Resonator, linear accelerator configuration and ion implantation system having rotating exciter

An exciter for a high frequency resonator. The exciter may include an exciter coil inner portion, extending along an exciter axis, an exciter coil loop, disposed at a distal end of the exciter coil inner portion. The exciter may also include a drive mechanism, including at least a rotation component to rotate the exciter coil loop around the exciter axis.

FIELD OF THE DISCLOSURE

The disclosure relates generally to ion implantation apparatus and more particularly to high energy beamline ion implanters.

BACKGROUND OF THE DISCLOSURE

Ion implantation is a process of introducing dopants or impurities into a substrate via ion bombardment. Ion implantation systems may comprise an ion source and a series of beam-line components. The ion source may comprise a chamber where ions are generated. The ion source may also comprise a power source and an extraction electrode assembly disposed adjacent the chamber. The beam-line components, may include, for example, a mass analyzer, a first acceleration or deceleration stage, a collimator, and a second acceleration or deceleration stage. Much like a series of optical lenses for manipulating a light beam, the beam-line components can filter, focus, and manipulate ions or ion beam having particular species, shape, energy, and/or other qualities. The ion beam passes through the beam-line components and may be directed toward a substrate mounted on a platen or clamp.

Implantation apparatus capable of generating ion energies of approximately 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 as ion acceleration stage a linear accelerator, or LINAC, where a series of electrodes arranged as tubes conduct and accelerate the ion beam to increasingly higher energy along the succession of tubes, where the electrodes receive an RF voltage signal. Known (RF) LINACs are driven by an RF voltage applied at frequencies between 13.56 MHz-120 MHz.

In known LINACs (for the purposes of brevity, the term LINAC as used herein may refer to an RF LINAC using RF signals to accelerate an ion beam) in order to reach a targeted final energy, such as one MeV, several MeV, or greater, the ion beam may be accelerated in multiple acceleration stages. Each successive stage of the LINAC may receive the ion beam at increasingly higher energy, and accelerate the ion beam to still higher energy. A given acceleration stage of a LINAC may employ a so-called double gap configuration with one RF powered electrode, or a so-called triple gap configuration, with two RF powered electrodes.

A given acceleration stage also may include a resonator, to drive the RF electrodes with an RF voltage at the chosen RF frequency. Examples of known configurations for resonators include solenoidal resonators having a solenoidal coil generally defining a circular cylindrical shape which coil is surrounded by an electrically grounded cylindrical resonator can (RF enclosure). From an electromagnetic point of view, the resonator is an RLC oscillating circuit comprising of the coil as inductive element and the resonator can as capacitive element. At resonance, the energy is transformed periodically from magnetic energy stored in the coil into electrostatic energy as a voltage difference between the powered RF electrodes. In these solenoidal configurations, an exciter coil is provided inside the resonator can but outside the resonator coil to generate an RF signal that is magnetically coupled to the resonator coil. In particular, in the resonant RF cavity, RF energy is transferred from an RF generator to the RLC oscillating circuit. For a given input RF power, the higher the shunt impedance (Zsh) of the resonator the higher the available acceleration voltage. The necessary RF energy is transferred from the RF generator to the RLC circuit by an RF exciter (exciter). In operation of the resonant cavity the exciter plays a double role: i) to match an output impedance of the RF generator (which impedance may be 50Ω) and, ii) to maximize the power transfer from the RF generator to the RLC circuit.

Recently, so-called toroidal resonators have been proposed for use in acceleration stages, where a resonator coil defines a toroid shape and the surrounding can (cavity) has a cylindrical shape. This configuration may generate a closed magnetic field topology within the resonator. In this configuration, the placement of the exciter may need adjustment compared to known solenoidal designs, since the magnetic field is generally enclosed within the loops of the resonator coil.

With respect to these and other considerations the present disclosure is provided.

