Methods for monitoring neutron rays and ion implantation devices

Abstract

[Problem] To monitor neutron radiation generation appropriately and at low cost. [Solution] The method disclosed herein includes the following steps: recording time-series data that establishes a correspondence between beam conditions (including ion type, energy, and beam current of the ion beam delivered along a beamline within an ion implantation device) and the neutron dose rate measured at a predetermined measurement location within the ion implantation device; delivering a high-energy ion beam along the beamline; acquiring a measured value of the neutron dose rate at the predetermined measurement location while delivering the high-energy ion beam; using the time-series data and the beam conditions of the high-energy ion beam, calculating an inferred value of the neutron dose rate at the predetermined measurement location while delivering the high-energy ion beam; and comparing the measured value with the inferred value.

Description

Methods for monitoring neutron rays and ion implantation devices This disclosure relates to a method for monitoring neutron rays and an ion implantation device. In semiconductor manufacturing, a standard procedure involves implanting ions into the semiconductor wafer to alter its conductivity, crystal structure, or other properties. The apparatus used in this step is typically called an ion implantation apparatus. The implantation energy is determined based on the desired implantation depth of the ions near the wafer surface. Low-energy ion beams are used for shallow implantation, while high-energy ion beams are used for deeper implantation. In recent years, to enable deeper implantation, the requirements for so-called ultra-high-energy ion implantation, which uses even higher-energy ion beams, have increased compared to conventional high-energy ion implantation. Ions accelerated to ultra-high energies can collide with components present in the beam of the ion implantation device, causing a nuclear reaction. This nuclear reaction can generate radiation such as neutron rays. [Prior Art Documents] [Patent Documents] [Patent Document 1] Japanese Patent No. 6785188 [The problem the invention aims to solve] In ultra-high energy ion implantation devices that raise concerns about neutron radiation, it is assumed, depending on the conditions, that the amount of neutron radiation produced is not so large, reaching a value close to the detection limit of a typical neutron radiation detector. Furthermore, the neutron dose rate generated by the neutron radiation source may change due to years of use. Therefore, it is not easy to confirm the integrity of the neutron radiation detector's measurements based solely on the measured neutron dose rate. One of the exemplary objectives of this disclosed form is to provide a technique for appropriately monitoring the generation of neutron rays at low cost. [Technical Means for Solving the Problem] The method disclosed herein includes the following steps: recording time-series data that establishes a correspondence between beam conditions (including ion type, energy, and beam current of the ion beam delivered along a beamline within the ion implantation device) and a neutron dose rate measured at a predetermined measurement location within the ion implantation device in a recording device; delivering a high-energy ion beam along the beamline; acquiring a measured value of the neutron dose rate measured at the predetermined measurement location while delivering the high-energy ion beam; using the time-series data and the beam conditions of the high-energy ion beam, calculating an inferred value of the neutron dose rate inferred at the predetermined measurement location while delivering the high-energy ion beam; and comparing the measured value with the inferred value. Another aspect disclosed herein is an ion implantation device. This ion implantation device comprises: an ion source for generating an ion beam; a beamline device configured to deliver the ion beam along the beamline, including an accelerator that accelerates the ion beam and generates a high-energy ion beam; a neutron beam detector positioned at a predetermined measurement location to measure the neutron dose rate; a memory storing a program; and a processor. The processor executes the following steps according to the program: recording timing data that establishes a correspondence between beam conditions (including the ion type, energy, and beam current of the ion beam delivered along the beamline) and the neutron dose rate measured using the neutron beam detector in a recording device; delivering the high-energy ion beam along the beamline; acquiring a measured value of the neutron dose rate measured using the neutron beam detector while delivering the high-energy ion beam; calculating an inferred value of the neutron dose rate at the predetermined measurement location while delivering the high-energy ion beam using the timing data and the beam conditions of the high-energy ion beam; and comparing the measured value with the inferred value. Furthermore, any combination of the aforementioned constituent elements, or any result obtained by substituting the constituent elements or expressions of this disclosure among methods, apparatuses, systems, etc., shall also be considered valid forms of this disclosure. [Effects of the Invention] According to a non-limiting exemplary embodiment of the present invention, a technique for appropriately monitoring the generation of neutron rays at low cost can be provided. The following description, with reference to the accompanying drawings, details the configurations of the method, ion implantation method, and ion implantation device used to implement the present disclosure. Furthermore, in the description of the drawings, the same elements are labeled with the same symbol, and repetitive descriptions are omitted where appropriate. Also, the structures described below are illustrative and do not limit the scope of the invention in any way. This embodiment relates to a high-energy ion implantation device. The ion implantation device accelerates an ion beam generated by an ion source and delivers the high-energy ion beam obtained by acceleration along a beamline to the object to be processed (e.g., a substrate or wafer W), implanting ions into the object to be processed. In this embodiment, "high energy" refers to energies of 4 MeV or higher, 5 MeV or higher, or 10 MeV or higher. Based on high-energy ion implantation, compared to conventional ion implantation with energies below 4 MeV, desired impurity ions are implanted onto the wafer surface at higher energies. Therefore, it is possible to implant desired impurities into deeper regions of the wafer surface (e.g., depths of 5 μm or higher). Applications of high-energy ion implantation include, for example, forming P-type and / or N-type regions in the manufacture of state-of-the-art semiconductor devices such as image sensors. In high-energy ion implantation devices, neutron rays can be generated by colliding a high-energy ion beam with a beam-forming component. According to the present inventors, neutron rays are generated using boron ion beams with energies of 4 MeV or higher. Specifically, regarding boron, a non-radioactive nucleus... 11 B is capable of undergoing the nuclear reactions described in (1) and (2) below. 11 B+ 11 B→ 21 Ne+n……(1) 11 B+ 12 C→ 22 Ne+n……(2) The above (1) is boron 11 When boron collides with each other, a nuclear reaction occurs, producing neutrons (n) (also known as the BB reaction). First, if boron... 11 When the ion beam of B strikes (collides with) a component that forms the beam, boron accumulates inside that component. 11 B. Subsequently, if high-energy boron 11 The ion beam of B and the boron accumulated inside the constituent components 11 When B collides, the BB reaction described in (1) above occurs, producing neutron rays. The above (2) is boron 11 B and carbon 12 The nuclear reaction that produces neutrons (n) through collisions with carbon (C) is also known as the BC reaction. At least a portion of the building blocks of the beam are composed of graphite (i.e., carbon), thus enabling the high-energy boron... 11 When the ion beam of boron collides with graphite, the BC reaction described in (2) above occurs, producing neutron rays. Additionally, boron is accumulated inside the graphite. 11 B can also produce neutron rays caused by the BB reaction described above (1). As described above, in high-energy ion implantation devices, although the implanted ions do not contain radioactive nuclei, neutron rays can be generated by the collision of the high-energy ion beam with various parts of the beam. Therefore, high-energy ion implantation devices possess neutron ray generation sources capable of producing neutron rays through the collision of high-energy ion beams. Therefore, in high-energy ion implantation devices, the neutron rays generated by the neutron ray generation source must be properly managed. Typically, in the case of devices that generate radiation such as neutron rays, a dedicated radiation management area is considered, within which an ion implantation device is installed. However, it is not easy to set up a separate radiation management area in a semiconductor manufacturing plant for mass production. In a semiconductor manufacturing plant, wafer containers and the like must be moved between the ion implantation device and other devices at any time. When the ion implantation device is installed in the radiation management area, wafer containers and the like are moved in and out between the management area and the management area. In order to properly shield neutron rays, concrete walls with a thickness of tens of centimeters or more are required, and the shielding doors used to move wafer containers in and out are also very thick. Thus, it is quite labor-intensive to open and close the thick shielding doors every time wafer containers are moved in and out. Furthermore, if the operation of the ion implantation device must be stopped when opening and closing the shielding doors, the production efficiency of semiconductor devices is reduced. Therefore, the inventors considered installing a neutron scattering component in the shell surrounding the device body that constitutes the beam, so that the neutron dose rate outside the shell is lower than the benchmark value limited by law, etc. In addition to neutron rays, X-rays can also be cited as radiation generated in high-energy ion implantation devices. Lead plates or similar materials are installed in the casing as X-ray shielding components. X-rays are easier to shield than neutron rays; for example, using lead plates with a thickness of approximately 1 mm to 5 mm can adequately shield X-rays directed towards the outside of the casing. On the other hand, reducing the neutron dose rate is not easy. For example, using ordinary high-density polyethylene (specific gravity 0.95 g / cm³) can be challenging. 3 When used as a neutron beam scattering component, a thickness of about 150mm to 200mm is required to reduce the neutron dose rate to 1 / 10. To reduce the neutron dose rate, it might be desirable to surround the entire device with a thick neutron beam scattering component. However, in high-energy ion implantation devices, the accelerating device used to accelerate the ion beam to high energies becomes larger, resulting in a device body area of, for example, 10m × 20m or more, and a height exceeding 2m. Therefore, if a thick neutron beam scattering component is installed throughout the entire device, a large number of neutron beam scattering components would be required, leading to a significant increase in cost and product weight, making this undesirable. In this embodiment, the goal is not to completely block neutron radiation, but rather to strategically place neutron radiation scattering components at locations outside the casing where the neutron dose rate might exceed a predetermined reference value as defined by law. Specifically, the placement of the neutron radiation scattering components is varied according to the distance from the neutron radiation source to the casing. This is because the neutron dose rate is inversely proportional to the square of the distance from the neutron radiation source; the neutron dose rate is higher at locations closer to the casing than at locations farther from the casing. Furthermore, the neutron dose rate generated by the neutron beam source in this embodiment is not very high; for example, the neutron dose rate at a distance of about 1 m from the neutron beam source is about 0.1 to 2 μSv / h. Therefore, by focusing on neutron beam scattering components at locations with relatively high neutron dose rates, the neutron dose rate outside the casing can be suppressed to below the benchmark value defined by law, etc. In this embodiment, the "neutron ray scattering component" refers to a material with a high scattering effect on neutron rays. Hydrogen (H) and boron (B) are known elements with high neutron ray scattering effects, and materials with high hydrogen and boron content are preferred as neutron ray scattering components. For example, polyolefins such as polyethylene and paraffin wax, with hydrogen atom content of 0.08~0.15 g / cm³, are examples of materials with high hydrogen content. 3 The material is preferred. For example, materials with a specific gravity of 0.94~0.97 g / cm³ are preferred. 3 Approximately 10-40% by weight of high-density polyethylene. Furthermore, as a neutron ray scattering component, boron oxide (B2O3) can be used in high-density polyethylene containing approximately 10-40% by weight. 2O 3) Those containing boron compounds. Figure 1 schematically illustrates the neutron beam scattering components 76a and 76b disposed in the housing 70. The housing 70 is configured to surround the periphery of the device 78 constituting the beam, separating the outer space E from the inner space F. The neutron beam generating source 79 is located inside the device 78. The housing 70 has an outer surface 70a exposed to the outer space E and an inner surface 70b exposed to the inner space F. The neutron beam scattering components 76a and 76b are disposed inside the housing 70, that is, between the outer surface 70a and the inner surface 70b of the housing 70. The housing 70 has a receiving portion 71 (also simply referred to as the receiving portion) provided with neutron ray scattering members 76a and 76b, and a non-receiving portion 72 without neutron ray scattering members. The receiving portion 71 includes: a first receiving portion 71a, which is provided with a first neutron ray scattering member 76a with a relatively large thickness ta; and a second receiving portion 71b, which is provided with a second neutron ray scattering member 76b with a relatively small thickness tb. The first neutron ray scattering member 76a is disposed in a first direction (arrow Da) where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 is a first distance, and is disposed at a position where neutron rays emitted from the neutron ray source 79 along the first direction can enter. The second neutron ray scattering member 76b is disposed in a second direction (arrow Db) where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 is a second distance greater than the first distance, and is disposed at a position where neutron rays emitted from the neutron ray source 79 along the second direction can enter. The thickness ta of the first neutron ray scattering member 76a is, for example, 100 mm or more, and is approximately 200 mm to 500 mm. On the other hand, the thickness tb of the second neutron ray scattering member 76b is, for example, 50 mm or more, and is approximately 100 mm to 200 mm. The first distance (Da) is for example, less than 2m, less than 1.5m or less than 1m, and the second distance (Db) is for example, less than 10m or less than 5m, which is more than 2m, more than 1.5m or more than 1m. Neutron scattering members are not disposed in a third direction (arrow Dc) where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 is greater than the first distance and the second distance. The third distance (Dc) is, for example, 5 m or more, 10 m or more, or 15 m or more. Therefore, in this embodiment, neutron scattering members are disposed in directions where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 is less than or equal to a certain predetermined value (e.g., the second distance), and neutron scattering members are not disposed in directions where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 exceeds another predetermined value (e.g., the third distance). Alternatively, it can be said that the first neutron ray scattering member 76a is positioned where the angular difference θa between the thickness direction of the scattering member and the first direction (arrow Da) from the neutron ray source 79 toward the outer surface 70a of the housing 70 is small. On the other hand, it can also be said that the second neutron ray scattering member 76b is positioned where the angular difference θb between the thickness direction of the scattering member and the second direction (arrow Db) from the neutron ray source 79 toward the outer surface 70a of the housing 70 is large. Neutron rays from the neutron ray source 79 toward the first neutron ray scattering member 76a can enter at approximately a right angle relative to the first neutron ray scattering member 76a, therefore the effective thickness (ta / cos(θa)) through which the neutron rays pass is approximately equal to the actual thickness ta of the scattering member. On the other hand, neutron rays from the neutron ray generation source 79 can enter the second neutron ray scattering member 76b at an angle relative to the second neutron ray scattering member 76b, so the effective thickness (tb / cos(θb)) through which the neutron rays pass becomes larger than the actual thickness tb of the scattering member. Therefore, even if a second neutron ray scattering member 76b with a relatively small thickness tb is used, the neutron dose rate in the external space E of the housing 70 can be effectively reduced. In the example of Figure 1, the first receiving portion 71a and the second receiving portion 71b are arranged adjacent to each other, and the first receiving portion 71a and the second receiving portion 71b are arranged to overlap at least partially in the thickness direction or in the direction from the neutron beam generating source 79 toward the outer surface 70a. Furthermore, the first neutron beam scattering member 76a provided in the first receiving portion 71a and the second neutron beam scattering member 76b provided in the second receiving portion 71b are arranged to overlap at least partially in the thickness direction or in the direction from the neutron beam generating source 79 toward the outer surface 70a. This prevents high dose rate neutron beams from leaking into the external space E through the gap between the first receiving portion 71a and the second receiving portion 71b. In the example of Figure 1, the thickness of the neutron scattering components 76a and 76b is changed in two stages. However, the thickness of the neutron scattering components can also be changed in three or more stages, or the thickness of the neutron scattering components can be changed continuously. Furthermore, in the first receiving part 71a and the second receiving part 71b, plate-shaped or block-shaped neutron scattering components with desired thicknesses ta and tb can be used. Alternatively, multiple plate-shaped or block-shaped neutron scattering components that are thinner than the desired thicknesses ta and tb can be overlapped in the thickness direction. Figure 2 is a detailed diagram showing the structure of the housing 71. The housing 71 has a body frame 73 and a cover plate 74. An X-ray shielding member 75 and a neutron scattering member 76 are disposed inside the housing 71. The body frame 73 is a support structure for supporting the X-ray shielding member 75 and the neutron scattering member 76, forming the outer surface 70a and side surface 70c of the housing 71. The cover plate 74 is installed in the opening of the body frame 73, forming the inner surface 70b of the housing 71. The body frame 73 and the cover plate 74 are made of metal materials such as iron and aluminum. The X-ray shielding member 75 and the neutron scattering member 76 are arranged overlapping in the thickness direction, for example, with the X-ray shielding member 75 forming the outer surface 70a side and the neutron scattering member 76 forming the inner surface 70b side. The X-ray shielding member 75 is, for example, a lead plate, and the neutron scattering member 76 is, for example, a plate-shaped or block-shaped high-density polyethylene. Alternatively, a non-combustible sheet can be installed on the inner surface 70b side of the neutron ray scattering member 76 instead of the cover plate 74. Furthermore, a non-combustible sheet can be added between the cover plate 74 and the neutron ray scattering member 76. A non-combustible sheet refers to a sheet-like component that does not burn for a certain period of time (e.g., 20 minutes) when heated; examples include polyvinyl chloride (PVC) resin sheets, resin sheets with glass fiber as a substrate, or metal sheets. The non-receiving portion 72 can be constructed in the same manner as the receiving portion 71, except that it does not have a neutron scattering member 76 inside. The non-receiving portion 72 may have, for example, the body frame 73 and cover plate 74 shown in FIG. 2, and an X-ray shielding member 75 is provided inside the non-receiving portion 72. The thickness of the non-receiving portion 72 may be the same as or less than the thickness of the receiving portion 71. The interior of the non-receiving portion 72 may be a cavity. Figure 3 schematically shows neutron scattering components 77a and 77b, which are separately arranged from the housing 70. The neutron scattering components 77a and 77b are installed in the device 78 containing the neutron scattering source 79 or in the support structure of the device 78. Since no neutron scattering components are provided in the housing 70, the housing 70 is configured as the aforementioned non-receiving part 72. Non-combustible sheets can be installed on the surfaces of the neutron scattering components 77a and 77b. In Figure 3, neutron scattering members 77a and 77b are also arranged according to the distance from the neutron ray source 79 to the outer surface 70a of the housing 70. The first neutron ray scattering member 77a, with a larger thickness ta, is arranged in a first direction (arrow Da) where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 is a first distance, and is positioned where neutron rays emitted from the neutron ray source 79 along the first direction can enter. The second neutron ray scattering member 77b, with a smaller thickness tb, is arranged in a second direction (arrow Db) where the distance from the neutron ray source 79 to the outer surface 70a of the housing 70 is a second distance greater than the first distance, and is positioned where neutron rays emitted from the neutron ray source 79 along the second direction can enter. On the other hand, no neutron scattering components are disposed in the third direction (arrow Dc) where the distance from the neutron ray generating source 79 to the outer surface 70a of the housing 70 is greater than the first and second distances. By disposing the neutron ray scattering components 77a and 77b in this way, the same neutron dose rate reduction effect as the structure in FIG1 can be expected. In Figure 3, neutron scattering components 77a and 77b are positioned closer to the neutron beam source 79, thus reducing the required number of neutron scattering components compared to those 76a and 76b in Figure 1. Therefore, the arrangement of neutron scattering components in Figure 3 may be superior to that in Figure 1. However, various machines, cables, etc., surround the device 78 that forms the beamline, making it difficult to arrange neutron scattering components seamlessly near the device 78. Therefore, in this embodiment, while using neutron scattering components 76a and 76b mounted on the housing as in Figure 1, neutron scattering components 77a and 77b are also appropriately arranged near the device body as in Figure 3. This reduces the total number of neutron scattering components in the overall device while keeping the neutron dose rate in the external space E of the housing below a baseline value. Figure 4 is a schematic top view of the ion implantation device 100 according to the embodiment. Figures 5(a) to 5(c) are side views showing the schematic structure of the ion implantation device of Figure 4. Figure 5(a) corresponds to the cross-section along line AA in Figure 4, Figure 5(b) corresponds to the cross-section along line BB in Figure 4, and Figure 5(c) corresponds to the cross-section along line CC in Figure 4. The ion implantation device 100 includes a device body 58 and a housing 60. The device body 58 includes a beam generation unit 12, a beam acceleration unit 14, a beam deflection unit 16, a beam delivery unit 18, and a substrate handling unit 20. The housing 60 is disposed around the device body 58 and at least partially surrounds the device body 58. Details will be described later, but neutron scattering components are disposed at the locations indicated by shaded lines in the figures. The beam generation unit 12 includes an ion source 10, a plurality of gas supply sources 10a and 10b, and a mass spectrometry analysis device 11. The ion source 10 generates an ion beam using source gases supplied from the plurality of gas supply sources 10a and 10b respectively. A first gas supply source 10a supplies a source gas of a first ion type, and a second gas supply source 10b supplies a source gas of a second ion type different from the first ion type. The ion source 10 generates an ion beam including either the first ion type or the second ion type using source gases supplied from either the first gas supply source 10a or the second gas supply source 10b. The beam generation unit 12 may have three or more gas supply sources for supplying three or more types of source gases. In the beam generation unit 12, an ion beam is drawn from the ion source 10 and analyzed by a mass spectrometry analyzer 11. The mass spectrometry analyzer 11 has a mass spectrometry magnet 11a and a mass spectrometry slit 11b. The mass spectrometry slit 11b is located downstream of the mass