JP2014225527A - Detection device and detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection device capable of achieving both good adhesion between an impurity semiconductor layer and a pixel electrode and good dark current characteristics of a conversion element. A substrate 100 that can transmit visible light, a conversion electrode 12 that includes a pixel electrode, an impurity semiconductor layer 123, and a semiconductor layer 124 in that order from the substrate 100 side, and converts radiation or light into electric charge; And a light source 24 for irradiating visible light onto the conversion element 12, and the pixel electrode includes a metal layer 122 having a thickness at least a part capable of transmitting visible light. . [Selection] Figure 1

Description

  The present invention relates to a detection apparatus and a detection system applied to a medical image diagnostic apparatus, a nondestructive inspection apparatus, an analysis apparatus using radiation, and the like.

  In recent years, thin-film semiconductor manufacturing technology has been applied to detection devices having an array of pixels (pixel array) in which a switch element such as a TFT (thin film transistor) and a conversion element that converts radiation or light such as a photodiode into a charge are combined. It's being used. As a conventional detection device, Patent Document 1 discloses a switch element disposed on a substrate, a conversion element disposed on the switch element and electrically connected to the switch element, a substrate, the switch element, and the conversion element. And a detection device including an interlayer insulating layer disposed between the two. In addition, the conversion element disclosed in Patent Document 1 includes a pixel electrode electrically connected to the switch element, a counter electrode disposed to face the pixel electrode, and a semiconductor layer disposed between the pixel electrode and the counter electrode. And an impurity semiconductor layer disposed between the pixel electrode and the semiconductor layer. For this pixel electrode, a polycrystallized transparent conductive oxide is used for the purpose of improving the efficiency of light irradiation for reducing afterimages, etc. Further, the conversion element of Patent Document 1 includes a semiconductor layer and a pixel electrode. It is disclosed that a buffer layer may be provided to improve the adhesion to the substrate.

JP 2002-026300 A

  However, in the configuration of Patent Document 1, it is difficult to achieve both the adhesion between the impurity semiconductor layer and the transparent conductive oxide and the dark current characteristics of the conversion element. An attempt to improve the adhesion between the impurity semiconductor layer and the transparent conductive oxide causes a decrease in the dark current characteristics of the conversion element. Conversely, an attempt to improve the dark current characteristics of the conversion element The adhesion between the semiconductor layer and the transparent conductive oxide was reduced. Therefore, an object of the present invention is to provide a detection device that can achieve both good adhesion between the impurity semiconductor layer and the pixel electrode and good dark current characteristics of the conversion element.

  The detection device according to the present invention includes a substrate that can transmit visible light, a pixel electrode, an impurity semiconductor layer, and a semiconductor layer in this order from the substrate side, a conversion element that converts radiation or light into electric charges, and the substrate. And a light source for irradiating the conversion element with the visible light, wherein the pixel electrode includes a metal layer having a thickness that allows at least a part of the pixel electrode to transmit the visible light. .

  According to the present invention, it is possible to provide a detection device capable of achieving both good adhesion between the impurity semiconductor layer and the pixel electrode and good dark current characteristics of the conversion element.

It is the plane schematic diagram and cross-sectional schematic diagram per pixel of the detection apparatus which concerns on 1st Embodiment. It is a typical equivalent circuit schematic of a detection apparatus. It is a cross-sectional schematic diagram for demonstrating the structure of a detection apparatus. It is a plane schematic diagram per pixel of the detection apparatus according to another example of the first embodiment. It is the plane schematic diagram and cross-sectional schematic diagram per pixel of the detection apparatus which concerns on 2nd Embodiment. It is a plane schematic diagram per pixel of the detection device according to the third embodiment. It is a plane schematic diagram per pixel of the detection device according to the fourth embodiment. It is a plane schematic diagram per pixel of the detection device according to the fifth embodiment. It is a conceptual diagram of the radiation detection system using the detection apparatus of this invention.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings. In this specification, in addition to α-rays, β-rays, γ-rays, etc., which are beams produced by particles (including photons) emitted by radioactive decay, beams having the same or higher energy, such as X-rays, Particle rays and cosmic rays are also included in the radiation.

