Imaging device

Abstract

To provide an imaging device capable of performing image processing.SOLUTION: An imaging device has additional functions, such as an image recognition function. The imaging device has a function of acquiring imaging data by cells arranged in a matrix and a function of retaining weight data. Some cells of the cells arranged in a matrix acquire the image data and the remaining cells retain the weight data. The imaging device performs calculation using the imaging data and the weight data. For example, the imaging device can calculate the product of the imaging data and the weight data for all pieces of imaging data and sum up the calculated products, that is, perform a product-sum operation. Since image processing can be carried out on the imaging data by the operation result being incorporated into a neural network, such as a convolutional neural network (CNN), the additional functions are available.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] One embodiment of the present invention relates to an imaging device and an electronic device.

[0002] Note that one embodiment of the present invention is not limited to the above technical field. The technical field of one embodiment of the invention disclosed in this specification etc. relates to an object, a method, or a manufacturing method. Alternatively, one embodiment of the present invention relates to a process, a machine, a manufacture, or a composition of matter. Therefore, more specifically, examples of the technical field of one embodiment of the present invention disclosed in this specification include a semiconductor device, a display device, a liquid crystal display device, a light-emitting device, a lighting device, a power storage device, a memory device, an imaging device, a driving method thereof, or a manufacturing method thereof.

[0003] Note that in this specification and the like, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics. A transistor and a semiconductor circuit are one embodiment of a semiconductor device. Further, a memory device, a display device, an imaging device, and an electronic device may include a semiconductor device. [Background technology]

[0004] A technology for forming a transistor using an oxide semiconductor thin film formed over a substrate has attracted attention. For example, Patent Document 1 discloses an imaging device in which a transistor that includes an oxide semiconductor and has an extremely low off-state current is used in a pixel circuit.

[0005] Moreover, Patent Document 2 discloses a technique for adding a calculation function to an imaging device. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2011-119711 A [Patent Document 2] JP 2016-123087 A Summary of the Invention [Problem to be solved by the invention]

[0007] With the advancement of technology, imaging devices equipped with solid-state imaging elements such as CMOS image sensors can easily capture high-quality images. In the next generation, imaging devices are expected to be equipped with various additional functions, such as image recognition functions, by performing image processing on captured images.

[0008] Therefore, an object of one embodiment of the present invention is to provide an imaging device capable of performing image processing. Another object is to provide an imaging device with low power consumption. Another object is to provide an imaging device that can be driven at high speed. Another object is to provide a small imaging device. Another object is to provide an imaging device with high reliability. Another object is to provide an imaging device with high light detection sensitivity. Another object is to provide a novel imaging device or the like. Another object is to provide a driving method of the imaging device or the like. Another object is to provide a novel semiconductor device or the like.

[0009] Note that the description of these problems does not preclude the existence of other problems. Note that one embodiment of the present invention does not necessarily solve all of these problems. Note that problems other than these will become apparent from the description of the specification, drawings, claims, etc., and it is possible to extract problems other than these from the description of the specification, drawings, claims, etc. [Means for solving the problem]

[0010] One embodiment of the present invention is an imaging device that includes a cell array in which a plurality of cells are arranged in a matrix, and a logic circuit, where the cell has a photoelectric conversion element and has a function of acquiring imaging data using the photoelectric conversion element and a function of holding weighting data, and the logic circuit has a function of performing a calculation using the imaging data acquired by the cell and weighting data held in a cell other than the cell that acquired the imaging data.

[0011] Alternatively, in the above aspect, the logic circuit may have a function of calculating a product of the imaging data and the weighting data.

[0012] Alternatively, one embodiment of the present invention is an imaging device including a cell array in which a plurality of cells are arranged in a matrix and a logic circuit, each of which has a photoelectric conversion element and has a function of acquiring imaging data by using the photoelectric conversion element and a function of holding weighting data, and the logic circuit has a function of performing calculations using the first imaging data, the second imaging data, the first weighting data, and the second weighting data when a first cell acquires the first imaging data, a second cell acquires the second imaging data, a third cell holds the first weighting data, and a fourth cell holds the second weighting data among the plurality of cells.

[0013] Alternatively, in the above aspect, the logic circuit may have a function of calculating the sum of the product of the first imaging data and the first weighting data and the product of the second imaging data and the second weighting data.

[0014] Alternatively, in the above-mentioned aspect, the imaging device has a readout circuit, the cell has a first transistor, a second transistor, a third transistor, and a fourth transistor, one electrode of the photoelectric conversion element is electrically connected to one of a source or a drain of the first transistor, the other of the source or the drain of the first transistor is electrically connected to one of a source or a drain of the second transistor, one of the source or the drain of the second transistor is electrically connected to a gate of the third transistor, and one of the source or the drain of the third transistor is electrically connected to a source or the other of the source or drain of the third transistor is electrically connected to a logic circuit, the other of the source or drain of the fourth transistor is electrically connected to a readout circuit, the cell has a function of holding weight data supplied via the source and drain of the second transistor, the cell has a function of outputting imaging data from the other of the source or drain of the third transistor or the other of the source or drain of the fourth transistor, and the cell has a function of outputting weight data from the other of the source or drain of the third transistor.

[0015] Alternatively, in the above aspect, the cell may have a function of outputting imaging data as binary data from the other of the source or drain of the third transistor, and the cell may have a function of outputting weighting data as binary data from the other of the source or drain of the third transistor.

[0016] Alternatively, in the above embodiment, the first transistor and the second transistor may have a metal oxide in a channel formation region, and the metal oxide may have In, Zn, and M (M is Al, Ti, Ga, Ge, Sn, Y, Zr, La, Ce, Nd, or Hf).

