Resonator operating device, method of linear accelerator and high energy ion implantation system

Abstract

An apparatus for resonator operation, a high energy ion implantation system, and a method of operating a linear accelerator. The apparatus can include an RF power supply assembly configured to output an RF signal, a resonator coupled to receive the RF signal, the resonator including a first output and a second output, and a drift tube assembly configured to emit an ion beam and coupled to the resonator. As such, the drift tube assembly can include a first AC drift tube electrode coupled to the first output and a second AC drift tube electrode coupled to the second output and separated from the first AC drift tube electrode by a first gap. The RF power supply assembly can be switchable to switch the output from a first eigenmode frequency to a second eigenmode frequency.

Description

Technical Field

[0001] This disclosure generally relates to ion implantation devices, and more specifically, to high-energy beamline ion implantation machines, a resonator operating device, a method for linear accelerators, and a high-energy ion implantation system. Background Technology

[0002] Ion implantation is a process of introducing dopants or impurities into a substrate through bombardment. An ion implantation system may include an ion source and a series of beamline assemblies. The ion source may include a chamber in which ions are generated. The ion source may also include a power supply and an extraction electrode assembly disposed near the chamber. The beamline assembly may include, for example, a mass analyzer, a first accelerating or decelerating stage, a collimator, and a second accelerating or decelerating stage. Much like a series of optical lenses used to manipulate a beam, the beamline assembly can filter, focus, and manipulate ions or ion beams having specific substances, shapes, energies, and / or other qualities. The ion beam passes through the beamline assembly and can be guided toward a substrate mounted on a clamp or jig.

[0003] Implantable devices capable of generating ion energies of approximately 1 MeV or higher are often referred to as high-energy ion implanters or high-energy ion implantation systems. One type of high-energy ion implanter is called a linear accelerator (LINAC), in which a series of electrodes configured as tubes conduct an ion beam along a series of tubes and accelerates the ion beam to increasingly higher energies, while the electrodes receive an alternating current (AC) voltage signal. Known radio frequency (RF) LINACs are driven by RF voltages supplied from 13.56 MHz to 120 MHz. One problem in operating RF LINAC ion implanters is that the accelerating stage is configured to accelerate ions with a specific mass / charge ratio (M / q) such that the maximum number of ions can be guided through the accelerating stage. To efficiently conduct different ions with different M / q ratios, hardware modifications may be required, such as changing the electrode length of the drift tube electrodes. This disclosure is provided for these and other considerations. Summary of the Invention

[0004] In one embodiment, an apparatus may include: an RF power supply assembly configured to output an RF signal; a resonator coupled to receive the RF signal, the resonator including a first output terminal and a second output terminal; and a drift tube assembly configured to emit an ion beam and coupled to the resonator. Thus, the drift tube assembly may include: a first AC drift tube electrode coupled to the first output terminal; and a second AC drift tube electrode coupled to the second output terminal and spaced apart from the first AC drift tube electrode by a first gap. The RF power supply assembly may be switched to switch the output from a first intrinsic mode frequency to a second intrinsic mode frequency.

[0005] A method for operating a linear accelerator is provided. The method may include: guiding a first ion beam via a drift tube assembly. The drift tube assembly may include: a first AC drift tube electrode coupled to a first output of a resonator; and a second AC drift tube electrode coupled to a second output of the resonator and spaced apart from the first AC drift tube electrode by a first gap. The method may include: delivering an RF signal to the resonator at a first frequency, the first frequency representing a second eigenmode of the resonator.

[0006] A high-energy ion implantation system is provided. The high-energy ion implantation system may include: an ion source and extraction system configured to generate an ion beam at a first energy; and a linear accelerator disposed downstream of the ion source. The linear accelerator is configured to accelerate the ion beam to a second energy greater than the first energy. The linear accelerator may include multiple acceleration stages; and an RF power system including multiple RF power assemblies and configured to output multiple RF signals separately to the multiple acceleration stages. The RF power system may be configured to send a first RF signal to the linear accelerator corresponding to a first eigenmode frequency of a first resonator of the multiple acceleration stages, and a second RF signal to the linear accelerator corresponding to a second eigenmode frequency of a second resonator of the multiple acceleration stages. Attached Figure Description

[0007] Figure 1 An exemplary apparatus according to an embodiment of this disclosure is shown.

[0008] Figure 1A An exemplary ion implantation system according to an embodiment of this disclosure is shown.

[0009] Figure 2 The general characteristics of the drift tube assembly are shown in the first case of operating the resonator.

