JP2008053672A - Radiation solid sensor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation solid sensor, along with its manufacturing method, equipped with a recording optical conductive layer in which alkali metal has a specific concentration distribution, with less degradation in sensitivity, and electron travel characteristics is excellent. <P>SOLUTION: In the radiation solid sensor, an electrode is provided on both sides of a recording optical conductive layer. A specified bias voltage is applied between the electrodes, so that the electric charge that occurs inside the recording optical conductive layer as radiation enters is detected as electric signals. A specified region is provided between the electrodes, and the alkali metal average concentration in the region is ten times or more the portion other than the region between the electrodes. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a radiation solid state sensor suitable for application to a radiation imaging apparatus such as an X-ray and a method for manufacturing the same.

  Conventionally, in medical X-ray imaging, a photoconductive layer that is sensitive to X-rays is used as a photoconductor to reduce the exposure dose received by a subject and improve diagnostic performance. An X-ray imaging panel (a radiation solid state sensor) that reads and records a recorded electrostatic latent image with light or a large number of electrodes is known. These are superior in that the resolution is higher than the indirect photographing method using a TV image pickup tube which is a well-known photographing method.

The X-ray imaging panel described above generates charges corresponding to X-ray energy by irradiating the charge generation layer provided in the imaging panel with X-rays, and reads the generated charges as an electrical signal. The photoconductive layer functions as a charge generation layer. Conventionally, materials such as amorphous selenium (a-Se), PbO, PbI ₂ , HgI ₂ , BiI ₃ , and Cd (Zn) Te are used for the photoconductive layer.

  The amorphous selenium can easily cope with an increase in area by using a thin film forming technique such as a vacuum vapor deposition method, but sensitivity tends to deteriorate because it tends to include many structural defects due to amorphous. Therefore, in order to improve performance, it is generally performed to add (doping) an appropriate amount of impurities. For example, Patent Document 1 uses amorphous selenium doped with 0.01 to 10 ppm of alkali metal. The recording photoconductive layer is disclosed in Patent Document 2 using amorphous selenium doped with 70 ppm of Na as an alkali metal, and the recording photoconductive layer is disclosed in Patent Document 3 using amorphous selenium doped with 100 ppm of Na. Each of the photoconductive layers is described.

Patent Document 4 discloses an X-ray image including a semiconductor layer having a thickness of 0.5 to 2 μm made of selenium doped with 20 to 200 ppm alkali metal that conducts electrons without conducting holes. A detector is described. Further, Patent Document 5 describes a multilayer plate for X-ray images having a thickness of 0.5 and 10 μm and having a semiconductor layer having a unipolar buffer layer of selenium doped with alkali metal.
JP 2003-315464 A JP 2001-244492 A US Pat. No. 3,658,989 JP-A-6-209097 Japanese Patent No. 3761691

  As a result of intensive studies by the inventor, if a predetermined region between the electrodes of the radiation solid sensor is a region having a high alkali metal concentration, and a portion other than the predetermined region is a region having a lower alkali metal concentration than the predetermined region. It was found that the electron running property of the recording photoconductive layer can be improved.

  Moreover, local crystallization may occur in amorphous selenium doped with an alkali metal as described in Patent Document 1. If this is used for the photoconductive layer, image defects may occur over time.

  The present invention has been made in view of the above circumstances, and a radiation solid-state sensor provided with a recording photoconductive layer having a specific concentration distribution of doped alkali metal, few defects, and excellent electron transit characteristics, and The object is to provide a manufacturing method thereof.

  The solid state radiation sensor of the present invention is provided with electrodes on both sides of the recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to electrically generate charges generated inside the recording photoconductive layer by incidence of radiation. In the radiation solid state sensor to detect as a signal, a predetermined region is provided between the electrodes, and an alkali metal average concentration in the region is 10 times or more of a portion other than the region between the electrodes. is there.

  The concentration is more preferably 100 times or more. The region is preferably provided in any region within 1000 μm in the thickness direction from one interface of the recording photoconductive layer. More preferably, the recording photoconductive layer is provided from one interface of the recording photoconductive layer to a thickness direction of 20 nm.

The thickness of the region is preferably 5 nm to 100 nm. Further, the alkali metal average concentration in the region is more preferably 0.2 to 10 ppm.
The recording photoconductive layer is preferably made of amorphous selenium.

  The radiation solid-state sensor of the present invention has electrodes provided on both sides of the recording photoconductive layer, and a charge generated in the recording photoconductive layer by radiation incident by applying a predetermined bias voltage between the electrodes. The recording photoconductive layer is amorphous selenium doped with a predetermined amount of alkali metal, and the average concentration of alkali metal in the recording photoconductive layer is 10 ppm or less. And the electronic life of the recording photoconductive layer is 500 microseconds or more.

