Light-emitting body, charged particle detector, electron microscope, and mass spectrometer

Abstract

This light emitting body (10) converts incident charged particles into light, and is provided with a multiple quantum well structure (14C) that emits light by the incidence of charged particles. The well layer (141) constituting the multiple quantum well structure (14C) has a thickness of 0.2 nm or more and less than 1.5 nm. The concentration of an additive added to a barrier layer (142) and a well layer (141) constituting the multiple quantum well structure (14C) is greater than 4 * 1018 cm <-3 > and 1 * 1020 cm <-3 > or less.

Description

Technical Field

[0001] One aspect of the present invention relates to a light emitter, a charged particle detector, an electron microscope, and a mass analysis device. Background Technology

[0002] Patent Document 1 describes a light emitter that converts incident electrons into light. The light emitter described in Patent Document 1 comprises a substrate, a nitride semiconductor layer formed on one side of the substrate and having a quantum well structure, a capping layer stacked on the nitride semiconductor layer and made of a material with a band gap energy greater than that of the constituent material of the nitride semiconductor layer, and a metal plating layer formed on the capping layer. Existing technical documents Patent documents

[0003] Patent Document 1: Japanese Patent No. 4365255 Summary of the Invention The technical problem the invention aims to solve

[0004] In the aforementioned luminescent devices, for example, to capture events occurring in a shorter time, there is a desire to further improve high-speed response. Therefore, one object of the present invention is to provide a luminescent device, a charged particle detector, an electron microscope, and a mass analysis apparatus that can further improve high-speed response. Technical means for solving problems

[0005] Through repeated and active research, the inventors discovered that the thickness of the trap layer in the luminescent material is related to the afterglow time. Furthermore, they found that the concentration of additives in the luminescent material is related to the afterglow time, with a relationship that a higher additive concentration results in a shorter afterglow time. On the other hand, they found that when the additive concentration exceeds a certain level, for example, crystallinity deteriorates, leading to a significant decrease in luminescence intensity, making practical application difficult. Therefore, the inventors further conducted repeated and active research, concluding that optimizing the thickness of the trap layer and the concentration of additives in both the barrier layer and the trap layer would allow for a reduction in afterglow time while maintaining luminescence intensity, thereby further improving high-speed response and thus completing one aspect of the present invention.

[0006] (1) That is, one aspect of the light emitter of the present invention is a light emitter that converts incident charged particles into light, comprising: a multiple quantum well structure that emits light through the incident charge particles, wherein the thickness of the well layer constituting the multiple quantum well structure is 0.2 nm or more and less than 1.5 nm; and the concentration of the additives added to the barrier layer and the well layer constituting the multiple quantum well structure is greater than 4 × 10⁻⁶. 18 cm -3 And it is 1×10 20 cm -3 the following.

[0007] In this light emitter, the thickness of the well layer is greater than 0.2 nm and less than 1.5 nm, and the concentration of additives in the barrier layer and well layer is greater than 4 × 10⁻⁶. 18 cm -3 And it is 1×10 20 cm -3 In this case, by optimizing the thickness of the trap layer and the concentration of additives in the barrier and trap layers based on the above insights, the afterglow time can be reduced while maintaining luminescence intensity. Therefore, the response time can be further shortened, and high-speed response can be further improved.

[0008] (2) The light emitter as described in (1) above, wherein the thickness of the trap layer may be 0.6 nm or more and less than 1.0 nm. In this case, the afterglow time can be further reduced.

[0009] (3) The luminescent body as described in (1) or (2) above, wherein it may be a multiple quantum well structure comprising a first barrier layer and a second barrier layer as barrier layers, the second barrier layer being located relative to the first barrier layer on the charged particle incident surface side of the multiple quantum well structure; the first barrier layer is thicker than the second barrier layer. Thus, by varying the thickness of the barrier layers according to the distance from the charged particle incident surface, the light conversion efficiency can be improved from a smaller accelerating voltage to a larger accelerating voltage, thereby increasing the luminous intensity.

[0010] (4) The light emitter as described in any one of (1) to (3) above, wherein the well layer and the barrier layer may be nitride semiconductor layers, and the additives include silicon. In this case, the well layer and the barrier layer may be nitride semiconductor layers, and silicon may be used as an additive thereto.

[0011] (5) A charged particle detector according to one aspect of the present invention comprises: a light emitter as described in any one of (1) to (4) above; and a photodetector optically coupled to a surface in a multiple quantum well structure opposite to the charged particle incident surface, and having sensitivity to light emitted from the multiple quantum well structure. Even in this charged particle detector, because of the light emitter described above, high-speed response can be further improved.

[0012] (6) An electron microscope according to one aspect of the present invention comprises: a light emitter as described in any one of (1) to (4); a photodetector optically coupled to a surface in a multiple quantum well structure opposite to the incident surface of charged particles, and sensitive to light emitted from the multiple quantum well structure; and a chamber in which at least one light emitter is disposed, an electron beam is irradiated onto the surface of a sample disposed in the chamber, electrons from the sample are directed to the light emitter, and an image of the sample is obtained by establishing a correspondence between the irradiation position of the electron beam in the sample and the output of the photodetector. Even in this electron microscope, because of the aforementioned light emitter, high-speed response can be further improved.

