JP2014062819A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device with a high resolution as it is required to improve the resolution of a sensor that detects light in order to obtain a detail image.SOLUTION: In an image pickup device 100 with a high resolution (for example, a flat panel detector) that includes a scintillator 102 that converts X rays to light and a photosensor 101, the interval between the photosensor 101 and scintillator 102 is exactly made uniform, which enables light 105 converted by the scintillator 102 to uniformly enter the photosensor 101.

Description

  The present invention relates to an image capturing apparatus. In particular, the present invention relates to a medical image diagnostic apparatus using X-rays.

  Medical diagnostic imaging apparatuses using X-rays are widely used in the medical field. In diagnosis using a conventional medical image diagnostic apparatus using X-rays, a specific part (bone, lung, etc.) of a patient is irradiated with X-rays from an X-ray source, and the X-rays transmitted through the specific part are photographed. Project to. After the projection, the state of the inside of the specific part can be visualized by developing the photographic film.

  In the method using the photographic film, the storage of the photographic film, that is, the storage of the data after the imaging is complicated, so that the method of digitizing the imaging data is becoming widespread. As a method for digitizing imaging data, there is a method using a stimulable phosphor, a so-called photostimulation method. In the stimulating method, a plate is formed of a material having a property (stimulating property) that emits light when irradiated with X-rays, and X-rays transmitted through a specific part of a patient are projected onto the plate. This is a method (imaging plate method) in which imaging data is constructed and digitized by detecting light emitted from the plate by a scanner after X-ray projection.

  The imaging plate method can digitize imaging data, but has a drawback that the digitization process becomes complicated. Thus, in recent years, a method using a flat panel detector (abbreviation of FPD: Flat Panel Detector) has attracted attention. The flat panel detector includes a scintillator that generates charges or light by irradiating X-rays, and an element substrate having a sensor that detects the charges or light. By composing the imaging data from the output of the sensor, the imaging data can be digitized. A configuration in which charges generated by irradiating X-rays are directly detected and output by a sensor is called a direct method. A configuration in which light generated by irradiating X-rays is detected by an optical sensor and output is referred to as an indirect conversion method.

  In the X-ray diagnostic apparatus which is an example of the indirect conversion type image pickup apparatus, a scintillator underlayer is disposed between a sensor panel having a photoelectric conversion element and a scintillator layer, and the sensor panel and the scintillator layer are bonded together. There is something. The scintillator underlayer has a function of protecting the rigidity of the photoelectric conversion element, and examples of the material forming the scintillator underlayer include polyamideimide resin, polyetherimide resin, polyimide resin, epoxy resin, and silicone resin. (See Patent Document 1).

JP 2011-191290 A

In order to acquire a more detailed image, the resolution of the sensor that detects light is required to be high.
An object of one embodiment of the present invention is to provide an image pickup device with high resolution.

  In view of the above problems, an embodiment of the disclosed invention is an image pickup device (e.g., a flat panel detector) including a scintillator that converts X-rays into light and a photosensor, and a distance between the photosensor and the scintillator. Is a high-resolution image pickup device that allows light converted by the scintillator to be uniformly incident on the photosensor.

  Another embodiment of the present invention is an image pickup device having a scintillator and a photosensor. A high-resolution image pickup device in which a spacer is provided between the photosensor and the scintillator so that minute intervals are evenly provided. Device.

  One aspect of the present invention includes a scintillator that converts X-rays into light, a photosensor that receives light converted by the scintillator, and a spacer that is disposed between the scintillator and the photosensor. An image pickup apparatus characterized by that.

  In the above embodiment of the present invention, the photosensor includes a plurality of pixels, and each of the plurality of pixels preferably includes a photodiode, a first transistor, a second transistor, and a third transistor. .

  In the above embodiment of the present invention, one of a source electrode and a drain electrode of the first transistor is electrically connected to one electrode of the photodiode, and the first transistor is an oxide semiconductor. A thin film transistor in which a film is used for a channel formation region is preferably used.

  In the above embodiment of the present invention, the other of the source electrode and the drain electrode of the first transistor is electrically connected to the gate electrode of the second transistor, and the second transistor includes an oxide. A thin film transistor using a semiconductor film for a channel formation region is preferably used.

  In the above embodiment of the present invention, one of the source electrode and the drain electrode of the second transistor is electrically connected to one of the source electrode and the drain electrode of the third transistor, and the third transistor The transistor is preferably formed using a thin film transistor in which an oxide semiconductor film is used for a channel formation region.

  In the above embodiment of the present invention, the photodiode, the first transistor, the second transistor, the third transistor, and the spacer may be formed over a substrate.

  In the above embodiment of the present invention, one spacer may be provided for one or two of the pixels.

  In the above embodiment of the present invention, the plurality of pixels may be formed in a pixel region, and the spacer may be formed in at least one of the pixel region and the outside of the pixel region.

  In the embodiment of the present invention described above, the spacer may be formed so as to completely or partially surround each of the photodiodes.

  In the above embodiment of the present invention, the oxide semiconductor film may be a film containing an oxide of one or more elements selected from indium, zinc, gallium, and tin.

  In the above embodiment of the present invention, the oxide semiconductor film includes a crystal part, and the crystal part has a c-axis aligned in a direction parallel to a normal vector of a formation surface of the oxide semiconductor film. Good.

  In the above embodiment of the present invention, a distance between the scintillator and the photosensor is preferably 0.1 μm or more and 10 μm or less.

  By applying one embodiment of the present invention, an image pickup device with high resolution can be provided.

FIGS. 4A and 4B are diagrams illustrating a state in which an X-ray image of an object to be inspected is captured by the image capturing apparatus according to one embodiment of the present invention, and FIG. 4C is an image capturing apparatus illustrated in FIGS. FIG. 10A is a plan view illustrating an image capturing device 1200 according to one embodiment of the present invention, FIG. 9B is a plan view illustrating an image capturing device 1220, and FIG. 9C is a plan view illustrating an image capturing device 1240. FIG. 3A is a diagram illustrating an example of a circuit configuration of one pixel in a pixel region 1203 illustrated in FIG. 2A; FIG. 3B is a diagram illustrating an example of a layout of a circuit illustrated in FIG. 3 is a timing chart for explaining a reading operation of a photosensor in the image pickup apparatus shown in FIG. Sectional drawing which shows X1-X2 of FIG. 2 (A) and Y1-Y2 of FIG. 3 (B). (A) is a top view which shows the example which has arrange | positioned one spacer per pixel, (B) is a top view which shows the example which has arrange | positioned one spacer per 2 pixels. (A), (B) is a top view which shows an example of arrangement | positioning of the spacer in the image pick-up device shown to FIG. 2 (A), respectively. FIG. 5A is a plan view illustrating an image pickup device 1300 according to one embodiment of the present invention, and FIG. 5B is a plan view in which a left upper portion of FIG. Sectional drawing which shows Z1-Z2 shown to FIG. 8 (A), and Y1-Y2 shown to FIG. 3 (B). (A), (B) is a top view which shows an example which used the spacer as a partition, respectively. The top view which shows an example using the spacer as a partition.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it is easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments below. Note that in all the drawings for describing the embodiments, the same portions or portions having similar functions are denoted by the same reference numerals, and repetitive description thereof is omitted.

  1A and 1B are diagrams illustrating a state in which an X-ray image of the inspection object 107 is captured by the image capturing apparatus 100 according to one embodiment of the present invention, and FIG. It is a conceptual diagram about the structure of the imaging device 100 shown to (A) and (B).

  As shown in FIG. 1C, the image capturing apparatus 100 includes a photosensor 101 and a scintillator 102, and X-rays 104 emitted from an X-ray source 103 are incident on the image capturing apparatus 100. Yes. When the X-ray 104 enters the scintillator 102, light 105 is emitted. The light 105 is incident on the photosensor 101. It is effective that the photosensor 101 has a plurality of pixels arranged in a matrix in the matrix direction.

