Cyclotron with continuously variable energy output.

Abstract

The apparatus may include a cyclotron for receiving the ion beam as an incident ion beam at an initial energy and outputting the ion beam as an accelerated ion beam at an accelerated ion energy. The apparatus may further include an RF source for outputting an RF power signal to the cyclotron chamber, the RF source including a variable power amplifier, and a movable stripper translatable to block the ion beam in the cyclotron at a series of different positions.

Description

[Technical field]

[0001] Related Applications This application claims priority to U.S. Nonprovisional Patent Application No. 17 / 560,632, entitled “CYCLOTRON HAVING CONTINUOUSLY VARIABLE ENERGY OUTPUT,” filed December 23, 2021, which is incorporated by reference in its entirety herein.

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

[0003] Ion implantation is a process that introduces dopants or impurities into a substrate by bombardment. An ion implantation system may consist of an ion source and a series of beamline components. The ion source may include a chamber in which ions are generated. The beamline components may include, for example, a mass analyzer, a collimator, and various components for accelerating or decelerating the ion beam. Just like a series of optical lenses for manipulating a beam of light, these beamline components are capable of filtering, focusing, and manipulating the ion beam with a particular species, shape, energy, and / or other quality. The ion beam passes through the beamline components and may be directed to a substrate mounted on a platen or clamp.

[0004] For high energy ion implantation, both tandem and linear accelerators have been implemented in beamline ion implanters to generate high energy ions, e.g., above 1 MeV. Cyclotrons are another component that offer an attractive approach to generate high energy ion beams. Among the several types of cyclotrons developed in the field of high energy physics, isochronous cyclotrons operating in continuous wave mode are attractive for applications in the semiconductor industry. Isochronous cyclotrons can be placed very compactly (less than 2 m between the ends of the main magnet), can achieve high energies (5 MeV for protons), and can deliver very high average beam currents (up to several mA).

[0005] One drawback of known isochronous cyclotrons is that they generally operate with only one output energy, i.e., the energy at which ions reach the outer radius of the main magnet and are extracted by dedicated electrodes or magnets. To generate variable energy outputs, several solutions have been developed. Currently, these approaches generate either (1) discrete energy steps of extracted ion energy (where the magnitude of each step is the kinetic energy gain per revolution) or (2) extracted ion beams with a wide range of energies. While these two results are acceptable for isotope production and other commercial applications where this technology is applied, they are not compatible with the requirements of semiconductor manufacturing, where very tight beam control and repeatability are often required.

[0006] It is with respect to these and other considerations that the present disclosure is presented. Summary of the Invention

[0007] In one embodiment, an apparatus is provided that may include a cyclotron that receives an ion beam of initial energy as an incident ion beam and outputs an ion beam of accelerated ion energy as an accelerated ion beam, and may further include an RF source that outputs an RF power signal to the cyclotron that includes a variable power amplifier, and a movable stripper that is translatable to block the ion beam in the cyclotron at various positions in a sequence.

[0008] In another embodiment, an ion implanter is provided that may include an ion source for generating a negative ion beam having an initial ion energy, and a cyclotron for receiving the negative ion beam as an incident ion beam at an incident ion energy and outputting the negative ion beam as a positive ion beam at an accelerated ion energy, the ion implanter including an RF power supply for outputting an RF power signal to the cyclotron with a variable power amplifier, and a movable stripper translatable to block the ion beam in the cyclotron at a series of different positions.