  Further, the radiation solid-state sensor of the present invention is provided with electrodes on both sides of the recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to generate charges generated in the recording photoconductive layer by radiation incidence. The recording photoconductive layer is amorphous selenium doped with a predetermined amount of alkali metal, and the average concentration of alkali metal in the recording photoconductive layer is the recording light. It is characterized by being 1/100 or less of the alkali metal concentration in the raw material of the conductive layer.

  In the recording photoconductive layer of the radiation solid sensor of the present invention, the alkali metal is preferably Na.

  The radiation solid sensor of the present invention can be manufactured by vapor-depositing amorphous selenium not containing an alkali metal to obtain the recording photoconductive layer in a vapor deposition device modified with a compound containing an alkali metal. .

  The radiation solid state sensor of the present invention is provided with electrodes on both sides of the recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to generate electric signals generated in the recording photoconductive layer by radiation incidence. In the radiation solid-state sensor to detect as described above, a predetermined region is provided between the electrodes, and the alkali metal average concentration in this region is 10 times or more that of the part other than the predetermined region between the electrodes. A solid radiation sensor having a long recording photoconductive layer with excellent electron transit characteristics can be obtained. Further, the radiation solid sensor of the present invention does not impair the hole travel characteristics.

  In particular, the radiation solid sensor of the present invention having a region having a thickness of 5 nm to 100 nm and an average alkali metal concentration of 0.2 to 10 ppm is improved in electron mobility and doped with an alkali metal. This is more preferable because minimization of the risk of crystallization due to this is compatible.

  In the solid state radiation sensor of the present invention, the recording photoconductive layer is amorphous selenium doped with a predetermined amount of alkali metal, and the average concentration of alkali metal in the recording photoconductive layer is 10 ppm or less, and Since the recording photoconductive layer has an electron lifetime of 500 microseconds or more, the recording photoconductive layer can have high electron sensitivity and a high sensitivity with a large charge collection amount.

  Furthermore, the solid state radiation sensor of the present invention comprises a recording photoconductive layer comprising amorphous selenium doped with a predetermined amount of alkali metal, wherein the average concentration of alkali metal in the recording photoconductive layer is that of the recording photoconductive layer. Since the alkali metal concentration in the raw material is 1/100 or less, carrier traps derived from the alkali metal are few and defects are reduced, so that excellent electron mobility can be obtained.

  The radiation solid state sensor of the present invention is provided with electrodes on both sides of the recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to generate electric signals generated in the recording photoconductive layer by radiation incidence. In the radiation solid state sensor to detect as described above, a predetermined region is provided between the electrodes, and the average alkali metal concentration of the predetermined region is 10 times or more that of the portion other than the predetermined region between the electrodes.

In the solid state radiation sensor, a direct conversion system that directly converts radiation into electric charge and accumulates the charge, and the radiation is once converted into light by a scintillator such as CsI: Tl, GOS (Gd ₂ O ₂ S: Tb), and the light. Although there is an indirect conversion system that converts and accumulates charges in the photoconductive layer, the radiation solid sensor of the present invention uses amorphous selenium in the photoconductive layer, even if the former direct conversion system, An indirect conversion type photoelectric conversion layer may be used. In addition to X-rays, γ rays, α rays, etc. can be used as radiation.

  In addition, the solid state radiation sensor of the present invention reads a radiation image detector using a semiconductor material that generates a charge by irradiation of light, so-called optical reading method, and also accumulates the charge generated by irradiation of radiation, A method of reading the accumulated charges by turning on and off an electrical switch such as a thin film transistor (TFT) one pixel at a time (hereinafter referred to as a TFT method) may be used.

  First, a radiation solid state sensor used for the former optical reading method will be described as an example. FIG. 1 is a cross-sectional view showing an embodiment of a solid state radiation sensor of the present invention.

  The radiation solid sensor 10 includes a first conductive layer 1 that is transparent to a recording radiation L1, which will be described later, and a recording radiation that exhibits conductivity when irradiated with the radiation L1 transmitted through the conductive layer 1. The conductive layer 2 and the charge charged on the conductive layer 1 (latent image polar charge; for example, negative charge) act as an insulator and have a charge opposite to the charge (transport polar charge; in the above example) Is a positive charge), a charge transport layer 3 acting as a substantially conductive material, a read photoconductive layer 4 that exhibits conductivity when irradiated with a read light L2 for reading, which will be described later, and a light-transmitting electromagnetic wave L2. The second conductive layer 5 having the property is laminated in this order. Although FIG. 1 shows a mode in which the charge transport layer is provided between the recording radiation conductive layer 2 and the reading photoconductive layer 4, the charge transport layer is replaced with the conductive layer 1 and the recording. It may be provided between the radiation conductive layer 2 for use, or may be provided at both positions, that is, two layers.

