High aspect ratio beam dump or faraday cup with neutron radiation shielding

Abstract

A neutron shielding apparatus has a shield member made of a neutron attenuation material. The shield member has a cavity defining an entrance with an entrance width for accepting an ion beam along a beam path. A target structure intercepts the ion beam within the cavity at a predetermined distance from the entrance, where the predetermined distance is greater than approximately one-half the entrance width, and where the ion beam emits neutron radiation in all directions. The neutron attenuation material attenuates the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure. The cavity can be a blind hole extending a predetermined depth from the entrance, or a passageway extending through the shield member defining the entrance and an exit. A positioning apparatus can selectively position the target structure at a target position within the cavity.

Description

[0001] HIGH ASPECT RATIO BEAM DUMP OR FARADAY CUP WITH NEUTRON RADIATION SHIELDING

[0002] REFERENCE TO RELATED APPLICATIONS

[0003] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 637,430 filed April 23, 2024, entitled, “HIGH ASPECT RATIO BEAM DUMP OR FARADAY CUP WITH NEUTRON RADIATION SHIELDING”, the contents of all of which are herein incorporated by reference in their entirety.

[0004] TECHNICAL FIELD

[0005] The present invention relates generally to high energy ion implantation systems, and more specifically to a beam dump or faraday cup having shielding to minimize exposure from an operator to neutron radiation.

[0006] BACKGROUND

[0007] In the manufacture of semiconductor devices, ion implantation is used to dope semiconductors with impurities. Ion implantation systems are often utilized to dope a workpiece, such as a semiconductor wafer, with ions from an ion beam, in order to either produce n- or p-type material doping, or to form passivation layers during fabrication of an integrated circuit. Such beam treatment is often used to selectively implant the wafers with impurities of a specified dopant material, at a predetermined energy level, and in controlled concentration, to produce a semiconductor material during fabrication of an integrated circuit. When used for doping semiconductor wafers, the ion implantation system injects a selected ion species into the workpiece to produce the desired extrinsic material. Implanting ions generated from source materials such as antimony, arsenic, or phosphorus, for example, results in an “n-type” extrinsic material wafer, whereas a “p-type” extrinsic material wafer often results from ions generated with source materials such as boron, gallium, or indium.

[0008] A typical ion implanter includes an ion source, an ion extraction device, a mass analysis device, a beam transport device and a wafer processing device. The ion source generates ions of desired atomic or molecular dopant species. These ions are extracted from the source by an extraction system, typically a set of electrodes, which energize and direct the flow of ions from the source, forming an ion beam. Desired ions are separated from the ion beam in a mass analysis device, typically a magnetic dipole performing mass dispersion or separation of the extracted ion beam. The beam transport device, typically a vacuum system containing a series of focusing devices, transports the ion beam to the wafer processing device while maintaining desired properties of the ion beam. Finally, semiconductor wafers are transferred in to and out of the wafer processing device via a wafer handling system, which may include one or more robotic arms, for placing a wafer to be treated in front of the ion beam and removing treated wafers from the ion implanter.

[0009] So-called high energy ion implanters can produce very high energy ion beams having substantial amounts of beam current. At such high energies, nuclear fusion can occur. High-energy boron ions having greater than 5MeV energy, for example, can tunnel through the Coulomb barrier of the target nuclei and fuse with either carbon nuclei of graphite liners of the end station, or fuse with other pre-implanted boron nuclei. Such a nuclear fusion reaction can result in high-energy neutrons, which are difficult to attenuate, since adequate shielding thicknesses can comprise ten to thirty or more inches of polyethylene or high-density concrete.

[0010] Additionally, measured neutron radiation shows a relatively shallow or weak angle dependence. As such, neutron shielding can lead to a substantial undesirable increase in footprint of high energy ion implanters, as clean room space is costly in which the ion implantation system is present. Conventional neutron shielding further limits or hampers serviceability of the system due to various limitations posed by the shielding, which can have a negative impact on uptime targets due to increased system maintenance times.

[0011] SUMMARY

[0012] The present disclosure provides a neutron shielding apparatus having a cavity or recess configured to limit radiation exposure beyond a predetermined periphery within an ion implantation system. The neutron shielding apparatus has a predetermined geometry associated with a Faraday cup and / or a beam dump, whereby shielding material, and therefore footprint, of an associated apparatus such as an end station is minimized while ensuring radiation safety limits (e.g., 30-60uRem / h) are met.

[0013] The following presents a simplified summary of the disclosure in order to provide a basic understanding of some aspects of the disclosure. This summary is not an extensive overview of the disclosure. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its purpose is to present some concepts of the disclosure in a simplified form as a prelude to the more detailed description that is presented later.

[0014] Aspects of the disclosure facilitate ion implantation processes for implanting ions into a workpiece. According to one exemplary aspect, an ion implantation system is provided having an ion source configured to form an ion beam, a beamline assembly configured to selectively transport the ion beam, and an end station is configured to accept the ion beam for implantation of the aluminum ions into a workpiece.