  As shown in FIGS. 1A and 1B, an object 107 such as a patient is disposed between the image pickup apparatus 100 and the X-ray source 103, and the X-ray 104 emitted from the X-ray source 103 is The light 105 is incident on the scintillator 102 of the image capturing apparatus 100 through the inspection object 107, and the light 105 emitted from the scintillator 102 is received by the photosensor 101, and an X-ray image is captured.

  In order to improve the resolution of the image capturing apparatus 100, it is necessary to make the distance between the photosensor 101 and the scintillator 102 as close as possible. This is because the light 105 converted from the X-ray 104 by the scintillator 102 is diffused and becomes stray light, and the light 105 may be detected by a pixel other than the desired pixel of the photosensor 101, and as a result, the image capturing apparatus 100. This is because the resolution of the image is reduced. Further, in order to improve the resolution of the image capturing apparatus 100, it is necessary to make the distance between the photosensor 101 and the scintillator 102 uniform. This is because if there is a region where the distance between the photosensor 101 and the scintillator 102 is long, the light detected by the pixels in the region becomes weaker than the other regions, and as a result, the resolution of the image capturing apparatus 100 decreases. Because it becomes.

  Thus, in the image pickup device 100 illustrated in FIG. 1C, a columnar spacer 106 is provided between the photosensor 101 and the scintillator 102. In other words, FIG. 1C illustrates an example in which the distance between the photosensor 101 and the scintillator 102 is controlled using a columnar spacer 106 that is selectively formed using a photolithography method. Note that the interval between the photosensor 101 and the scintillator 102 only needs to be smaller than the pixel pitch (a distance connecting the center points of adjacent pixels), and is preferably 0.1 μm or more and 10 μm or less, for example. In addition, the position of the spacer 106 in FIG. 1C is an example, and the practitioner can arbitrarily determine the position, number, density, and the like of the spacer.

  In addition, the distance between the photosensor 101 and the scintillator 102 can be controlled by dispersing spherical spacers (also referred to as bead spacers) instead of the columnar spacers 106. In this manner, by forming a spacer between the photosensor 101 and the scintillator 102, the distance between the photosensor 101 and the scintillator 102 can be formed minutely and uniformly. With such a configuration, light converted from X-rays by the scintillator can be uniformly incident on the photosensor. Therefore, it is possible to provide an image pickup device with little in-plane variation and high resolution.

  FIG. 2A is a plan view illustrating an image capturing device 1200 according to one embodiment of the present invention. The image pickup apparatus 1200 includes a substrate 1201, and a photosensor that forms a pixel region 1203 including a plurality of pixels is formed over the substrate 1201. A scintillator 1202 is formed on the photosensor via a spacer (not shown). With this spacer, the distance between the photosensor and the scintillator 1202 can be made narrow and uniform.

  A plurality of driving ICs 1205 for driving the photosensors are arranged on the substrate 1201. Each drive IC 1205 is mounted on a flexible substrate by a TCP (tape carrier package) 1204, is externally attached to four sides of the substrate 1201, and is disposed so as to surround the pixel region 1203.

  FIG. 2B is a plan view illustrating an image pickup device 1220 according to one embodiment of the present invention. The image pickup device 1220 includes a substrate 1221, and a photosensor that forms a pixel region 1223 including a plurality of pixels is formed over the substrate 1221. A scintillator 1222 is formed on the photosensor via a spacer (not shown), and this spacer can make the distance between the photosensor and the scintillator 1222 narrow and uniform.

  A driver IC 1225 for driving the photosensor is attached to the substrate 1221 by a COG (chip on glass) method, and these driver ICs 1225 are arranged so as to surround the pixel region 1223. Further, FPCs (flexible printed circuit boards) 1224 corresponding to the respective driving ICs 1225 are externally attached to the four sides of the substrate 1221.

  FIG. 2C is a plan view illustrating an image capturing device 1240 according to one embodiment of the present invention. The image pickup device 1240 includes a substrate 1241, and a photosensor and gate drivers 1247 a and 1247 b that form a pixel region 1243 including a plurality of pixels are formed over the substrate 1241. A scintillator 1242 is formed on the photosensor and gate drivers 1247a and 1247b via a spacer (not shown), and this spacer makes the gap between the photosensor and the scintillator 1242 narrow and uniform. it can.

  A plurality of driving ICs 1245 for driving the photosensors are arranged on two sides on the substrate 1241. Each drive IC 1245 is mounted on a flexible substrate by a TCP (tape carrier package) 1246 and is externally attached to two sides of the substrate 1241. The periphery of the pixel region 1243 is surrounded by a TCP 1246 and gate drivers 1247a and 1247b. Gate drivers 1247a and 1247b are built in the panel. In addition, FPC 1244 corresponding to the gate drivers 1247a and 1247b are externally attached to two sides of the substrate 1221.

  FIG. 3A illustrates an example of a circuit configuration of one pixel in the pixel region 1203 illustrated in FIG. In the pixel region 1203, the circuits illustrated in FIG. 3A are arranged in a matrix of a row example.

  As shown in FIG. 3A, one pixel includes one photodiode 201 and three transistors 202, 203, and 204. One electrode of the photodiode 201 is electrically connected to the wiring 206, and the other electrode of the photodiode 201 is electrically connected to one of the source electrode and the drain electrode of the transistor 202. A gate of the transistor 202 is electrically connected to the wiring 207. The other of the source electrode and the drain electrode of the transistor 202 is electrically connected to the wiring 205, and the wiring 205 is electrically connected to the gate of the transistor 203. One of a source electrode and a drain electrode of the transistor 203 is electrically connected to the wiring 209, and the other of the source electrode and the drain electrode of the transistor 203 is electrically connected to one of the source electrode and the drain electrode of the transistor 204. The gate of the transistor 204 is electrically connected to the wiring 208, and the other of the source electrode and the drain electrode of the transistor 204 is electrically connected to the wiring 210.

  Note that in FIG. 3A, the anode of the photodiode 201 is electrically connected to the wiring 206 and the cathode of the photodiode 201 is electrically connected to one of the source electrode and the drain electrode of the transistor 202. Although shown, it is not limited to this. The cathode of the photodiode 201 may be electrically connected to the wiring 206, and the anode of the photodiode 201 may be electrically connected to one of the source electrode and the drain electrode of the transistor 202.

  The photodiode 201 is a photoelectric conversion element that generates a current when irradiated with light. Therefore, a photocurrent flows through the photodiode 201 by detecting light emitted from the scintillator.

  Next, a specific layout of the circuit in FIG. FIG. 3B illustrates an example of a layout of the circuit illustrated in FIG.

  As shown in FIG. 3B, in one pixel 200, a photodiode 201 having a light detection region 211 is formed on one side thereof, and a circuit region having transistors 202 to 204 on the other side. And a spacer 219 is formed in a region that does not overlap with the light detection region 211. Here, the light detection region 211 and the circuit region are separately arranged, but the light detection region 211 may be stacked on the circuit region.

  The conductive layer 214 functions as one of the source electrode and the drain electrode of the transistor 202. The conductive layer 205a functions as the other of the source electrode and the drain electrode of the transistor 202. The transparent conductive film 212 is electrically connected to one electrode of the photodiode 201 and the conductive layer 214. The other electrode of the photodiode 201 is electrically connected to the conductive layer 206b, and the conductive layer 206b is electrically connected to the conductive layer 206a. The conductive layer 213 functions as a gate electrode of the transistor 202 and is further electrically connected to the wiring 207. The wiring 207 is electrically connected to the wiring 217.