[0017] Alternatively, in the above embodiment, a colored layer may be provided, and at least one of the first to fourth transistors, the photoelectric conversion element, and the colored layer may have an overlapping region, and the colored layer may have a function of a microlens.

[0018] Alternatively, in the above embodiment, the logic circuit may include a fifth transistor, and the fifth transistor, at least one of the first to fourth transistors, the photoelectric conversion element, and the colored layer may have regions overlapping with each other.

[0019] Alternatively, in the above aspect, the imaging device includes a readout circuit and an A / D conversion circuit, the cell includes a first transistor, a second transistor, a third transistor, a fourth transistor, and a fifth transistor, one electrode of the photoelectric conversion element is electrically connected to one of a source or a drain of the first transistor, the other of the source or the drain of the first transistor is electrically connected to one of a source or a drain of the second transistor, one of the source or the drain of the second transistor is electrically connected to a gate of the third transistor, one of the source or the drain of the third transistor is electrically connected to one of a source or a drain of the fourth transistor, and one of the source or the drain of the fourth transistor is electrically connected to one of a source or a drain of the fifth transistor. the other of the source or drain of the third transistor is electrically connected to a readout circuit, one of the source or drain of the fifth transistor is electrically connected to an A / D conversion circuit, the A / D conversion circuit is electrically connected to a logic circuit, a first potential is supplied to the other of the source or drain of the third transistor, and a second potential is supplied to the other of the source or drain of the fifth transistor, the cell has a function of retaining weight data supplied via the source and drain of the second transistor, the cell has a function of outputting imaging data from one of the source or drain of the third transistor or the other of the source or drain of the fourth transistor, and the cell has a function of outputting weight data from one of the source or drain of the third transistor.

[0020] Alternatively, in the above embodiment, the first transistor and the second transistor may have a metal oxide in a channel formation region, and the metal oxide may have In, Zn, and M (M is Al, Ti, Ga, Ge, Sn, Y, Zr, La, Ce, Nd, or Hf).

[0021] Alternatively, in the above embodiment, a colored layer may be provided, and at least one of the first to fifth transistors, the photoelectric conversion element, and the colored layer may have an overlapping region, and the colored layer may have a function of a microlens.

[0022] Alternatively, in the above embodiment, the logic circuit may include a sixth transistor, and the sixth transistor, at least one of the first to fifth transistors, the photoelectric conversion element, and the colored layer may have regions overlapping with each other.

[0023] An electronic device including the imaging device of one embodiment of the present invention and a display portion is also one embodiment of the present invention. Effect of the Invention

[0024] By using one embodiment of the present invention, an imaging device capable of performing image processing can be provided. Alternatively, an imaging device with low power consumption can be provided. Alternatively, an imaging device that can be driven at high speed can be provided. Alternatively, a small-sized imaging device can be provided. Alternatively, an imaging device with high reliability can be provided. Alternatively, an imaging device with high light detection sensitivity can be provided. Alternatively, a novel imaging device or the like can be provided. Alternatively, a driving method of the imaging device or the like can be provided. Alternatively, a novel semiconductor device or the like can be provided.

[0025] The effects of one embodiment of the present invention are not limited to the effects listed above. The effects listed above do not preclude the existence of other effects. The other effects are effects not mentioned in this section, which will be described below. Effects not mentioned in this section can be derived by a person skilled in the art from descriptions in the specification, drawings, etc., and can be appropriately extracted from these descriptions. One embodiment of the present invention has at least one of the effects listed above and / or other effects. Therefore, one embodiment of the present invention may not have the effects listed above, depending on the circumstances. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a block diagram illustrating an example of the configuration of an imaging apparatus. [Diagram 2] 2A and 2B are circuit diagrams illustrating examples of the configuration of a cell. [Diagram 3] FIG. 3 is a circuit diagram illustrating an example of the configuration of the arithmetic circuit. [Figure 4] 4A and 4B are diagrams for explaining an example of the calculation. [Diagram 5] 5A and 5B are diagrams for explaining an example of the calculation. [Figure 6] FIG. 6 is a diagram for explaining an example of the calculation. [Figure 7] FIG. 7 is a circuit diagram illustrating an example of the configuration of an imaging device. [Figure 8] FIG. 8 is a timing chart illustrating an example of a method for driving the imaging device. [Figure 9] FIG. 9 is a diagram illustrating an example of a method for driving the imaging device. [Figure 10] FIG. 10 is a timing chart illustrating an example of a method for driving the imaging device. [Figure 11] FIG. 11 is a circuit diagram illustrating an example of a method for driving the imaging device. [Figure 12] 12A and 12B are circuit diagrams illustrating examples of the configuration of a cell. [Figure 13]FIG. 13 is a circuit diagram illustrating an example of the configuration of the arithmetic circuit. [Figure 14] FIG. 14 is a circuit diagram illustrating an example of the configuration of an imaging device. [Figure 15] FIG. 15 is a timing chart illustrating an example of a method for driving the imaging device. [Figure 16] FIG. 16 is a timing chart illustrating an example of a method for driving the imaging device. [Figure 17] 17A and 17B are circuit diagrams illustrating an example of a method for driving an imaging device. [Figure 18] 18A to 18E are perspective views for explaining configuration examples of an imaging device. [Figure 19] 19A and 19B are cross-sectional views for explaining a configuration example of an imaging device. [Figure 20] 20A to 20C are cross-sectional views illustrating examples of the configuration of an imaging device. [Figure 21] 21A and 21B are cross-sectional views illustrating an example of the configuration of an imaging device. [Figure 22] 22A to 22D are cross-sectional views for explaining configuration examples of an imaging device. [Diagram 23] 23A to 23C are perspective views for explaining configuration examples of an imaging device. [Figure 24] 24A and 24B are cross-sectional views for explaining a configuration example of an imaging device. [Diagram 25] 25A and 25B are cross-sectional views for explaining a configuration example of an imaging device. [Figure 26] 26A and 26B are cross-sectional views for explaining a configuration example of an imaging device. [Figure 27] 27A and 27B are cross-sectional views for explaining a configuration example of an imaging device. [Figure 28] 28A and 28B are perspective views for explaining a configuration example of an imaging device. [Figure 29]Fig. 29A is a diagram for explaining the classification of IGZO crystal structures, Fig. 29B is a diagram for explaining the XRD spectrum of a CAAC-IGZO film, and Fig. 29C is a diagram for explaining the ultrafine electron beam diffraction pattern of a CAAC-IGZO film. [Diagram 30] 30A1 to 30B3 are perspective views of a package and a module that house an imaging device. [Diagram 31] 31A to 31F are diagrams illustrating an electronic device. [Diagram 32] 32A and 32B are diagrams illustrating an automobile. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] The embodiments 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 the form and details of the present invention can be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the present invention is not interpreted as being limited to the description of the embodiments shown below. In the configuration of the invention described below, the same reference numerals are used in common between different drawings for the same parts or parts having similar functions, and repeated explanations may be omitted. In addition, hatching of the same elements constituting the drawings may be omitted or changed as appropriate between different drawings.