  The predetermined region in the radiation solid sensor shown in FIG. 1 is provided between the conductive layer 1 and the conductive layer 5, and preferably from the interface between the recording photoconductive layer 2 and the conductive layer 1 to the recording photoconductive layer 2 side. Or within a thickness direction of 1000 μm on the recording photoconductive layer 2 side from the interface between the recording photoconductive layer 2 and the charge transport layer 3, or a charge transport layer. 3 is preferably provided on the charge transport layer 3 side from the interface between the photoconductive layer 2 and the recording photoconductive layer 2. The same applies to the case where the charge transport layer 3 is provided between the conductive layer 1 and the recording radiation conductive layer 2.

  In the case where the predetermined region is provided in the recording photoconductive layer, the alkali in the raw material of the photoconductive layer is produced when it is intended to produce a recording photoconductive layer made of amorphous selenium doped with an alkali metal having an average concentration of a predetermined amount. It can be manufactured by setting the metal concentration to 10 times or more of the desired average concentration, reacting alkali metal and amorphous selenium in advance to obtain a selenium alloy, and depositing this in a crucible for vapor deposition.

  The predetermined region provided in the recording photoconductive layer is also produced by vapor-depositing a-Se not containing alkali metal in a vapor deposition device (including a crucible) modified with a compound containing alkali metal. can do. Here, being modified with a compound containing an alkali metal means that the alkali metal remains in the vapor deposition device (including the crucible) by performing vapor deposition with the compound containing the alkali metal.

As the compound containing an alkali metal, alkali metal-doped selenium, alkali halide such as NaCl, LiF, RbBr, or NaF, or alkali metal chalcogenide such as Na ₂ S, Na ₂ Se, or Na ₂ Te is used. be able to. Further, the crucible may be immersed in an alkali hydroxide such as NaOH or LiOH.

  A radiation solid sensor having a region manufactured in this way has an alkali metal average concentration in the region that is 10 times or more that of a portion other than the predetermined region between the electrodes, and can be a radiation solid sensor having a long electron lifetime.

As the conductive layers 1 and 5, for example, a transparent glass plate uniformly coated with a conductive material (nesa film or the like), more specifically, polycrystalline ITO (In ₂ O ₃ : Sn), amorphous ITO (In ₂ O ₃ : Sn), amorphous IZO (In ₂ O ₃ : Zn), ATO (SnO ₂ : Sb), FTO (SnO ₂ : F), AZO (ZnO: Al), GZO (ZnO: Ga) A thin film of gold, silver, platinum, aluminum, indium or the like, a coating film of a dispersion of a noble metal (platinum, gold, silver) having a size of about 10 to 1000 nm is preferable.

As the charge transport layer 3, the larger the difference between the mobility of the negative charge charged in the conductive layer 1 and the mobility of the positive charge having the opposite polarity, the better, poly N-vinylcarbazole (PVK), N, N Organic compounds such as' -diphenyl-N, N'-bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD) and discotic liquid crystals, or TPD polymers ( Polycarbonate, polystyrene, PVK, polyvinyl alcohol) dispersion, As ₂ Se ₃ , Sb ₂ S ₃ , silicon oil, semiconductor materials such as a-Se doped with 10 to 200 ppm of Cl, and polycarbonate are suitable. In particular, organic compounds (PVK, TPD, discotic liquid crystal, etc.) are preferable because they have light insensitivity, and since the dielectric constant is generally small, the capacitance of the charge transport layer 3 and the photoconductive layer 4 for reading is reduced, and thus reading is performed. The signal extraction efficiency can be increased.

The photoconductive layer 4 for reading is a-Se doped with 10-200 ppm of a-Se, Cl, selenium doped with 5-200 ppm of a group V element such as As, Se-Te, Se-As-Te, As. ₂ Se ₃ , metal-free phthalocyanine, metal phthalocyanine, MgPc (Magnesium phtalocyanine), VoPc (phase II of Vanadyl phthalocyanine), CuPc (Cupper phtalocyanine), Bi ₁₂ MO ₂₀ (M: Ti, Si, Ge), Bi ₄ M ₃ O ₁₂ (M: Ti, Si, Ge), Bi ₂ O ₃ , BiMO ₄ (M: Nb, Ta, V), Bi ₂ WO ₆ , Bi ₂₄ B ₂ O ₃₉ , ZnO, ZnS, ZnSe, ZnTe, MNbO ₃ A photoconductive substance containing at least one of (M: Li, Na, K), PbO, HgI ₂ , PbI ₂ , CdS, CdSe, CdTe, BiI _{3 and the} like as a main component is preferable. A selenium alloy containing 0.3 to 100 ppm of a monovalent metal and 0.1 to 4000 ppm of a group V element can also be preferably used.

