Radiation detection device

Abstract

The invention realizes a radiation detection device with high reliability. This radiation detection device is provided with: a transistor in which an oxide semiconductor layer is used as a channel; a photoelectric conversion layer connected to the transistor; a wavelength conversion layer that faces the photoelectric conversion layer and emits visible light on the basis of the absorbed radiation; and an oxide layer in contact with the oxide semiconductor layer between the transistor and the photoelectric conversion layer and having a film thickness of 50 nm or less. The transistor may also include a gate electrode layer opposed to the oxide semiconductor layer and a gate insulating layer between the oxide semiconductor layer and the gate electrode layer, and the oxide semiconductor layer may also be closer to the photoelectric conversion layer than the gate electrode layer.

Description

Technical Field

[0001] One embodiment of the present invention relates to a radiation detection device. In particular, one embodiment of the present invention relates to a radiation detection device including a semiconductor device using an oxide semiconductor as a channel. Background Art

[0002] In recent years, the development of semiconductor devices using oxide semiconductors for channels instead of amorphous silicon, low-temperature polycrystalline silicon, and single-crystal silicon has been continuously developed (e.g., Patent Documents 1 to 6). Semiconductor devices using oxide semiconductors for channels can be formed with a simple structure and by a low-temperature process, similar to semiconductor devices using amorphous silicon for channels. It is known that semiconductor devices using oxide semiconductors for channels have higher mobility than semiconductor devices using amorphous silicon for channels.

[0003] In order to make a semiconductor device in which an oxide semiconductor is used as a channel operate stably, it is important to reduce oxygen vacancies formed in the oxide semiconductor layer by supplying oxygen to the oxide semiconductor layer in the manufacturing process of the semiconductor device. As one method of supplying oxygen to the oxide semiconductor layer, for example, a technique of forming an insulating layer covering the oxide semiconductor layer under the condition that the insulating layer contains more oxygen is disclosed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2021-141338

[0007] Patent Document 2: Japanese Patent Application Publication No. 2014-099601

[0008] Patent Document 3: Japanese Patent Application Publication No. 2021-153196

[0009] Patent Document 4: Japanese Patent Application Publication No. 2018-006730

[0010] Patent Document 5: Japanese Patent Application Publication No. 2016-184771

[0011] Patent Document 6: Japanese Patent Application Publication No. 2021-108405 Summary of the invention

[0012] Problems to be solved by the invention

[0013] However, an insulating layer formed under conditions containing more oxygen will contain many defects. Under the influence of these defects, the characteristics of the semiconductor device in the reliability test may change, which is believed to be caused by the capture of holes in the defects. If a semiconductor device with hole traps is used for a detection device for radiation, the characteristics of the semiconductor device may change due to the capture of holes generated by the radiation. It is required to suppress such characteristic changes.

[0014] One of the embodiments of the present invention aims to realize a highly reliable radiation detection device.

[0015] Means for solving problems

[0016] A radiation detection device according to one embodiment of the present invention comprises: a transistor in which an oxide semiconductor layer is used as a channel; a photoelectric conversion layer connected to the transistor; a wavelength conversion layer opposite to the photoelectric conversion layer and emitting visible light based on absorbed radiation; and an oxide layer between the transistor and the photoelectric conversion layer, in contact with the oxide semiconductor layer and having a film thickness of less than 50 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a cross-sectional view schematically showing a radiation detection device according to an embodiment of the present invention.

[0018] Figure 2 This is a circuit diagram schematically showing a radiation detection device according to an embodiment of the present invention.

[0019] Figure 3 This is a diagram showing the results of a reliability test for visible light of a transistor used in a radiation detection device according to an embodiment of the present invention.

[0020] Figure 4 This is a diagram showing the results of a reliability test on a transistor used in a radiation detection device according to an embodiment of the present invention with respect to radiation.

[0021] Figure 5 This is a diagram showing the results of a reliability test on a transistor used in a radiation detection device according to an embodiment of the present invention with respect to radiation.

[0022] Figure 6 This is a diagram showing the results of a reliability test for visible light of a transistor used in a radiation detection device according to an embodiment of the present invention.

[0023] Figure 7 This is a diagram showing the results of a reliability test for visible light of a transistor used in a radiation detection device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] Hereinafter, various embodiments of the present invention will be described with reference to the accompanying drawings. The following disclosure is only an example. The configuration that can be easily conceived by those skilled in the art by appropriately changing the configuration of the embodiment while maintaining the gist of the invention is of course included in the scope of the present invention. With respect to the accompanying drawings, in order to make the description clearer, the width, thickness, shape, etc. of each part are sometimes schematically indicated compared to the actual method. However, the shape shown in the figure is only an example and does not limit the interpretation of the present invention. In this specification and each figure, the same figure mark is marked for the same configuration as that described in the accompanying drawings that have appeared, and the detailed description is sometimes appropriately omitted.

[0025] In each embodiment of the present invention, the direction from the substrate toward the oxide semiconductor layer is referred to as up or above. Conversely, the direction from the oxide semiconductor layer toward the substrate is referred to as down or below. Thus, for ease of explanation, the above or below phrases are used for explanation, but, for example, the up-and-down relationship between the substrate and the oxide semiconductor layer may be configured in a different direction than that shown in the figure. In the following description, for example, the expression "oxide semiconductor layer on the substrate" is only used to illustrate the up-and-down relationship between the substrate and the oxide semiconductor layer as described above, and other components may be configured between the substrate and the oxide semiconductor layer. Above or below refers to the stacking order in a structure having a plurality of layers stacked, and in the case of a first component described as being above a transistor, it may also be a positional relationship in which the transistor and the first component do not overlap when viewed from above. On the other hand, in the case of a first component described as being vertically above a transistor, it refers to a positional relationship in which the transistor and the first component overlap when viewed from above.

