Radiation detection element, radiation detector, and radiation detection device

Abstract

Provided are a radiation detection element, radiation detector, and radiation detection device that make it possible to suppress reduction in the sensitivity of radiation detection.　This radiation detection element comprising a flat-plate-shaped semiconductor part comprises: a doping layer that is provided on one surface of the semiconductor part, is doped with a dopant, and comprises a semiconductor of a type that is different from that of the semiconductor part; an insulation layer that covers the doping layer; and a metal layer that is laid over the insulation layer. The electric potential of the doping layer and the electric potential of the metal layer are different.

Description

Technical Field

[0001] The present invention relates to a radiation detection element, a radiation detector, and a radiation detection device.

Background Art

[0002] Among radiation detectors that detect radiation such as X-rays, there are those equipped with a radiation detection element using a semiconductor. The radiation detection element using a semiconductor includes a flat semiconductor portion. On the surface of the radiation detection element, a doping layer doped with a dopant and made of a semiconductor of a type different from that of the semiconductor portion is provided. A voltage is applied using the doping layer, and an electric field is generated inside the semiconductor portion. When radiation enters the semiconductor portion, charges are generated inside the semiconductor portion, and the charges move to the electrodes according to the electric field, and a signal corresponding to the amount of charge is output from the electrodes, and the radiation is detected.

[0003] The doping layer is covered with an insulating layer made of an oxide. When radiation enters the insulating layer, charges are generated in the insulating layer, and a part of the generated charges stays near the interface between the insulating layer and the doping layer. A part of the charges generated in the semiconductor portion is attracted to the charges staying near the interface, and the signal output from the electrodes decreases. For this reason, the sensitivity for detecting radiation decreases. Patent Document 1 discloses a radiation detection element in which a metal layer is stacked on an insulating layer. By allowing charges to flow through the metal layer, a decrease in the sensitivity for detecting radiation is alleviated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Even in a radiation detection element in which a metal layer is stacked on an insulating layer, when there is a large amount of incident radiation, there is a problem that a large amount of charge stays in the insulating layer and the sensitivity for detecting radiation decreases.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to provide a radiation detection element, a radiation detector, and a radiation detection device capable of suppressing a decrease in sensitivity for detecting radiation.

Means for Solving the Problems

[0007] The radiation detection element according to the present invention is a radiation detection element including a flat semiconductor part, and is provided on one surface of the semiconductor part, and a doping layer which is doped with a dopant and is a semiconductor of a type different from that of the semiconductor part, an insulating layer covering the doping layer, and a metal layer overlapping the insulating layer, and is characterized in that the potential of the doping layer and the potential of the metal layer are different potentials.

[0008] In one embodiment of the present invention, a doping layer is provided on one surface of the semiconductor part, the doping layer is covered with an insulating layer, and a metal layer overlaps the insulating layer. By making the potential of the doping layer and the potential of the metal layer different potentials, a potential difference is generated. Due to the potential difference, it becomes easier for charge to move from the insulating layer to the metal layer, and the number of charges staying in the insulating layer decreases. The charge that has moved to the metal layer is discharged through the metal layer. Since the number of charges staying in the insulating layer decreases, it becomes difficult for the charge in the semiconductor part to be attracted to the charge in the insulating layer. Since it becomes difficult for the charge generated in the semiconductor part by radiation to be attracted to the charge in the insulating layer, a decrease in the intensity of the signal output from the radiation detection element is suppressed.

[0009] In the radiation detection element according to the present invention, the component of the semiconductor part is an n-type semiconductor, the component of the doping layer is a p-type semiconductor, and the potential of the metal layer is lower than the potential of the doping layer.

[0010] In one embodiment of the present invention, the semiconductor portion is an n-type semiconductor, the doping layer is a p-type semiconductor, and the radiation detection element outputs a signal corresponding to electrons generated in the semiconductor portion. Since the potential of the metal layer is lower than the potential of the doping layer, holes generated in the insulating layer are likely to move to the metal layer. Since the number of holes in the insulating layer decreases, electrons in the semiconductor portion are less likely to be attracted to the holes in the insulating layer. Since electrons generated in the semiconductor portion by radiation are less likely to be attracted to the charges in the insulating layer, a decrease in the intensity of the signal output from the radiation detection element is suppressed.

