KR20210125413A - Apparatus and techniques for generating bunched ion beam - Google Patents

Abstract

An ion implantation system comprises: an ion source; and a collector for receiving a continuous ion beam from the ion source and outputting a focused ion beam. The collector may include a drift tube assembly having a sequence in which grounded drift tubes and AC drift tubes are alternated. The drift tube assembly may include a first grounded drift tube configured to receive a continuous ion beam, at least two AC drift tubes at downstream of the first grounded drift tube, and a second grounded drift tube at downstream of the at least two AC drift tubes. The ion implantation system may include an AC voltage assembly coupled to the at least two AC drift tubes and including at least two AC voltage sources individually coupled to the at least two AC drift tubes. The ion implantation system may include a linear accelerator including a plurality of acceleration stages disposed at downstream of the collector.

Description

APPARATUS AND TECHNIQUES FOR GENERATING BUNCHED ION BEAM

Related applications

This application is a continuation of and claims priority to U.S. Patent Application Serial No. 16/107,151, filed on August 21, 2018, entitled NOVEL APPARATUS AND TECHNIQUES FOR GENERATING BUNCHED ION BEAM, NOVEL APPARATUS AND TECHNIQUES FOR It is a continuation-in-part of U.S. Patent Application Serial No. 16/842,464, filed April 07, 2020, entitled GENERATING BUNCHED ION BEAM, and claims priority thereto.

technical field

BACKGROUND This disclosure relates generally to ion implantation apparatus, and more particularly to high energy beamline ion implanters.

Ion implantation is a process that introduces dopants or impurities into a substrate through collisions. Ion implantation systems may include an ion source and a series of beam-line components. The ion source may include a chamber in which ions are generated. Beam-line components may include, for example, a mass analyzer, a collimator, and various components for accelerating or decelerating the ion beam. Much like a series of optical lenses for manipulating a light beam, beam-line components are capable of filtering, focusing, and manipulating an ion beam of a particular species, shape, energy and/or other quantities. The ion beam may pass through the beam-line components and directed towards a substrate mounted on a platen or clamp.

One type of ion implanter suitable for generating medium or high energy ion beams is a linear accelerator or LINAC, in which a series of electrodes arranged as tubes around the beam beam ion up to increasingly higher energies along successive tubes. to accelerate The various electrodes may be arranged in a series of stages, wherein a given electrode in a given stage receives an AC voltage signal to accelerate the ion beam.

LINACs use early stages that bunch the ion beam as it is conducted through the beamline. The initial stage of LINAC may be referred to as a bundler, in which a continuous ion beam is received by the collector and output as an ion beam aggregated into packets. Depending on the frequency and amplitude of the AC voltage signal, the acceptance or phase capture of an ion beam conducted through a known “double-gap” collector using a single powered electrode is It can be about 30-35%, which means that more than 65% of the beam current is lost while conducting into the acceleration stages of the linear accelerator.

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

In one embodiment, an apparatus comprises a multi-ring drift tube assembly comprising an alternating sequence of a set of grounded drift tubes and a set of AC drift tubes, arranged in an alternating manner with each other. may include The multi-ring drift tube assembly includes a first grounded drift tube configured to receive a continuous ion beam, at least two AC drift tubes arranged in series downstream of the first grounded drift tube, and at least two AC It may further include a second grounded drift tube downstream of the drift tubes. The apparatus may further include an AC voltage assembly electrically coupled to the at least two AC drift tubes. The AC voltage assembly comprises: a first AC voltage source coupled to deliver a first AC voltage signal at a first frequency to a first AC drift tube of the at least two AC drift tubes; and a second AC voltage source coupled to deliver a second AC voltage signal at a second frequency to a second AC drift tube of the at least two AC drift tubes. As such, the second frequency may be configured as an integer multiple of the first frequency.

In a further embodiment, an ion implantation system may include an ion source for generating a continuous ion beam, and a collector disposed downstream of the ion source to receive the continuous ion beam and output a focused ion beam. can The collector may comprise a drift tube assembly characterized by alternating a set of grounded drift tubes and a set of AC drift tubes, arranged in an alternating manner with one another. The drift tube assembly includes a first grounded drift tube arranged to receive a continuous ion beam, at least two AC drift tubes downstream of the first grounded drift tube; a second grounded drift tube downstream of the at least two AC drift tubes, and an AC voltage assembly electrically coupled to the at least two AC drift tubes. The AC voltage assembly may include at least two AC voltage sources each coupled to the at least two AC drift tubes. The ion implantation system may further include a linear accelerator comprising a plurality of acceleration stages disposed downstream of the collector.

In another embodiment, the apparatus may include a multi-ring drift tube assembly and an AC voltage assembly. The multi-ring drift tube assembly includes a first grounded drift tube arranged to receive a continuous ion beam, and a first AC drift disposed downstream of the first grounded drift tube and adjacent the first grounded drift tube. tube may be included. The multi-ring drift tube assembly also includes an intermediate grounded drift tube arranged downstream of the first AC drift tube and downstream of the first AC drift tube, and an intermediate grounded drift tube adjacent and adjacent to the intermediate grounded drift tube. and a second AC drift tube disposed downstream of The multi-ring drift tube assembly may also include a second grounded drift tube, wherein the second grounded drift tube is disposed adjacent the second AC drift tube and downstream of the second AC drift tube. The apparatus may further include an AC voltage assembly electrically coupled to the multi-ring drift tube assembly. The AC voltage assembly includes a first AC voltage source coupled to convey a first AC voltage signal at a first frequency to the first AC drift tube, and a second AC voltage signal coupled to convey a second AC voltage signal at a second frequency to the second AC drift tube and a second AC voltage source configured to be used, wherein the second frequency comprises an integer multiple of the first frequency.

