Detection device

Abstract

A detection device 1 includes: an insulation layer 15 and a passivation layer 21 (an insulation part) that cover a pn junction region K such that a portion of a p-type semiconductor layer 14 is exposed as an entry region R for electrons E and electrically insulate a p-electrode layer 16 and an n-electrode layer 17; and a scattered electron–blocking part 18 that has an opening 18a that exposes the entry region R and is arranged on one surface 13a side such that the insulation part is not exposed from the opening 18a. The entry region R has an edge part Ra, and a reflected electron–blocking part 19 that separates the entry region R and the insulation part extends along the edge part Ra.

Description

Detection device

[0001] The present disclosure relates to a detection device for detecting charged particles.

[0002] A conventional detection device is described in, for example, Non-Patent Document 1. This conventional detection device has a p-type impurity region on one surface of an n-type semiconductor substrate, which serves as an incident region for charged particles. A p-n junction region is formed between the semiconductor substrate and the p-type impurity region. The p-n junction region is exposed on the surface of the semiconductor substrate, and is covered with an insulating portion except for the incident region for charged particles.

[0003] Japanese Patent Application Laid-Open No. 2006-294563

[0004] GA Johansen, CB Johnson, Nuclear Instruments and Methods in Physics Research A326, pp.295-298(1993)

[0005] The above-described detector has a problem in that dark current increases due to the generation of crystal defects when charged particles are incident on the p-n junction region. To address this problem, a shielding plate can be provided to limit the path of the charged particles incident on the p-n junction region. For example, in the electron detector described in Patent Document 1, a shielding member having an opening for allowing charged particles to be incident on the p-type impurity region is provided to cover the exposed surface of the p-n junction region.

[0006] However, even in a configuration in which a shielding member is provided in a detection device, if the number of charged particles incident on the incident region increases, it is conceivable that the number of electrons reflected from the surface of a member near the incident region (hereinafter referred to as "reflected electrons") will increase. If the number of reflected electrons increases and an increase in the number of electrons reaching the insulating portion that electrically insulates the p-electrode electrically connected to the p-type semiconductor layer from the n-electrode electrically connected to the n-type semiconductor layer increases, the insulating portion may become charged, which may be one of the causes of an increase in dark current.

[0007] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a detection device that can suppress an increase in dark current caused by charging of the insulating part even when the number of incident charged particles increases.

[0008] The gist of the present disclosure is as follows.

[0009] [1] A detection device including: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type provided so as to be exposed on one surface of the first semiconductor layer and forming a p-n junction region between the first semiconductor layer; a first electrode layer electrically connected to the first semiconductor layer; a second electrode layer electrically connected to the second semiconductor layer; an insulating portion covering the p-n junction region so that a portion of the second semiconductor layer is exposed as an incident region of charged particles and electrically insulating the first electrode layer from the second electrode layer; and a first shielding portion having an opening that exposes the incident region and is arranged on the one surface side so that the insulating portion is not exposed from the opening in a planar view of the one surface, wherein a second shielding portion that separates the incident region from the insulating portion extends along the edge of the incident region in a planar view of the one surface.

[0010] In this detection device, the first shielding portion is arranged so that charged particles heading toward the incident region cannot see through the insulating portion. Therefore, even if charged particles heading toward the incident region pass through the opening at various angles due to scattering, the charged particles can be prevented from directly reaching the insulating portion. Furthermore, in this detection device, the second shielding portion separating the incident region from the insulating portion extends along the edge of the incident region. By having the second shielding portion extend along the edge of the incident region, backscattered electrons reflected by the surface of a component near the incident region can be prevented from reaching the insulating portion. Therefore, in this detection device, even if the number of charged particles entering the incident region increases, it is possible to suppress charging of the insulating portion, thereby suppressing an increase in dark current due to charging of the insulating portion.

[0011] [2] The detection device according to [1], wherein the second shielding portion extends over the entire edge of the incident region. In this case, by extending the second shielding portion over the entire edge of the incident region, it is possible to more effectively prevent reflected electrons reflected by the surface of a component near the incident region from reaching the insulating portion. Therefore, it is possible to more reliably prevent an increase in dark current due to charging of the insulating portion.

[0012] [3] The detection device according to [1] or [2], wherein the first shielding portion has a first conductive layer corresponding to the second semiconductor layer, and the second shielding portion is made of a conductive material and electrically connects the second semiconductor layer and the first conductive layer. In this case, signals can be easily extracted from the detection device via the first conductive layer. Furthermore, the second semiconductor layer and the first conductive layer are at the same potential, which suppresses charging of the first shielding portion, thereby stabilizing the output signal.

[0013] [4] The detection device according to any one of [1] to [3], wherein the second shielding portion is composed of a first portion on the second semiconductor layer side and a second portion on the second shielding portion side. In this case, the second shielding portion can be formed simply and accurately by forming the first portion and the second portion separately and aligning them so that they face each other.