(First embodiment)
First, the detection apparatus according to the first embodiment will be described with reference to FIGS. 1 (a) and 1 (b). FIG. 1A is a schematic plan view of one pixel constituting the detection device, and FIG. 1B is a schematic cross-sectional view taken along line AA ′ of FIG. Note that in FIG. 1A, each insulating layer, covering member, semiconductor layer, and each impurity semiconductor layer, which will be described later, are omitted for simplification.

  In the detection device of the present invention, a plurality of pixels 11 are arranged in a matrix on a substrate 100. As shown in FIGS. 1A and 1B, one pixel 11 includes a conversion element 12 that converts radiation or light into electric charge, and a switch element that outputs an electrical signal corresponding to the electric charge of the conversion element 12. TFT (thin film transistor) 13. In this embodiment, an amorphous silicon PIN photodiode is used as the conversion element 12. The conversion element 12 is disposed on a TFT 13 provided on an insulating substrate 100 such as a glass substrate, with an interlayer insulating layer 120 made of an organic material interposed therebetween. The interlayer insulating layer 120 is disposed so as to cover the plurality of TFTs 13 which are a plurality of switch elements. As shown in FIG. 1B, the surface of the interlayer insulating layer 120 is covered with a covering member 121 and a pixel electrode 122 made of an inorganic material.

  The TFT 13 includes a control electrode 131, an insulating layer 132, a semiconductor layer 133, an impurity semiconductor layer 134 having an impurity concentration higher than that of the semiconductor layer 133, and a first main layer, which are arranged on the substrate 100 in order from the substrate side. An electrode 135 and a second main electrode 136 are included. The impurity semiconductor layer 134 is in contact with the first main electrode 135 and the second main electrode 136 in a partial region thereof, and a region between the regions of the semiconductor layer 133 in contact with the partial region is a channel region of the TFT. The control electrode 131 is electrically connected to the control wiring 15, the first main electrode 135 is electrically connected to the signal wiring 16, and the second main electrode 136 is electrically connected to the pixel electrode 122 of the conversion element 12. It is connected to the. In the present embodiment, the first main electrode 135, the second main electrode 136, and the signal wiring 16 are integrally formed of the same conductive layer, and the first main electrode 135 constitutes a part of the signal wiring 16. ing. The protective layer 137 is provided so as to cover the TFT 13, the control wiring 15, and the signal wiring 16. In this embodiment, an inverted stagger type TFT using the semiconductor layer 133 and the impurity semiconductor layer 134, which are mainly made of amorphous silicon, is used as the switch element. However, the present invention is not limited to this. For example, a staggered TFT mainly composed of polycrystalline silicon, an organic TFT, an oxide TFT, or the like can be used. In the present embodiment, the control electrode 131 and the control wiring 15 are integrally formed using the same conductive layer. The first main electrode 135 and the signal wiring 16 are integrally formed using the same conductive layer.

  The interlayer insulating layer 120 is disposed between the substrate 100 and a pixel electrode 122 of the conversion element 12 described later so as to cover the plurality of TFTs 13 and has a contact hole. The pixel electrode 122 of the conversion element 12 and the second main electrode 136 of the TFT 13 are electrically connected in a contact hole provided in the interlayer insulating layer 120.