[0013] (7) A mass analysis apparatus according to one aspect of the present invention comprises: a light emitter as described in any one of (1) to (4); a photodetector optically coupled to a surface in a multiple quantum well structure opposite to the incident surface of charged particles, and sensitive to light emitted from the multiple quantum well structure; a chamber in which at least one light emitter is disposed; a separation section spatially or temporally separating ions generated from a sample in the chamber according to their mass; and an electron conversion section irradiated with ions separated by the separation section, guiding electrons emitted from the electron conversion section according to the incident direction of ions to the electron conversion section, and performing mass analysis of the sample based on the output of the photodetector. Even in this mass analysis apparatus, because of the aforementioned light emitter, high-speed response can be further improved. The effects of the invention

[0014] According to one aspect of the present invention, a luminescent material, a charged particle detector, an electron microscope, and a mass analysis device that can further improve high-speed responsiveness can be provided. Attached Figure Description

[0015] Figure 1 This is a cross-sectional view showing the structure of the light-emitting body in the first embodiment. Figure 2 It is an enlarged representation Figure 1 A cross-sectional view of the internal structure of a multiple quantum well structure. Figure 3 It means in Figure 1 A graph showing the decay (decay) of the luminescent material as the thickness of the trap layer changes. Figure 4 It means in Figure 1 A graph showing the decay of the luminescent material as the concentration of the additive changes. Figure 5 It means in Figure 1 A graph showing the luminescence intensity when the thickness of the trap layer is varied in the luminescent body. Figure 6 It means in Figure 1 A graph showing the luminescence intensity as the concentration of additives in the luminescent body changes. Figure 7 It means Figure 1 A graph showing the relationship between attenuation and luminescence intensity in a luminescent body. Figure 8 This is a cross-sectional view showing the configuration of the electron beam detector in the second embodiment. Figure 9 This is a schematic diagram illustrating the configuration of the length measuring SEM (Scanning Electron Microscope) of the third embodiment. Figure 10This is a diagram that schematically illustrates the configuration of the quality analysis apparatus according to the fourth embodiment. Detailed Implementation

[0016] The embodiments will now be described in detail with reference to the accompanying drawings. The same or equivalent parts are indicated by the same reference numerals in each drawing, and repeated descriptions are omitted.

[0017] [First Implementation] Figure 1 This is a cross-sectional view showing the structure of the light-emitting element 10 in the first embodiment, showing a cross-section along the thickness direction. The light-emitting element 10 converts incident charged particles, which in this embodiment are electrons, into light. Figure 1 As shown, the light emitter 10 includes a substrate 12, a nitride semiconductor layer 14 disposed on the main surface 12a of the substrate 12, and a conductive layer 18 disposed on the nitride semiconductor layer 14. The surface of the conductive layer 18 forms an electron incident surface (charged particle incident surface) 10a.

[0018] The substrate 12 is a plate-shaped member that is transmissive to light of wavelengths emitted from the nitride semiconductor layer 14. The material of the substrate 12 is not particularly limited, as long as it allows light emitted from the nitride semiconductor layer 14 to pass through and allows the nitride semiconductor layer 14 to be epitaxially grown. In one example, the substrate 12 is a sapphire substrate. In another example, the substrate 12 transmits light with wavelengths of 170 nm or higher. The substrate 12 has a main surface 12a and a back surface 12b located opposite the main surface 12a.

[0019] The nitride semiconductor layer 14 includes a first buffer layer 14A disposed on the main surface 12a of the substrate 12, a second buffer layer 14B disposed on the first buffer layer 14A, and a multiple quantum well structure 14C disposed on the second buffer layer 14B.

[0020] The first buffer layer 14A is a layer used to grow the multiple quantum well structure 14C with good crystallinity, and is in contact with the main face 12a. The first buffer layer 14A is grown at a relatively low temperature (e.g., above 400°C and below 700°C) and has an amorphous structure mainly comprising, for example, gallium (Ga) and nitrogen (N). In one example, the first buffer layer 14A comprises amorphous GaN. The thickness of the first buffer layer 14A is, for example, above 5 nm and below 500 nm, and in one embodiment, it is 20 nm.

[0021] The second buffer layer 14B is also a layer for growing the multiple quantum well structure 14C with good crystallinity, and mainly contains, for example, GaN crystals. In one example, the second buffer layer 14B contains GaN crystals. The second buffer layer 14B is epitaxially grown at a temperature higher than that of the first buffer layer 14A (for example, 700 °C or higher and 1200 °C or lower). The thickness of the second buffer layer 14B is, for example, 1 μm or more and 10 μm or less, and is 2.5 μm in one example. The second buffer layer 14B may be in contact with the first buffer layer 14A.

[0022] The multiple quantum well structure 14C is a part that emits light upon incidence of electrons, and is a layer epitaxially grown on the second buffer layer 14B. Figure 2 is a cross-sectional view showing an enlarged internal structure of the multiple quantum well structure 14C. As Figure 2 shown, the multiple quantum well structure 14C has a structure in which well layers 141 and barrier layers 142 are alternately stacked.