[0014] [5] The detection device according to [4], wherein the second shielding portion is configured as multiple portions, and the thickness of the first portion and the thickness of the second portion are different from each other in the multiple second shielding portions. In this case, the multiple second shielding portions can effectively prevent reflected electrons from reaching the insulating portion. Furthermore, the different thicknesses of the first portion and the second portion in the multiple second shielding portions can prevent reflected electrons from reaching the insulating portion even when there is a gap between the first portion and the second portion. If there is a gap between the first portion and the second portion, it is possible to effectively prevent gas from remaining near the second shielding portion when the detection device is used in a vacuum environment.

[0015] [6] The detection device according to any one of [1] to [5], wherein the second shielding portion is configured as multiple portions with at least a discontinuous portion, and the multiple second shielding portions are arranged so that the discontinuous portions do not face each other. In this case, the multiple second shielding portions can effectively prevent reflected electrons from reaching the insulating portion even when each of the multiple second shielding portions has a discontinuous portion. Furthermore, by not having the discontinuous portions of the multiple second shielding portions face each other, it is possible to suitably prevent gas from remaining near the second shielding portion when the detection device is used in a vacuum environment.

[0016] [7] The detection device according to any one of [1] to [3], wherein the second shielding portion is configured by an edge of the opening of the first shielding portion protruding toward the one surface. In this case, the second shielding portion can be configured with a simple structure.

[0017] [8] The detection device according to any one of [1] to [7], wherein a third shielding portion is provided in the region outside the second shielding portion in a plan view of the one surface, separating the insulating portion between the second shielding portion and the region outside the third shielding portion. In this case, the third shielding portion can suppress the intrusion of charged particles from the region outside the second shielding portion. Therefore, an increase in dark current due to charging of the insulating portion can be more reliably suppressed.

[0018] [9] The detection device according to [8], wherein the first shielding portion has a second conductive layer corresponding to the first semiconductor layer, and the third shielding portion is made of a conductive material and electrically connects the first semiconductor layer and the second conductive layer. In this case, signals can be easily extracted from the detection device via the second conductive layer. Furthermore, the first semiconductor layer and the second conductive layer are at the same potential, which suppresses charging of the first shielding portion, thereby stabilizing the output signal.

[0019]

[10] The detection device according to any one of [1] to [9], wherein the first shielding portion is made of ceramic. In this case, the voltage resistance of the first shielding portion can be sufficiently ensured. By ensuring the voltage resistance of the first shielding portion, it is possible to narrow the gap between the first shielding portion and one surface of the first semiconductor layer and the second semiconductor layer, and it is possible to more effectively prevent reflected electrons from reaching the insulating portion.

[0020]

[11] The detection device according to any one of [1] to [9], wherein the first shielding portion is made of Si. In this case, the first shielding portion can be produced inexpensively.

[0021]

[12] The detection device according to any one of [1] to

[11] , wherein the second shielding portion is made of Au. In this case, the degree of freedom in the formation pattern of the second shielding portion can be easily ensured, and sufficient bonding strength can be obtained even with a small metallized area.

[0022] According to the present disclosure, even if the number of incident charged particles increases, an increase in dark current caused by charging of the insulating portion can be suppressed.

[0023] Fig. 3 is a schematic cross-sectional view showing the configuration of a detection device according to an embodiment of the present disclosure. Fig. 4 is a schematic cross-sectional view showing the configuration of a detection unit. Fig. 5 is a schematic plan view showing the detection unit shown in Fig. 2 with a scattered electron shielding unit removed. Fig. 6 is a schematic cross-sectional view showing the configuration of a detection unit according to a modified example. Fig. 7 is a schematic cross-sectional view showing the configuration of a detection unit according to another modified example. Fig. 8 is a schematic plan view showing the detection unit according to another modified example with a scattered electron shielding unit removed. Fig. 9 is a schematic cross-sectional view showing the configuration of a detection unit according to another modified example.

[0024] Hereinafter, a preferred embodiment of a detection device according to one aspect of the present disclosure will be described in detail with reference to the drawings.

[0025] FIG. 1 is a schematic cross-sectional view showing the configuration of a detection device according to an embodiment of the present disclosure. The detection device 1 is a device that detects charged particles such as ions and electrons. In the example of FIG. 1, the detection device 1 is configured as a phototube. The detection device 1 has a cylindrical bulb 2. The bulb 2 is evacuated. An opening at one end of the bulb 2 is sealed by a photocathode plate 3 that serves as an electron source. A photocathode 4 that emits electrons (photoelectrons) E in response to incident photons C is provided on the surface of the photocathode plate 3 facing the inside of the bulb 2. An opening at the other end of the bulb 2 is sealed by a stem 5. The stem 5 has a plurality of through-holes. A lead pin is inserted into each of the through-holes and fixed by a bonding member such as glass.

[0026] Inside the bulb 2, there are provided a plurality of grids (not shown) that focus the electrons E emitted from the photocathode 4. Inside the bulb 2, there is provided a detection unit 11 between the grids and the stem 5. The detection unit 11 is an electron multiplying semiconductor electron sensor that outputs a signal V in response to the incidence of electrons E. In this embodiment, the detection unit 11 has a structure equivalent to that of an avalanche photodiode.