The conversion element 12 is disposed on the interlayer insulating layer 120 in this order from the interlayer insulating layer side (substrate side), the metal layer 122 serving as the pixel electrode, the first conductivity type impurity semiconductor layer 123, and the semiconductor layer 124. A second conductivity type impurity semiconductor layer 125, and a counter electrode 126. The pixel electrode includes a metal layer 122 made of a metal material or an alloy material. As the metal material, Al (2.655 × 10 ⁻⁶ Ωcm), Cr (1.29 × 10 ⁻⁵ Ωcm), Ti (4.2 × 10 ⁻⁵ Ωcm), Cu (1.67 × 10 ⁻⁶⁾ (Ωcm) can be preferably selected. As the alloy material, an Al-based alloy is preferably used, and for example, Al—Nd (5.0 × 10 ⁻⁸ Ωcm) can be preferably used. Such a metal material or alloy material has higher plasma resistance in plasma CVD when forming the first conductivity type impurity semiconductor layer 123 than a transparent conductive oxide as in Patent Document 1. Therefore, the metal layer 122 is less damaged by plasma CVD than the transparent conductive oxide layer, and has higher adhesion to the first conductive type impurity semiconductor layer 123 than the transparent conductive oxide layer. be able to. Further, since the metal layer 122 has better surface flatness than the transparent conductive oxide, the lattice defects of the impurity semiconductor layer 123 in contact with the metal layer 122 are larger than those in the impurity semiconductor layer in contact with the transparent conductive oxide. Can be less. Therefore, the impurity semiconductor layer 123 in contact with the metal layer 122 can have a higher impurity concentration than the impurity semiconductor layer in contact with the transparent conductive oxide, and the reverse saturation current at the time of reverse bias of the PIN photodiode, that is, Dark current can be suppressed. The metal layer 122 can transmit visible light emitted from a light source (not shown) that can be provided on the surface side facing the surface on which the pixels 11 of the substrate 100 are disposed in order to reduce afterimages. Has a thickness. When at least part of the metal layer 122 has a thickness that allows visible light to pass therethrough, the semiconductor layer 124 can be sufficiently irradiated with light from a light source (not shown). Further, since the specific resistance of the metal material or alloy material is lower than that of the transparent conductive oxide (˜2.0 × 10 ⁻⁴ Ωcm), the resistance of the metal layer 122 can be used as a pixel electrode even if the gap 122 ′ is provided. It becomes easy to suppress it to be sufficiently low to be usable. Therefore, it becomes easy to ensure a sufficient pixel transfer rate. As described above, by using the metal layer 122 having a thickness at least part of which can transmit visible light, good adhesion between the impurity semiconductor layer and the pixel electrode, good dark current characteristics of the conversion element, and good It is possible to provide a detection device capable of ensuring a high transfer rate. The first conductivity type impurity semiconductor layer 123 has a polarity of the first conductivity type, and has a higher concentration of the first conductivity type impurity than the semiconductor layer 124 and the second conductivity type impurity semiconductor layer 125. The second conductivity type impurity semiconductor layer 125 has a second conductivity type polarity and has a higher concentration of second conductivity type impurities than the first conductivity type impurity semiconductor layer 123 and the semiconductor layer 124. This corresponds to another impurity semiconductor layer of the present invention. The first conductivity type and the second conductivity type are conductivity types having different polarities, and in this embodiment, the first conductivity type is n-type and the second conductivity type is p-type. However, the present invention is not limited thereto, and the first conductivity type may be p-type and the second conductivity type may be n-type. An electrode wiring (not shown) is electrically connected to the counter electrode 126 of the conversion element 12. The metal layer 122 serving as a pixel electrode is electrically connected to the second main electrode 136 of the TFT 13 through a contact hole provided in the interlayer insulating layer 120. In the present embodiment, a photodiode using a first conductivity type impurity semiconductor layer 123, a semiconductor layer 124, and a second conductivity type impurity semiconductor layer 125 mainly containing amorphous silicon is used. In the present embodiment, the surface of the interlayer insulating layer 120 is covered with the metal layer 122 and the covering member 121 made of an inorganic material. Therefore, exposure of the surface of the interlayer insulating layer 120 is suppressed when an impurity semiconductor film to be the impurity semiconductor layer 123 is formed by a CVD method, an evaporation method, a sputtering method, or the like. Therefore, mixing of the organic material into the impurity semiconductor layer 123 can be reduced. In this embodiment, the impurity semiconductor layer 123, the semiconductor layer 124, and the impurity semiconductor layer 125 are separated or removed for each pixel on the covering member 121. At the time of separation or removal, the covering member 121 serves as an etching stopper layer. Therefore, it is possible to suppress contamination of the conversion element by the organic material without exposing the interlayer insulating layer 120 to the dry etching species.

  A passivation layer 127 is provided so as to cover the conversion element 12 and the covering member 121.

  In the present embodiment, the photodiode using the first conductivity type impurity semiconductor layer 123, the semiconductor layer 124, and the second conductivity type impurity semiconductor layer 125, which is mainly made of amorphous silicon, is used. The invention is not limited to this. For example, an element that directly converts radiation into electric charges using the first conductive type impurity semiconductor total 123, the semiconductor layer 124, and the second conductive type impurity semiconductor layer 125 mainly containing amorphous selenium can be used. . The counter electrode 126 is disposed to face the metal layer 122 serving as a pixel electrode, and is electrically connected to an electrode wiring (not shown). When a photodiode using the first conductive type impurity semiconductor layer 123, the semiconductor layer 124, and the second conductive type impurity semiconductor layer 125, which is mainly made of amorphous silicon, is used, the counter electrode 126 is formed of a transparent conductive oxide. Is preferably used. This is because light from a scintillator (not shown) that converts the wavelength of radiation into visible light can be transmitted to the semiconductor layer 124 satisfactorily.