[0009] In a further embodiment, a method of generating a high energy ion beam may include generating a negative ion beam having an initial ion energy and accelerating the negative ion beam in a cyclotron chamber of a cyclotron, the method may include stripping the negative ion beam to generate a positive ion beam by positioning a movable stripper in a predetermined orbit within the cyclotron chamber, and adjusting an amplitude of an RF voltage applied to the cyclotron. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1 illustrates an exemplary ion implantation system in accordance with an embodiment of the present disclosure. [Figure 1B] FIG. 1 illustrates a variation of a cyclotron according to an embodiment of the present disclosure. [Diagram 2]FIG. 1 illustrates another variation of a cyclotron according to some embodiments of the present disclosure. [Figure 3A] FIG. 2 illustrates a cyclotron magnet according to an embodiment of the present disclosure. [Figure 3B] FIG. 3B illustrates the shape of the equilibrium orbit generated by the cyclotron magnet of FIG. 3A in accordance with an embodiment of the present disclosure. [Figure 4A] FIG. 2 illustrates the average cyclotron orbit radius and radial spacing of adjacent cyclotron orbits for a set of cyclotron orbits versus ion energy according to one embodiment of the present disclosure. [Figure 4B] FIG. 4B shows the same average cyclotron radius versus ion energy for the conditions of FIG. 4A and the relative energy change between one cyclotron orbit and an adjacent cyclotron orbit. [Diagram 5] FIG. 1 illustrates the use of a composite RF signal to achieve uniform acceleration of ions in a cyclotron according to one embodiment of the present disclosure. [Figure 6] FIG. 1 illustrates an exemplary process flow diagram according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The drawings are not necessarily to scale. The drawings are merely representative and are not intended to illustrate specific parameters of the present disclosure. The drawings are intended to illustrate exemplary embodiments of the present disclosure and therefore should not be considered limiting in scope. In these drawings, like numbers indicate like elements.

[0012] The apparatus, systems, and methods according to the present disclosure will now be described in more detail with reference to the accompanying drawings, in which embodiments of the systems and methods are shown. The systems and methods may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are presented so that this disclosure will be thorough and complete, and will fully convey the scope of these systems and methods to those skilled in the art.

[0013] As used herein, elements or operations described in the singular and preceded by the words "a" or "an" are understood to potentially include a plurality of elements or operations. Furthermore, references to "one embodiment" in the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features.

[0014] Provided herein is an approach for an improved high energy ion implantation system based on a cyclotron architecture. For simplicity, the ion implantation system may also be referred to herein as an "ion implanter." Various embodiments present novel configurations for achieving the capability of generating high energy ions with final ion energies delivered to a substrate that can be 300 keV, 500 keV, 1 MeV, 2 MeV, 5 MeV, or higher. In an exemplary embodiment, a novel cyclotron assembly is used to process the ion beam in a manner that facilitates the generation of a monoenergetic ion beam accelerated to high energies, where the energy of the monoenergetic ion beam is continuously variable.

[0015] 1A, an exemplary ion implanter, designated as ion implanter system 100, is shown in block form. Ion implanter system 100 may correspond to a beamline ion implanter, with some elements omitted for clarity of illustration. Ion implanter system 100 may include an ion source 102 for generating an ion beam 104 at a first ion energy. According to various non-limiting embodiments of the present disclosure, ion source 102 is a negative ion source as known in the art, with various components omitted. Examples of ion energies suitable for the first ion energy range from 5 keV to 100 keV, although embodiments are not limited to this condition. According to certain non-limiting embodiments, ion source 102 generates a negative hydrogen ion beam (H - ) to generate ion species such as ions from a source of negative hydrogen ions. To form a high energy ion beam, the ion implantation system 100 includes various additional components for accelerating the ion beam 104.

[0016] The ion implantation system 100 further comprises an injection assembly 103 (discussed further below) for injecting the ion beam 104 into a cyclotron assembly 120, which is used to accelerate the ion beam 104 and output a high-energy ion beam 112. According to various embodiments, the high-energy ion beam 112 may be a positive ion beam. As such, the cyclotron assembly 120 may function to accelerate the ion beam 104 and strip electrons from negative ions of the ion beam 104 to generate positive ions. In one example, the ion beam 104 is injected into an incident H - The high energy ion beam 112 is H + The high energy ion beam 112 is then sent through various downstream beamline elements 115 that may direct, shape, or scan the beam depending on the tool's architecture before it reaches the substrate 117.

[0017] It should be noted that the injection assembly 103 may include an injection device (not shown separately), as is known in the art, that is used to redirect the ion beam 104 from along the y-axis into the transverse acceleration plane, i.e., the xz-plane.