  An electron injection blocking layer may be provided between the first conductive layer and the recording photoconductive layer 2. As the electron injection blocking layer, antimony sulfide, N, N′-diphenyl-N, N′-bis (3-methylphenyl)-[1,1′-biphenyl] -4,4′-diamine (TPD) is used. It is done. There may be a hole injection blocking layer between the reading photoconductive layer 4 and the second conductive layer 5. As the hole injection blocking layer, cerium oxide, antimony sulfide, and zinc sulfide are used.

  Next, a system that uses light to read an electrostatic latent image will be briefly described. FIG. 2 shows a schematic configuration diagram of a recording / reading system (integrating an electrostatic latent image recording device and an electrostatic latent image reading device) using the radiation solid state sensor 10. This recording / reading system comprises a radiation solid state sensor 10, a recording irradiation means 90, a power source 50, a current detection means 70, a reading exposure means 92, and connection means S1, S2, and the electrostatic latent image recording device portion is a radiation solid. The sensor 10 includes a power source 50, a recording irradiation unit 90, and a connection unit S1, and the electrostatic latent image reader unit includes a radiation solid sensor 10, a current detection unit 70, and a connection unit S2.

  The conductive layer 1 of the radiation solid sensor 10 is connected to the negative electrode of the power source 50 through the connection means S1, and is also connected to one end of the connection means S2. One end of the connection means S2 is connected to the current detection means 70, and the conductive layer 5 of the radiation solid sensor 10, the positive electrode of the power source 50, and the other end of the connection means S2 are grounded. The current detection means 70 includes a detection amplifier 70a made of an operational amplifier and a feedback resistor 70b, and constitutes a so-called current-voltage conversion circuit.

  The conductive layer 5 may have a structure described in Japanese Patent Application Laid-Open Nos. 2001-337171 and 2001-160922.

  A subject 9 is disposed on the upper surface of the conductive layer 1, and the subject 9 has a portion 9a that is transparent to the radiation L1 and a blocking portion 9b that is not transparent. The recording irradiation means 90 uniformly exposes the radiation L1 to the subject 9, and the reading exposure means 92 emits the reading light L2 such as laser light, LED, organic EL, inorganic EL, etc. in the direction of the arrow in FIG. It is desirable that the reading light L2 has a linearly converged shape.

  The electrostatic latent image recording process in the recording / reading system configured as described above will be described below with reference to a charge model (FIG. 3). In FIG. 2, the connection means S2 is opened (not connected to either the ground or current detection means 70), the connection means S1 is turned on, and the DC voltage Ed from the power source 50 is applied between the conductive layer 1 and the conductive layer 5. Then, a negative charge is applied to the conductive layer 1 and a positive charge is applied to the conductive layer 5 from the power source 50 (see FIG. 3A). As a result, a parallel electric field is formed between the conductive layers 1 and 5 in the radiation solid sensor 10.

  Next, the radiation L1 is uniformly irradiated toward the subject 9 from the recording irradiation means 90. The radiation L1 passes through the transmission part 9a of the subject 9, and further passes through the conductive layer 1. The radiation conductive layer 2 receives the transmitted radiation L1 and exhibits conductivity. This is understood by acting as a variable resistor that shows a variable resistance value according to the dose of radiation L1, and the resistance value is caused by the generation of a charge pair of electrons (negative charge) and holes (positive charge) by radiation L1. The resistance value is large if the dose of the radiation L1 transmitted through the subject 9 is small (see FIG. 3B). The negative charge (−) and the positive charge (+) generated by the radiation L1 are represented by enclosing − or + in circles in the drawing.

  The positive charge generated in the recording photoconductive layer 2 moves at high speed in the radiation conductive layer 2 toward the conductive layer 1 and is charged to the conductive layer 1 at the interface between the conductive layer 1 and the recording photoconductive layer 2. It disappears by recombining with the negative charge (see FIGS. 3C and 3D). On the other hand, the negative charges generated in the recording photoconductive layer 2 move in the recording photoconductive layer 2 toward the charge transport layer 3. Since the charge transport layer 3 acts as an insulator for a charge having the same polarity as the charge charged in the conductive layer 1 (in this example, a negative charge), the negative charge that has moved through the recording photoconductive layer 2 is used. Stops at the interface between the recording photoconductive layer 2 and the charge transport layer 3 and accumulates at this interface (see FIGS. 3C and 3D). The amount of charge accumulated is determined by the amount of negative charge generated in the recording photoconductive layer 2, that is, the dose of radiation L1 transmitted through the subject 9.