[0026] In this specification, unless otherwise specified, expressions such as “α includes A, B, or C”, “α includes any one of A, B, and C”, and “α includes one selected from the group consisting of A, B, and C” do not exclude the case where α includes a plurality of combinations of A to C. In addition, the above expressions do not exclude the case where α includes other elements.

[0027] It should be noted that the following embodiments can be combined with each other as long as no technical contradiction occurs.

[0028] [1. First embodiment]

[0029] Reference Figure 1 and Figure 2 A radiation detection device 10 according to an embodiment of the present invention will be described.

[0030] [1-1. Configuration of Radiation Detection Device 10]

[0031] use Figure 1 and Figure 2 The configuration of a radiation detection device 10 according to an embodiment of the present invention will be described. Figure 1 It is a cross-sectional view schematically showing a radiation detection device according to an embodiment of the present invention. Figure 2 This is a circuit diagram schematically showing a radiation detection device according to an embodiment of the present invention.

[0032] like Figure 1 As shown, the radiation detection device 10 is disposed on a substrate 100. The radiation detection device 10 includes a transistor 20, a photoelectric conversion layer 300, a wavelength conversion layer 400, and an oxide layer 150. In addition to the above-mentioned components, the radiation detection device 10 also includes an insulating layer 160, a light shielding layer 210, a connecting wiring 220, an insulating layer 230, a lower electrode 310, an upper electrode 320, insulating layers 330, 340, and wirings 350, 360.

[0033] The transistor 20 includes a gate electrode 105, gate insulating layers 110, 120, a metal oxide layer 130, an oxide semiconductor layer 140, a source electrode 201, and a drain electrode 203. The transistor 20 is a transistor in which the oxide semiconductor layer 140 is used as a channel. Depending on the polarity of the transistor, the circuit configuration, and the potential of each node, the source electrode and the drain electrode of the aforementioned transistor are sometimes interchanged. In the case where the source electrode 201 and the drain electrode 203 are not particularly distinguished, they are sometimes collectively referred to as source-drain electrodes 200. In this embodiment, a bottom-gate transistor in which the gate electrode 105 is provided below the oxide semiconductor layer 140 as the radiation detection device 10 is described.

[0034] In this embodiment, a bottom-gate transistor in which the oxide semiconductor layer 140 is closer to the photoelectric conversion layer 300 than the gate electrode 105 is illustrated as the radiation detection device 10, but the radiation detection device 10 is not limited to the bottom-gate transistor. For example, the radiation detection device 10 may be a dual-gate transistor in which the gate electrodes are provided both above and below the oxide semiconductor layer 140.

[0035] The gate electrode 105 is provided on the substrate 100. The gate electrode 105 is opposite to the oxide semiconductor layer 140. The gate insulating layers 110 and 120 are provided between the gate electrode 105 and the oxide semiconductor layer 140. The gate insulating layers 110 and 120 are stacked structures. The metal oxide layer 130 is provided on the gate insulating layer 120. The oxide semiconductor layer 140 is provided on the metal oxide layer 130. The source electrode 201 and the drain electrode 203 are provided on the oxide semiconductor layer 140. The source electrode 201 and the drain electrode 203 are in contact with the oxide semiconductor layer 140 from above the oxide semiconductor layer 140.

[0036] The oxide layer 150 and the insulating layer 160 are provided on the oxide semiconductor layer 140, the source electrode 201, and the drain electrode 203. The oxide layer 150 and the insulating layer 160 are stacked structures. The insulating layer 160 is provided on the oxide layer 150. The oxide layer 150 and the insulating layer 160 cover the source electrode 201 and the drain electrode 203. The oxide layer 150 is in contact with the oxide semiconductor layer 140. The oxide layer 150 can be provided between the transistor 20 and the photoelectric conversion layer 300.

[0037] The oxide semiconductor layer 140 is light-transmissive and has a polycrystalline structure including a plurality of crystal grains. The oxide semiconductor layer 140 having a polycrystalline structure can be formed by using the Poly-OS (Poly-crystalline Oxide Semiconductor) technology, and the details will be described later. The composition of the oxide semiconductor layer 140 is described below, and the oxide semiconductor having a polycrystalline structure is sometimes referred to as Poly-OS.

[0038] The crystal grain size of the crystal grains contained in the Poly-OS is, for example, 0.1 μm or more, 0.3 μm or more, or 0.5 μm or more. The crystal grain size of the crystal grains can be obtained by, for example, cross-sectional SEM observation, cross-sectional TEM observation, or electron backscattered diffraction (EBSD) method.

[0039] As described above, since the crystal grain size of the crystal grains included in the Poly-OS is not less than 0.1 μm, there is a region including only one crystal grain along the film thickness direction in the oxide semiconductor layer 140 having a film thickness of not less than 10 nm and not more than 30 nm.

[0040] The film thickness of the gate insulating layer 110 is, for example, 50 nm to 500 nm, 50 nm to 400 nm, 50 nm to 300 nm, 50 nm to 150 nm, or 50 nm to 100 nm. The film thickness of the gate insulating layer 120 is, for example, 10 nm to 200 nm, or 10 nm to 100 nm. The total film thickness of the gate insulating layers 110 and 120 is, for example, 100 nm to 700 nm, 100 nm to 500 nm, 100 nm to 400 nm, 100 nm to 250 nm, 100 nm to 200 nm, or 100 nm to 150 nm.