[0015] In accordance with one exemplary aspect of the disclosure, a neutron shielding apparatus for an ion implantation system is provided. The neutron shielding apparatus, for example, comprises a shield member comprising a neutron attenuation material. The shield member has a cavity defined therein, and wherein the cavity has an entrance configured to accept an ion beam along a beam path. A target structure is further positioned a first predetermined distance from the entrance within the cavity, wherein in one example, the target structure is configured to intercept the ion beam. The cavity, for example, defines an entrance width at the entrance of the cavity, wherein the first predetermined distance is greater than approximately one-half the entrance width.

[0016] The ion beam, for example, is configured to emit neutron radiation in all directions therefrom upon being intercepted by the target structure. The neutron attenuation material, for example, is configured to attenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure.

[0017] In one example, the cavity comprises a blind hole extending into the shield member a predetermined depth from the entrance, wherein the target structure is selectively positioned within the blind hole at approximately the predetermined depth. The neutron radiation, for example, can be emitted along a return path to the origin location, wherein the neutron attenuation material is not present along the return path. One or more upstream components can be positioned along the beam path at one or more upstream locations with respect to an origin location of the ion beam, and are configured to attenuate the neutron radiation to the predetermined radiation exposure limit at one or more upstream regions.

[0018] In another example, the cavity comprises a passageway extending through the shield member, thereby defining the entrance and an exit, wherein the target structure is selectively positioned at the first predetermined distance within the passageway. A positioning apparatus can be operably coupled to the target structure, wherein the positioning apparatus is configured to selectively position the target structure at a target position within the passageway, wherein the beam path intersects the target structure when the target structure is at the target position. The target structure, for example, can comprise a first side having a faraday cup and a second side having a graphite beam dump, and wherein the positioning apparatus is configured to selectively expose each of the first side and the second side of the target structure.

[0019] The shield member can comprise a recess, wherein the recess extends laterally outward from a sidewall of the passageway and away from the beam path. The positioning apparatus, for example, can comprise a translation apparatus configured to selectively translate the target structure between the target position and a retracted position within the recess.

[0020] In another example, the target structure comprises a beam passage defined therethrough, wherein the target structure is configured to selectively block the ion beam from passing through the beam passage based on a rotational orientation of the target structure with respect to the ion beam.

[0021] In accordance with another exemplary aspect of the disclosure, a neutron shielding apparatus comprises a shield member consisting of a neutron attenuation material. Th shield member, for example, has a cavity defined therein, wherein the cavity has an entrance configured to accept an ion beam along a beam path, wherein the entrance has an entrance width when viewed along the beam path. A target structure, for example, is positioned within the cavity at a predetermined distance from the entrance along the beam path, wherein the target structure is configured to intercept the ion beam. The ion beam, for example, is configured to emit neutron radiation in all directions therefrom upon being intercepted by the target structure, wherein the ion beam emanates generally linearly along the beam path toward the target structure from an origin location, and wherein the neutron attenuation material is configured to attenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure. The neutron attenuation material, for example, has a predetermined thickness associated with each of the one or more regions, respectively.

[0022] In one example, the cavity comprises blind hole extending into the shield member from the entrance, wherein the target structure is selectively positioned within the blind hole at approximately the predetermined distance, wherein the predetermined distance is greater than approximately one-half the entrance width.

[0023] In another example, the cavity comprises a passageway extending through the shield member, thereby defining the entrance and an exit of the cavity, wherein the target structure is selectively positioned at the predetermined distance within the passageway, and wherein the predetermined distance is greater than approximately one-half the entrance width.

[0024] In accordance with yet another exemplary aspect of the disclosure, a neutron shielding apparatus comprises a shield member consisting of a neutron attenuation material, wherein the shield member has a cavity defined therein, and wherein the cavity has an entrance configured to accept an ion beam along a beam path, wherein the entrance has an entrance width when viewed along the beam path. A target structure, for example, is positioned within the cavity at a predetermined distance from the entrance along the beam path, wherein the predetermined distance is greater than approximately one-half the entrance width, and wherein the target structure is configured to intercept the ion beam. The ion beam, for example, is configured to emit neutron radiation in all directions therefrom upon being intercepted by the target structure, wherein the ion beam emanates generally linearly along the beam path toward the target structure from an origin location, and wherein the neutron attenuation material is configured to attenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure, wherein the neutron attenuation material has a predetermined thickness associated with each of the one or more regions, respectively.

[0025] The above summary is merely intended to give a brief overview of some features of some embodiments of the present disclosure, and other embodiments may comprise additional and / or different features than the ones mentioned above. In particular, this summary is not to be construed to be limiting the scope of the present application. Thus, to the accomplishment of the foregoing and related ends, the disclosure comprises the features hereinafter described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the disclosure. These embodiments are indicative, however, of a few of the various ways in which the principles of the disclosure may be employed. Other objects, advantages and novel features of the disclosure will become apparent from the following detailed description of the disclosure when considered in conjunction with the drawings.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Fig. 1 is a schematic block diagram of another ion implantation system having a neutron shielding apparatus in accordance with several example aspects of the present disclosure.

[0028] Fig. 2A illustrates an example of an end station of an ion implantation system. Fig. 2B illustrates a close up view of the end station of Fig. 2A.