BRIEF SUMMARY

an exciter for a high frequency resonator is provided. The exciter may include an exciter coil inner portion, extending along an exciter axis, an exciter coil loop, disposed at a distal end of the exciter coil inner portion. The exciter may also include a drive mechanism, including at least a rotation component to rotate the exciter coil loop around the exciter axis.

In another embodiment, a resonator for a linear accelerator is provided. The resonator may include a toroidal resonator coil that defines a toroidal shape and an exciter, disposed at least partially within the toroidal resonator coil. The exciter may include an exciter coil inner portion, extending along an exciter axis, an exciter coil loop, disposed at a distal end of the exciter coil inner portion. The exciter may also have a drive mechanism, including at least a rotation component to rotate the exciter coil loop around the exciter axis.

In a further embodiment, a method of operating a linear accelerator is provided. The method may include sending RF power to an exciter of an RF resonator in the linear accelerator, where the RF resonator comprises a toroidal resonator coil and a resonator can, and where the exciter comprises an exciter loop that is 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 the ion beam is conducted through the linear accelerator, wherein a power coupling between the exciter and the toroidal resonator coil is adjusted.

DETAILED DESCRIPTION

An apparatus, system and method in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, where embodiments of the system and method are shown. The system and method may be embodied in many different forms and are not be construed as being limited to the embodiments set forth herein. Instead, these embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art.

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 a component of a semiconductor manufacturing device as appearing in the figures. The terminology may include the words specifically mentioned, derivatives thereof, and words of similar import.

As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” are understood as potentially including plural elements or operations as well. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as precluding the existence of additional embodiments also incorporating the recited features.

Provided herein are approaches for RF resonators, and in particular for improved high energy ion implantation systems and components, based upon a beamline architecture using linear accelerators. For brevity, an ion implantation system may also be referred to herein as an “ion implanter.” Various embodiments entail novel approaches that provide the capability of flexibly adjusting the effective drift length within acceleration stages of a linear accelerator.

FIG.1A-1Fshows different views an exemplary apparatus, referred to herein as exciter10. In particular, in addition toFIGS.1A,1B, discussed below,FIG.1Cshows details of a portion of the exciter10,FIG.1Dshows an end view of the exciter10,FIG.1Eshows a perspective view of the exciter10, whileFIG.1Fshows a side view of the exciter10. The exciter10may be suitable for use in a high frequency resonator, such as an RF resonator of a LINAC, where excitation frequency may span the MHz range. As shown inFIG.1A, the exciter10includes an exciter coil12, formed of a suitable conductor such as a high conductivity metal or metal alloy, as well as an exciter shaft17. As detailed inFIG.1B, the exciter shaft17includes a powered leg, shown as exciter coil inner portion14, insulating sleeve18, and a grounded leg, shown as conductive sleeve20.

The exciter shaft17may extend along an exciter axis, in this case defined as parallel to the Y-axis of the Cartesian coordinate system shown. The exciter coil12may further include an exciter loop16, disposed at a distal end of the exciter coil inner portion14. Thus, part of the exciter coil12is formed in the shaft17, including the exciter coil inner portion14and conductive sleeve20, while part of the exciter coil (exciter coil loop16) extends beyond the exciter shaft17.

The exciter coil loop16may define a circular shape that lies within a given plane, such as the X-Y plane. On a first end of the exciter coil loop16is connected to the distal end of the exciter coil inner portion14, as shown, while on a second end, the exciter coil loop16is connected to conductive sleeve20. This configuration allows the insulating sleeve18and exciter coil inner portion to be passed through a chamber wall22that may house the exciter coil12, as well as associated hardware of a resonator.

As further shown inFIG.1A, the exciter10may include a stage24, which stage may incorporate a drive mechanism that includes at least a rotation component (not separately shown), to rotate the exciter coil loop16around the exciter axis (Y-axis). In some examples, the drive mechanism of the stage24may further include a translation component (not separately shown), to move the exciter coil loop16along a first direction parallel to the exciter axis, in other words, along the Y-axis. As such, the orientation and position of the exciter coil loop16may be adjusted with respect to a resonator coil within a chamber housing the exciter coil loop16. Advantages of this adjustability will be discussed further below.