[0041] The thickness of the metal oxide layer 130 is, for example, not less than 1 nm and not more than 20 nm, or not less than 1 nm and not more than 10 nm. In the present embodiment, aluminum oxide is used as the metal oxide layer 130. Aluminum oxide has a high barrier property against gases such as oxygen and hydrogen. Barrier property refers to the function of inhibiting gases such as oxygen and hydrogen from penetrating aluminum oxide. That is, even if gases such as oxygen and hydrogen are released from a layer disposed under the aluminum oxide film, the gas will not move to a layer disposed above the aluminum oxide film. Alternatively, even if gases such as oxygen and hydrogen are released from a layer disposed above the aluminum oxide film, the gas will not move to a layer disposed under the aluminum oxide film.

[0042] The oxide semiconductor layer 140 has a thickness of 10 nm to 50 nm, 10 nm to 40 nm, or 10 nm to 30 nm. The oxide layer 150 has a thickness of 50 nm to 300 nm, 60 nm to 200 nm, or 70 nm to 150 nm.

[0043] The thickness of oxide layer 150 is, for example, 100 nm or less, 50 nm or less, 30 nm or less, 20 nm or less, or 10 nm or less. By setting the thickness of oxide layer 150 within the above range, the reliability of transistor 20 against visible light and radiation is improved as described later.

[0044] The film thickness of the insulating layer 160 is, for example, not less than 50 nm and not more than 500 nm, not less than 50 nm and not more than 400 nm, not less than 50 nm and not more than 300 nm, or not less than 50 nm and not more than 200 nm.

[0045] The light shielding layer 210 is provided on the insulating layer 160. The light shielding layer 210 is provided in a region overlapping with the oxide semiconductor layer 140 when viewed from above. When viewed from above, the light shielding layer 210 is provided in a manner to cover at least the oxide semiconductor layer 140 exposed from the source-drain electrode 200. When the light shielding layer 210 is formed of a conductive material, the same voltage as that of the gate electrode 105 may be supplied to the light shielding layer 210. In this case, the transistor 20 functions as a dual-gate transistor.

[0046] The oxide layer 150 and the insulating layer 160 are provided with an opening 161. The opening 161 reaches the source electrode 201. The connection wiring 220 is provided on the insulating layer 160 and inside the opening 161. The connection wiring 220 is in contact with the source electrode 201 at the bottom of the opening 161.

[0047] An insulating layer 230 is provided on the insulating layer 160, the light shielding layer 210, and the connection wiring 220. The insulating layer 230 covers the pattern end of the light shielding layer 210 and the pattern end of the connection wiring 220. The insulating layer 230 is used to alleviate the step difference formed by the light shielding layer 210 and the connection wiring 220. The insulating layer 230 can be called a planarization layer. As the insulating layer 230, an organic insulating layer can be used. An opening 231 is provided in the insulating layer 230. The opening 231 reaches the connection wiring 220.

[0048] A lower electrode 310 is provided on the insulating layer 230 and inside the opening 231. The lower electrode 310 is in contact with the connection wiring 220 at the bottom of the opening 231. A photoelectric conversion layer 300 and an upper electrode 320 are provided on the lower electrode 310. That is, the photoelectric conversion layer 300 is connected to the transistor 20 via the lower electrode 310 and the connection wiring 220. The photoelectric conversion layer 300 includes an N-type semiconductor layer, a P-type semiconductor layer, and an intrinsic semiconductor layer. The intrinsic semiconductor layer is provided between the N-type semiconductor layer and the P-type semiconductor layer. One of the N-type semiconductor layer and the P-type semiconductor layer is in contact with the lower electrode 310, and the other is in contact with the upper electrode 320.

[0049] The photoelectric conversion layer 300 has the function of converting light energy into electric energy. When light energy is absorbed by the intrinsic semiconductor layer of the photoelectric conversion layer 300, the semiconductor is excited by light to generate pairs of electrons and holes. The generated electrons and holes flow to the lower electrode 310 and the upper electrode 320 via the N-type semiconductor layer and the P-type semiconductor layer. By detecting the current generated by the electrons and holes generated by light excitation, the intensity of light irradiated to the photoelectric conversion layer 300 can be detected.

[0050] An insulating layer 330 is provided on the upper electrode 320. An opening 331 is provided in the insulating layer 330. The opening 331 reaches the upper electrode 320. An insulating layer 340 is provided on the insulating layer 330. An opening 341 is provided in the insulating layer 340. When viewed from above, the opening 341 is larger than the opening 331. The opening 341 reaches the upper electrode 320 and a part of the insulating layer 330. As the insulating layer 330, an inorganic insulating layer can be used. As the insulating layer 340, an organic insulating layer can be used. The insulating layer 330 has a shape reflecting the step difference formed by the lower electrode 310, the photoelectric conversion layer 300 and the upper electrode 320. On the other hand, the insulating layer 340 mitigates the step difference. That is, the insulating layer 340 is a planarization layer.

[0051] Wiring 360 is provided on insulating layer 340 in a region not overlapping photoelectric conversion layer 300 in a plan view. Wiring 350 is provided on insulating layer 340, on wiring 360, and inside opening 341. Wiring 350 is in contact with upper electrode 320 at the bottom of opening 341.

[0052] In order to make the visible light emitted from the wavelength conversion layer 400 efficiently reach the photoelectric conversion layer 300, a transparent conductive layer can be used as the upper electrode 320 and the wiring 350, and the details will be described later. On the other hand, the wiring 360 is an opaque metal layer. The resistance of the metal layer used as the wiring 360 is lower than the resistance of the transparent conductive layer used as the wiring 350. However, as the wiring 360, a transparent conductive layer can also be used.