[0028] In addition, even if a circuit diagram shows a single element, the element may be configured as a plurality of elements as long as there is no functional problem. For example, a plurality of transistors operating as a switch may be connected in series or parallel. A capacitor may also be divided and placed in multiple positions.

[0029] In addition, one conductor may have multiple functions such as wiring, an electrode, and a terminal, and in this specification, multiple names may be used for the same element. Even if elements are shown as being directly connected to each other on a circuit diagram, the elements may actually be connected to each other via multiple conductors, and in this specification, such a configuration is also included in the category of direct connection.

[0030] (Embodiment 1) In this embodiment, an imaging device which is one embodiment of the present invention will be described.

[0031] One aspect of the present invention is an imaging device with additional functions such as an image recognition function. In the imaging device, pixels arranged in a matrix have a function of acquiring imaging data and a function of holding weight data. Of the pixels arranged in a matrix, some pixels acquire imaging data, and the remaining pixels hold the weight data. Then, a calculation is performed using the imaging data and the weight data. For example, a calculation can be performed in which the product of the imaging data and the weight data is calculated for all imaging data, and the calculated products are summed up. In other words, a product-sum calculation can be performed. By inputting the calculation result into a neural network such as a convolutional neural network (CNN), image processing can be performed on the imaging data, and the additional function can be used.

[0032] <Image capture device configuration example_1> FIG 1 is a block diagram illustrating a configuration example of an imaging device 10 which is an imaging device according to one embodiment of the present invention. In the imaging device 10, cells 12 are arranged in a matrix of m rows and n columns (m and n are integers equal to or greater than 1) to form a cell array 11. The imaging device 10 also includes a row driver circuit 13, a data generation circuit 14, a readout circuit 16, an arithmetic circuit 17, and a transistor 27. Note that each circuit illustrated in FIG 1 is not limited to a single circuit configuration, and may be configured with a plurality of circuits. Alternatively, any of the above circuits may be integrated.

[0033] In this specification and the like, for example, the cell 12 in the first row and first column is described as cell 12[1,1], and the cell 12 in the mth row and nth column is described as cell 12[m,n].

[0034] The row driver circuit 13 is electrically connected to the cell 12 via the wiring 35. Here, for example, the cells 12 in the same row can be electrically connected to the row driver circuit 13 via the same wiring 35. In this specification, for example, the wiring 35 electrically connected to the cell 12 in the first row is described as wiring 35[1], the wiring 35 electrically connected to the cell 12 in the second row is described as wiring 35[2], and the wiring 35 electrically connected to the cell 12 in the mth row is described as wiring 35[m]. Note that similar descriptions may be used for other wirings, etc.

[0035] The data generation circuit 14 is electrically connected to the cell 12 via the wiring 43. Here, for example, the cells 12 in the same column can be electrically connected to the data generation circuit 14 via the same wiring 43. In this specification, for example, the wiring 43 electrically connected to the cell 12 in the first column is described as wiring 43[1], the wiring 43 electrically connected to the cell 12 in the second column is described as wiring 43[2], and the wiring 43 electrically connected to the cell 12 in the nth column is described as wiring 43[n]. Note that similar descriptions may be used for other wirings.

[0036] The readout circuit 16 is electrically connected to the cells 12 via wiring 45. Here, for example, the cells 12 in the same column can be electrically connected to the readout circuit 16 via the same wiring 45.

[0037] The arithmetic circuit 17 is electrically connected to the cells 12 via wiring 44. Here, for example, each cell 12 can be electrically connected to a different wiring 44. In this specification, for example, the wiring 44 electrically connected to the cell 12[1,1] is described as wiring 44[1,1], and the wiring 44 electrically connected to the cell 12[m,n] is described as wiring 44[m,n]. Note that similar descriptions may be used for other wirings.

[0038] One of the source and the drain of the transistor 27 is electrically connected to the wiring 45. The other of the source and the drain of the transistor 27 is electrically connected to the wiring 47. The gate of the transistor 27 is electrically connected to the wiring 37. Here, for example, the transistor 27 electrically connected to the wiring 45[1] is referred to as the transistor 27[1], the transistor 27 electrically connected to the wiring 45[2] is referred to as the transistor 27[2], and the transistor 27 electrically connected to the wiring 45[n] is referred to as the transistor 27[n].

[0039] The wiring 47 functions as a power supply line. For example, a low potential can be supplied to the wiring 47. The wiring 37 functions as a signal line that controls the conduction / non-conduction of the transistor 27.