  The conductive layer 205b functions as a gate electrode of the transistor 203, and is further electrically connected to the conductive layer 205a. The conductive layer 216 functions as one of a source electrode and a drain electrode of the transistor 203. The conductive layer 215 functions as the other of the source electrode and the drain electrode of the transistor 203 and one of the source electrode and the drain electrode of the transistor 204. The wiring (conductive layer) 210 also functions as the other of the source electrode and the drain electrode of the transistor 204. The wiring (conductive layer) 208 also functions as a gate electrode of the transistor 204. The wiring (conductive layer) 218 is electrically connected to the conductive layer 216 and the wiring 209.

  The wiring 208, the conductive layer 213, the conductive layer 205b, the wiring 218, the conductive layer 206b, and the wiring 217 can be formed by processing one conductive film formed over the insulating surface into a desired shape. Over the wiring 208, the conductive layer 213, the conductive layer 205b, the wiring 218, the conductive layer 206b, and the wiring 217, a gate insulating film (corresponding to the insulating films 306 and 307 in FIG. 5) is formed. Further, the conductive layer 206b, the wiring 207, the wiring 209, the wiring 210, the conductive layer 214, the conductive layer 205a, the conductive layer 216, and the conductive layer 215 are obtained by forming one conductive film formed over the gate insulating film into a desired shape. It can be formed by processing.

  An insulating film (not shown) is formed over the conductive layer 206b, the wiring 207, the wiring 209, the wiring 210, the conductive layer 214, the conductive layer 205a, the conductive layer 216, and the conductive layer 215. A transparent conductive film 212 is formed on this insulating film.

  The transistor 202 can be formed using a thin film transistor in which a semiconductor layer such as amorphous silicon, microcrystalline silicon, polycrystalline silicon, or single crystal silicon is used for a channel formation region. Note that the transistor 202 accumulates electric charge generated when the photodiode 201 detects light as a potential in the wiring 205 and holds the potential, so that the transistor 202 has high mobility and an off-state current. It is preferable to use an extremely low thin film transistor. Therefore, the transistor 202 is preferably formed using a thin film transistor in which an oxide semiconductor film is used for a channel formation region.

  The transistor 203 can be formed using a thin film transistor using a semiconductor layer such as amorphous silicon, microcrystalline silicon, polycrystalline silicon, or single crystal silicon. Note that the transistor 203 preferably has high mobility because it has a function of amplifying an electric signal generated by the photodiode 201. On the other hand, in order to prevent unnecessary potential from being output to the wiring 209, the off-state current is preferably low. Therefore, a structure in which the transistor 203 is formed using a thin film transistor in which an oxide semiconductor film capable of achieving both high mobility and low off-state current is used for a channel formation region is also effective.

  The transistor 204 can be formed using a thin film transistor using a semiconductor layer such as amorphous silicon, microcrystalline silicon, polycrystalline silicon, or single crystal silicon. Note that the transistor 204 preferably has high mobility because it has a function of controlling the output of the pixel. On the other hand, in order to prevent unnecessary potential from being output to the wiring 210, it is preferable that the off-state current be low. Therefore, a structure in which the transistor 204 is formed using a thin film transistor in which an oxide semiconductor film capable of achieving both high mobility and low off-state current is used for a channel formation region is also effective.

  Next, a photosensor reading operation in the image pickup device illustrated in FIG. 2A will be described with reference to a timing chart in FIG.

  In FIG. 4, each of the signals 3001 to 3005 corresponds to the potential of the wiring 206, the wiring 207, the wiring 208, the wiring 205, and the wiring 210 in FIG. Note that the potential of the wiring 209 is constant at “L” (low).

  At time A, when the potential of the wiring 206 (signal 3001) is set to “H” (high) and the potential of the wiring 207 (signal 3002) is set to “H” (reset operation starts), a forward bias is applied to the photodiode 201. Thus, the potential of the wiring 205 (signal 3004) becomes “H”. Note that the potential of the wiring 210 (signal 3005) is precharged to “H”.

  At time B, the potential of the wiring 206 (signal 3001) is set to “L”, and the potential of the wiring 207 (signal 3002) is set to “H” (reset operation end, cumulative operation start). The potential of the wiring 205 (signal 3004) starts to decrease. Since the off-current of the photodiode 201 increases when light is irradiated, the rate of decrease in the potential of the wiring 205 (signal 3004) changes in accordance with the amount of light irradiated. That is, the channel resistance between the source and the drain of the transistor 203 changes in accordance with the amount of light with which the photodiode 201 is irradiated.

  At the time C, when the potential of the wiring 207 (signal 3002) is set to “L” (accumulation operation ends), the potential of the wiring 205 (signal 3004) becomes constant. Here, the potential is determined by the amount of charge generated by the photodiode during the accumulation operation. That is, it varies according to the amount of light that has been irradiated to the photodiode. In addition, since the transistor 202 is formed using a thin film transistor with an extremely low off-state current in which a channel formation region is formed using an oxide film semiconductor layer, the charge amount can be kept constant until a subsequent selection operation is performed. .

  Note that when the potential of the wiring 207 (the signal 3002) is set to “L”, the potential of the wiring 205 changes due to parasitic capacitance between the wiring 207 and the wiring 205. When the change amount of the potential change is large, the amount of charge generated by the photodiode during the accumulation operation cannot be accurately obtained. In order to reduce the amount of change in potential, measures such as reducing the gate-source (or gate-drain) capacitance of the transistor 202, increasing the gate capacitance of the transistor 203, and providing a storage capacitor in the wiring 205 are taken. It is valid. In FIG. 4, it is assumed that the above potential change can be ignored by taking these measures.

  At time D, when the potential of the wiring 208 (the signal 3003) is set to “H” (selection operation starts), the transistor 204 is turned on, and the wiring 209 and the wiring 210 are turned on through the transistor 203 and the transistor 204. . Then, the potential of the wiring 210 (signal 3005) decreases. Note that the precharge of the wiring 210 is ended before the time D. Here, the rate at which the potential of the wiring 210 (signal 3005) decreases depends on the current between the source and the drain of the transistor 203. That is, it changes according to the amount of light irradiated to the photodiode 201 during the accumulation operation.

  At time E, when the potential of the wiring 208 (signal 3003) is set to “L” (selection operation ends), the transistor 204 is cut off, and the potential of the wiring 210 (signal 3005) becomes a constant value. Here, the constant value changes according to the amount of light irradiated on the photodiode 201. Therefore, by acquiring the potential of the wiring 210, the amount of light applied to the photodiode 201 during the accumulation operation can be known.

  More specifically, when the light applied to the photodiode 201 is strong (weak), the potential of the wiring 205 is low (high) and the gate voltage of the transistor 203 is low (high). The potential at which the potential (signal 3005) decreases is slow (early). Therefore, the potential of the wiring 210 becomes high (low).

  By setting it as the above forms, an image pick-up device with high resolution can be provided. That is, by increasing the resolution of the photosensor, a more detailed affected area image can be acquired. Therefore, more accurate diagnosis is possible.

  5 is a cross-sectional view illustrating X1-X2 illustrated in FIG. 2A and Y1-Y2 illustrated in FIG.

  A terminal electrode 302, conductive layers 213 and 206a, and a wiring 217 are formed over the substrate 301, and an insulating film 306 is formed over the terminal electrode 302, the conductive layers 213, 206a, and the wiring 217. An insulating film 307 is formed over the insulating film 306, and an oxide semiconductor film 311 located over the conductive layer 213 is formed over the insulating film 307. A connection hole located on the wiring 217 is formed in the insulating films 306 and 307, and a wiring 207 is formed in the connection hole and on the insulating film 307. A wiring 210 is formed over the insulating film 307. In addition, a conductive layer 312 a is formed over one of the oxide semiconductor films 311, and a conductive layer 312 b is formed over the other of the oxide semiconductor films 311.

