bottom of the system between the legs of the toroidal coil 114. The center of the exciter coil loop 16 is aligned with the azimuthal axis of the toroid (meaning a circle on the toroid's Oyz symmetry plane, with a radius equal to the semimajor axis of the torus (RMajor)). The conductive sleeve 20 is electrically connected to the grounded pedestal of the toroidal coil 114. This configuration shortens the return path to ground while maintaining low arcing risk and balanced voltage. As a result, the voltage drop across the exciter 10 is reduced, which leads to improved power transfer efficiency.

[0032] It has been shown that in the ideal case (no losses), magnetic energy is converted completely into electrostatic energy, resulting in a 1:1 energy conversion from the toroidal coil 114 (magnetic energy) to the accelerating ions (kinetic energy). However, in practical systems, there are losses that limit this energy conversion. In this case, the energy transfer is quantified by the shunt impedance (Zsh) of the resonator. For the same amount of input power, Z sh The higher the voltage generated at the accelerating electrode, the higher the Z. sh corresponds to the inductance of the coil, 3 / 2 The larger L is, the greater Z sh On the other hand, since the cavity forms an RLC circuit, the circuit oscillates at a specific frequency. The frequency at resonance is TIFF2026035587000008.tif20170, where L is the inductance of the coil and C is the capacitance of the system.

[0033] Therefore, the coil-can (enclosure) resonator system should have the highest possible shunt impedance (Z sh) while simultaneously having a natural resonant frequency (f0) as close as possible to the desired operating RF frequency (e.g., 13.56 MHz and 27.12 MHz). As mentioned above, slight deviations of the resonant frequency from the operating frequency can be corrected with a capacitive tuning component (here, one possible position of the capacitive tuning component 140 is shown by the dashed line). As shown in equations (3) and (4), mutual coupling depends on the size and relative position of the coils. Therefore, for a given resonator coil geometry, there will be an optimal size of the inductive RF exciter (meaning the diameter of the exciter coil loop 16). The electrical behavior induced by sets of exciter coils with the same characteristic impedance (Zch) but different loop radii was modeled for the same resonator coil. As can be seen in Figures 4A and 4B, HFSS (High Frequency Simulation Software) modeling results indicate that the optimal ratio of the excitation loop radius to the toroidal minor radius for maximum power transfer corresponds to a value of approximately 0.25. At this ratio, the VSWR is approximately 1.1 (corresponding to 99.7% transferred power) and the voltage at the powered slit is 2.25 kV for 100 W input power in the exciter 10. As mentioned above, in order to achieve maximum power transfer and maximum voltage conversion for a normally operating, energized slit, the resonant frequency of the system must match the frequency of the RF generator.

[0034] According to embodiments of the present disclosure, the resonator can be initially tuned for resonance in the absence of an ion beam. During operation, thermal effects can cause the resonator frequency to deviate from its design value, necessitating manipulation to return the resonator to the resonance value. This return to resonance can be achieved, for example, using a tuning system including an adjustable capacitor. However, the presence of a beam also changes the load impedance of the resonator due to the electrical resistance introduced by the beam. This change in impedance affects the power coupling, leading to a suboptimal coupling of the exciter loop to the resonator coil. According to embodiments of the present disclosure, the coupling of the exciter 10 to the toroidal coil 114 can be adjusted by providing a movement mechanism for the exciter 10 (e.g., the drive mechanism of the stage 24), as described above. In other words, by rotating the exciter coil loop 16 about the Oy axis, the coupling can be easily changed, thereby exposing more or less of the “effective” surface area, which maximizes the magnetic flux linkage between the exciter 10 and the toroidal coil 114.

[0035] 5A, 5B, and 5C show end views of a resonator operated at various rotational orientations of the exciter loop according to embodiments of the present disclosure for an embodiment of the resonator, specifically, in which the angle between the normal to the exciter loop surface and the tangent to the toroidal azimuthal axis varies from 0° to 15° to 30°, respectively.

[0036] 6A and 6B show the structural details of one embodiment of a rotary exciter. The toroidal coil post 111 is hollow and has a concentric cylindrical bore with a diameter slightly larger than that of the conductive sleeve 20. This concentric cylindrical bore extends from the leg of the toroidal coil to the chamber wall. The exciter shaft 17 (conductive sleeve 20, insulating sleeve 18, and exciter coil inner portion 14) is threaded through the post cylindrical bore and is free to rotate. At the bottom of the post, the insulating sleeve 18 and the feed leg of the exciter coil 12 (exciter coil inner portion 14) pass through the chamber wall (not shown separately) and further to the step 24. This configuration ensures dynamic connection to the RF generator 120 using a spring-loaded electrical connection. The ground connection between the conductive sleeve 20 and the toroidal coil post 111 is ensured by a connecting ring 116. This ring can be fastened to the conductive sleeve 20 with side screws or the like and has a diameter slightly larger than the post bore. In this way, the connecting ring 116 is located on top of the toroidal coil post 111, ensuring an electrical path to ground. And, as mentioned above, rotation of the exciter coil 12 can be performed by a rotation stage external to the resonator chamber.