[0040] The cell 12 has a photoelectric conversion element and has a function of acquiring imaging data using the photoelectric conversion element. That is, the cell 12 has a function as a pixel. In addition, the cell 12 has a function of holding weight data generated by the data generation circuit 14, which will be described in detail later. Thus, the cell 12 has a function as a memory.

[0041] In this specification and the like, the term “element” may be replaced with the term “device.” For example, a “photoelectric conversion element” may be replaced with a “photoelectric conversion device.”

[0042] The row driver circuit 13 has a function of selecting the cell 12. The row driver circuit 13 has a function of selecting the cell 12 from which imaging data is to be read, for example. The row driver circuit 13 has a function of selecting the cell 12 by, for example, generating a selection signal and supplying the generated selection signal to the cell 12 via a wiring 35. Thus, the wiring 35 functions as a signal line.

[0043] The data generation circuit 14 has a function of generating weight data. The generated weight data is supplied to the cell 12 via the wiring 43 and held therein. Specifically, the weight data is supplied to the cell 12 from which imaging data has not been acquired and held therein. The data generation circuit 14 also has a function of generating reset data, which is data to be supplied to the cell 12 when the cell 12 performs a reset operation before an imaging operation, and supplying the reset data to the cell 12 via the wiring 43. As described above, the wiring 43 functions as a data line.

[0044] The readout circuit 16 has a column driver circuit. The column driver circuit has a function of selecting a cell 12 from which imaging data is to be read out. The readout circuit 16 may also have a correlated double sampling circuit (CDS circuit), an analog-to-digital conversion circuit (A / D conversion circuit), and the like. Here, imaging data output from the cell 12 to a wiring 45 is supplied to the readout circuit 16. Thus, the wiring 45 functions as an output line.

[0045] The arithmetic circuit 17 has a function of performing calculations using the imaging data and weighting data. As described above, image processing can be performed by inputting the calculation results into a neural network such as CNN. Details of the calculations performed by the arithmetic circuit 17 will be described later. Here, the imaging data and weighting data output from the cell 12 to the wiring 44 are supplied to the arithmetic circuit 17. Therefore, the wiring 44 functions as an output line.

[0046] The imaging device 10 can be driven in a first mode or a second mode. In the first mode, for example, all the cells 12 acquire imaging data and output the acquired imaging data to the readout circuit 16. On the other hand, in the second mode, some of the cells 12 acquire imaging data and the remaining cells 12 hold weight data. Then, the imaging data and weight data are output to the arithmetic circuit 17.

[0047] As described above, in the first mode, the imaging data is output to the outside of the imaging device 10 without performing an operation using the weight data generated by the data generation circuit 14. Therefore, the first mode is a mode in which the additional function is not used. On the other hand, in the second mode, image processing is performed by performing an operation using the imaging data and the weight data. Therefore, the second mode is a mode in which the additional function is used. In the first mode, for example, all the cells 12 are used to obtain the imaging data, so that the additional function cannot be used, but instead the resolution of the image represented by the imaging data can be made higher than the resolution of the image represented by the imaging data in the second mode. In the first mode, the operation circuit 17 can be stopped from driving. In the second mode, the readout circuit 16 can be stopped from driving.

[0048] 2A is a circuit diagram showing an example of the configuration of the cell 12. The cell 12 includes a photoelectric conversion element 21, a transistor 22, a transistor 23, a transistor 24, a transistor 25, and a transistor .

[0049] One electrode of the photoelectric conversion element 21 is electrically connected to one of the source and drain of the transistor 22. The other of the source and the drain of the transistor 22 is electrically connected to one of the source and the drain of the transistor 23. The one of the source and the drain of the transistor 23 is electrically connected to the gate of the transistor 24. The one of the source and the drain of the transistor 24 is electrically connected to one of the source and the drain of the transistor 25.

[0050] The other electrode of the photoelectric conversion element 21 is electrically connected to a wiring 41. The gate of the transistor 22 is electrically connected to a wiring 32. The other of the source and the drain of the transistor 23 is electrically connected to a wiring 43. The gate of the transistor 23 is electrically connected to a wiring 33. The other of the source and the drain of the transistor 24 and the one of the source and the drain of the transistor 26 are electrically connected to a wiring 44. The other of the source and the drain of the transistor 25 is electrically connected to a wiring 45. The gate of the transistor 25 is electrically connected to a wiring 35. The other of the source and the drain of the transistor 26 is electrically connected to a wiring 46. The gate of the transistor 26 is electrically connected to a wiring 36.

[0051] 2A, one electrode of the photoelectric conversion element 21 is an anode, and the other electrode of the photoelectric conversion element 21 is a cathode. Thus, in FIG. 2A, the anode of the photoelectric conversion element 21 is electrically connected to one of the source or drain of the transistor 22, and the cathode of the photoelectric conversion element 21 is electrically connected to the wiring 41.

[0052] Here, the electrical connection point between the other of the source or the drain of the transistor 22, the one of the source or the drain of the transistor 23, and the gate of the transistor 24 is referred to as a node FD.

[0053] The wiring 41 and the wiring 46 function as power supply lines. For example, a high potential can be supplied to the wiring 41 and the wiring 46. Furthermore, signals for controlling the conduction / non-conduction of each transistor are supplied to the wiring 32, the wiring 33, and the wiring 36. Thus, the wiring 32, the wiring 33, and the wiring 36 function as signal lines.

[0054] The photoelectric conversion element 21 has a function of acquiring imaging data. A photodiode can be used as the photoelectric conversion element 21. When it is desired to increase the light detection sensitivity in low illuminance conditions, it is preferable to use an avalanche photodiode.