  An insulating film 313 is formed over the wirings 207 and 210, the conductive layers 312 a and 312 b, the oxide semiconductor film 311, and the insulating film 307, and the insulating film 314 is formed over the insulating film 313. Insulating films 313 and 314 are formed with connection holes located on the wiring. A p-type semiconductor film 308, an i-type semiconductor film 309, and an n-type semiconductor film 310 are sequentially stacked in the connection hole and on the insulating film 314. These semiconductor films 308 to 310 constitute a photodiode 201.

  A planarization film 315 is formed over the photodiode 201 and the insulating film 314. An insulating film 316 is formed over the planarization film 315 and the insulating film 306. A connection hole located on the semiconductor film 310 is formed in the planarization film 315 and the insulating film 316. In addition, connection holes located on the conductive layer 312a are formed in the planarization film 315 and the insulating films 313, 314, and 316. A transparent conductive film 317 (corresponding to the transparent conductive film 212 shown in FIG. 3) is formed in these connection holes and on the insulating film 316, and the conductive layer 312a (the conductive layer 214 shown in FIG. 3) is formed by the transparent conductive film 317. And the semiconductor film 310 are electrically connected.

  A columnar spacer 219 is formed over the insulating film 316. An adhesive layer 318 is disposed around the spacer 219, over the transparent conductive film 317, and the insulating film 316. A scintillator 319 is formed over the adhesive layer 318 and the spacer 219. A scintillator protective layer 320 is formed on the scintillator 319. The spacer 219 can make the distance between the scintillator 319 and the photodiode 201 narrow, constant, and uniform.

  Openings are formed in the insulating films 306 and 316 located on the outer periphery of the substrate 301, and the terminal electrodes 302 are exposed through these openings. A transparent conductive film 303 is formed on the terminal electrode 302, and an anisotropic conductive film 304 is formed on the transparent conductive film 303. A TCP 305 is attached on the anisotropic conductive film 304.

Next, the arrangement of the spacers 219 will be described with reference to FIGS.
FIG. 6A is a plan view illustrating an example of the arrangement of the spacers 219 in the image pickup device according to one embodiment of the present invention. In this image pickup apparatus, one pixel 200 including a light detection region 250 and a circuit region 251 formed adjacent to the light detection region 250 is arranged in a matrix in a matrix direction. One spacer 219 is arranged for each pixel 200. The spacer 219 is disposed at a position that does not overlap the light detection region 250.

FIG. 6B is a plan view illustrating an example of the arrangement of the spacers 219 in the image pickup device according to one embodiment of the present invention. The same portions as those in FIG. Only explained.
One spacer 219 is arranged for two pixels 200. Thus, the number of spacers need not be one per pixel, and a plurality of spacers can be arranged at an arbitrary interval (density).

FIG. 7A is a plan view illustrating an example of the arrangement of the spacers 1254 in the image pickup device illustrated in FIG.
The spacer 1254 is disposed only in the pixel region 1203 and is not disposed outside the pixel region 1203.

FIG. 7B is a plan view illustrating an example of the arrangement of the spacers 1254, 1255a, and 1255b in the image pickup apparatus illustrated in FIG.
The spacer 1254 is disposed in the pixel region 1203, and the spacers 1255a and 1255b are disposed outside the pixel region 1203.

  FIG. 8A is a plan view illustrating an image pickup device 1300 according to one embodiment of the present invention, and FIG. 8B is an enlarged plan view of the upper left portion of FIG.

  The image pickup device 1300 includes a substrate 1301, and a photosensor that forms a pixel region 1303 including a plurality of pixels is formed over the substrate 1301. A scintillator 1302 is formed on the photosensor via a spacer 1307, and the spacer 1307 can make the distance between the photosensor and the scintillator 1302 narrow and uniform.

  Between the substrate 1301 and the scintillator 1302, a sealant 1306 located outside the pixel region 1303 is disposed. TCP 1304 having a driving IC 1305 is provided on four sides of the substrate 1301. Here, no injection port for injecting the adhesive is provided. Therefore, after drawing the sealing material 1306, an appropriate amount of adhesive is dropped on a region surrounded by the sealing material 1306, and the scintillator 1302 is bonded to the substrate 1301, whereby the image pickup device 1300 is manufactured.

  8A and 8B, an injection port for injecting an adhesive is not provided. However, after an injection port is provided in the sealing material 1306 and an adhesive is injected by a vacuum injection method, a sealing material ( You may employ | adopt the method of sealing an injection port by not shown.

  9 is a cross-sectional view showing Z1-Z2 shown in FIG. 8A and Y1-Y2 shown in FIG. 3B, and only different portions from FIG. 5 will be described.

  A space between the scintillator 319 (corresponding to 1302 in FIG. 8) and the substrate 301 (corresponding to 1301 in FIG. 8) is sealed with a sealing material 321 (corresponding to 1306 in FIG. 8). In FIG. 5, columnar spacers 219 are formed on the insulating film 316, but in FIG. 9, spherical spacers 322 are formed on the insulating film 316.

  Next, an example in which a spacer is used as a partition in the image pickup device according to one embodiment of the present invention will be described with reference to FIGS.

FIG. 10A is a plan view showing an example in which a spacer is used as a partition. The same portions as those in FIG. 6A are denoted by the same reference numerals, and only different portions will be described.
The periphery of one pixel 200 is surrounded by a partition 500, and this partition 500 also functions as a spacer. That is, the partition wall 500 is divided in units of pixels.

  As shown in FIG. 10A, stray light can be blocked between adjacent pixels by separating the light detection regions 250 of adjacent pixels 200 from each other by a partition wall 500. Therefore, it is possible to prevent stray light from entering the light detection region adjacent to the light detection region 250 where light should be detected and detecting the stray light that has entered in the adjacent light detection region. Therefore, it contributes to increasing the resolution of the sensor in the image pickup apparatus.

FIG. 10B is a plan view showing an example in which a spacer is used as a partition. The same portions as those in FIG. 10A are denoted by the same reference numerals, and only different portions will be described.
The periphery of the light detection region 250 of one pixel 200 is surrounded by a partition wall 501, and this partition wall 501 also functions as a spacer.

  The same effect as that of the image pickup apparatus shown in FIG. 10A can be obtained also in the image pickup apparatus shown in FIG.

FIG. 11 is a plan view showing an example in which a spacer is used as a partition. The same parts as those in FIG. 10A are denoted by the same reference numerals, and only different parts will be described.
The periphery of one pixel 200 is not completely surrounded by the partition wall 502. In other words, a gap is provided between the partition wall 502 and the partition wall 502. The partition wall 502 also functions as a spacer.

  Also in the image pickup apparatus shown in FIG. 11, the same effect as that of the image pickup apparatus shown in FIG.

  Further, in the image pickup apparatus shown in FIG. 11, since a gap is provided between the partition walls 502 and 502, the adhesive can be smoothly injected into the pixels 200 through the gap. Therefore, it is possible to facilitate the step of attaching the scintillator to the substrate.

[Description of each component of the imaging device]
<Board>
As a material for the substrate, it can be appropriately selected from glass, plastic and the like.

<Spacer>
The columnar spacer is for maintaining a gap between the scintillator and the substrate or a gap between the scintillator and the photodiode. This spacer is also called a photolithography spacer, a post spacer, or a column spacer. As a method for manufacturing the columnar spacer, an organic insulating material such as photosensitive acrylic is applied to the entire surface of the substrate by a spin coating method, and this is performed through a series of photolithography steps, thereby leaving the photosensitive acrylic remaining on the substrate. Serves as a spacer. In this method, depending on the mask pattern at the time of exposure, exposure can be performed at a place where the spacer is to be arranged, so by arranging this columnar spacer in a portion not overlapping the photodiode, not only the gap between the scintillator and the substrate is maintained. The light converted by the scintillator can be prevented from entering a photodiode other than the photodiode to be incident.