[0011] In the radiation detection element according to the present invention, a part of one surface of the semiconductor portion is an incident region where radiation is incident, and the doping layer is provided over the entire incident region.

[0012] In one embodiment of the present invention, a doping layer is provided over the entire incident region on one surface of the semiconductor portion where radiation is incident. By the doping layer, an electric field is generated throughout the range where radiation enters the semiconductor portion, and charges are collected by the electric field. Charges generated in the semiconductor portion are efficiently collected by the electric field, and a signal having an intensity corresponding to the energy of the radiation incident on the semiconductor portion is output.

[0013] The radiation detection element according to the present invention further includes an electrode that penetrates the insulating layer and is connected to the doping layer, and a voltage is applied through the electrode so that the potential of the doping layer becomes a potential different from the potential of the metal layer.

[0014] In one embodiment of the present invention, the doping layer is connected to an electrode that penetrates the insulating layer. By applying a voltage through the electrode, the potential of the doping layer and the potential of the metal layer can be made different.

[0015] The radiation detection element according to the present invention is a silicon drift type radiation detection element.

[0016] In one embodiment of the present invention, the radiation detection element is a silicon drift type radiation detection element. Since the decrease in the intensity of the signal output from the radiation detection element is suppressed, the widening of the width of the peak included in the spectrum of the radiation toward the low energy side is suppressed. It becomes possible to actually realize the feature that the width of the peak is narrow by using the silicon drift type radiation detection element.

[0017] The radiation detector according to the present invention is characterized by including the radiation detection element according to the present invention, a substrate on which the radiation detection element is mounted, and a housing that houses the radiation detection element and the substrate.

[0018] In one embodiment of the present invention, by setting the potential of the doping layer and the potential of the metal layer to different potentials, the decrease in the intensity of the signal output from the radiation detection element is suppressed. Therefore, the decrease in the intensity of the signal output from the radiation detector including the radiation detection element is suppressed.

[0019] In the radiation detector according to the present invention, the housing has an opening that is not blocked, and the radiation detection element is disposed at a position facing the opening.

[0020] In one embodiment of the present invention, the radiation incident on the radiation detection element does not need to pass through the opening and transmit through the window material. For this reason, the radiation detector can detect radiation that cannot transmit through the window material due to low energy. Even when a large amount of low-energy radiation is incident on the radiation detection element, the decrease in the intensity of the signal is suppressed, so that the radiation detector can accurately detect low-energy radiation.

[0021] The radiation detection device according to the present invention includes an irradiation unit that irradiates a sample with radiation, a radiation detector according to the present invention that detects the radiation generated from the sample, a voltage application unit that applies a voltage to the radiation detection element so that the potentials of the doping layer and the metal layer of the radiation detection element are different from each other, a spectrum generation unit that generates a spectrum of the radiation detected by the radiation detector, and a display unit that displays the spectrum generated by the spectrum generation unit.

[0022] In one embodiment of the present invention, by setting the potential of the doping layer and the potential of the metal layer to different potentials, a decrease in the intensity of the signal output from the radiation detection element is suppressed. Therefore, a decrease in the intensity of the signal output from the radiation detector including the radiation detection element is suppressed, and a decrease in the sensitivity of the radiation detection device to detect radiation is suppressed.

Advantages of the Invention

[0023] In the present invention, a decrease in the intensity of the signal output from the radiation detection element and the radiation detector is suppressed. Therefore, the present invention has excellent effects such as suppression of a decrease in the sensitivity of the radiation detection device to detect radiation.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0025] The present invention will be specifically described below based on the drawings showing its embodiments. <Embodiment 1> FIG. 1 is a schematic cross-sectional view of the radiation detection element 1. The radiation detection element 1 is a silicon drift type radiation detection element. The radiation detection element 1 is generally flat-plate shaped. The radiation detection element 1 includes a disk-shaped Si layer 11 made of Si (silicon). The component of the Si layer 11 is, for example, n-type Si. The Si layer 11 is a semiconductor part. The Si layer 11 has a first surface 111 and a second surface 112 located on the back side of the first surface 111. The second surface 112 is mainly the incident surface on which radiation is incident.