[0055] The transistor 22 has a function of controlling transfer of charge accumulated in the photoelectric conversion element 21 to the node FD in accordance with illuminance of light irradiated to the photoelectric conversion element 21. Thus, the transistor 22 functions as a transfer transistor.

[0056] The transistor 23 has a function of controlling supply to the node FD of the reset data and a potential corresponding to the weight data generated by the data generation circuit 14. Thus, the transistor 23 functions as a reset transistor.

[0057] The transistor 24 has a function of setting the potential of the wiring 44 or the wiring 45 to a potential corresponding to the potential of the node FD. As a result, the imaging data acquired by the cell 12 is read out through the wiring 44 or the wiring 45, and the weight data held in the cell 12 is read out through the wiring 44. Here, the imaging data or the weight data held in the cell 12 is amplified by the transistor 24 and output. Thus, the transistor 24 functions as an amplifying transistor.

[0058] The transistor 25 has a function of controlling the selection of the cell 12 that outputs imaging data to the readout circuit 16. Thus, the transistor 25 functions as a selection transistor.

[0059] The transistor 26 has a function of controlling the potential of the wiring 44. When the transistor 26 is turned on, the potential of the wiring 44 becomes a potential that corresponds to the potential of the wiring 46. This allows the wiring 44 to be precharged. Thus, the transistor 26 has a function of controlling the precharge of the wiring 44. Thus, the transistor 26 functions as a precharge transistor.

[0060] In this specification and the like, a transistor being in a conductive state or being in an on state means that a current flows between the drain and source of the transistor. For example, the transistor can be made conductive by setting the difference between the gate potential and the source potential of the transistor to be equal to or higher than the threshold voltage of the transistor. Furthermore, a transistor being in a non-conductive state or being in an off state means that no current flows between the drain and source of the transistor. The transistor can be made non-conductive by setting the difference between the gate potential and the source potential of the transistor to be less than the threshold voltage of the transistor.

[0061] Here, it is preferable to use transistors with extremely small off-state current for the transistors 22 and 23. This allows the node FD to hold charge for an extremely long period of time. This allows the cell 12 to hold the imaging data and the weight data for a long period of time. Since the cell 12 can hold the weight data for a long period of time, the frequency of the refresh operation can be reduced. This allows the power consumption of the imaging device 10 to be reduced. Furthermore, since the cell 12 can hold the imaging data for a long period of time, a global shutter method in which charge accumulation operation is performed simultaneously in all the cells 12 can be applied without complicating the circuit configuration or driving method. Furthermore, while holding the imaging data in the node FD, it is also possible to perform multiple calculations using the imaging data. As a transistor with extremely small off-state current, a transistor using a metal oxide in a channel formation region (hereinafter, referred to as an OS transistor) can be given.

[0062] In addition, an OS transistor has a characteristic of high withstand voltage. When an avalanche photodiode is used as the photoelectric conversion element 21, a high voltage may be applied, so that it is preferable to use a high-withstand-voltage transistor as the transistor connected to the photoelectric conversion element 21. Therefore, when an avalanche photodiode is used as the photoelectric conversion element 21, it is preferable to use an OS transistor as the transistor 22.

[0063] Here, when the transistors 22 and 23 are OS transistors, the transistors 24 to 26 are also preferably OS transistors. By using the same type of transistors for the transistors 22 to 26, all the transistors included in the cell 12 can be formed in the same process. In this manner, the imaging device 10 can be manufactured by a simple method.

[0064] Note that the transistors 22 to 26 may be transistors other than OS transistors. For example, it is preferable to use transistors using silicon for a channel formation region (hereinafter, Si transistors) as the transistors 22 to 26. For example, when transistors using single crystal silicon for a channel formation region are used as the transistors 22 to 26, the on-state current of the transistors 22 to 26 is large. Thus, the imaging device 10 can be driven at high speed.

[0065] Fig. 2B is a circuit diagram showing a configuration example of the cell 12, which is a modified example of the configuration shown in Fig. 2A. The cell 12 shown in Fig. 2B differs from the cell 12 shown in Fig. 2A in that the cathode of the photoelectric conversion element 21 is electrically connected to one of the source and drain of the transistor 22, and the anode of the photoelectric conversion element 21 is electrically connected to the wiring 41. In the cell 12 shown in Fig. 2B, the potential of the wiring 41 can be set to a low potential.

[0066] Fig. 3 is a circuit diagram showing a configuration example of the arithmetic circuit 17. The arithmetic circuit 17 includes a logic circuit 51 and transistors 52[1,1] to 52[p,q] (p and q are integers of 1 or more). Note that in the arithmetic circuit 17 of Fig. 3, the transistors 52 are arranged in a p x q matrix.

[0067] An input terminal of the logic circuit 51 is electrically connected to the wirings 44[1,1] to 44[m,n]. An output terminal of the logic circuit 51 is electrically connected to one of the sources or drains of the transistors 52[1,1] to 52[p,q]. Here, the logic circuit 51 can have, for example, m×n input terminals, each of which is electrically connected to a different wiring 44. The logic circuit 51 can have, for example, p×q output terminals, each of which is electrically connected to a different transistor 52.

[0068] For example, the other of the sources or the drains of the transistors 52 in the same column can be electrically connected to each other. For example, the other of the sources or the drains of the transistors 52[1,1] to 52[p,1] located in the first column can be electrically connected to each other, and the other of the sources or the drains of the transistors 52[1,q] to 52[p,q] located in the qth column can be electrically connected to each other.

[0069] The gate of the transistor 52 is electrically connected to a wiring 53. Here, for example, the gates of the transistors 52 in the same row can be electrically connected to each other through the same wiring 53. A signal that controls the conduction / non-conduction of the transistor 52 is supplied to the wiring 53. Thus, the wiring 53 functions as a signal line.