[0027] A constant voltage is supplied to the photocathode 4 from a power supply 6. A reverse bias voltage is supplied to the detection unit 11 from a power supply 7. When a photon C is incident on the photocathode 4 in this state, an electron E is emitted from the photocathode 4 into the bulb 2. The emitted electron E passes through the grid and then enters the incident region R of the detection unit 11. Due to the collision of the electron E upon incidence, electron-hole pairs are generated in the detection unit 11 according to the energy lost by the electron E due to the collision. The generated electron-hole pairs drift within the detection unit 11, to which a reverse bias voltage is supplied, and are avalanche-multiplied in the pn junction region K (see FIG. 2 ) with a multiplication factor according to the reverse bias voltage.

[0028] Fig. 2 is a schematic cross-sectional view showing the configuration of the detection unit. Fig. 3 is a schematic plan view thereof. For convenience of explanation, Fig. 3 shows the planar configuration of the detection unit 11 with a scattered electron shielding portion 18 (described later) removed. As shown in Figs. 2 and 3 , the detection unit 11 is configured to include a substrate 12, an n-type semiconductor layer (first semiconductor layer) 13, a p-type semiconductor layer (second semiconductor layer) 14, an insulating layer 15, a p-electrode layer (second electrode layer) 16, an n-electrode layer (first electrode layer) 17, a scattered electron shielding portion (first shielding portion) 18, a reflected electron shielding portion (second shielding portion) 19, and a sneak electron shielding portion (third shielding portion) 20.

[0029] The substrate 12 is a base of the detection unit 11. The substrate 12 is formed of a metal such as Au and has a rectangular shape in a plan view. The n-type semiconductor layer 13 is a semiconductor layer whose conductivity type is n-type (first conductivity type). The n-type semiconductor layer 13 is made of, for example, Si (silicon). The n-type semiconductor layer 13 is formed on the entire surface 12a of the substrate 12. The p-type semiconductor layer 14 is a semiconductor layer whose conductivity type is p-type (second conductivity type). The p-type semiconductor layer 14 is made of, for example, Si (silicon). The p-type semiconductor layer 14 is provided so as to be partially exposed on one surface 13a of the n-type semiconductor layer 13.

[0030] In this embodiment, the exposed portion of the p-type semiconductor layer 14 from one surface 13a of the n-type semiconductor layer 13 has a circular shape in a plan view. The exposed portion is buried in the center of one surface 13a of the n-type semiconductor layer 13 so as to be flush with one surface 13a of the n-type semiconductor layer 13. A pn ​​junction region K is formed between the p-type semiconductor layer 14 and the n-type semiconductor layer 13.

[0031] The insulating layer 15 electrically insulates the p-electrode layer 16 from the n-electrode layer 17. The insulating layer 15 is made of, for example, SiO ２ The insulating layer 15 is made of an electrically insulating material such as SiO 2 or the like. The insulating layer 15 covers the pn junction region K so that a portion of the p-type semiconductor layer 14 is exposed as an incident region R for electrons E. Here, the insulating layer 15 is provided on one surface 13a of the n-type semiconductor layer 13 so as to cover the periphery of the exposed portion of the p-type semiconductor layer 14 and substantially the entire surface 13a of the n-type semiconductor layer 13. A central circular region of the p-type semiconductor layer 14 is exposed from a central opening 15a of the insulating layer 15. This circular region serves as the incident region R for electrons E to be incident.

[0032] The p-electrode layer 16 is an electrode portion electrically connected to the p-type semiconductor layer 14. The n-electrode layer 17 is an electrode portion electrically connected to the n-type semiconductor layer 13. The p-electrode layer 16 and the n-electrode layer 17 are, for example, Al films formed by vapor deposition of Al (aluminum). When forming the p-electrode layer 16, contact holes 15b that expose the p-type semiconductor layer 14 are provided in the insulating layer 15. The p-electrode layer 16 is formed in a predetermined pattern on the insulating layer 15, filling the contact holes 15b. The n-electrode layer 17 is formed in a predetermined pattern on the insulating layer 15 outside the p-electrode layer 16, along the outer surface 15c of the insulating layer 15, and spaced apart from the p-electrode layer 16.

[0033] The insulating layer 15, the p-electrode layer 16, and the n-electrode layer 17 are covered with a passivation layer 21. The passivation layer 21 is a layer provided for the purpose of protecting the surfaces of the p-electrode layer 16 and the n-electrode layer 17. The passivation layer 21 is made of, for example, silicon nitride (SiN) or SiO ２The passivation layer 21 is formed of an insulating material such as silicon oxide. The passivation layer 21 is provided with an opening 21A that exposes the incident region R together with the opening 15a of the insulating layer 15, an opening 21B that exposes the p-electrode layer 16 corresponding to the reflected electron shielding portion 19, and an opening 21C that exposes the n-electrode layer 17 corresponding to the loop-through electron shielding portion 20. In this embodiment, the passivation layer 21, together with the insulating layer 15, constitutes "an insulating portion that covers the p-n junction region so that a portion of the p-type semiconductor layer 14 is exposed as the incident region R of charged particles and electrically insulates the p-electrode layer 16 and the n-electrode layer 17" in the present disclosure. In an embodiment in which the passivation layer 21 is omitted, the insulating layer 15 alone constitutes the insulating portion in the present disclosure.