1A illustrates an exemplary ion implantation system in accordance with embodiments of the present disclosure.
1B illustrates another ion implantation system in accordance with embodiments of the present disclosure.
2 illustrates an exemplary grouper in accordance with embodiments of the present disclosure.
3 illustrates another exemplary grouper according to other embodiments of the present disclosure.
4 shows the results of modeling of the operation of a drift tube assembly according to embodiments of the present disclosure.
5A and 5B are graphs illustrating the phase behavior of different rays of ion beams processed by different collectors, highlighting the advantages of the present embodiments.
6 illustrates an exemplary process flow in accordance with some embodiments of the present disclosure.
7 illustrates another exemplary grouper according to other embodiments of the present disclosure.
8 illustrates another exemplary grouper according to other embodiments of the present disclosure.
9 shows another exemplary grouper according to other embodiments of the present disclosure.
10 shows a sawtooth waveform.
The drawings are not necessarily to scale. The drawings are representations only and are not intended to represent specific parameters of the present disclosure. The drawings are intended to depict exemplary embodiments of the present disclosure, and thus should not be construed as limiting their scope. Within the drawings, like numbers indicate like elements.

An apparatus, system and method according to the present disclosure will now be described more fully with reference to the accompanying drawings in which embodiments of the system and method are shown. The system and method may be embodied in many different forms and should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of systems and methods to those skilled in the art.

As used herein, an element or action referred to in the singular and preceded by the word “a” or “an” should be understood to potentially include a plurality of elements or actions as well. Further, references to “one embodiment” of the invention are not intended to be construed as excluding the existence of additional embodiments that also incorporate the recited features.

Approaches to improved high energy ion implantation systems based on beamline architecture are provided herein. For the sake of brevity, an ion implantation system may also be referred to herein as an “ion implanter”. Various embodiments provide novel configurations for providing the ability to generate high energy ions, wherein the final ion energy delivered to the substrate can be 300 keV, 500 keV, 1 MeV or more. In exemplary embodiments, a novel collector design may be used to process the ion beam in a manner that increases reception of the ion beam, as described below.

Referring now to FIG. 1A , an exemplary ion implanter shown as implantation system 100 is shown in block form. The ion implantation system 100 may represent a beamline ion implanter, wherein some elements are omitted for clarity of description. The ion implantation system 100 may include an ion source 102 and a gas box 107 held at a high voltage as is known in the art. The ion source 102 may include extraction components and filters (not shown) for generating the ion beam 106 at a first energy. Examples of suitable ion energies for the first ion energy range from 5 keV to 100 keV, although embodiments are not limited in this context. To form a high energy ion beam, the ion implantation system 100 includes various additional components for accelerating the ion beam 106 .

The ion implantation system 100 may include an analyzer 110 that functions to analyze the received ion beam. Thus, in some embodiments, the analyzer 110 may receive the ion beam 106 having energy imparted by extraction optics located in the ion source 102 , wherein the ion energy is 100 keV. or less, specifically, 80 keV or less. In other embodiments, the analyzer 110 may receive an ion beam accelerated by a DC accelerator column to higher energies, such as 200 keV, 250 keV, 300 keV, 400 keV, or 500 keV. The embodiments are not limited in this context. The ion implantation system 100 may also include a collector 130 , and a linear accelerator 114 (shown in dashed lines) disposed downstream of the collector 130 . The operation of the aggregator 130 is detailed below. Briefly, a collector 130 is disposed downstream of an upstream beamline 111 to receive the ion beam 106 as a continuous ion beam (or DC ion beam) and output the beam as a focused ion beam. do. For a focused ion beam, the ion beam is output in discrete packets. At the same time, the energy of the ion beam may be increased by the collector 130 . The linear accelerator 114 may include a plurality of accelerator stages 126 arranged in series, as shown. Accelerator stages 126 may act similarly to a collector to output the focused ion beams at a given stage, and to accelerate the ion beam to a higher energy in the stages. Thus, the collector can be considered as a first accelerator stage, which differs from the downstream accelerator stages in that the ion beam is received as a continuous ion beam.

In various embodiments, the ion implantation system 100 may include additional components, such as a filter magnet 116 , a scanner 118 and a collimator 120 , including a filter magnet 116 , a scanner ( 118) and the general functions of collimator 120 are well known and will not be described in further detail herein. As such, after acceleration by the linear accelerator 114 , the high energy ion beam represented by the high energy ion beam 115 may be delivered to the end station 122 for processing the substrate 124 .

In some embodiments in which the ion beam 106 is provided directly to the analyzer 110 , the collector 130 , as noted, is continuous at a relatively lower energy, eg, lower than 100 keV. The ion beam 106 may be received as an ion beam. In other embodiments where the ion implantation system includes a DC accelerator column, the ion beam 106 may be accelerated to be supplied as a continuous ion beam at energies up to 500 keV or more. In these different cases, the exact alternating current (AC) voltages applied by the collector 130 may be adjusted according to the ion energy of the continuous ion beam received by the collector 130 .