  On the other hand, since the radiation L1 does not pass through the blocking part 9b of the subject 9, no change occurs in the portion corresponding to the lower part of the blocking part 9b of the radiation solid sensor 10 (see FIGS. 3B to 3D). In this way, by exposing the subject 9 to the radiation L1, charges corresponding to the subject image can be accumulated at the interface between the recording photoconductive layer 2 and the charge transport layer 3. The subject image based on the accumulated charges is called an electrostatic latent image.

  Next, an electrostatic latent image reading process will be described with reference to a charge model (FIG. 4). The connection means S1 is opened to stop the power supply, and S2 is temporarily connected to the ground side, and the conductive layers 1 and 5 of the radiation solid sensor 10 on which the electrostatic latent image is recorded are charged to the same potential to recharge the charge. After the arrangement (see FIG. 4A), the connection means S2 is connected to the current detection means 70 side.

  When the reading light L2 is scanned and exposed to the conductive layer 5 side of the radiation solid sensor 10 by the reading exposure means 92, the reading light L2 passes through the conductive layer 5, and the photoconductive layer 4 irradiated with the transmitted reading light L2 is Conductivity is exhibited according to scanning exposure. This is because the recording photoconductive layer 2 is exposed to the radiation L1 to generate positive and negative charge pairs, and similarly, the recording photoconductive layer 2 is irradiated with the reading light L2 to generate positive and negative charge pairs. It depends (see FIG. 4B). As in the recording process, negative charges (−) and positive charges (+) generated by the reading light L2 are represented by enclosing − or + in circles in the drawing.

  Since the charge transport layer 3 acts as a conductor for the positive charge, the positive charge generated in the reading photoconductive layer 4 rapidly moves in the charge transport layer 3 so as to be attracted to the accumulated charge. The accumulated charges recombine and disappear at the interface between the recording photoconductive layer 2 and the charge transport layer 3 (see FIG. 4C). On the other hand, the negative charge generated in the photoconductive layer 4 is recombined with the positive charge of the conductive layer 5 and disappears (see FIG. 4C). The photoconductive layer 4 is scanned and exposed with a sufficient amount of light by the reading light L2, and the accumulated charge accumulated at the interface between the recording photoconductive layer 2 and the charge transport layer 3, that is, the electrostatic latent image is all charged. It is extinguished by recombination. Thus, the disappearance of the charge accumulated in the radiation solid sensor 10 means that the current I has flowed through the radiation solid sensor 10 due to the movement of the charge, and this state is the radiation solid sensor 10. Can be expressed by an equivalent circuit as shown in FIG. 4D, in which the current amount is expressed by a current source whose amount depends on the accumulated charge amount.

  Thus, by detecting the current flowing out of the radiation solid sensor 10 while scanning the reading light L2, it is possible to sequentially read the accumulated charge amount of each scanning-exposed part (corresponding to the pixel). The electrostatic latent image can be read. The operation of the radiation detection unit is described in Japanese Patent Application Laid-Open No. 2000-105297.

  Next, the latter TFT type radiation solid sensor will be described. As shown in FIG. 5, the radiation solid sensor has a structure in which a radiation detection unit 100 and an active matrix array substrate (hereinafter referred to as AMA substrate) 200 are joined. As shown in FIG. 6, the radiation detection unit 100 is roughly divided into a common electrode 103 for applying a bias voltage and a recording that generates carriers that are electron-hole pairs in response to the radiation to be detected in order from the radiation incident side. The photoconductive layer 104 for use and the detection electrode 107 for collecting carriers are stacked. The upper layer of the common electrode may have a radiation detection unit support.

  The predetermined region in the radiation solid-state sensor shown in FIG. 6 is provided between the common electrode 103 for applying the bias voltage and the detection electrode 107 for collecting the carrier, and preferably, the recording photoconductive layer 104 and the application for the bias voltage. It is provided within 1000 μm in the thickness direction on the recording photoconductive layer 104 side from the interface with the common electrode 103.

  The common electrode 103 and the detection electrode 107 are made of a conductive material such as ITO (indium tin oxide), Au, or Pt, for example. Depending on the polarity of the bias voltage, a hole injection blocking layer and an electron injection blocking layer may be attached to the common electrode 103 and the detection electrode 107. As the hole injection blocking layer, cerium oxide, antimony sulfide, and zinc sulfide are used. As the electron injection blocking layer, antimony sulfide, N, N′-diphenyl-N, N′-bis (3-methylphenyl) is used. )-[1,1′-biphenyl] -4,4′-diamine (TPD) is used.