[0010] Figure 3 This illustrates a second case of operating the resonator. Figure 2 The electrical characteristics of the drift tube assembly shown.

[0011] Figure 4 This illustrates the first case of operating the resonator. Figure 2 The electrical characteristics of the drift tube assembly shown vary with position.

[0012] Figure 5 This illustrates a second case of operating the resonator. Figure 3 The electrical characteristics of the drift tube assembly shown vary with position.

[0013] Figure 5A A list of ideal tube lengths for different ionic substances (hydrogen, boron, and phosphorus) is provided, shown as a function of ion energies up to 10 MeV.

[0014] Figure 6 The modeling results are presented for operating a triple-gap LINAC drift tube configuration at a single frequency.

[0015] Figure 7 The modeling results are presented for operating the triple-gap LINAC drift tube configuration at a second frequency.

[0016] Figure 8 An exemplary process flow is presented.

[0017] The accompanying drawings are not necessarily drawn to scale. They are illustrative only and are not intended to depict specific parameters of this disclosure. The drawings are intended to illustrate exemplary embodiments of this disclosure and should therefore not be construed as limiting the scope. In the drawings, the same numbers represent the same elements. Detailed Implementation

[0018] In the following, apparatus, systems, and methods according to the present disclosure will be more fully described with reference to the accompanying drawings, which illustrate embodiments of the systems and methods. The systems and methods may be implemented in many different forms and should not be considered as limited to the embodiments set forth herein. Rather, 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.

[0019] In this document, terms such as “top,” “bottom,” “upper,” “lower,” “vertical,” “horizontal,” “lateral,” and “longitudinal” may be used to describe the relative placement and orientation of the components and their constituent parts shown in the figures with respect to the geometry and orientation of the components of a semiconductor manufacturing device. The terms may include specifically mentioned words, their derivatives, and words with similar meanings.

[0020] As used herein, elements or operations described in the singular and preceded by the word "a" (or "an") are understood to potentially include multiple elements or operations as well. Furthermore, references to "one embodiment" in this disclosure are not intended to exclude the existence of other embodiments that also encompass the described features.

[0021] This document provides methods for improving high-energy ion implantation systems and components (specifically, ion implanters based on linear accelerators) using a beamline architecture. For brevity, the ion implantation system may also be referred to herein as an "ion implanter." Various embodiments require novel methods that provide the ability to flexibly adjust the effective drift length within the acceleration stage of a linear accelerator.

[0022] Figure 1 A schematic diagram of an apparatus according to an embodiment of this disclosure is shown. Apparatus 10 includes an acceleration stage 20-A of a LINAC (shown as a linear accelerator 114) and associated circuitry including an RF voltage source 40-A and a controller 50. Figure 1 As shown, the linear accelerator 114 may include multiple acceleration stages, illustrated as acceleration stages 20-B…20-N. In various embodiments, one or more of the stages of the linear accelerator 114 may include components of acceleration stage 20-A, as detailed herein.

[0023] In order to place the operation of device 10 in context, Figure 1A An ion implanter 100 is shown, which may represent a beam ion implanter; for clarity, some components are not shown. As is known in the art, the ion implanter 100 may include an ion source 102 and a gas cartridge 107 disposed in a terminal. The ion source 102 may include an extraction system comprising extraction components and a filter (not shown) to generate an ion beam 106 at a first energy. Suitable ion energies for the first ion energy are in the range of 5 keV to 100 keV, but embodiments are not limited to this context. To form a high-energy ion beam, the ion implanter 100 includes various additional components for accelerating the ion beam 106.

[0024] As shown, the ion implanter 100 may include an analyzer 110 for analyzing the ion beam 106 as known in the device by altering its trajectory. The ion implanter 100 may also include a beam gatherer 112 and a linear accelerator 114 (shown in dashed lines) disposed downstream of the beam gatherer 112, wherein the linear accelerator 114 is configured to accelerate the ion beam 106 before it enters the linear accelerator 114 to form a high-energy ion beam 115 with an ion energy greater than that of the ion beam 106. The beam gatherer 112 may receive the ion beam 106 as a continuous ion beam and output the ion beam 106 as a bundled ion beam to the linear accelerator 114. As shown, the linear accelerator 114 may include multiple acceleration stages (20-A to 20-N) arranged in series. In various embodiments, the ion energy of the high-energy ion beam 115 may represent, or approximate, the final ion energy of the ion beam 106. In various embodiments, the ion implanter 100 may include additional components such as a filter magnet 116, a scanner 118, and a collimator 120, the general functions of which are well known and will not be described in further detail herein. This allows a high-energy ion beam, represented by a high-energy ion beam 115, to be delivered to a terminal station 122 for processing the substrate 124. The non-limiting energy range of the high-energy ion beam 115 includes 500 keV to 10 MeV, wherein the ion energy of the ion beam 106 is progressively increased through the various acceleration stages of the linear accelerator 114.