1B shows a DC accelerator column 108 disposed downstream of an ion source 102 and arranged to accelerate the ion beam 106 to produce an accelerated ion beam 109 with a second ion energy. One embodiment of an ion implantation system 100A is shown, wherein the second ion energy is greater than the first ion energy generated by the ion source 102 . The DC accelerator column 108 may be arranged as in known DC accelerator columns, such as those used in medium energy ion implanters. The DC accelerator column may accelerate the ion beam 106 , wherein the accelerated ion beam 109 energizes the analyzer 110 and collector with an energy such as 200 keV, 250 keV, 300 keV, 400 keV, or 500 keV. It is received by the flag 130 . Otherwise, the ion implantation system 100A may function similarly to the ion implantation system 100 .

FIG. 2 shows the structure of an exemplary grouper of a linear accelerator shown as aggregator 130 , in accordance with embodiments of the present disclosure. The collector 130 may include a drift tube assembly 150 that includes a first grounded drift tube 152 arranged to receive a continuous ion beam, shown as an accelerated ion beam 109 . . As shown, the first grounded drift tube 152 is connected to electrical ground. The drift tube assembly 150 may further include an AC drift tube assembly arranged downstream of the first grounded drift tube 152 . As discussed in detail below, the AC drift tube assembly 156 is arranged to receive an AC voltage signal that is generally within the radio frequency range (RF range), which signal accelerates and manipulates the accelerated ion beam 109 . function to do 2, the AC drift tube assembly 156 includes only one AC drift tube. In other embodiments, the AC drift tube assembly 156 may include multiple AC drift tubes.

The drift tube assembly 150 further includes a second grounded drift tube 154 downstream of the AC drift tube assembly 156 . Overall, the drift tube assembly 150 receives a continuous ion beam, conducts the ion beam through hollow cylinders, and causes the ion beam to be received and further accelerated by an acceleration stage 158 located downstream. Arranged as hollow cylinders to accelerate some portions of the ion beam and decelerate others in a clustering manner into discrete packets, shown as a bunch 109A. The drift tube assembly 150 may be constructed of graphite or similar suitable material configured to minimize contamination of the ion beam conducted therethrough. Subsequent acceleration stages, denoted acceleration stage 158 , may operate with a well-defined frequency ω, and capture of populations into these acceleration structures is approximately for this basal angular frequency ω. It can be limited to a phase angle of ±5°. In order to transmit the maximum possible current through the entire beamline, it is desirable to arrange the collector 130 to produce one cluster for each cycle of this fundamental frequency ω.

As shown in FIG. 2 , the collector 130 applies an AC voltage signal to the AC drift tube assembly 156 to drive a varying voltage in the powered drift tube of the AC drift tube assembly 156 . and an AC voltage assembly 140 arranged to transmit. The varying voltage on the AC drift tube assembly 156 assembly provides different accelerations to the ions depending on the arrival time of the ions in the AC drift tube assembly 156 . In this way, the trailing end 109A1 of the collection 109A is given more speed than the leading end 109A2 of the collection 109A, and the entirety of the collection 109A is accelerated stage 158 . ) to be as compact as possible. In various embodiments, the AC voltage signal may be a composite of a plurality of individual AC voltage signals superimposed to produce an AC voltage signal in a manner to provide improved aggregation of a continuous ion beam. In various embodiments, AC voltage assembly 140 may generate a first AC voltage signal at a first frequency and a second AC voltage signal at a second frequency, wherein the second frequency is an integer of the first frequency. includes drainage. In some embodiments, AC voltage assembly 140 may generate a third AC voltage signal at a third frequency, wherein the third frequency is configured as an integer multiple of a first frequency different from the second frequency, etc. am. Thus, the second frequency, the third frequency, etc. may be harmonics of the first frequency, where the frequency may be two times, three times, etc., compared to the first frequency.

In the embodiment of FIG. 2 , the AC voltage assembly 140 is represented by V ₁ cos(ωt + φ ₁ ), V ₂ cos(2ωt + φ ₂ ), and V ₃ cos(3ωt + φ ₃ ). , is shown generating three different AC voltage signals. For purposes of illustration, AC voltage signals are shown as sinusoidal signals, although other waveforms are possible. The AC voltage assembly 140 includes a first AC voltage supply 142, a second AC voltage supply 144, and A third AC voltage supply 146 may be included. The AC voltage supply may be implemented using an RF amplifier driven by a synchronized signal generator. The general term V denotes the maximum amplitude of an AC voltage signal, while the general term φ denotes the phase of the AC voltage signal. Thus, the maximum amplitude and phase may be different between different signals. In this embodiment, the second and third AC signals exhibit doubling and tripling, respectively, of the frequency ω of the first signal. 2, the AC voltage assembly 140 may include an adder 148, wherein the adder 148 sums the individual voltage signals and converts the composite AC voltage signal 149 into an AC drift tube assembly ( 156) is output.

In various embodiments, the composite AC voltage signal may be formed from AC voltage signals, wherein the highest frequency of the AC voltage signal is about 120 MHz or less.

The composite AC voltage signal 149 is designed to adjust the phase dependence of the ions being processed by the AC drift tube assembly 156 in a manner that increases acceptance at the downstream acceleration stage. In linear accelerators of known ion implantation systems, when a continuous ion beam is focused for transmission in packets to the downstream acceleration stages, a certain fraction of the ion beam is due to the nature of the acceleration and aggregation process. lost to walls or other surfaces. Acceptance refers to the percentage of the ion beam that is not lost (eg, the percentage of beam current) and thus the percentage received by the downstream acceleration stage. As mentioned, for known ion implantation devices using linear accelerators, the acceptance can be up to about 30% to 35% when various conditions are optimized. These known ion implantation systems can drive the collector with an AC voltage signal having a frequency of 10 MHz, 13.56 MHz, or 20 MHz, with a voltage amplitude in the range of several tens of kV. In particular, in known ion implantation systems the AC voltage signal can be generated as a simple AC voltage signal of a single frequency.