FIG.2Apresents a detailed front view of an embodiment of an acceleration stage100of a linear accelerator. The acceleration stage100includes a drift tube assembly102and associated resonator, shown as resonator110, for accelerating an ion beam104in a linear accelerator. As shown inFIG.8, discussed below, the resonator110may be implemented in a plurality of acceleration stages of a linear accelerator314for accelerating an ion beam306in an ion implanter300.

In the embodiment ofFIG.2A, the drift tube assembly102includes an upstream grounded drift tube, and a downstream grounded drift tube, labeled similarly as grounded drift tube electrodes102B. The drift tube assembly102further includes a pair of RF drift tube electrodes, shown as RF drift tube electrodes102A, separated by a gap therebetween. Collectively, the RF drift tube electrodes102A and grounded drift tube electrodes102B define a triple gap configuration.

The RF drift tube electrodes102A are driven by a resonator110. The resonator110includes an RF enclosure112to house a toroidal resonator coil, referred to as toroidal coil114. The toroidal coil114and similar resonator coils are described in detail in the embodiments to follow. In brief, the exciter coil12may be arranged to receive RF power as part of an RF power delivery assembly, shown as the rf circuitry124, including an RF generator120and impedance element122. While not shown in the figures, the resonator110or similar resonators, as described below, may include a capacitive tuner, located externally to the toroidal coil114but inside of a resonator can (rf enclosure112). In various non-limiting embodiments, the capacitive tuner may be movable, in a manner to adjust gross capacitance of the RLC circuit formed by the toroidal coil114and the resonator can (RF enclosure112).

Moreover, as shown inFIG.2A, and in the figures to follow, according to various non-limiting embodiments, the resonator110and similar resonators may be applied to triple gap accelerator configuration. Besides the novel configuration of exciter10, a difference over known LINACs in these embodiments is that the resonator110, resonator110A and resonator110B (which resonators are shown inFIGS.3A-C) deliver voltage to the drift tube assembly102via a toroidal coil114, as opposed to solenoidal (or helical) coils of known triple gap accelerator stages.

The exciter coil12and toroidal coil114in conjunction with the RF enclosure112act to generate RF voltages at the RF drift tube electrodes102A. To obtain the relationships between the input RF power and the voltage generated on the accelerating electrodes (RF drift tube electrodes102A), the resonant cavity including the exciter coil12, toroidal coil114, and the RF enclosure112is modelled as a lumped element circuit. Using Thevenin theorem, the RF generator circuit and resonator circuit can be transformed into a single circuit. The equivalent mutual impedance ZMcan be written as
ZM=iωLcoil+ω2M/(Z0+iωLexcit)  (1)
and similarly, the equivalent RF voltage VMis given as
VM=V0ωM/(Z0+iωLexcit)  (2)
where i2=−1, ω=2πf is angular frequency, V0and Z0are the output voltage and impedance of the rf generator, M is mutual inductance of the exciter coil and resonator coil. As can be seen in eq. (2) the power transfer efficiency (which efficiency scales with the square of the voltage) depends on the coupling between the coils, which coupling is a function of the size, structure, physical spacing, relative location, and the properties of the environment surrounding the coils. In a simplest form, the mutual inductance for two concentric coils is given by the Maxwell formula.
M=4π√{square root over (Aa)}[(2/k−k)F−2E/k](3)
with
k=2√{square root over (Aa)}/√{square root over ((A+a)2+s2)}  (4)
where A and a are the radii of the circular coils, s the distance between their centers, and F, and E are the complete elliptic integrals of the first kind and second kind, respectively.