spectrometry magnet 11a. Based on the results of the mass spectrometry analysis performed by the mass spectrometry analyzer 11, only the desired ion species are selected for implantation, and the ion beam of the selected ion species is guided to the next beam acceleration unit 14. The beam acceleration unit 14 includes a plurality of linear accelerating devices 22a, 22b, and 22c for accelerating the ion beam and a beam profile slit 23, forming a linearly extending portion of the beamline BL. Each of the linear accelerating devices 22a-22c has one or more high-frequency resonators, which apply a high-frequency (RF) electric field to the ion beam to accelerate it. The beam profile slit 23 is located at the downstream end of the beam acceleration unit 14 and is used to measure the beam profile of the high-energy ion beam accelerated by the plurality of linear accelerating devices 22a-22c. In this embodiment, three linear acceleration devices 22a to 22c are provided. The first linear acceleration device 22a is located on the upper layer of the beam acceleration unit 14 and includes multiple layers (e.g., 5 to 10 layers) of high-frequency resonators. The first linear acceleration device 22a performs "bunching," matching the continuous beam (DC beam) output from the beam generation unit 12 with a predetermined acceleration phase; for example, it accelerates the ion beam to an energy of approximately 1 MeV. The second linear acceleration device 22b is located on the middle layer of the beam acceleration unit 14 and includes multiple layers (e.g., 5 to 10 layers) of high-frequency resonators. The second linear acceleration device 22b accelerates the ion beam output from the first linear acceleration device 22a to an energy of approximately 2 to 3 MeV. The third linear acceleration device 22c is located on the lower layer of the beam acceleration unit 14 and includes multiple layers (e.g., 5 to 10 layers) of high-frequency resonators. The third linear accelerator 22c accelerates the ion beam output from the second linear accelerator 22b to a high energy of 4 MeV or higher. In this embodiment, the approximately 15 to 30 layers of high-frequency resonators included in the beam acceleration unit 14 are configured as three linear acceleration devices 22a to 22c. However, the structure of the beam acceleration unit 14 is not limited to that shown in the figure. The beam acceleration unit 14 can be configured as a single linear acceleration device, or it can be configured as two or more linear acceleration devices. Furthermore, the beam acceleration unit 14 can be composed of other arbitrary forms of acceleration devices, such as having tandem acceleration devices. This embodiment is not limited to a fixed ion acceleration method; any beam acceleration device can be used as long as it can generate an ultra-high energy ion beam of 4 MeV or higher. The high-energy ion beam output from the beam acceleration unit 14 has a certain range of energy distribution. Therefore, in order to make the high-energy ion beam reciprocate and parallelize and irradiate the wafer downstream of the beam acceleration unit 14, it is necessary to perform high-precision energy analysis, trajectory correction and beam convergence and divergence adjustment in advance. The beam deflection unit 16 performs energy analysis, energy dispersion control, and trajectory correction of the high-energy ion beam output from the beam acceleration unit 14. The beam deflection unit 16 constitutes the arc-shaped extension of the beamline BL. The high-energy ion beam is redirected by the beam deflection unit 16 and directed toward the beam delivery unit 18. The beam deflection unit 16 includes an energy analysis electromagnet 24, a laterally converging quadrupole lens 26 to suppress energy dispersion, an energy analysis slit 27, a first Faraday cup 28, a deflection electromagnet 30 for providing steering (track correction), and a second Faraday cup 31. The energy analysis electromagnet 24 is also referred to as an energy filtering electromagnet (EFM). Furthermore, the group of devices consisting of the energy analysis electromagnet 24, the laterally converging quadrupole lens 26, the energy analysis slit 27, and the first Faraday cup 28 is collectively referred to as the "energy analysis device". The energy analysis slit 27 is configured with a variable slit width to adjust the resolution of the energy analysis. The energy analysis slit 27 may be composed of, for example, two shielding bodies capable of moving in the slit width direction, and configured such that the slit width can be adjusted by changing the interval between the two shielding bodies. The energy analysis slit 27 can also be configured to have a variable slit width by selecting any one of a plurality of slits with different widths. The first Faraday cup 28 is positioned immediately behind the energy analysis slit 27 and is used for measuring the beam current for energy analysis. The second Faraday cup 31 is positioned immediately behind the deflection electromagnet 30 and is provided for measuring the beam current of the ion beam entering the beam delivery unit 18 after track correction. The first Faraday cup 28 and the second Faraday cup 31 are configured to move in and out of the beam line BL by means of the operation of the Faraday cup drive unit (not shown). The beam delivery unit 18 constitutes a straight-line extension of the beam line BL, parallel to the beam acceleration unit 14 across the maintenance area MA in the center of the device. The length of the beam delivery unit 18 is designed to be the same as the length of the beam acceleration unit 14. As a result, the beam line BL, composed of the beam acceleration unit 14, the beam deflection unit 16, and the beam delivery unit 18, forms a U-shaped layout. The beam delivery unit 18 includes a beam shaper 32, a beam scanner 34, a beam gather stack 35, a beam parallelizer 36, a final energy filter 38, and left and right Faraday cups 39L and 39R. The beam shaper 32 includes a quadrupole convergence / divergence device (Q-lens) and other convergence / divergence lenses, and is configured to shape the ion beam passing through the beam deflection unit 16 into a desired cross-sectional shape. The beam shaper 32 may be constructed, for example, by an electric field-type three-segment quadrupole lens (also called a tripolar Q-lens), and has three quadrupole lenses. The beam shaper 32 can independently adjust the convergence or divergence of the ion beam in the horizontal direction (x-direction) and the vertical direction (y-direction) by using the three lens devices. The beam shaper 32 may include a magnetic field lens device, or it may include a lens device that uses both electric and magnetic fields to shape the beam. The beam scanner 34 is configured to provide reciprocating scanning of the beam and is a beam deflection device for scanning the shaped ion beam in the x-direction. The beam scanner 34 has a pair of scanning electrodes facing each other in the beam scanning direction (x-direction). The scanning electrode pair is connected to a variable voltage power supply (not shown), and by periodically changing the voltage applied between the scanning electrode pair, the electric field generated between the electrodes is changed, causing the ion beam to deflect at various angles. As a result, the ion beam is scanned within the scanning range indicated by arrow X. In Figure 4, multiple trajectories of the ion beam within the scanning range are represented by thin solid lines. The beam scanner 34 deflects the beam beyond the scanning range indicated by arrow X, causing the ion beam to enter the beam collection stack 35 located away from the beam line BL. The beam scanner 34 blocks the ion beam by temporarily retracting it from the beam line BL towards the beam collection stack 35, thereby preventing the ion beam from reaching the downstream substrate handling unit 20. The beam parallelizer 36 is configured to make the travel direction of the scanned ion beam parallel to the designed trajectory of the beam line BL. The beam parallelizer 36 has a plurality of arc-shaped parallelizing lens electrodes with the ion beam passing through a slit at its center. The parallelizing lens electrodes are connected to a high-voltage power supply (not shown), so that the electric field generated by the applied voltage acts on the ion beam, aligning the travel direction of the ion beam parallel. Alternatively, the beam parallelizer 36 can be replaced with other beam parallelizing devices, such as a magnetic device utilizing a magnetic field. The final energy filter 38 is configured to analyze the energy of the ion beam and deflect ions with the required energy downwards (in the -y direction) to guide them to the substrate transport processing unit 20. The final energy filter 38 is sometimes referred to as an angular energy filter (AEF) and has an AEF electrode pair for electric field deflection. The AEF electrode pair is connected to a high-voltage power supply (not shown). In Figure 5(c), the ion beam is deflected downwards by applying a positive voltage to the upper AEF electrode and a negative voltage to the lower AEF electrode. Alternatively, the final energy filter 38 can be constructed using a magnetic field deflection magnet device, or it can be constructed using a combination of the electric field deflection AEF electrode pair and a magnet device. The left and right Faraday cups 39L and 39R are positioned downstream of the final energy filter 38 and at the left and right ends of the scanning range indicated by arrow X, where the beam can penetrate. The left and right Faraday cups 39L and 39R are positioned so as not to obstruct the beam directed toward the wafer W, and the beam current is measured when ions are implanted into the wafer W. A substrate handling unit 20 is disposed downstream of the beam delivery unit 18, that is, at the very downstream of the beam line BL. The substrate handling unit 20 includes an implantation processing chamber 40, a beam monitor 42, a substrate handling device 44, and a loading port 46. A platform drive device (not shown) is disposed in the implantation processing chamber 40. The platform drive device holds the wafer W during ion implantation and moves the wafer W in a direction perpendicular to the beam scanning direction (x direction) (y direction). A beam monitor 42 is located at the downstream end of the beamline BL inside the implantation processing chamber 40. The beam monitor 42 is positioned where the ion beam can enter even when there is no wafer W on the beamline BL, and is configured to measure the beam current before or between ion implantation steps. For example, the beam monitor 42 is located near the transport port 43 connecting the implantation processing chamber 40 and the substrate transport device 44, and is positioned vertically below the transport port 43. The substrate handling device 44 is configured to transport wafers W between a loading port 46, on which wafer containers 45 are placed, and an implantation processing chamber 40. The loading port 46 is configured to simultaneously hold a plurality of wafer containers 45, for example, having four loading stages arranged along the x-direction. A wafer container handling port 47 is provided vertically above the loading port 46, and the wafer containers 45 are configured to pass through vertically as indicated by arrow Y. For example, the wafer containers 45 are automatically moved into the loading port 46 through the wafer container handling port 47 by a handling robot installed in the ceiling or other part of a semiconductor manufacturing plant where the ion implantation device 100 is installed, and are automatically removed from the loading port 46. The ion implantation device 100 further includes a central control device 50. The central control device 50 controls all operations of the ion implantation device 100. The central control device 50 is implemented in hardware by components and mechanical devices, primarily a computer CPU and memory, and in software by computer programs. The various functions provided by the central control device 50 can be realized through hardware and software protocols. An operation panel 49, which includes a display device and an input device for setting the operating mode of the ion implantation device 100, is provided near the central control unit 50. The positions of the central control unit 50 and the operation panel 49 are not particularly limited, but for example, they can be positioned adjacent to the entrance / exit 48 of the maintenance area MA between the beam generation unit 12 and the substrate handling unit 20. By placing the ion source 10, the loading port 46, the central control unit 50, and the operation panel 49—which are frequently used by personnel managing the ion implantation device 100—adjacent to each other, operational efficiency can be improved. The ion implantation device 100 includes a neutron beam source capable of generating neutron beams through the collision of a high-energy ion beam of 4 MeV or higher. The components capable of serving as neutron beam sources are those into which a high-energy ion beam can be continuously injected, including slits, beam monitors, and beam gathers. Specifically, examples of slits capable of serving as neutron beam sources include beam profile slit 23 and energy analysis slit 27. Examples of beam monitors capable of serving as neutron beam sources include a first Faraday cup 28, a second Faraday cup 31, left and right Faraday cups 39L and 39R, and a beam monitor 42. Furthermore, the beam gather 35 located downstream of the beam scanner 34 can also serve as a neutron beam source. In Figures 4 and 5(a) to 5(c), the constituent elements of the beam that can serve as a neutron beam source are filled in black. The ion implantation device 100 includes a plurality of neutron beam detectors 51, 52, 53, and 54 for measuring neutron beams generated within the device. The dose rate of neutron beams generated in the ion implantation device 100 is not very high, approaching the detection limit of a typical neutron beam detector; therefore, they are positioned near the neutron beam source to improve measurement accuracy. The first neutron beam detector 51 is positioned near the beam profile slit 23, the second neutron beam detector 52 is positioned near the energy analysis slit 27 and the first Faraday cup 28, the third neutron beam detector 53 is positioned near the final energy filter 38 located between the beam gather 35 and the left and right Faraday cups 39L and 39R, and the fourth neutron beam detector 54 is positioned near the beam monitor 42. Furthermore, the configuration of the neutron beam detectors is merely an example; neutron beam detectors can be configured in fewer or more locations than those shown in the figure. For example, additional or alternative neutron beam detectors can be configured near the second Faraday cup 31 and the beam gather 35. Also, multiple neutron beam detectors can be configured in the same location; for example, the neutron beam detectors 51-54 configured in the four locations shown in Figure 4 can each have multiple units (e.g., two or three). The housing 60 scatters the neutron rays generated in the device body 58 so that the neutron dose rate in the external space E outside the housing 60 is below a predetermined reference value. As shown in Figures 5(a) to 5(c), the housing 60 includes: a side wall portion 61 disposed on the side of the device body 58; a top portion 62 disposed vertically above the device body 58; and a bottom plate portion 63 disposed vertically below the device body. The housing 60 surrounds the generally rectangular internal space F occupied by the device body 58. Neutron scattering components are at least partially installed on the sidewall portion 61, the roof portion 62, and the base plate portion 63. On the other hand, neutron scattering components are not installed on a portion of the housing 60 arranged along a section of the beam line, namely, a portion of the sidewall portion 61, the roof portion 62, and the base plate portion 63. In the drawings, neutron scattering components are provided in the shaded areas, and not in the unshaded areas. At least a portion of each of the side wall portion 61, the roof portion 62, and the bottom plate portion 63 can be constructed in the same manner as the aforementioned storage portion 71 or non-storage portion 72. Furthermore, sliding doors or hinged doors can be installed at any location on the housing 60, and neutron ray scattering components can be mounted on these door structures. The sidewall portion 61 has a first sidewall portion 61a disposed near or around the beam generating unit 12. The beam generating unit 12 is the location through which a low-energy ion beam, before being accelerated to high energy, passes, and therefore cannot serve as a neutron beam source. Furthermore, the first sidewall portion 61a is located at a position 5m to 10m or more away from the neutron beam source, and therefore no neutron beam scattering member is provided. For example, the first sidewall portion 61a is constructed in the same manner as the non-receiving portion 72 described above. The sidewall portion 61 has a second sidewall portion 61b and a third sidewall portion 61c arranged along the beam acceleration unit 14. The second sidewall portion 61b is arranged along the first linear acceleration device 22a and the second linear acceleration device 22b through which the ion beam is accelerated to high energy, and therefore no neutron beam scattering member is provided. On the other hand, the third sidewall portion 61c is the portion arranged along the third linear acceleration device 22c through which the high-energy ion beam is passed, and is arranged near the beam profile slit 23 that can become a neutron beam generation source, and therefore a neutron beam scattering member is provided. The second sidewall portion 61b is constructed, for example, in the same manner as the non-receiving portion 72 described above. The third sidewall portion 61c is constructed, for example, in the same manner as the receiving portion 71 described above. The third sidewall portion 61c is constructed in the same manner as the second receiving portion 71b, and a second neutron beam scattering member 76b with a small thickness can be provided. The sidewall portion 61 has a fourth sidewall portion 61d, a fifth sidewall portion 61e, and a sixth sidewall portion 61f arranged along the beam deflection unit 16. The beam deflection unit 16 has an energy analysis slit 27, a first Faraday cup 28, and a second Faraday cup 31 that can serve as a neutron beam generation source. Therefore, neutron beam scattering members are provided in the sidewall portions 61d to 61f near the beam deflection unit 16. The fourth sidewall portion 61d is positioned near the energy analysis electromagnet 24 where the beam BL is arc-shaped, therefore the distance from the beam BL to the fourth sidewall portion 61d is relatively large. Therefore, a thin neutron ray scattering member is provided in the fourth sidewall portion 61d. Similarly, the sixth sidewall portion 61f is positioned near the deflection electromagnet 30 where the beam BL is arc-shaped, and the distance from the beam BL to the sixth sidewall portion 61f is relatively large, therefore a thin neutron ray scattering member is provided. The fourth sidewall portion 61d and the sixth sidewall portion 61f are constructed in the same manner as the second receiving portion 71b described above, allowing for the provision of a thin second neutron ray scattering member 76b. The fifth sidewall portion 61e is positioned near the transversely converging quadrupole lens 26, the energy analysis slit 27, and the first Faraday cup 28, where the beamline BL is straight, and is parallel to the beamline BL. From the viewpoint of reducing the area occupied by the housing 60, the fifth sidewall portion 61e is positioned close to the beamline BL. The distance from the energy analysis slit 27 and the first Faraday cup 28, which serve as neutron generation sources, to the fifth sidewall portion 61e is small, for example, less than 2m, less than 1.5m, or less than 1m. Furthermore, neutron rays from the energy analysis slit 27 and the first Faraday cup 28 toward the fifth sidewall portion 61e travel in the thickness direction of the fifth sidewall portion 61e, making it difficult to obtain an effective thickness through which the neutron rays pass. Therefore, a neutron scattering member with a large thickness is provided in the fifth sidewall portion 61e, for example, with a thickness of 150mm or more, 200mm or more, or 300mm or more. The fifth sidewall portion 61e is constructed in the same manner as the first receiving portion 71a described above, and a first neutron ray scattering member 76a with a large thickness can be provided. The sidewall portion 61 has a seventh sidewall portion 61g disposed along the beam delivery unit 18. The seventh sidewall portion 61g is disposed near the beam shaper 32, beam scanner 34, and beam parallelizer 36 located upstream of the beam delivery unit 18. Near the seventh sidewall portion 61g are a second Faraday cup 31 and a beam gather 35 that can serve as neutron beam sources, but the distance from these neutron beam sources to the seventh sidewall portion 61g is relatively large. Therefore, a thin neutron beam scattering member is provided on the seventh sidewall portion 61g. The seventh sidewall portion 61g is constructed in the same manner as the second receiving portion 71b described above, allowing for the provision of a thin second neutron beam scattering member 76b. The sidewall portion 61 has an eighth sidewall portion 61h arranged along the final energy filter 38, the implantation processing chamber 40, and the substrate transport device 44. The eighth sidewall portion 61h is located near the beam monitor 42, into which high-energy ion beams can frequently enter. Since the neutron dose rate in the beam monitor 42 is relatively high, a thick neutron beam scattering member is provided. The eighth sidewall portion 61h is constructed in the same manner as the first receiving portion 71a described above, and a thick first neutron beam scattering member 76a can be provided. The side wall portion 61 has a ninth side wall portion 61i arranged to surround the loading port 46. The ninth side wall portion 61i has a portion disposed on the front of the loading port 46 and a portion disposed on the side of the loading port 46. An entrance / exit and a front door to the loading port 46 are provided on the ninth side wall portion 61i. The ninth side wall portion 61i is disposed near the beam monitor 42, therefore a neutron scattering member is provided. The ninth side wall portion 61i is close to the beam monitor 42, therefore it is preferable to provide a neutron scattering member with a large thickness, but if the thickness of the front door is excessively increased, the opening and closing of the front door will require labor, resulting in reduced convenience. Therefore, by arranging additional neutron scattering members 64a and 64b between the beam monitor 42 and the loading port 46, the required thickness of the neutron scattering member of the ninth side wall portion 61i is reduced. The 9th side wall portion 61i is constructed in the same manner as the 2nd storage portion 71b described above, and a second neutron ray scattering member 76b with a small thickness can be provided. Furthermore, neutron scattering members are also provided for the ceiling portion 62 and the base portion 63 from the same perspective as for the side wall portion 61. That is, neutron scattering members are prominently arranged near the neutron ray source, in the portion close to the distance from the neutron ray source to the ceiling portion 62 or the base portion 63, while in other portions the neutron ray scattering members are thinned or not provided at all. In Figure 5(a), the canopy portion 62 has a first canopy portion 62a without neutron beam scattering components and a second canopy portion 62b with neutron beam scattering components. The first canopy portion 62a is arranged upstream of the beam generating unit 12 and the beam accelerating unit 14 (the first linear accelerating device 22a and the second linear accelerating device 22b). The second canopy portion 62b is arranged downstream of the beam accelerating unit 14 (the third linear accelerating device 22c and the beam profile slit 23). The second canopy portion 62b is close to the beam profile slit 23, which can serve as a neutron beam source (for example, within 1 m), so the thickness of the neutron beam scattering components is changed in stages according to the distance from the beam profile slit 23. For example, in the second canopy portion 62b, the number of overlapping plate-shaped neutron beam scattering components increases as the distance from the beam profile slit 23 decreases. In Figure 5(a), the base plate 63 has a first base plate 63a without neutron beam scattering members and a second base plate 63b with neutron beam scattering members. The first base plate 63a is disposed upstream of the beam generating unit 12 and the beam accelerating unit 14. The second base plate 63b is disposed near the beam profile slit 23. From the viewpoint of ensuring a foothold for the mounting device body 58 during operation, it is preferable that the base plate 63 be configured as flat as possible. In other words, it is not ideal for the upper surface of the base plate 63 to be stepped by locally distributing thick neutron beam scattering members. Therefore, by distributing additional neutron beam scattering members 64c and 64d on the lower surface of the device housing the third linear accelerating device 22c and the beam profile slit 23, the required thickness of the neutron beam scattering members in the second base plate 63b is reduced. In Figure 5(b), the canopy portion 62 has a third canopy portion 62c on which a neutron beam scattering member is provided. The third canopy portion 62c is arranged along the beam deflection unit 16. The third canopy portion 62c is configured in the same manner as the second canopy portion 62b, such that the thickness of the neutron beam scattering member increases as the distance from the neutron beam source decreases in the vicinity of the energy analysis slit 27 and the first Faraday cup 28, which can serve as neutron beam generation sources. In Figure 5(b), the base plate 63 has a third base plate 63c on which a neutron beam scattering member is provided. The third base plate 63c is arranged