[0029] Fig. 2C illustrates a close up view of an alternative configuration illustrating a faraday in the end station of Fig. 2A.

[0030] Fig. 3 illustrates an end station for an ion implantation system having neutron shielding in accordance with various example aspects of the present disclosure.

[0031] Fig. 4 illustrates an end station for an ion implantation system having a neutron shielding apparatus in accordance with several example aspects of the present disclosure.

[0032] Fig. 5 illustrates a neutron shielding apparatus for an end station in accordance with several example aspects of the present disclosure. Fig. 6 illustrates another neutron shielding apparatus for an end station in accordance with several example aspects of the present disclosure.

[0033] Fig. 7 illustrates still another neutron shielding apparatus for an end station in accordance with several example aspects of the present disclosure.

[0034] Fig. 8A illustrates a neutron shielding apparatus for a movable faraday positioned along a beam path of an ion implantation system in accordance with several example aspects of the present disclosure.

[0035] Fig. 8B illustrates the neutron shielding apparatus of Fig. 8A having the movable faraday positioned outside of the beam path in accordance with several example aspects of the present disclosure.

[0036] Fig. 9A is a perspective view of a beam blocking apparatus in an open position in accordance with several example aspects of the present disclosure.

[0037] Fig. 9B is a perspective view of the beam blocking apparatus of Fig. 9A in a closed position in accordance with several example aspects of the present disclosure.

[0038] DETAILED DESCRIPTION

[0039] The present disclosure is directed generally toward an ion implantation system having a neutron shielding apparatus associated therewith. More particularly, the present disclosure is directed toward an enclosure for minimizing neutron radiation to various positions external to the ion implantation system. The present disclosure provides protection to operators of the ion implantation system from neutron radiation associated with a high energy ion beam impinging on a surface within the ion implantation system, such as impingement on a beam dump or faraday. Consequently, operator safety is increased due to decreased exposure to neutron radiation associated with the operation of the ion implantation system.

[0040] Accordingly, the present invention will now be described with reference to the drawings, wherein like reference numerals may be used to refer to like elements throughout. It is to be understood that the description of these aspects are merely illustrative and that they should not be interpreted in a limiting sense. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be evident to one skilled in the art, however, that the present invention may be practiced without these specific details. Further, the scope of the invention is not intended to be limited by the embodiments or examples described hereinafter with reference to the accompanying drawings, but is intended to be only limited by the appended claims and equivalents thereof.

[0041] It is also noted that the drawings are provided to give an illustration of some aspects of embodiments of the present disclosure and therefore are to be regarded as schematic only. In particular, the elements shown in the drawings are not necessarily to scale with each other, and the placement of various elements in the drawings is chosen to provide a clear understanding of the respective embodiment and is not to be construed as necessarily being a representation of the actual relative locations of the various components in implementations according to an embodiment of the invention. Furthermore, the features of the various embodiments and examples described herein may be combined with each other unless specifically noted otherwise.

[0042] It is also to be understood that in the following description, any direct connection or coupling between functional blocks, devices, components, circuit elements or other physical or functional units shown in the drawings or described herein could also be implemented by an indirect connection or coupling. Furthermore, it is to be appreciated that functional blocks or units shown in the drawings may be implemented as separate features or circuits in one embodiment, and may also or alternatively be fully or partially implemented in a common feature or circuit in another embodiment. For example, several functional blocks may be implemented as software running on a common processor, such as a signal processor. It is further to be understood that any connection which is described as being wire-based in the following specification may also be implemented as a wireless communication, unless noted to the contrary.

[0043] The present disclosure appreciates that higher energy ion beams are increasingly used in the fabrication of next-generation CMOS image sensors, such as ion beams comprised of relatively light species (e.g., boron ions) at energies of approximately 1 MeV to greater than 5 MeV. At such high energies, nuclear fusion can occur when the ion beam collides with carbon atoms (e.g., carbon in graphite liners within the ion implantation system), or with other ions previously implanted into a target (e.g., boron nuclei in the ion beam fusing with pre-implanted boron nuclei in a workpiece, beam dump, faraday, etc.), thus resulting in neutron radiation.

[0044] In order to gain a better appreciation of the disclosure, Fig. 1 illustrates an ion implantation system 100 in accordance with various exemplified aspects of the present disclosure. The ion implantation system 100 of Fig. 1 , for example, comprises a source chamber assembly 102, whereby the source chamber assembly comprises an ion source 104 and an extraction electrode 106 configured to extract and accelerate ions from the ion source to an intermediate energy, thereby forming a generated ion beam 108 along a beam path 110. A mass analyzing magnet 1 12, for example, mass analyzes the generated ion beam 108, thereby removing unwanted mass and charge ion species from the generated ion beam to define a first ion beam 114 (also called an analyzed ion beam) comprising desired ions at a first charge state (qi). A first linear accelerator 1 16 (also called a first LINAC), for example, is configured to accelerate the desired ions of the first ion beam 114 to a plurality of first energies. In accordance with one example of the present disclosure, the first LINAC 1 16 comprises an RF linear particle accelerator in which ions are accelerated repeatedly by an RF field. Alternatively, the first LINAC 116 comprises a DC accelerator (e.g., a tandem electrostatic accelerator), in which ions are accelerated with a stationary DC high voltage.