As coupling between an exciter coil and resonator coil depends on the amount of magnetic flux linkage between the exciter coil and resonator coil, for a given size of the resonator coil an optimum dimension of the exciter coil exists where the effect of coupling is maximum. In order to cover a wide range of frequencies, the exciter coil will have a high bandwidth of operation. Therefore, according to embodiments of the disclosure, the exciter coil12is designed as a low Q factor coil, meaning a low inductance coil. Thus, as shown inFIGS.1A-1F, the exciter coil12may be designed as a one loop circular coil of radius r0. The exciter coil loop16in particular may be formed of a conductive metal, such as a silver-plated copper wire of diameter d. Similar to a coaxial cable, the conductive sleeve20ensures a return path to ground and also screens the exciter coil inner portion14from RF interference. According to embodiments of the disclosure, the diameters of the exciter coil inner portion14, insulating sleeve18, and conductive sleeve20are chosen such that the exciter coil12characteristic impedance will match an RF generator output impedance. Thus for an rf generator of impedance 50Ω (most common):

Zch=12⁢π⁢μ0ϵ0⁢ϵr⁢ln⁢Dd=50⁢Ω(5)
where μ0to and ϵ0stand for magnetic permeability and dielectric permittivity of free space and ϵrfor relative dielectric permittivity of the insulating sleeve material. Depending on the geometrical characteristics of the exciter a matching material can be chosen as insulator: air (ϵr=1), PTFE (ϵr=2), quartz (ϵr=3.7), alumina (ϵr=9.8) or other ceramics. In general, in RF electronics the efficiency of power transmission from the generator to the load is characterized by a Voltage Standing Wave Ratio (VSWR), which parameter is the ratio between the amplitudes of the reflected voltage wave and forward voltage wave. As shown inFIG.2B, VSWR is a sharp function of frequency and can take values between 1 (perfect transmission) and ∞ (zero transmission). This parameter is related to power transfer:
Pr/Pf=((VSWR−1)/(VSWR+1))2(6)
where Pr, Pfstand for the reflected and forward power, respectively. In one embodiment, by proper design of the exciter coil, the VSWR may be minimized to approach a value of 1. For the case depicted inFIG.2Bwhere VSWR=1.08 from Eq. 6, the value of reflected power represents just 0.15% of the forward power.

While the exciter coil12may be used to drive a resonator coil of any shape, in the present embodiments, such as inFIG.2A, the resonator coil is a toroidal resonator. As such, the magnetic flux130generated by the toroidal coil114, for example, is totally enclosed by the resonator coil, in other words, the magnetic flux is confined inside the coil loops. As such, in accordance with embodiments of the disclosure, in order to provide the necessary flux linkage between magnetic flux generated by an exciter coil and the magnetic flux of the toroidal resonator coil, an exciter coil needs to be inserted between the loops of a toroidal resonator coil to power the toroidal resonator coil. On the other hand, the toroidal resonator configuration benefits from the fact that magnetic flux is contained inside the toroidal coil114. This geometry avoids leakage of field lines outside the toroidal coil114, and thus leads to less induced eddy currents in the RF enclosure112of the resonator, where the lesser eddy currents translate into smaller resistance of the RLC circuit and implicitly higher shunt impedance.

To illustrate examples of this insertion geometry of exciter coil within a resonator coil,FIG.3A,FIG.3B, andFIG.3Cprovide examples of two different resonators, according to embodiments of the disclosure. In particular,FIG.3A,FIG.3B, show a side view, and end view, respectively, for a resonator110A, according to an embodiment of the disclosure, whileFIG.3Cshows a side view for another resonator, according to another embodiment of the disclosure. Each of these resonators uses a toroidal coil. As used herein, the term “toroidal coil” may refer to two separate coils that are mutually arranged to define a toroid shape, where each of the separate coils may form a part of the toroid shape, such as similar halves of the toroid. As shown more clearly inFIG.3B, the toroidal coil114includes a plurality of loops or turns. The toroidal coil114includes two coils arranged as two halves, having N turns each, and constructed of a suitable conductor, such as silver plated copper tubing. The turns of each half of the toroidal coil114are wound in the same direction, enabling the phase difference between the voltage on powered drift tubes to be 180° (antiphase). At the upper part of the toroidal coil114, the two ends of the toroidal coil114are extended by a length l0and passed through an opening (not shown) in the rf enclosure to for separate connection to two separate powered RF drift tube electrodes (RF electrodes102A), described above. At the bottom part the loops of the toroidal coil114may be connected to a grounded enclosure wall (see chamber wall22).