In particular, the elementary component of a complex AC voltage signal _{can be simplified to V 1} cos(ωt), where the relative phase to the other two AC voltage signals is given by the _{phase offsets, φ 2} or φ _{3 , respectively.} As detailed below, these offsets can be adjusted to increase acceptance.

In particular, the inventors have found that the application of multiple frequencies to create a composite (composite waveform) results in better output phase coherence/capture compared to known aggregators using an AC voltage signal at a single frequency. ) was found to produce

Referring now to FIG. 3 , shown is a structure of a collector 160 , an exemplary collector of a linear accelerator, in accordance with additional embodiments of the present disclosure. The collector 160 may include a drift tube assembly 170 that includes a first grounded drift tube 182 arranged to receive a continuous ion beam, shown as an accelerated ion beam 109 . . As shown, the first grounded drift tube 182 is connected to electrical ground. The drift tube assembly 170 may further include an AC drift tube assembly 180 arranged downstream of the first grounded drift tube 182 . As discussed in detail below, AC drift tube assembly 180, similar to AC drift tube assembly 156, is arranged to receive AC voltage signal(s) that are generally within a radio frequency range (RF range) and , this signal serves to accelerate and manipulate the accelerated ion beam 109 . 3 , AC drift tube assembly 180 includes three AC drift tubes, shown as AC drift tube 184 , AC drift tube 186 , and AC drift tube 188 .

The drift tube assembly 170 further includes a second grounded drift tube 190 downstream of the AC drift tube assembly 180 . Overall, the drift tube assembly 170 receives a continuous ion beam, conducts the ion beam through hollow cylinders, and causes the ion beam to be received and further accelerated by an acceleration stage 192 located downstream. Arranged as hollow cylinders to accelerate the ion beam in a clustering manner into discrete packets, shown as clustering 109A. As such, the drift tube assembly 170 may be configured as a multi-ring drift tube assembly having a length (along the direction of propagation of the ion beam) of at least 100 mm and less than 400 mm.

3 , an AC voltage assembly 162 is provided, which provides an AC voltage to the AC drift tube assembly 180 to drive a varying voltage in the powered drift tube of the AC drift tube assembly 180 . arranged to transmit a signal. The AC voltage assembly 162 is configured such that a first AC voltage supply 142 drives the AC drift tube 184 , a second AC voltage supply 144 drives the AC drift tube 186 , and a third AC voltage The supply 146 may be configured to drive the AC drift tube 188 . These AC voltage signals may be synchronized in time by the controller 164 to efficiently generate a composite signal similar to the composite AC voltage signal 149 . Although FIG. 3 illustrates a configuration in which the lowest frequency AC voltage signal is supplied to the furthest upstream AC drift tube, in other embodiments, the lowest frequency AC voltage signal (V ₁ cos(ωt + φ ₁ )) is a different AC It can be applied to drift tube. The same applies to the medium frequency AC voltage signal (V ₂ cos(2ωt + φ ₂ )) and the high frequency AC voltage signal (V ₃ cos(3ωt + φ _{3 )).} This configuration has the advantage over the configuration of Figure 2, wherein the risk of the power supply interfering with other power supplies is avoided.

Although the use of a multi-frequency AC voltage signal to drive the collector is possible, in particular using multiple frequencies to generate the AC voltage signals may involve more voltage supplies, as detailed below. This may result in a longer beamline. Therefore, such a configuration in a beamline ion implanter has not been considered until now. In particular, the inventors have found that these considerations can be overcome by adjusting the drive signals to significantly improve the ion beam throughput, especially for ions with masses within the range of common dopants such as boron, phosphorus, and the like. configurations were identified. In particular, in the “single-ring” of FIG. 2 (where “ring” refers to the AC drift tube) or the “triple-ring” aggregator of FIG. 3 , a composite AC voltage signal is generated, wherein the ion beam Gathering is performed in such a way as to improve phase coherence and thus increase acceptance by using an ion beam at a targeted distance from the AC drift tube assembly.

Referring now to FIG. 4 , a composite illustration is shown including a depiction of a drift tube assembly 150 and a corresponding phase map plotted as a function of distance in millimeters along the beam path. The phase map is a graph illustrating the phase (shown on the right ordinate) as a function of distance, where the position of a single drift tube of the AC drift tube assembly 156 extends between 30 mm and 75 mm do. In this position, the voltage applied to the AC drift tube assembly 156 (shown by the left ordinate) reaches a maximum of about 18 kV and is applied at a frequency of 40 MHz. The relative phase positions of a series of 21 different rays of the accelerated ion beam 109 are shown to the right of the graph. The mass of the ions of the accelerated ion beam 109 is assumed to be 20 amu. As shown, the voltage reaches a maximum at the location of the AC drift tube assembly 156 and is zero elsewhere. At the point of entry into the AC drift tube assembly 156 , the twenty-one exemplary rays are equally spaced in topology with an interval of 18 degrees. Complex AC voltage given by _{V = V 1} cos(ωt + φ ₁ )+V ₂ cos(2ωt + φ ₂ ) +V ₃ cos(3ωt + φ ₃ ), as generated by AC voltage assembly 140 . When processed by the signal, the various rays converge topologically to the right, as shown.