[0023] The well layer 141 is a light-emitting layer formed of a material that receives electrons and emits light. The well layer 141 mainly contains, for example, In x Ga 1-x N (0 < x < 1) crystal nitride semiconductor layer. In one example, the well layer 141 contains Si-doped In x Ga 1-x N (0 < x < 1) crystal. When electrons enter the multiple quantum well structure 14C, electron-hole pairs are formed, and light is emitted (cathodoluminescence) during the process of recombination within the well layer 141. The compositions of the multiple well layers 141 constituting the multiple quantum well structure 14C are the same as each other, and the above-mentioned composition x is equal to each other. In one embodiment, the composition x is 0.1. In addition, the thicknesses of the multiple well layers 141 constituting the multiple quantum well structure 14C are equal to each other.

[0024] The bandgap energy of the barrier layer 142 is greater than the bandgap energy of the well layer 141. By sandwiching the well layer 141 between the barrier layers 142, electrons can be collected into the well layer 141 and efficiently converted into light. The barrier layer 142 is a nitride semiconductor layer mainly containing GaN crystals. In one example, the barrier layer 142 contains Si-doped GaN crystals. In addition, the barrier layer 142 may further contain group III atoms other than Ga (for example, In). Even in this case, the compositions of the multiple barrier layers 142 constituting the multiple quantum well structure 14C are equal to each other.

[0025] The thicknesses of the multiple barrier layers 142 constituting the multiple quantum well structure 14C are different from each other. Specifically, each barrier layer 142 is relative to each barrier layer 142 located on the electron incident surface 10a (see Figure 1The barrier layer 142 on the side closest to the electron incident surface 10a is thicker. In other words, the barrier layers 142 become thicker the further away from the electron incident surface 10a, and the first barrier layer 142 closest to the electron incident surface 10a is the thinnest among the barrier layers 142. In a preferred embodiment, the thickness of the first barrier layer 142 closest to the electron incident surface 10a is 80% or less of the average thickness of the barrier layers 142, more preferably 20% or less. The thickness of the second barrier layer 142 (i.e., the barrier layer 142 adjacent to the barrier layer 142 closest to the electron incident surface 10a) is 90% or less of the average thickness of the barrier layers 142, more preferably 80% or less.

[0026] In the multiple quantum well structure 14C of this embodiment, nine barrier layers 142 are provided. The initial well layer 141 is provided between the first barrier layer 142 and the second barrier layer 142 counting from the electron incident surface 10a. Subsequently, the nth (n=2, ..., 8) well layer 141 is provided between the nth barrier layer 142 and the (n+1)th barrier layer 142 counting from the electron incident surface 10a. Furthermore, between the last (9th) well layer 141 and the second buffer layer 14B, a barrier layer 143 having the same composition as each barrier layer 142 is provided (see reference). Figure 2 The thickness of the barrier layer 143 does not affect the characteristics of the light emitter 10, for example, it is 10 nm. Alternatively, the barrier layer 143 may be omitted if necessary.

[0027] In this embodiment, among all the multiple barrier layers 142, the barrier layer 142 is thicker the further away from the electron incident surface 10a. However, if most of the multiple barrier layers 142 satisfy this condition, the effect of this embodiment is hardly impaired even if some barrier layers 142 do not satisfy this condition. That is, the effect of this embodiment described later is better achieved when a certain barrier layer 142 (hereinafter also referred to as "first barrier layer") is thicker than another barrier layer 142 (hereinafter also referred to as "second barrier layer") located on the electron incident surface 10a side relative to that barrier layer 142.

[0028] In this embodiment, the difference in thickness between adjacent barrier layers 142 decreases the further away from the electron incident surface 10a. Furthermore, if most of the barrier layers 142 satisfy this condition, the effect of this embodiment is hardly diminished even if some barrier layers 142 do not satisfy this condition. That is, the effect described later is better achieved when the difference in thickness between a pair of adjacent barrier layers 142 is less than the difference in thickness between another pair of adjacent barrier layers 142 located on the electron incident surface 10a side relative to that pair of barrier layers 142.

[0029] The conductive layer 18 serves as an electrode for guiding electrons to the light emitter 10. The conductive layer 18 primarily comprises, for example, a metal, and in one embodiment, primarily aluminum (Al). The thickness of the conductive layer 18 is, for example, 10 nm or more and 1000 nm or less, and in one embodiment, about 300 nm. When the conductive layer 18 primarily comprises a metal, it also functions as a light-reflecting film. That is, a portion of the light generated in the multiple quantum well structure 14C directly reaches the substrate 12 from the multiple quantum well structure 14C and is emitted to the outside of the light emitter 10 through the substrate 12, but the remaining portion of the light generated in the multiple quantum well structure 14C reaches the conductive layer 18, is reflected in the conductive layer 18, and is emitted to the outside of the light emitter 10 through the substrate 12.