along the beam deflection unit 16. Furthermore, an additional neutron beam scattering member 64e is arranged on the lower surface of the device constituting the beam deflection unit 16. The additional neutron beam scattering member 64e is arranged near the energy analysis slit 27 and the first Faraday cup 28, which can serve as a neutron beam generation source, and is configured such that the thickness of the neutron beam scattering member increases as the distance from the neutron beam generation source decreases. By arranging the additional neutron beam scattering member 64e, the required thickness of the neutron beam scattering member in the third base plate 63c is reduced. In Figure 5(c), the canopy portion 62 has a fourth canopy portion 62d and a fifth canopy portion 62e, each equipped with a neutron beam scattering member. The fourth canopy portion 62d is arranged along the beam delivery unit 18, and the fifth canopy portion 62e is arranged along the substrate handling unit 20. The fourth canopy portion 62d is configured such that the thickness of the neutron beam scattering member increases near the second Faraday cup 31 and the beam gather 35, which can each serve as a neutron beam generation source. Furthermore, an additional neutron beam scattering member 64g is provided near the beam gather 35 on the upper surface of the beam scanner 34. The fifth canopy portion 62e is configured such that the thickness of the neutron beam scattering member increases as it gets closer to the beam monitor 42, which can serve as a neutron beam generation source. In Figure 5(c), the base plate portion 63 has a fourth base plate portion 63d and a fifth base plate portion 63e, on which neutron beam scattering members are provided. The fourth base plate portion 63d is arranged along the beam delivery unit 18, and the fifth base plate portion 63e is arranged along the substrate handling unit 20. The fourth base plate portion 63d is configured such that the thickness of the neutron beam scattering member is uniform. An additional neutron beam scattering member 64f is disposed on the lower surface of the device body 58 near the second Faraday cup 31. By disposing of the additional neutron beam scattering member 64f, the required thickness of the neutron beam scattering member in the fourth base plate portion 63d is reduced. The fifth base plate portion 63e is configured such that the thickness of the neutron beam scattering member increases near the implantation processing chamber 40 where the beam monitor 42 is provided. In addition, no neutron beam scattering member is provided on the base plate portion (sixth base plate portion) 63f of the substrate handling device 44 and the loading port 46. This is because the additional neutron beam scattering member 64a disposed between the implantation processing chamber 40 and the substrate transport device 44 can sufficiently reduce the neutron dose rate from the beam monitor 42 toward the sixth base plate portion 63f. In Figure 5(c), the additional neutron scattering members 64a and 64b provided in the substrate handling unit 20 are configured so as not to obstruct the handling of the wafer W between the implantation processing chamber 40 and the loading port 46. Specifically, the configuration is such that no neutron scattering members are provided on the wafer handling path in the horizontal direction indicated by arrow Z at the height position where the handling port 43 is provided. That is, the additional neutron scattering members 64a and 64b are configured so as not to overlap each other in the horizontal direction. On the other hand, in order to prevent neutron rays from leaking to the outside through the wafer handling path in the horizontal direction indicated by arrow Z, a ninth sidewall portion 61i including neutron scattering members is provided on the front side of the loading port 46. The ninth sidewall portion 61i is configured to partially overlap with the additional neutron scattering members 64a and 64b in the horizontal direction, respectively. In Figure 5(c), the additional neutron scattering member 64b provided in the substrate handling unit 20 is configured so as not to obstruct the handling of the wafer container in the vertical direction indicated by arrow Y passing through the wafer container handling port 47. That is, the additional neutron scattering member 64b is positioned horizontally away from the 9th sidewall portion 61i across the wafer container handling port 47. On the other hand, in order to prevent neutron rays from leaking to the outside through the wafer container handling port 47, the additional neutron scattering member 64b is configured to partially overlap with the 9th sidewall portion 61i in the horizontal direction. Figure 6 is a schematic top view showing the structure of the front door 80 of the loading port 46. The loading port 46 has four mounting platforms 46a-46d arranged in a row along the left-right direction (in the direction of arrow S). An entrance 81 is provided on the front of the loading port 46, surrounded by a portion of the 9th side wall 61i in Figure 4. Two sliding doors 82 and 83 and a hinged door 84 are provided in a manner that allows the entrance 81 to be closed. Neutron ray scattering components are installed on each of the doors 82-84 constituting the front door 80. The first sliding door 82 is configured to slide in the left-right direction along the first guide rail 85 extending in the left-right direction, and the second sliding door 83 is configured to slide in the left-right direction along the second guide rail 86 extending in the left-right direction. The first sliding door 82 and the second sliding door 83 are arranged at different positions in the depth direction; when viewed from the front of the loading port 46, the first sliding door 82 is located on the inner side, and the second sliding door 83 is located on the near-front side. The hinged door 84 is configured to rotate about the hinge 87 provided at the right end of the entrance 81 as an axis of rotation, as indicated by arrow R. In the closed state of the front door 80 as shown in Figure 6, the first sliding door 82 is positioned at the center of the entrance 81, the second sliding door 83 is positioned on the left side of the entrance 81, and the hinged door 84 is positioned on the right side of the entrance 81. In other words, the hinged door 84 closes the right end of the entrance 81, and the two sliding doors 82 and 83 close the remaining part of the entrance 81 that is not closed by the hinged door 84. In the closed state, the first sliding door 82 and the second sliding door 83 are configured to partially overlap in the depth direction, and the first sliding door 82 and the hinged door 84 are also configured to partially overlap in the depth direction. The hinged door 84 is configured such that, in the closed state, its position in the depth direction coincides with that of the second sliding door 83. Figures 7(a) and 7(b) are schematic top views of the front door 80 in its open state. Figure 7(a) shows the state with the left side of the entrance 81 open. The hinged door 84 opens forward, and the first sliding door 82 and the second sliding door 83 slide to the right side of the entrance 81. As a result, the front of the first platform 46a and the second platform 46b located on the left side is open. Figure 7(b) shows the state with the right side of the entrance 81 open. The hinged door 84 opens forward, and the first sliding door 82 and the second sliding door 83 slide to the left side of the entrance 81. As a result, the front of the third platform 46c and the fourth platform 46d located on the right side is open. According to this embodiment, in the loading port 46 provided with four mounting platforms 46a-46d, by combining three doors 82-84, the entire front of any two mounting platforms on the left and right can be opened in the open state, providing ample working space in the left and right directions. Assuming that the front door 80 is composed of only two sliding doors, the two sliding doors are arranged in an overlapping manner near the center of the entrance 81, thus preventing the two central mounting platforms 46b and 46c from opening wide enough. Furthermore, in the case where the front door 80 is composed of three sliding doors, the three sliding doors must be staggered in the depth direction, increasing the overall thickness of the front door 80 in the depth direction. In this embodiment, each door 82-84 constituting the front door 80 is equipped with a thick (e.g., about 200 mm) neutron scattering component, thus increasing the depth of the front door 80 when using three sliding doors. On the other hand, according to this embodiment, by combining two sliding doors and one hinged door, the depth of the front door 80 can be reduced while the entrance 81 can be opened wider. In the front door 80 shown in Figures 6, 7(a), and 7(b), the hinged door 84 is positioned on the right side of the entrance 81. However, the hinged door 84 can also be positioned on the left side of the entrance 81. That is, the front door 80 can also be configured in a symmetrical manner with respect to the structure shown in the figures. Furthermore, it is also possible to configure a first hinged door on the left side of the entrance 81, a second hinged door on the right side of the entrance 81, and a sliding door in the center of the entrance 81. Next, the measurement of neutron rays will be described. The central control unit 50 acquires the measurement values ​​of each of the plurality of neutron ray detectors 51-54 shown in FIG. 4, and monitors the generation of neutron rays. Based on the measurement values ​​of the plurality of neutron ray detectors 51-54, the central control unit 50 infers the location of at least one neutron ray source and infers the intensity of neutron rays radiated from the neutron ray source at the inferred location. For example, if neutron rays are detected by the first neutron ray detector 51 and the second neutron ray detector 52, but not by the third neutron ray detector 53 and the fourth neutron ray detector 54, it can be inferred that a neutron ray source exists upstream of the beamline BL. In this case, by analyzing the values ​​measured by the first neutron ray detector 51 and the second neutron ray detector 52, it is possible to infer which neutron ray source produced the neutron rays. For example, if the measured value of the first neutron ray detector 51 is large and the measured value of the second neutron ray detector 52 is small, it can be inferred that the beam profile slit 23 is the neutron ray source. Furthermore, if the measured value of the first neutron ray detector 51 is small and the measured value of the second neutron ray detector 52 is large, it can be inferred that at least one of the energy analysis slit 27, the first Faraday cup 28, and the second Faraday cup 31 is the neutron ray source. Furthermore, if both the measured values ​​of the first neutron ray detector 51 and the second neutron ray detector 52 are large, it is inferred that the beam profile slit 23, the energy analysis slit 27, the first Faraday cup 28, and the second Faraday cup 31 are all neutron ray sources. Conversely, if no neutron rays are detected by the first neutron ray detector 51 and the second neutron ray detector 52, but neutron rays are detected by the third neutron ray detector 53 and the fourth neutron ray detector 54, it is inferred that there is a neutron ray source downstream of the beamline BL. By inferring the location of the neutron ray source, the intensity of neutron rays radiated from the neutron ray source at the inferred location can also be inferred based on the arrangement and distance of the plurality of neutron ray detectors 51-54 relative to the inferred neutron ray source at the inferred location. The central control device 50 can infer the neutron dose rate distribution in the internal space F inside the housing 60 based on the measurements from a plurality of neutron ray detectors 51-54. The central control device 50 can also infer the neutron dose rate outside the housing 60 based on the measurements from a plurality of neutron ray detectors 51-54. For example, the central control device 50 can infer the location and neutron dose rate of the neutron ray source, and, based on the inferred location and neutron dose rate of the neutron ray source, calculate the neutron dose rate at any location in the external space E or internal space F of the housing 60 through simulation experiments. The calculation of the neutron dose rate inside or outside the housing 60 can be considered by taking into account the configuration of the device body 58, the configuration of the housing 60, the configuration of the neutron ray scattering components installed in the housing 60, and the configuration of the neutron ray scattering components installed separately from the housing 60. If the calculated neutron dose rate inside or outside the housing 60 exceeds a predetermined upper limit, the central control device 50 may output a warning, temporarily stop the output of the ion beam, or change the operating conditions of at least one of the plurality of devices constituting the device body 58 so that the neutron dose rate does not reach the upper limit. The central control unit 50 can monitor at least one of a plurality of devices arranged along the beamline BL based on the measurements of a plurality of neutron ray detectors 51-54. Specifically, it can detect anomalies in at least one of the plurality of devices constituting the device body 58, or determine which of the plurality of devices requires maintenance. The central control unit 50 can use information related to the operating mode of the device body 58 to determine whether the at least one device being monitored is normal or abnormal. This is because, depending on the operating mode of the device body 58, the location of the neutron ray source and the neutron dose rate generated at the neutron ray source may differ. Hereinafter, referring to Figures 8-14, the operating modes that enable the generation of neutron rays will be explained. Figure 8 is a flowchart illustrating the ion implantation process of the embodiment, showing the process of implanting ions into wafer W after adjusting the ion beam. Figures 9-14 schematically show the operation mode of the device body 58, the position of the neutron beam generation source, and the neutron beams 90-97 detected by the plurality of neutron beam detectors 51-54 in each step. In Figures 9-14, the reach of the ion beam through the beamline BL is indicated by thick lines, and the main neutron beam generation source is highlighted in black. First, in step 1 (S10) of Figure 8, the beam energy is adjusted. Figure 9 schematically shows the ion implantation device 100 in step 1. Step 1 is performed in the following state (also referred to as the first operating mode): the beam profile slit 23 is inserted into the beam line BL, the slit width of the energy analysis slit 27 is narrowed, and the first Faraday cup 28 is inserted into the beam line BL. In step 1, it is possible for a high-energy ion beam to collide with the beam profile slit 23, the energy analysis slit 27, and the first Faraday cup 28 to generate neutron rays. Therefore, in step 1, the beam profile slit 23, the energy analysis slit 27, and the first Faraday cup 28 can become neutron ray sources. At this time, the neutron rays 90 generated in the beam profile slit 23 are mainly detected by the first neutron ray detector 51. Furthermore, the neutron rays 91 generated in the energy analysis slit 27 and the first Faraday cup 28 are primarily detected by the second neutron ray detector 52. Additionally, the neutron rays 90 generated in the beam profile slit 23 can also be detected by the second neutron ray detector 52. Similarly, the neutron rays 91 generated in the energy analysis slit 27 and the first Faraday cup 28 can also be detected by the first neutron ray detector 51. Next, in step 2 (S12) of Figure 8, the beam current is adjusted using the first Faraday cup 28. Figure 10 schematically shows the ion implantation device 100 in step 2. Step 2 is performed in the following state (also referred to as the second operating mode): the beam profile slit 23 is retracted from the beam line BL, the slit width of the energy analysis slit 27 is widened to its normal width, and the first Faraday cup 28 is inserted into the beam line BL. Step 2 becomes the same operating mode as step 1 of Figure 9, but the high-energy ion beam does not collide with the beam profile slit 23, and the high-energy ion beam is unlikely to collide with the energy analysis slit 27. As a result, in step 2, the high-energy ion beam essentially only collides with the first Faraday cup 28, and the first Faraday cup 28 can become a neutron beam generation source. The neutron beam 92 generated by the first Faraday cup 28 can be detected by the first neutron beam detector 51 and the second neutron beam detector 52. In step 2, more high-energy ion beams are injected into the first Faraday cup 28, so the dose rate of neutron rays 92 that can be generated in the first Faraday cup 28 is higher than that in step 1. Next, in step 3 (S14) of Figure 8, the beam current is adjusted using the second Faraday cup 31. Figure 11 schematically shows the ion implantation device 100 in step 3. Step 3 is performed in the following state (also referred to as the third operating mode): the first Faraday cup 28 is withdrawn from the beam line BL, and the second Faraday cup 31 is inserted into the beam line BL. In step 3, the ion beam collides with the second Faraday cup 31, thus the second Faraday cup 31 can become the main neutron beam source. The neutron beam 93 generated by the second Faraday cup 31 is mainly detected by the first neutron beam detector 51 and the second neutron beam detector 52. At this time, the dose rate of neutron ray 93 detected by the second neutron ray detector 52 located near the second Faraday cup 31 is relatively large, while the dose rate of neutron ray 93 detected by the first neutron ray detector 51 located away from the second Faraday cup 31 is relatively small. Next, in step 4 (S16) of Figure 8, the beam current is adjusted using the beam monitor 42. Figure 12 schematically shows the ion implantation device 100 in step 4. Step 4 is performed in a non-scanning state (also known as the fourth operating mode) where the second Faraday cup 31 is withdrawn from the beam line BL, and the ion beam is not reciprocated by the beam scanner 34. In step 4, the ion beam collides with the beam monitor 42, thus the beam monitor 42 can become the main neutron beam generation source. The neutron beam 94 generated by the beam monitor 42 is mainly detected by the third neutron beam detector 53 and the fourth neutron beam detector 54. At this time, the dose rate of the neutron beam 94 detected by the fourth neutron beam detector 54, which is located near the beam monitor 42, is relatively high, while the dose rate of the neutron beam 94 detected by the third neutron beam detector 53, which is located away from the beam monitor 42, is relatively low. Next, in step 5 (S18) of Figure 8, the ion beam is temporarily withdrawn from the beamline BL, and the wafer W to be implanted with ions is moved into the implantation processing chamber 40. Figure 13 schematically shows the ion implantation device 100 in step 5. In step 5, the ion beam is deflected using the beam scanner 34, so that the ion beam enters the cluster 35 (also known as the fifth operating mode). Therefore, in step 5, the cluster 35 can become the main source of neutron radiation. The neutron radiation 95 generated in the cluster 35 is mainly detected by the first neutron radiation detector 51, the second neutron radiation detector 52, and the third neutron radiation detector 53. At this time, the dose rate of neutron ray 95 detected by the third neutron ray detector 53 located near the cluster 35 is relatively large, while the dose rate of neutron ray 95 detected by the first neutron ray detector 51 and the second neutron ray detector 52 located away from the cluster 35 is relatively small. Next, in step 6 (S20) of Figure 8, an ion beam, reciprocatingly scanned by beam scanner 34, is irradiated onto wafer W to perform ion implantation. Figure 14 schematically shows the ion implantation device 100 in step 6. In step 6, the ion beam is reciprocatedly scanned by beam scanner 34, resulting in the ion beam entering the left and right Faraday cups 39L and 39R. Also, in step 6, at least a portion of the ion beam that does not enter wafer W while wafer W is reciprocating in the vertical direction enters beam monitor 42 (also referred to as the sixth operating mode). Therefore, in step 6, the left and right Faraday cups 39L and 39R and beam monitor 42 can become the main sources of neutron radiation. The neutron radiation 96 generated by the left and right Faraday cups 39L and 39R is mainly detected by the third neutron radiation detector 53, and the neutron radiation 97 generated by beam monitor 42 is mainly detected by the fourth neutron radiation detector 54. In addition, in step 6, a portion of the ion beam that reaches the implantation processing chamber 40 is injected into the beam monitor 42. Therefore, compared with step 4, the neutron dose rate generated by the beam monitor 42 is lower, and the dose rate of neutron ray 97 detected by the fourth neutron ray detector 54 is also lower. In addition to the operation modes corresponding to steps 1 to 6 respectively, the device body 58 can also adopt various operation modes depending on the state of the device body 58. As described above, if the operating mode of the device body 58 changes, the location that can become a neutron beam generation source changes, and the neutron dose rate generated by the neutron beam generation source may also change. Therefore, the central control device 50 performs anomaly detection corresponding to the operating mode of the device body 58. The central control device 50 monitors the device based on information related to the operating mode of the device body 58 and the measurement value of at least one neutron beam detector under a predetermined operating mode. For example, the benchmark for anomaly detection varies depending on the operating mode, and a benchmark corresponding to the operating mode can be used to monitor at least one of the plurality of devices. Furthermore, if the measurement value of at least one neutron beam detector exceeds the benchmark value defined for a predetermined operating mode, the operating conditions of at least one of the plurality of devices can be changed to bring the measurement value below the benchmark value. For example, the operating conditions can be changed to reduce the neutron dose rate, or the beam output can be temporarily stopped to prevent the generation of neutron beams. In the first operating mode of Figure 9 or the second operating mode of Figure 10, neutron rays 90, 91, and 92 may be detected by the first neutron ray detector 51 and the second neutron ray detector 52. On the other hand, it is normal that no neutron rays are detected by the third neutron ray detector 53 and the fourth neutron ray detector 54. Therefore, in the first and second operating modes, the upper limit values ​​of the first neutron ray detector 51 and the second neutron ray detector 52 are set high, and the upper limit values ​​of the third neutron ray detector 53 and the fourth neutron ray detector 54 are set low (e.g., near the background noise level). In this way, if neutron rays are detected by the third neutron ray detector 53 or the fourth neutron ray detector 54, an anomaly in the ion implantation device 100 can be detected. By using the first neutron ray detector 51 and the second neutron ray detector 52, the beam energy and beam current can be adjusted while monitoring the neutron rays generated by at least one of the beam acceleration unit 14 and the beam deflection unit 16. Therefore, if the measured value of the first neutron ray detector 51 or the second neutron ray detector 52 exceeds the upper limit, an anomaly can be detected in the adjustment step of the first or second operating mode. In the third operating mode shown in Figure 11, the second Faraday cup 31 can become the main neutron radiation source. Therefore, it is normal for the first neutron radiation detector 51 and the second neutron radiation detector 52 to either not detect neutron radiation or to detect only trace amounts of neutron radiation. For example, it is normal for the neutron dose rate detected by the first neutron radiation detector 51, which is positioned away from the second Faraday cup 31, to be lower than the neutron dose rate detected by the second neutron radiation detector 52, which is positioned near the second Faraday cup 31. Therefore, in the third operating mode, the beam current can be adjusted while monitoring the neutron radiation generated by the second Faraday cup 31, which is located downstream of the energy analyzer, using both the first neutron radiation detector 51 and the second neutron radiation detector 52. In the fourth operating mode shown in Figure 12, the beam monitor 42 can become the primary neutron radiation source. Therefore, it is possible to detect neutron radiation using the third neutron radiation detector 53 and the fourth neutron radiation detector 54. On the other hand, it is normal that no neutron radiation is detected by the first neutron radiation detector 51 and the second neutron radiation detector 52. Therefore, in the fourth operating mode, the upper limits of the first neutron radiation detector 51 and the second neutron radiation detector 52 can be set low (e.g., near the background noise level), while the upper limits of the third neutron radiation detector 53 and the fourth neutron radiation detector 54 can be set high. In the fourth operating mode, the beam current can be adjusted while monitoring the neutron radiation generated by the beam monitor 42 using the third neutron radiation detector 53 and the fourth neutron radiation detector 54. In the fifth operating mode shown in Figure 13, the beam gatherer 35 can become the primary neutron radiation source. Therefore, it is normal for the first neutron radiation detector 51, the second neutron radiation detector 52, or the third neutron radiation detector 53 to either not detect neutron radiation or to detect only trace amounts of neutron radiation. For example, it is normal for the neutron dose rate detected by the first neutron radiation detector 51 and the second neutron