[0025] return Figure 1 The diagram illustrates details of an accelerator stage 20-A configured as a triple-gap electrode assembly. As used herein, the terms "triple-gap" or "triple-gap configuration" can refer to the presence of three gaps between electrodes within a given accelerator stage. In accelerator stage 20-A, the electrode assembly includes: a first ground drift tube electrode 34 (also shown as G1); a first AC drift tube electrode 30 (also shown as E1); a second AC drift tube electrode 32 (also shown as E2); and a second ground drift tube electrode 36 (also shown as G2). This configuration of the electrodes is arranged as hollow conductive cylinders to conduct the ion beam 106 through them. According to various embodiments of this disclosure, the ion beam 106 can be received as a bundle of ion beams, meaning that the ion beam 106 is received as multiple packets spaced apart from each other. Therefore, different ion packets of the ion beam 106 arrive at accelerator stage 20-A at different times and are correspondingly accelerated and sequentially conducted through accelerator stage 20-A.

[0026] like Figure 1As shown, RF voltage source 40-A is electrically coupled to resonator 22 to drive an RF voltage signal within resonator 22. Similar resonators may be included in other acceleration stages of LINAC 114, and in some embodiments may be individually coupled to dedicated RF voltage sources, shown as RF voltage sources 40-B…40-N. Resonator 22 has a first output terminal 24 coupled to a first AC drift tube electrode 30 and a second output terminal 26 coupled to a second AC drift tube electrode 32. When an RF voltage is sent to resonator 22, resonator 22 may resonate according to the frequency of the RF voltage and the configuration of resonator 22. More specifically, resonator 22 will exhibit a fundamental (resonant) frequency corresponding to the first eigenmode frequency.

[0027] In a known linear accelerator, the resonator 22 can be excited at its fundamental frequency. When the resonator 22 is excited at its fundamental frequency, the instantaneous voltages appearing on the first AC drift tube electrode 30 and the second AC drift tube electrode 32 will oscillate with equal amplitude and opposite polarity. In this case, each of the AC drift tube electrodes will be in the three gaps formed by the triple-gap configuration (e.g., Figure 2 The ion beam 106 is accelerated in each of the GAP1, GAP2 and GAP3 symbols shown in the diagram, and is discussed in more detail below.

[0028] According to embodiments of this disclosure, the device 10 may be adjustable, thereby transmitting RF signals to the resonator 22 at multiple frequencies. For example, the controller 50 and the RF voltage source 40-A may be considered as forming an RF power supply assembly that can be switched to switch the output of the RF voltage signal from a first intrinsic mode frequency to a second intrinsic mode frequency (schematically shown within the controller 50), wherein the first and second intrinsic mode frequencies are characteristics of the resonator 22. It should be noted that the ability to switch between different discrete frequencies, and the characteristics of the different intrinsic modes of the resonator 22, bring various advantages to the accelerator stage 20-A, as discussed below with reference to the accompanying drawings.

[0029] Figure 2 and Figure 3 This illustrates the difference between the two operating modes of the accelerator stage 20-A. Specifically, Figure 2 This is a block diagram illustrating the general features of the drift tube assembly 30-A in a first configuration for operating the resonator 22 (not shown). The drift tube assembly 30-A includes... Figure 1 The aforementioned electrodes are referred to as E1, E2, G1, and G2. Figure 2As shown, there is a gap between each pair of consecutive electrodes. GAP1 is located between the first ground drift tube electrode 34 and the first AC drift tube electrode 30, GAP2 is located between the first AC drift tube electrode 30 and the second AC drift tube electrode 32, and GAP3 is located between the second ground drift tube electrode 36 and the second AC drift tube electrode 32.