[0018] As shown in FIG. 1A, the cyclotron assembly 120 may include a cyclotron 106 that receives the ion beam 104 as a negative ion beam at an exit energy, referred to herein as the "entered ion energy." The cyclotron 106 may serve to accelerate, convert, and output the ion beam 104 as a positive ion beam, shown as the energetic ion beam 112 at an accelerated ion energy. The cyclotron assembly 120 may also include an RF power supply 108 for outputting an RF power signal 116 to the cyclotron 106. The RF power signal 116 may be applied to a dee located within the cyclotron 106, the operation of which will be described in more detail below. In brief, the dee may be a curved counter electrode that receives the RF power signal and cooperates with the cyclotron magnet to accelerate the ion beam 104 in a helical trajectory (as used herein, the term "trajectory" generally refers to the cyclotron trajectory unless otherwise indicated) in accordance with generally known cyclotron principles.

[0019] According to various embodiments of the present disclosure, the RF power supply 108 may include a variable power amplifier capable of continuously varying the amplitude of the voltage of the RF power signal 116. Thus, the energy of the accelerated ion beam, i.e., the high-energy ion beam 112, may be continuously varied. With further reference to FIG. 1B, which illustrates a variation of the cyclotron 106, the ion beam 104 is accelerated in the cyclotron 106. The cyclotron path 114 of the ion beam 104 defines a helical shape characterized by one or more trajectories of increasing beam radius or diameter as shown. Thus, at a given angular position, the ion energy between adjacent trajectories increases stepwise, as will be described in more detail below. By providing a variable power amplifier, the voltage of the RF power signal 116 may be changed from an unadjusted RF peak voltage to an adjusted RF peak voltage, such that an intermediate energy may be imparted to the ion beam 104. In this case, the intermediate energy is between the ion energies imparted to the ion beam 104 of adjacent trajectories using the unadjusted RF peak voltage. In other words, the RF peak voltage can be continuously varied to allow for continuous adjustment of ion energy from the lowest ion energy at the innermost orbital position to the highest ion energy at the outermost orbital position, which in some embodiments can span 2 MeV, 4 MeV, 6 MeV, or more.

[0020] As used herein, according to some embodiments, the term "continuously variable" in relation to ion energy means that between a given energy Emin and a second energy Emax, an ion beam can be repeatedly extracted from a cyclotron at any desired energy E between Emin and Emax, within a range of dE, by utilizing components, systems, and methods as detailed herein. It should be noted that the value of dE can be arbitrarily small depending on the resolution to which the RF voltage is controlled using a control system with appropriate feedback.

[0021] As shown particularly in FIG. 1B, the cyclotron 106 includes a cyclotron chamber 118 and a movable stripper 110 that is translatable within the cyclotron chamber 118 to block multiple cyclotron orbits at multiple radial positions relative to the central axis of the cyclotron 106. The movable stripper 110 can convert an incoming negative ion beam at position 122 into an exiting positive ion beam at the top right. In this case, the position of the movable stripper 110 relative to the cyclotron path 114 will determine the energy of the exiting or energetic ion beam 112. The movable stripper 110 may be formed from a thin conductive sheet or foil, such as graphite foil. It is noted that the shape of the dee 123 may vary according to different embodiments and is shown in a simplified configuration in FIG. 1B.

[0022] Referring to FIG. 2, a variation of the cyclotron 106 according to some embodiments is shown. In this example, the cyclotron 106 comprises a cyclotron chamber 202, with multiple cyclotron orbits shown as cyclotron orbits 204. A movable stripper 206 is shown, and multiple ion beam paths for the exiting ion beam are shown as ion beam paths 210. The ion beam paths 210 correspond to the initial orbits of the positive ions stripped from different orbits of the cyclotron orbits 204. By positioning the movable stripper 206 in different orbits, the energy of the exiting ion beam can be changed in stepwise energy increments. In this case, the size of the energy step is defined by the energy that the ions gain as they travel one orbit through the acceleration field. The exact position of the movable stripper 206 can be adjusted so that all the ion beam paths 210 intersect at a predetermined position C outside the main cyclotron magnet 107. To guide the exiting ion beam in a uniform direction, a dipole coupled magnet 212 is provided as shown in the figure. The dipole coupled magnets 212 may be electromagnets. The current applied to the dipole coupled magnets 212 may be accordingly adjustable to send the accelerated ion beam 214 along a common beamline axis (illustrated as the Z-axis) regardless of the ion energies and initial trajectories of the stripped positive ion beams represented by the various paths of the ion beam path 210.