At a position corresponding to 700 mm, which is 670 mm to the right of the entrance of the AC drift tube assembly 156 , the phase difference between the plurality of rays is close to zero. Thus, when the entrance to the acceleration stage 158 is located at a 700 mm position corresponding to a zero-phase difference between the multiple rays, the acceptance may be maximum. For an acceptance based on +/- 5-degree variation, in the example of Figure 4, the acceptance at the accelerator is about 55%. In various other simulations, the maximum acceptance for the configuration of FIG. 4 was calculated to be as high as 75%, a significant improvement over the 30%-35% acceptance in known ion implanters using single frequency collectors. For example, when V is set equal to 59.4 kV, the acceptance is 75%, whereas at 24 kV, the acceptance is 65%.

In particular, the same behavior for phase convergence shown in FIG. 4 using the example of the AC drift tube assembly 156 can be obtained by applying the same voltage parameters to the triple ring configuration of the AC drift tube assembly 180 . .

5A and 5B are graphs illustrating the phase behavior of different rays of ion beams, highlighting the advantage of applying a complex AC voltage signal according to the present embodiments. 5A continues with the composite AC voltage parameters of the embodiment of FIG. 4 , while FIG. 5B illustrates an example of applying a single AC voltage signal to the ion beam. In the example of FIG. 5B , the AC signal is _{given by V = V max} cos(ωt + φ), whereas in FIG. 5A , the AC signal is V = V ₁ cos(ωt + φ ₁ )+V ₂ cos(2ωt) + φ ₂ ) is given by +V ₃ cos(3ωt + φ _{3 ).} The frequency ω is 40 MHz in both cases.

In two different graphs, the phase behavior describes the phase of the given rays at a specified distance from a point near the entrance to the collector as a function of the phase of the given rays at the entrance to the collector. The designated distance is set to a distance at which the phases of different rays of the ion beam can converge appropriately. Thus, referring back to Figure 4, in cluster 109A, operation of AC drift tube assembly 156 tends to accelerate phase-lagging ions, i.e., trailing end 109A1, It tends to decelerate the phase-leading ions, ie the leading end 109A2, which causes phase convergence, for example at 700 mm.

In Fig. 5b, which is the highest phase coherent condition producing the highest relative acceptance of 35%, there is a small degree of phase difference at 400 mm even for differences in the initial phase as small as 30 degrees. For other voltages, the behavior is worse as shown. In particular, the embodiment of Figure 5a produces convergence at 700 mm, which is somewhat longer than single frequency aggregator results that require convergence at 400 mm. This result is due in part to the need to keep the AC voltage amplitude at a reasonable level for complex AC voltage signals such as about 20 kV. In the case of a single frequency aggregator, operation at 20 kV AC voltage amplitude allows convergence at 400 mm. Although the embodiment of Figure 5a may entail a somewhat longer separation between the collector and the accelerator for a single frequency collector architecture (700 mm vs 400 mm), the advantage is a significantly greater acceptance, and thus the main accelerator of LINAC. A significantly larger beam current conducted into the stages. In various additional embodiments, the convergence length may range from 300 mm to 1000 mm.

Without being limited to a particular theory, the above results may be interpreted in the following manner. Application of multiple frequencies to generate a composite or complex AC voltage signal (waveform) can produce a waveform with a shape that is more conducive to increasing capture. In principle, the waveform has a sharp characteristic like a vertical sawtooth waveform as shown in FIG. 10 . Such a waveform can accelerate ions in such a way that a single “tooth” causes them to come together to form a colony, which theoretically allows ~100% capture. In particular, in certain clusterers, a resonator based resonant circuit is used to drive an AC voltage waveform with relevant frequencies (in the megahertz range), wherein the resonant circuit essentially generates a sinusoidal waveform, The waveform does not produce as high a capture as in the vertical sawtooth case. In this approach, the addition of sinusoidal waveforms at a number of different frequencies may result in a shape close to the ideal sawtooth shape and thus increase the improved output phase coherence and capture as described above. used to create complex waveforms.

It should be noted that in the present embodiments, two or more waveforms may represent a relationship in which a first waveform is generated with a fundamental frequency and the other waveform(s) are generated with an integer multiple of the fundamental frequency. In this way, when a new component is present at an integer multiple of the fundamental frequency, each ion population will experience the same fields, and the base highest common factor frequency remains at the fundamental frequency.

In principle, the addition of a large number of waveforms (such as a Fourier series) can produce a synthesized composite waveform that more accurately approximates a sawtooth waveform, but this approach is difficult due to the increased cost of adding such a large number of frequencies. may be unrealistic. The inventors have found that the addition of only two or three harmonics of sinusoidal waveforms produces a very significant increase in output phase coherence and capture, as discussed above. Furthermore, the present inventors believe that application of different sinusoidal waveforms to separate electrodes can operate similarly to applying different sinusoidal waveforms to a single electrode, and that application of only two waveforms can be achieved by a single frequency waveform. It was found to produce significant improvements in output phase coherence and capture similar to the case of the three waveforms, in contrast to the relatively lower output phase coherence produced.

Additional stages of LINAC may perform in a similar manner to the collectors of the present embodiments, but in order to accelerate and further aggregate the packet of ions, these additional stages of LINAC are driven by complex AC voltage signals as shown. it doesn't have to be In other words, further improvements in phase convergence may be less necessary since the complex AC voltage signal of the collector has already mostly converges the phase of the various rays of the focused ion beam at the entrance to the accelerator stage. This fact enables a simpler design of AC voltage assemblies to drive the accelerator stages of LINAC.