[0034] The scattered electron shielding portion 18 is a member that restricts the path of electrons E traveling from the photocathode 4 toward the incident region R. The scattered electron shielding portion 18 is formed in a disk shape using an insulating material such as ceramic, with a thickness sufficient to shield the electrons E. In this embodiment, the diameter of the scattered electron shielding portion 18 is slightly smaller than the planar dimensions of the substrate 12 and the n-type semiconductor layer 13, but the scattered electron shielding portion 18 covers the area extending beyond the opening 21C of the passivation layer 21.

[0035] An opening 18a having a circular cross section and a diameter corresponding to the diameter of the incident region R is provided in the center of the scattered electron shielding portion 18. The scattered electron shielding portion 18 is disposed close to one surface 13a of the n-type semiconductor layer 13 so that the opening 18a faces the incident region R. This ensures that the insulating layer 15 and the passivation layer 21, which are insulating portions, are not exposed (cannot be seen through) from the opening 18a of the scattered electron shielding portion 18 in a plan view of the one surface 13a.

[0036] Among the electrons E emitted from the photocathode 4, in addition to those that pass through the opening 18a along the axial direction (the normal direction of the incident region R), some may be scattered by the inner wall of the bulb 2 or the like and pass through the opening 18a at various angles. However, by arranging the scattered electron shielding portion 18 having a certain thickness close to one surface 13a of the n-type semiconductor layer 13, the scattered electrons Ea that are obliquely incident on the opening 18a collide with the inner wall surface of the opening 18a of the scattered electron shielding portion 18, and their progression is blocked.

[0037] A p-conductive layer (first conductive layer) 22 corresponding to the p-type semiconductor layer 14 and an n-conductive layer (second conductive layer) 23 corresponding to the n-type semiconductor layer 13 are provided on the surface of the scattered electron shielding portion 18. The p-conductive layer 22 and the n-conductive layer 23 are, for example, Au films formed by vapor deposition of Au (gold). The p-conductive layer 22 is formed over the periphery of the opening 18a on one surface 18b of the scattered electron shielding portion 18 (the surface facing one surface 13a of the n-type semiconductor layer 13), the inner wall surface of the opening 18a, and the other surface 18c of the scattered electron shielding portion 18 (the surface opposite to the one surface 18b). The n-conductive layer 23 is formed on the one surface 18b of the scattered electron shielding portion 18, outside the p-conductive layer 22 and spaced apart from the p-conductive layer 22.

[0038] The p-conductive layer 22 and the n-conductive layer 23 are each electrically connected to a conductive wire (not shown). A predetermined voltage is applied to the p-conductive layer 22 and the n-conductive layer 23 via the wire. In this embodiment, the p-conductive layer 22 and the reflected electron shield 19, p-electrode layer 16, and p-type semiconductor layer 14 electrically connected thereto are at ground potential. A positive voltage of, for example, about 400 V to 500 V is applied to the n-conductive layer 23 and the sneak electron shield 20, n-electrode layer 17, and n-type semiconductor layer 13 electrically connected thereto. By specifying the voltages of the p-conductive layer 22 and the n-conductive layer 23, a floating state can be avoided, and the operation of the detection device 1 can be stabilized.

[0039] The reflected electron shielding portion 19 is a member that prevents electrons E (hereinafter referred to as "reflected electrons Eb") reflected on the surface of a member near the incident region R from reaching the insulating portion. The reflected electron shielding portion 19 is, for example, an Au film formed by vapor deposition of Au (gold). In a plan view of the one surface 13a, the reflected electron shielding portion 19 extends along the edge portion Ra of the incident region R so as to separate the incident region R from the insulating portion. In this embodiment, the reflected electron shielding portion 19 is provided in a continuous annular shape across the entire edge portion Ra of the incident region R (see FIG. 3).

[0040] 2 , the space from the opening 18 a of the scattered electron shielding portion 18 to the incident region R is referred to as the incident space H. Reflected electrons Eb emitted in the reflection direction due to electrons incident on the surfaces of components facing the incident space H (such as the surface of the p-type semiconductor layer 14 and the inner wall of the opening 18 a) can reach the insulating portion via various paths. As the number of electrons E incident on the incident region R increases, the number of reflected electrons Eb also increases, and some of the reflected electrons Eb may reach the insulating portion covering the pn junction region (particularly, the portion of the passivation layer 21 that electrically insulates the p electrode layer 16 and the n electrode layer 17). In contrast, because the reflected electron shielding portion 19 extends to the edge portion Ra of the incident region R, the reflected electrons Eb emitted due to the electrons E entering the incident space H collide with the reflected electron shielding portion 19, blocking their travel.