[0023] As previously mentioned, the RF power applied to the dees 123 (see FIG. 1B) may be varied to obtain ion energies between the discrete energy increments generated by moving the movable stripper 206 from one cyclotron orbit to another. For example, to provide ion energies for the high energy ion beam 112 in the range of about 1 MeV to 7 MeV, the energy step between adjacent cyclotron orbits is less than 20%. Thus, in some embodiments, the RF power applied between the dees 123 may vary by up to ±20%, which results in a change in the dee voltage by ±10%, thus spanning the energy increment between any two adjacent cyclotron orbits. Careful positioning and adjustment of the stripper foil of the movable stripper 110 allows the innermost edge of the movable stripper 206 to be positioned between these cyclotron orbits. It should be noted that according to some embodiments, the stripper foil may be positioned approximately perpendicular to the ion beam propagation direction, as in known cyclotrons, and may have a suitable thickness, such as in the range of 100 μm. Furthermore, changes in the exit energy of the ion beam 104 or the focusing and deflection of the exit beam (ion beam 104) may be required. Since the perturbations are moderate (10%), this result may be easily achieved by readjusting these energy, focusing, and deflection parameters to maximize the ion beam transmission.

[0024] Unlike known cyclotron configurations, according to various embodiments of the present disclosure, the movable stripper 110 or the movable stripper 206 may be continuously translatable to intercept the ion beam in the cyclotron at a continuous variety of positions. This continuous movement of the movable stripper, in combination with the continuous change in the voltage amplitude of the RF power signal 116, facilitates the ability to suitably extract the accelerated ion beam from the cyclotron at a continuously variable ion energy over a wide range of ion energies. Thus, as the amplitude of a given RF voltage signal is adjusted, the position of the helical trajectory of the ion beam in the cyclotron chamber will change for a constant magnetic field. Because the movable stripper may be continuously translated over a continuous range of positions, the position of the movable stripper may be adjusted to precisely match the position of the ion beam on the cyclotron trajectory corresponding to the ion energy of interest to be extracted from the cyclotron.

[0025] Similar to known cyclotrons, and in accordance with embodiments of the present disclosure, the cyclotron 106 or similar cyclotrons include a cyclotron magnet (not shown in FIGS. 1A-1B) for generating a cyclotron trajectory of the ion beam 104 in combination with an applied RF voltage. While the exact shape of the cyclotron magnet or magnet assembly may vary, any such magnet may generate a magnetic field that extends approximately perpendicular to the electric field generated by the dee. FIG. 3A illustrates a cyclotron magnet 300 in accordance with an embodiment of the present disclosure. The cyclotron magnet 300 may be suitable for operation in a variation of the cyclotron 106 in which the dee has a different shape than the variation of FIG. 1B. In this variation, the cyclotron magnet 300 has a circular configuration with four high magnetic field regions, illustrated as high magnetic field regions 302, and multiple low magnetic field regions, illustrated as low magnetic field regions 304. The low magnetic field regions 304 are alternately disposed between the high magnetic field regions 302 along a circular arc. In this embodiment, a pair of energized dees may be positioned within a "pocket" defined by the low magnetic field regions 304. Specifically, a first energized dee may be disposed in a first low magnetic field region 304A of the low magnetic field regions 304, and a second energized dee may be disposed in a second low magnetic field region 304B of the low magnetic field regions 304 located on the opposite side of the first low magnetic field region 304A. According to various embodiments of the present disclosure, the other two pockets formed by the low magnetic field regions 304 may be used for housing diagnostic components and a movable stripper used to extract the ion beam. For example, the low magnetic field region 304C may be used to house the movable stripper 110, and the low magnetic field region 304D may be used to house diagnostic components. According to some embodiments, the pockets formed by the first low magnetic field region 304A and the second low magnetic field region 304B may each occupy an arc of about 45 degrees, and thus the first powered dee and the second powered dee may each occupy a similar arc of about 45 degrees when positioned within these low magnetic field regions.