Turning first toFIG.3C, a first insertion geometry is shown. The exciter coil12is inserted toward the bottom of the toroidal coil114with the center of the loop on the azimuthal axis of the toroid and equally spaced from the toroid legs. Said differently, the long axis of the exciter coil12extends along the Z-axis, orthogonal to the X-Y plane. Because the bottom legs of the toroidal coil are connected to the ground, this configuration reduces the risk of arcing between the exciter coil12and the toroidal coil114. In addition, the exciter coil loop16may be symmetrically placed to ensure a balanced voltage on the two halves of the toroidal coil114. A drawback of this configuration stems from the fact that the conductive sleeve20has to be passed through the loops of the toroidal coil114and then connected to the grounded chamber wall1. While functional, this configuration introduces a voltage drop along the exciter coil12, because the exciter shaft (meaning, in particular, the exciter coil inner portion14) is relatively longer in order to be long enough to reach the chamber wall22, and thus reduces the efficiency of the power transfer.

A more advantageous insertion geometry for exciter coil12is depicted inFIG.3AandFIG.3B. In this case the exciter coil12is inserted at the bottom of the system between the legs of the toroidal coil114. The center of the exciter coil loop16is aligned on the azimuthal axis of the toroid (meaning the circle on the Oyz symmetry plane of the toroid, having a radius equal to major radius of the torus (RMajor) conductive sleeve20is electrically connected to the grounded pedestal of the toroidal coil114. While maintaining the low arcing risk and the balanced voltage, in this configuration the return path to ground is shortened. Consequently, the voltage drop on the exciter10is reduced, which reduction translates into better power transfer efficiency.

For an ideal case (no losses) the magnetic energy has been shown to convert entirely into electrostatic energy resulting in 1:1 energy conversion from the toroidal coil114(magnetic energy) to the accelerating ion (kinetic energy). However, in real systems there are losses limiting 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, as higher Zshas higher the voltage generated on the accelerating electrodes. Theoretical analysis shows Zshscales with inductance of the coil as ˜L3/2which relationship means the larger L becomes the larger is Zsh. On other hand, because the cavity forms an RLC circuit the circuit will oscillate with a certain frequency, which frequency at resonance is
f0=½π√{square root over (LC)}(7)
where L is the inductance of the coil and C the capacitance of the system.
Therefore, the coil-can (enclosure) resonator system is designed to have an as-high-as-possible shunt impedance (Zsh), and simultaneously a natural resonance frequency (f0) as close as possible to the desired operating RF frequency (e.g., 13.56 MHz and 27.12 MHz). As noted above, the small departures of the resonant frequency from the operating frequency may be corrected with a capacitive tuning component (here, one possible location of a capacitive tuning component140is shown in the dashed lines),

As shown by Eqs (3)-(4), the mutual coupling depends on the sizes and relative location of the coils. Therefore, for a given resonator coil geometry there will be an optimal size of the inductive RF exciter, meaning the exciter coil loop16diameter. The electrical behavior induced by a set of exciter coils having identical characteristic impedance (Zch) but different loop radii was modelled against the same resonator coil. As can be seen inFIG.4AandFIG.4B, HFSS (High Frequency Simulation Software) modelling results show that the optimal ratio of the exciter loop radius to toroid minor radius where the power transfer is maximum corresponds to a value of approximately 0.25. For this ratio, VSWR˜1.1 (corresponding to 99.7% transferred power) and the voltage on the powered slits for 100 W input power in the exciter10is 2.25 kV. As described previously, in order to work properly and achieve the maximum power transfer and then conversion into maximum voltage on energized slits, the resonant frequency of the system must match the frequency of the RF generator.