[0026] At the center of the first surface 111, a signal output electrode 161, which is an electrode that outputs a signal during radiation detection, is provided. The component of the signal output electrode 161 is Si of the same type as the Si layer 11 and is doped with a specific dopant such as phosphorus. For example, the component of the signal output electrode 161 is n+Si. Also, on the first surface 111, a plurality of curved electrodes 162 in a multiple ring shape are provided. The component of the curved electrode 162 is Si of a type different from that of the Si layer 11. For example, the component of the curved electrode 162 is p-type Si, which is p+Si doped with a specific dopant such as boron in Si. The plurality of curved electrodes 162 arranged in a ring shape are substantially concentric, and the signal output electrode 161 is located substantially at the center of the plurality of curved electrodes 162. That is, the plurality of curved electrodes 162 surround the signal output electrode 161, and the distances between the signal output electrode 161 and each of the curved electrodes 162 are different.

[0027] FIG. 1 shows four curved electrodes 162, but actually more curved electrodes 162 are provided. Note that the shape of the curved electrode 162 may be a deformed shape of an annulus or a shape in which a part is segmented. The multiple curved electrodes 162 do not have to be concentric. Alternatively, the signal output electrode 161 may be disposed at a position other than the center of the multiple curved electrodes 162, or may be disposed at a position other than the center of the first surface 111. An earth electrode 163 connected to the earth potential is provided outside the plurality of curved electrodes 162. The first surface 111 is covered with an insulating layer 17 made of an oxide or nitride of Si or the like.

[0028] FIG. 2 is a schematic plan view of the radiation detection element 1 as viewed from the side of the second surface 112. FIG. 1 shows a cross-sectional view taken along the two-dot chain line shown in FIG. 2. FIG. 2 shows an example in which the shape of the radiation detection element 1 is disk-shaped. The shape of the radiation detection element 1 may be a shape other than disk-shaped. The shape of the radiation detection element 1 may be a droplet type in plan view, or may be a plate shape having a polygonal shape such as a square, rectangle, trapezoid or hexagon.

[0029] A doping layer 12 doped with more dopants than the dopants contained in the Si layer 11 is provided on the second surface 112. The component of the doping layer 12 is Si of a different type from the Si layer 11. If the component of the Si layer 11 is n-type Si, the component of the doping layer 12 is p-type Si, for example p+ Si. The doping layer 12 is formed by implanting dopants into the Si layer 11. A part of the second surface 112 including the center of the second surface 112 is set as an incident region 113 where radiation to be detected is incident. The doping layer 12 is formed in most of the region including the center of the second surface 112 and is provided over the entire incident region 113.

[0030] A ground electrode 15 connected to a ground potential is provided between the edge of the doping layer 12 and the edge of the second surface 112. The ground electrode 15 is annular in plan view. The second surface 112 is covered with an insulating layer 13 made of an oxide or nitride of Si or the like. The insulating layer 13 covers the doping layer 12 and the ground electrode 15. A metal layer 14 overlaps the insulating layer 13. The metal layer 14 is a metal film made of a metal such as Al (aluminum) or Au (gold). When the side of the second surface 112 of the Si layer 11 is the upper side, the insulating layer 13 overlaps the doping layer 12, and the metal layer 14 overlaps the insulating layer 13. The metal layer 14 is disposed at a position overlapping a portion including the center of the second surface 112. As shown in FIG. 2, in plan view, the metal layer 14 overlaps the doping layer 12 and occupies a region narrower than the doping layer 12.

[0031] As shown in FIGS. 1 and 2, a through electrode 121 penetrating the insulating layer 13 is connected to the doping layer 12. For example, the through electrode 121 is made of metal. The through electrode 121 is in a ring shape with a part being segmented in plan view. The through electrode 121 is located above the peripheral portion of the doping layer 12. The insulating layer 13 is penetrated by the through electrode 121 in a ring shape with a part being segmented. The through electrode 121 is in contact with and connected to a part of the peripheral portion of the doping layer 12 that is in a ring shape with a part being segmented. The through electrode 121 substantially surrounds the metal layer 14 in plan view. A part of the metal layer 14 is disposed at the position where the ring of the through electrode 121 is segmented. The through electrode 121 is separated from the metal layer 14.