  The columnar spacer is made of an organic resin material containing at least one of acrylic, polyimide, polyimide amide, and epoxy as a main component, or any one of silicon oxide, silicon nitride, and silicon oxynitride, or a laminated film thereof. It may be an inorganic material. In addition, when a spherical spacer is used instead of a columnar spacer, an inorganic compound material such as glass, silica, metal oxide (such as alumina), polyacryl, nylon, polyester, polyethylene, A plastic material such as polystyrene, polypropylene, or nylon may be used.

<Seal material>
As the sealing material, an insulating epoxy resin material or the like may be used, or an acrylic photo-curing resin or an acrylic thermosetting resin may be used. Moreover, as a sealing material, it is good to use a thing with a viscosity of 40-400 Pa.s, for example including a filler of diameter 6 micrometers-24 micrometers.

<Scintillator>
The scintillator may be a scintillator layer. The scintillator converts radiation into light that can be sensed by a photoelectric conversion element (photodiode), and has a structure having a plurality of columnar crystals. In a scintillator having a columnar crystal, light generated by the scintillator propagates through the columnar crystal, so that light scattering is small and resolution can be improved. As a material of the scintillator for forming the columnar crystal, a material mainly composed of an alkali halide is preferably used. For example, CsI: Tl, CsI: Na, CsBr: Tl, NaI: Tl, LiI: Eu, KI: Tl, etc. are used. For example, CsI: Tl can be formed by simultaneously depositing CsI and Tl.

The scintillator is generally made of cesium iodide (CsI): sodium (Na), cesium iodide (CsI): thallium (Tl), sodium iodide (NaI), or gadolinium oxysulfide (Gd ₂ O ₂ S). ), Etc., and the resolution characteristics can be improved by forming grooves by dicing or the like, or by depositing by a vapor deposition method so that a columnar structure is formed. Examples of other scintillator materials include a-Se, Si, CdTe, CdZnTe, HgI ₂ , and PbI ₂ .

<Adhesive layer>
The adhesive layer (adhesive) may be made of an adhesive such as an ultraviolet curable resin or a thermosetting resin, an adhesive, a hot melt, etc., and an ultraviolet curable resin is preferably used. Any of them should have a low viscosity that can be filled.

<Detailed description of oxide semiconductor film>
The oxide semiconductor film may have an amorphous structure or a polycrystalline structure. In addition, the oxide semiconductor film may be a CAAC-OS (C Axis Crystalline Oxide Semiconductor) film.

  The CAAC-OS film is not completely single crystal nor completely amorphous. The CAAC-OS film is an oxide semiconductor film with a crystal-amorphous mixed phase structure where crystal parts are included in an amorphous phase. Note that the crystal part is often large enough to fit in a cube whose one side is less than 100 nm. Further, in the observation image obtained by a transmission electron microscope (TEM), the boundary between the amorphous part and the crystal part included in the CAAC-OS film is not clear. Further, a grain boundary (also referred to as a grain boundary) cannot be confirmed in the CAAC-OS film by TEM. Therefore, in the CAAC-OS film, reduction in electron transfer due to grain boundaries is suppressed.

  In the crystal part included in the CAAC-OS film, the c-axis is aligned in a direction parallel to the normal vector of the formation surface of the CAAC-OS film or the normal vector of the surface, and triangular when viewed from the direction perpendicular to the ab plane. It has a shape or hexagonal atomic arrangement, and metal atoms are arranged in layers or metal atoms and oxygen atoms are arranged in layers as viewed from the direction perpendicular to the c-axis. Note that the directions of the a-axis and the b-axis may be different between different crystal parts. In this specification and the like, a simple term “vertical” includes a range from 85 ° to 95 °. In addition, a simple term “parallel” includes a range from −5 ° to 5 °.

  Note that the distribution of crystal parts in the CAAC-OS film is not necessarily uniform. For example, in the formation process of the CAAC-OS film, when crystal growth is performed from the surface side of the oxide semiconductor film, the ratio of crystal parts in the vicinity of the surface might be high. In addition, when an impurity is added to the CAAC-OS film, the crystal part in a region to which the impurity is added becomes amorphous in some cases.

  Since the c-axis of the crystal part included in the CAAC-OS film is aligned in a direction parallel to the normal vector of the formation surface of the CAAC-OS film or the normal vector of the surface, the shape of the CAAC-OS film (formation surface) Depending on the cross-sectional shape of the surface or the cross-sectional shape of the surface).

  Note that the c-axis direction of the crystal part is parallel to the normal vector of the surface where the CAAC-OS film is formed or the normal vector of the surface. The crystal part is formed by film formation or by performing crystallization treatment such as heat treatment after film formation.

  A transistor including a CAAC-OS film can reduce variation in electrical characteristics of the transistor due to irradiation with visible light or ultraviolet light. Further, fluctuations and variations in the threshold value can be suppressed. Therefore, the transistor has high reliability.

  In an oxide semiconductor film having a crystal part or crystallinity, defects in the bulk can be further reduced. Further, by increasing planarity of a crystalline portion or a surface of an oxide semiconductor film having crystallinity, a transistor using the oxide semiconductor film has a higher field-effect mobility than a transistor using an amorphous oxide semiconductor film. Can be obtained. In order to improve the flatness of the surface of the oxide semiconductor film, it is preferable to form the oxide semiconductor film over a flat surface. Specifically, the flat surface roughness (Ra) is preferably 0.15 nm or less, preferably It is good to form on the surface of 0.1 nm or less.

  Ra is a three-dimensional extension of the centerline average roughness defined in Japanese Industrial Standards JIS B0601 so that it can be applied to the surface. “The absolute value of the deviation from the reference surface to the specified surface is It can be expressed as “average value” and is defined by the following formula.

In the above, S ₀ is surrounded by four points represented by the measurement plane (coordinates (x ₁ , y ₁ ) (x ₁ , y ₂ ) (x ₂ , y ₁ ) (x ₂ , y ₂ )). (Rectangular region) indicates the area, and Z ₀ indicates the average height of the measurement surface. Ra can be evaluated with an atomic force microscope (AFM).

  As the oxide semiconductor film, an oxide semiconductor having a forbidden band width larger than 1.1 eV of silicon is preferably used. For example, an In—Ga—Zn-based metal whose forbidden band width is about 3.15 eV is used. Oxide, indium oxide with a forbidden band width of about 3.0 eV, indium tin oxide with a forbidden band width of about 3.0 eV, indium gallium oxide with a forbidden band width of about 3.3 eV, forbidden band width Indium zinc oxide having a band gap of about 2.7 eV, tin oxide having a band gap of about 3.3 eV, zinc oxide having a band gap of about 3.37 eV can be preferably used. By using such a material, the off-state current of the transistor can be kept extremely low.

  The oxide semiconductor used for the oxide semiconductor film preferably contains at least one selected from the group of indium (In), zinc (Zn), and gallium (Ga). In particular, In and Zn are preferably included. In addition, it is preferable to include tin (Sn) as a stabilizer for reducing variation in electric characteristics of the transistor including the oxide semiconductor.

  For example, as an oxide semiconductor, indium oxide, tin oxide, zinc oxide, binary metal oxides such as In—Zn metal oxide, Sn—Zn metal oxide, In—Ga metal oxide, ternary In-Ga-Zn-based metal oxides (also referred to as IGZO), In-Sn-Zn-based metal oxides, Sn-Ga-Zn-based metal oxides, and quaternary metal oxides that are metal-based metal oxides An In—Sn—Ga—Zn-based metal oxide can be used.