[0053] The wavelength conversion layer 400 is disposed above the wiring 350 in a manner opposite to the photoelectric conversion layer 300. The wavelength conversion layer 400 may be bonded to the wiring 350 and the insulating layer 340 by an adhesive layer, or the positional relationship with the wiring 350 and the insulating layer 340 may be fixed by other fixing members. The wavelength conversion layer 400 has a function of converting radiation into visible light. For example, the wavelength conversion layer 400 includes a phosphor that absorbs X-rays, α-rays, or γ-rays and emits visible light. The wavelength conversion layer 400 can be called a scintillator.

[0054] When radiation enters the wavelength conversion layer 400 from above, the radiation is converted into visible light by the wavelength conversion layer 400. The converted visible light enters the photoelectric conversion layer 300, whereby the light energy is converted into electric energy, and the converted electric energy is detected as current. Since there is a correlation between the intensity of the radiation entering the wavelength conversion layer 400 and the detected current, the intensity of the radiation can be evaluated based on the magnitude of the current.

[0055] like Figure 2 As shown, pixels 30 are arranged in a matrix in the radiation detection device 10. The pixel 30 includes a transistor 20 and a photoelectric conversion layer 300. The gate electrode of the transistor 20 is connected to the gate control line 109. The source electrode 201 of the transistor 20 is connected to the cathode of the photoelectric conversion layer 300. The anode of the photoelectric conversion layer 300 is connected to the wiring 309. The drain electrode 203 of the transistor 20 is connected to the wiring 209. The wiring 209 is connected to the charge amplifier circuit 500.

[0056] As described above, the radiation incident on the wavelength conversion layer 400 is converted into visible light, and the visible light is converted into electric energy by the photoelectric conversion layer 300. Here, by supplying a bias voltage to the wiring 309 connected to the pixel 30 for detecting radiation, the gate control line 109 connected to the pixel 30 is controlled to be in an on state, thereby detecting the electric energy as a current flowing in the transistor 20. The current flowing in the transistor 20 is supplied to the charge amplifier circuit 500 via the wiring 209. And, the charge amplifier circuit 500 converts the charge signal into a voltage signal and outputs the voltage signal to the outside. Through the above-mentioned operation, the intensity of the radiation irradiated to the pixel 30 can be evaluated.

[0057] like Figure 1 As shown, ideally, all radiation incident from above is absorbed by the wavelength conversion layer 400, but in reality, a portion of the radiation passes through the wavelength conversion layer 400. In addition, ideally, the radiation that passes through the wavelength conversion layer 400 is blocked by the light shielding layer 210, but in reality, the radiation bypasses the light shielding layer 210 due to reflection from other components and reaches the oxide semiconductor layer 140. When radiation is incident on the oxide semiconductor layer 140, electron and hole pairs are generated in the oxide semiconductor layer 140. Since a hole trap is formed in the oxide layer 150 in contact with the oxide semiconductor layer 140, the generated holes are captured in the oxide layer 150. Under its influence, a problem that the electrical characteristics of the transistor 20 are shifted in the negative direction sometimes occurs.

[0058] [1-2. Materials of Components of Radiation Detection Device 10]

[0059] As the substrate 100, a glass substrate, a quartz substrate, a sapphire substrate, or other light-transmitting rigid substrate can be used. When the substrate 100 needs to be flexible, a substrate containing resin such as a polyimide substrate, an acrylic substrate, a siloxane-based substrate, or a fluororesin substrate can be used as the substrate 100. When a substrate containing resin is used as the substrate 100, impurities may be introduced into the above-mentioned resin in order to improve the heat resistance of the substrate 100. As the substrate 100, a semiconductor substrate such as a silicon substrate, a silicon carbide substrate, or a compound semiconductor substrate, or a conductive substrate such as a stainless steel substrate, which is not light-transmitting, can also be used.

[0060] As the gate electrode 105, the source-drain electrode 200, the light shielding layer 210, the connecting wiring 220, the lower electrode 310 and the wiring 360, common metal materials can be used. For example, as the above-mentioned components, for example, aluminum (Al), titanium (Ti), chromium (Cr), cobalt (Co), nickel (Ni), molybdenum (Mo), hafnium (Hf), tantalum (Ta), tungsten (W), bismuth (Bi), silver (Ag), copper (Cu) and their alloys or compounds can be used. As the above-mentioned electrodes and wirings, the above-mentioned materials can be used in a single layer form or in a stacked layer. In the case where the light shielding layer 210 is not required to have conductivity, a black resin can also be used as the light shielding layer 210.

[0061] A transparent conductive layer may be used as the upper electrode 320 and the wiring 350. A mixture of indium oxide and tin oxide (ITO) and a mixture of indium oxide and zinc oxide (IZO) may be used as the transparent conductive layer. Materials other than the above may also be used as the transparent conductive layer.

[0062] A common insulating material is used as the gate insulating layer 110, 120, the oxide layer 150, and the insulating layer 160, 330. For example, silicon oxide (SiO x ), silicon oxide nitride (SiO x N y ), aluminum oxide (AlO x ), aluminum oxide nitride (AlO x N y ) or other oxygen-containing inorganic insulating layers. As the gate insulating layer 110 and the insulating layer 160, silicon nitride (SiN x ), silicon oxide nitride (SiN x O y ), aluminum nitride (AlN x ), aluminum nitride (AlN x O y ) or other nitrogen-containing inorganic insulating layers. However, as the gate insulating layer 110 and the insulating layer 160, the above-mentioned oxygen-containing inorganic insulating layers may also be used. As the gate insulating layer 120 and the oxide layer 150, the above-mentioned nitrogen-containing inorganic insulating layers may also be used.