Here, the visible light transmittance of the pixel electrode is preferably 10% or more. As a result of sincerity examination, if the following relationship is satisfied, the transmittance of the pixel electrode necessary for suppressing the afterimage can be obtained. In order to suppress the afterimage, it is necessary to saturate the conversion element 12 by light irradiation. The saturation charge amount N ₁ of the conversion element 12 is represented by the following formula (1).

N ₁ = (ε ₀ * ε _r * S * V) / (q * d) (1)
Here, S (cm ² ) is the area of the semiconductor layer 124, d is the thickness of the semiconductor layer 124, ε _r (F · cm ⁻¹ ) is the relative dielectric constant of the semiconductor layer 124, and ε ₀ (F · cm ^−1). ) Is the relative permittivity of vacuum, V (V) is the voltage of the conversion element 12, and q (C) is the elementary charge. On the other hand, the photocarrier N2 generated in the conversion element 12 by irradiation of visible light from the light source 24 shown in FIGS. 4A and 4B is expressed by the following equation (2).

N ₂ = T _s * T _a * T _c * T _i * η * P * t * S (2)
Here, T _s is the transmittance of the substrate 100 for visible light emitted from the light source 24, T _a is the transmittance of the component between the conversion element 12 and the substrate 100, T _c is the transmittance of the pixel electrode, and T _i is This is the transmittance of the impurity semiconductor layer 123. Further, η is the internal quantum efficiency of the semiconductor layer 124, P is the photon flux (pieces · cm ⁻² · s ⁻¹ ), and t (s) is the irradiation time of visible light.

That the conversion element 12 is saturated by light irradiation satisfies N2 ≧ N1. Therefore, it is desirable that the transmittance T _c of the pixel electrode satisfies the following expression (3) from the expressions (1) and (2).

T _c ≧ (ε ₀ * ε _r * V) / (d * q * T _s * T _a * T _i * η * P * t) (3)
The photon flux P is the peak wavelength λ (nm) of visible light emitted from the light source 24, the illuminance E (lx), the maximum luminous sensitivity Km (lm · W ⁻¹ ), the relative luminous sensitivity F at the wavelength λ, Planck. The constant h (Js) and the speed of light c (ms ⁻¹ ) can be derived from the following equation (5).

P = E * λ / (Km * F * h * c) (4)
From Equation (3) and Equation (4), T _c ≧ (ε ₀ * ε _r * V * Km * F * h * c) / (d * q * T _s * T _a * T _i * η * t * E * Λ) (5)
The thickness of the metal layer 122 can be set as appropriate so as to satisfy the transmittance _Tc of the pixel electrode. Note that although the metal layer 122 is described as a single layer in FIG. 1B, the present invention is not limited thereto, and a plurality of layers of different materials may be used.

  Next, a schematic equivalent circuit of the detection apparatus according to the first embodiment of the present invention will be described with reference to FIG. In FIG. 2, an equivalent circuit diagram of 3 rows and 3 columns is used for simplification of description, but the present invention is not limited to this, and the detection apparatus has n rows and m columns (n and m are both 2 A natural number) pixel array. In the detection apparatus according to this embodiment, a conversion unit 3 including a plurality of pixels 1 arranged in the row direction and the column direction is provided on the surface of the substrate 100. Each pixel 1 includes a conversion element 12 that converts radiation or light into an electric charge, and a TFT 13 that outputs an electric signal corresponding to the electric charge of the conversion element 12. A scintillator (not shown) that converts the wavelength of radiation into visible light may be disposed on the surface of the conversion element on the counter electrode 126 side. The electrode wiring 14 is commonly connected to the counter electrodes 126 of the plurality of conversion elements 12 arranged in the column direction. The control wiring 15 is commonly connected to the control electrodes 131 of the plurality of TFTs 13 arranged in the row direction, and is electrically connected to the drive circuit 2. The drive circuit 2 supplies drive pulses sequentially or simultaneously to a plurality of control wirings 15 arranged in the column direction, so that electric signals from the pixels are parallel to the plurality of signal wirings 16 arranged in the row direction. Is output. The signal wiring 16 is connected in common to the first main electrodes 135 of the plurality of TFTs 13 arranged in the column direction, and is electrically connected to the readout circuit 4. The readout circuit 4 includes, for each signal wiring 16, an integration amplifier 5 that integrates and amplifies the electrical signal from the signal wiring 16, and a sample hold circuit 6 that samples and holds the electrical signal amplified and output by the integration amplifier 5. Prepare. The readout circuit 4 further includes a multiplexer 7 that converts electrical signals output in parallel from the plurality of sample and hold circuits 6 into serial electrical signals, and an A / D converter 8 that converts the output electrical signals into digital data. Including. A reference potential Vref is supplied from the power supply circuit 9 to the non-inverting input terminal of the integrating amplifier 5. The power supply circuit 9 is further electrically connected to a plurality of electrode wirings 14 arranged in the row direction, and supplies a bias potential Vs to the counter electrode 126 of the conversion element 12.