[0032] An electrode 151 penetrating the insulating layer 13 is in contact with and connected to the ground electrode 15. The electrode 151 is annular and surrounds the metal layer 14 and the through electrode 121 in plan view. The electrode 151 is separated from the metal layer 14 and the through electrode 121.

[0033] The through electrode 121 is connected to the voltage application unit 31. The doping layer 12 is connected to the voltage application unit 31 via the through electrode 121. The metal layer 14 is also connected to the voltage application unit 31. Also, among the multiple curved electrodes 162, the innermost curved electrode 162 and the outermost curved electrode 162 are connected to the voltage application unit 31.

[0034] The voltage application unit 31 applies a voltage such that the potential of the innermost curved electrode 162 is the highest and the potential of the outermost curved electrode 162 is the lowest. Also, the radiation detection element 1 is configured such that a predetermined electrical resistance is generated between adjacent curved electrodes 162 with different distances from the signal output electrode 161. For example, by adjusting the components of the portion located between adjacent curved electrodes 162, an electrical resistance channel through which the two curved electrodes 162 are connected is formed. That is, the plurality of curved electrodes 162 are connected in series via electrical resistances. When a voltage is applied to such a plurality of curved electrodes 162 from the voltage application unit 31, each curved electrode 162 has a potential that monotonically increases sequentially from the outer curved electrode 162 toward the inner curved electrode 162. That is, the potential of the curved electrode 162 increases sequentially from the curved electrode 162 far from the signal output electrode 161 toward the curved electrode 162 close to the signal output electrode 161. Note that a pair of adjacent curved electrodes 162 having the same potential may be included among the plurality of curved electrodes 162.

[0035] Due to the potentials of the plurality of curved electrodes 162, an electric field (potential gradient) is generated in the Si layer 11 such that the potential is higher closer to the signal output electrode 161 and lower farther from the signal output electrode 161 in a stepwise manner. Also, the voltage application unit 31 applies a voltage to the doping layer 12 such that the potential of the doping layer 12 becomes the potential between the innermost curved electrode 162 and the outermost curved electrode 162. In this way, an electric field in which the potential increases closer to the signal output electrode 161 is generated inside the Si layer 11. Since the doping layer 12 is provided over the entire incident region 113, an electric field is generated throughout the range where radiation in the Si layer 11 is incident.

[0036] Furthermore, the voltage application unit 31 applies a voltage to the doping layer 12 and the metal layer 14 so that the potential of the doping layer 12 and the potential of the metal layer 14 become different potentials. More specifically, the voltage application unit 31 applies a voltage to the doping layer 12 and the metal layer 14 so that the potential of the metal layer 14 becomes lower than the potential of the doping layer 12. For example, the potential of the metal layer 14 is -7V compared to the potential of the doping layer 12. In this way, a potential difference is generated in which the potential of the metal layer 14 is lower than the potential of the doping layer 12. Since the potential of the metal layer 14 is lower than the potential of the doping layer 12, a pulling force acts on the positive charges generated inside the insulating layer 13 toward the metal layer 14.

[0037] A preamplifier 21 is connected to the signal output electrode 161. Radiation such as X-rays, general photons (including UV and visible light), electron beams, or other charged particle beams is incident on the radiation detection element 1. The radiation mainly enters the Si layer 11 through the incident region 113 on the second surface 112. An amount of charge corresponding to the energy of the radiation absorbed in the Si layer 11 is generated in the Si layer 11. The generated charges are electrons and holes. The generated charges move by the electric field inside the Si layer 11, and one type of charge concentrates and flows into the signal output electrode 161. In this embodiment, when the signal output electrode 161 is of n-type, the electrons generated by the incidence of radiation move and flow into the signal output electrode 161. The charge flowing into the signal output electrode 161 becomes a current signal and is output, and is input to the preamplifier 21. The preamplifier 21 converts the current signal into a voltage signal. The preamplifier 21 outputs a signal with an intensity corresponding to the energy of the radiation. Since an electric field is generated in the range where the radiation in the Si layer 11 is incident, the electrons efficiently flow into the signal output electrode 161, and a signal with an intensity corresponding to the energy of the radiation incident on the Si layer 11 is output.