[0063] As the oxide layer 150, an insulating layer having a function of releasing oxygen by heat treatment is used. That is, as the oxide layer 150, an oxide insulating layer containing an excessive amount of oxygen is used. The temperature of the heat treatment for releasing oxygen from the oxide layer 150 is, for example, 600°C or less, 500°C or less, 450°C or less, or 400°C or less. That is, the oxide layer 150 releases oxygen at the heat treatment temperature performed in the manufacturing process of the transistor 20 when a glass substrate is used as the substrate 100, for example.

[0064] The oxide layer 150 is a layer having different film qualities depending on the film thickness direction, and the details will be described later. Specifically, the oxide layer 150 near the oxide semiconductor layer 140 has a smaller amount of hole traps than the oxide layer 150 outside of the oxide layer 140. For ease of explanation, the region near the oxide semiconductor layer 140 in the oxide layer 150 is sometimes referred to as the first region and the region outside of the oxide layer 150 is sometimes referred to as the second region. In this case, the hole traps of the oxide layer 150 formed in the first region can be less than the hole traps of the oxide layer 150 formed in the second region. Similarly, the first region of the oxide layer 150 can be in contact with the oxide semiconductor layer 140. The first region is only the region near the oxide semiconductor layer 140. That is, the first region is thinner than the second region.

[0065] As the gate insulating layer 120, an insulating layer with few defects is used. For example, when the composition ratio of oxygen in the gate insulating layer 120 is compared with the composition ratio of oxygen in an insulating layer having the same composition as the gate insulating layer 120 (hereinafter referred to as "another insulating layer"), the composition ratio of oxygen in the gate insulating layer 120 is closer to the stoichiometric ratio with respect to the insulating layer than the composition ratio of oxygen in the other insulating layer. Specifically, silicon oxide (SiO x ), the oxygen composition ratio of silicon oxide used as the gate insulating layer 120 is closer to the stoichiometric ratio of silicon oxide than the oxygen composition ratio of silicon oxide used as the oxide layer 150. For example, as the gate insulating layer 120, a layer in which no defects are observed when evaluated by an electron spin resonance method (ESR) may be used.

[0066] The above SiO x N y and AlO x N y It is a silicon compound or aluminum compound containing nitrogen (N) at a ratio (x>y) less than oxygen (O). x O y and AlN x O y These are silicon compounds and aluminum compounds containing oxygen at a ratio smaller than that of nitrogen (x>y).

[0067] An organic insulating layer can be used as the insulating layers 230 and 340. For example, a polyimide resin, an acrylic resin, an epoxy resin, a silicone resin, a fluorine resin, or a siloxane resin can be used as the organic insulating layer.

[0068] As the metal oxide layer 130, a metal oxide containing aluminum as a main component is used. For example, aluminum oxide (AlO x ), aluminum oxide nitride (AlO x N y ) or other inorganic insulating layers. “Metal oxide layer 130 mainly composed of aluminum” means that the ratio of aluminum contained in the metal oxide layer 130 is greater than 1% of the entire metal oxide layer. The ratio of aluminum contained in the metal oxide layer 130 may also be greater than 5% and less than 70%, greater than 10% and less than 60%, or greater than 30% and less than 50% of the entire metal oxide layer. The above ratio may be a mass ratio or a weight ratio.

[0069] A metal oxide having semiconductor characteristics can be used as the oxide semiconductor layer 140. The oxide semiconductor layer 140 has a polycrystalline structure. The oxide semiconductor layer 140 having a polycrystalline structure can be manufactured using the Poly-OS technology.

[0070] For example, as the oxide semiconductor layer 140, an oxide semiconductor containing indium (In), gallium (Ga), zinc (Zn) and oxygen (O) may be used. For example, as the oxide semiconductor layer 140, an oxide semiconductor having a composition ratio of In:Ga:Zn:O=1:1:1:4 may be used. However, the oxide semiconductor containing In, Ga, Zn and O used in this embodiment is not limited to the above composition. As the oxide semiconductor, an oxide semiconductor having a composition different from that described above may also be used. For example, in order to improve mobility, an oxide semiconductor layer having an In ratio greater than that described above may also be used. On the other hand, in order to increase the band gap and reduce the influence of light irradiation, an oxide semiconductor layer having a Ga ratio greater than that described above may also be used.

[0071] For example, as the oxide semiconductor layer 140 having an In ratio greater than the above, an oxide semiconductor containing two or more metals including indium (In) may be used. In this case, in the oxide semiconductor layer 140, the ratio of the indium element to all metal elements may be 50% or more in terms of atomic ratio. As the oxide semiconductor layer 140, in addition to indium, gallium (Ga), zinc (Zn), aluminum (Al), hafnium (Hf), yttrium (Y), zirconium (Zr), and lanthanide elements may be used. As the oxide semiconductor layer 140, elements other than the above may also be used.

[0072] As the oxide semiconductor layer 140, other elements may be added to the oxide semiconductor containing In, Ga, Zn and O, for example, metal elements such as Al and Sn may be added. In addition to the above-mentioned oxide semiconductors, an oxide semiconductor containing In and Zn (IZO), an oxide semiconductor containing In, Sn and Zn (ITZO), an oxide semiconductor containing In, Sn, Ga and Zn (ITGZO), an oxide semiconductor containing In and Ga (IGO), etc. may be used as the oxide semiconductor layer 140.