[0030] An example related to the fabrication method of the light emitter 10 will be described. First, the substrate 12 is introduced into the growth chamber of a metal-organic vapor phase (MOVPE) apparatus and subjected to a heat treatment at 1100°C for 10 minutes in a hydrogen atmosphere to clean the main surface 12a. Then, the temperature of the substrate 12 is lowered to 500°C, and after depositing the first buffer layer 14A, the temperature of the substrate 12 is raised to 1100°C to epitaxially grow the second buffer layer 14B. Subsequently, the temperature of the substrate 12 is lowered to 800°C to form In... x Ga 1-x The N / GaN multiple quantum well structure 14C is constructed. Furthermore, by moving the substrate 12 into the evaporation apparatus, a conductive layer 18 is formed on the multiple quantum well structure 14C, thereby completing the fabrication of the light emitter 10.

[0031] Furthermore, in the above examples, trimethylgallium (Ga(CH3)3:TMGa) can be used as the Ga source, trimethylindium (In(CH3)3:TMIn) as the In source, ammonia (NH3) as the N source, hydrogen (H2) or nitrogen (N2) as the carrier gas, and monosilane (SiH4) as the Si source. Alternatively, other organometallic raw materials (e.g., triethylgallium (Ga(C2H5)3:TEGa), triethylindium (In(C2H5)3:TEIn), etc.) and other hydrides (e.g., disilane (Si2H4), etc.) can also be used. Additionally, although an MOVPE apparatus is used in the above examples, a hydride vapor phase growth (HVPE) apparatus or a molecular beam epitaxy (MBE) apparatus can also be used. Furthermore, the growth temperatures are not limited to the temperatures described above.

[0032] In this embodiment, the thickness of the well layer 141 is 0.2 nm or more and less than 1.5 nm. Preferably, the thickness of the well layer 141 is 0.6 nm or more and less than 1.0 nm. The additives (hereinafter also referred to as "additives") added to the barrier layer 142 and the well layer 141 comprise silicon. The concentration of the additives is greater than 4 × 10⁻⁶. 18 cm -3 And it is 1×10 20 cm -3 The following is an explanation of additives, also known as dopants, and the concentration of these additives is called the Si doping concentration.

[0033] Figure 3 This is a graph showing the decay as the thickness of the trap layer 141 in the luminescent body 10 changes. The decay is the afterglow time, defined as the time it takes for the intensity to drop from 90% to 10% of its peak value. In the graph, circles represent measured values, and line segments represent values ​​derived from the measured values ​​(the same applies to the following graphs). Example 1 uses an additive concentration of 4 × 10⁻⁶. 18 cm -3 Example 2 is an example where the concentration of the additive is 1.5 × 10⁻⁶. 19 cm -3 This is an example of a situation. The threshold α is a value set based on the decay of a typical luminescent material, which is 3.5 ns in this case. The threshold α is not specifically defined.

[0034] like Figure 3 As shown, the attenuation varies quadratically with the thickness of the well layer 141. In the illustrated example, the quadratic function of attenuation has a bottom between 0.2 nm and 1.5 nm (around 0.8 nm in this case) when the thickness of the well layer 141 is between 0.2 nm and 1.5 nm. It is presumed that even if the concentration of the additive is changed, the relationship between attenuation and the thickness of the well layer 141 will show the same tendency. In the light emitter 10, if the thickness of the well layer 141 is less than 0.2 nm, it is impractical from a manufacturing or practical point of view.

[0035] Figure 4 This is a graph showing the decay as the concentration of the additive in the light emitter 10 changes. Example 3 is an example where the thickness of the well layer 141 is 0.8 nm. Example 4 is an example where the thickness of the well layer 141 is 1.5 nm. Figure 4 As shown, the higher the concentration of the additive, the lower the attenuation. It can also be seen that the higher the concentration of the additive, the smaller the change in attenuation. It is inferred that even if the thickness of the trap layer 141 is changed, the relationship between attenuation and the additive concentration will show the same tendency. It can be seen that when the additive concentration is less than 4 × 10⁻⁶... 18 cm -3 When the thickness of the well layer 141 is 1.5 nm, the possibility of the attenuation increasing and exceeding the threshold α increases.

[0036] Figure 5 This is a graph showing the luminous intensity (arbitrary units (au)) as the thickness of the trap layer 141 in the luminescent body 10 is varied. Example 5 uses an additive concentration of 4 × 10⁻⁶. 18 cm -3 Example 6 is an example where the concentration of the additive is 1.5 × 10⁻⁶. 19 cm -3 Example 7 is an example where the concentration of the additive is 1×10⁻⁶. 20 cm -3 This is an example of a situation. The threshold β is a value set based on the luminous intensity of a typical luminescent body, which is 5000 in this case. The threshold β is not specifically limited.

[0037] like Figure 5 As shown, the greater the thickness of the well layer 141, the higher the luminescence intensity. It is inferred that the luminescence intensity exhibits the same tendency even when the concentration of the additive is changed. It is known that when the thickness of the well layer 141 is less than 0.2 nm, for example, when the additive concentration is 1 × 10⁻⁶ nm... 20 cm -3 In this case, the probability of the luminescence intensity decreasing and falling below the threshold β increases.