[0038] When radiation enters the radiation detection element 1, the radiation also enters the insulating layer 13. Due to the incidence of radiation, charges are generated in the insulating layer 13. When the Si layer 11 is n-type and the doping layer 12 is p-type, holes generated in the insulating layer 13 may stay near the interface between the insulating layer 13 and the doping layer 12, and electrons in the Si layer 11 may be attracted to the trapped holes. When electrons in the Si layer 11 are attracted to holes in the insulating layer 13, some of the electrons generated in the Si layer 11 by radiation may not flow into the signal output electrode 161 or the inflow may be delayed. Therefore, the intensity of the signal output by the signal output electrode 161 decreases, leading to a decrease in the sensitivity of radiation detection.

[0039] In this embodiment, by setting the potential of the doping layer 12 and the potential of the metal layer 14 to different potentials, a potential difference that pulls the charges in the insulating layer 13 toward the metal layer 14 is generated. Since the potential of the metal layer 14 is lower than the potential of the doping layer 12, a potential difference that pulls the holes generated in the insulating layer 13 toward the metal layer 14 is generated. A part of the charges in the insulating layer 13 can move to the metal layer 14. Due to the potential difference that pulls the holes toward the metal layer 14, it becomes easier for the holes to move from the insulating layer 13 to the metal layer 14, and the proportion of the holes that move to the metal layer 14 among the holes in the insulating layer 13 increases. The holes that have moved to the metal layer 14 pass through the metal layer 14 and flow to the voltage application unit 31. That is, the holes that have moved from the insulating layer 13 to the metal layer 14 are discharged to the outside of the radiation detection element 1. In this way, the proportion of the holes discharged from the insulating layer 13 increases, and the number of holes staying in the insulating layer 13 decreases.

[0040] Since the number of holes staying in the insulating layer 13 decreases, it becomes difficult for the electrons in the Si layer 11 to be attracted to the holes in the insulating layer 13. Therefore, it is suppressed that some of the electrons generated in the Si layer 11 by radiation do not flow into the signal output electrode 161 or the inflow is delayed. Accordingly, it is suppressed that the intensity of the signal output by the signal output electrode 161 decreases, and the decrease in the sensitivity of radiation detection is suppressed.

[0041] FIG. 3 is a schematic cross-sectional view showing a configuration example of a radiation detector 2 including a radiation detection element 1 according to Embodiment 1. The radiation detector 2 is an SDD (Silicon Drift Detector). The radiation detector 2 includes a housing 25 having a shape in which a truncated cone is connected to one end of a cylinder. The housing 25 is configured by covering a plate-shaped bottom plate portion with a cap-shaped cover. A window 26 for transmitting radiation is provided at the tip of the housing 25. Inside the housing 25, a radiation detection element 1, a collimator 22, a substrate 23, a cooling unit 28, and a cold finger 24 are arranged. The housing 25 houses the radiation detection element 1, the collimator 22, the substrate 23, and the cooling unit 28. The cooling unit 28 is, for example, a Peltier element.

[0042] The radiation detection element 1 is mounted on the surface of the substrate 23 and is arranged at a position facing the window 26. The radiation detection element 1 is arranged such that the first surface 111 faces the substrate 23 and the second surface 112 faces the window 26. The collimator 22 has a cylindrical shape with both ends open and is made of a material that shields radiation. The collimator 22 is arranged between the radiation detection element 1 and the window 26. One end of the collimator 22 faces the window 26, and the other end faces the surface of the radiation detection element 1. Radiation mainly enters the inside of the housing 25 through the window 26, and the collimator 22 shields a part of the radiation. The portion of the second surface 112 other than the incident region 113 is covered with the collimator 22 that shields radiation, and no radiation is incident. The incident region 113 is not covered with the collimator 22, and radiation is incident. The radiation detection element 1 detects the radiation that enters without being shielded by the collimator 22.