[0073] When the ratio of the indium element is large, the oxide semiconductor layer 140 is easily crystallized. As described above, in the oxide semiconductor layer 140, by using a material in which the ratio of the indium element to all metal elements is 50% or more, it is possible to easily obtain an oxide semiconductor layer 140 having a polycrystalline structure. As a metal element other than indium, the oxide semiconductor layer 140 preferably contains gallium. Gallium belongs to the same Group 13 element as indium. Therefore, the crystallinity of the oxide semiconductor layer 140 is not hindered by gallium, and the oxide semiconductor layer 140 has a polycrystalline structure.

[0074] The oxide semiconductor layer 140 can be formed using a sputtering method. The composition of the oxide semiconductor layer 140 formed by the sputtering method depends on the composition of the sputtering target. Even when the oxide semiconductor layer 140 has a polycrystalline structure, the composition of the sputtering target is substantially consistent with the composition of the oxide semiconductor layer 140. In this case, the composition of the metal element of the oxide semiconductor layer 140 can be determined based on the composition of the metal element of the sputtering target.

[0075] In the case where the oxide semiconductor layer 140 has a polycrystalline structure, the composition of the oxide semiconductor layer can also be determined using an X-ray diffraction (XRD) method. Specifically, the composition of the metal elements of the oxide semiconductor layer can be determined based on the crystal structure and lattice constant of the oxide semiconductor layer obtained by the XRD method. In addition, the composition of the metal elements of the oxide semiconductor layer 140 can also be determined using fluorescent X-ray analysis or electron probe microanalyzer (EPMA) analysis. However, the oxygen element contained in the oxide semiconductor layer 140 will change depending on the process conditions of sputtering, etc., and therefore, it is sometimes impossible to determine using the above method.

[0076] [1-3. Film Formation Method of Oxide Layer 150]

[0077] As described above, the oxide layer 150 included in the radiation detection device 10 according to the present embodiment includes a first region and a second region, wherein the first region is a region near the oxide semiconductor layer 140 and has relatively few hole traps, and the second region is located above the first region and has relatively many hole traps. The difference between the oxide layer 150 in the first region and the second region is caused by the film forming method of the oxide layer 150.

[0078] The film forming process when forming a silicon oxide layer as the oxide layer 150 includes the following steps (1) and (2): The oxide layer 150 in the first region is formed by the step (1), and the oxide layer 150 in the second region is formed by the step (2).

[0079] (1) Interface formation treatment

[0080] (2) Bulk formation process

[0081] (1) The treatment conditions of the interface forming treatment are as follows.

[0082] SiH4 / N2O flow rate = 3 / 1000sccm

[0083] Chamber pressure = 200Pa

[0084] RF power = 20W

[0085] F ratio (RF / SiH4) = 6.7

[0086] Film thickness = 10nm

[0087] (2) The processing conditions of the bulk forming process are as follows.

[0088] SiH4 / N2O flow rate = 10 / 1000sccm

[0089] Chamber pressure = 333Pa

[0090] RF power = 200W

[0091] F ratio (RF / SiH4) = 10.0

[0092] Film thickness = arbitrary

[0093] In this embodiment, the electrode size of the CVD device for forming the oxide layer 150 is a circle with a radius of 9 cm. The area of ​​the electrode of the CVD device is 254 cm 2 Therefore, the power density of the RF power (20 W) in the conditions of (1) the interface formation treatment is 0.079 W / cm 2 (2) The power density of the RF power (200 W) in the bulk formation process is 0.79 W / cm 2 .

[0094] As described above, regarding the film formation power (RF power) in the sputtering method, the RF power (20 W) in the film formation of the oxide layer 150 in the first region is lower than the RF power (200 W) in the film formation of the oxide layer 150 in the second region. Similarly, the ratio of SiH4 gas to N2O gas in the film formation of the oxide layer 150 in the first region (3 / 1000) is smaller than the ratio of SiH4 gas to N2O gas in the film formation of the oxide layer 150 in the second region (10 / 1000). Similarly, the ratio of RF power to SiH4 gas in the film formation of the oxide layer 150 in the first region (6.7) is smaller than the ratio of RF power to SiH4 gas in the film formation of the oxide layer 150 in the second region (10).

[0095] As described above, by forming the oxide layer 150 in the first region in contact with the oxide semiconductor layer 140 at low power, it is possible to form an oxide layer with few hole traps as the oxide layer 150 near the oxide semiconductor layer 140. By making the film thickness of the oxide layer 150 less than 100 nm or less than 50 nm, the amount of hole traps included in the oxide layer 150 can be reduced, and the details will be described later. As a result, it is possible to suppress the characteristic variation of the transistor 20 caused by the holes generated in the oxide semiconductor layer 140 due to the incidence of radiation being captured by the oxide layer 150.

[0096] [1-4. Reliability Test Results of Transistor 20]

[0097] Figure 3 This is a diagram showing the results of a reliability test for visible light of a transistor used in a radiation detection device according to an embodiment of the present invention. Figure 3 The reliability test results shown are for Negative Bias Temperature Illumination Stress (NBTIS). Figure 3 In FIG. 1 , the electrical characteristics of the transistor 20 before NBTIS of each of Example 1 and Comparative Example 1 are indicated by a dotted line, and the electrical characteristics after NBTIS are indicated by a solid line.

[0098] The conditions of the NBTIS reliability test are as follows.

[0099] Channel area size: W / L = 3.0 μm / 3.0 μm

[0100] Light irradiation conditions: With irradiation (7000lx)

[0101] ·Gate voltage: -30V

[0102] Source and drain voltage: 0V

[0103] ·Workbench temperature when stress is applied: 85°C

[0104] Stress application time: 1000 seconds (sec)

[0105] Conducted Figure 3 The structures of the transistors involved in Example 1 and Comparative Example 1 of the reliability test are as follows.