[0041] In this embodiment, the reflected electron shielding portion 19 has a portion 19a extending along the inner wall surface of the central opening 15a in the insulating layer 15 and the inner wall surface of the opening 21A in the passivation layer 21, a portion 19b filling the opening 21B in the passivation layer 21, and a portion 19c extending on the passivation layer 21 so as to connect these portions 19a and 19b (see FIG. 2 ). The portion 19a contacts the p-type semiconductor layer 14 in the opening 15a in the insulating layer 15, and the portion 19b contacts the p-electrode layer 16 in the opening 21B in the passivation layer 21. The portion 19c contacts the p-conductive layer 22 of the scattered electron shielding portion 18 on the passivation layer 21. As a result, the reflected electron shielding portion 19 is in a state where it electrically connects the p-type semiconductor layer 14 and the p-conductive layer 22 of the scattered electron shielding portion 18, and a predetermined potential is applied to the p-type semiconductor layer 14 via the p-conductive layer 22 and the reflected electron shielding portion 19.

[0042] The loop-in electron shielding portion 20 is a member that suppresses the escape of electrons E from an area outside the reflected electron shielding portion 19. The loop-in electron shielding portion 20 is, for example, an Au film formed by vapor deposition of Au (gold), similar to the reflected electron shielding portion 19. The loop-in electron shielding portion 20 is provided so as to separate the insulating portion between it and the reflected electron shielding portion 19 (here, the portion of the passivation layer 21 that is located between the p electrode layer 16 and the n electrode layer 17) from the area outside it.

[0043] More specifically, the looping electron shielding portion 20 extends linearly along each of the four sides of the detection unit 11 in a plan view of one surface 13 a, for a length longer than the diameter of the annular reflected electron shielding portion 19, so that the reflected electron shielding portion 19 cannot be seen from outside the detection unit 11 (see FIG. 3 ). In this embodiment, the ends of the looping electron shielding portion 20 on each side are discontinuous. When viewed as a whole, the looping electron shielding portion 20 is provided in the shape of a rectangular frame with discontinuous corners so as to surround the reflected electron shielding portion 19.

[0044] Among the electrons E emitted from the photocathode 4, some may be scattered or reflected by the inner wall of the bulb 2, and may not head toward the opening 18a of the scattered electron shielding portion 18, but may invade between the n-type semiconductor layer 13 and the scattered electron shielding portion 18 from the side of the detection device 1 (hereinafter referred to as "introjected electrons Ec"). In contrast, by arranging the introjected electron shielding portion 20 so that the reflected electron shielding portion 19 is not visible when viewed from the outside of the detection portion 11, such introjected electrons Ec collide with the introjected electron shielding portion 20, and their progression is blocked.

[0045] In this embodiment, the sneak-in electron shielding portion 20 has a portion 20a that fills the opening 21C of the passivation layer 21 and a portion 20b that protrudes from the opening 21C. The portion 20a is in contact with the n-electrode layer 17 within the opening 21C of the passivation layer 21. The portion 20b protrudes from the opening 21C of the passivation layer 21. The portion 20b extends toward the scattered electron shielding portion 18 and is in contact with the n-conductive layer 23 of the scattered electron shielding portion 18. As a result, the sneak-in electron shielding portion 20 electrically connects the n-type semiconductor layer 13 and the n-conductive layer 23 of the scattered electron shielding portion 18, and a predetermined potential is applied to the n-type semiconductor layer 13 via the n-conductive layer 23 and the sneak-in electron shielding portion 20.

[0046] As described above, in the detection device 1, the scattered electron shielding portion 18 is arranged so that the insulating layer 15 and the passivation layer 21, which are insulating portions, are not visible to the electrons E heading toward the incident region R. Therefore, even if the electrons E heading toward the incident region R pass through the opening 18a at various angles due to scattering, the scattered electrons Ea can be prevented from directly reaching the insulating portion. Furthermore, in the detection device 1, the reflected electron shielding portion 19 that separates the incident region R from the insulating portion extends along the edge portion Ra of the incident region R. By having the reflected electron shielding portion 19 extend along the edge portion Ra of the incident region R, reflected electrons Eb reflected by the surface of a component near the incident region R can be prevented from reaching the insulating portion. Therefore, in the detection device 1, even if the number of electrons E incident on the incident region R increases, charging of the insulating portion can be suppressed, and an increase in dark current due to charging of the insulating portion can be suppressed.

[0047] In this embodiment, the reflected electron shielding portion 19 extends over the entire edge portion Ra of the incident region R. By extending the reflected electron shielding portion 19 over the entire edge portion Ra of the incident region R, it is possible to more effectively prevent reflected electrons Eb reflected by the surface of a member in the vicinity of the incident region R from reaching the insulating portion. Therefore, it is possible to more reliably prevent an increase in dark current caused by charging of the insulating portion.

[0048] In this embodiment, the scattered electron shielding portion 18 has a p-conductive layer 22 corresponding to the p-type semiconductor layer 14, and the reflected electron shielding portion 19 is made of a conductive material and electrically connects the p-type semiconductor layer 14 and the p-conductive layer 22. With this configuration, it is possible to easily extract a signal from the detection device 1 and apply a potential to the p-type semiconductor layer 14 via the p-conductive layer 22. Furthermore, the p-type semiconductor layer 14 and the p-conductive layer 22 have the same potential, which suppresses charging of the scattered electron shielding portion 18, thereby stabilizing the output signal.