[0026] The effect of this geometry is to achieve greater focusing by alternating magnetic field strength using four high magnetic field regions in each cyclotron orbit and two powered dees located in low magnetic field "pockets". In some embodiments, the diameter of the resulting ion beam in the cyclotron is equal to or less than the orbital spacing between adjacent cyclotron orbits. In this manner, a monoenergetic ion beam can be extracted from the cyclotron 106 by carefully placing the movable stripper 110 to strip off only ions from the ion beam in selected cyclotron orbits. EXAMPLES

[0027] According to some examples, the incident ion energy (exit energy of the ion beam into the cyclotron) may be between 10 keV and 100 keV, and the RF power signal applied to the dees in the cyclotron may have a peak voltage of 25 kV to 100 kV. Figure 3B shows an orbital geometry within a cyclotron chamber 310 utilizing a magnet configuration similar to that of Figure 3A. The ion exit energy is 30 keV, but the peak amplitude (Vp) of the RF voltage applied between the dees is 55 kV, resulting in an energy increment or energy step between adjacent orbits of 220 keV. Specifically, FIG. 3B shows the shape of stable orbits 312, which have an average radius r, calculated by r=mv / qB (where m is the mass of the ion, v is the velocity of the ion, q is the unit charge of the ion, and B is the strength of the magnetic field. In SI units, m is in kilograms, v is in meters / second, q is in coulombs, B is in teslas, and r is in meters). Note that the detailed shape of the stable orbits alternates between four regions with smaller radii and four regions with larger radii. Note that these stable orbits are the result of simultaneous radial and axial focusing, and there is no resonance between the acceleration frequency and the oscillation frequency of the ions in the focusing field.

[0028] 4A shows the calculated average cyclotron orbit radius and the radial spacing of adjacent cyclotron orbits for a series of cyclotron orbits for ion energies of positive hydrogen ions in a cyclotron magnetic field of 1.3 T. Again, the ion ejection energy is set to 50 keV and the peak amplitude (Vp) of the RF voltage applied between the dees is 55 kV, resulting in an energy increment between adjacent orbits of 220 keV. Note that even at very high energies, the spacing between adjacent orbits remains greater than about 4 mm.

[0029] Figure 4B shows the same average cyclotron radius versus ion energy for the conditions of Figure 4A, but now the right axis shows the relative energy change between one cyclotron orbit and an adjacent cyclotron orbit. Note that for ion energies above 1 MeV, the energy step between adjacent orbits is less than 20%, and for ion energies above 2 MeV, the energy step between adjacent orbits is less than 10%.

[0030] According to various embodiments of the present disclosure, a DC (continuous) ion beam is fed into a cyclotron, which allows the cyclotron to accept a portion of the DC ion beam into its acceleration scheme. The remainder of the continuous ion beam impinges on internal beamline components and is not accelerated by the cyclotron. In this way, the cyclotron acts as an inherent buncher to generate ion bunches.

[0031] It should be noted that since the ion bunch will necessarily spread over a length of its orbit while traversing the cyclotron path, and the RF accelerating field applied to the ion bunch will spread over a range, the acceleration of the ion bunch while traversing the gap between the powered electrode and ground will be somewhat non-uniform, or vice versa. To address this issue, according to some embodiments, a composite RF signal may be used to drive the dee of the cyclotron, where the composite RF signal includes a first signal having a first frequency and a second signal having a second frequency, the second frequency being a harmonic of the first frequency. Due to symmetry requirements in the time domain, odd harmonic frequencies are useful for the second frequency, with the third harmonic frequency contributing most to the generation of the composite signal. In other embodiments, adding a portion of the fifth harmonic as a second signal may also be useful to generate a suitable composite RF signal, while in theory adding the seventh and / or ninth harmonic to the fundamental RF signal as additional RF signals may also be employed, but in this case with less impact on the composite RF signal.