[0038] Figure 6 This is a graph showing the luminescence intensity (arbitrary unit (au)) as the concentration of the additive in the luminescent body 10 changes. Example 8 is an example where the thickness of the well layer 141 is 0.8 nm. Example 9 is an example where the thickness of the well layer 141 is 0.2 nm. Figure 6 As shown, the higher the concentration of the additive, the lower the luminescence intensity. The higher the concentration of the additive, the smaller the change in luminescence intensity. It can be inferred that even if the thickness of the well layer 141 is changed, the luminescence intensity will exhibit the same tendency. It is known that when the concentration of the additive is greater than 1 × 10⁻⁶... 20 cm -3 When, for example, the thickness of the well layer 141 is 0.2 nm, the probability of the luminescence intensity decreasing and falling below the threshold β increases.

[0039] In the above-mentioned light emitter 10, the thickness of the well layer 141 is 0.2 nm or more and less than 1.5 nm, and the concentration of the additives in the barrier layer 142 and the well layer 141 is greater than 4 × 10⁻⁶. 18 cm -3 And it is 1×10 20 cm -3 In this case, the thickness of the well layer 141 and the concentration of additives in the barrier layer 142 and the well layer 141 can be optimized to reduce attenuation while maintaining luminescence intensity. Therefore, the response time can be further shortened and the high-speed response can be further improved.

[0040] In the light emitter 10, the thickness of the well layer 141 is greater than 0.6 nm and less than 1.0 nm. In this case, the attenuation can be further reduced.

[0041] In the light emitter 10, the multiple quantum well structure 14C comprises a first barrier layer and a second barrier layer as barrier layer 142. The second barrier layer is located on the electron incident surface 10a side relative to the first barrier layer, and the first barrier layer is thicker than the second barrier layer. Because the second barrier layer, located relatively shallowly from the electron incident surface 10a, is relatively thin, the well layer 141, sandwiched between the second barrier layer and located on the opposite side of the electron incident surface 10a, is arranged closer to the electron incident surface 10a. Therefore, the light conversion efficiency for electron beams with relatively low accelerating voltages can be improved. Furthermore, because the first barrier layer, located relatively deeply, is relatively thick, the well layer 141, sandwiched between the first barrier layer and located on the opposite side of the electron incident surface 10a, is arranged further away from the electron incident surface 10a. Therefore, the light conversion efficiency can be maintained even with deep penetration of electron beams with relatively high accelerating voltages. Furthermore, since the electron beam extends in a hemispherical shape inside the light emitter 10, the quantum wells densely arranged near the electron incident surface 10a can indeed capture electrons even at higher accelerating voltages. Moreover, by varying the thickness of the barrier layer 142 according to the distance from the electron incident surface 10a, the light conversion efficiency can be improved from a lower accelerating voltage to a higher accelerating voltage, thereby increasing the luminous intensity.

[0042] In the light emitter 10, the well layer 141 and the barrier layer 142 are nitride semiconductor layers, and the additives include silicon. In this case, the well layer 141 and the barrier layer 142 can be set as nitride semiconductor layers, and silicon can be used as an additive thereto.

[0043] Furthermore, in the light emitter 10, the second barrier layer is closest to the electron incident surface 10a among the plurality of barrier layers 142. Additionally, in this case, the second barrier layer is the thinnest among the plurality of barrier layers 142. Therefore, the position of the well layer closest to the electron incident surface 10a is closer than the electron incident surface 10a, which can further improve the light conversion efficiency of electron beams with relatively small accelerating voltages.

[0044] In the light emitter 10, the multiple barrier layers 142 become thicker the further away from the electron incident surface 10a. In this case, appropriate well layer configurations can be achieved according to various accelerating voltages, further improving the light conversion efficiency. In the light emitter, the multiple well layers 141 have the same composition, making the fabrication of multiple quantum well structures easier.

[0045] Figure 7 This is a graph showing the relationship between attenuation and luminescence intensity in the luminescent body 10. The graph displays data for varying the thickness of the trap layer 141 and the concentration of the additives. For example... Figure 7As shown, it can be confirmed that the greater the attenuation in the luminescent body 10, the higher the luminous intensity.

[0046] In this embodiment, incident electrons are converted into light, but this is not a limitation. This embodiment can be any light emitter that converts incident charged particles into light. In the above embodiment, nitride semiconductor refers to a compound containing at least one of Ga, In, and Al as a group III element and N as a predominant group V element. Having light transmittance means, for example, the property of allowing light of the target to pass through at least 50%.

[0047] [Second Implementation] Figure 8 This is a cross-sectional view showing the configuration of the electron beam detector 20 in the second embodiment, showing a cross-section along the thickness direction. For example... Figure 8 As shown, the electron beam detector 20 includes a light emitter 10 according to the first embodiment, an insulating optical component 22, and a photodetector 30. The optical component 22 is an example of a light-transmitting component (light guiding component). The optical component 22 is insulating and is disposed between the light emitter 10 and the photodetector 30, thereby integrating the light emitter 10 and the photodetector 30.

[0048] The back surface 12b of the substrate 12 of the light emitter 10 is optically coupled to the light incident surface 30a of the photodetector 30 via an optical component 22. Specifically, one end face of the optical component 22 is coupled to the light incident surface 30a, and the other end face of the optical component 22 is coupled to the light emitter 10. The optical component 22 can be an optical waveguide such as a fiber optic plate (FOP), or a lens that focuses the light generated in the light emitter 10 onto the light incident surface 30a.