  Here, the In—Ga—Zn-based metal oxide means a metal oxide containing In, Ga, and Zn as main components, and the ratio of In, Ga, and Zn does not matter. Moreover, metal elements other than In, Ga, and Zn may be contained.

Alternatively, a material represented by InMO ₃ (ZnO) _m (m> 0 is satisfied, and m is not an integer) may be used as the oxide semiconductor. Note that M represents one metal element or a plurality of metal elements selected from Ga, Fe, Mn, and Co, or the above-described element as a stabilizer. Alternatively, a material represented by In ₂ SnO ₅ (ZnO) _n (n> 0 is satisfied, and n is an integer) may be used as the oxide semiconductor.

  For example, an In—Ga—Zn-based metal having an atomic ratio of In: Ga: Zn = 1: 1: 1, In: Ga: Zn = 3: 1: 2, or In: Ga: Zn = 2: 1: 3 An oxide or an oxide in the vicinity of the composition may be used.

  In the oxide semiconductor film formation step, it is preferable that impurities such as hydrogen and water be contained in the oxide semiconductor film as much as possible. For example, it is preferable to preheat the substrate in a preheating chamber of a sputtering apparatus and desorb and exhaust impurities such as hydrogen and water adsorbed on the substrate as pretreatment for the oxide semiconductor film formation step. The oxide semiconductor film is preferably formed in a film formation chamber (also referred to as a film formation chamber) from which residual water is exhausted.

Note that in order to remove water from the preheating chamber and the film formation chamber, an adsorption-type vacuum pump such as a cryopump, an ion pump, or a titanium sublimation pump is preferably used. The exhaust means may be a turbo pump provided with a cold trap. In the preheating chamber and the film formation chamber exhausted using a cryopump, for example, a compound containing hydrogen atoms such as hydrogen atoms and water (H ₂ O) (more preferably a compound containing carbon atoms) is exhausted. Therefore, the concentration of impurities such as hydrogen and water contained in the oxide semiconductor film can be reduced.

  Note that an In—Ga—Zn-based metal oxide is formed as the oxide semiconductor film by a sputtering method. The oxide semiconductor film can be formed by a sputtering method in a rare gas (typically argon) atmosphere, an oxygen atmosphere, or a mixed atmosphere of a rare gas and oxygen.

  As a target for forming an In—Ga—Zn-based metal oxide by an sputtering method as an oxide semiconductor film, for example, a metal oxide target having an atomic ratio of In: Ga: Zn = 1: 1: 1 A metal oxide target having an atomic ratio of In: Ga: Zn = 3: 1: 2 or a metal oxide target having an atomic ratio of In: Ga: Zn = 2: 1: 3 can be used. Note that targets that can be used for the oxide semiconductor film are not limited to materials and compositions of these targets.

In the case where the oxide semiconductor film is formed using the above-described metal oxide target, the composition of the target may be different from the composition of the thin film formed over the substrate. For example, in the case of using a metal oxide target of In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 1: 1: 1 [mol ratio], the oxide semiconductor film which is a thin film depends on the film formation conditions. The composition ratio may be In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 1: 1: 0.6 to 0.8 [mol ratio]. This is considered to be because ZnO sublimates during the formation of the oxide semiconductor film or the sputtering rates of the components of In ₂ O ₃ , Ga ₂ O ₃ , and ZnO are different.

Therefore, when it is desired to form a thin film having a desired composition ratio, it is necessary to adjust the composition ratio of the metal oxide target in advance. For example, when the composition ratio of the thin oxide semiconductor film is In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 1: 1: 1 [mol ratio], the composition ratio of the metal oxide target is In ₂ O ₃ : Ga ₂ O ₃ : ZnO = 1: 1: 1.5 [molar ratio] may be used. That is, the ZnO content of the metal oxide target may be increased in advance. However, the composition ratio of the target is not limited to the above numerical values, and can be appropriately adjusted depending on the film forming conditions and the composition of the thin film to be formed. Further, increasing the ZnO content of the metal oxide target is preferable because the crystallinity of the resulting thin film is improved.

  The relative density of the metal oxide target is 90% to 100%, preferably 95% to 99.9%. By using a metal oxide target having a high relative density, the formed oxide semiconductor film can be a dense film.

  As a sputtering gas used for forming the oxide semiconductor film, a high-purity gas from which impurities such as hydrogen and water are removed is preferably used.

  In the case where a CAAC-OS film is used as the oxide semiconductor film, for example, there are three methods for forming the CAAC-OS film. First, the oxide semiconductor film is formed at a deposition temperature of 200 ° C. to 450 ° C., so that the c-axis of the crystal part included in the oxide semiconductor film is a normal vector of the surface to be formed or the surface This is a method for forming crystal parts aligned in a direction parallel to the normal vector. Second, after the oxide semiconductor film is formed with a small thickness, heat treatment is performed at 200 ° C. to 700 ° C. so that the c-axis of the crystal part included in the oxide semiconductor film is a method of forming a surface. This is a method of forming a crystal part aligned in a direction parallel to a line vector or a surface normal vector. Third, after forming a thin oxide semiconductor film of the first layer, heat treatment at 200 ° C. to 700 ° C. is performed, and further, a second oxide semiconductor film is formed. In which the c-axis of the crystal part is aligned in a direction parallel to the normal vector of the surface to be formed or the normal vector of the surface.

  In addition, by forming the film while heating the substrate, the concentration of impurities such as hydrogen and water contained in the formed oxide semiconductor film can be reduced. Further, it is preferable because damage due to sputtering is reduced. Alternatively, the oxide semiconductor film may be formed by an ALD (Atomic Layer Deposition) method, an evaporation method, a coating method, or the like.

  Note that in the case where an oxide semiconductor film (single crystal or microcrystal) having crystallinity other than the CAAC-OS film is formed as the oxide semiconductor film, the deposition temperature is not particularly limited.

As a method for processing the oxide semiconductor film, the oxide semiconductor film can be etched by a wet etching method or a dry etching method. BCl ₃ , Cl ₂ , O _2, or the like can be used as an etching gas for the dry etching method. A dry etching apparatus using a high-density plasma source such as ECR (Electron Cyclotron Resonance) or ICP (Inductive Coupled Plasma) can be used to improve the etching rate.

  Further, after the oxide semiconductor film is formed, heat treatment may be performed on the oxide semiconductor film. The temperature of the heat treatment is 300 ° C. or higher and 700 ° C. or lower, or lower than the strain point of the substrate. By performing the heat treatment, excess hydrogen, water, or the like contained in the oxide semiconductor film can be removed. Note that the heat treatment may be referred to as dehydration treatment (dehydrogenation treatment) in this specification and the like.

  The heat treatment can be performed, for example, by introducing an object to be processed into an electric furnace using a resistance heating element and the like under a nitrogen atmosphere at 450 ° C. for one hour. During this time, the oxide semiconductor film is not exposed to the air so that entry of hydrogen, water, or the like does not occur.

  The heat treatment apparatus is not limited to an electric furnace, and an apparatus for heating an object to be processed by heat conduction or heat radiation from a medium such as a heated gas may be used. For example, an RTA (Rapid Thermal Annealing) device such as a GRTA (Gas Rapid Thermal Annealing) device or an LRTA (Lamp Rapid Thermal Annealing) device can be used. The LRTA apparatus is an apparatus that heats an object to be processed by radiation of light (electromagnetic waves) emitted from a lamp such as a halogen lamp, a metal halide lamp, a xenon arc lamp, a carbon arc lamp, a high pressure sodium lamp, or a high pressure mercury lamp. The GRTA apparatus is an apparatus that performs heat treatment using a high-temperature gas. As the gas, an inert gas that does not react with an object to be processed by heat treatment, such as nitrogen or a rare gas such as argon, is used.