[0032] FIG. 5 illustrates the use of a composite RF signal to achieve uniform acceleration of ions in a cyclotron according to one embodiment of the present disclosure. In this example, a first RF signal is generated as shown by curve 502. Curve 502 is a sinusoid corresponding to an applied voltage signal with an amplitude shown as sin(t). A second RF signal is generated as shown by curve 504. Curve 504 is another sinusoid corresponding to an applied voltage signal with an amplitude shown as 0.131 sin(3t). A second RF signal is generated as shown by curve 504. These two RF signals are synchronized such that each zero point of curve 502 corresponds to a zero point of curve 504. Thus, a composite RF signal is generated (the sum of curves 502 and 504) as shown by curve 506. Curve 506 is no longer an ideal sinusoidal shape and may be characterized as having a flat upper region for approximately 1 / 3 of a cycle as shown. Specifically, by adding 0.13 of the amplitude of the first harmonic (sin(t)) to the third harmonic (sin(3t)), it is possible to uniformly accelerate the entire ion bunch to within 0.2%.

[0033] The result of the embodiment of FIG. 5 is that each cyclotron orbit can have only one energy at any given angular position, and therefore can be separated from adjacent cyclotron orbits if the phase space distribution and emittance of the ion source ejection beam are small enough and the increase in emittance is minimized by properly matching the ejection ion source beam to the cyclotron acceptance ellipse in phase space. Using these design parameters, the spacing between adjacent cyclotron orbits is greater than 5 mm. Note that, according to the embodiment described above, the magnetic field design allows the beam size to be smaller than the 5 mm orbit spacing, so that the ion orbits are reversed in their curvature by inserting a movable stripper foil to convert the ejected ions from negative to positive ions and emerge from the main magnet. The position of the movable stripper foil can be carefully adjusted so that all of the positive ion orbits of different energies intersect at a point outside the main cyclotron magnet. As previously mentioned, in this position, a single dipole coupled magnet can be used to direct the ion beam towards downstream beamline elements that can steer, shape or scan the beam depending on the tool architecture.

[0034] It should be noted that various components of the ejection assembly 103, such as the inflector (not shown separately), may be appropriately adjusted to maintain a target ion beam size, such as less than 5 mm spacing between adjacent orbits. In general, these ejection assembly components will be adjusted (tuned) to focus and direct the ion beam into a cyclotron, such as cyclotron 106, and to match the size, shape, and direction of the ejected ion beam's phase space distribution as closely as possible to the cyclotron's acceptance ellipse. As is known in the art, these acceptance ellipses are effectively intrinsic ellipses that can be obtained by backtracking the desired extracted beam characteristics from the extraction foil position to a position at or near the inflector exit using an appropriate computer model. This procedure will serve to keep the ejection ion source's phase space ellipse aligned to the shape / orientation of the acceptance ellipse at or near the inflector exit. Alternatively, if the phase space ellipse of the ejection ion source is not well aligned with respect to the shape / orientation of the acceptance ellipse at or near the inflector exit, the phase space distribution of the beam in each phase slice of the accelerated beam pulse may grow significantly in the cyclotron. This misalignment condition may result in the beam size in each phase slice of the beam pulse being larger than the desired spacing, e.g., 5 mm, between adjacent trajectories.

[0035] In some examples, components including a collimator and scraper are provided in the cyclotron 106 to prevent the phase width of the beam pulse from becoming larger than the flat region of the curve 506 shown in Figure 5. These components are positioned to carefully trim the beam pulse of the ion beam while the ion beam is in the first or second orbit (i.e., the innermost orbit) of a cyclotron such as the cyclotron 106. Still referring to Figure 1A, in some embodiments, a controller 105 or control system may be provided to perform beam pulse trimming using a feedback loop to ensure that the tail of the beam pulse is properly removed and a "flat" beam pulse is generated in a phase angle range that falls within the flat region of the generated RF waveform.

[0036] As mentioned above, to obtain an ion energy intermediate between the energy "steps" generated in adjacent trajectories, the RF power applied to the dee may be changed to effect some combination of adjusting the position of the movable stripper, changing the ion ejection energy, and focusing or deflecting the ion beam, but in any of these scenarios the movable stripper may be positioned to intercept a given trajectory of the ion beam having monoenergetic ions.