[0106] Gate insulation layer 110\120: SiN\SiO=300\10nm

[0107] Oxide semiconductor layer 140: 30 nm (polycrystalline)

[0108] Oxide layer 150\insulating layer 160: SiO\SiN=300\100nm

[0109] The film forming conditions of the oxide layer 150 in the transistor 20 according to Example 1 are as shown in the above steps (1) to (2). On the other hand, in the film forming conditions of the oxide layer in the transistor according to Comparative Example 1, the film forming conditions in step (1') of Comparative Example 1 are different from the film forming conditions in step (1) of Example 1.

[0110] (1′) The treatment conditions of the interface forming treatment in Comparative Example 1 are as follows.

[0111] SiH4 / N2O flow rate = 10 / 1000sccm

[0112] Chamber pressure = 200Pa

[0113] RF power = 100W

[0114] F ratio (RF / SiH4) = 10.0

[0115] Film thickness = 10nm

[0116] As described above, the processing conditions of the interface film formation treatment of Comparative Example 1 are higher in RF power during film formation, a larger ratio of SiH4 gas to N2O gas, and a larger ratio of RF power to SiH4 gas than those of the interface film formation treatment of Example 1. The amount of hole traps in the oxide layer formed under these conditions is greater than the amount of hole traps in the oxide layer 150 of Example 1. In the following description, the processing conditions of (1) are sometimes referred to as low-power film formation, and the processing conditions of (1') are sometimes referred to as conventional condition film formation.

[0117] like Figure 3 As shown, the threshold variation before and after NBTIS of the transistor 20 according to Example 1 is smaller than that of the transistor according to Comparative Example 1. This result is caused by the fact that the amount of hole traps included in the oxide layer 150 according to Example 1 is smaller than that of the oxide layer according to Comparative Example 1.

[0118] Figure 4 and Figure 5 This is a diagram showing the results of a reliability test on a transistor used in a radiation detection device according to an embodiment of the present invention with respect to radiation. Figure 4 The reliability test shown is the result of X-ray irradiation test. Figure 4 In FIG. 1 , the electrical characteristics of transistor 20 before X-ray irradiation are indicated by a dotted line, and the electrical characteristics after X-ray irradiation are indicated by a solid line. The results of the X-ray irradiation test of Example 1 and Comparative Example 1 are shown in three numbers (#1 to #3). Figure 4 The structure of the transistor involved in the X-ray irradiation test of Example 1 and Comparative Example 1 is Figure 3 same. Figure 5 In the bar chart shown, for Figure 4 The threshold voltage Vth obtained from the electrical characteristics of the device shows the variation before and after the reliability test.

[0119] The conditions of the X-ray irradiation test are as follows.

[0120] Channel area size: W / L = 3.0 μm / 3.0 μm

[0121] ·X-ray irradiation device: MBR-1520R-3 (manufactured by Hitachi Power Solutions Co., Ltd.)

[0122] X-ray irradiation conditions: 30Gy, 60Gy, 90Gy (20mA continuous irradiation)

[0123] X-ray irradiation conditions: filter Al = 1 mm

[0124] like Figure 4 and Figure 5 As shown in FIG. 1 , the threshold variation of the transistor 20 according to Example 1 before and after the X-ray irradiation test is smaller than the threshold variation of the transistor according to Comparative Example 1 before and after the X-ray irradiation test. Figure 3 The same result is caused by the fact that the amount of hole traps included in the oxide layer 150 involved in Example 1 is less than the amount of hole traps included in the oxide layer involved in Comparative Example 1. As described above, the same tendency was confirmed in the NBTIS and X-ray irradiation tests. The reason for confirming the same tendency is that both the threshold change in the NBTIS and the threshold change in the X-ray irradiation test are caused by the holes generated by light irradiation or X-ray irradiation being captured by the oxide layer 150.

[0125] As described above, since the correlation between the threshold variation in NBTIS and the threshold variation in the X-ray irradiation test was confirmed, only the results of NBTIS will be shown below.

[0126] Figure 6 This is a diagram showing the results of a reliability test for visible light of a transistor used in a radiation detection device according to an embodiment of the present invention. Figure 6 The reliability test results shown are obtained by evaluating the change in threshold voltage Vth based on NBTIS for samples with different structures. Figure 6 Detailed Description of the Invention 2 and Comparative Examples 2 to 5 in which reliability is improved by reducing the thickness of the oxide layer 150 are shown.

[0127] about Figure 6 The samples of Example 2 and Comparative Examples 2 to 5 shown have the following common structure.

[0128] Oxide semiconductor layer 140: 30 nm (polycrystalline)

[0129] Film formation conditions of the oxide layer 150: Steps (1′) and (2)

[0130] about Figure 6 The samples shown have different structures for each sample as follows.

[0131] [Gate insulation layer 110\120]

[0132] Comparative Example 2: SiN\SiO=300\100nm

[0133] Comparative Example 3: SiN\SiO=300\50nm

[0134] Comparative Example 4: SiN\SiO=300\30nm

[0135] Comparative Example 5: SiN\SiO=300\10nm

[0136] Example 2: SiN\SiO=300\30nm

[0137] [Oxide layer 150\insulating layer 160]

[0138] Comparative Example 2: SiO\SiN=300\100nm

[0139] Comparative Example 3: SiO\SiN=300\100nm

[0140] Comparative Example 4: SiO\SiN=300\100nm

[0141] Comparative Example 5: SiO\SiN=300\100nm

[0142] Example 2: SiO\SiN=50\100nm

[0143] like Figure 6 As shown in FIG. 1 , the variation of the threshold voltage Vth of Example 2 is small compared with Comparative Examples 2 to 5. That is, it can be seen that the thickness of the oxide layer 150 has a great influence on the variation of the threshold voltage Vth. On the other hand, it can be seen that the thickness of the gate insulating layers 110 and 120 has a small influence on the variation of the threshold voltage Vth. Figure 6As shown in FIG. 1 , when the oxide layer 150 has a thickness of 50 nm or less, the reliability improvement effect based on NBTIS can be obtained. Similarly, when the oxide layer 150 has a thickness of 50 nm or less, the reliability improvement effect for the X-ray irradiation test can be obtained.