[0030] When an RF voltage is applied to the resonator 22, the first AC drift tube electrode 30 and the second AC drift tube electrode 32 will experience an oscillation voltage. Figure 2 V1 and V2 are shown respectively. When the resonator 22 is operated at the fundamental frequency, the oscillation voltage experienced by the first AC drift tube electrode 30 and the second AC drift tube electrode 32 will generate a "triple gap" acceleration stage. The first acceleration gap appears between the first ground drift tube electrode 34 and the first AC drift tube electrode 30, and corresponds to the physical gap, i.e., GAP1. There is a second acceleration gap corresponding to GAP2 between the first AC drift tube electrode 30 and the second AC drift tube electrode 32, and there is a third acceleration gap corresponding to GAP3 between the second ground drift tube electrode 36 and the second AC drift tube electrode 32.

[0031] In other words, since the first ground drift electrode 34 remains fixed at ground potential, when an RF voltage is received from the resonator 22 at the first end, an oscillating potential difference across GAP1 will occur between the first ground drift electrode 34 and the first AC drift electrode 30. Because the second AC drift electrode 32 is coupled to the resonator 22 at the second end (see...), Figure 1 Furthermore, since the resonator operates at the fundamental frequency or in the first intrinsic mode, the instantaneous voltage at the first AC drift tube electrode 30 and the instantaneous voltage at the second AC drift tube electrode 32 will have opposite polarities, thereby generating a second potential difference across the gap GAP2. Figure 2 As shown, the voltage V1 at the first AC drift tube electrode 30 can be represented by V1 = Vo cos(ωt), while the voltage at the second AC drift tube electrode 32 is given by V2 = Vo cos(ωt + π). In the configuration where V1 and V2 are 180 degrees (π) out of phase with each other, Figure 2 The operating frequency (ω) of the condition corresponds to the first eigenmode of the resonator 22. Since the second ground drift tube electrode 36 remains fixed at ground potential, when an RF voltage is received from the resonator 22 at the second terminal, an oscillating potential difference will occur across GAP3 between the second ground drift tube electrode 36 and the second AC drift tube electrode 32. These gaps, spanning GAP1, GAP2, and GAP3 respectively, generate a first accelerating electric field at t = zero radians, a second accelerating electric field at t = π radians, and a third accelerating electric field at t = 2π radians.

[0032] exist Figure 2 In the operating mode shown, the drift tube assembly 30-A is thus used to accelerate the ion beam 106 through three gaps, wherein the lengths of various drift tube electrodes along the beam transport direction (horizontal axis in the figure) can be customized to optimize the transport of the ion beam 106 within the bundle. The length of the first AC drift tube electrode 30 is shown as D. E1 The length of the second AC drift tube electrode is shown as D. E2 These lengths can be optimized to accelerate the ion encapsulation at a given ion energy and M / q ratio, thereby generating the maximum ion acceleration through the drift tube assembly 30 Å. For a given ion energy and M / q ratio, the length D... E1 The device can be configured such that the ion packet drifts through the first AC drift tube electrode 30 for a predetermined time based on the frequency of the applied RF voltage signal. The timing of the drift time ensures that the second drift tube electrode 32 receives the ion packet at a suitable point in the period of the RF voltage signal, thereby maximizing the acceleration of the ion packet. It should be noted that the length of the second AC drift tube electrode 32 is shown as possibly greater than D. E1 The length is to account for the relatively high energy of ions traveling through the second AC drift tube electrode 32.

[0033] Figure 2 The operation may be particularly well-suited for ions with relatively low ion energy and / or relatively high M / q ratios, where the ion velocity and therefore drift time are relatively low.

[0034] Figure 3 This is a block diagram illustrating the general characteristics of the drift tube assembly 30-A in a second case of operation of the resonator 22 (not shown). In this case, the resonator 22 operates at a second higher frequency (also shown as ω) corresponding to the second eigenmode of the resonator 22. According to an embodiment of this disclosure, Figure 2 The fundamental frequency or first eigenmode frequency pair Figure 3 The ratio of the second intrinsic mode frequency to the first intrinsic mode frequency is 1 / √2. According to some embodiments, the first intrinsic mode frequency is at least 13.56 MHz, including frequencies of 20 MHz, 27.12 MHz, or 40 MHz. Therefore, for a given first intrinsic mode frequency, the second intrinsic mode frequency will be a factor of √2. When relatively low M / q ions are accelerated at higher energies, Figure 3 This "second harmonic operation" may be particularly suitable for the operation of ion implantation machines. Consistent with the foregoing discussion, relatively high-velocity ions will require relatively long drift tube lengths to increase the flight time between acceleration gaps so that the arrival time of the ions coincides with the peak voltage of a given oscillating voltage electrode. Figure 3 The operation was carried out in the following manner to achieve this result.