[0037] As shown in the VSWR and voltage behavior in Figures 7A and 7B, the HFSS modeling results show that the specific r0 / r min The ratio indicates that the optimum exciter coil orientation for maximum power transfer is ≈7°. For this model, the maximum power transfer is 96.3% and the developed voltage for 100 W of input power is 2.27 kV. Thus, by providing rotation capability for stage drives and the like, this embodiment facilitates easy adjustment to maintain coupling between the exciter and resonator coils in a given accelerating stage of a linear accelerator.

[0038] Ideally, the center of the exciter coil loop 16 is aligned concentrically with the azimuthal axis of the toroid formed by the toroidal coil. However, slight deviations from symmetry between the two halves of the toroidal coil can cause slight voltage imbalances in the powered drift tube. According to embodiments of the present disclosure, this imbalance can be corrected by adjusting the insertion depth of the exciter coil 12. This adjustment can be achieved essentially by moving the exciter coil loop 16 into the toroidal coil or by withdrawing the exciter coil loop 16 from the toroidal coil, moving it to a new position, and then fixing it in the new position.

[0039] FIG. 8 shows a schematic diagram of an apparatus according to an embodiment of the present disclosure. The ion implanter 300 includes a linear accelerator 314. The apparatus 300 may represent a beamline ion implanter. Some elements are not shown for clarity. The ion implanter 300 may include an ion source 302, as known in the art, and a gas box 307. The ion source 302 may include an extraction system including extraction components and filters (not shown) to generate an ion beam 306 at a first energy. A suitable ion energy range for the first ion energy is, for example, 5 keV to 300 keV, although embodiments are not limited thereto. To form a high-energy ion beam, the ion implanter 300 includes various additional components for accelerating the ion beam 306.

[0040] As shown, the ion implanter 300 may include an analyzer 310 that functions to analyze the ion beam 306, similar to known devices, by varying the trajectory of the ion beam 306. The ion implanter 300 may further include a buncher 312 and a linear accelerator 314 (shown in dashed lines) disposed downstream of the buncher 312, where the linear accelerator 314 is configured to accelerate the ion beam 306 to form a high-energy ion beam 315 having an ion energy greater than the ion energy of the ion beam 306 before entering the linear accelerator 314. The buncher 312 may receive the ion beam 306 as a continuous ion beam and output the ion beam 306 as a bunched ion beam to the linear accelerator 314. The linear accelerator 314 may include multiple acceleration stages, represented by acceleration stages 110, arranged in series as shown. In various embodiments, the ion energy of the high-energy ion beam 315 may represent, or near, the final ion energy of the ion beam 306. In various embodiments, the ion implanter 300 may include additional components, such as a filter magnet 316, a scanner 318, and a collimator 320. The general functionality of the scanner 318 and collimator 320 is well known and will not be described in further detail here. In this manner, a high-energy ion beam, represented by high-energy ion beam 315, may be delivered to an end station 322 for processing a substrate 324. Depending on the state of ionization of the ion species (single, double, triple, etc. ionization), a non-limiting energy range for the high-energy ion beam 315 includes 500 keV-10 MeV, and the ion energy of the ion beam 306 is increased stepwise through various acceleration stages of the linear accelerator 314. According to various embodiments of the present disclosure, the acceleration stages of the linear accelerator 314 are powered by a resonator 110, the design of which may be consistent with the embodiments of FIGS. 2A-7B.

[0041] 9 illustrates an exemplary process flow 900. In block 902, RF power is delivered to an exciter of an RF resonator in a beamline ion implanter. The RF power may be delivered from an RF power source coupled to the exciter. In various embodiments, the RF resonator may be comprised of a toroidal resonator coil. In some embodiments, the RF resonator may be comprised of a solenoidal resonator coil. The exciter may include an exciter loop disposed within the toroidal resonator coil. In certain embodiments, the exciter loop may be centered about an azimuthal axis of the toroidal resonator coil.

[0042] In block 904, the resonator conditions may be adjusted or set to adjust the resonant frequency of the circuit formed by the RF power source and the resonator. In one example, the resonator conditions may be set by minimizing the VSWR. In particular, the adjustment may be achieved by moving an adjustable capacitance component, such as a capacitor, located within the resonator chamber that houses the resonator coil and exciter loop.

[0043] In block 906, an ion beam is generated in a beamline ion implanter including a linear accelerator using the current resonator circuit conditions established in block 904.

[0044] At decision block 908, a determination is made as to whether the resonator is out of adjustment. For example, relevant parameters such as reflected power and VSWR can be monitored to see if they remain below a threshold. If so, flow proceeds to block 910, where the power coupling to the RF resonator is adjusted by rotating the exciter loop of the exciter. Flow then proceeds to block 912.

[0045] At block 912, beam processing continues using the current resonator circuit conditions, which may or may not represent updated conditions based on the operations of block 910.