  Below, operation | movement of the detection apparatus of this embodiment is demonstrated. A reference potential Vref is applied to the pixel electrode 122 of the conversion element 12 via the TFT 13, and a bias potential Vs necessary for electron-hole pair separation generated by radiation or visible light is applied to the counter electrode 126. In this state, radiation that has passed through the subject or visible light corresponding thereto enters the conversion element 12, is converted into electric charge, and is accumulated in the conversion element 12. The electrical signal corresponding to the electric charge is output in parallel to each signal line 16 in units of rows by the TFT 13 being turned on in units of rows by a drive pulse applied from the drive circuit 2 to the control line 15. The electric signal output in units of rows is read out to the outside as digital data for one row by the reading circuit 4. By sequentially performing this operation in units of rows, an image signal for one image is output from the pixels to the readout circuit 4, and image data that is digital data for one image is output from the readout circuit 4. The In order to perform such an operation, even if the pixel electrode of the present invention includes the metal layer 122 having the gap 122 ′, a sufficient image signal must be output from the plurality of pixels 11. Therefore, in this invention, it is preferable that it is a pixel electrode which satisfy | fills the following formula | equation (6).

R _S ≦ T / (n × C _S ) −R _ON (6)
Here, _{C S} is the capacitance of the conversion element _12, rows TFT13 driving circuit 2 a plurality of pixels 11 for _{R ON} is for outputting an image signal satisfying the on-resistance, T S / N ratio is required of TFT13 This is the time required to drive sequentially in units. Further, n is the number of rows of the plurality of pixels 11, and _RS is the resistance of a member made up of the impurity semiconductor layer 123 and the pixel electrode. Here, the required S / N ratio is the difference between the amount of charge that can be generated by the conversion element 12 and the amount of charge that can be transferred by the conduction of the TFT 13, that is, the amount of charge remaining in the pixel 11. 12 is the reciprocal of the value divided by the amount of charge that can be generated. Incidentally, in the embodiment shown in FIG. 1 (b), the sheet resistance of the impurity semiconductor layer 123 is preferably equal to or less than 200 times the on-resistance _{R ON} of the TFT 13.

  Next, the configuration of the detection device of the present invention will be described with reference to FIGS. 3 (a) and 3 (b). The detection apparatus illustrated in FIG. 3A includes a pixel 11 and a scintillator 21 in order from the substrate 100 side on the radiation incident side of the substrate 100. In addition, the detection apparatus includes a light source 24 and a circuit board 23 in order from the substrate 100 side on the side opposite to the side where the pixels of the substrate 100 are provided. The light source 24 is for irradiating the semiconductor layer 124 of the conversion element 12 of the pixel 11 with visible light through the gap 122 ′ between the substrate 100 and the metal layer 122 in order to reduce an afterimage. The circuit board 23 is provided with the drive circuit 2 or the readout circuit 4 and is electrically connected to a flexible printed board electrically connected to the pixel 11. The circuit board 23 includes at least one of an integrated circuit that supplies a control signal to the drive circuit 2 and an integrated circuit that processes an image signal from the readout circuit 4. On the other hand, the detection apparatus shown in FIG. 3B includes a pixel 11, a scintillator 21, and a circuit board 23 in this order from the substrate 100 side on the side opposite to the radiation incident side of the substrate 100. The circuit board 23 is provided on the radiation incident side of the substrate 100, that is, on the side opposite to the side on which the pixels of the substrate 100 are provided. 4A and 4B includes a housing 100 that houses a substrate 100, a pixel 11, a scintillator 21, a flexible printed circuit board 22, a circuit board 23, and a light source 24.