[0045] A charge stripper 1 18, for example, is further provided and configured to strip at least one electron from the desired ions of the first ion beam 1 14, thereby defining a second ion beam 120 comprising the desired ions at a plurality of second charge states or charge state distribution. In accordance with the present disclosure, a charge selector 122, for example, is further positioned downstream of the charge stripper 118 in order to select desired ions with a higher charge state after the stripping process.

[0046] The charge selector 122, for example, comprises a first dipole magnet 124, wherein the first dipole magnet is configured to bend the second ion beam 120, thereby spatially dispersing the second ion beam 120. A charge defining aperture 126 is positioned downstream of the first dipole magnet 124, wherein the charge defining aperture is configured to pass a desired charge state of the second ion beam 120 selected from the plurality of second charge states therethrough, while blocking a remainder of the plurality of second charge states of the second ion beam from passing therethrough.

[0047] The charge selector 122 further comprises a quadrupole apparatus 128 (e.g., a quadrupole magnet), for example, wherein the quadrupole apparatus is configured to spatially focus the second ion beam 120 to define a third ion beam 130 comprising the desired ions at the plurality of first energies and at the desired charge state (<72). A second dipole magnet 132 of the charge selector 122 is further configured to bend the third ion beam 130 and further direct the third ion beam to a second linear accelerator 134 in order to gain maximum energy that is higher than the original-charge state ions. For example, the second linear accelerator 134 can be configured to accelerate the desired ions of the third ion beam 130 to a plurality of second energies.

[0048] A final energy magnet 136, for example, is further provided, wherein the final energy magnet is configured to bend the third ion beam 130, whereby an energy defining aperture 138 of the final energy magnet, for example, is configured to pass only the desired ions at a desired energy therethrough, thereby defining a final ion beam 140 comprising the desired ions at the desired energy and desired charge state. The final energy magnet 136 is thus configured to remove unwanted energy spectrum from the accelerated third ion beam 130 emerging from the output of second linear accelerator 134 to define the final ion beam 140.

[0049] A beam scanner 142, for example, can be further provided and configured to scan the final ion beam 140 after exiting from the final energy magnet 136, whereby the final ion beam is scanned back and forth at a fast frequency to define a scanned ion beam 144. The beam scanner 142, for example, is configured to electrostatically or electromagnetically scan the final ion beam 140 to define a scanned ion beam 144.

[0050] The scanned ion beam 144 is further passed into an angle corrector lens 146, whereby the angle corrector lens 146, for example, can be configured to parallelize and shift the scanned ion beam 144 to define a parallelized final ion beam 148 for implantation into a workpiece 150 supported on a workpiece support 152. The angle corrector lens 146, for example, can comprise electromagnetic or electrostatic devices configured to shift and / or parallelize the scanned ion beam 144. The workpiece 150 (e.g., a semiconductor wafer) can be selectively positioned in a process chamber 154 associated with an end station 156 of the ion implantation system 100. In one example, the workpiece 150, for example, can be moved orthogonal to the parallelized final ion beam 148 (e.g., moving in and out of the paper) in a hybrid scan scheme to irradiate the entire surface of the workpiece 150 uniformly. It is noted that the present disclosure appreciates various other mechanisms and methods for scanning the final ion beam 140 with respect to the workpiece 150, and all such mechanisms and methods are contemplated as falling within the scope of the present disclosure.

[0051] A controller 158, for example, can be further provided to control one or more components of the ion implantation system 100, such as one or more of the ion source 104, mass analyzing magnet 112, first linear accelerator 116, charge selector 122, second linear accelerator 134, beam scanner 142, final energy magnet 136, and workpiece support 152.

[0052] The present disclosure contemplates the ion implantation system 100 as being useful for various next-generation semiconductor processing, such as for the formation of CMOS image sensors on the workpiece 150. For example, for such next-generation semiconductor processing, the ion implantation system 100 can be configured to implant boron ions at high energies (e.g., approximately 1 MeV to greater than 5 MeV) via the parallelized final ion beam 148. At such high energies, nuclear fusion can occur when the ion beam 108 travels along the beam path 1 10 and collides with carbon atoms (e.g., carbon in graphite liners within the ion implantation system), or with other ions previously implanted into a target 160 (e.g., boron nuclei in the ion beam fusing with pre-implanted boron nuclei in the target), thus resulting in neutron radiation 162. The target 160, for example, can comprise the workpiece 150, or a beam dump, faraday, etc., as will be discussed further infra.

[0053] While the end station 156 is illustrated as containing the target 160, the present disclosure contemplates the target being positioned anywhere along the beam path 1 10. For example, while the target 160 is illustrated in Fig. 1 as being positioned in a vacuum chamber 164 (e.g., the process chamber 154), the target may be alternatively positioned anywhere along the beam path 1 10, such as proximate to an entrance or exit of any of the ion source 104, mass analyzing magnet 112, first linear accelerator 1 16, charge selector 122, second linear accelerator 134, beam scanner 142, final energy magnet 136, etc.