[0037] 6 illustrates an exemplary process flow 600 according to some embodiments of the present disclosure. In block 602, an ion beam is generated, such as by extraction from an ion source, as a negative ion beam. As such, the ion beam may exhibit ion energies in the range of 10 keV to 100 keV according to some non-limiting embodiments. In some embodiments, the negative ion beam may be a hydrogen negative ion beam.

[0038] At block 604, a negative ion beam is received into a cyclotron chamber of a cyclotron. According to some embodiments, the negative ion beam may be ejected axially into the cyclotron chamber along a central axis of the cyclotron chamber.

[0039] In block 606, the negative ion beam is accelerated through one or more cyclotron tracks in the cyclotron chamber. According to some embodiments, the ion beam may be accelerated by applying an RF power signal at a suitable peak voltage, such as a peak voltage of 25 kV to 100 kV, to a pair of dees in the cyclotron chamber. The tracks may be separated from each other by a suitable distance, such as at least a few millimeters, in combination with application of a magnetic field of suitable strength, such as 1 T, 1.2 T, and 1.4 T.

[0040] In block 608, a movable stripper is placed in a suitable orbit within the cyclotron chamber to convert the negative ion beam into a positive ion beam and extract the positive ion beam. The movable stripper may be configured as a suitable conductive foil.

[0041] The amplitude of the RF power signal applied to a pair of dees of the cyclotron is adjusted in block 610. The operation in block 610 is performed to adjust the energy of the positive ion beam extracted from the cyclotron because the energy between adjacent orbits can increase in increments of a few percent to as much as 20 percent depending on the ion energy.

[0042] In block 612, the current to the coupled dipole magnets is adjusted to direct any of the extracted trajectories onto the common beamline axis.

[0043] In view of the foregoing, at least the following advantages are achieved by the embodiments disclosed herein. The first advantage is realized by providing an approach to generate energetic ions with continuously variable energy using a cyclotron. The second advantage is provided by various embodiments in which the energy of the ions extracted from the cyclotron is monochromatic, which may eliminate the need for beamline components such as energy analyzers. The embodiments provide further advantages in semiconductor processing conditions. For example, the continuously variable energy of the extracted ions according to the embodiments may allow for careful adjustment of the implantation depth of the implanted ions. Furthermore, generating a monochromatic ion beam, e.g., a monochromatic positive ion beam, according to the embodiments allows for precise scanning and collimation of the ion beam.

[0044] Although specific embodiments of the present disclosure have been described herein, the present disclosure is not limited thereto. Because the scope of the present disclosure is as broad as the art permits, the present specification can be interpreted in the same manner. Therefore, the above description should not be interpreted as limiting. Other modifications within the scope and spirit of the claims appended hereto will occur to those skilled in the art.

Claims

1. a cyclotron for receiving an ion beam as an incident ion beam with an initial energy and outputting the ion beam as an accelerated ion beam with an accelerated ion energy; an RF source for outputting an RF power signal to the cyclotron, the RF source comprising a variable power amplifier; a movable stripper translatable to intercept the ion beam within the cyclotron at a succession of different positions; An apparatus comprising:

2. The apparatus of claim 1 , wherein the incident ion beam comprises a beam of negative hydrogen ions and the accelerated ion beam comprises a beam of protons.

3. The cyclotron is a cyclotron chamber, the movable stripper being translatable within the cyclotron chamber to intercept a plurality of cyclotron orbits located at a plurality of radial positions relative to a central axis of the cyclotron; The apparatus of claim 1 further comprising:

4. the cyclotron further comprising a cyclotron magnet in communication with the RF source to generate the plurality of cyclotron orbits; the plurality of cyclotron orbits are characterized by an orbital spacing between adjacent cyclotron orbits; The apparatus of claim 3 , wherein a beam diameter of the ion beam is less than or equal to a minimum of the orbital spacing of the plurality of cyclotron orbits.