As an example, in one embodiment of a triple-frequency composite AC signal, the fundamental frequency for the first signal may be 40 MHz, while the first harmonic frequency for the second signal added to the first signal is 80 MHz, and the second harmonic frequency for the first signal and the third signal added to the second signal may be 120 MHz.

In particular, while the above embodiments emphasize generating complex AC voltage signals based on three AC voltage signals and using a multi-ring drift tube assembly comprising three drift tubes, whereas in other embodiments , the composite AC voltage signal may be formed from two AC voltage signals or four AC voltage signals. The embodiments are not limited in this context. Likewise, a multi-ring drift tube assembly according to other embodiments may use two drift tubes or four drift tubes. The embodiments are not limited in this context.

6 illustrates an example process flow 600 in accordance with some embodiments of the present disclosure. At block 602, the ion beam is generated as a continuous ion beam, such as by extraction from an ion source. As such, the ion beam can exhibit ion energies ranging from a few keV to about 80 keV. Optionally, the continuous ion beam may be accelerated to produce an accelerated continuous ion beam. In one example, a DC accelerator column may be applied to accelerate a continuous ion beam. As such, the accelerated continuous ion beam may exhibit ion energies between 200 keV and 500 keV or, in some embodiments, more.

At block 604 , a continuous ion beam is received at a multi-ring drift tube assembly. The multi-ring drift tube assembly includes a first grounded drift tube and a second grounded drift tube, as well as a multi-ring AC drift tube assembly disposed between the first grounded drift tube and the second grounded drift tube. can do.

At block 606 , a continuous ion beam is conducted through a first AC drift tube of the multi-ring drift tube assembly while a first AC voltage signal is applied to the first AC drift tube at a first frequency.

At block 608 , a continuous ion beam is conducted through a second AC drift tube of the multi-ring drift tube assembly while a second AC voltage signal is applied to the second AC drift tube at a second frequency. In various embodiments, the second frequency may be an integer multiple of the first frequency, such as twice the first frequency. In an optional operation, the accelerated continuous ion beam is to be conducted through a third AC drift tube of the multi-ring drift tube assembly while a third AC voltage signal is applied to the third AC drift tube at a third frequency. can The third frequency may be an integer multiple of the first frequency, different from the second frequency. In this way, an accelerated continuous ion beam can be output from the multi-ring drift tube assembly as a focused ion beam.

7 illustrates another exemplary aggregator 200 for a linear accelerator, according to further embodiments of the present disclosure. The collector 200 may include a drift tube assembly 201 that includes a first grounded drift tube 202 arranged to receive a continuous ion beam, shown as an accelerated ion beam 109 . . As shown, the first grounded drift tube 202 is connected to electrical ground. The drift tube assembly 201 may further include an AC drift tube assembly 203 arranged downstream of the first grounded drift tube 182 . The AC drift tube assembly 203, similar to the AC drift tube assemblies described above, is arranged to receive an AC voltage signal(s) that are generally within the radio frequency range (RF range), which signal is 109) to accelerate/decelerate and operate. In the embodiment of FIG. 7 , drift tube assembly 201 includes an AC drift tube 204 , and two AC drift tubes, shown as AC drift tube 208 .

The drift tube assembly 201 further includes a second grounded drift tube 210 downstream of the AC drift tube assembly 203 . Overall, the drift tube assembly 201 receives a continuous ion beam, conducts the ion beam through hollow cylinders, and causes the ion beam to be received and further accelerated by a linear accelerator 212 located downstream. Arranged as hollow cylinders to accelerate/decelerate the ion beam in a clustering manner into discrete packets, shown as packet 109B. As such, the drift tube assembly 201 may be configured as a multi-ring drift tube assembly having a length (along the direction of propagation of the ion beam) of at least 100 mm and less than 400 mm.

In the embodiment of FIG. 7 , an AC voltage assembly 166 is provided, which provides an AC voltage to the AC drift tube assembly 203 to drive a varying voltage in the powered drift tube of the AC drift tube assembly 203 . arranged to transmit a signal. The AC voltage assembly 166 may be configured such that a first AC voltage supply 214 drives the AC drift tube 204 , while a second AC voltage supply 216 drives the AC drift tube 208 . . In this configuration and in the configuration of FIG. 8 , the two different AC voltage supplies may output a first frequency of 40 MHz and a second frequency of 80 MHz, or alternatively, two different AC voltage supplies may output a first frequency of 13.56 MHz and a second frequency of 27.12 MHz according to different non-limiting embodiments.

These AC voltage signals are combined to produce a beam behavior similar to that produced by a single drift tube, with a composite signal given by _{V = V 1} cos(ωt + φ ₁ )+V ₂ cos(2ωt + φ _{2 ).} It may be synchronized in time by the controller 164 . In this way, the output phase coherence as a function of the input phase of the ions can be improved over single frequency collectors in a manner similar to the embodiments of FIGS. 2-5B discussed above.

Although FIG. 7 illustrates a configuration in which the lowest frequency AC voltage signal is supplied to the furthest upstream AC drift tube 204 , in other embodiments the lowest frequency AC voltage signal (V ₁ cos(ωt + φ ₁ )) can be applied to different AC drift tubes.