radiation detector 52, which are positioned away from the beam gatherer 35, to be lower than the neutron dose rate detected by the third neutron radiation detector 53, which is positioned near the beam gatherer 35. Therefore, in the fifth operating mode, the first neutron radiation detector 51, the second neutron radiation detector 52, and the third neutron radiation detector 53 can be used to measure the neutron radiation generated in the beam gatherer 35 while monitoring whether the beam has been properly backed away. In the fifth operating mode, if neutron rays are detected by the fourth neutron ray detector 54, it can be considered that some kind of abnormality has occurred in the beam avoidance, and the wafer loading and unloading will be stopped. In the sixth operating mode shown in Figure 14, the left and right Faraday cups 39L and 39R and the beam monitor 42 can become the main neutron beam generation sources. Therefore, similar to the fourth operating mode, the third and fourth neutron beam detectors 53 and 54 can be used to measure neutron beams while monitoring whether ion implantation has been properly performed. Even if the left and right Faraday cups 39L and 39R and the beam monitor 42 do not generate neutron beams, an anomaly may occur in the final energy filter 38, and the high-energy ion beam may collide with the AEF electrode pair, making the final energy filter 38 a neutron beam generation source. Suppose that an anomaly occurs and neutron beams are generated in the final energy filter 38, and the neutron dose rate increases as detected by the third neutron beam detector 53. Therefore, if the neutron dose rate measured by the third neutron beam detector 53 exceeds the upper limit limit for the sixth operating mode, it can be considered that an anomaly has occurred in the final energy filter 38, and the ion implantation process is stopped. The central control device 50 can accumulate measurement values ​​from multiple neutron ray detectors 51-54 and analyze the relationship between the measurement values ​​of each detector under the aforementioned multiple operating modes and their changes over time. For example, it can accumulate relevant data on the operating modes of the device body 58 and the measurement values ​​of multiple neutron ray detectors 51-54 under predetermined operating modes, and infer the status of each device constituting the device body 58 based on the accumulated relevant data. As for the status of each device, for example, it can be inferred whether it is in a condition requiring maintenance at the current point in time, and it can also be inferred when future maintenance is required. As the amount of boron accumulated in the neutron ray source increases due to the long-term use of the device, the neutron dose rate generated by the neutron ray source increases. Therefore, it is possible to infer whether maintenance is required and when maintenance is required by analyzing the increasing trend of the neutron dose rate measured by the detectors. The central control device 50 can detect anomalies in at least one neutron beam detector based on the operating mode of the device body 58 and the measured values ​​of a plurality of neutron beam detectors 51-54 under a predetermined operating mode. Normally, to detect anomalies in a neutron beam detector, a plurality of neutron beam detectors must be positioned at the same location and measured under the same conditions. However, in cases like this embodiment where there are multiple neutron beam sources, and therefore neutron beams must be measured at multiple locations, configuring a plurality of neutron beam detectors at each location would significantly increase costs. Therefore, in this embodiment, anomalies in at least one neutron beam detector can be detected based on the measured values ​​of a plurality of neutron beam detectors 51-54 positioned at different locations. In each of the aforementioned operating modes, the location of the primary neutron radiation source is determined for each mode, and the distance from the neutron radiation source to each neutron radiation detector 51-54 is also fixed. Therefore, the proportion of the measured values ​​of each neutron radiation detector 51-54 under a given operating mode remains approximately constant. Thus, in cases where the measured values ​​deviate from the proportion of the measured values ​​of each neutron radiation detector 51-54 defined for each operating mode, an anomaly in the detector itself can be detected, or an anomaly in the detector can be inferred. Furthermore, by calculating and comparing the proportions of the measured values ​​of each neutron radiation detector 51-54 under multiple operating modes, an anomaly in the detector can be inferred. According to this embodiment, the location that can become a neutron radiation source is inferred based on the operating mode. Therefore, neutron radiation within the device can be appropriately monitored using neutron radiation detectors 51-54 located at a number fewer positions (e.g., 4) than the assumed number of neutron radiation sources (e.g., 8). That is, compared to the case where neutron radiation detectors are arranged in a one-to-one correspondence between neutron radiation sources at multiple locations, the number of neutron radiation detectors can be reduced, and the increased cost caused by arranging a large number of neutron radiation detectors can be prevented. In the above embodiments, a plate-shaped or block-shaped neutron scattering component is shown mounted on the device body 58 and the housing 60. In variations, granular, gel-like, or paste-like neutron scattering components can be provided. For example, gel-like or paste-like neutron scattering components can be coated or filled on the surfaces and gaps of the device body 58 and the housing 60. Furthermore, granular neutron scattering components can be filled into the cavities in the support structure of the device body 58 and the housing 60. One aspect of this embodiment is as follows. (Item 1-1) An ion implantation device, characterized by comprising: a device body including a plurality of units arranged along a beamline of a delivered ion beam and a substrate transport processing unit arranged at the downstream end of the aforementioned beamline, and having a neutron beam generating source capable of generating neutron beams by collision with a high-energy ion beam; a housing that at least partially surrounds the aforementioned device body; and a neutron beam scattering member arranged at a position where neutron beams emitted from the aforementioned neutron beam generating source can penetrate along a direction where the distance from the aforementioned neutron beam generating source to the aforementioned housing is predetermined. (Item 1-2) The ion implantation device as described in Item 1-1 is characterized in that the aforementioned neutron ray scattering component includes: a first neutron ray scattering component, which is disposed at a position where neutron rays emitted from the aforementioned neutron ray generation source can penetrate along a first direction in which the distance from the aforementioned neutron ray generation source to the aforementioned housing is a first distance; and a second neutron ray scattering component, which is disposed at a position where neutron rays emitted from the aforementioned neutron ray generation source can penetrate along a second direction in which the distance from the aforementioned neutron ray generation source to the aforementioned housing is a second distance greater than the aforementioned first distance, and the thickness is smaller than that of the aforementioned first neutron ray scattering component. (Item 1-3) An ion implantation device as described in Item 1-1 or Item 1-2, characterized in that the aforementioned neutron ray scattering member is disposed at a position in which neutron rays emitted from the aforementioned neutron ray generating source can enter along a first direction where the distance from the aforementioned neutron ray generating source to the aforementioned housing is a first distance; on the other hand, it is not disposed at a position in which neutron rays emitted from the aforementioned neutron ray generating source can enter along a third direction where the distance from the aforementioned neutron ray generating source to the aforementioned housing is a third distance greater than the aforementioned first distance. (Item 1-4) An ion implantation device as described in any one of Items 1-1 to 1-3, characterized in that the aforementioned neutron ray generating source is at least one of a slit in the aforementioned beamline, a beam monitor, and a beam gather. (Item 1-5) An ion implantation device as described in any one of Items 1-1 to 1-4, characterized in that at least a portion of the aforementioned neutron ray scattering member is mounted in the aforementioned housing. (Items 1-6) An ion implantation device as described in Items 1-5, characterized in that at least a portion of the aforementioned neutron beam scattering member is installed in a door disposed in the aforementioned housing. (Item 1-7) An ion implantation device as described in any one of Items 1-1 to 1-6, characterized in that at least a portion of the aforementioned neutron beam scattering member is installed in at least one of the aforementioned device body and the supporting structure of the aforementioned device body. (Item 1-8) An ion implantation device as described in any one of Items 1-1 to 1-7, characterized in that the aforementioned neutron beam scattering member is not installed in a portion of the aforementioned housing disposed along a portion of the aforementioned beam line.(Items 1-9) The ion implantation device as described in items 1-8 is characterized in that the aforementioned plurality of units comprises: a beam acceleration unit, which accelerates an ion beam drawn from an ion source to generate the aforementioned high-energy ion beam; and a beam delivery unit, which delivers the aforementioned high-energy ion beam to the aforementioned substrate transport processing unit, wherein the aforementioned neutron ray scattering member is at least partially mounted in a portion of the aforementioned housing arranged along the aforementioned beam delivery unit, and at least partially not mounted in a portion of the aforementioned housing arranged along the aforementioned beam acceleration unit. (Item 1-10) The ion implantation device as described in items 1-9 is characterized in that the aforementioned plurality of units further comprises a beam deflection unit, wherein the aforementioned beam deflection unit connects the aforementioned beam acceleration unit and the aforementioned beam delivery unit, wherein the aforementioned beam line is U-shaped by the straight aforementioned beam acceleration unit, the curved aforementioned beam deflection unit and the straight aforementioned beam delivery unit, and the aforementioned neutron ray scattering member is at least partially mounted in a portion of the aforementioned housing arranged along the aforementioned beam deflection unit. (Item 1-11) An ion implantation apparatus as described in any one of items 1-1 to 1-10, characterized in that the aforementioned substrate transport processing unit comprises: an implantation processing chamber for performing an implantation process in which the aforementioned high-energy ion beam is irradiated onto a wafer; a loading port for holding a wafer container capable of accommodating a plurality of wafers; and a substrate transport device for transporting wafers between the aforementioned implantation processing chamber and the aforementioned wafer container, the aforementioned housing having a wafer container transport port, the aforementioned wafer container transport port being configured such that the aforementioned wafer container can pass through in a vertical direction above the aforementioned loading port, and the aforementioned neutron beam scattering member being configured not to obstruct the transport of the aforementioned wafer container in the aforementioned wafer container transport port. (Item 1-12) An ion implantation apparatus as described in item 1-11, characterized in that a portion of the aforementioned neutron beam scattering member is configured to overlap in a horizontal direction across the aforementioned wafer container transport port. (Item 1-13) The ion implantation device as described in Item 1-11 or Item 1-12 is characterized in that the aforementioned housing has: an inlet / outlet located on the front of the aforementioned loading port; a hinged door that closes the right or left end of the aforementioned inlet / outlet; and two sliding doors that close the remaining portion of the aforementioned inlet / outlet not closed by the aforementioned hinged door, wherein the aforementioned neutron ray scattering member is mounted on both the aforementioned hinged door and the aforementioned sliding door. (Item 1-14) The ion implantation device as described in Item 1-11 or Item 1-12 is characterized in that the aforementioned housing has: an inlet / outlet located on the front of the aforementioned loading port; two hinged doors that close the right and left ends of the aforementioned inlet / outlet; and a sliding door that closes the center of the aforementioned inlet / outlet not closed by the aforementioned two hinged doors, wherein the aforementioned neutron ray scattering member is mounted on both the aforementioned hinged door and the aforementioned sliding door.(Item 1-15) The ion implantation device as described in any one of items 1-1 to 1-14 is characterized in that the aforementioned housing comprises: a side wall portion disposed on the side of the aforementioned device body; a top portion disposed vertically above the aforementioned device body; and a bottom plate portion disposed vertically below the aforementioned device body, wherein the aforementioned side wall portion, the aforementioned top portion, and the aforementioned bottom plate portion respectively have a portion for installing the aforementioned neutron ray scattering component and a portion for not installing the aforementioned neutron ray scattering component. (Item 1-16) The ion implantation device as described in any one of items 1-1 to 1-15 is characterized in that the aforementioned neutron ray scattering component has a hydrogen atom content of 0.08 g / cm³. 3 ~ 0.15g / cm 3 The material composition of the ion implantation device as described in any one of items 1-1 to 1-16 is characterized in that the aforementioned neutron scattering member comprises a polyolefin. (Item 1-18) The ion implantation device as described in item 1-17 is characterized in that the aforementioned neutron scattering member further comprises boron atoms. (Item 1-19) The ion implantation device as described in any one of items 1-1 to 1-18 is characterized in that at least a portion of the aforementioned neutron scattering member is plate-shaped or block-shaped. (Item 1-20) The ion implantation device as described in item 1-19 is characterized in that a non-combustible sheet is mounted on the surface of the aforementioned plate-shaped or block-shaped neutron scattering member. (Item 1-21) The ion implantation device as described in any one of items 1-1 to 1-20 is characterized in that at least a portion of the aforementioned neutron scattering member is granular, gel-shaped, or paste-shaped. (Item 1-22) An ion implantation device as described in any one of items 1-1 to 1-21, characterized in that it further comprises an X-ray shielding member mounted on the aforementioned housing. (Item 1-23) An ion implantation device as described in any one of items 1-1 to 1-22, characterized in that the aforementioned high-energy ion beam comprises boron ions with an energy of 4 MeV or higher. Another embodiment of this invention is as follows. (Item 2-1) An ion implantation device, characterized by comprising: a plurality of devices arranged along a beamline of an ion beam; a plurality of neutron beam detectors arranged at a plurality of positions near the aforementioned beamline to measure neutron beams generated at a plurality of locations along the aforementioned beamline by collision with a high-energy ion beam; and a control device that monitors at least one of the plurality of devices based on the measurement value of at least one of the plurality of neutron beam detectors. (Item 2-2) The ion implantation device as described in Item 2-1, characterized in that the control device infers the location of a neutron beam generation source at at least one location along the aforementioned beamline based on the measurement values ​​of the aforementioned plurality of neutron beam detectors. (Item 2-3) The ion implantation device as described in Item 2-1 or Item 2-2, characterized in that the control device infers the intensity of neutron beams radiated from a neutron beam generation source at at least one location along the aforementioned beamline based on the measurement values ​​of the aforementioned plurality of neutron beam detectors. (Item 2-4) An ion implantation device as described in any one of items 2-1 to 2-3, characterized in that at least one of the plurality of neutron beam detectors is disposed near at least one of the slits, beam monitors, and beam gathers of the aforementioned beamline. (Item 2-5) An ion implantation device as described in any one of items 2-1 to 2-4, characterized in that the aforementioned control device detects an anomaly of at least one of the aforementioned plurality of devices based on information related to the operating mode of the aforementioned plurality of devices and the measured value of at least one neutron beam detector under a predetermined operating mode. (Item 2-6) An ion implantation device as described in item 2-5, characterized in that when the measured value of at least one neutron beam detector exceeds a reference value defined corresponding to the aforementioned predetermined operating mode, the aforementioned control device changes the operating conditions of at least one of the aforementioned plurality of devices so that the measured value becomes below the aforementioned reference value. (Item 2-7) An ion implantation device as described in any one of items 2-1 to 2-6, characterized in that the aforementioned control device accumulates relevant data on the operating modes of the aforementioned plurality of devices and the measured values ​​of the aforementioned plurality of neutron radiation detectors under a predetermined operating mode, and infers which of the aforementioned plurality of devices requires maintenance based on the accumulated relevant data. (Item 2-8) An ion implantation device as described in item 2-7, characterized in that the aforementioned control device infers the maintenance period of at least one of the aforementioned plurality of devices based on the aforementioned accumulated relevant data. (Item 2-9) An ion implantation device as described in any one of items 2-1 to 2-8, characterized in that the aforementioned control device detects an anomaly of at least one of the aforementioned plurality of devices based on information related to the operating modes of the aforementioned plurality of devices and the measured values ​​of at least two or more neutron radiation detectors under a predetermined operating mode.(Item 2-10) An ion implantation device as described in any one of items 2-1 to 2-9, characterized in that the aforementioned plurality of devices includes: a beam acceleration device for accelerating an ion beam drawn from an ion source to generate the aforementioned high-energy ion beam; and an energy analysis device disposed downstream of the aforementioned beam acceleration device, wherein the aforementioned control device uses at least two or more neutron ray detectors to monitor the generation of neutron rays in at least one of the aforementioned beam acceleration device and the aforementioned energy analysis device, while adjusting at least one of the energy of the ion beam output from the aforementioned energy analysis device and the beam current. (Item 2-11) The ion implantation device as described in Item 2-10 is characterized in that the plurality of neutron beam detectors include: a first detector disposed near the slit at the exit of the aforementioned beam acceleration device; and a second detector disposed near the slit at the exit of the aforementioned energy analysis device and the beam monitor, wherein the aforementioned control device uses the aforementioned first detector and the aforementioned second detector to monitor for neutron beams that can be generated in at least one of the aforementioned beam acceleration device and the aforementioned energy analysis device. (Item 2-12) The ion implantation device as described in Item 2-11 is characterized in that the aforementioned control device uses the aforementioned first detector and the aforementioned second detector to monitor for neutron beams that can be generated downstream of the aforementioned beam line, further than the aforementioned energy analysis device. (Item 2-13) An ion implantation device as described in any one of items 2-1 to 2-12, characterized in that the plurality of devices includes a beam deflection device, which applies at least one of an electric field and a magnetic field to the ion beam to deflect the ion beam away from a beam stack located away from the beam line, and the control device uses at least two or more neutron ray detectors to monitor neutron rays that can be generated in the beam stack when the ion beam is deflected by the beam deflection device. (Item 2-14) An ion implantation device as described in any one of items 2-1 to 2-13, characterized in that the plurality of neutron beam detectors includes: a third detector disposed upstream of a beam monitor disposed near the implantation site of the wafer irradiated by the aforementioned ion beam; and a fourth detector disposed downstream of the aforementioned beam monitor disposed near the aforementioned implantation site, wherein the control device uses the aforementioned third detector and the aforementioned fourth detector to monitor neutron beams generated by the aforementioned beam monitor disposed near the aforementioned implantation site. (Item 2-15) An ion implantation device as described in any one of items 2-1 to 2-14, characterized in that the control device detects an anomaly of at least one neutron beam detector based on information related to the operating mode of the plurality of devices and the measured values ​​of the plurality of neutron beam detectors under a predetermined operating mode.