[0049] In this embodiment, in a plan view of the one surface 13a, a loop-in electron shielding portion 20 is provided in the region outside the reflected electron shielding portion 19, separating the insulating portion between the reflected electron shielding portion 19 and the region outside it. By providing such a loop-in electron shielding portion 20, it is possible to suppress the loop-in of electrons from the region outside the reflected electron shielding portion 19. Therefore, it is possible to more reliably suppress an increase in dark current caused by charging of the insulating portion.

[0050] In this embodiment, the scattered electron shielding portion 18 has an n-conductive layer 23 corresponding to the n-type semiconductor layer 13, and the sneak electron shielding portion 20 is made of a conductive material and electrically connects the n-type semiconductor layer 13 and the n-conductive layer 23. With this configuration, it is possible to easily extract a signal from the detection device 1 and apply a potential to the n-type semiconductor layer 13 via the n-conductive layer 23. Furthermore, the n-type semiconductor layer and the n-conductive layer 23 have the same potential, which suppresses charging of the scattered electron shielding portion 18, thereby stabilizing the output signal.

[0051] In the case where the detection device 1 is a phototube having a photocathode 4 as in this embodiment, the sneak electron shielding portion 20 also functions as a member that suppresses adhesion of the alkali metal used in the process of forming the photocathode 4 to the insulating portion (particularly the portion of the passivation layer 21 that is located between the p electrode layer 16 and the n electrode layer 17). By suppressing adhesion of the alkali metal to the insulating portion that is located between the p electrode layer 16 and the n electrode layer 17, it is possible to prevent a decrease in the surface resistance of the insulating portion, and thereby suppress the generation of dark current that results from this.

[0052] In this embodiment, the loop-in electron shielding portion 20 is provided in the shape of a rectangular frame with discontinuous corners so as to surround the reflected electron shielding portion 19. By making the loop-in electron shielding portion 20 in a discontinuous shape (not a closed shape), when the detection device 1 is used in a vacuum environment, it is possible to suitably suppress the residual gas inside the loop-in electron shielding portion 20 when the inside of the bulb 2 is evacuated. Therefore, it is possible to prevent a decrease in the degree of vacuum inside the bulb 2 after the bulb 2 is vacuum-sealed.

[0053] In this embodiment, the scattered electron shielding portion 18 is made of ceramic. This ensures sufficient voltage resistance of the scattered electron shielding portion 18. By ensuring the voltage resistance of the scattered electron shielding portion 18, it becomes possible to narrow the gap between the scattered electron shielding portion 18 and the one surface 13a, and it is possible to more effectively prevent reflected electrons Eb from reaching the insulating portion. Furthermore, in this embodiment, the reflected electron shielding portion 19 is made of an Au film. This makes it easy to ensure flexibility in the formation pattern of the reflected electron shielding portion 19, and sufficient bonding strength can be obtained even with a small metallized region.

[0054] The present disclosure is not limited to the above-described embodiment. For example, in the above-described embodiment, the reflected electron shielding portion 19 extends over the entire edge portion Ra of the incidence region R. However, the reflected electron shielding portion 19 does not necessarily have to extend over the entire edge portion Ra of the incidence region R, as long as it has at least a portion extending along the edge portion Ra. For example, a portion of the reflected electron shielding portion 19 may be discontinuous, and continuous and discontinuous portions may be provided alternately along the edge portion Ra of the incidence region R (i.e., the reflected electron shielding portion 19 may be provided in the form of a dashed line).

[0055] In the above embodiment, the scattered electron shielding portion 18 is made of ceramic. However, the scattered electron shielding portion 18 may be made of silicon (Si). In this case, the scattered electron shielding portion 18 can be manufactured inexpensively. When the scattered electron shielding portion 18 is made of silicon, the electrical connection between the n-electrode layer 17 and the n-conductive layer 23 of the scattered electron shielding portion 18 by the sneak electron shielding portion 20 may be omitted, as shown in FIG. 4 , taking into account the electrical resistance of silicon (Si). In this case, the spacing between the scattered electron shielding portion 18 and the n-electrode layer 17 can be secured, thereby preventing short circuits between the scattered electron shielding portion 18 and the n-electrode layer 17. In the configuration of FIG. 4 , conductive wires or the like can be directly electrically connected to the p-electrode layer 16, the n-electrode layer 17, and the p-conductive layer 22, thereby enabling signals to be extracted and voltages to be applied to the detection portion 11 via the wires.

[0056] In the above embodiment, a single layer of the reflected electron shielding portion 19 is provided on the edge portion Ra of the incidence region R. However, as shown in Fig. 5, multiple layers of the reflected electron shielding portion 19 may be provided on the edge portion Ra of the incidence region R. By providing multiple layers of the reflected electron shielding portion 19, it is possible to effectively prevent the reflected electrons Eb from reaching the insulating portion.