[0035] exist Figure 3 (as well as Figure 2 In the case of ), the applied RF voltage is applied to the drift tube assembly through the resonator 22, such as Figure 1 As shown in the configuration. Since the frequency of the RF voltage represents the second eigenmode (second harmonic) of the resonator 22, at any given moment, the oscillation voltage at the first AC drift tube electrode 30, given by V = Vo cos(ωt), has the same amplitude and the same polarity as the oscillation voltage at the second AC drift tube electrode 32 (V = Vo cos(ωt)). When operating at the second eigenmode frequency, this condition results in several characteristics of the drift tube assembly 30-A. Figure 2 Conversely, the three solid gaps of the drift tube assembly 30-A generate a first accelerating electric field at t = zero radians across GAP1, and a second accelerating electric field at t = π radians across GAP3, while no accelerating electric field exists across GAP2. Therefore, only GAP1 and GAP3 act as accelerating gaps, while GAP2 does not. In other words, Figure 3 The operation can be considered as converting the drift tube assembly 30-A into a dual-gap acceleration stage, that is, having only two acceleration gaps.

[0036] To further explain the operation of this embodiment, Figure 4 The diagram illustrates a first case for operating the resonator 22 (where the applied voltage has the frequency characteristics of a first eigenmode of the resonator 22). Figure 2 The potential and electric field of the drift tube assembly 30-A vary with position. Figure 5 This illustrates a second case for operating the resonator 22 (where the applied voltage has a frequency characteristic of the second eigenmode of the resonator 22). Figure 3 The electrical characteristics of the drift tube assembly shown vary with position.

[0037] Specifically Figure 4 The simulated voltage and electric field distribution along the Z-axis are shown as a function of position along the propagation direction of the ion beam (shown in meters as Z-axis or axis). Figure 4 and Figure 5In the example illustrated, the maximum amplitude of the voltage shown is approximately 100,000 V, which corresponds to the maximum amplitude of the RF voltage applied to resonator 22. When resonating at the fundamental frequency or the first eigenmode frequency, the voltage of the first AC drift tube electrode 30 and the voltage of the second AC drift tube electrode 32 are out of phase by π radians, and remain so at any given time. When resonating at the second eigenmode frequency, the voltage on the first AC drift tube electrode 30 is the same as the voltage on the second AC drift tube electrode 32. The voltage V represents the amplitude of the voltage applied at a given time, varying with position along the Z-coordinate, while the electric field Ez represents the amplitude of the electric field along the Z-direction (meaning along the Z-axis), varying with position along the Z-coordinate. Therefore, the larger the amplitude of Ez, the larger the accelerating field along the Z-axis, thus tending to accelerate ions to higher energies.

[0038] In principle, the voltage in the first grounded drift tube electrode 34 will be zero, and curve V will show a value close to zero until the Z coordinate = 0, corresponding to the outlet (downstream) side of the first grounded drift tube electrode 34. Then, at the inlet of the first AC drift tube electrode 30, the voltage across gap GAP1 drops to -100,000V. Within the first AC drift tube electrode 30, the voltage is constant and then switches to a potential of +100,000V across GAP2. Within the second AC drift tube electrode 32, the voltage is constant and then drops to a potential of 0V across GAP3. The resulting accompanying electric field has zero amplitude within the first grounded drift tube electrode 34, increases to approximately -4.5E6 V / m in the middle of GAP1, and decreases to approximately zero within the first AC drift tube electrode 30. The accompanying electric field increases to approximately +4.5E6 V / m in the middle of GAP2 and decreases to approximately zero within the second AC drift tube electrode 32. The resulting accompanying electric field also switches to a value of approximately -4.5E6 V / m in the middle of GAP3, and decreases to approximately zero within the second grounded drift tube electrode 36. Therefore, in Figure 4 The configuration forms three different acceleration gaps, where the amplitude of the acceleration field can reach 4.5E6 V / m.

[0039] As mentioned above, Figure 5 Showing for with Figure 4 The same resonator topology and voltage and electric field distribution of the drift tube assembly are shown, but the resonator 22 operates under the condition that an RF voltage is applied at a second-highest harmonic frequency (meaning the second eigenmode). The voltage appearing on the first AC drift tube electrode 30 and the voltage appearing on the second AC drift tube electrode 32 now oscillate simultaneously with equal amplitude and the same polarity.