In accordance with embodiments of the disclosure, the resonator may be firstly tuned for resonance in the absence of an ion beam. During operation due to thermal effects, the resonator frequency may drift from a designed value, requiring an operation to bring the resonator back to a resonance value. This return to resonance may be accomplished using a tuning system, including, for example, an adjustable capacitor. However, in the presence of beam, the resonator load impedance is changed as well, due to electrical resistance introduced by the beam. This impedance change will affect the power coupling, leading to a circumstance where the coupling of exciter loop to a resonator coil is not optimum. According to the present embodiments, the coupling of exciter10to the toroidal coil114may be adjusted with the provision of a movement mechanism for exciter10, such as the drive mechanism of stage24, discussed above. In other words, by rotating the exciter coil loop16around Oy axis, the coupling is readily changed, thus exposing more or less “effective” surface area, which change will maximize magnetic flux linkage between the exciter10and the toroidal coil114.

FIG.5A,FIG.5BandFIG.5C, show an end view of a resonator operated in different rotation orientations of an exciter loop, according to embodiments of the disclosure; respectively, for an embodiment of a resonator. In particular, inFIG.5A,FIG.5B, andFIG.5C, the angle between the normal on the exciter loop surface and the tangent to the toroid azimuthal axis are varied from 0° to 15° and then to 30°, respectively.

FIG.6AandFIG.6Bshows construction details of an embodiment of a rotating exciter. Toroidal coil post111is hollow, having a concentric cylindrical hole of a diameter slightly larger than the diameter of the conductive sleeve20which concentric cylindrical hole spans all the way from the toroidal coil legs down to the chamber wall. The exciter shaft17(conductive sleeve20, insulating sleeve18, and exciter coil inner portion14) is passed through and can rotate freely in the post cylindrical hole. At the bottom of the post, insulating sleeve18and powered leg (exciter coil inner portion14) of the exciter coil12are passed through a chamber wall (not separately shown) and further to a stage24, which configuration may ensure a dynamic connection with the RF generator120using a spring loaded electrical connection. Grounding connection between the conductive sleeve20and toroidal coil post111is ensured by a connection ring116, which ring may be affixed, such as by a side screw to the conductive sleeve20, where the connection ring has a diameter slightly larger than the post hole. In this fashion the connection ring116sits on the top portion of the toroidal coil post111and thus ensures electrical path to ground. The rotation of the exciter coil12may then be performed by a rotation stage outside the resonator chamber, as discussed above.

As depicted in the VSWR and voltage behavior ofFIG.7AandFIG.7B, HFSS modelling results show for the particular r0/rminratio chosen in the model, the optimal value of the exciter coil orientation where a maximum power transfer is achieved is ≅7°. For this model, the maximum power transfer is 96.3% and the developed voltage is 2.27 kV for 100 W input power. Thus, by providing rotation capability, such as through a drive of a stage, the present embodiments facilitate facile tuning to maintain coupling of exciter and resonance coil in a given acceleration stage of a linear accelerator.

Ideally the center of the exciter coil loop16should align concentrically with the azimuthal axis of the toroid formed by a toroidal coil. However, small departures from symmetry of the two halves of the toroidal coil may a induce slight voltage imbalance on the powered drift tubes. In accordance with embodiments of the disclosure, this imbalance may be corrected by adjusting the insertion depth of the exciter coil12. This adjusting may practically be achieved by moving the exciter coil loop16into the toroidal coil or withdrawing the exciter coil loop16from the toroidal coil to a new position, and subsequently fixing in the new position.

FIG.8depicts a schematic of an apparatus, according to embodiments of the disclosure. The ion implanter300includes a linear accelerator314. The ion implanter300, may represent a beamline ion implanter, with some elements not shown for clarity of explanation. The ion implanter300may include an ion source302, and a gas box307as known in the art. The ion source302may include an extraction system including extraction components and filters (not shown) to generate an ion beam306at a first energy. Examples of suitable ion energy for the first ion energy range from 5 keV to 300 keV, while the embodiments are not limited in this context. To form a high energy ion beam, the ion implanter300includes various additional components for accelerating the ion beam306.