(Item 2-16) An ion implantation device as described in any one of items 2-1 or 2-15, characterized in that it further comprises a housing surrounding the plurality of devices and the plurality of neutron beam detectors, wherein the control device infers the neutron dose rate outside the housing based on the measured values ​​of the plurality of neutron beam detectors. (Item 2-17) An ion implantation device as described in item 2-16, characterized in that the control device infers the neutron dose rate outside the housing based on the configuration of at least one of the neutron beam scattering material contained in the housing and the neutron beam scattering material disposed near the beam. (Item 2-18) An ion implantation device as described in item 2-16 or 2-17, characterized in that when the inferred neutron dose rate outside the housing exceeds a predetermined upper limit, the control device changes the operating conditions of at least one of the plurality of devices to reduce the neutron dose rate outside the housing. (Item 2-19) An ion implantation device as described in any one of items 2-16 to 2-18, characterized in that the control device infers the dose rate distribution of neutron rays inside the housing based on the measurement values ​​of the plurality of neutron ray detectors. (Item 2-20) An ion implantation device as described in any one of items 2-1 to 2-19, characterized in that the high-energy ion beam contains boron (B) ions with an energy of 4 MeV or higher. (Item 2-21) An ion implantation method, characterized in that it includes the following steps: using a plurality of neutron ray detectors disposed at a plurality of positions near the beamline of the ion beam, measuring neutron rays that can be generated at a plurality of locations along the beamline by the collision of the high-energy ion beam; and monitoring at least one of a plurality of devices disposed along the beamline based on the measurement value of at least one of the plurality of neutron ray detectors. The method for monitoring neutron rays will now be described in further detail. As mentioned above, the dose rate of neutron rays generated in the ion implantation device 100 is not very high, and can be close to the detection limit of a typical neutron ray detector. Furthermore, the neutron dose rate measured in neutron ray detectors 51-54 may vary depending on the various operating modes shown in Figures 9-14. Moreover, as the amount of boron accumulated near the surface of the neutron ray source increases due to long-term use of the device, the neutron dose rate generated at the neutron ray source increases. Therefore, it is not easy to confirm the integrity of the measurements in neutron ray detectors 51-54 based solely on the measured values ​​of the neutron dose rate. Therefore, in this embodiment, the current neutron dose rate is inferred using time-series data of previously measured neutron dose rates. The current measured neutron dose rate is compared with the inferred value to determine the validity of the current measured neutron dose rate. In other words, a benchmark value for evaluating the validity of the current neutron dose rate measurement is determined based on the current trend of the neutron dose rate, and this trend-based benchmark value is used to confirm the soundness of any abnormal measurements in the neutron radiation detectors 51-54. In this embodiment, the benchmark value is dynamically changed based on the trend, thus allowing for more appropriate confirmation of the soundness of the measurements taken by the neutron radiation detectors 51-54. Figure 15 is a schematic diagram showing the structure of the central control unit 50. The central control unit 50 includes: a processor 50a such as a CPU (Central Processing Unit); memory 50b such as ROM (Read Only Memory) and RAM (Random Access Memory); and recording devices 50c such as HDD (Hard Disk Drive) and SSD (Solid State Drive). The central control device 50, for example, executes a program stored in memory 50b via processor 50a, and controls all operations of the ion implantation device 100 according to the program. Processor 50a can execute programs stored in any storage device different from memory 50b, programs retrieved from any recording medium via a reading device, or programs retrieved via a network. Memory 50b storing the program can be volatile memory such as DRAM (Dynamic Random Access Memory), or non-volatile memory such as EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory, magnetoresistive memory, resistive random access memory, or ferroelectric random access memory. Non-volatile memory, magnetic recording media such as magnetic tapes and magnetic disks, and optical recording media such as optical discs are examples of nontransitory and tangible computer-readable storage media. The various functions provided by the central control unit 50 can be implemented by a single device equipped with a processor 50a and a memory 50b, or by a protocol implemented by a plurality of devices each equipped with a processor 50a and a memory 50b. The recording device 50c records data representing the operational performance of the ion implantation device 100. The recording device 50c can be installed within the central control unit 50, or it can be installed as an external device separate from the central control unit 50. Figure 16 is a block diagram schematically showing the functional structure of the central control unit 50. The central control unit 50 includes an operation mode control unit 102, a dose rate acquisition unit 104, a dose rate recording unit 106, a dose rate inference unit 108, a comparison unit 110, and a determination unit 112. Each functional block shown in Figure 16 is implemented by the processor 50a executing a program stored in the memory 50b. The operation mode control unit 102 controls the operation of the device body 58 according to the operation mode. For example, the operation mode control unit 102 selects at least one of the plurality of operation modes provided by the ion implantation device 100, and causes the device body 58 to operate according to the selected operation mode. Examples of the plurality of operation modes are the first to sixth operation modes shown in Figures 9 to 14. When the device body 58 operates in any of the plurality of operating modes, the ion beam delivered along the beam line BL is at least partially injected into at least one of the plurality of locations within the ion implantation device 100. Here, the plurality of locations where the ion beam is at least partially injected refers to at least a portion of the surface of the slit, beam monitor, and beam gather, which are components capable of serving as the aforementioned neutron generation source. Specific examples of the plurality of components include the beam profile slit 23, the energy analysis slit 27, the first Faraday cup 28, the second Faraday cup 31, the beam gather 35, the left and right Faraday cups 39L and 39R, and the beam monitor 42, but are not limited to these. In at least one of a plurality of operating modes, a driving device is used to position at least one of a plurality of portions on the beamline BL, thereby at least partially blocking the ion beam by means of at least one of the plurality of portions. The driving device is configured to change the position of at least one of the plurality of portions. Figures 17(a) and 17(b) are schematic diagrams illustrating a drive device 122 that alters the position of the portion 120 where the ion beam IB is at least partially injected. The drive device 122 is configured to change the position of the member 124 having the portion 120 where the ion beam IB is partially injected. The drive device 122 can change the position of the portion 120 between a state where the portion 120 is inserted into the beam line BL as shown in Figure 17(a) and a state where the portion 120 is retracted from the beam line BL as shown in Figure 17(b). The drive device 122 can change the position and range of the ion beam IB injection in the portion 120 by moving the portion 120 in a direction intersecting the beam line BL (e.g., the direction of arrow A). For example, in the first operating mode described above, the beam profile slit 23 is inserted into the beamline BL by the driving device, thereby at least partially blocking the ion beam. For example, in the first operating mode described above, the slit width of the energy analysis slit 27 is changed by the driving device, thereby at least partially blocking the ion beam. In the first and second operating modes described above, the first Faraday cup 28 is inserted into the beamline BL by the driving device, thereby at least partially blocking the ion beam. In the third operating mode described above, the second Faraday cup 31 is inserted into the beamline BL, thereby at least partially blocking the ion beam. In at least one of a plurality of operating modes, the ion beam is deflected by a deflection device, and the ion beam is injected into at least one of a plurality of locations located away from the beam line BL. Figures 18(a) and 18(b) are schematic diagrams of a deflection device 126 for deflecting the ion beam IB. The deflection device 126 is configured to apply at least one of an electric field and a magnetic field to deflect the trajectory of the ion beam IB. The deflection device 126 may be configured to switch between a state in which the ion beam IB is injected into the location 128 located away from the beam line BL as shown in Figure 18(a) and a state in which the ion beam IB is not injected into the location 128 located away from the beam line BL as shown in Figure 18(b). Specific examples of the deflection device 126 include an energy analysis electromagnet 24, a deflection electromagnet 30, a beam scanner 34, a beam parallelizer 36, and a final energy filter 38, but it is not limited to these. For example, in the first operating mode described above, the ion beam is deflected by the energy analysis electromagnet 24, and the ion beam is injected into the energy analysis slit 27 located away from the beam line BL. For example, in the fifth operating mode described above, the ion beam is deflected by the beam scanner 34, and the ion beam is injected into the beam gather 35 located away from the beam line BL. For example, in the sixth operating mode described above, the ion beam is deflected (more specifically, reciprocated scanned) by the beam scanner 34, and the ion beam is injected into the left and right Faraday cups 39L and 39R located away from the beam line BL. In at least one of a plurality of operating modes, the ion beam is at least partially incident on a first location, and at least partially incident on a second location located downstream of the beamline BL from the first location. The first and second locations are any one of the plurality of locations. For example, in the first operating mode described above, the ion beam is at least partially incident on the beam profile slit 23, and at least partially incident on the energy analysis slit 27 and the first Faraday cup 28 located downstream of the beam profile slit 23. Returning to Figure 16, the dose rate acquisition unit 104 acquires the measured values ​​of the neutron dose rate measured in a plurality of neutron radiation detectors 51-54 under a plurality of operating modes. The dose rate acquisition unit 104 can acquire the measured values ​​of the neutron dose rate measured in a plurality of neutron radiation detectors 51-54 under a plurality of operating modes. The dose rate acquisition unit 104 can acquire 24 measured values ​​measured in neutron radiation detectors 51-54 located at four measurement positions under six different operating modes. A plurality of neutron ray detectors 51-54 are respectively disposed at corresponding predetermined positions (or predetermined measurement positions). For example, the first neutron ray detector 51 is disposed at the first position (or the first measurement position), the second neutron ray detector 52 is disposed at the second position (or the second measurement position), the third neutron ray detector 53 is disposed at the third position (or the third measurement position), and the fourth neutron ray detector 54 is disposed at the fourth position (or the fourth measurement position). The measuring positions of the plurality of neutron ray detectors 51-54 are located outside the device body 58 and inside the housing 60. The device body 58 has a vacuum container surrounding the beamline BL, and the plurality of neutron ray detectors 51-54 are disposed outside the vacuum container. At least one of the plurality of neutron ray detectors 51-54 is located inside the arc-shaped curved portion of the beamline BL. The arc-shaped curved portion of the beamline BL is, for example, a beam deflection unit 16. For example, the first neutron ray detector 51 and the second neutron ray detector 52 are disposed inside the curved portion formed by the beam deflection unit 16. In one embodiment, the dose rate acquisition unit 104 can acquire a first measurement value measured at a predetermined position (e.g., the first neutron radiation detector 51) in a first operating mode and a second measurement value measured at the predetermined position (e.g., the first neutron radiation detector 51) in a second operating mode. In another embodiment, the dose rate acquisition unit 104 can acquire a first measurement value measured at a first position (e.g., the first neutron radiation detector 51) in a first operating mode and a second measurement value measured at a second position (e.g., the second neutron radiation detector 52) in a first operating mode. In one embodiment, the dose rate acquisition unit 104 can acquire a first measurement value measured at a first position (e.g., the first neutron ray detector 51) in the first operating mode, a second measurement value measured at a second position (e.g., the second neutron ray detector 52) in the first operating mode, a third measurement value measured at a first position (e.g., the first neutron ray detector 51) in the second operating mode, and a fourth measurement value measured at a second position (e.g., the second neutron ray detector 52) in the second operating mode. The dose rate recording unit 106 records the measured neutron dose rate obtained by the dose rate acquisition unit 104, establishing a correspondence between the ion beam firing conditions, the operating mode of the device body 58, the measurement position, and the measurement time during the measurement. Here, the ion beam firing conditions include the ion type, energy, and beam current of the ion beam. The firing conditions may further include transport parameters for controlling at least one of the ion beam's center trajectory, beam size, and beam shape. Transport parameters can also be referred to as operating parameters for controlling the operation of various machines in the device body 58 used to transport an ion beam that meets predetermined firing conditions. The dose rate recording unit 106 records the acquired neutron dose rate measured value as time-series data, and can perform post-hoc analysis of the temporal variation (i.e., trend) of the neutron dose rate based on the time-series data. The dose rate recording unit 106 can record the neutron dose rate measurement only when a high-energy ion beam capable of generating neutron rays is being delivered. For example, the dose rate recording unit 106 can record the neutron dose rate measurement only when the ion type is boron ions and the beam energy is within a predetermined energy range of 3.7 MeV or higher and 10 MeV or lower. In other words, the dose rate recording unit 106 can omit the neutron dose rate measurement when the ion type is other than boron and the beam energy is less than 3.7 MeV. The dose rate estimation unit 108 uses time-series data recorded by the dose rate recording unit 106 on the recording device 50c to estimate the neutron dose rate. Figure 19 is a schematic graph illustrating the neutron dose rate estimation method. Figure 19 schematically shows the time-series data of the neutron dose rate recorded on the recording device 50c. The time-series data includes multiple measured values ​​132 of the neutron dose rate measured at different times in the past. The dose rate estimation unit 108 arranges the multiple measured values ​​132 in chronological order and determines a function 134 representing the trend of the multiple measured values ​​132. In the example shown in Figure 19, the function 134 is an approximate straight line of the multiple measured values ​​132, but the function 134 is not limited to a straight line; it can be a polynomial of any degree (e.g., sixth degree), or an exponential or logarithmic function. The function 134 can be a moving average of the multiple measured values ​​132. The dose rate estimation unit 108 uses the intersection point 136 of the determined function 134 and the current time as the estimated value of the current neutron dose rate. The time-series data on the changing neutron dose rate over time correspond to the changes in the accumulation state of a specific element (e.g., boron) that undergoes nuclear reactions at the site that becomes a neutron radiation source. The dose rate estimation unit 108 estimates the neutron dose rate corresponding to the combination of the operating mode, ion beam conditions, and measurement position of the ion implantation device 100. The neutron dose rate varies depending on the accumulation state of a specific element (e.g., boron), the operating mode, the beam conditions, and the measurement position; therefore, the dose rate estimation unit 108 considers these estimated neutron dose rates. For example, the dose rate estimation unit 108 uses a plurality of measurement values ​​that are consistent with the combination of operating mode, beam conditions, and measurement position recorded in the timing data of the recording device 50c to calculate the estimated value of the current neutron dose rate. For example, the estimated neutron dose rate at the first position (e.g., the first neutron beam detector 51) when assuming a high-energy ion beam carrying boron ions is delivered in the first operating mode is estimated using a plurality of measurement values ​​previously measured at the first position (e.g., the first neutron beam detector 51) when a high-energy ion beam carrying boron ions is delivered in the first operating mode. The dose rate estimation unit 108 can calculate the estimated neutron dose rate using only past measurements where the ion type, energy, and beam current are all identical under the beam conditions. Alternatively, the dose rate estimation unit 108 can use past measurements where some beam conditions are inconsistent to calculate the estimated neutron dose rate. It can also use past measurements where the ion type and energy are the same but the beam current is different to calculate the estimated neutron dose rate. In this case, the estimated neutron dose rate can be calculated using a value corrected for the difference in beam current. For example, the correlation between the neutron dose rate and the beam current can be calculated beforehand, and the estimated neutron dose rate can be estimated using a value corrected for the correlation. The dose rate estimation unit 108 can also use past measurements where the ion type and beam current are the same but the energy is different to calculate the estimated neutron dose rate. In this case, the estimated neutron dose rate can be calculated using a value corrected for the difference in energy. For example, the correlation between neutron dose rate and energy can be calculated in advance, and the neutron dose rate can be inferred using values ​​corrected for past measurements based on this correlation. The dose rate inference unit 108 can calculate an inferred neutron dose rate using past measurements that, while having the same ion species, differ in energy and beam current. In this case, the inferred neutron dose rate can be calculated using values ​​corrected for past measurements based on differences in energy and beam current. For example, the correlation between neutron dose rate and energy and beam current can be calculated in advance, and the neutron dose rate can be inferred using values ​​corrected for this correlation. The comparison unit 110 compares the current measured value of the neutron dose rate acquired by the dose rate acquisition unit 104 with the predicted value of the neutron dose rate predicted by the dose rate prediction unit 108. The comparison unit 110 can determine whether the difference between the current measured value and the predicted value exceeds a predetermined threshold value, and output a warning if the predetermined threshold value is exceeded. The predetermined threshold value can be a fixed value that does not depend on the magnitude of the predicted value, or it can be a value obtained by multiplying the predicted value by a predetermined ratio. The predetermined threshold value can be determined based on the deviation of past measured values ​​used to calculate the predicted value, or it can be determined using a statistic (e.g., standard deviation) that represents the deviation of a plurality of measured values ​​132 relative to the function 134 shown in FIG. 19. The comparison unit 110 can compare a plurality of current measured values ​​of the neutron dose rate measured under a plurality of operating modes with a plurality of inferred values ​​of the neutron dose rate inferred under a plurality of operating modes. In one embodiment, the comparison unit 110 can compare a first measured value measured at a first position (e.g., neutron beam detector 51) under a first operating mode with a first inferred value inferred at the first position under the first operating mode, and compare a second measured value measured at a first position (e.g., neutron beam detector 51) under a second operating mode with a second inferred value inferred at the first position under the second operating mode. In this embodiment, the comparison unit 110 can output a warning if at least one of the difference between the first measured value and the first inferred value and the difference between the second measured value and the second inferred value exceeds a predetermined threshold. In this embodiment, the predetermined threshold can be set jointly for both the first inferred value and the second inferred value, or it can be set separately for each of the first inferred value and the second inferred value. The comparison unit 110 can compare a plurality of current measured values ​​of the neutron dose rate measured by a plurality of neutron radiation detectors 51-54 with a plurality of inferred values ​​of the neutron dose rate inferred at a plurality of measurement positions. In one embodiment, the comparison unit 110 can compare a first measured value measured at a first position (e.g., neutron radiation detector 51) in a first operating mode with a first inferred value inferred at the first position in the first operating mode, and compare a second measured value measured at a second position (e.g., second neutron radiation detector 52) in the first operating mode with a second inferred value inferred at the second position in the first operating mode. In this embodiment, the comparison unit 110 can output a warning if at least one of the difference between the first measured value and the first inferred value and the difference between the second measured value and the second inferred value exceeds a predetermined threshold value. In this embodiment, the predetermined threshold value can be set jointly for both the first inferred value and the second inferred value, or it can be set separately for each of the first inferred value and the second inferred value. The comparison unit 110 can compare a plurality of current measured values ​​of neutron dose rate measured by a plurality of neutron ray detectors 51-54 under a plurality of operating modes with a plurality of inferred values ​​of neutron dose rate inferred at a plurality of measurement positions under a plurality of operating modes. In one embodiment, the comparison unit 110 can compare a first measured value measured at a first position (e.g., neutron ray detector 51) under a first operating mode with a first inferred value inferred at the first position under the first operating mode; compare a second measured value measured at a second position (e.g., second neutron ray detector 52) under a first operating mode with a second inferred value inferred at the second position under the first operating mode; compare a third measured value measured at a first position (e.g., neutron ray detector 51) under a second operating mode with a third inferred value inferred at the first position under the second operating mode; and compare a fourth measured value measured at a second position (e.g., second neutron ray detector 52) under a second operating mode with a fourth inferred value inferred at the second position under the second operating mode. In this embodiment, the comparison unit 110 can compare 24 measured values ​​measured at 4 locations (e.g., neutron ray detectors 51-54) under 6 different operating modes with 24 inferred values ​​measured at 4 locations under 6 different operating modes. In this embodiment, the comparison unit 110 can output a warning if at least one of the differences between the corresponding measured values ​​and inferred values ​​exceeds a predetermined threshold. In this embodiment, the predetermined threshold can be set jointly for a plurality of inferred values ​​or set individually for each plurality of inferred values. The comparison unit 110 can determine the validity of the delivery parameters included in the beam conditions when the difference between the corresponding measured value and the inferred value exceeds a predetermined threshold. The comparison unit 110 can compare the current delivery parameters set in the device body 58 when measuring the neutron dose rate with the past delivery parameters corresponding to past measured values ​​recorded in the recording device 50c. The comparison unit 110 can output a warning when the difference between the current delivery parameters and the past delivery parameters exceeds a predetermined threshold. In this case, as a reason for the current measured value of the neutron dose rate becoming abnormal, it can be inferred that the following situation exists: due to the difference between the current and past delivery parameters, the ion beam has entered an unexpected location, thereby changing the amount of neutron radiation produced. The determination unit 112 may issue a warning if the current measured value of the neutron dose rate acquired by the dose rate acquisition unit 104 exceeds a predetermined reference value. The determination unit 112 may also issue a warning if the predicted value of the neutron dose rate predicted by the dose rate inference unit 108 exceeds a predetermined reference value. Here, the predetermined reference value is, for example, the upper limit for neutron dose rate management. When a warning is issued by the determination unit 112, maintenance may be performed, for example, to reduce the neutron dose rate, including replacing parts that could become neutron radiation sources, or cleaning parts outside the device, such as the plasma implantation device 100. Figure 20 is a flowchart illustrating an example of the method for monitoring neutron radiation according to an embodiment. Processor 50a records timing data establishing the correspondence between beam conditions and neutron dose rate in recording device 50c (S30). Processor 50a controls the operation of device body 58 to deliver a high-energy ion beam along beam line BL (S32). Processor 50a acquires the measured value of the neutron dose rate at a predetermined measurement position during the delivery of the high-energy ion beam (S34). Processor 50a uses the timing data recorded in recording device 50c and the beam conditions of the high-energy ion beam during the current delivery period to calculate an inferred value of the neutron dose rate at the predetermined measurement position (S36). Processor 50a compares the measured value with the inferred value (S38), and outputs a warning if the difference between the measured value and the inferred value exceeds a predetermined threshold (Yes in S40) (S42). If the difference between the measured value and the inferred value is below a predetermined threshold (not in S40), the processor 50a skips the processing in S42. Figure 21 is a flowchart illustrating another example of the process of monitoring neutron rays according to the embodiment. The processor 50a controls the operation of the device body 58 to deliver an ion beam along the beamline BL (S50). The ion beam delivered in S50 can be a high-energy ion beam or a low-energy ion beam that is not high-energy. The processor 50a acquires a measured value of the neutron dose rate at a predetermined measurement position during the delivery of the ion beam (S52). If past timing data is stored in the recording device 50c (yes in S54), the processor 50a uses the past timing data and the beam conditions of the ion beam during the current delivery period to calculate an inferred value of the neutron dose rate at the predetermined measurement position (S56). The processor 50a compares the measured value with the inferred value (S58), and outputs a warning if the difference between the measured value and the inferred value exceeds a predetermined threshold (yes in S60) (S62). If the difference between the measured value and the inferred value is below a predetermined threshold (no in S60), the processor 50a establishes a correspondence between the measured value of the neutron dose rate and the beam conditions of the ion beam during the current delivery period and records it in the recording device 50c (S64). If sufficient past time-series data to infer the neutron dose rate is not accumulated in the recording device 50c (no in S54), the processor 50a skips the processing of S56 to S60 and executes the processing of S64. Next, a method for reducing the dose rate of neutron rays generated in the ion implantation device 100 will be described. If a specific element (e.g., boron) that undergoes nuclear reactions accumulates at the site that becomes a neutron ray source when the ion implantation device 100 is used, the neutron dose rate increases when a high-energy ion beam is injected into that site. In particular, the neutron dose rate increases due to an increase in the amount of the specific element present near the surface of the site that becomes a neutron ray source. Therefore, if the amount of the specific element present near the surface of the site that becomes a neutron ray source can be reduced, the neutron dose rate when a high-energy ion beam is injected into that site can be reduced. As a method to reduce the amount of a specific element present near the surface of a site that becomes a neutron beam source, one could consider replacing the parts constituting that site or removing the parts and cleaning them outside the device. However, when maintenance of the ion implantation device 100 is performed to replace parts or clean parts outside the device, the operation of the ion implantation device 100 must be stopped for a certain period of time, resulting in a decrease in the productivity of the ion implantation device 100. Therefore, in this embodiment, a cleaning method to reduce the amount of a specific element present near the surface of a site that becomes a neutron beam source is performed, which is different from replacing parts and cleaning parts outside the device. Specifically, the amount of a specific element present near the surface of a site that becomes a neutron beam source is reduced by irradiating the site that becomes a neutron beam source with an ion beam containing ions of an element different from the specific element. By irradiating the site with an ion beam containing ions of an element different from the specific element, the specific element near the surface of the site that becomes the irradiation target can be removed by sputtering, or the surface of the site that becomes the irradiation target can be coated with an element different from the specific element. The ion beam used for cleaning includes ions of elements with an atomic number or mass number greater than that of a specific element. In the case of boron as the specific element, the ion types used in the cleaning ion beam include, for example, phosphorus (P), arsenic (As), argon (Ar), fluorine (F), xenon (Xe), carbon monoxide (CO), or carbon dioxide (CO₂). 