  The configuration of each part of the AMA substrate 200 will be briefly described. As shown in FIG. 7, the AMA substrate 200 is provided with a capacitor 210 as a charge storage capacitor and a TFT 220 as a switching element for each of the radiation detection portions 105 corresponding to pixels. In the support 102, the radiation detection units 105 corresponding to the pixels are two-dimensionally arranged in a matrix configuration of about 1000 to 3000 × 1000 to 3000 in accordance with the required pixels, and the AMA substrate 200 also has pixels. The same number of capacitors 210 and TFTs 220 are two-dimensionally arranged in the same matrix configuration. The charge generated in the recording photoconductive layer is accumulated in the capacitor 210 and becomes an electrostatic latent image corresponding to the optical reading method. In the TFT method, an electrostatic latent image generated by radiation is held in a charge storage capacitor.

  Specific configurations of the capacitor 210 and the TFT 220 in the AMA substrate 200 are as shown in FIG. That is, the AMA substrate support 230 is an insulator, and the connection-side electrode 210b of the capacitor 210 and the TFT 220 are disposed on the ground electrode 210a of the capacitor 210 and the gate electrode 220a of the TFT 220 formed on the surface thereof via the insulating film 240. In addition to the source electrode 220b and the drain electrode 220c being stacked, the outermost surface side is covered with a protective insulating film 250. Further, the connection side electrode 210b and the source electrode 220b are connected to each other and are formed simultaneously. As the insulating film 240 constituting both the capacitor insulating film of the capacitor 210 and the gate insulating film of the TFT 220, for example, a plasma SiN film is used. The AMA substrate 200 is manufactured by using a thin film forming technique or a fine processing technique used for manufacturing a liquid crystal display substrate.

  Subsequently, the joining of the radiation detection unit 100 and the AMA substrate 200 will be described. With the detection electrode 107 and the connection side electrode 210b of the capacitor 210 aligned, both substrates 100 and 200 are made of anisotropic conductive film (ACF) containing conductive particles such as silver particles and having conductivity only in the thickness direction. The substrates 100 and 200 are mechanically combined by heating and pressurizing and bonding together, and at the same time, the detection electrode 107 and the connection side electrode 210b are electrically connected by the interposition conductor 140. .

  Further, the AMA substrate 200 is provided with a read drive circuit 260 and a gate drive circuit 270. As shown in FIG. 7, the read drive circuit 260 is connected to a read wiring (read address line) 280 in the vertical (Y) direction that connects the drain electrodes of the TFTs 220 having the same column, and the gate drive circuit 270 has a row. A horizontal (X) direction read line (gate address line) 290 connecting the gate electrodes of the same TFT 220 is connected. Although not shown, one preamplifier (charge-voltage converter) is connected to one readout wiring 280 in the readout drive circuit 260. As described above, the read driving circuit 260 and the gate driving circuit 270 are connected to the AMA substrate 200. However, an integrated circuit in which the read drive circuit 260 and the gate drive circuit 270 are integrally formed in the AMA substrate 200 is also used.

The radiation detection operation by the radiation imaging apparatus in which the radiation detector 100 and the AMA substrate 200 are joined and combined is described in, for example, Japanese Patent Application Laid-Open No. 11-287862.
Examples of the recording photoconductive layer constituting the radiation solid-state sensor of the present invention are shown below.

(Examples 1-6, Comparative Example 2)
High purity 5N selenium, Na ₂ Se for Na doping was added, filled into a Pyrex (registered trademark) glass tube, vacuum sealed at 0.1 Pa or less, reacted at 550 ° C., and selenium shown in Table 1 An alloy was made. The selenium alloy and high-purity 5N selenium are packed in different stainless steel crucibles, and the amorphous IZO glass substrate is heated to a temperature of 280 ° C. and a vacuum degree of 0.0001 Pa. The substrate temperature is 65 ° C. and the deposition rate is 1 μm / min. Under the conditions, a Se vapor deposition film containing Na having a thickness of 1000 μm was prepared. By adjusting the deposition time during the deposition of the selenium alloy and the high purity 5N selenium, Na localized regions having the respective positions and thicknesses shown in Table 1 were prepared. Finally, gold was deposited as an upper electrode to a thickness of 100 nm, and devices of Examples 1 to 6 and Comparative Example 2 were produced.