The ion implanter300may include an analyzer310, functioning to analyze the ion beam306as in known apparatus, by changing the trajectory of the ion beam306, as shown. The ion implanter300may also include a buncher312, and a linear accelerator314(shown in the dashed line), disposed downstream of the buncher312, where the linear accelerator314is arranged to accelerate the ion beam306to form a high energy ion beam315, greater than the ion energy of the ion beam306, before entering the linear accelerator314. The buncher312may receive the ion beam306as a continuous ion beam and output the ion beam306as a bunched ion beam to the linear accelerator314. The linear accelerator314may include a plurality of acceleration stages, represented by the resonators110, arranged in series, as shown. In various embodiments, the ion energy of the high energy ion beam315may represent the final ion energy for the ion beam306, or approximately the final ion energy. In various embodiments, the ion implanter300may include additional components, such as filter magnet316, a scanner318, collimator320, where the general functions of the scanner318and collimator320are well known and will not be described herein in further detail. As such, a high energy ion beam, represented by the high energy ion beam315, may be delivered to an end station322for processing a substrate324. Depending on the ionization state (single, double, triple, . . . ionization) of the ionic species, non-limiting energy ranges for the high energy ion beam315include 500 keV-10 MeV, where the ion energy of the ion beam306is increased in steps through the various acceleration stages of the linear accelerator314. In accordance with various embodiments of the disclosure, the acceleration stages of the linear accelerator314are powered by the resonators110, where the design of resonators110may be in accordance with the embodiments ofFIGS.2A-7B.

FIG.9depicts an exemplary process flow900. At block902, RF power is sent to an exciter of an RF resonator in a beamline ion implanter. The RF power may be sent from an RF power supply coupled to the exciter. In various embodiments, the RF resonator may be constructed with a toroidal resonator coil. In some embodiments, the RF resonator may be constructed with a solenoidal resonator coil. The exciter may include an exciter loop disposed within the toroidal resonator coil. In particular embodiments, the exciter loop may be centered on the azimuthal axis of the toroidal resonator coil.

At block904, resonator conditions may be adjusted or set to tune the resonant frequency of the circuit formed by the RF power supply and resonator. The resonator conditions may be set by minimizing VSWR in one example. In particular, tuning may be accomplished by moving an adjustable capacitance component, such as a capacitor disposed in a resonance chamber housing the resonator coil and exciter loop.

At block906, an ion beam is generated in a beamline ion implanter including a linear accelerator, using the current resonator circuit conditions, established at block904.

At decision block908, a determination is made as to whether the resonator is out of tune. For example, a relevant parameter such as the reflected power or VSWR may be monitored to see if the relevant parameter remains below a threshold. If so, the flow proceeds to block910, where power coupling to the RF resonator is adjusted by rotating the exciter loop of the exciter. The flow then proceeds to block912.

At block912, beam processing is continued using the current resonator circuit conditions, where the current resonator circuit conditions may or may not represent conditions that are updated based upon the operation at block910.

If at decision block908, the resonator is not out of tune, the flow proceeds directly to block912. After block912, the flow may return to decision block908as beam processing continues. The flow loop between decision block908and block912may proceed while beam processing continues.

In view of the above, the present disclosure provides at least the following advantages. For one advantage, the configuration of exciter and resonator according to the present embodiments provides higher magnetic coupling efficiency and implicitly high power transfer compared with known resonators. At the same time the rotatable exciter configuration provides the advantage of another accessible tuning “knob” for adjusting the power transfer efficiency into a resonator.

While certain embodiments of the disclosure have been described herein, the disclosure is not limited thereto, as the disclosure is as broad in scope as the art will allow and the specification may be read likewise. Therefore, the above description is not to be construed as limiting. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.