2) Ions. Ion beams for cleaning can be used exclusively for cleaning or as part of ion implantation into wafers. In other words, the ion beam for cleaning may or may not irradiate the wafer. The ion beam for cleaning can sequentially irradiate at least one plurality of wafers contained in a batch. The cleaning ion beam is delivered in such a way that it is injected into at least one of a plurality of sites that become neutron sources. The cleaning ion beam can be delivered in at least one of the aforementioned plurality of operating modes, or in at least two of the plurality of operating modes, or in all of the plurality of operating modes. By delivering the cleaning ion beam in at least one of the plurality of operating modes, at least one of the plurality of sites that become neutron sources can be cleaned when a high-energy ion beam is delivered in at least one of the plurality of operating modes. For example, by delivering the cleaning ion beam in a first operating mode, at least one of the plurality of sites that become neutron sources can be cleaned when a high-energy ion beam is delivered in the first operating mode. The cleaning ion beam can be delivered in a predetermined cleaning mode. In this cleaning mode, the cleaning ion beam is delivered to change the position or range of at least partial penetration of the ion beam into the area to be cleaned. By changing at least one of the delivery state of the cleaning ion beam or changing the position of the area to be cleaned in the cleaning mode, the position or range of at least partial penetration of the ion beam into the area to be cleaned can be changed. This improves the cleaning efficiency of the area to be cleaned. In cleaning mode, the delivery parameters (e.g., at least one of the center track, beam size, and beam shape) of the cleaning ion beam can be changed while maintaining a fixed position on the area to be cleaned. For example, by using a deflector to reciprocate the center track of the ion beam in a predetermined direction, the position where the cleaning ion beam enters the area to be cleaned can be moved back and forth in the predetermined direction. Furthermore, by using a quadrupole convergence / divergence device (Q-lens) or the like to enlarge or reduce the beam size or change the beam shape, the range of the cleaning ion beam entering the area to be cleaned can be changed. In cleaning mode, the position of the area to be cleaned can be changed by a drive device while maintaining a fixed central trajectory, beam size, and beam shape of the ion beam. For example, by reciprocatingly scanning the area to be cleaned in a predetermined direction, the position where the ion beam enters the area to be cleaned can be moved back and forth in the predetermined direction. In cleaning mode, changes in at least one of the ion beam's central trajectory, beam size, and beam shape, along with changes in the position of the area to be cleaned, can be combined. The ion implantation device 100 can have multiple cleaning modes corresponding to multiple operating modes. The operating mode control unit 102 can operate the device body 58 according to the cleaning mode. Here, the cleaning mode corresponding to the predetermined operating mode refers to the cleaning mode used to clean the part that becomes a neutron generation source under the predetermined operating mode. The cleaning mode corresponding to the predetermined operating mode may differ from the predetermined operating mode in at least one aspect, including intentionally changing the delivery state of the cleaning ion beam and intentionally changing the position of the part that becomes the cleaning target, but be the same as the predetermined operating mode in other aspects. For example, in the first cleaning mode corresponding to the first operating mode of FIG9, the cleaning ion beam is injected into the beam profile slit 23, the energy analysis slit 27 and the first Faraday cup 28 for cleaning. The first cleaning mode and the first operating mode may differ in at least one aspect: intentionally changing the delivery state of the cleaning ion beam and intentionally changing the positions of the beam profile slit 23, the energy analysis slit 27, and the first Faraday cup 28. When the current measured value of the neutron dose rate obtained by the dose rate acquisition unit 104 exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. When the predicted value of the neutron dose rate predicted by the dose rate inference unit 108 exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. Therefore, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source when at least one of the measured value and the predicted value of the neutron dose rate exceeds a predetermined threshold. Here, the predetermined threshold can be the same as the aforementioned upper limit value for neutron dose rate management, i.e., the reference value, or it can be a value lower than the reference value. The predetermined threshold can, for example, be 10% to 90% of the reference value, or it can be 25%, 50%, or 75% of the reference value. The predetermined threshold can be changed according to the usage time of the ion implantation device 100 since the last maintenance, or the reference value can be increased as the usage time increases. If at least one of the plurality of measured values ​​of the neutron dose rate at a plurality of measurement locations exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. If at least one of the plurality of inferred values ​​of the neutron dose rate at a plurality of measurement locations exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. When at least one of the plurality of measured values ​​of the neutron dose rate measured in a plurality of operating modes exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. When at least one of the plurality of inferred values ​​of the neutron dose rate inferred in a plurality of operating modes exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. In this case, the cleaning ion beam can be delivered in an operating mode where the measured or inferred value exceeds the predetermined threshold, or in a cleaning mode corresponding to the operating mode where the measured or inferred value exceeds the predetermined threshold. When at least one of a plurality of measured values ​​of the neutron dose rate corresponding to a combination of a plurality of operating modes and a plurality of measurement locations exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. When at least one of a plurality of inferred values ​​of the neutron dose rate corresponding to a combination of a plurality of operating modes and a plurality of measurement locations exceeds a predetermined threshold, the ion implantation device 100 can deliver a cleaning ion beam to perform cleaning of the site that becomes a neutron generation source. In this case, the cleaning ion beam can be delivered in an operating mode where the measured or inferred value exceeds the predetermined threshold, or in a cleaning mode corresponding to an operating mode where the measured or inferred value exceeds the predetermined threshold. The ion implantation device 100 can deliver a high-energy ion beam after delivering a cleaning ion beam to obtain a measurement value of the neutron dose rate after cleaning. If the measured value after cleaning exceeds a predetermined threshold, the ion implantation device 100 can perform a second cleaning. That is, a second cleaning can be performed after the first cleaning. The beam conditions of the ion beam used for the second cleaning can be the same as or different from those of the ion beam used for the first cleaning. For example, if arsenic ions were used in the first cleaning, arsenic ions can also be used in the second cleaning, or phosphorus ions, argon ions, or fluorine ions, which are different from arsenic ions, can be used. Furthermore, in the second cleaning, the beam current can be increased compared to the first cleaning, or the energy can be decreased compared to the first cleaning. When the ion implantation device 100 delivers a cleaning ion beam or performs ion implantation using a high-energy ion beam, provided that the neutron dose rate measurements corresponding to a plurality of combinations of operating modes and measurement positions do not exceed a predetermined threshold, the ion implantation device 100 can also deliver a cleaning ion beam or perform ion implantation using a high-energy ion beam. In this case, the high-energy ion beam can irradiate at least one wafer or sequentially irradiate at least one plurality of wafers contained in a batch. Regarding the dose rate of neutron rays generated by the boron-boron (BB) reaction involving collisions of boron ions, it is known that after accumulating boron near the surface of a site capable of becoming a neutron ray source by delivering a low-energy boron ion beam, the dose rate tends to increase when delivering a high-energy boron ion beam. Here, an example of low energy is 0.1 MeV or higher but less than 3.7 MeV, and an example of high energy is 3.7 MeV or higher but less than 10 MeV. When irradiated with a high-energy boron ion beam, boron accumulates at a relatively deep position away from the surface where boron ions are injected. On the other hand, when irradiated with a low-energy boron ion beam, boron accumulates at a shallow position near the surface where boron ions are injected. The BB reaction occurs at a predetermined energy threshold (e.g., 3.7 MeV) or higher, and therefore occurs only near the surface where high-energy boron ions are injected. High-energy boron ions slow down as they travel from the surface of the injection site along the depth direction. At a depth deep from the surface of the injection site, the energy level becomes lower than the critical value for reaction. Therefore, the boron accumulated at a depth deep from the surface does not contribute to the generation of neutron rays. Therefore, when a high-energy boron ion beam is to be delivered after a low-energy boron ion beam, it is preferable to reduce the amount of boron near the surface of the site that could become a neutron radiation source by delivering a cleaning ion beam. That is, it is preferable to deliver a cleaning ion beam after a low-energy boron ion beam and before a high-energy boron ion beam. Furthermore, the neutron dose rate when delivering a high-energy boron ion beam after a low-energy boron ion beam can be measured or estimated, and it can be determined whether at least one of the measured value and the estimated value exceeds a predetermined threshold, thus determining whether it is necessary to deliver a cleaning ion beam. When a high-energy boron ion beam is to be delivered after a low-energy boron ion beam, if the estimated value of the neutron dose rate before delivering the high-energy boron ion beam exceeds a predetermined threshold, a cleaning ion beam can be delivered. In the ion implantation apparatus 100, in order to suppress the accumulation of a specific element (e.g., boron) near the surface of a site that could become a neutron beam source, the ion implantation apparatus 100 can be used while switching the type of ions used for the implantation process. For example, if only the implantation process using a low-energy boron ion beam is repeatedly performed, the accumulation of boron near the surface of the site that could become a neutron beam source can be promoted. Subsequently, if the implantation process using a high-energy boron ion beam is performed, the neutron dose rate tends to increase. At this time, by performing the implantation process using an ion beam of an element different from the specific element (e.g., boron) (e.g., arsenic) after the implantation process using a low-energy boron ion beam, the accumulation of boron near the surface of the site that could become a neutron beam source can be suppressed, and the increase in neutron dose rate when performing the implantation process using a high-energy boron ion beam can be suppressed. Processor 50a can acquire a plurality of implantation conditions corresponding to a plurality of batches and use the acquired plurality of implantation conditions to determine the processing order of the plurality of batches. For example, processor 50a can acquire implantation instructions including a plurality of implantation conditions from an external management device used to manage the operation of the ion implantation device 100, and determine the processing order of the plurality of batches based on the acquired implantation instructions. Processor 50a can determine the processing order of the plurality of batches in a manner that suppresses the accumulation of boron near the surface of a site that could become a neutron ray generation source. Processor 50a can perform an implantation process that implants ions into a plurality of wafers contained in each of the plurality of batches according to the determined processing order and the corresponding implantation conditions. For example, if the acquired plurality of implantation conditions include a first implantation condition for implanting high-energy boron ions and a second implantation condition for implanting a different type of ion (e.g., arsenic ions), the processing order can be determined by implanting a different type of ion (e.g., arsenic ions) into a plurality of wafers contained in the batch of the second implantation condition, and then implanting high-energy boron ions into a plurality of wafers contained in the batch of the first implantation condition. Furthermore, when the acquired implantation conditions include a first implantation condition for implanting high-energy boron ions, a second implantation condition for implanting a different type of ion (e.g., arsenic ions), and a third implantation condition for implanting low-energy boron ions, the processing order can be determined by not immediately performing the implantation process based on the first implantation condition after the implantation process based on the third implantation condition. For example, if the measured or inferred value of the neutron dose rate before the start of the implantation process based on the multiple implantation conditions is below a predetermined critical value, the implantation process based on the first implantation condition can be performed first, followed by the implantation processes based on the second and third implantation conditions. In this case, by performing the implantation process based on the second implantation condition after the implantation process based on the third implantation condition, the accumulation of boron near the surface caused by the implantation process based on the third implantation condition can be reduced by utilizing the implantation process based on the second implantation condition. If the measured or inferred value of the neutron dose rate before the commencement of implantation treatment based on multiple implantation conditions exceeds a predetermined threshold, the implantation treatment can be performed in the order of the second implantation condition, the first implantation condition, and the third implantation condition. Alternatively, the implantation treatment can be performed in the order of the third implantation condition, the second implantation condition, and the first implantation condition. Figure 22 is a flowchart illustrating an example of the ion implantation method according to an embodiment. The processor 50a controls the operation of the device body 58, delivering a first ion beam containing a high-energy first ion type along the beamline BL (S70). Here, an example of high energy is 3.7 MeV or higher and 10 MeV or lower, and an example of the first ion type is boron ions. The processor 50a acquires a measured value of the neutron dose rate at a predetermined position during the delivery of the first ion beam (S72). If the measured value exceeds a predetermined threshold (Yes in S74), the processor 50a controls the operation of the device body 58 to stop the delivery of the first ion beam and delivers a second ion beam containing a second ion type with a mass number greater than that of the first ion type along the beamline BL (S76). Here, an example of the second ion type is arsenic ions, and the second ion beam is the aforementioned cleaning ion beam. After delivering the second ion beam, the processor 50a delivers the first ion beam along the beamline and irradiates the wafer, performing ion implantation processing using the first ion beam (S78). If the measured value is below the predetermined threshold (not in S74), then processor 50a skips S76 and executes the process of S78. Figure 23 is a flowchart illustrating another example of the ion implantation method of the embodiment. The method shown in Figure 23 differs from the method shown in Figure 22 in that it uses an inferred value instead of a measured value to determine whether a second ion beam for cleaning needs to be delivered. Processor 50a acquires an implantation command (S80) using a first ion beam comprising a first ion type with high energy. The implantation command is sent, for example, from an external management device used to manage the operation of ion implantation device 100 to ion implantation device 100. Processor 50a calculates an inferred value of the neutron dose rate at a predetermined position assuming the first ion beam is delivered along the beam line BL (S82). Processor 50a calculates the inferred value of the neutron dose rate, for example, using timing data recorded in recording device 50c and the beam conditions of the first ion beam. If the inferred value exceeds a predetermined threshold (Yes in S84), processor 50a controls the operation of device body 58 to deliver a second ion beam comprising a second ion type with a mass number greater than that of the first ion type along the beam line BL (S86). After delivering the second ion beam, processor 50a delivers the first ion beam along the beam line BL and irradiates the wafer, performing ion implantation processing using the first ion beam (S88). If the inferred value is below a predetermined threshold (not in S84), processor 50a skips S86 and executes the processing in S88. In the above embodiments, a method for calculating the inferred value of the neutron dose rate using time-series data of neutron dose rate measurements has been described. In another embodiment, the inferred value of the neutron dose rate can be calculated using time-series data representing the accumulation state of a specific element (e.g., boron) at a site capable of becoming a neutron source. For example, the accumulation state of a specific element (e.g., boron) at a site capable of becoming a neutron source can be calculated based on the delivery performance of the ion beam on the beamline BL. Furthermore, the neutron dose rate at a predetermined location can be inferred using the beam conditions of the high-energy ion beam incident on the site where the specific element is accumulated and the calculated accumulation state of the specific element. The calculation of the accumulation state of the specific element and the inference of the neutron dose rate can utilize the techniques described in Japanese Patent Nos. 6785188 and 6785189 (US Patent Nos. 10,354,835 and 10,490,389), all of which are incorporated herein by reference. One embodiment of this method is as follows. (Item 3-1) A method comprising the steps of: recording time-series data that establishes a correspondence between beam conditions, including the ion type, energy, and beam current of an ion beam delivered along a beamline within an ion implantation device, and a neutron dose rate measured at a predetermined measurement location within the ion implantation device, in a recording device; delivering a high-energy ion beam along the aforementioned beamline; obtaining a measured value of the neutron dose rate measured at the aforementioned predetermined measurement location while delivering the aforementioned high-energy ion beam; using the aforementioned time-series data and the aforementioned beam conditions of the aforementioned high-energy ion beam, calculating an inferred value of the inferred neutron dose rate at the aforementioned predetermined measurement location while delivering the aforementioned high-energy ion beam; and comparing the measured value with the inferred value. (Item 3-2) The method of Item 3-1, wherein the aforementioned ion implantation device has a plurality of operating modes for at least partially inserting an ion beam delivered along the aforementioned beamline into at least one of a plurality of sites within the aforementioned ion implantation device, the aforementioned measurement value is measured when the aforementioned high-energy ion beam is delivered in at least one of the aforementioned operating modes, and the aforementioned inferred value is calculated using the neutron dose rate measured in the aforementioned time series data when the aforementioned ion beam is delivered in at least one of the aforementioned operating modes. (Item 3-3) The method of Item 3-2, wherein the aforementioned ion implantation device has a driving device that changes the position of at least one of the aforementioned sites, at least one of the aforementioned operating modes is used to position at least one of the aforementioned sites on the aforementioned beamline using the aforementioned driving device, thereby at least partially blocking the aforementioned ion beam by means of at least one of the aforementioned sites. (Item 3-4) The method of Item 3-2, wherein the aforementioned ion implantation device includes a deflection device that applies at least one of an electric field and a magnetic field to deflect the trajectory of the aforementioned ion beam, and at least one of the aforementioned plurality of operating modes uses the aforementioned deflection device to direct the aforementioned ion beam into at least one of the aforementioned plurality of locations located away from the aforementioned beam line. (Item 3-5) The method of any one of Items 3-2 to 3-4, wherein the aforementioned plurality of locations includes a first location and a second location located downstream of the aforementioned beam line from the first location, and at least one of the aforementioned plurality of operating modes directs the aforementioned ion beam into at least partially the first location and into the second location.(Item 3-6) The method as described in any one of items 3-2 to 3-4, wherein the plurality of locations includes a first location and a second location located downstream of the aforementioned beam line from the first location; the plurality of operating modes include: a first operating mode in which the aforementioned ion beam is at least partially incident on the aforementioned first location; and a second operating mode in which the aforementioned ion beam is at least partially incident on the aforementioned second location; the aforementioned measured values ​​include: a first measured value of neutron dose rate, measured at the aforementioned predetermined measurement position when the aforementioned high-energy ion beam is delivered in the aforementioned first operating mode; and a second measured value of neutron dose rate, measured at the aforementioned predetermined measurement position when the aforementioned high-energy ion beam is delivered in the aforementioned second operating mode; the aforementioned inferred values ​​include: a first inferred value, calculated using the neutron dose rate measured in the aforementioned time series data when the aforementioned ion beam is delivered in the aforementioned first operating mode; and a second inferred value, calculated using the neutron dose rate measured in the aforementioned time series data when the aforementioned ion beam is delivered in the aforementioned second operating mode. The aforementioned comparison includes the following steps: comparing the aforementioned first measured value with the aforementioned first inferred value; and comparing the aforementioned second measured value with the aforementioned second inferred value.