[0070] The logic circuit 51 has a function of performing logical operations using the imaging data and weight data output from the cell 12. The logic circuit 51 has a function of performing logical operations using digital data. The operation result can be represented by a matrix of p rows and q columns, for example, and data representing each element of the matrix is ​​output from the output terminal of the logic circuit 51.

[0071] The transistor 52 has a function of controlling the reading of the calculation result by the logic circuit 51. For example, it is assumed that the logic circuit 51 outputs a matrix with p rows and q columns as the calculation result. In this case, when the transistor 52[1,1] is made conductive, the component in the 1st row and 1st column can be read out, and when the transistor 52[p,q] is made conductive, the component in the pth row and qth column can be read out.

[0072] It is preferable to use Si transistors as the transistors in the logic circuit 51 and the transistor 52. For example, it is preferable to use transistors using single crystal silicon for their channel formation regions as the transistors in the logic circuit 51 and the transistor 52. As described above, a transistor using single crystal silicon for its channel formation region has a large on-state current. Therefore, when a transistor using single crystal silicon for its channel formation region is used as the transistor in the logic circuit 51, the logic circuit 51 can perform calculations at high speed. In addition, when a transistor using single crystal silicon for its channel formation region is used as the transistor 52, the calculation results by the logic circuit 51 can be read at high speed. Note that a transistor using amorphous silicon, microcrystalline silicon, or polycrystalline silicon for its channel formation region may be used as the Si transistor.

[0073] <Example of calculation> 4A, 4B, 5A, and 5B are diagrams showing an example of data held in the cell 12 and an example of a calculation performed by the logic circuit 51. Here, imaging data is indicated by "x" and weighting data is indicated by "w." In addition, a number is added to "x" to distinguish different imaging data, and an alphanumeric character is added to "w" to distinguish different weighting data.

[0074] 4A, 4B, 5A, and 5B show cells 12[1,1] to 12[6,12], and the cells 12 in which imaging data is held are hatched. In Fig. 4A, 4B, 5A, and 5B, of the four cells 12, one cell 12 holds imaging data, and three cells 12 hold weighting data. Specifically, the cell 12 in the odd-numbered row and odd-numbered column holds imaging data, and the other cells 12 hold weighting data.

[0075] In FIG. 4A, imaging data x 11 or image data x 33 The figure shows how convolution data Ca1 is obtained by performing a product-sum operation between the image data x 11 or image data x 33 The convolution data Cb1 is obtained by performing a product-sum operation between the image data x 11 or image data x 33 13 shows how convolution data Cc1 is obtained by performing a product-sum operation between weight data wc1 through wc9 and weight data wc1 through wc9.

[0076] In FIG. 4B, the imaging data x 12 or image data x 34 The figure shows how convolution data Ca2 is obtained by performing a product-sum operation between the image data x 12 or image data x 34 The convolution data Cb2 is obtained by performing a product-sum operation between the image data x 12 or image data x 34 13 shows how convolution data Cc2 is obtained by performing a product-sum operation between weight data wc1 through wc9 and weight data wc1 through wc9.

[0077] As shown in FIG. 4B, when acquiring the convolution data Ca2, for example, the imaging data x12 and the weight data wa1 are calculated. Here, the weight data wa1 is stored in the cell 12[1,8] as well as the cell 12[1,2]. However, the cell 12[1,2] has a higher weight than the image data x 12 The weight data wa1 held in cell 12[1,2] has coordinates close to those of cell 12[1,3] in which the convolution data Ca2 is held. Therefore, using the weight data wa1 held in cell 12[1,8] when acquiring the convolution data Ca2 is preferable because the delay time can be reduced compared to when the weight data wa1 held in cell 12[1,8] is used. Similarly, using the weight data wc1 held in cell 12[2,2] when acquiring the convolution data Cc2 is preferable because the delay time can be reduced compared to when the weight data wc1 held in cell 12[2,8] is used. The same can be said about other weight data used when acquiring the convolution data Ca2, the convolution data Cb2, or the convolution data Cc2.

[0078] In FIG. 5A, imaging data x 13 or image data x 35 The figure shows how convolution data Ca3 is obtained by performing a product-sum operation between the image data x 13 or image data x 35 The convolution data Cb3 is obtained by performing a product-sum operation between the image data x 13 or image data x 35 13 shows how convolution data Cc3 is obtained by performing a product-sum operation between weight data wc1 through wc9 and weight data wc1 through wc9.

[0079] In FIG. 5B, the imaging data x 14 or image data x 36 The figure shows how convolution data Ca4 is obtained by performing a product-sum operation between the image data x 14 or image data x 36The convolution data Cb4 is obtained by performing a product-sum operation between the image data x 14 or image data x 36 13 shows how convolution data Cc4 is obtained by performing a product-sum operation between weight data wc1 through wc9 and weight data wc1 through wc9.

[0080] In the above manner, the product-sum operation is performed to obtain convolution data. In the examples shown in Fig. 4A, Fig. 4B, Fig. 5A, and Fig. 5B, a convolution operation (product-sum operation) with a stride of 1 can be performed using three types of 3x3 filters. Note that the stride can be set to 2 by performing the operation shown in Fig. 5A without performing the operation shown in Fig. 4B, for example, after performing the operation shown in Fig. 4A.

[0081] Here, if the same weight data is held in a plurality of cells 12, it is possible to prevent the coordinates of the cell 12 holding the imaging data from becoming distant from the coordinates of the cell 12 holding the weight coefficient by which the imaging data is multiplied, as shown in Fig. 4B for example. This makes it possible to prevent the delay time from becoming long, and therefore allows the logic circuit 51 to perform calculations at high speed. On the other hand, by reducing the number of cells 12 holding the same weight data, it is possible to increase the number of types of filters that can be used, for example, in a convolution calculation.