[0040] In principle, the voltage in the first grounded drift tube electrode 34 will be zero, and the curve V will show a value close to zero until the Z coordinate = 0, corresponding to the outlet (downstream) side of the first grounded drift tube electrode 34. Then, at the inlet of the first AC drift tube electrode 30, the voltage across gap GAP1 increases to + to 100,000V. Within the first AC drift tube electrode 30, the voltage is constant and remains almost constant across GAP2, continues to remain constant within the second AC drift tube electrode 32, and then decreases to zero across GAP3. The resulting associated electric field exhibits zero amplitude within the first grounded drift tube electrode 34, increases to approximately +4E6 V / m in the middle of GAP1, and decreases to approximately zero within the first AC drift tube electrode 30. The resulting electric field also exhibits near-zero amplitude within gap GAP2 and the second AC drift tube electrode 32, decreases to approximately -4E6 V / m in the middle of GAP3, and returns to zero within the second grounded drift tube electrode 36.

[0041] therefore, Figure 5 The configuration provides only two acceleration gaps, corresponding to GAP1 and GAP3, while no acceleration occurs across GAP2. In other words, by effectively binding the voltages on the two AC drift tube electrodes to the zero electrode field across GAP2, Figure 5 The configuration creates a longer quasi-drift tube, simulating a known long drift tube dual-gap acceleration stage, by increasing the field-free drift interval between the successive acceleration gaps (GAP1 and GAP3). More specifically, the first length of the first AC drift tube electrode is determined by D. E1 The second length of the second AC drift tube electrode is represented by D. E2 represent, Figure 5 The drift tube assembly 30-A shown is characterized by extending along the axial direction (Z-axis) to a length equal to the first length D. E1 Second length D E2 and gap D G2 The field free zone of the sum of distances. Figure 5 In a non-limiting example, this field free zone is approximately 0.1 m, which is much longer than the length of any of the AC drift tube electrodes shown.

[0042] To illustrate the advantages of forming a longer effective drift tube Figure 5AA list of ideal drift tube lengths for different ionic substances (hydrogen, boron, and phosphorus) is provided, shown as a function of ion energies up to 10 MeV. This length specifies the distance an ion travels in time corresponding to an AC voltage of 180° or π radians. Tube length is also a function of signal frequency and is typically 13.56 MHz for linear accelerators and 40 MHz for other frequencies. It should be noted that for each ion energy, and at the two frequencies shown, the switching from phosphorus to boron ions corresponds to an increase in ideal drift tube length of more than two times. Furthermore, the ideal drift tube length increases with increasing ion energy within a given substance. For example, to accelerate boron ions using a 40 MHz RF resonator, increasing the ion energy from 500 keV to 2 MeV would increase the ideal drift tube length from 3.7 cm to 7.4 cm.

[0043] In light of the above considerations, when the ion energy increases or the M / q ratio of the ion material decreases, the drift tube assembly 30-A can switch from operating at the frequency corresponding to the first eigenmode of the resonator to operating at the frequency corresponding to the second eigenmode. This flexibility avoids the need for extensive hardware modifications to optimize performance when changing the ion material or ion energy.

[0044] Figure 6 The modeling results presented are for operating a triple-gap LINAC drift tube configuration at a single frequency. Figure 7 The modeling results used to operate a triple-gap LINAC drift tube configuration at a second frequency are presented. More specifically, Figure 6 The diagram shows the magnetic field lines around the resonator coil of resonator 22 when the triple-gap accelerator operates at its fundamental frequency (first eigenmode). Figure 7 The magnetic field lines are shown when the same resonator operates in the second-highest harmonic (second eigenmode). Figure 7 In this configuration, the field lines branch off at the center of the resonant coil. For the same rate of change of current, this more complex path of the magnetic field produces a larger voltage, causing the coil to exhibit a significantly larger effective self-inductance and a second eigenmode resonant frequency that is greater than the frequency of the first eigenmode.

[0045] return Figure 1 and Figure 2According to further embodiments of this disclosure, an RF signal can be selectively applied at a second intrinsic mode frequency to select an acceleration stage of a linear accelerator. For example, a first RF signal can be applied to acceleration stage 20-A at a first intrinsic mode (fundamental) frequency of resonator 22, while a second RF signal can be applied to acceleration stage 20-B at a similar second intrinsic mode (fundamental) frequency to resonator 22. Since the ion energy will be higher in the second acceleration stage located downstream of the first acceleration stage, the generation of an effective “dual-gap” acceleration stage may be suitable for conducting relatively faster ions via an effectively longer drift tube formed by two separated AC drift tube electrodes, as disclosed above. On the other hand, for an upstream acceleration stage where the ion energy is relatively lower, a single AC drift tube electrode can individually have sufficient length for delivering the ion beam at suitable timing.