[0054] In order to provide a more thorough understanding of the disclosure, Fig. 2A, for example, illustrates a vacuum chamber 210 having a target 212 positioned therein, whereby the vacuum chamber 210 is configured to receive an ion beam 214 e.g., a high energy ion beam), such as the ion beam 108 of Fig. 1 . Collisions of highly energized ions from the ion beam 214 with ions previously implanted into the target 212 of Fig. 2A, for example, can produce neutron radiation 216 (illustrated as dashed arrows) radiating in all directions from the target. An operator 218 (e.g., a human operator), for example, may be thus exposed to the neutron radiation 216, such as when passing near the vacuum chamber 210 while the ion beam 214 is striking the target 212.

[0055] The target 212 illustrated in Figs. 2A and 2B, for example, can comprise a beam dump 220 coupled to a chamber wall 222 of the vacuum chamber 210. In one example, the vacuum chamber 210 may comprise the process chamber 154 shown in Fig. 1 . As more particularly shown in Fig. 2B, the beam dump 220 may comprise a target material 224 (e.g., graphite) coupled to a back plate 226 (e.g., an aluminum plate), whereby the back plate is sealed to the chamber wall 222 by one or more O-rings 228 for vacuum sealing between the beam dump and the vacuum chamber 210. One or more cooling channels 230 defined within the back plate 226, for example, provide a passage of cooling fluid (e.g., water) therethrough to sufficiently cool the beam dump 220 due to the ion beam 214 impacting the target material 224, and thus protecting the back plate from being exposed to the high energy ion beam and protecting the one or more O-rings 228 from excess heating that could otherwise lead to a vacuum leak. The neutron radiation 216, for example, can be produced by fusing of the highly energized ions of the high energy ion beam 14 with carbon atoms of the target material 224 or with other previously implanted ions (e.g.,11B +12C -->22Na + n or11B +11B -->21Ne + n, typically denoted as12C(11B,n)22Na or11B(11B,n)21Ne in nuclear physics, respectively). Such neutron radiation 216, for example, is a result of a low atomic number (Z) of both the highly energized ions of the ion beam 214 and the target material 224, such as resulting from energies of approximately 4 MeV and higher of the high energy ion beam. Accordingly, the neutrons of the neutron radiation 216 interact weakly with the graphite and aluminum of the target material 224 and back plate 226, such that the target 212 is practically transparent to the neutron radiation.

[0056] Fig. 2C illustrates an alternative example of the end station of Fig. 2A, where the target 212 comprises a Faraday cup 232 configured to determine an ion beam current 234 (e.g., a number of ions) received (e.g., by the beam dump 220) from the ion beam 214. To measure the beam current accurately, the Faraday cup 232, for example, is further coupled to the chamber wall 222 with one or more insulators 236. The Faraday cup 232, for example, is further suppressed with magnets 238, or is otherwise provided with negatively biased electrodes or grids in order to suppress or prevent secondary electrons from escaping to prevent erroneous current measurements. Regardless, the target 212 comprising the Faraday cup 232 of Fig. 2C is also relatively transparent to the neutron radiation 216, as discussed above.

[0057] While lead (Pb) shielding is commonly used to attenuate x-ray radiation, lead shielding is relatively ineffective at attenuating the neutron radiation 216. As such, other shielding materials capable of shielding neutron radiation, such as polyethylene or high- density concrete having thicknesses on the order of tens of centimeters can be provided external to source locations of such radiation in order to meet radiation safety limits (e.g., 30-50 prem / h). Such thick neutron shielding, however, can possibly lead to a deleterious increase in footprint and limited serviceability, as clean room space is costly, and system maintenance is required to achieve the uptime targets set by semiconductor manufacturers.

[0058] In accordance with one example aspect, Fig. 3 illustrates a neutron shielding apparatus 240 operably coupled to the chamber wall 222 of the vacuum chamber 210, whereby the neutron shielding apparatus is configured to at least partially attenuate the neutron radiation 216 external to the vacuum chamber 210. The neutron shielding provided by the neutron shielding apparatus 240 generally wraps around the beam dump 220 (or, alternatively, wraps around a faraday cup), whereby the neutron shielding apparatus has a shield member 242 comprising neutron shielding material 244. The neutron shielding material 244, for example, contains an abundant amount of hydrogen atoms for attenuating the neutron radiation 216 to safe dose rates. The nuclei of the hydrogen atoms, for example, are approximately the same mass as the neutrons of the neutron radiation 216, whereby collision of the neutrons with the hydrogen atoms transfers maximum energy to the hydrogen atoms of the neutron shielding material 244, thus thermalizing the neutrons down to the sub-eV range, after many collisions, therewith. The neutron shielding material 244, for example, can comprise polyethylene, whereby the thermalized neutrons can be readily absorbed by additionally provided boron (e.g., 5 -50%10B) further provided in the polyethylene.