[0082] FIG. 6 is a diagram showing an example of data held in the cells 12 and an example of an operation performed by the logic circuit 51 when the number of the cells 12 holding each weight data is half that of the examples shown in FIG. 4A, FIG. 4B, FIG. 5A, and FIG. 5B. In the examples shown in FIG. 4A, FIG. 4B, FIG. 5A, and FIG. 5B, two cells 12 among the cells 12[1,1] to the cells 12[6,12] hold one type of weight data. On the other hand, in the example shown in FIG. 6, one cell 12 among the cells 12[1,1] to the cells 12[6,12] holds one type of weight data. Therefore, in the example shown in FIG. 6, the cells 12 can hold the weight data Wa1 to Wa9, the weight data Wb1 to Wb9, the weight data Wc1 to Wc9, the weight data Wd1 to Wd9, the weight data We1 to We9, and the weight data Wf1 to Wf9. In other words, 54 types of weight data can be stored in the cell 12. As a result, for example, a convolution operation using six types of 3×3 filters can be performed. 11 or image data x 33 When performing a convolution operation using the above, as shown in Fig. 6, in addition to the convolution data Ca1, the convolution data Cb1, and the convolution data Cc1, the convolution data Cd1, the convolution data Ce1, and the convolution data Cf1 can be obtained. As a result, for example, many image feature amounts can be extracted, so that the imaging device 10 can perform highly accurate image processing. Therefore, the additional functions of the imaging device 10 can be made high performance.

[0083] In the examples shown in Figs. 4A, 4B, 5A, 5B, and 6, one of the four cells 12 holds imaging data, and three of the cells 12 hold weighting data. In other words, of the cells 12 constituting the cell array 11, 1 / 4 of the cells 12 hold imaging data, and 3 / 4 of the cells 12 hold weighting data. Here, if the ratio of the cells 12 that hold imaging data is increased, the resolution of the image represented by the imaging data can be increased. On the other hand, if the ratio of the cells 12 that hold weighting data is increased, image processing can be performed with higher accuracy, and the additional functions of the imaging device 10 can be made high performance.

[0084] The logic circuit 51 may have a function of performing an operation other than the product-sum operation. For example, the logic circuit 51 may have a function of performing pooling. When the logic circuit 51 has a function of performing pooling, the amount of data output from the imaging device 10 can be reduced.

[0085] As described above, when the imaging device 10 is driven in the second mode, the arithmetic circuit 17 having the logic circuit 51 performs the arithmetic operation. Therefore, the arithmetic operations shown in Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, and Fig. 6 are performed when the imaging device 10 is driven in the second mode. Note that when the imaging device 10 is driven in the first mode, imaging data x can be held in all the cells 12.

[0086] <One example of a method for driving an imaging device_1> An example of a driving method of the imaging device 10 will be described below. Specifically, an example of a driving method of the cell 12[i,j] (i is an integer of 1 to m-1, and j is an integer of 1 to n-1), the cell 12[i,j+1], the cell 12[i+1,j], the cell 12[i+1,j+1], the transistor 27[j], the transistor 27[j+1], the transistor 52[h,k] (h is an integer of 1 to p-1, and k is an integer of 1 to q-1), the transistor 52[h,k+1], the transistor 52[h+1,k], and the transistor 52[h+1,k+1] will be described. FIG. 7 is a circuit diagram showing components of the imaging device 10 that will be used to explain an example of a driving method. As shown in FIG. 7, the wiring 47 is supplied with a potential VSS as a low potential. Also, the wiring 41 and the wiring 46 are supplied with a high potential.

[0087] In the following, all the transistors related to the description of the driving method are n-channel transistors, but the following description of the driving method can be referred to even if some or all of the transistors are p-channel transistors by appropriately changing the magnitude relationship of the potentials, etc. Also, as shown in Figure 7, the driving method will be described assuming that cell 12 has the configuration shown in Figure 2A, but the following description can be referred to even if cell 12 has the configuration shown in Figure 2B by appropriately changing the magnitude relationship of the potentials, etc.

[0088] 8 is a timing chart showing an example of a method for driving the imaging device 10 when the imaging device 10 is driven in the first mode. As described above, in the first mode, calculations using weight data are not performed.

[0089] In the timing chart shown in Fig. 8, high potential is indicated by "H" and low potential is indicated by "L." Also, the timing chart shown in Fig. 8 does not take into account delays within the circuit. The above is the same for other timing charts.

[0090] In a period T01, a high potential is supplied to the wiring 32[i,j], the wiring 32[i+1,j], the wiring 32[i,j+1], the wiring 32[i+1,j+1], the wiring 33[i,j], the wiring 33[i+1,j], the wiring 33[i,j+1], the wiring 33[i+1,j+1], and the wiring 36. As a result, the transistor 22[i,j], the transistor 22[i,j+1], the transistor 22[i+1,j], the transistor 22[i+1,j+1], the transistor 23[i,j], the transistor 23[i,j+1], the transistor 23[i+1,j], the transistor 23[i+1,j+1], the transistor 26[i,j], the transistor 26[i,j+1], the transistor 26[i+1,j], and the transistor 26[i+1,j+1] are turned on. In addition, a low potential is supplied to the wiring 35[i], the wiring 35[i+1], the wiring 43[j], the wiring 43[j+1], the wiring 53[h], and the wiring 53[h+1]. As a result, the transistors 25[i,j], 25[i,j+1], 25[i+1,j], 25[i+1,j+1], 52[h,k], 52[h,k+1], 52[h+1,k], and 52[h+1,k+1] are turned off. In addition, a bias potential Vb is supplied to the wiring 37. Here, the bias potential refers to a potential that, when supplied to the gate of a transistor, drives the transistor as a current source. For example, when supplied to the gate of a transistor, it refers to a potential that drives the transistor in a saturation region.