[0046] Therefore, the controller 50 can be used to selectively switch the frequency of the RF signal transmitted from the RF voltage source to a suitable acceleration stage between a first intrinsic mode frequency and a second intrinsic mode frequency, based on the given ionic substance, ionic charge state, and ionic energy.

[0047] Figure 8 An exemplary process flow 800 is illustrated. At block 802, an operation occurs where an ion beam is guided via a drift tube assembly including a first AC drift tube electrode and a second AC drift tube electrode. At block 804, an RF signal is delivered at a frequency corresponding to a second eigenmode of the drift tube assembly to a resonator coupled to the drift tube assembly, while the ion beam is conducted through the resonator. At block 806, the ion beam is guided via the drift tube assembly; the second ion beam may have lower energy or a lower M / q ratio compared to the first ion beam. At block 808, a second RF signal is applied to the resonator at a second frequency corresponding to the first eigenmode of the resonator, while the second ion beam is conducted through the resonator.

[0048] In view of the foregoing, the embodiments disclosed herein provide at least the following advantages. Firstly, by providing a method for selectively applying an RF signal to a resonator at a second eigenmode frequency, this method offers the advantage of adjusting the effective AC drift tube length in the drift tube assembly without requiring cumbersome hardware changes within the accelerator stage. Secondly, this embodiment provides the ability to extend the accelerator-based LINAC processing capability for multiple ions of different masses without delay, as hardware changes to the drift tube assembly are avoided. A further advantage provided by this embodiment is the ability to improve the delivery efficiency of a given ion beam for a given ion material by selectively applying the second eigenmode excitation frequency to select an accelerator stage (e.g., a downstream accelerator stage where ion energies are relatively high).

[0049] While certain embodiments of this disclosure have been set forth herein, this disclosure is not limited thereto, as the scope of this disclosure has the broadest range permitted by the art and as indicated in this specification. Therefore, the foregoing description should not be considered restrictive. Other modifications within the scope and spirit of the appended claims will be apparent to those skilled in the art.

Claims

1. An apparatus for operating a resonator, comprising: The radio frequency power supply assembly is configured to output radio frequency signals; A resonator, coupled to receive the radio frequency signal, the resonator including a first output terminal and a second output terminal; as well as A drift tube assembly, configured to emit an ion beam and coupled to the resonator, the drift tube assembly comprising: The first AC drift tube electrode is coupled to the first output terminal; as well as The second AC drift transistor electrode is coupled to the second output terminal and separated from the first AC drift transistor electrode by a first gap. The radio frequency power supply assembly is capable of switching the output from a first intrinsic mode frequency to a second intrinsic mode frequency. This ensures that the oscillation voltages at the first AC drift tube electrode and the second AC drift tube electrode have the same amplitude and polarity, thereby changing the acceleration stage of the drift tube assembly from a triple-gap configuration to an effective dual-gap configuration.

2. The apparatus of claim 1, wherein the triple gap configuration comprises: The first ground drift tube electrode is disposed upstream of the first AC drift tube electrode and separated from the first AC drift tube electrode by a second gap; and the second ground drift tube electrode is disposed downstream of the second AC drift tube electrode and separated from the second AC drift tube electrode by a third gap.

3. The apparatus of claim 1, wherein the first intrinsic mode frequency is at least 13.56 MHz.

4. The apparatus of claim 1, wherein the first intrinsic mode frequency is 13.56 MHz, 20 MHz, or 27.12 MHz.

5. The apparatus of claim 1, wherein the ratio of the first intrinsic mode frequency to the second intrinsic mode frequency is 1 / √2.

6. The apparatus of claim 1, wherein the first AC drift tube electrode includes a first length along an axial direction, and the second AC drift tube electrode includes a second length along the axial direction, and wherein the drift tube assembly defines a field free region along the axial direction, the field free region extending along the axial direction by a distance equal to the sum of the first length, the second length, and the first gap.

7. A method for operating a linear accelerator, comprising: The first ion beam is guided via a drift tube assembly of an accelerator stage, the drift tube assembly comprising: The first AC drift tube electrode is coupled to the first output terminal of the resonator; and The second AC drift tube electrode is coupled to the second output terminal of the resonator and separated from the first AC drift tube electrode by a first gap; and A radio frequency signal is delivered to the resonator at a first frequency, the first frequency representing a second eigenmode of the resonator. This ensures that the oscillation voltages at the first AC drift tube electrode and the second AC drift tube electrode have the same amplitude and polarity, thereby changing the acceleration stage of the drift tube assembly from a triple-gap configuration to an effective dual-gap configuration.