[0046] If the resonator is not misadjusted at decision block 908, flow continues to block 912. After block 912, beam processing continues, so flow may return to decision block 908. The flow loop between decision block 908 and block 912 may proceed while beam processing continues.

[0047] In view of the above, the present disclosure provides at least the following advantages: As an advantage, the exciter and resonator configuration according to the present invention provides higher magnetic coupling efficiency and potentially higher power transfer compared to known resonators, while the rotatable exciter configuration provides the advantage of another accessible adjustment "knob" for adjusting the power transfer efficiency to the resonator.

[0048] While particular embodiments of the present disclosure have been described herein, the disclosure is not limited thereto, as the art will permit, and the specification can be read in the same manner. Therefore, the above description should not be construed as limiting. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Claims

1. 1. An exciter for a high frequency resonator, comprising: an exciter coil inner portion extending along the exciter axis; an exciter coil loop disposed at a distal end of the exciter coil inner portion; and a drive mechanism including at least a rotating component for rotating the exciter coil loop about the exciter axis; An exciter equipped with:

2. The exciter of claim 1 , wherein the drive mechanism further comprises a translation component that moves the exciter coil loop along a first direction parallel to the exciter axis.

3. The exciter of claim 1 , wherein the exciter coil loop comprises a circular shape.

4. an insulating sleeve disposed around the exciter coil inner portion; and a conductive sleeve disposed around the insulating sleeve; 2. The exciter of claim 1, wherein the exciter coil loop has a first end connected to the distal end of the exciter coil inner portion and a second end connected to a conductive sleeve.

5. The exciter of claim 4 , wherein the exciter coil inner portion is coupled to receive an RF signal and the conductive sleeve is coupled to ground.

6. 5. The exciter of claim 4, further comprising a conductive ring circumferentially surrounding the conductive sleeve for connection to a resonator.

7. 1. A resonator for a linear accelerator, comprising: a toroidal resonator coil defining a toroidal shape; and an exciter disposed at least partially within the toroidal resonator coil, an exciter coil inner portion extending along the exciter axis; an exciter coil loop disposed at a distal end of the exciter coil inner portion; a drive mechanism further comprising at least a rotating component for rotating the exciter coil loop about the exciter axis; An exciter equipped with A resonator comprising:

8. 8. The resonator of claim 7, wherein said toroidal resonator coil defines an azimuthal axis, and said exciter coil loop is centered about said azimuthal axis.

9. 8. The resonator of claim 7, wherein the toroidal resonator coil defines a minor radius, the exciter coil loop has a loop radius, and the ratio of the loop radius to the minor radius is between 0.2 and 0.

3.

10. 10. The resonator of claim 9, wherein the ratio of the loop radius to the minor axis is between 0.22 and 0.

28.

11. The resonator of claim 7 , wherein the toroidal resonator coil defines a midplane, and the exciter coil loop is disposed within the midplane.

12. The resonator of claim 7 , wherein the drive mechanism further comprises a translation component that moves the exciter coil loop along a first direction parallel to the exciter axis.

13. The exciter is an insulating sleeve disposed around the exciter coil inner portion; and a conductive sleeve disposed around the insulating sleeve; 8. The resonator of claim 7, further comprising: the exciter coil loop having a first end connected to the distal end of the exciter coil inner portion and a second end connected to a conductive sleeve.

14. The resonator of claim 13 , wherein the exciter coil inner portion is coupled to receive an RF signal and the conductive sleeve is coupled to ground.

15. the toroidal resonator coil comprises a toroidal coil post; the exciter coil inner portion, the insulating sleeve, and the conductive sleeve together define an exciter shaft; and The resonator of claim 13 , wherein the exciter shaft is at least partially disposed within the toroidal coil post.

16. 1. A method of operating a linear accelerator, comprising: sending RF power to an exciter of an RF resonator in the linear accelerator, the RF resonator comprising a toroidal resonator coil and a resonator can, the exciter comprising an exciter loop disposed within the toroidal resonator coil; conducting an ion beam through said linear accelerator; rotating the exciter loop while transmitting the ion beam through the linear accelerator, wherein rotating the exciter loop adjusts power coupling between the exciter and the toroidal resonator coil; A method comprising:

17. the exciter coil includes an exciter coil inner portion extending along an exciter axis and connected to the exciter loop, the exciter coil inner portion being coupled to a drive mechanism; 17. The method of claim 16, wherein rotating the exciter loop includes using the drive mechanism to rotate an exciter coil inner portion about the exciter axis.

18. prior to transmitting the ion beam through the linear accelerator; 17. The method of claim 16, further comprising adjusting a resonator circuit condition of the RF resonator using a tunable capacitance component disposed in a resonator chamber that houses the toroidal resonator coil.

19. 17. The method of claim 16, wherein the toroidal resonator coil defines a minor radius, the exciter loop has a loop radius, and the ratio of the loop radius to the minor radius is between 0.2 and 0.3.

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