[0049] A light-transmitting adhesive layer AD2 is disposed between the optical component 22 and the photodetector 30, fixing the relative position between the optical component 22 and the photodetector 30. The adhesive layer AD2 mainly comprises, for example, a light-transmitting resin. Additionally, an adhesive layer AD1 is disposed between the back surface 12b of the substrate 12 of the light emitter 10 and the optical component 22. The adhesive layer AD1 comprises a SiN layer ADa disposed on the back surface 12b and a SiO2 layer ADb disposed on the SiN layer ADa. In one example, the back surface 12b and the SiN layer ADa are in contact with each other, and the SiN layer ADa and the SiO2 layer ADb are in contact with each other. The SiO2 layer ADb is fused to the optical component 22. Since both the SiO2 layer ADb and the optical component 22 are silicon oxides, they can be fused together by heating.

[0050] Because the SiO2 layer ADb is formed on the SiN layer ADa using sputtering or similar methods, the coupling force between the SiN layer ADa and the SiO2 layer ADb is extremely high. Similarly, because the SiN layer ADa is also formed on the back surface 12b of the substrate 12 using sputtering or similar methods, the coupling force between the SiN layer ADa and the substrate 12 is also extremely high. Therefore, the substrate 12 and the optical component 22 are firmly bonded together via the adhesive layer AD1. In addition, the SiN layer ADa also functions as an anti-reflection film, suppressing or reducing the reflection of light generated in the multiple quantum well structure 14C on the back surface 12b.

[0051] In the electron beam detector 20 with this structure, the light generated by the incident electrons in the multiple quantum well structure 14C passes sequentially through the adhesive layer AD1, the optical component 22 and the adhesive layer AD2 to reach the light incident surface 30a of the photodetector 30.

[0052] As described above, the light incident surface 30a of the photodetector 30 is optically coupled to the surface opposite to the electron incident surface 10a in the multiple quantum well structure 14C via the substrate 12, adhesive layer AD1, optical component 22, and adhesive layer AD2. That is, the photodetector 30 is optically coupled to the surface opposite to the electron incident surface 10a in the multiple quantum well structure 14C (see reference). Figure 1 The opposite side is shown. The photodetector 30 is sensitive to light emitted by the multiple quantum well structure 14C. The photodetector 30 is, for example, a photoelectron multiplier tube. In this case, the photodetector 30 includes a vacuum container 31. The vacuum container 31 is composed of a metal side tube 31a, a light incident window 31b that closes the opening at the top of the side tube 31a, and a base plate 31c that closes the opening at the bottom of the side tube 31a. Inside the vacuum container 31, a photocathode 32 formed on the inner surface of the light incident window 31b and an electrode portion 33 including an electron multiplier and an anode are disposed. The electron multiplier includes, for example, a microchannel plate or a grid-type secondary emitter.

[0053] The light incident surface 30a is the outer surface of the light incident window 31b. Light incident on the light incident surface 30a passes through the light incident window 31b and enters the photocathode 32. The photocathode 32 performs photoelectric conversion according to the incident light, releasing the generated photoelectrons into the internal space of the vacuum container 31. These photoelectrons are multiplied by the electron multiplier of the electrode section 33. The multiplied electrons are collected at the anode of the electrode section 33. The electrons collected at the anode of the electrode section 33 are extracted to the outside of the photodetector 30 via any one of the multiple pins penetrating the base plate 31c. The potential of the metal side tube 31a is 0V, and the photocathode 32 is electrically connected to the side tube 31a.

[0054] In addition, even in the electron beam detector 20, the presence of the light emitter 10 further enhances the high-speed response. Furthermore, this embodiment is an electron beam detector 20 for incident electrons, but it is not limited to this; any charged particle detector for incident charged particles is acceptable.

[0055] [Third Implementation] Electron beam detector 20 of the second embodiment (see reference) Figure 8 It can be used in electron microscopes, such as scanning electron microscopes (SEM). Figure 9 This is a schematic diagram showing the configuration of the length measuring SEM 40 according to the third embodiment. The length measuring SEM 40 includes: an SEM 41 that acquires an image of the object to be inspected; a control unit 42 that performs overall control; a storage unit 43 that stores the acquired images, etc., in a disk or semiconductor memory, etc.; and an arithmetic unit 44 that performs calculations according to a program.

[0056] The SEM 41 includes: a movable stage 46 on which a sample wafer 45 is mounted; an electron source 47 that irradiates the sample wafer 45 with an electron beam EB1; and multiple (three are shown in the figure) electron beam detectors 20 that detect electrons (secondary electrons and reflected electrons) generated from the sample wafer 45. The configuration of the electron beam detectors 20 is the same as in the second embodiment. The SEM 41 includes an electron lens (not shown) that focuses the electron beam EB1 onto the sample wafer 45, a deflector (not shown) for scanning the electron beam EB1 on the sample wafer 45, and an image generation unit 48 that digitally converts the signals from each electron beam detector 20 to generate a digital image.

[0057] The length measuring SEM 40 has a vacuum chamber 50 whose internal space is set to a vacuum (reduced pressure) atmosphere. Inside the vacuum chamber 50 are arranged a movable stage 46, an electron source 47, at least one light emitter 10 from the electron beam detector 20, an electron lens, and a deflector. The image generation unit 48 and each electron beam detector 20 are electrically connected to each other via wiring. The image generation unit 48, control unit 42, storage unit 43, and arithmetic unit 44 are electrically connected to each other via a data bus 49.