[0043] Wiring is formed on the substrate 23, and the preamplifier 21 is mounted thereon. In FIG. 3, the preamplifier 21 is omitted. The substrate 23 is in thermal contact with the heat absorption part of the cooling part 28 directly or via an intervening object. The heat dissipation part of the cooling part 28 is in thermal contact with the cold finger 24. The cold finger 24 has a flat plate-like part with which the heat dissipation part of the cooling part 28 is in thermal contact and a part that penetrates the bottom plate part of the housing 25. The heat of the radiation detection element 1 is absorbed by the cooling part 28 through the substrate 23, transmitted from the cooling part 28 to the cold finger 24, and dissipated to the outside of the radiation detector 2 through the cold finger 24.

[0044] The radiation detector 2 includes a plurality of lead pins 27 that penetrate the bottom plate part of the housing 25. The lead pins 27 are connected to the substrate 23 by a method such as wire bonding. The application of voltage to the radiation detection element 1 by the voltage application unit 31 and the output of the signal from the preamplifier 21 are performed through the lead pins 27. Note that the radiation detector 2 may further include other components.

[0045] FIG. 4 is a block diagram showing a functional configuration example of the radiation detection device 10. The radiation detection device 10 is, for example, a fluorescent X-ray analysis device. The radiation detection device 10 includes an irradiation unit 4 that irradiates a sample 6 with radiation such as an electron beam or X-ray, a sample stage 5 on which the sample 6 is placed, and a radiation detector 2. The radiation detector 2 includes the radiation detection element 1 and the preamplifier 21. Note that a part of the preamplifier 21 may be included inside the radiation detector 2 and the other part may be arranged outside the radiation detector 2.

[0046] The sample 6 is irradiated with radiation from the irradiation unit 4, radiation such as fluorescent X-ray is generated in the sample 6, and the radiation detector 2 detects the radiation generated from the sample 6. In the figure, the radiation is indicated by arrows. The radiation detector 2 outputs a signal proportional to the energy of the detected radiation. Note that the radiation detection device 10 may be configured to hold the sample 6 by a method other than placing it on the sample stage 5.

[0047] The radiation detector 2 is connected to a voltage application unit 31 and a signal processing unit 32 that processes the output signal. The voltage application unit 31 is connected to the radiation detection element 1, and the signal processing unit 32 is connected to the preamplifier 21. When the preamplifier 21 outputs a signal, the radiation detector 2 outputs a signal with an intensity corresponding to the energy of the radiation. The signal processing unit 32 detects the signal value corresponding to the energy of the radiation detected by the radiation detector 2 by detecting the intensity of the signal output by the radiation detector 2. An analysis unit 34 is connected to the signal processing unit 32. The analysis unit 34 includes an arithmetic unit that performs calculations and a memory that stores data. The voltage application unit 31, the signal processing unit 32, the analysis unit 34, and the irradiation unit 4 are connected to a control unit 33. The control unit 33 controls the operations of the voltage application unit 31, the signal processing unit 32, the analysis unit 34, and the irradiation unit 4.

[0048] The signal processing unit 32 outputs data indicating the detected signal value to the analysis unit 34. Based on the data from the signal processing unit 32, the analysis unit 34 counts the signals of each value and performs a process of generating the relationship between the energy of the radiation and the count number, that is, the spectrum of the radiation. The signal processing unit 32 and the analysis unit 34 correspond to a spectrum generation unit. Further, the analysis unit 34 performs qualitative analysis or quantitative analysis of the elements contained in the sample 6 based on the spectrum. Note that the signal processing unit 32 may generate the spectrum of the radiation.

[0049] A display unit 35 such as a liquid crystal display is connected to the analysis unit 34. The display unit 35 displays the spectrum generated by the analysis unit 34 and the analysis result by the analysis unit 34. The control unit 33 may be configured to receive an operation by a user and control each part of the radiation detection device 10 according to the received operation. Also, the control unit 33 and the analysis unit 34 may be configured by the same computer.