[0059] During the absorption process, however, photons are further released in the form of gamma radiation. The gamma radiation can be a secondary radiation source, whereby the shield member 242 can further comprise lead shielding 246 that is substantially thinner than the neutron shielding material 244. While the neutron shielding apparatus 240 substantially attenuates the neutron radiation 216 in a first region 248, thus limiting an exposure of the operator 218 to harmful radiation, barring additional shielding, the shield member 242 shown in Fig. 3 may not, itself, prevent exposure of the operator to the neutron radiation 216 in a second region 250. However, it is to be appreciated that various additional components (not shown) or additional space / distance may be provided between the operator 218 in the second region 250 and the beam dump 220 to effectively attenuate the neutron radiation 216 to safe levels (e.g., dose rates decrease with distance d according to the inverse square law 1 / d2).

[0060] In accordance with another aspect of the present disclosure, Fig. 4 illustrates a neutron shielding apparatus 260 for an ion implantation system, such as can be implemented in the ion implantation system 100 of Fig. 1. The neutron shielding apparatus 260 of Fig. 4, for example, comprises a shield member 262, whereby the shield member comprises a cavity 264 for accepting the ion beam 214 emanating from an origin location 266 as it travels along the beam path 110 in Fig. 1 . The shield member 262 of Fig. 4, for example, comprises a neutron attenuation material 268 such as polyethylene. The cavity 264, for example, has an entrance 270 configured to accept the ion beam 214.

[0061] In the present example, the neutron shielding apparatus 260 is operably coupled to the chamber wall 222 of the vacuum chamber 210, whereby the ion beam 214 passes through the entrance 270 of the cavity 264 in the shield member 262, and wherein the cavity 264 generally defines a blind hole 272. A target structure 274 e.g., a target member), for example, is selectively positioned within the cavity 264 at a first predetermined distance 276 (a depth D) from the entrance 270, whereby the target structure is configured to intercept the ion beam 214. The target structure 274, for example, can comprise a beam dump 220 or Faraday cup 232, as described above, whereby upon intercepting the ion beam 214, neutron radiation 216 is emitted in all directions from the target structure. Accordingly, the neutron attenuation material 268 is configured to attenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions 278A-278E defined beyond a predetermined periphery 280 (represented by dashed lines) of the target structure 274. The predetermined periphery

[0062] 280, for example, can be generally defined by the shield member 262.

[0063] Dimensions of the neutron attenuation material 268, for example, may be associated with the one or more regions 278A-278E and their relative location with respect to the target structure 274, as further illustrated in Fig. 5. For example, the entrance 270 of the cavity 264 defines a second predetermined distance 281 , also referred to as an entrance width W of the cavity. For optimal shielding from neutron radiation, the relationship of the second predetermined distance 281 (the entrance width W) to the first predetermined distance 276 (the depth D) can define an aspect ratio a (alpha) provided as:

[0064] W / D = 2 tan (a) (1 ).

[0065] The present disclosure thus appreciates that the entrance width W to depth D ratio of the neutron attenuation material 268 being less than approximately 2 can advantageously provide an adequate thickness of the neutron shielding of the operator 218 in the one or more regions 278A-278E. In other words, the first predetermined distance 276 is greater than approximately one-half the second predetermined distance

[0066] 281.

[0067] In an example where the neutron attenuation material 268 is polyethylene, a ten- inch thickness of the neutron attenuation material can attenuate the neutron radiation by approximately ten-fold. Providing an aspect ratio W / D <= 2 e.g., corresponding to approximately a 45° spread), for example, can minimize or eliminate exposure of the operator 218 to the neutron radiation 216, as the neutron radiation extending upstream along the beam path 110 provides enough distance e.g., using the radiation inverse square law) to ensure safety of the operator.

[0068] The blind hole 272, for example, extends the depth D from the entrance 270 into the shield member 262, for example, wherein the target structure 274 is selectively positioned within the blind hole at approximately the depth the first predetermined distance 276 from the entrance 270. A target width 282, for example, is approximately 2-3 times larger than a beam width 284 of the ion beam 214, whereby entrance edges 285 are not struck by the ion beam.

[0069] In one example, as illustrated in the example shown in Fig. 6, the target structure 274 may comprise a first target portion 286A and a second target portion 286B that are selectively positioned with respect to the ion beam 214. For example, the first target portion 286A may be configured to receive the ion beam 214 at a first energy (e.g., a low energy beam), and the second target portion 286B may be configured to receive the ion beam at a second energy (e.g., a high energy beam). The target structure 274, for example, may be selectively translated (indicated by arrow 288) such one of the first target portion 286A and the second target portion 286B selectively intercepts the ion beam 214 based on a process recipe associated with the formation of the ion beam.

[0070] The target structure 274 is illustrated in another example in Fig. 7, whereby the target structure is configured to selectively rotate (indicated by arrow 290). As such, one of the first target portion 280A or the second target portion 280B selectively intercepts the ion beam 214 based on the rotational position of the target structure 274. In other examples, the first target portion 280A may comprise a faraday apparatus, while the second target portion 280B may comprise a graphite beam dump or other structure. The respective faraday apparatus and graphite beam dump, for example, may be further cooled, shielded, or otherwise adapted to accept selectively intercept the ion beam 214.