(Examples 7 to 10, Comparative Example 1)
High purity 5N selenium, Na ₂ Se for Na doping is added, filled into a Pyrex (registered trademark) glass tube, vacuum sealed at 0.1 Pa or less, reacted at 550 ° C., and selenium alloys shown in Table 1 Was made. This selenium alloy is packed in a stainless steel crucible and applied to an amorphous IZO glass substrate under conditions of a crucible temperature of 280 ° C. and a degree of vacuum of 0.0001 Pa, a substrate temperature of 65 ° C., and a deposition rate of 1 μm / min. An Se vapor-deposited film containing was produced. By adjusting the deposition time during the deposition of the selenium alloy and the high purity 5N selenium, Na localized regions having the respective positions and thicknesses shown in Table 1 were prepared. Devices of Examples 7 to 10 and Comparative Example 1 were fabricated by vapor deposition using gold as an upper electrode so as to have a thickness of 100 nm.

(Example 11)
After the vapor deposition of Example 8, the 2 ppm Na-doped selenium alloy remaining in the vapor deposition crucible was removed under the condition of 380 ° C. for 30 minutes, and then the same crucible was filled with 5N selenium and vapor deposition was performed in the same manner to produce a device. .

(Measurement of electronic lifetime)
S. O. Kasap, J .; A. Based on the description of Rowlands, Journal of Materials Science: Materials in Electronics, 11, 179 (2000), the electronic lifetime was measured by the time-of-flight (TOF) method. The hole lifetime was measured with the bias voltage reversed.

(Measurement of charge collection amount)
An X-ray of 10 mR was irradiated to the Se vapor-deposited film obtained in Examples 1 to 10 and Comparative Examples 1 and 2 for 0.2 seconds under the condition of a voltage of 30 kV with a Mo tube, and the voltage was applied. The pulsed photocurrent generated under the applied conditions was converted to a voltage with a current amplifier and measured with a digital oscilloscope. The applied voltage was applied so as to correspond to an electric field of 10 V / μm, and the charge collection amount was measured by integrating the current over time.

(Analysis of raw materials used in devices)
The raw material Na was analyzed by the atomic absorption method. The element concentration in selenium was expressed in ppm by weight with respect to selenium. In addition, 5N selenium of Comparative Example 1 was below the measurement limit and had a Na concentration of less than 0.01 ppm.

(Analysis of device deposition film)
In order to measure the Na concentration in the deposited film in the devices of Comparative Examples 1 and 2 and the devices of Examples 1 to 10, a silicon wafer was prepared together with a 5 cm square glass substrate provided with an amorphous IZO layer and a comb electrode. At the same time, vapor deposition was performed. The total amount of the selenium alloy film on the silicon substrate is dissolved with nitric acid, the amount of selenium in the solution is determined by ICP emission, the amount of Na is determined by graphite-type atomic absorption spectroscopy, and the average concentration of Na with respect to selenium in the film Asked.

  Also, the Na concentration of 20 nm, 1 μm, 100 μm, and 1000 μm from the interface is obtained by dissolving the Se vapor-deposited film with concentrated nitric acid solution for various times. By calculating the thickness, the relationship with the etching film thickness was obtained, the time during which etching was possible at 20 nm, 1 μm, 100 μm, and 1000 μm was determined from this calibration curve, and the Na concentration at the interface 20 nm, 1 μm, 100 μm, and 1000 μm was obtained. At this time, in order to remove the influence of the contamination of Na on the surface layer, washing with water was performed twice to remove Na and K which have not been incorporated into the selenium layer. The following etching was performed twice.

In addition, when an inorganic layer or an organic layer other than selenium is provided on the selenium layer, peeling due to strain stress when the volume of the selenium layer changes after crystallization, or expansion by cooling. The Na concentration of the selenium layer adhering to the substrate or the selenium layer alone can be obtained by peeling due to the rate difference.
The results are shown in Table 1.

  As is apparent from Table 1, the devices of Examples 1 to 10 have an electron lifetime that is 5 to 10 times higher than that of Comparative Example 1 that is not doped with an alkali metal, and the localized alkali relative to the average alkali metal concentration. The metal concentration was 1.25 to several times higher than Comparative Example 2 in which the metal concentration was less than 10 times. Although not shown in Table 1, the measured charge collection amount was about 1.2 times larger than that of Comparative Example 1.

  In addition, although not shown in Table 1, the hole lifetime was 5 to 10 μs in all the examples and comparative examples. That is, it can be seen that the device of the present invention is not adversely affected in the hole mobility as compared with the conventional device.