[0057] 5 , the reflected electron shielding portion 19 is provided in multiple layers, and is composed of a first portion 19A on the p-type semiconductor layer 14 side and a second portion 19B on the scattered electron shielding portion 18 side. Here, the first portion 19A is formed by depositing Au (gold) on the p-electrode layer 16, and the second portion 19B is formed by depositing Au (gold) on the p-conductive layer 22 of the scattered electron shielding portion 18. The first portion 19A and the second portion 19B can be formed by, for example, vapor deposition or plating. The first portion 19A and the second portion 19B may be composed of a conductive adhesive or a metal member.

[0058] In the multiple backscattered electron shielding portion 19, the thickness of the first portion 19A and the thickness of the second portion 19B may be equal to each other, or the thickness of the first portion 19A and the thickness of the second portion 19B may be different from each other. Here, the thicknesses of the first portion 19A and the second portion 19B refer to the lengths in the direction connecting one surface 13a of the n-type semiconductor layer 13 and one surface 18b of the scattered electron shielding portion 18. In other words, the thicknesses of the first portion 19A and the second portion 19B refer to the heights in the thickness direction of the substrate 12. In the example of FIG. 5 , the backscattered electron shielding portion 19 is configured as a double layer. In the inner backscattered electron shielding portion 19, the thickness of the first portion 19A is greater than the thickness of the second portion 19B, and in the outer backscattered electron shielding portion 19, the thickness of the second portion 19B is greater than the thickness of the first portion 19A. Conversely, in the inner reflected electron shielding portion 19, the thickness of the second portion 19B may be greater than the thickness of the first portion 19A, and in the outer reflected electron shielding portion 19, the thickness of the first portion 19A may be greater than the thickness of the second portion 19B.

[0059] 5 , the thickness of the first portion 19A and the thickness of the second portion 19B are different from each other, resulting in a slight gap being provided between the first portion 19A and the second portion 19B. With this configuration, even when the reflected electron shielding portion 19 is provided over the entire edge portion Ra of the incidence region R, it is possible to suitably suppress the gas from remaining inside the reflected electron shielding portion 20 (i.e., the space sandwiched between the reflected electron shielding portion 19 and the reflected electron shielding portion 20) when the bulb 2 is evacuated, just as in the case where the reflected electron shielding portion 20 has a discontinuous shape.

[0060] The first portion 19A and the second portion 19B may be configured to be in contact with each other. In this case, there is no gap between the first portion 19A and the second portion 19B, which more reliably prevents reflected electrons Eb from passing through the gap and reaching the insulating portion. In a configuration in which the first portion 19A and the second portion 19B are in contact with each other, the reflected electron shield 19 electrically connects the p-type semiconductor layer 14 and the p-conductive layer 22, as in the embodiment shown in FIG. 2 . This makes it easy to extract signals from the detection device 1 and apply a potential to the p-type semiconductor layer 14 via the p-conductive layer 22. Furthermore, the p-type semiconductor layer 14 and the p-conductive layer 22 are at the same potential, which prevents charging of the scattered electron shield 18 and stabilizes the output signal.

[0061] A configuration may be provided in which both a contact portion where first portion 19A and second portion 19B are in contact with each other and a non-contact portion where first portion 19A and second portion 19B are not in contact with each other are provided. For example, the contact portion and non-contact portion may be provided alternately in the circumferential direction of reflected electron shielding portion 19 provided over the entire edge portion Ra of incidence region R. In this case, reflected electron shielding portion 19 electrically connects p-type semiconductor layer 14 and p-conductive layer 22, and can also effectively suppress gas remaining inside return electron shielding portion 20 when the bulb 2 is evacuated.

[0062] When multiple backscattered electron shielding portions 19 are provided, each of the backscattered electron shielding portions 19 does not necessarily have to be continuous over the entire edge portion Ra of the incidence region R, and may have at least a portion having a discontinuous portion M. In the example of Fig. 6, the inner backscattered electron shielding portion 19 and the outer backscattered electron shielding portion 19 each have a discontinuous portion M. The inner backscattered electron shielding portion 19 and the outer backscattered electron shielding portion 19 are arranged so that the discontinuous portions M, M do not face each other in the radial direction.

[0063] According to this configuration, the backscattered electron shielding portions 19 are multiple, and thus it is possible to effectively prevent the backscattered electrons Eb from reaching the insulating portion even when the discontinuous portions M are provided in each of the multiple backscattered electron shielding portions 19. Furthermore, by not having the discontinuous portions M, M face each other in the radial direction in the multiple backscattered electron shielding portions 19, it is possible to suitably prevent gas from remaining in the vicinity of the backscattered electron shielding portions 19 (the space sandwiched between the inner backscattered electron shielding portion 19 and the outer backscattered electron shielding portion 19) when the detection device 1 is used in a vacuum environment.