5. 2. The apparatus of claim 1, further comprising a cyclotron magnet, the cyclotron magnet comprising a circular configuration having four high magnetic field regions and a plurality of low magnetic field regions, the plurality of low magnetic field regions being disposed alternating between the high magnetic field regions along a circular arc.

6. 6. The apparatus of claim 5, further comprising: a first powered dee disposed in a first low magnetic field region of the plurality of low magnetic field regions and a second powered dee disposed in a second low magnetic field region of the plurality of low magnetic field regions on an opposing side of the first low magnetic field region, the first powered dee and the second powered dee being coupled to receive the RF power signal.

7. 7. The apparatus of claim 6, wherein the first powered dee and the second powered dee are positioned to each occupy an arc of approximately 45 degrees.

8. 2. The apparatus of claim 1, wherein the RF power signal comprises a composite signal comprising a first signal having a first frequency and a second signal having a second frequency, the second frequency being an odd harmonic of the first frequency.

9. an ion source for generating a beam of negative ions, the beam having an initial ion energy; a cyclotron for receiving the negative ion beam as an incident ion beam with an incident ion energy and outputting the negative ion beam as a positive ion beam with an accelerated ion energy; an RF power supply for outputting an RF power signal to the cyclotron, the RF power supply comprising a variable power amplifier; a movable stripper translatable to intercept the ion beam within the cyclotron at a succession of different positions; An ion implantation apparatus comprising:

10. The cyclotron is a cyclotron chamber, the movable stripper being translatable within the cyclotron chamber to intercept a plurality of cyclotron orbits located at a plurality of radial positions relative to a central axis of the cyclotron; 10. The ion implanter of claim 9, further comprising:

11. 11. The ion implanter of claim 10, wherein the cyclotron further comprises a cyclotron magnet in communication with the RF source to generate a plurality of cyclotron orbits, the plurality of cyclotron orbits being characterized by an orbital spacing between adjacent cyclotron orbits, and a beam diameter of the ion beam being less than or equal to a minimum of the orbital spacing of the plurality of cyclotron orbits.

12. 10. The ion implanter of claim 9, further comprising a cyclotron magnet, the cyclotron magnet comprising a circular configuration having four high magnetic field regions and a plurality of low magnetic field regions, the plurality of low magnetic field regions being disposed alternatingly between the high magnetic field regions along a circular arc.

13. 13. The ion implanter of claim 12, further comprising a first powered dee disposed in a first low magnetic field region of the plurality of low magnetic field regions and a second powered dee disposed in a second low magnetic field region of the plurality of low magnetic field regions on an opposing side of the first low magnetic field region, the first powered dee and the second powered dee being coupled to receive the RF power signal.

14. 14. The ion implanter of claim 13, wherein the first powered dee and the second powered dee are positioned to each occupy an arc of approximately 45 degrees.

15. 10. The ion implanter of claim 9, wherein the incident ion energy is between 10 keV and 100 keV and the RF power signal has a peak voltage of between 25 kV and 100 kV.

16. 10. The ion implanter of claim 9, wherein the RF power signal comprises a composite signal comprising a first signal having a first frequency and a second signal having a second frequency, the second frequency being a harmonic of the first frequency.

17. 1. A method for generating a high energy ion beam, comprising: generating a negative ion beam having an initial ion energy; accelerating the negative ion beam in a cyclotron chamber of a cyclotron; stripping the negative ion beam to generate a positive ion beam by disposing a movable stripper in a predetermined orbit within the cyclotron chamber; adjusting the amplitude of an RF voltage applied to the cyclotron; A method comprising:

18. 18. The method of claim 17, wherein the initial ion energy is between 10 keV and 100 keV, and accelerating the negative ion beam includes applying an RF power signal to a pair of dees in the cyclotron at a peak voltage of 25 kV to 100 kV.

19. 20. The method of claim 18, wherein the RF power signal comprises a composite signal comprising a first signal having a first frequency and a second signal having a second frequency, the second frequency being a harmonic of the first frequency.

20. the movable stripper is translatable to intercept the negative ion beam in the cyclotron at a succession of different positions; 20. The method of claim 17, wherein a monoenergetic positive ion beam is generated with continuously adjustable ion energy.

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