[0058] When electron beam EB1 is irradiated onto the sample wafer 45 while scanning the surface of the sample wafer 45, electrons are emitted from the surface of the sample wafer 45 and guided to the electron beam detector 20 as electron beam EB2. The electron beam detector 20 converts electron beam EB2 into an electrical signal and outputs an electrical signal according to the current of electron beam EB2. By synchronizing and establishing a correspondence between the scanning position of electron beam EB1 and the output of electron beam detector 20, an image of the sample wafer 45 can be obtained.

[0059] The control unit 42 has the functions of controlling the transport of the sample wafer 45, controlling the movable stage 46, controlling the irradiation position of the electron beam EB1, and controlling the scanning of the electron beam EB1. The storage unit 43 has an area for storing the acquired image data and an area for storing imaging conditions (e.g., accelerating voltage). The arithmetic unit 44 has the function of calculating the dimensions of the structure (such as the width of the slot) based on the brightness (contrast) in the image data. Furthermore, the control unit 42 and the arithmetic unit 44 can be configured as hardware designed to implement each function, or they can be configured to be executed using a general-purpose computing device (such as a CPU (Central Processing Unit) or GPU (Graphics Processing Unit) installed as software.

[0060] In addition, even in the length measurement SEM40, the presence of the luminescent element 10 further enhances the high-speed response capability.

[0061] [Fourth Implementation] Electron beam detector 20 of the second embodiment (see reference) Figure 8 It can be used in quality analysis devices. Figure 10 This is a diagram that schematically illustrates the configuration of the quality analysis device 60 according to the fourth embodiment. (See diagram below.) Figure 10 As shown, the quality analysis apparatus 60 includes: an electron beam detector 20 (see reference). Figure 8 The configuration is the same as that in the second embodiment; a vacuum chamber (chamber) 61 in which at least the light emitter 10 (Figure) of the electron beam detector 20 is disposed in an internal space with a vacuum (reduced pressure) atmosphere; a separation section AZ in which ions generated from the sample in the vacuum chamber 61 are spatially or temporally separated according to their mass; and electron conversion sections, namely secondary emitters DY1 and DY2, which are irradiated with ions separated by the separation section AZ.

[0062] In the mass analysis apparatus 60, the electron-guided light emitter 10, which emits light from the secondary emitters DY1 and DY2 based on the incident ions onto the secondary emitters DY1 and DY2, performs mass analysis of the sample based on the output of the electron beam detector 20. Specifically, in the mass analysis apparatus 60, when a positive ion located in the separation section AZ imparts an appropriate potential to the aperture AP and imparts a negative potential to the secondary emitter DY1 located on the opposite side of the separation section AZ relative to the aperture AP, the secondary emitter DY1 collides with the aperture AP, and electrons are emitted from the surface of the secondary emitter DY1 along with the collision, serving as the electron beam e3 guiding the electron beam detector 20. When a positive potential is imparted to the secondary emitter DY2 and a negative ion is drawn from the separation section AZ, the negative ion collides with the secondary emitter DY2, and electrons are emitted from the surface of the secondary emitter DY2 along with the collision, serving as the electron beam e3 guiding the electron beam detector 20. An electrical signal is output from the electron beam detector 20 based on the incident electron beam e3.

[0063] For example, if the separation section AZ is designed as a flight tube, the transit time of ions inside the flight tube varies depending on their mass, resulting in different arrival times towards the secondary emitters DY1 and DY2. Furthermore, if the separation section AZ is designed to change the flight trajectory of each ion according to its mass using a magnetic field, then by making the magnetic flux density of the separation section AZ variable, the ions passing through the aperture AP will vary depending on their mass. Therefore, the mass of each ion can be determined by monitoring the time variation of the electrical signal output from the electron beam detector 20.

[0064] Therefore, even in the mass analysis device 60, the presence of the light emitter 10 further enhances the high-speed response capability.

[0065] [Variation Example] The present invention is not limited to the above-described embodiments, and various other modifications are also possible.

[0066] In the above embodiments, the composition of the well layer 141 and barrier layer 142 constituting the multiple quantum well structure 14C is not limited to the examples described above. Although the above examples illustrate the use of GaN layers for the first buffer layer 14A and the second buffer layer 14B, other compositions may be used as long as the semiconductor is a nitride semiconductor containing at least one of Group III elements (In, Al, and Ga), containing N as the main Group V element, and having light transmittance to the emission wavelength of the multiple quantum well structure 14C.

[0067] In the above embodiment, although an example is shown where Si is doped into the well layer 141 and barrier layer 142 of the multiple quantum well structure 14C, it is not limited to this, and other impurities (e.g., Mg) may also be doped. In the above embodiment, the well layer 141 and barrier layer 142 of the multiple quantum well structure 14C may be made of Inx Al y Ga 1-x-y N(0≦x≦1, 0≦y≦1, 0≦x+y≦1) can be used. Therefore, in addition to the InGaN / GaN combination mentioned above, combinations such as InGaN / AlGaN, InGaN / InGaN, and GaN / AlGaN can also be used. Alternatively, the well layer 141 and the barrier layer 142 can also be made of semiconductors other than nitride semiconductors.