Note that FIG. 1B illustrates a mode in which the semiconductor layer 124 and the impurity semiconductor layer 125 are separated for each pixel 11, but the present invention is not limited thereto. As illustrated in FIG. 4, the semiconductor layer 124 and the impurity semiconductor layer 125 may not be separated for each pixel 11. In the form shown in FIG. 4, the area where the semiconductor layer 124 and the impurity semiconductor layer 125 are arranged is larger than in the form shown in FIG. 1B, and the aperture ratio is improved as compared with FIG. In FIG. 4, the counter electrode 126 may be divided for each pixel 11. However, it is preferable that the counter electrode 126 is not separated for each pixel 11 in terms of improving the aperture ratio. This can be suitably applied to other embodiments of the present invention. 1B shows a form in which the covering member 121 is positioned between the metal layers 122, the present invention is not limited thereto. As shown in FIG. 4, the covering member 121 may be disposed so as to cover the entire surface of the interlayer insulating layer 120, thereby covering the surface of the interlayer insulating layer 120 with the metal layer 122 and the covering member 121. In that case, the metal material of the metal layer 122 can be suitably selected from Al, Mo (5.0 × 10 ⁻⁸ Ωcm), Cr, Ti, W (5.65 × 10 ⁻⁶ Ωcm), and Cu. As the alloy material, an Al-based alloy is preferably used, and for example, Al—Nd can be preferably used.

(Second Embodiment)
Next, a detection apparatus according to the second embodiment will be described with reference to FIGS. 5 (a) and 5 (b). FIG. 5A is a schematic plan view of one pixel constituting the detection device, and FIG. 5B is a schematic cross-sectional view taken along the line BB ′ of FIG. In FIG. 5A, each insulating layer, covering member, semiconductor layer, and each impurity semiconductor layer are omitted for simplification. The second embodiment shown in FIGS. 5A and 5B is different from the first embodiment shown in FIGS. 1A and 1C in the following points.

  In the first embodiment, the entire thickness of the metal layer 122 is set to a thickness capable of transmitting visible light from the light source 24. However, in the second embodiment, a part of the metal layer 122 is visible from the light source 24. The thickness is such that light can be transmitted. In particular, in the metal layer 122, the region excluding the region of the metal layer 122 located in the contact hole and the peripheral region of the metal layer 122 has a thickness capable of transmitting visible light from the light source 24. . As a result, it is possible to improve the reliability of electrical connection with the second main electrode 136 in the contact hole and improve the mechanical strength as compared with the first embodiment shown in FIG. It becomes. In FIG. 5B, the metal layer 122 is described as a single layer, but the present invention is not limited thereto. For example, the metal layer 122 has a laminated structure of two layers, the first layer is formed with a thickness of 30 nm using an Al—Nd alloy as a material, the second layer is formed with a thickness of 100 nm using Mo as a material, and the light source 24 The metal layer 122 may be formed by removing the second layer in the region where visible light from the light can be transmitted.

(Third embodiment)
Next, a detection apparatus according to the third embodiment will be described with reference to FIGS. 6 (a) and 6 (b). FIG. 6A is a schematic plan view of one pixel constituting the detection device, and FIG. 6B is a schematic cross-sectional view taken along the line CC ′ of FIG. In FIG. 6A, each insulating layer, covering member, semiconductor layer, and each impurity semiconductor layer are omitted for simplification. The third embodiment shown in FIGS. 6 (a) and 6 (b) differs from the first embodiment shown in FIGS. 1 (a) and 1 (c) in the following points.

The third embodiment is different from the first embodiment in that the pixel electrode further includes a conductive member 122a covering a step located around a region of the metal layer 122 that is electrically connected to the transistor 13. . The metal layer 122 has a step around a region electrically connected to the second main electrode 136 of the transistor 13 in the contact hole. When the metal layer 122 is thin, tearing may occur at this step. Therefore, in this embodiment, the pixel electrode further includes a conductive member 122a that covers the step, so that connection failure due to the tearing of the metal layer 122 at the step can be suppressed. Thereby, compared with the first embodiment shown in FIG. 1B, it is possible to improve the reliability of electrical connection with the second main electrode 136 in the contact hole and improve the mechanical strength. It becomes. The metal material used for the conductive member 122a can be suitably selected from Al, Mo (5.0 × 10 ⁻⁸ Ωcm), Cr, Ti, W, and Cu. As the alloy material used for the conductive member 122a, an Al-based alloy is preferably used, and for example, Al—Nd can be preferably used.