FIG. 8 shows another exemplary collector 220 , according to other embodiments of the present disclosure. The collector 220 can include a drift tube assembly 221 that includes a first grounded drift tube 202 arranged to receive a continuous ion beam, shown as an accelerated ion beam 109 . . As shown, the first grounded drift tube 202 is connected to electrical ground. The drift tube assembly 221 may further include an AC drift tube 204 arranged downstream of the first grounded drift tube 202 . In the embodiment of Fig. 8, as in the embodiment of Fig. 7, the AC drift tube 208 is located downstream of the AC drift tube 204, and the second grounded drift tube 210 is the AC drift tube. It is located downstream of 208. As such, the drift tube assembly 201 may be configured as a multi-ring drift tube assembly having a length L (along the direction of propagation of the ion beam) of at least 100 mm and less than 400 mm. In addition to the components described above, the drift tube assembly 221 includes an intermediate grounded drift tube 206 disposed between the AC drift tube 204 and the AC drift tube 208 . The advantage provided by this configuration is that two power supplies (AC voltage supply 214, AC voltage supply 216) and two power supplies (AC voltage supply 214, AC voltage supply 216) driving AC drift tube 204 and AC drift tube 208 respectively. A reduced risk of cross-talk between resonant circuits.

8 illustrates a drift tube assembly 221 characterized by an alternating sequence of alternating one AC drift tube with one grounded drift tube as the ion beam is conducted down the beamline. In other embodiments of alternating sequences, three or more AC as generally described with respect to FIG. 3, except that a grounded drift tube is disposed between each successive pair of AC drift tubes. Drift tubes may be provided to generate the composite AC signal. In this way, cross-talk between all power supplies and resonators can be reduced.

에 따라 조정될 수 있으며, 여기에서 v는 속도이다. 이러한 거리는 주어진 전압에 대하여 최대 가속을 제공하지만, 어떤 바람직하지 않은 위상 효과들을 생성할 수 있다. 0.2D₀만큼 작은 더 짧은 튜브들을 사용하는 것이 더 높은 전압을 필요로 할 수 있지만, 전체적으로 더 양호한 결과들을 생성할 수 있다. 수렴 길이(L)와 관련하여, 이러한 파라미터를 더 짧게 만드는 것이 유익하지만, 더 높은 전압이 인가될 것을 요구한다. 따라서, L은 이온 종, 전압 고려사항들, 및 다른 효과들에 기초하여 상이한 실시예들에 따라 300 mm 내지 1 m의 범위일 수 있다.It should be noted that in embodiments using two frequencies, an output phase coherence of up to 200 degrees can be achieved with an acceptance of the ion beam up to 55%. In various embodiments, the tube length of the drift tubes may be adjusted with the following considerations: 1) the length is the distance the ions in a given ion beam traveled in 180°, or

can be adjusted according to , where v is the speed. This distance provides maximum acceleration for a given voltage, but can create some undesirable phase effects. Using shorter tubes as small as 0.2D ₀ may require a higher voltage, but may produce better results overall. Regarding the convergence length L, it is beneficial to make this parameter shorter, but requires a higher voltage to be applied. Thus, L may range from 300 mm to 1 m according to different embodiments based on ionic species, voltage considerations, and other effects.

Also, while the application of multi-frequency signals can generally serve to increase the convergence length when the design is limited to the maximum voltage applied and the individual frequencies are subtracted, certain multi-frequency designs do not increase the convergence length. It should be noted that this can be achieved.

9 provides an example of such an arrangement, in which a collector 230 is shown. The drift tube assembly 232 includes a first grounded drift tube 234; a first AC drift tube (236) disposed adjacent to the first grounded drift tube (234) and downstream of the first grounded drift tube (234); a first intermediate grounded drift tube (238) arranged downstream of the first AC drift tube (236); a second AC drift tube (240) disposed adjacent to the first intermediate grounded drift tube (238) and downstream of the first intermediate grounded drift tube (238); a second intermediate grounded drift tube 242 disposed adjacent the second AC drift tube 240 and downstream of the second AC drift tube 240 ; a third AC drift tube (244) disposed adjacent to the second intermediate grounded drift tube (242) and downstream of the second intermediate grounded drift tube (242); and a second grounded drift tube (246), wherein the second grounded drift tube (246) is adjacent to the third AC drift tube (244) and downstream of the third AC drift tube (244). are placed Once again, the provision of the first intermediate grounded drift tube 238 and the second intermediate grounded drift tube 242 is the first AC voltage supply 142 , the second AC voltage supply 144 , and the third AC Crosstalk between the voltage supply units 146 can be prevented.

In summary, the present embodiments provide collectors controlled using multi-frequency signals applied either in concert to a single AC drift tube or separately and individually applied to dedicated AC drift tubes. Without limitation, various embodiments may utilize commercially available frequencies as listed in Table 1 below.

[Table 1]

Table 1 above illustrates various ISM frequencies as defined by the US FCC, where, in this embodiment, each frequency will be an integer multiple of a fundamental frequency applied to one signal. Thus, in the two-frequency embodiment, a combination of 13.56 MHz and 27.12 MHz is appropriate, in the three-frequency embodiment, a combination of 13.56 MHz and 27.12 MHz, and 40.68 MHz is appropriate, and so on.

In view of the above, at least the following advantages are achieved by the embodiments disclosed herein. A first advantage is realized by providing a complex AC voltage signal to drive the concentrator, so that a significantly larger ion beam current can be transmitted via the downstream LINAC. A further advantage is the ability to drive a given AC signal from a given power supply of a plurality of AC power supplies to a dedicated electrode, which is common while still driving a larger ion beam current as in the case of a composite AC voltage signal. It avoids interference between power supplies that can occur when coupled to a common multiple power supplies coupled to drive multiple AC voltage signals through the electrodes.