[0144] Figure 7 This is a diagram showing the results of a reliability test for visible light of a transistor used in a radiation detection device according to an embodiment of the present invention. Figure 7 The reliability test results shown are obtained by evaluating the change in threshold voltage Vth based on NBTIS for samples with different structures. Figure 7 Examples 3 to 6 are shown in which reliability is improved by forming the oxide layer 150 with low power and reducing its thickness.

[0145] about Figure 7 The samples of Examples 3 to 6 shown have the following common structure.

[0146] Oxide semiconductor layer 140: 30 nm (polycrystalline)

[0147] Film formation conditions of oxide layer 150: Steps (1) and (2)

[0148] about Figure 7 The samples shown have different structures for each sample as follows.

[0149] [Gate insulation layer 110\120]

[0150] Example 3: SiN\SiO=300\50nm

[0151] Example 4: SiN\SiO=300\50nm

[0152] Example 5: SiN\SiO=300\30nm

[0153] Example 6: SiN\SiO=300\10nm

[0154] [Oxide layer 150\insulating layer 160]

[0155] Example 3: SiO\SiN=300\100nm

[0156] Example 4: SiO\SiN=100\100nm

[0157] Example 5: SiO\SiN=50\100nm

[0158] Example 6: SiO\SiN=50\100nm

[0159] like Figure 7 As shown in FIG. 1 , in Examples 3 to 6, the film forming conditions of the oxide layer 150 are all low power film forming conditions. Therefore, under all conditions, Figure 6 Compared with the result of the embodiment 3, the change of the threshold voltage Vth is small. Among them, by comparing Example 3 with Examples 4 to 6, it can be seen that by reducing the film thickness of the oxide layer 150 from 300nm to 100nm, the change of the threshold voltage Vth is reduced. That is, when the film forming condition of the oxide layer 150 is low-power film formation, by making the film thickness of the oxide layer 150 less than 100nm, the amount of hole traps included in the oxide layer 150 can be reduced, and the effect of improving the reliability of NBTIS can be obtained. Similar to this result, when the film thickness of the oxide layer 150 is less than 100nm, the effect of improving the reliability of the X-ray irradiation test is obtained.

[0160] As the embodiments of the present invention, the embodiments described above can be implemented in appropriate combination as long as they do not contradict each other. In addition, the solutions obtained by adding, deleting or changing the design of the components or adding, omitting or changing the conditions of the processes based on the transistors and radiation detection devices of the embodiments by those skilled in the art are also included in the scope of the present invention as long as they have the gist of the present invention.

[0161] Even if there are other effects different from the effects brought about by the schemes of the above-mentioned embodiments, if they are clearly known from the description of this specification or can be easily predicted by those skilled in the art, they are of course understood to be the effects brought about by the present invention.

[0162] Description of Reference Numerals

[0163] 10: Radiation detection device, 20: Transistor, 30: Pixel, 100: Substrate, 105: Gate electrode, 109: Gate control line, 110: Gate insulating layer, 120: Gate insulating layer, 130: Metal oxide layer, 140: Oxide semiconductor layer, 150: Oxide layer, 160: Insulating layer, 161: Opening, 200: Source / drain electrode, 201: Source electrode, 203: Drain electrode, 209: Wiring, 210: Light shielding layer, 220: Connection wiring, 230: Insulating layer, 231: Opening, 300: Photoelectric conversion layer, 309: Wiring, 310: Lower electrode, 320: Upper electrode, 330: Insulating layer, 331: Opening, 340: Insulating layer, 341: Opening, 350: Wiring, 360: Wiring, 400: Wavelength conversion layer, 500: Charge amplifier circuit

Claims

1. A radiation detection device, comprising: An oxide semiconductor layer is used for a channel of a transistor; A photoelectric conversion layer connected to the transistor; a wavelength conversion layer that faces the photoelectric conversion layer and emits visible light based on absorbed radiation; and An oxide layer is in contact with the oxide semiconductor layer and has a thickness of 50 nm or less, between the transistor and the photoelectric conversion layer.

2. The radiation detection device according to claim 1, wherein: The transistor includes a gate electrode layer facing the oxide semiconductor layer and a gate insulating layer located between the oxide semiconductor layer and the gate electrode layer. The oxide semiconductor layer is closer to the photoelectric conversion layer than the gate electrode layer.

3. The radiation detection device according to claim 1, wherein: The oxide layer is a silicon oxide layer.

4. The radiation detection device according to claim 1, wherein: The oxide layer has a thickness of 30 nm or less.

5. The radiation detection device according to any one of claims 1 to 4, wherein: The oxide layer includes a first region and a second region, The first region is in contact with the oxide semiconductor layer, The film thickness of the oxide layer in the first region is thinner than the film thickness of the oxide layer in the second region.

6. The radiation detection device according to claim 5, wherein: The hole-trapping property of the oxide layer in the first region is smaller than the hole-trapping property of the oxide layer in the second region.

7. The radiation detection device according to claim 5, wherein: The oxide layer in the first region is a layer formed under conditions where the film formation power in the sputtering method is lower than that of the oxide layer in the second region.

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