(Fourth embodiment)
Next, a detection apparatus according to a fourth embodiment will be described with reference to FIGS. 7 (a) and 7 (b). FIG. 7A is a schematic plan view of one pixel constituting the detection device, and FIG. 7B is a schematic cross-sectional view taken along the line DD ′ in FIG. In FIG. 7A, each insulating layer, covering member, semiconductor layer, and each impurity semiconductor layer are omitted for simplification. The fourth embodiment shown in FIGS. 7 (a) and 7 (b) differs from the first embodiment shown in FIGS. 1 (a) and 1 (c) in the following points.

The fourth embodiment is different from the first embodiment in that the pixel electrode further includes a conductive member 122b that covers a region electrically connected to the pixel electrode of the transistor 13. The protective layer 137 has an end portion around a region electrically connected to the second main electrode 136 of the transistor 13. When the thickness of the metal layer 122 is small, the metal layer 122 may be stepped in a region covering the end portion of the protective layer 137 of the metal layer 122 and may be broken. Therefore, in this embodiment, the pixel electrode further includes a conductive member 122b that covers the second main electrode 136 of the transistor 13 and the end portion of the protective layer 137, so that connection failure due to tearing of the metal layer 122 can be suppressed. Thereby, compared with the first embodiment shown in FIG. 1B, it is possible to improve the reliability of electrical connection with the second main electrode 136 in the contact hole and improve the mechanical strength. It becomes. The metal material used for the conductive member 122b can be suitably selected from Al, Mo (5.0 × 10 ⁻⁸ Ωcm), Cr, Ti, W, and Cu. Moreover, as an alloy material used for the conductive member 122b, an Al-based alloy is preferably used, and for example, Al—Nd can be preferably used.

(Fifth embodiment)
Next, a detection apparatus according to the fifth embodiment will be described with reference to FIGS. 8A and 8B. FIG. 8A is a schematic plan view of one pixel constituting the detection device, and FIG. 8B is a schematic cross-sectional view taken along line EE ′ of FIG. In FIG. 8A, each insulating layer, covering member, semiconductor layer, and each impurity semiconductor layer are omitted for simplification. The fifth embodiment shown in FIGS. 8A and 8B is different from the first embodiment shown in FIGS. 1A and 1C in the following points.

  In the fifth embodiment, the pixel electrode further includes a conductive layer 122 c made of a transparent conductive oxide disposed between the metal layer 122 and the interlayer insulating layer 120 and electrically connected to the metal layer 122. This is different from the first embodiment. The transparent conductive oxide does not have good adhesion to the impurity semiconductor layer 123, but since the metal layer 122 exists between the conductive layer 122c and the impurity semiconductor layer 123, the transparent conductive oxide is almost in direct contact with the impurity semiconductor layer 123. do not do. Therefore, the metal layer 122 having good adhesion with the impurity semiconductor layer 123 can ensure sufficient adhesion as the pixel electrode. Also, with such a configuration, the sheet resistance of the pixel electrode can be made lower than that of the first embodiment while ensuring the transmittance of visible light from the light source 24.

(Application embodiment)
Next, a radiation detection system using the detection apparatus of the present invention will be described with reference to FIG.

  X-rays 6060 emitted from the X-ray tube 6050 serving as a radiation source pass through the chest 6062 of the patient or subject 6061 and enter each conversion element included in the detection device 6040 of the present invention. This incident X-ray includes information inside the body of the patient 6061. Corresponding to the incidence of X-rays, the conversion unit 3 converts the radiation into electric charges to obtain electrical information. This information is converted into digital data, image-processed by an image processor 6070 as a signal processing means, and can be observed on a display 6080 as a display means in a control room.

  Further, this information can be transferred to a remote place by transmission processing means such as a telephone line 6090, and can be displayed on a display 6081 serving as a display means such as a doctor room in another place or stored in a recording means such as an optical disk. It is also possible for a doctor to make a diagnosis. Moreover, it can also record on the film 6110 used as a recording medium by the film processor 6100 used as a recording means.