In order to estimate the crystallization of amorphous selenium over time in Examples 1 to 10, a transparent glass substrate was prepared together with a 5 cm square glass substrate provided with an amorphous IZO layer and a comb-shaped electrode, and vapor deposition was simultaneously performed. At 300 degrees Celsius and 20% relative humidity for 300 hours, the surface is observed at a magnification of 100 times the reflection mode of the optical microscope, and a locally crystallized granular region is observed, and the number per unit area is counted. did. Although only the crystallized part of about 470 / mm ² was observed only in Example 6, Examples 1 to 5 and 7 to 10 could not observe the crystallized part at all. As described above, among the radiation solid-state sensors of the present invention, those having a thickness of 5 nm to 100 nm and a region having an alkali metal average concentration of 0.2 to 10 ppm are doped with an alkali metal and improved electron mobility. It can be seen that the crystallization is particularly excellent because the crystallization can be minimized.

  Example 11 is a vapor deposition crucible modified with a compound containing an alkali metal, in which a-Se not containing an alkali metal is vapor-deposited. In this case as well, Comparative Example 1 in which no alkali metal is doped is used. Compared with the electron lifetime, it was 7 times higher.

  As described above, the radiation solid state sensor of the present invention has electrodes provided on both sides of the recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes, and is generated inside the recording photoconductive layer by radiation incidence. In a radiation solid state sensor that detects an electric charge as an electric signal, a predetermined region is provided between the electrodes, and the average alkali metal concentration in this region is 10 times or more that of the portion other than the region between the electrodes, so that the electron lifetime is long. Thus, it was possible to obtain a radiation solid sensor provided with a photoconductive layer for recording excellent in electron running characteristics. Moreover, it is possible not to impair hole travelability.

Sectional drawing which shows one Embodiment of the radiation solid sensor of this invention Schematic configuration diagram of a recording and reading system using a radiation solid state sensor Diagram showing the electrostatic latent image recording process in a recording and reading system using a charge model Diagram showing the electrostatic latent image reading process in the recording and reading system using a charge model Schematic diagram showing the combined state of the radiation detector and the AMA substrate Schematic cross-sectional view showing the pixels of the radiation detector Electrical circuit diagram showing equivalent circuit of AMA substrate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st conductive layer 2 Photoconductive layer for recording 3 Charge transport layer 4 Reading photoconductive layer 5 2nd conductive layer 10 Radiation solid state sensor 70 Current detection means

Claims (11)

  In a radiation solid-state sensor in which electrodes are provided on both sides of a recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to detect an electric charge generated inside the recording photoconductive layer as an electric signal by radiation incidence. A radiation solid sensor, wherein a predetermined region is provided between the electrodes, and an average alkali metal concentration in the region is 10 times or more that of a portion other than the region between the electrodes.   2. The radiation solid sensor according to claim 1, wherein the concentration is 100 times or more.   The radiation solid-state sensor according to claim 1, wherein the region is provided in any region within 1000 μm in the thickness direction from one interface of the recording photoconductive layer.   4. The radiation solid-state sensor according to claim 3, wherein the region is provided in a region from one interface of the recording photoconductive layer to a thickness direction of 20 nm.   The radiation solid-state sensor according to any one of claims 1 to 4, wherein the thickness of the region is 5 nm to 100 nm.   The radiation solid sensor according to claim 1, wherein the alkali metal average concentration in the region is 0.2 to 10 ppm.   7. The radiation solid sensor according to claim 1, wherein the recording photoconductive layer is made of amorphous selenium.   In a radiation solid-state sensor in which electrodes are provided on both sides of a recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to detect an electric charge generated inside the recording photoconductive layer as an electric signal by radiation incidence. The recording photoconductive layer is amorphous selenium doped with a predetermined amount of alkali metal, the average concentration of alkali metal in the recording photoconductive layer is 10 ppm or less, and the recording photoconductive layer A solid state radiation sensor characterized by having an electron lifetime of 500 microseconds or more.   In a radiation solid-state sensor in which electrodes are provided on both sides of a recording photoconductive layer, and a predetermined bias voltage is applied between the electrodes to detect an electric charge generated inside the recording photoconductive layer as an electric signal by radiation incidence. The recording photoconductive layer is amorphous selenium doped with a predetermined amount of alkali metal, and the average alkali metal concentration of the recording photoconductive layer is equal to the alkali metal concentration in the raw material of the recording photoconductive layer. A radiation solid sensor characterized by being 1/100 or less.   The radiation solid sensor according to claim 1, wherein the alkali metal is Na.   10. The radiation according to claim 7, 8 or 9, wherein the recording photoconductive layer is obtained by vapor-depositing amorphous selenium not containing an alkali metal in a vapor deposition device modified with a compound containing an alkali metal. Manufacturing method of solid state sensor.

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