[0071] In accordance with another example, as illustrated in Figs. 8A-8B, another neutron shielding apparatus 300 is illustrated, whereby the cavity 264 comprises a passageway 302 extending through the shield member 262, thereby defining the entrance 270 and an exit 304 of the passageway. In the present example, the neutron shielding apparatus may be positioned anywhere along the beam path 1 10 of Fig. 1 , whereby the ion beam 108 can be selectively passed through the neutron shielding apparatus, as will now be described. In some examples, the target structure 274 of Figs. 8A-8B is selectively positioned at the first predetermined distance 276 within the passageway 302. Further, in one example, the second predetermined distance 281 (the width W of the cavity 264) is approximately three times the beam width 284 of the ion beam 214. Further, a thickness 305 of the neutron attenuation material 268 is approximately twenty times the beam width 284, and the second predetermined distance 281 (the width W of the cavity 264) is approximately one to two times the first predetermined distance 276 (the depth D of the cavity). In another example, a positioning apparatus (not shown) is operably coupled to the target structure 274, wherein the positioning apparatus is configured to selectively position the target structure at a target position 306 within the passageway 302, such as when beam measurements are desired to be taken, or when the ion beam 214 is desired to be otherwise blocked. As such, the beam path 1 10 of the ion beam 214 intersects the target structure 274 when the target structure is at the target position 306 illustrated in Fig. 8A.

[0072] In another example, the shield member 262 comprises a recess 310, wherein the recess extends laterally outward from a sidewall 312 of the passageway 302 and away from the beam path 110. As such, the positioning apparatus comprises a translation apparatus configured to selectively translate (illustrated as arrow 314) the target structure 274 between the target position 306 illustrated in Fig. 8A and a retracted position 316 within the recess, as illustrated in Fig. 8B. The shield member 262, for example, can further comprise a gamma radiation shield 318, such as a lead sheet or other gamma-blocking material.

[0073] In accordance with yet another example of the present disclosure, Figs. 9A-9B illustrate a target 350 that defines a beam blocker 352. The beam blocker 352, for example, comprises a beam passage 354 defined therethrough, and can be selectively positioned along the beam path 110 of Figs. 8A-8B. The beam passage 354, for example, is configured to selectively pass the ion beam 214 therethrough in an open position 356 shown in Fig. 9A, and to selectively block the ion beam from passing therethrough in a closed position 358, as shown in Fig. 9B. For example, the beam blocker 352 is configured to rotate (illustrated as arrow 360) to selectively block or pass the ion beam 214 through the passageway 302 of Figs. 8A-8B.

[0074] Although the invention has been shown and described with respect to a certain embodiment or embodiments, it should be noted that the above-described embodiments serve only as examples for implementations of some embodiments of the present invention, and the application of the present invention is not restricted to these embodiments. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.), the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component ( / .e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments as may be desired and advantageous for any given or particular application. Accordingly, the present invention is not to be limited to the above-described embodiments, but is intended to be limited only by the appended claims and equivalents thereof.

Claims

CLAIMSIn the Claims:1 . A neutron shielding apparatus for an ion implantation system, the neutron shielding apparatus comprising: a shield member comprising a neutron attenuation material, wherein the shield member has a cavity defined therein, and wherein the cavity has an entrance configured to accept an ion beam along a beam path; and a target structure positioned a first predetermined distance from the entrance within the cavity and configured to intercept the ion beam, whereby the ion beam is configured to emit neutron radiation in all directions therefrom upon being intercepted by the target structure, and wherein the neutron attenuation material is configured to attenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure.

2. The neutron shielding apparatus of claim 1 , wherein the ion beam emanates generally linearly toward the target structure from an origin location along the beam path, and wherein the neutron attenuation material has a predetermined thickness associated with each of the one or more regions, respectively.

3. The neutron shielding apparatus of claim 2, wherein the cavity comprises a blind hole extending into the shield member a predetermined depth from the entrance, and wherein the target structure is selectively positioned within the blind hole at approximately the predetermined depth.

4. The neutron shielding apparatus of claim 2, wherein the neutron radiation is emitted along a return path to the origin location, and wherein the neutron attenuation material is not present along the return path.

5. The neutron shielding apparatus of claim 4, further comprising one or more upstream components positioned along the beam path at one or more upstream locations with respect to the origin location, wherein the one or more upstream components are configured to attenuate the neutron radiation to the predetermined radiation exposure limit at one or more upstream regions.

6. The neutron shielding apparatus of claim 2, wherein the cavity comprises a passageway extending through the shield member, thereby defining the entrance and an exit, wherein the target structure is selectively positioned at the first predetermined distance within the passageway.

7. The neutron shielding apparatus of claim 6, further comprising a positioning apparatus operably coupled to the target structure, wherein the positioning apparatus is configured to selectively position the target structure at a target position within the passageway, wherein the beam path intersects the target structure when the target structure is at the target position.

8. The neutron shielding apparatus of claim 7, wherein the target structure comprises a first side having a faraday cup and a second side having a graphite beam dump, and wherein the positioning apparatus is configured to selectively expose each of the first side and the second side of the target structure.