Although specific embodiments of the present disclosure have been described herein, the present disclosure is not limited thereto, as the disclosure is in scope as the art will accept and the specification may be similarly read. Accordingly, the above description should not be construed as limiting. Those skilled in the art will envision other modifications within the spirit and scope of the claims appended hereto.

Claims (13)

An ion implantation system comprising:
an ion source for generating a continuous ion beam;
a buncher disposed downstream of the ion source for receiving the continuous ion beam and outputting a bundled ion beam, the buncher comprising a drift tube assembly, the drift tube The assembly comprises an alternating sequence of a set of grounded drift tubes and a set of AC drift tubes arranged in an alternating manner with each other, the drift tube assembly further comprising:
a first grounded drift tube arranged to accept a continuous ion beam;
at least two AC drift tubes downstream of the first grounded drift tube;
a second grounded drift tube downstream of the at least two AC drift tubes; and
an AC voltage assembly electrically coupled to the at least two AC drift tubes, the AC voltage assembly comprising at least two AC voltage sources individually coupled to the at least two AC drift tubes Including, the grouping group; and
and a linear accelerator comprising a plurality of acceleration stages disposed downstream of the collector for receiving and accelerating the focused ion beam.
The method according to claim 1,
The AC voltage assembly comprises:
a first AC voltage source coupled to deliver a first AC voltage signal at a first frequency to a first AC drift tube of the at least two AC drift tubes; and
a second AC voltage source coupled to deliver a second AC voltage signal at a second frequency to a second AC drift tube of the at least two AC drift tubes, wherein the second frequency is an integer multiple of the first frequency; comprising, an ion implantation system.
3. The method according to claim 2,
wherein the first frequency is 40 MHz and the second frequency is 80 MHz.
3. The method according to claim 2,
wherein the first frequency is 13.56 MHz and the second frequency is 27.12 MHz.
3. The method according to claim 2,
The aggregator is
the first grounded drift tube;
a first AC drift tube disposed adjacent the first grounded drift tube and downstream of the first grounded drift tube;
an intermediate grounded drift tube arranged downstream of the first AC drift tube;
a second AC drift tube disposed adjacent the intermediate grounded drift tube and downstream of the intermediate grounded drift tube; and
and the second grounded drift tube disposed adjacent the second AC drift tube and downstream of the second AC drift tube.
6. The method of claim 5,
The aggregator is
the first grounded drift tube;
the first AC drift tube disposed adjacent the first grounded drift tube and downstream of the first grounded drift tube;
a first intermediate grounded drift tube arranged downstream of the first AC drift tube and downstream of the first AC drift tube;
the second AC drift tube disposed adjacent the first intermediate grounded drift tube and downstream of the first intermediate grounded drift tube;
a second intermediate grounded drift tube disposed adjacent the second AC drift tube and downstream of the second AC drift tube;
a third AC drift tube disposed adjacent the second intermediate grounded drift tube and downstream of the second intermediate grounded drift tube; and
and the second grounded drift tube disposed adjacent the third AC drift tube and downstream of the third AC drift tube.
7. The method of claim 6,
The AC voltage assembly includes a third AC voltage source coupled to deliver a third AC voltage signal at a third frequency to the third AC drift tube, the third frequency being different from the second frequency. An ion implantation system comprising an integer multiple of one frequency.
8. The method of claim 7,
wherein the second frequency is twice the first frequency and the third frequency is three times the first frequency.
8. The method of claim 7,
wherein the first frequency comprises a frequency of at least 13.56 MHz and the third frequency comprises a frequency of 120 MHz or less.
The method according to claim 1,
wherein the ion implantation system further comprises a DC accelerator column disposed between the ion source and the collector and arranged to accelerate the continuous ion beam to an energy of at least 200 keV.
An ion implantation system comprising:
an ion source for generating a continuous ion beam;
a collector disposed downstream of the ion source to receive the continuous ion beam and output a focused ion beam, the collector comprising:
a first grounded drift tube arranged to receive a continuous ion beam;
a first AC drift tube disposed adjacent the first grounded drift tube and downstream of the first grounded drift tube;
an intermediate grounded drift tube arranged downstream of the first AC drift tube and downstream of the first AC drift tube;
a second AC drift tube disposed adjacent the intermediate grounded drift tube and downstream of the intermediate grounded drift tube;
the collector comprising a second grounded drift tube disposed adjacent the second AC drift tube and downstream of the second AC drift tube; and
An AC voltage assembly comprising:
a first AC voltage source coupled to deliver a first AC voltage signal at a first frequency to the first AC drift tube; and
a second AC voltage source coupled to deliver a second AC voltage signal at a second frequency to the second AC drift tube, the second frequency comprising an integer multiple of the first frequency ; and
and a linear accelerator disposed downstream of the collector for receiving and accelerating the focused ion beam.
An ion implantation system comprising:
an ion source for generating a continuous ion beam;
a collector disposed downstream of the ion source to receive the continuous ion beam and output a focused ion beam, the collector comprising:
a first AC drift tube for receiving a first AC signal at a first frequency; and
the collector comprising a second AC drift tube disposed downstream of the first AC drift tube for receiving a second AC signal at a second frequency that is an integer multiple of the first frequency; and
and a linear accelerator disposed downstream of the collector for receiving and accelerating the focused ion beam.
13. The method of claim 12,
The ion implantation system,
a first grounded drift tube disposed upstream of the first AC drift tube;
an intermediate grounded drift tube arranged downstream of the first AC drift tube; and
and a second grounded drift tube disposed adjacent the second AC drift tube and downstream of the second AC drift tube.

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