(Item 3-7) The method as described in any one of items 3-2 to 3-4, wherein the aforementioned plurality of locations includes a first location and a second location located downstream of the aforementioned beam line from the first location; the aforementioned predetermined measurement position includes a first measurement position and a second measurement position; and the aforementioned plurality of operating modes include: a first operating mode in which the aforementioned ion beam is at least partially incident on the aforementioned first location; and a second operating mode in which the aforementioned ion beam is at least partially incident on the aforementioned second location. The aforementioned measured values ​​include: a first measured value of neutron dose rate, measured at the first measured position when the aforementioned high-energy ion beam is delivered in the aforementioned first operating mode; a second measured value of neutron dose rate, measured at the aforementioned first measured position when the aforementioned high-energy ion beam is delivered in the aforementioned second operating mode; a third measured value of neutron dose rate, measured at the aforementioned second measured position when the aforementioned high-energy ion beam is delivered in the aforementioned first operating mode; and a fourth measured value of neutron dose rate, measured at the aforementioned second measured position when the aforementioned high-energy ion beam is delivered in the aforementioned second operating mode. The aforementioned inferred values ​​include: a first inferred value, calculated using the neutron dose rate measured at the first measurement position when the aforementioned ion beam is delivered in the aforementioned first operating mode, as shown in the aforementioned time series data; a second inferred value, calculated using the neutron dose rate measured at the first measurement position when the aforementioned ion beam is delivered in the aforementioned second operating mode, as shown in the aforementioned time series data; a third inferred value, calculated using the neutron dose rate measured at the second measurement position when the aforementioned ion beam is delivered in the aforementioned first operating mode, as shown in the aforementioned time series data; and a fourth inferred value, calculated using the neutron dose rate measured at the second measurement position when the aforementioned ion beam is delivered in the aforementioned second operating mode, as shown in the aforementioned time series data. The aforementioned comparison includes the following steps: comparing the aforementioned first measurement value with the aforementioned first inferred value; comparing the aforementioned second measurement value with the aforementioned second inferred value; comparing the aforementioned third measurement value with the aforementioned third inferred value; and comparing the aforementioned fourth measurement value with the aforementioned fourth inferred value. (Item 3-8) The method as described in any one of items 3-1 to 3-5, wherein the predetermined measurement location includes a first measurement location and a second measurement location, the measured value includes: a first measurement value of neutron dose rate, measured at the first measurement location during the delivery of the high-energy ion beam; and a second measurement value of neutron dose rate, measured at the second measurement location during the delivery of the high-energy ion beam; the inferred value includes: a first inferred value, calculated using the neutron dose rate measured at the first measurement location in the aforementioned time series data; and a second inferred value, calculated using the neutron dose rate measured at the second measurement location in the aforementioned time series data, the comparison includes the steps of: comparing the first measurement value with the first inferred value; and comparing the second measurement value with the second inferred value.(Item 3-9) The method as described in any one of items 3-1 to 3-8, wherein the ion type of the aforementioned high-energy ion beam is boron ions, and the energy of the aforementioned high-energy ion beam is 3.7 MeV or higher and 10 MeV or lower. (Item 3-10) The method as described in any one of items 3-1 to 3-9, wherein the aforementioned inferred value is calculated using the neutron dose rate corresponding to the beam conditions in the aforementioned time series data, and the aforementioned beam conditions are the same ion type as the aforementioned high-energy ion beam and are high energy within a predetermined energy range. (Item 3-11) The method as described in item 3-10, wherein the aforementioned predetermined energy range is 3.7 MeV or higher and 10 MeV or lower. (Item 3-12) The method as described in item 3-10 or item 3-11, wherein the aforementioned inferred value is calculated using the neutron dose rate corresponding to the beam conditions in the aforementioned time series data, and the aforementioned beam conditions are the same energy as the aforementioned high-energy ion beam. (Item 3-13) The method of any one of items 3-10 to 3-12, wherein the aforementioned inferred value is calculated using the neutron dose rate corresponding to the beam conditions in the aforementioned time series data, wherein the aforementioned beam conditions are the same beam current as the aforementioned high-energy ion beam. (Item 3-14) The method of any one of items 3-1 to 3-13, wherein the aforementioned comparison includes the step of determining whether the difference between the aforementioned measured value and the aforementioned inferred value exceeds a predetermined threshold value. (Item 3-15) The method of item 3-14, further including the step of outputting a warning if the difference between the aforementioned measured value and the aforementioned inferred value exceeds the aforementioned predetermined threshold value. (Item 3-16) The method as described in Item 3-14 or Item 3-15, wherein the aforementioned beam conditions further include a transport parameter for controlling at least one of the central trajectory, beam size, and beam shape of the aforementioned ion beam transported along the aforementioned beam line, and the aforementioned method further includes the step of: comparing the transport parameters of the aforementioned high-energy ion beam with the transport parameters contained in the aforementioned time series data when the difference between the aforementioned measured value and the aforementioned inferred value exceeds the aforementioned predetermined threshold value. (Item 3-17) The method as described in any one of Items 3-1 to 3-16, wherein the aforementioned ion implantation device comprises: a vacuum container surrounding the aforementioned beam line; and a housing disposed outside the aforementioned vacuum container, wherein the aforementioned predetermined measurement position is outside the aforementioned vacuum container and inside the aforementioned housing. (Item 3-18) The method as described in any one of Items 3-1 to 3-17, wherein the aforementioned beam line includes a curved portion extending in an arc shape, and the aforementioned predetermined measurement position is located inside the aforementioned curved portion.(Item 3-19) An ion implantation device comprising: an ion source for generating an ion beam; a beamline device configured to deliver the ion beam along the beamline, and including an accelerator for accelerating the ion beam and generating a high-energy ion beam; a neutron beam detector disposed at a predetermined measurement position for measuring a neutron dose rate; a memory storing a program; and a processor, wherein the processor performs the following steps according to the program: recording timing data that establishes a correspondence between beam conditions including the ion type, energy, and beam current of the ion beam delivered along the beamline and the neutron dose rate measured using the neutron beam detector in a recording device; delivering the high-energy ion beam along the beamline; acquiring a measured value of the neutron dose rate measured using the neutron beam detector while delivering the high-energy ion beam; calculating an inferred value of the neutron dose rate inferred at the predetermined measurement position while delivering the high-energy ion beam using the timing data and the beam conditions of the high-energy ion beam; and comparing the measured value with the inferred value. Another embodiment of this invention is as follows. (Item 4-1) An ion implantation method, comprising the following steps: obtaining at least one of a first measured value of neutron dose rate and a first inferred value of neutron dose rate, wherein the first measured value of neutron dose rate is measured at a predetermined position in the ion implantation device when a first ion beam including a high-energy first ion type is delivered along a beamline in the ion implantation device, and the first inferred value of neutron dose rate is inferred at the predetermined position assuming that the first ion beam is delivered along the beamline; determining whether at least one of the first measured value and the first inferred value exceeds a predetermined threshold; if at least one of the first measured value and the first inferred value exceeds the predetermined threshold, delivering a second ion beam including a second ion type with a mass number greater than the first ion type along the beamline; and after delivering the second ion beam, delivering the first ion beam along the beamline and irradiating a wafer. (Item 4-2) The ion implantation method as described in Item 4-1, wherein the aforementioned first measured value includes a plurality of first measured values ​​of neutron dose rate measured at a plurality of predetermined locations within the aforementioned ion implantation device, the aforementioned first inferred value includes a plurality of first inferred values ​​of neutron dose rate inferred at the aforementioned plurality of predetermined locations, and the aforementioned second ion beam is delivered along the aforementioned beamline when at least one of the aforementioned plurality of first measured values ​​and the aforementioned plurality of first inferred values ​​exceeds the aforementioned predetermined threshold value. (Item 4-3) The ion implantation method as described in Item 4-1, wherein the aforementioned ion implantation device has a plurality of operating modes for at least partially injecting an ion beam delivered along the aforementioned beamline into at least one of a plurality of sites within the aforementioned ion implantation device, the aforementioned first measurement value includes a plurality of first measurement values ​​corresponding to the aforementioned plurality of operating modes measured at the aforementioned predetermined position when the aforementioned first ion beam is delivered in the aforementioned plurality of operating modes, the aforementioned first inference value includes a plurality of first inference values ​​corresponding to the aforementioned plurality of operating modes inferred at the aforementioned predetermined position assuming that the aforementioned first ion beam is delivered in the aforementioned plurality of operating modes, and if at least one of the aforementioned plurality of first measurement values ​​and the aforementioned plurality of first inference values ​​exceeds the aforementioned predetermined threshold value, the aforementioned second ion beam is delivered along the aforementioned beamline.(Item 4-4) The ion implantation method as described in Item 4-1, wherein the aforementioned ion implantation device has a plurality of operating modes for at least partially injecting an ion beam delivered along the aforementioned beamline into at least one of a plurality of sites within the aforementioned ion implantation device, the aforementioned first measurement value includes a plurality of first measurement values ​​measured at a plurality of predetermined positions within the aforementioned ion implantation device when the aforementioned first ion beam is delivered in the aforementioned plurality of operating modes, corresponding to a combination of the aforementioned plurality of operating modes and the aforementioned plurality of predetermined positions, the aforementioned first inference value includes a plurality of first inference values ​​inferred at the aforementioned plurality of predetermined positions assuming that the aforementioned first ion beam is delivered in the aforementioned plurality of operating modes, corresponding to a combination of the aforementioned plurality of operating modes and the aforementioned plurality of predetermined positions, and if at least one of the aforementioned plurality of first measurement values ​​and the aforementioned plurality of first inference values ​​exceeds the aforementioned predetermined threshold value, the aforementioned second ion beam is delivered along the aforementioned beamline. (Item 4-5) An ion implantation method as described in Item 4-3 or Item 4-4, wherein the plurality of sites includes a first site and a second site located downstream of the beam line from the first site, and the plurality of operating modes include: a first operating mode in which the ion beam is at least partially inserted into the first site; and a second operating mode in which the ion beam is at least partially inserted into the second site. (Item 4-6) An ion implantation method as described in any one of Items 4-3 to 4-5, wherein the ion implantation device includes a driving device for changing the position of at least one of the plurality of sites, and at least one of the plurality of operating modes uses the driving device to position at least one of the plurality of sites on the beam line, thereby at least partially blocking the ion beam by means of at least one of the plurality of sites. (Item 4-7) An ion implantation method as described in any one of items 4-3 to 4-6, wherein the ion implantation device includes a deflection device that applies at least one of an electric field and a magnetic field to deflect the trajectory of the ion beam, and at least one of the plurality of operating modes uses the deflection device to direct the ion beam to at least one of the plurality of sites before the beam line is set. (Item 4-8) An ion implantation method as described in any one of items 4-3 to 4-7, wherein the determination includes the steps of: determining at least one operating mode corresponding to at least one first measured value or first inferred value exceeding the predetermined threshold value, and delivering the second ion beam includes the step of: delivering the second ion beam in the determined at least one operating mode.(Item 4-9) An ion implantation method as described in any one of items 4-3 to 4-7, wherein the ion implantation device comprises a plurality of cleaning modes, the plurality of cleaning modes changing the position or range of at least partial penetration of the ion beam in at least one of the plurality of sites, and delivering the second ion beam comprises the step of delivering the second ion beam in at least one of the plurality of cleaning modes. (Item 4-10) An ion implantation method as described in item 4-9, wherein the plurality of sites includes a first site and a second site located downstream of the beam line from the first site, the plurality of cleaning modes comprising: a first cleaning mode changing the position or range of at least partial penetration of the ion beam in the first site; and a second cleaning mode changing the position or range of at least partial penetration of the ion beam in the second site. (Item 4-11) An ion implantation method as described in Item 4-9 or Item 4-10, wherein at least one of the aforementioned plurality of cleaning modes includes changing a delivery parameter used to control at least one of the central trajectory, beam size, and beam shape of the aforementioned ion beam. (Item 4-12) An ion implantation method as described in any one of Items 4-9 to 4-11, wherein at least one of the aforementioned plurality of cleaning modes includes changing the position of at least one of the aforementioned plurality of sites. (Item 4-13) An ion implantation method as described in any one of Items 4-9 to 4-12, wherein delivering the aforementioned second ion beam includes the step of delivering the aforementioned second ion beam in at least two of the aforementioned plurality of cleaning modes. (Item 4-14) An ion implantation method as described in any one of Items 4-1 to 4-13, wherein delivering the aforementioned second ion beam does not include the step of irradiating the wafer with the aforementioned second ion beam. (Item 4-15) An ion implantation method as described in any one of items 4-1 to 4-13, wherein delivering the aforementioned second ion beam comprises the step of irradiating the aforementioned second ion beam onto a wafer. (Item 4-16) An ion implantation method as described in any one of items 4-1 to 4-13, wherein delivering the aforementioned second ion beam comprises the step of irradiating the aforementioned second ion beam onto at least one plurality of wafers contained in a batch. (Item 4-17) An ion implantation method as described in any one of items 4-1 to 4-16, wherein irradiating the aforementioned first ion beam onto a wafer comprises the step of irradiating the aforementioned first ion beam onto at least one plurality of wafers contained in a batch. (Item 4-18) An ion implantation method as described in any one of items 4-1 to 4-17, wherein the aforementioned first ion type is boron ions, and the aforementioned high energy is 3.7 MeV or higher and 10 MeV or lower. (Item 4-19) The ion implantation method as described in Item 4-18, wherein the aforementioned second ion type is a phosphorus, arsenic, argon or fluorine ion.(Item 4-20) An ion implantation method as described in any one of items 4-1 to 4-19, wherein if at least one of the aforementioned first measured value and the first inferred value does not exceed the aforementioned predetermined threshold value, the aforementioned second ion beam is not delivered before the aforementioned first ion beam is delivered and irradiated onto the wafer. (Item 4-21) The ion implantation method as described in any one of items 4-1 to 4-20 further includes the following steps: acquiring at least one of a second measured value of neutron dose rate and a second inferred value of neutron dose rate, wherein the second measured value of neutron dose rate is measured at the predetermined position after the delivery of the first ion beam along the aforementioned beamline following the delivery of the second ion beam, and the second inferred value of neutron dose rate is inferred at the predetermined position assuming that the first ion beam is delivered along the aforementioned beamline after the delivery of the second ion beam; determining whether at least one of the acquired second measured value and the second inferred value exceeds the aforementioned predetermined threshold; and if at least one of the acquired second measured value and the second inferred value exceeds the aforementioned predetermined threshold, delivering a third ion beam including a third ion species with a mass number greater than that of the first ion species along the aforementioned beamline before delivering the first ion beam. (Item 4-22) The ion implantation method as described in any one of items 4-1 to 4-21 further includes the step of delivering a fourth ion beam comprising a low-energy first ion type along the aforementioned beamline, wherein the acquisition of at least one of the aforementioned first measured value and the aforementioned first inferred value is performed under the following conditions: the aforementioned first ion beam is delivered after the delivery of the aforementioned fourth ion beam; or the aforementioned first ion beam is pre-delivered after the delivery of the aforementioned fourth ion beam. (Item 4-23) The ion implantation method as described in item 4-22, wherein the aforementioned low energy is 0.1 MeV or higher and less than 3.7 MeV.(Item 4-24) An ion implantation device comprising: a first gas supply source for supplying a source gas of a first ion type; a second gas supply source for supplying a source gas of a second ion type with a mass number greater than that of the first ion type; an ion source for generating an ion beam comprising the first ion type or the second ion type using the source gas supplied from the first gas supply source or the second gas supply source; a beamline device configured to deliver the ion beam along a beamline, including an accelerator for accelerating the ion beam; an implantation processing chamber for performing an implantation process in which the ion beam delivered by the beamline device is irradiated onto a wafer; and a memory storing a program and a processor, wherein the processor executes the following steps according to the program: The method involves acquiring at least one of a first measured value and a first inferred value of neutron dose rate, wherein the first measured value of neutron dose rate is measured at a predetermined position within the ion implantation device while delivering a first ion beam comprising a high-energy first ion type along a beamline within the ion implantation device, and the first inferred value of neutron dose rate is inferred at the predetermined position assuming that the first ion beam is delivered along the aforementioned beamline; determining whether at least one of the first measured value and the first inferred value exceeds a predetermined threshold; if at least one of the first measured value and the first inferred value exceeds the aforementioned predetermined threshold, delivering a second ion beam comprising a second ion type with a mass number greater than that of the first ion type along the aforementioned beamline; and after delivering the second ion beam, delivering the first ion beam along the aforementioned beamline and irradiating the wafer. (Item 4-25) An ion implantation method comprising the steps of: acquiring a plurality of implantation conditions corresponding to a plurality of batches; using the plurality of implantation conditions to determine the processing order of the plurality of batches; and implanting ions conforming to the corresponding implantation conditions into a plurality of wafers contained in each of the plurality of batches according to the determined processing order, wherein, in the case where the plurality of implantation conditions acquired include a first implantation condition for implanting a first type of high-energy ion and a second implantation condition for implanting a second type of ion with a mass number greater than that of the first type of ion, the processing order is determined as follows: after implanting the second type of ion into a plurality of wafers contained in the batch containing the second implantation condition, the high-energy first type of ion is implanted into a plurality of wafers contained in the batch containing the first implantation condition. The present disclosure has been described above with reference to the various embodiments described above. However, the present disclosure is not limited to the embodiments described above, and the structures of the embodiments can be appropriately combined or substituted. Furthermore, based on the knowledge of those skilled in the art, the combinations and processing order of the embodiments can be appropriately reorganized, and various design changes and modifications can be applied to the embodiments. Embodiments with such reorganizations and modifications can also be included within the scope of the method, ion implantation, and ion implantation device disclosed herein. This application claims priority based on Japanese Patent Application No. 2022-047385, filed on March 23, 2022. The entire contents of that Japanese application are incorporated herein by reference. 10: Ion source; 12: Beam generation unit; 14: Beam acceleration unit; 16: Beam deflection unit; 18: Beam delivery unit; 20: Substrate handling unit; 22a~22c: Linear acceleration device; 23: Beam profile slit; 24: Energy analysis electromagnet; 27: Energy analysis slit; 28: First Faraday cup; 31: Second Faraday cup; 34: Beam scanner; 35: Beam gather stack; 40: Implantation processing chamber; 42: Beam monitor; 50: Central control device; 50a: Processor; 50b: Memory; 50c: Recording device; 58: Device body; 60: Housing; 100: Ion implantation device. [Figure 1] Schematic diagram of the neutron scattering member disposed in the housing. [Figure 2] Schematic cross-sectional view of the structure of the housing. [Figure 3] Schematic diagram of the neutron scattering member disposed separately from the housing. [Figure 4] Top view of the schematic structure of the ion implantation device according to the embodiment. [Figure 5] Figures 5(a) to 5(c) are side views of the schematic structure of the ion implantation device of Figure 4. [Figure 6] Schematic top view of the structure of the front door of the loading port. [Figure 7] Figures 7(a) and 7(b) are schematic top views of the front door of the loading port in the open state. [Figure 8] Flowchart of the ion implantation steps according to the embodiment. [Figure 9] Schematic diagram of the ion implantation device in the first step. [Figure 10] Schematic diagram of the ion implantation device in the second step. [Figure 11] Schematic diagram of the ion implantation device in the third step. [Figure 12] Schematic diagram of the ion implantation device in the fourth step. [Figure 13] Schematic diagram of the ion implantation device in step 5. [Figure 14] Schematic diagram of the ion implantation device in step 6. [Figure 15] Schematic diagram of the structure of the central control device. [Figure 16] Schematic block diagram of the functional structure of the central control device. [Figure 17] Schematic diagram of a drive device that changes the position of at least a partially injected portion of the ion beam. [Figure 18] Schematic diagram of a deflection device that deflects the ion beam. [Figure 19] Schematic graph of a method for inferring neutron dose rate. [Figure 20] Flowchart of an example of the method for monitoring neutron rays according to the embodiment. [Figure 21] Flowchart of another example of the method for monitoring neutron rays according to the embodiment. [Figure 22] Flowchart of an example of the ion implantation method according to the embodiment. [Figure 23] Flowchart of another example of the ion implantation method according to the embodiment. 126: Deflection device 128: Location where the beam BL is set BL: Beamline IB: Ion Beam