8. The method of claim 7, comprising: A second ion beam is guided via the drift tube assembly, the second ion beam having a second specific mass / charge ratio, wherein the first ion beam has a first specific mass / charge ratio that is smaller than the second specific mass / charge ratio; as well as A second radio frequency signal is delivered to the resonator at a second frequency, the second frequency representing a first eigenmode of the resonator. The acceleration stage of the drift tube assembly is operated in the triple gap configuration.

9. The method of claim 7, comprising: A second ion beam is guided via the drift tube assembly, the second ion beam comprising a second energy, wherein the first ion beam comprises a first energy greater than the second energy; as well as A second radio frequency signal is delivered to the resonator at a second frequency, the second frequency representing a first eigenmode of the resonator. The acceleration stage of the drift tube assembly is operated in the triple gap configuration.

10. The method of claim 7, wherein the linear accelerator comprises a plurality of acceleration stages, wherein the first AC drift tube electrode and the second AC drift tube electrode are disposed in a downstream acceleration stage of the linear accelerator, the method further comprising: The first ion beam is guided via a second drift tube assembly, the second drift tube assembly being disposed in an upstream accelerator stage of the linear accelerator relative to the downstream accelerator stage, the second drift tube assembly comprising: The third AC drift tube electrode is coupled to the first output terminal of the second resonator; and The fourth AC drift tube electrode is coupled to the second output terminal of the second resonator and is separated from the second AC drift tube electrode by a second gap; and A second radio frequency signal is delivered to the second resonator at a second frequency, the second frequency representing a first eigenmode of the resonator.

11. The method of claim 10, wherein the upstream accelerator stage receives the first ion beam at a first ion energy, and The downstream acceleration stage receives the first ion beam at a second ion energy, where the second ion energy is greater than the first ion energy.

12. The method of claim 7, wherein the drift tube assembly comprises a triple-gap accelerator configuration, wherein a first grounded drift tube electrode is disposed upstream of the first AC drift tube electrode and spaced apart from the first AC drift tube electrode by a second gap; and wherein a second grounded drift tube electrode is disposed downstream of the second AC drift tube electrode and spaced apart from the second AC drift tube electrode by a third gap.

13. The method of claim 7, wherein the first frequency is at least 13.56 MHz.

14. The method of claim 13, wherein the first frequency is 13.56 MHz, 20 MHz, or 27.12 MHz.

15. The method of claim 8, wherein the ratio of the first frequency to the second frequency is 1 / √2.

16. The method of claim 7, wherein the first AC drift tube electrode includes a first length along an axial direction, and the second AC drift tube electrode includes a second length along the axial direction, and wherein the drift tube assembly defines a field free region along the axial direction, the field free region extending along the axial direction by a distance equal to the sum of the first length, the second length, and the first gap.

17. The method of claim 7, wherein the resonator generates an instantaneous voltage at the first AC drift tube electrode that is equal to the instantaneous voltage at the second AC drift tube electrode.

18. A high-energy ion implantation system, comprising: The ion source and extraction system are configured to generate an ion beam at the first energy level. A linear accelerator, disposed downstream of the ion source, is configured to accelerate the ion beam to a second energy greater than the first energy, wherein the linear accelerator includes multiple acceleration stages. as well as The radio frequency power system includes multiple radio frequency power assemblies and is configured to output multiple radio frequency signals separately to the multiple acceleration stages; The radio frequency power system is configured to send a first radio frequency signal to the linear accelerator corresponding to a first eigenmode frequency of a first resonator of the plurality of accelerator stages, and to send a second radio frequency signal to the linear accelerator corresponding to a second eigenmode frequency of a second resonator of the plurality of accelerator stages. Specifically, for a given acceleration stage among the plurality of acceleration stages, the change from the first radio frequency signal to the second radio frequency signal causes the oscillation voltage at the first AC drift tube electrode and the second AC drift tube electrode to have the same amplitude and the same polarity, thereby changing the given acceleration stage from a triple-gap configuration to an effective dual-gap configuration.

19. The high-energy ion implantation system of claim 18, wherein the first resonator and the second resonator are single resonators and correspond to the given acceleration stage of the linear accelerator. The first radio frequency power assembly of the plurality of radio frequency power assemblies is coupled to the single resonator and is capable of switching the output from the first radio frequency signal to the second radio frequency signal.

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