[0064] As shown in Fig. 7 , the scattered electron shielding portion 18 may also function as the reflected electron shielding portion 19. In this case, the reflected electron shielding portion 19 can be configured with a simple structure. In the example of Fig. 7 , the entire edge 18d of the opening 18a of the scattered electron shielding portion 18 protrudes toward the one surface 13a in correspondence with the edge Ra of the incident region R, and the edge 18d functions as the reflected electron shielding portion 19. In the example of Fig. 7 , the p-conductive layer 22 is continuous also on the surface of the edge 18da. The p-conductive layer 22 is in direct contact with the p-type semiconductor layer 14, thereby electrically connecting the p-type semiconductor layer 14 and the p-conductive layer 22.

[0065] 7 , similarly to the embodiment shown in FIG. 2 , the reflected electron shielding portion 19 made of an Au film electrically connects the p-electrode layer 16 and the p-conductive layer 22. In this case, the edge portion 18d of the scattered electron shielding portion 18 serves as the inner reflected electron shielding portion 19, and the Au film electrically connecting the p-type semiconductor layer 14 and the p-conductive layer 22 serves as the outer reflected electron shielding portion 19. Therefore, the reflected electron shielding portions 19 are multiplexed, and it is possible to effectively prevent the reflected electrons Eb from reaching the insulating portion.

[0066] 7 , when the edge 18d of the opening 18a of the scattered electron shielding portion 18 protrudes toward the one surface 13a, the p-conductive layer 22 does not necessarily have to be in contact with the p-type semiconductor layer 14. In this case, a gap is created between the p-conductive layer 22 and the p-type semiconductor layer 14, which can suitably prevent gas from remaining between the inner and outer reflected electron shielding portions 19 when the detection device 1 is used in a vacuum environment. When the edge 18d of the opening 18a of the scattered electron shielding portion 18 protrudes toward the one surface 13a as in FIG. 7 , the reflected electron shielding portion 19 made of an Au film may be omitted. In this case, the configuration of the detection device 1 can be further simplified.

[0067] 1...detection device, 13...n-type semiconductor layer (first semiconductor layer), 13a...one side, 14...p-type semiconductor layer (second semiconductor layer), 15...insulating layer (insulating portion), 16...p electrode layer (second electrode layer), 17...n electrode layer (first electrode layer), 18...scattered electron shielding portion (first shielding portion), 18a...opening, 18d...edge portion (second shielding portion), 19...reflected electron shielding portion (second shielding portion), 19A...first portion, 19B...second portion, 20...reflected electron shielding portion (third shielding portion), 21...passivation layer (insulating portion), 22...p conductive layer (first conductive layer), E...electrons (charged particles), K...pn junction region, R...incident region, Ra...edge portion, M...discontinuous portion.

Claims

a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type provided so as to be exposed on one side of the first semiconductor layer and forming a p-n junction region between the first semiconductor layer and the first electrode layer; a second electrode layer electrically connected to the first semiconductor layer; a second electrode layer electrically connected to the second semiconductor layer; an insulating portion covering the p-n junction region so that a part of the second semiconductor layer is exposed as an incidence region for charged particles and electrically insulating the first electrode layer and the second electrode layer; and a first shielding portion having an opening exposing the incidence region and disposed on the one side such that the insulating portion is not exposed from the opening in a plan view of the one side, wherein a second shielding portion extends along an edge of the incidence region and separates the incidence region from the insulating portion in a plan view of the one side.

2. A detection device as claimed in claim 1, wherein said second shielding portion extends over the entire edge of said incident area.

3. A detection device as described in claim 1 or 2, wherein the first shielding portion has a first conductive layer corresponding to the second semiconductor layer, and the second shielding portion is made of a conductive material and electrically connects the second semiconductor layer and the first conductive layer.

4. A detection device according to any one of claims 1 to 3, wherein the second shielding portion is composed of a first portion on the second semiconductor layer side and a second portion on the second shielding portion side.

5. A detection device according to claim 4, wherein the second shielding portion is constructed in a multiple-layer structure, and in the multiple second shielding portions, the thickness of the first portion and the thickness of the second portion are different from each other.

6. A detection device as claimed in any one of claims 1 to 5, wherein the second shielding portion is configured in multiple layers with at least a portion of the second shielding portion being discontinuous, and the multiple second shielding portions are arranged so that the discontinuous portions do not face each other.

7. A detection device as claimed in any one of claims 1 to 3, wherein the second shielding portion is formed by an edge of the opening of the first shielding portion protruding towards the one surface side.

8. A detection device as claimed in any one of claims 1 to 7, wherein in a plan view of the one side, a third shielding portion is provided in the area outside the second shielding portion, separating the insulating portion between the second shielding portion and the area outside the second shielding portion.

9. The detection device according to claim 8, wherein the first shielding portion has a second conductive layer corresponding to the first semiconductor layer, and the third shielding portion is made of a conductive material and electrically connects the first semiconductor layer and the second conductive layer.

10. A detection device according to any one of claims 1 to 9, wherein the first shielding portion is made of ceramic.

11. A detection device according to any one of claims 1 to 9, wherein the first shielding portion is made of Si.

12. A detection device according to any one of claims 1 to 11, wherein the second shielding portion is made of Au.

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