DESCRIPTION OF SYMBOLS 11 Pixel 12 Conversion element 13 Switch element 14 Electrode wiring 15 Control wiring 16 Signal wiring 100 Substrate 120 Interlayer insulating layer 121 Cover member 122 Metal layer 123 First conductive type impurity semiconductor layer 124 Semiconductor layer 125 Second conductive type impurity semiconductor layer 126 Counter electrode

Claims (12)

A substrate capable of transmitting visible light;
A conversion element that has a pixel electrode, an impurity semiconductor layer, and a semiconductor layer in order from the substrate side, and converts radiation or light into electric charge;
A light source for transmitting the visible light to the conversion element through the substrate;
A detection device comprising:
The detection device, wherein at least a part of the pixel electrode includes a metal layer having a thickness capable of transmitting the visible light. The metal layer has a thickness d of the semiconductor layer, a dielectric constant of the semiconductor layer ε _r , a dielectric constant of vacuum ε ₀ , a voltage of the conversion element V, an elementary charge q, and the visible light the transmittance T _s of the substrate with respect _to, the transmittance T _a construct between the substrate and the transducer with respect to visible _light, the transmittance T _i of the impurity semiconductor layer with respect to the visible _light, the semiconductor layer The visible light irradiation time t, the visible light illuminance E, the maximum visible light sensitivity Km, the Planck constant h, the speed of light c, and the peak wavelength of the visible light. Λ, and the relative visibility at wavelength λ is F, the transmittance T _{c of the} pixel electrode for the visible light is
T _c ≧ (ε ₀ * ε _r * V * Km * F * h * c) / (d * q * T _s * T _a * T _i * η * t * E * λ)
The detection device according to claim 1, wherein the detection device has a thickness satisfying Each including the conversion element and a transistor that is electrically connected to the pixel electrode and transfers the charge, and a plurality of pixels arranged in a matrix on the substrate;
A drive circuit for sequentially driving the transistors of the plurality of pixels in units of rows in order to output image signals based on the charges from the plurality of pixels;
Including
In order to output the image signal satisfying a required S / N ratio, the drive circuit sequentially converts the transistors of the plurality of pixels in units of rows, so that the capacitance of the conversion element is C _S , the on-resistance of the transistor is R _ON . If the time required for driving is T, the number of rows of the plurality of pixels is n, and the resistance of the member composed of the impurity semiconductor layer and the pixel electrode is R _S ,
R _S ≦ T / (n × C _S ) −R _ON
The detection device according to claim 2, wherein: The transistor is disposed between the substrate and the pixel electrode, and an interlayer insulating layer is disposed between the substrate and the transistor and the pixel electrode,
The interlayer insulating layer is provided with a contact hole for electrically connecting the pixel electrode and the transistor,
The detection device according to claim 3, wherein the transistor and the metal layer are electrically connected in the contact hole.   The detection device according to claim 4, wherein the pixel electrode further includes a conductive member covering a step located around a region of the metal layer electrically connected to the transistor.   The detection device according to claim 4, wherein the pixel electrode further includes a conductive member that covers a region electrically connected to the pixel electrode of the transistor.   The detection device according to claim 4, wherein the pixel electrode further includes a conductive layer made of a transparent conductive oxide disposed between the metal layer and the interlayer insulating layer and electrically connected to the metal layer.   The detection apparatus according to claim 4, further comprising a covering member arranged to cover the surface of the interlayer insulating layer with the pixel electrode.   9. The detection device according to claim 1, wherein the semiconductor layer is made of amorphous silicon, and the impurity semiconductor layer is made of n-type amorphous silicon.   The conversion element includes: a counter electrode disposed to face the pixel electrode; and another impurity semiconductor layer made of p-type amorphous silicon disposed between the semiconductor layer and the counter electrode. The detection device according to claim 9, further comprising: The detection device according to any one of claims 1 to 10,
Signal processing means for processing a signal from the detection device;
Recording means for recording a signal from the signal processing means;
Display means for displaying a signal from the signal processing means;
Transmission processing means for transmitting a signal from the signal processing means;
A detection system comprising:   The detection system according to claim 11, further comprising a radiation source that emits radiation toward the detection device.

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