  For example, as the heat treatment, a GRTA process may be performed in which an object to be processed is put in a heated inert gas atmosphere, heated for several minutes, and then the object to be processed is taken out from the inert gas atmosphere. When GRTA treatment is used, high-temperature heat treatment can be performed in a short time. In addition, application is possible even under temperature conditions exceeding the heat resistance temperature of the object to be processed. Note that the inert gas may be switched to a gas containing oxygen during the treatment.

  Note that as the inert gas atmosphere, an atmosphere containing nitrogen or a rare gas (such as helium, neon, or argon) as a main component and not containing hydrogen, water, or the like is preferably used. For example, the purity of nitrogen or a rare gas such as helium, neon, or argon introduced into the heat treatment apparatus is 6N (99.9999%) or more, preferably 7N (99.99999%) or more (that is, the impurity concentration is 1 ppm). Hereinafter, preferably 0.1 ppm or less.

  Further, when the above-described dehydration treatment (dehydrogenation treatment) is performed, oxygen that is a main component material included in the oxide semiconductor film may be simultaneously desorbed and reduced. In the oxide semiconductor film, oxygen vacancies exist at locations where oxygen is released, and donor levels that cause fluctuations in electrical characteristics of the transistor are generated due to the oxygen vacancies. Therefore, when dehydration treatment (dehydrogenation treatment) is performed, oxygen is preferably supplied to the oxide semiconductor film. By supplying oxygen into the oxide semiconductor film, oxygen vacancies in the film can be filled.

  As an example of a method for filling oxygen vacancies in an oxide semiconductor film, after dehydration treatment (dehydrogenation treatment) is performed on the oxide semiconductor film, high-purity oxygen gas or oxygen dinitride is supplied to the same furnace. Gas or ultra dry air (CRDS (Cavity Ring Down Laser Spectroscopy) type dew point meter) moisture content when measured using a dew point meter of 20 ppm or less, preferably 1 ppm or less, more preferably 10 ppm The following air) may be introduced. It is preferable that hydrogen, water, or the like be not contained in the oxygen gas or the oxygen dinitride gas. Alternatively, the purity of the oxygen gas or oxygen dinitride gas introduced into the heat treatment apparatus is 6N (99.9999%) or higher, preferably 7N (99.99999%) or higher (that is, in oxygen gas or oxygen dinitride gas). The impurity concentration is preferably 1 ppm or less, and preferably 0.1 ppm or less.

  As an example of a method for supplying oxygen into the oxide semiconductor film, an oxide semiconductor can be obtained by adding oxygen (including at least one of oxygen radicals, oxygen atoms, and oxygen ions) to the oxide semiconductor film. Oxygen may be supplied into the film. As a method for adding oxygen, an ion implantation method, an ion doping method, plasma treatment, or the like can be used.

  As an example of a method for supplying oxygen into the oxide semiconductor film, the base insulating film, the gate insulating film, or the like is heated so that part of oxygen is released and oxygen is supplied to the oxide semiconductor film. May be.

  As described above, after the oxide semiconductor film is formed, dehydration treatment (dehydrogenation treatment) is performed to remove hydrogen, water, and the like from the oxide semiconductor film so that impurities are contained as little as possible. In addition, it is preferable to add oxygen that has been reduced by dehydration treatment (dehydrogenation treatment) to the oxide semiconductor, or supply excess oxygen to fill oxygen vacancies in the oxide semiconductor film. The case where oxygen is supplied to the oxide semiconductor film may be referred to as oxygenation treatment or peroxygenation treatment.

In this manner, an oxide semiconductor film is electrically i-type (intrinsic) by removing hydrogen, water, and the like by dehydration treatment (dehydrogenation treatment) and filling oxygen vacancies by oxygenation treatment. Or a substantially i-type oxide semiconductor film. Specifically, the hydrogen concentration in the oxide semiconductor film is 5 × 10 ¹⁹ atoms / cm ³ or less, preferably 5 × 10 ¹⁸ atoms / cm ³ or less, more preferably 5 × 10 ¹⁷ atoms / cm ³ or less. To do. Note that the hydrogen concentration in the oxide semiconductor film is measured by secondary ion mass spectrometry (SIMS).

As described above, in the oxide semiconductor film in which the hydrogen concentration is sufficiently reduced to be highly purified and the defect level in the forbidden band width caused by the oxygen deficiency is reduced by supplying sufficient oxygen, the oxide semiconductor film is derived from the donor. There are very few carriers (close to zero), and the carrier concentration is less than 1 × 10 ¹² / cm ³ , preferably less than 1 × 10 ¹¹ / cm ³ , and more preferably less than 1.45 × 10 ¹⁰ / cm ³ . In a transistor including such an oxide semiconductor film, for example, an off current at room temperature (25 ° C.) (here, a value per unit channel width (1 μm)) is 100 zA (1 zA (zeptoampere) is 1 × 10 ⁻²¹ A) or less, preferably 10 zA or less, and more preferably 100 yA (1 yA (yokutoampere) is 1 × 10 ⁻²⁴ A) or less. As described above, by using an i-type or substantially i-type oxide semiconductor, a transistor having extremely excellent off-state current characteristics can be obtained.

<Method for Manufacturing Transistor>
A method for manufacturing the transistor 202 illustrated in FIG. 3B will be described with reference to FIGS.

  First, a base insulating film (not shown) is formed over the substrate 301. Next, after a conductive film is formed over the base insulating film, the gate electrode 213 is formed by a photolithography process and an etching process.

  As the substrate 301, a glass material such as aluminosilicate glass, aluminoborosilicate glass, or barium borosilicate glass is preferably used.

  As the base insulating film, for example, silicon oxide, gallium oxide, aluminum oxide, silicon nitride, silicon oxynitride, aluminum oxynitride, silicon nitride oxide, or the like can be used. The base insulating film can be formed by a CVD method, a sputtering method, or the like. By using the above-described silicon nitride film or aluminum oxide film as the base insulating film, impurities that diffuse from the substrate 301 into the transistor 202 can be prevented. Note that the base insulating film may be provided as necessary.

  As the gate electrode 213, a single layer, a metal material such as molybdenum, titanium, tantalum, tungsten, aluminum, copper, neodymium, and scandium, or an alloy material containing at least one of these is formed by a sputtering method or the like. Alternatively, they can be stacked.

  After that, gate insulating films 306 and 307 are formed over the base insulating film and the gate electrode 213.

  As the gate insulating film, for example, silicon oxide, gallium oxide, aluminum oxide, silicon nitride, silicon oxynitride, aluminum oxynitride, silicon nitride oxide, or the like can be used. The thickness of the gate insulating film 108 can be, for example, 10 nm to 500 nm, preferably 50 nm to 300 nm.

The gate insulating film preferably contains oxygen in a portion in contact with the oxide semiconductor film 311 to be formed later. In particular, in the gate insulating film, it is preferable that oxygen in an amount exceeding the stoichiometric composition ratio is present in the film. For example, when silicon oxide is used as the gate insulating film, SiO _{2 + α} (where α > 0). In this embodiment, silicon oxide with SiO _{2 + α} (where α> 0) is used as the gate insulating film. By using this silicon oxide as a gate insulating film, oxygen can be supplied to the oxide semiconductor film 311 to be formed later, and the electrical characteristics of the oxide semiconductor film 311 can be improved.

Other materials for the gate insulating film include hafnium oxide, yttrium oxide, hafnium silicate (HfSi _x O _y (x> 0, y> 0)), and hafnium silicate added with nitrogen (HfSiO _x N _y (x > 0, y> 0)), hafnium aluminate (HfAl _x O _y (x> 0, y> 0)), high-k materials such as lanthanum oxide can be used. By using such a material, gate leakage current can be reduced. Further, the gate insulating film may have a single-layer structure or a stacked structure.