[0050] As described in detail above, in this embodiment, since the potential of the metal layer 14 is lower than the potential of the doping layer 12, a potential difference is generated that pulls the holes generated in the insulating layer 13 toward the metal layer 14. Due to the potential difference, holes easily move from the insulating layer 13 to the metal layer 14, and the number of holes remaining in the insulating layer 13 decreases. Since the number of holes remaining in the insulating layer 13 decreases, it becomes difficult for the electrons in the Si layer 11 to be attracted to the holes in the insulating layer 13. Even when there is a large incidence of radiation on the radiation detection element 1, the number of holes remaining in the insulating layer 13 is small, and the electrons in the Si layer 11 are less likely to be affected by the holes in the insulating layer 13. It is suppressed that a part of the electrons generated in the Si layer 11 by radiation does not flow into the signal output electrode 161 or the inflow is delayed. For this reason, it is suppressed that the intensity of the signal output from the signal output electrode 161 decreases. Therefore, it is suppressed that the intensity of the signal output from the radiation detector 2 decreases, and a decrease in the sensitivity of the radiation detection device 10 to detect radiation is suppressed.

[0051] Since the radiation detection element 1 is a silicon drift type radiation detection element, the signal-to-noise ratio of the output signal is high. For this reason, the width of the peak included in the spectrum of the radiation becomes narrow. However, when the intensity of the signal output from the signal output electrode 161 decreases due to the influence of the holes in the insulating layer 13, the energy of the radiation corresponding to the signal is measured to be lower than the actual value, and the width of the peak included in the spectrum becomes wider on the low energy side. In this embodiment, since it is suppressed that the intensity of the signal output from the signal output electrode 161 decreases, it is suppressed that the width of the peak included in the spectrum becomes wider on the low energy side. It becomes possible to actually realize the feature that the width of the peak is narrow by using a silicon drift type radiation detection element, and high-precision analysis becomes possible.

[0052] <Embodiment 2> FIG. 5 is a schematic cross-sectional view showing a configuration example of the radiation detector 2 according to Embodiment 2. An opening 251 is formed in the truncated portion at the tip of the housing 25. A window having a window material is not provided in the opening 251, and the opening 251 is not blocked. The radiation detection element 1 is disposed at a position facing the opening 251, and the second surface 112 is disposed so as to face the opening 251. The configuration of the other parts of the radiation detector 2 is the same as that of Embodiment 1. The configuration of the parts of the radiation detection device 10 other than the radiation detector 2 is the same as that of Embodiment 1.

[0053] In Embodiment 2, the radiation that mainly passes through the opening 251 enters the radiation detection element 1 and is detected. Since the opening 251 is not blocked by a window material, the radiation does not need to pass through the window material. Therefore, radiation having low energy that cannot pass through the window material can also enter the radiation detection element 1. Radiation having relatively high energy is likely to enter deep into the radiation detection element 1, and radiation having relatively low energy is likely to generate charges in a portion close to the surface of the radiation detection element 1. Therefore, the radiation that generates charges in the insulating layer 13 is low-energy radiation. When a large amount of low-energy radiation enters the radiation detection element 1, the number of charges generated in the insulating layer 13 can increase.

[0054] However, since the potential of the metal layer 14 is lower than the potential of the doping layer 12, the number of holes remaining in the insulating layer 13 decreases, so that electrons in the Si layer 11 are less likely to be attracted to the holes in the insulating layer 13. For this reason, it is suppressed that a part of the electrons generated in the Si layer 11 by radiation does not flow into the signal output electrode 161 or the inflow is delayed. Therefore, even when a large amount of low-energy radiation enters the radiation detection element 1, a decrease in the intensity of the signal output from the signal output electrode 161 is suppressed.

[0055] In Embodiment 2, the radiation detector 2 can detect radiation that cannot penetrate the window material due to its low energy. For example, the radiation detection device 10 can detect elements with low-energy fluorescent X-rays by detecting low-energy fluorescent X-rays, making it possible to detect elements with low-energy fluorescent X-rays. Even when a large amount of low-energy radiation enters the radiation detection element 1, the decrease in the signal intensity is suppressed, so the radiation detector 2 can accurately detect low-energy radiation.

[0056] In Embodiments 1 and 2, a Peltier element is shown as an example of the cooling unit 28, but the radiation detector 2 may be configured with a cooling unit 28 other than the Peltier element. The radiation detector 2 may be configured without the cold finger 24 or without the cooling unit 28.