Claims

1. A method for monitoring neutron radiation, comprising the steps of: recording time-series data in a recording device that establishes a correspondence between beam conditions, including the ion type, energy, and beam current of an ion beam delivered along a beamline within an ion implantation device, and a plurality of past measurements of neutron dose rate measured at a predetermined measurement location within the ion implantation device at a plurality of different times in the past; delivering a high-energy ion beam along the aforementioned beamline; acquiring a current measurement of the neutron dose rate measured at the predetermined measurement location while delivering the aforementioned high-energy ion beam; using the aforementioned time-series data and the aforementioned beam conditions of the aforementioned high-energy ion beam, calculating an inferred value of the neutron dose rate inferred at the aforementioned predetermined measurement location while currently delivering the aforementioned high-energy ion beam; and comparing the aforementioned current measurement value with the aforementioned inferred value.

2. The method for monitoring neutron rays as described in claim 1, wherein the aforementioned ion implantation device has a plurality of operating modes for at least partially injecting an ion beam delivered along the aforementioned beamline into at least one of a plurality of sites within the aforementioned ion implantation device, the aforementioned measured value is measured when the aforementioned high-energy ion beam is delivered in at least one of the aforementioned plurality of operating modes, and the aforementioned inferred value is calculated using the neutron dose rate measured in the aforementioned time series data when the aforementioned ion beam is delivered in at least one of the aforementioned plurality of operating modes.

3. The method for monitoring neutron rays as described in claim 2, wherein the aforementioned ion implantation device includes a driving device that changes the position of at least one of the aforementioned plurality of portions, and at least one of the aforementioned plurality of operating modes uses the aforementioned driving device to position at least one of the aforementioned plurality of portions on the aforementioned beam line, thereby at least partially blocking the aforementioned ion beam by means of at least one of the aforementioned plurality of portions.

4. The method for monitoring neutron rays as described in claim 2, wherein the aforementioned ion implantation device includes a deflection device that applies at least one of an electric field and a magnetic field to deflect the trajectory of the aforementioned ion beam, and at least one of the aforementioned plurality of operating modes uses the aforementioned deflection device to direct the aforementioned ion beam into at least one of the aforementioned plurality of locations before the aforementioned beam line is set.

5. A method for monitoring neutron rays as described in any one of claims 2 to 4, wherein the plurality of locations includes a first location and a second location located downstream of the beam line from the first location, and at least one of the plurality of operating modes causes the ion beam to be at least partially incident on the first location and at least partially incident on the second location.

6. A method for monitoring neutron rays as described in any one of claims 2 to 4, wherein the plurality of locations includes a first location and a second location located downstream of the beam line from the first location, and the plurality of operating modes include: The first operating mode causes the aforementioned ion beam to be at least partially injected into the aforementioned first location; The second operating mode allows the aforementioned ion beam to at least partially penetrate the aforementioned second location. The aforementioned measured values ​​include: a first measured value of neutron dose rate, measured at the aforementioned predetermined measurement location when the aforementioned high-energy ion beam is delivered in the aforementioned first operating mode; and a second measured value of neutron dose rate, measured at the aforementioned predetermined measurement location when the aforementioned high-energy ion beam is delivered in the aforementioned second operating mode. The aforementioned inferred values ​​include: a first inferred value, calculated using the neutron dose rate measured when the aforementioned ion beam is delivered in the aforementioned first operating mode from the aforementioned time series data; and a second inferred value, calculated using the neutron dose rate measured when the aforementioned ion beam is delivered in the aforementioned second operating mode from the aforementioned time series data. The aforementioned comparison includes the following steps: comparing the aforementioned first measured value with the aforementioned first inferred value; and comparing the aforementioned second measured value with the aforementioned second inferred value.

7. A method for monitoring neutron rays as described in any one of claims 2 to 4, wherein the plurality of locations includes a first location and a second location located downstream of the beam line from the first location; the predetermined measurement positions include a first measurement position and a second measurement position; and the plurality of operating modes include: The first operating mode causes the aforementioned ion beam to be at least partially injected into the aforementioned first location; And a second operating mode, wherein the aforementioned ion beam is at least partially injected into the aforementioned second location, the aforementioned measured values ​​include: a first measured value of neutron dose rate, measured at the aforementioned first measurement location when the aforementioned high-energy ion beam is delivered in the aforementioned first operating mode; a second measured value of neutron dose rate, measured at the aforementioned first measurement location when the aforementioned high-energy ion beam is delivered in the aforementioned second operating mode; a third measured value of neutron dose rate, measured at the aforementioned second measurement location when the aforementioned high-energy ion beam is delivered in the aforementioned first operating mode; and a fourth measured value of neutron dose rate, measured at the aforementioned second measurement location when the aforementioned high-energy ion beam is delivered in the aforementioned second operating mode. The aforementioned inferred values ​​include: a first inferred value, calculated using the neutron dose rate measured at the first measurement position when the aforementioned ion beam is delivered in the aforementioned first operating mode, as shown in the aforementioned time series data; a second inferred value, calculated using the neutron dose rate measured at the first measurement position when the aforementioned ion beam is delivered in the aforementioned second operating mode, as shown in the aforementioned time series data; a third inferred value, calculated using the neutron dose rate measured at the second measurement position when the aforementioned ion beam is delivered in the aforementioned first operating mode, as shown in the aforementioned time series data; and a fourth inferred value, calculated using the neutron dose rate measured at the second measurement position when the aforementioned ion beam is delivered in the aforementioned second operating mode, as shown in the aforementioned time series data. The aforementioned comparison includes the following steps: comparing the aforementioned first measurement value with the aforementioned first inferred value; comparing the aforementioned second measurement value with the aforementioned second inferred value; comparing the aforementioned third measurement value with the aforementioned third inferred value; and comparing the aforementioned fourth measurement value with the aforementioned fourth inferred value.

8. A method for monitoring neutron radiation as described in any one of claims 1 to 4, wherein the predetermined measurement locations include a first measurement location and a second measurement location, and the measured values ​​include: The first measurement of the neutron dose rate is measured at the aforementioned first measurement location during the delivery of the aforementioned high-energy ion beam; The second measurement of the neutron dose rate is measured at the second measurement location during the delivery of the aforementioned high-energy ion beam; the aforementioned inferred value includes: a first inferred value, calculated using the neutron dose rate measured at the aforementioned first measurement location in the aforementioned time series data; The second inferred value is calculated using the neutron dose rate measured at the second measurement location in the aforementioned time series data. The aforementioned comparison includes the following steps: comparing the aforementioned first measurement value with the aforementioned first inferred value; and comparing the aforementioned second measurement value with the aforementioned second inferred value.

9. A method for monitoring neutron rays as described in any one of claims 1 to 4, wherein the ion type of the aforementioned high-energy ion beam is boron ions, and the energy of the aforementioned high-energy ion beam is above 3.7 MeV and below 10 MeV.

10. A method for monitoring neutron radiation as described in any one of claims 1 to 4, wherein the aforementioned inferred value is calculated using the neutron dose rate corresponding to the beam conditions in the aforementioned time series data, wherein the aforementioned beam conditions are the same type of ion as the aforementioned high-energy ion beam and are high energy within a predetermined energy range.

11. The method for monitoring neutron rays as described in claim 10, wherein the predetermined energy range is above 3.7 MeV and below 10 MeV.

12. The method for monitoring neutron radiation as described in claim 10, wherein the aforementioned inferred value is calculated using the neutron dose rate corresponding to the beam conditions in the aforementioned time series data, the aforementioned beam conditions being the same energy as the aforementioned high-energy ion beam.

13. The method for monitoring neutron radiation as described in claim 10, wherein the aforementioned inferred value is calculated using the neutron dose rate corresponding to the beam conditions in the aforementioned time series data, wherein the aforementioned beam conditions are the same beam current as the aforementioned high-energy ion beam.

14. A method for monitoring neutron radiation as described in any one of claims 1 to 4, wherein the aforementioned comparison includes the step of determining whether the difference between the aforementioned measured value and the aforementioned inferred value exceeds a predetermined threshold value.

15. The method for monitoring neutron radiation as described in claim 14, further comprising the step of: outputting a warning when the difference between the measured value and the inferred value exceeds a predetermined threshold value.

16. The method for monitoring neutron rays as described in claim 14, wherein the aforementioned beam conditions further include transport parameters for controlling at least one of the central trajectory, beam size, and beam shape of the aforementioned ion beam delivered along the aforementioned beam line, and the aforementioned method further includes the step of: comparing the transport parameters of the aforementioned high-energy ion beam with the transport parameters contained in the aforementioned time series data when the difference between the aforementioned measured value and the aforementioned inferred value exceeds the aforementioned predetermined threshold value.

17. A method for monitoring neutron rays as described in any one of claims 1 to 4, wherein the aforementioned ion implantation device comprises: a vacuum container surrounding the aforementioned beam; and a housing disposed outside the aforementioned vacuum container, wherein the predetermined measurement position is outside the aforementioned vacuum container and inside the aforementioned housing.

18. A method for monitoring neutron rays as described in any one of claims 1 to 4, wherein the aforementioned beam includes a curved portion extending in an arc shape, and the aforementioned predetermined measurement position is located inside the aforementioned curved portion.

19. An ion implantation device comprising: an ion source for generating an ion beam; a beamline device configured to deliver the ion beam along the beamline, and including an accelerator for accelerating the ion beam and generating a high-energy ion beam; a neutron beam detector disposed at a predetermined measurement position for measuring a neutron dose rate; a memory storing a program; and a processor, wherein the processor performs the following steps according to the program: recording time-series data that establishes a correspondence between beam conditions including the ion type, energy, and beam current of the ion beam delivered along the beamline and a plurality of past measurement values ​​of the neutron dose rate measured at a plurality of different times using the neutron beam detector in a recording device; delivering the high-energy ion beam along the beamline; and acquiring the current measurement value of the neutron dose rate measured using the neutron beam detector while delivering the high-energy ion beam. Using the aforementioned timing data and the aforementioned beam conditions of the aforementioned high-energy ion beam, calculate the inferred neutron dose rate at the aforementioned predetermined measurement position when the aforementioned high-energy ion beam is currently being delivered; and compare the aforementioned current measurement value with the aforementioned inferred value.

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