9. The neutron shielding apparatus of claim 8, wherein the first side is opposite the second side, and wherein the positioning apparatus comprises a rotation apparatus configured to selectively rotate the target structure within the passageway.

10. The neutron shielding apparatus of claim 7, wherein the shield member comprises a recess, wherein the recess extends laterally outward from a sidewall of the passageway and away from the beam path, and wherein the positioning apparatus comprises a translation apparatus configured to selectively translate the target structure between the target position and a retracted position within the recess.1 1 . The neutron shielding apparatus of claim 7, wherein the target structure comprises a beam passage defined therethrough, wherein the target structure is configured to selectively block the ion beam from passing through the beam passage based on a rotational orientation of the target structure with respect to the ion beam.

12. The neutron shielding apparatus of claim 6, wherein the cavity defines an entrance width at the entrance of the cavity, wherein the first predetermined distance is greater than approximately one-half the entrance width.

13. The neutron shielding apparatus of claim 1 , wherein the neutron attenuation material comprises polyethylene.

14. The neutron shielding apparatus of claim 1 , wherein the shield member comprising further comprises a gamma radiation shield.

15. The neutron shielding apparatus of claim 14, wherein the gamma radiation shield comprises a lead sheet.

16. A neutron shielding apparatus for an ion implantation system, the neutron shielding apparatus comprising: a shield member consisting of a neutron attenuation material, wherein the shield member has a cavity defined therein, and wherein the cavity has an entrance configured to accept an ion beam along a beam path, wherein the entrance has an entrance width when viewed along the beam path; and a target structure positioned within the cavity at a predetermined distance from the entrance along the beam path, wherein the target structure is configured to intercept the ion beam, whereby the ion beam is configured to emit neutron radiation in all directions therefrom upon being intercepted by the target structure, wherein the ion beam emanates generally linearly along the beam path toward the target structure from an origin location, and wherein the neutron attenuation material is configured toattenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure, wherein the neutron attenuation material has a predetermined thickness associated with each of the one or more regions, respectively.

17. The neutron shielding apparatus of claim 16, wherein the cavity comprises blind hole extending into the shield member from the entrance, and wherein the target structure is selectively positioned within the blind hole at approximately the predetermined distance, wherein the predetermined distance is greater than approximately one-half the entrance width.

18. The neutron shielding apparatus of claim 16, wherein the cavity comprises a passageway extending through the shield member, thereby defining the entrance and an exit of the cavity, wherein the target structure is selectively positioned at the predetermined distance within the passageway, wherein the predetermined distance is greater than approximately one-half the entrance width.

19. The neutron shielding apparatus of claim 18, further comprising a positioning apparatus operably coupled to the target structure, wherein the positioning apparatus is configured to selectively position the target structure at a target position within the passageway, wherein the beam path intersects the target structure when the target structure is at the target position.

20. The neutron shielding apparatus of claim 19, wherein the target structure comprises a first side having a faraday cup and a second side having a graphite beam dump, and wherein the positioning apparatus is configured to selectively expose each of the first side and the second side of the target structure.21 . The neutron shielding apparatus of claim 20, wherein the first side is opposite the second side, and wherein the positioning apparatus comprises a rotation apparatus configured to selectively rotate the target structure within the passageway.

22. A neutron shielding apparatus for an ion implantation system, the neutron shielding apparatus comprising: a shield member consisting of a neutron attenuation material, wherein the shield member has a cavity defined therein, and wherein the cavity has an entrance configured to accept an ion beam along a beam path, wherein the entrance has an entrance width when viewed along the beam path; and a target structure positioned within the cavity at a predetermined distance from the entrance along the beam path, wherein the predetermined distance is greater than approximately one-half the entrance width, and wherein the target structure is configured to intercept the ion beam, whereby the ion beam is configured to emit neutron radiation in all directions therefrom upon being intercepted by the target structure, wherein the ion beam emanates generally linearly along the beam path toward the target structure from an origin location, and wherein the neutron attenuation material is configured to attenuate the neutron radiation to a predetermined radiation exposure limit at one or more regions beyond a predetermined periphery of the target structure, wherein the neutron attenuation material has a predetermined thickness associated with each of the one or more regions, respectively.

23. The neutron shielding apparatus of claim 22, wherein the cavity comprises blind hole extending into the shield member from the entrance.

24. The neutron shielding apparatus of claim 22, wherein the cavity comprises a passageway extending through the shield member.

25. The neutron shielding apparatus of claim 24, further comprising a positioning apparatus operably coupled to the target structure, wherein the positioning apparatus is configured to selectively position the target structure at a target position within the passageway, wherein the beam path intersects the target structure when the target structure is at the target position.

26. The neutron shielding apparatus of claim 25, wherein the target structure comprises a first side having a faraday cup and a second side having a graphite beam dump, and wherein the positioning apparatus is configured to selectively expose each of the first side and the second side of the target structure.

27. The neutron shielding apparatus of claim 26, wherein the first side is opposite the second side, and wherein the positioning apparatus comprises a rotation apparatus configured to selectively rotate the target structure within the passageway.

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