[0057] In Embodiments 1 and 2, a form is shown in which the Si layer 11 is made of n-type Si and the doping layer 12 is made of p-type Si. However, the radiation detection element 1 may be configured such that the Si layer 11 is made of p-type Si and the doping layer 12 is made of n-type Si. In this form, holes flow into the signal output electrode 161 and a signal is output. The voltage application unit 31 applies a voltage to the doping layer 12 and the metal layer 14 so that the potential of the metal layer 14 becomes higher than the potential of the doping layer 12. A potential difference is generated that pulls the electrons generated in the insulating layer 13 towards the metal layer 14. Due to the potential difference, electrons easily move from the insulating layer 13 to the metal layer 14, and the number of electrons remaining in the insulating layer 13 decreases. The holes in the Si layer 11 are less likely to be attracted by the electrons in the insulating layer 13, and a decrease in the intensity of the signal output by the signal output electrode 161 is suppressed. Therefore, even in this form, a decrease in the sensitivity of radiation detection is suppressed.

[0058] In Embodiments 1 and 2, the form in which the radiation detection element 1 is a silicon drift type radiation detection element was shown. However, as long as the radiation detection element 1 is a semiconductor element, it may be an element other than the silicon drift type radiation detection element. For this reason, the radiation detector 2 may be a radiation detector other than an SDD. In Embodiments 1 and 2, the form in which radiation is irradiated onto the sample 6 and the radiation generated from the sample 6 is detected was shown. However, the radiation detection device 10 may be in a form that detects radiation transmitted through the sample 6 or reflected by the sample 6. The radiation detection device 10 may be in a form that scans the sample 6 with radiation by changing the direction of the radiation. The radiation detection device 10 may be in a form that does not include the irradiation unit 4, the sample stage 5, the analysis unit 34, or the display unit 35.

[0059] The present invention is not limited to the content of the above-described embodiments, and various modifications are possible within the scope shown in the claims. That is, embodiments obtained by combining technical means appropriately modified within the scope shown in the claims are also included in the technical scope of the present invention.

Explanation of Signs

[0060] 10 Radiation detection device 1 Radiation detection element 11 Si layer (semiconductor part) 12 Doping layer 13 Insulating layer 14 Metal layer 2 Radiation detector 25 Housing 251 Opening 31 Voltage application unit 32 Signal processing unit 34 Analysis unit 35 Display unit 4 Irradiation unit 5 Sample stage 6 Sample

Claims

1. In a radiation detection element including a flat semiconductor part, a doping layer provided on one surface of the semiconductor part, which is doped with a dopant and is a semiconductor of a type different from that of the semiconductor part, an insulating layer covering the doping layer, and a metal layer overlapping the insulating layer, wherein the potential of the doping layer and the potential of the metal layer are different from each other A radiation detection element characterized by that.

2. The component of the semiconductor part is an n-type semiconductor, The component of the doping layer is a p-type semiconductor, The potential of the metal layer is lower than the potential of the doping layer The radiation detection element according to claim 1, characterized by that.

3. A part of one surface of the semiconductor part is an incident region where radiation is incident, The doping layer is provided over the entire incident region The radiation detection element according to claim 1 or 2, characterized by that.

4. Further comprising an electrode that penetrates the insulating layer and is connected to the doping layer, A voltage is applied through the electrode so that the potential of the doping layer is different from the potential of the metal layer The radiation detection element according to any one of claims 1 to 3, characterized by that.

5. The radiation detection element according to any one of claims 1 to 4, characterized by being a silicon drift type radiation detection element.

6. A radiation detection element according to any one of claims 1 to 5, a substrate on which the radiation detection element is mounted, and a housing that houses the radiation detection element and the substrate A radiation detector characterized by comprising.

7. The housing has an opening that is not blocked, The radiation detection element is disposed at a position facing the opening The radiation detector according to claim 6, characterized by that.

8. An irradiation unit that irradiates a sample with radiation, The radiation detector according to claim 6 or 7 that detects radiation generated from the sample, A voltage application unit that applies a voltage to the radiation detection element so that the potentials of the doping layer and the metal layer of the radiation detection element are different from each other, A spectrum generation unit that generates a spectrum of the radiation detected by the radiation detector, And a display unit that displays the spectrum generated by the spectrum generation unit A radiation detection device characterized by comprising.

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