[0068] In the above embodiment, although the number of well layer 141 and barrier layer 142 is set to 9, the number of well layer 141 and barrier layer 142 can be any number of 2 or more. In the above embodiment, the photodetector 30 is not limited to a photoelectron multiplier tube, but can also be an avalanche photodiode, for example. In addition, the optical component 22 is not limited to a linear shape, but can also be a curved shape, and its size can also be appropriately changed.

[0069] In the above embodiment, although the multiple quantum well structure 14C is a structure in which the first barrier layer on the substrate 12 side is thicker than the second barrier layer on the electron incident surface 10a side (so-called tilted structure), it is not particularly limited to this, and the thicknesses of the multiple barrier layers 142 can be the same or different from each other.

[0070] The values ​​mentioned above may include errors in measurement, manufacturing, and design. The aforementioned "4×10" 18 cm -3 "Not only does it contain exactly 4×10" 18 cm -3 It also contains approximately 4×10 18 cm -3 The aforementioned "1×10" 20 cm -3 "Not only does it contain exactly 1×10" 20 cm -3 It also contains approximately 1×10 20 cm -3 The "0.6nm" mentioned above includes not only exactly 0.6nm, but also approximately 0.6nm. Similarly, the "1.0nm" mentioned above includes not only exactly 1.0nm, but also approximately 1.0nm. The "measurement," "manufacturing," and "design" mentioned above can be implemented according to known standards and specifications such as JIS (Japanese Industrial Standard). The terms "equal" and "identical" mentioned above include not only cases of complete equality and exact sameness, but also cases of approximately equality and approximately identicalness. Symbol Explanation

[0071] 10…Light emitter; 10a…Electron incident surface (charged particle incident surface); 12…Substrate; 12a…Main surface; 12b…Back surface; 14…Nitride semiconductor layer; 14A…First buffer layer; 14B…Second buffer layer; 14C…Multiple quantum well structure; 18…Conductive layer; 20…Electron beam detector; 22…Optical component; 30…Photodetector; 30a…Light incident surface; 31…Vacuum container; 32…Photocathode; 33…Electrode section; 40…Length measuring SEM; 41…Scanning electron microscope (SEM); 42…Control section; 43…Storage section; 44…Computation section; 45…Sample wafer; 46…Movable stage; 47…Electron source; 48…Image generation section; 50, 61…Vacuum chamber; 141…Trap layer; 142, 143…Block layer; AZ…Separation section; DY1, DY2…Secondary emitter (electron conversion section).

Claims

1. A luminescent body, wherein, It is a light-emitting body that converts incident charged particles into light. It possesses: a multiple quantum well structure that emits light upon the incidence of the charged particles. The thickness of the well layer constituting the multiple quantum well structure is greater than 0.2 nm and less than 1.5 nm. The concentration of the additives added to the barrier layer and the well layer constituting the multiple quantum well structure is greater than 4 × 10⁻⁶. 18 cm -3 And it is 1×10 20 cm -3 the following.

2. The light emitter as described in claim 1, wherein, The thickness of the well layer is greater than 0.6 nm and less than 1.0 nm.

3. The light-emitting body as described in claim 1 or 2, wherein, The multiple quantum well structure comprises a first barrier layer and a second barrier layer as the barrier layers. The second barrier layer is located relative to the first barrier layer on the charged particle incident surface side of the multiple quantum well structure. The first barrier layer is thicker than the second barrier layer.

4. The light-emitting body as described in claim 1 or 2, wherein, The well layer and the barrier layer are nitride semiconductor layers. The additive contains silicon.

5. A charged particle detector, wherein, have: The light-emitting body according to claim 1 or 2; and A photodetector, optically coupled to a surface in the multiple quantum well structure opposite to the incident surface of the charged particle, is sensitive to the light emitted by the multiple quantum well structure.

6. An electron microscope, wherein, have: The light-emitting body according to claim 1 or 2; A photodetector, optically coupled to a surface in the multiple quantum well structure opposite to the incident surface of the charged particle, is sensitive to the light emitted by the multiple quantum well structure; and A chamber, which contains at least the light-emitting element. An electron beam is irradiated onto the surface of a sample disposed within the chamber, guiding electrons from the sample to the light emitter. An image of the sample is obtained by establishing a correspondence between the irradiation position of the electron beam in the sample and the output of the photodetector.

7. A quality analysis apparatus, wherein, have: The light-emitting body according to claim 1 or 2; A photodetector, optically coupled to a surface in the multiple quantum well structure opposite to the incident surface of the charged particle, is sensitive to the light emitted by the multiple quantum well structure. A chamber, which is at least provided with the light-emitting element inside; A separation section that spatially or temporally separates ions generated from the sample within the chamber based on their mass; and The electron conversion section is irradiated with ions separated by the separation section. Electrons emitted from the electron conversion unit according to the incident ions onto the electron conversion unit are guided to the light emitter, and the mass analysis of the sample is performed based on the output of the photodetector.

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