  Next, heat treatment may be performed on the substrate 301 over which the gate insulating films 306 and 307 are formed.

  For example, as the heat treatment, an apparatus for heating an object to be processed by heat conduction or heat radiation from a heating element such as an electric furnace or a resistance heating element can be used. <Detailed Description of Oxide Semiconductor Film> The heat treatment apparatus described in the column can be used as appropriate. Note that an inert gas that does not react with an object to be processed by heat treatment, such as nitrogen or a rare gas such as argon, is used as a high-temperature gas used in the GRTA apparatus or the like. As another example of the high temperature gas, oxygen may be used. By using oxygen, desorption of oxygen from the gate insulating film can be suppressed, or oxygen can be supplied to the gate insulating film.

  As the processing temperature of the heat treatment, when mother glass is used as the substrate 301, the processing temperature is high, and the processing time is long. It is not lower than 350 ° C.

  Note that by performing the heat treatment, impurities such as water and hydrogen contained in the gate insulating films 306 and 307 can be removed. Further, the heat treatment can reduce the defect density in the gate insulating film. By reducing impurities such as hydrogen and water contained in the gate insulating film or defect density in the film, the reliability of the transistor is improved. For example, transistor deterioration in an optical negative bias stress test, which is one of transistor reliability tests, can be suppressed.

  Further, the above heat treatment may be performed as pre-deposition treatment for the oxide semiconductor film 311 to be formed later. For example, the oxide semiconductor film 311 may be formed after the gate insulating film is formed and heat treatment is performed in a vacuum in a preheating chamber of a sputtering apparatus.

  Further, the heat treatment may be performed a plurality of times. For example, after the gate insulating film is formed, heat treatment is performed in a nitrogen atmosphere using an electric furnace or the like, and then heat treatment is performed in vacuum in a preheating chamber of a sputtering apparatus, and then the oxide semiconductor film 311 is formed. May be.

  Next, an oxide semiconductor film is formed over the gate insulating films 306 and 307, and a photolithography step and an etching step are performed, so that the element-isolated oxide semiconductor film 311 is formed.

  The detailed contents, manufacturing method, and the like of the oxide semiconductor film 311 are omitted in the section <Detailed description of oxide semiconductor film>.

  Next, a conductive film was formed over the gate insulating films 306 and 307 and the oxide semiconductor film 311, and the conductive film was electrically connected to the oxide semiconductor film 311 by performing a photolithography process and an etching process. Source and drain electrodes 312a and 312b are formed. Note that the transistor 202 is formed at this stage.

  As the conductive film used for the source and drain electrodes 312a and 312b, for example, a metal film containing an element selected from Al, Cr, Cu, Ta, Ti, Mo, and W, or metal nitridation containing the above-described element as a component A single layer or a stacked layer can be formed using a material film (a titanium nitride film, a molybdenum nitride film, a tungsten nitride film), or the like. Further, a refractory metal film such as Ti, Mo, W or the like or a metal nitride film thereof (a titanium nitride film, a molybdenum nitride film, a tungsten nitride film) on one or both of the lower side or the upper side of a metal film such as Al or Cu. ) May be laminated.

  Next, insulating films 313 and 314 and a planarization film 315 are formed over the transistor 202.

  The insulating films 313 and 314 can be formed using a material and a method similar to those used for the gate insulating film.

  As the planarization film 315, for example, an organic resin material such as polyimide, acrylic, or benzocyclobutene can be used. With the planarization film, unevenness of the transistor 202 can be reduced.

DESCRIPTION OF SYMBOLS 100 Image pick-up apparatus 101 Photo sensor 102 Scintillator 103 X-ray source 104 X-ray 105 Light 106 Spacer 107 Test object (subject)
200 1 pixel 201 photodiode 202, 203, 204 transistor 205, 206, 207, 208, 209, 210 wiring 205a, 205b, 206a, 206b conductive layer 211 photodetection region 212 transparent conductive film 213, 214, 215, 216 conductive layer 217, 218 Wiring 219 Spacer 250 Photodetection region 251 Circuit region 301 Substrate 302 Terminal electrode 303 Transparent conductive film 304 Anisotropic conductive film 305 TCP
306, 307 Insulating films 308, 309, 310 Semiconductor film 311 Oxide semiconductor films 312a, 312b Conductive layers 313, 314 Insulating film 315 Planarizing film 316 Insulating film 317 Transparent conductive film 318 Adhesive layer 319 Scintillator 320 Scintillator protective layer 321 Sealing material 322 Spherical spacers 500, 501, 502 Partition 1200 Image capturing device 1201 Substrate 1202 Scintillator 1203 Pixel area 1204 TCP
1205 Drive IC
1220 Image pickup device 1221 Substrate 1222 Scintillator 1223 Pixel region 1224 FPC
1225 Drive IC
1240 Image pickup device 1241 Substrate 1242 Scintillator 1243 Pixel area 1244 FPC
1245 Drive IC
1246 TCP
1247a, 1247b Scanning drive circuit 1254, 1255a, 1255b Spacer 1300 Image pickup device 1301 Substrate 1302 Scintillator 1303 Pixel area 1304 TCP
1305 Drive IC
1306 Sealing material 1307 Spacers 3001, 3002, 3003, 3004, 3005 Signal

Claims (12)

A scintillator that converts X-rays into light;
A photosensor on which the light converted by the scintillator is incident;
A spacer disposed between the scintillator and the photosensor;
An image pickup apparatus comprising: In claim 1,
The photosensor has a plurality of pixels,
Each of the plurality of pixels includes a photodiode, a first transistor, a second transistor, and a third transistor. In claim 2,
One of a source electrode and a drain electrode of the first transistor is electrically connected to one electrode of the photodiode;
The image pickup device, wherein the first transistor is a thin film transistor using an oxide semiconductor film in a channel formation region. In claim 3,
The other of the source electrode and the drain electrode of the first transistor is electrically connected to the gate electrode of the second transistor;
The image pickup device, wherein the second transistor is formed of a thin film transistor using an oxide semiconductor film in a channel formation region. In claim 4,
One of a source electrode and a drain electrode of the second transistor is electrically connected to one of a source electrode and a drain electrode of the third transistor;
The image pickup device, wherein the third transistor is a thin film transistor using an oxide semiconductor film in a channel formation region. In any one of Claims 2 thru | or 5,
The image pickup device, wherein the photodiode, the first transistor, the second transistor, the third transistor, and the spacer are formed on a substrate. In any one of Claims 2 thru | or 6,
The image pickup apparatus according to claim 1, wherein one spacer is arranged for one or two of the pixels. In any one of Claims 2 thru | or 6,
The plurality of pixels are formed in a pixel region,
The image pickup apparatus, wherein the spacer is formed in at least one of the pixel region and the outside of the pixel region. In any one of Claims 2 thru | or 6,
The image pickup apparatus, wherein the spacer is formed so as to completely or partially surround each of the photodiodes. In any one of Claims 3 thru | or 5,
The image pickup apparatus, wherein the oxide semiconductor film is a film containing an oxide of one or more elements selected from indium, zinc, gallium, and tin. In any one of Claim 3 thru | or 5 and Claim 10,
The oxide semiconductor film includes a crystal part,
The image pickup device according to claim 1, wherein the crystal part has a c-axis aligned in a direction parallel to a normal vector of a surface where the oxide semiconductor film is formed. In any one of Claims 1 thru | or 11,
An image pickup apparatus, wherein an interval between the scintillator and the photosensor is 0.1 μm or more and 10 μm or less.

Images