[0091] In the period T01, the potentials of the nodes FD[i,j], FD[i,j+1], FD[i+1,j], and FD[i+1,j+1] are set to low potentials, which are the potentials of the wiring 43[j] and wiring 43[j+1]. As a result, the potentials of the nodes FD[i,j], FD[i,j+1], FD[i+1,j], and FD[i+1,j+1] are reset. Thus, the period T01 is a period in which a reset operation is performed. In the period T01, the data generation circuit 14 generates reset data, and the reset data is supplied to the cell 12 via the wiring 43.

[0092] In the period T02, the potentials of the wiring 32[i,j], the wiring 32[i+1,j], the wiring 32[i,j+1], and the wiring 32[i+1,j+1] are set to low potential, and then the potentials of the wiring 33[i,j], the wiring 33[i+1,j], the wiring 33[i,j+1], and the wiring 33[i+1,j+1] are set to low potential. As a result, the transistors 22[i,j], the transistors 22[i,j+1], the transistors 22[i+1,j], and the transistors 22[i+1,j+1] are turned off, and then the transistors 23[i,j], the transistors 23[i,j+1], the transistors 23[i+1,j], and the transistors 23[i+1,j+1] are turned off. This completes the reset operation.

[0093] In the period T03, the potentials of the wiring 32[i,j], the wiring 32[i+1,j], the wiring 32[i,j+1], and the wiring 32[i+1,j+1] are set to high potential. As a result, the transistors 22[i,j], the transistors 22[i,j+1], the transistors 22[i+1,j], and the transistors 22[i+1,j+1] are turned on, and the potentials of the nodes FD[i,j], the nodes FD[i,j+1], the nodes FD[i+1,j], and the nodes FD[i+1,j+1] rise in response to the illuminance of the light irradiated to the photoelectric conversion element 21[i,j], the photoelectric conversion element 21[i,j+1], the photoelectric conversion element 21[i+1,j], and the photoelectric conversion element 21[i+1,j+1], respectively. Therefore, the period T03 is a period in which an exposure operation is performed.

[0094] In period T04, the potentials of the wiring 32[i,j], the wiring 32[i+1,j], the wiring 32[i,j+1], and the wiring 32[i+1,j+1] are set to low. As a result, the transistors 22[i,j], 22[i,j+1], 22[i+1,j], and 22[i+1,j+1] are turned off, and the exposure operation is completed. As a result, the cells 12[i,j], 12[i,j+1], 12[i+1,j], and 12[i+1,j+1] can acquire imaging data.

[0095] In the period T05, the potential of the wiring 35[i] is set to a high potential to turn on the transistors 25[i,j] and 25[i,j+1], and then the potential of the wiring 35[i] is set to a low potential to turn off the transistors 25[i,j] and 25[i,j+1]. By turning on the transistor 25[i,j], the imaging data acquired by the cell 12[i,j] is output to the readout circuit 16 via the wiring 45[j], and the imaging data acquired by the cell 12[i,j] is read out. By turning on the transistor 25[i,j+1], the imaging data acquired by the cell 12[i,j+1] is output to the readout circuit 16 via the wiring 45[j+1], and the imaging data acquired by the cell 12[i,j+1] is read out.

[0096] Next, the potential of the wiring 35[i+1] is set to a high potential to turn on the transistors 25[i+1,j] and 25[i+1,j+1], and then the potential of the wiring 35[i+1] is set to a low potential to turn off the transistors 25[i+1,j] and 25[i+1,j+1]. By turning on the transistor 25[i+1,j], the imaging data acquired by the cell 12[i+1,j] is output to the readout circuit 16 via the wiring 45[j], and the imaging data acquired by the cell 12[i+1,j] is read out. In addition, by turning on the transistor 25[i+1,j+1], the imaging data acquired by the cell 12[i+1,j+1] is output to the readout circuit 16 via the wiring 45[j+1], and the imaging data acquired by the cell 12[i+1,j+1] is read out. From the above, the period T05 is a period in which the read operation is performed.

[0097] The above is an example of the method of driving the imaging device 10 in the first mode.

[0098] Next, an example of a driving method of the imaging device 10 in the second mode will be described. Specifically, as shown in Fig. 9, an example of a driving method of the imaging device 10 will be described in a case where the cell 12[i,j] acquires imaging data x, and weight data w1 is written to the cell 12[i,j+1], weight data w2 is written to the cell 12[i+1,j], and weight data w3 is written to the cell 12[i+1,j+1]. Fig. 10 is a timing chart showing an example of a driving method of the imaging device 10 when the imaging device 10 is driven in the second mode.

[0099] In the period T11, first, a high potential is supplied to the wiring 37. This causes the transistors 27[j] and 27[j+1] to be turned on. In addition, a low potential is supplied to the wirings 32[i,j], 32[i,j+1], 32[i+1,j], 32[i+1,j+1], 33[i,j], 33[i,j+1], 33[i+1,j], 33[i+1,j+1], 35[i], 35[i+1], 36, 53[h], and 53[h+1]. As a result, transistor 22[i,j], transistor 22[i,j+1], transistor 22[i+1,j], transistor 22[i+1,j+1], transistor 23[i,j], transistor 23[i,j+1], transistor 23[i+1,j], transistor 23[i+1,j+1], transistor 25[i,j], transistor 25[i,j+1], transistor 25[i+1,j], transistor 25[i+1,j+1], transistor 26[i,j], transistor 26[i,j+1], transistor 26[i+1,j], transistor 26[i+1,j+1], transistor 52[h,k], transistor 52[h,k+1], transistor 52[h+1,k], and transistor 52[h+1,k+1] are non-conductive.

[0100] Next, the data generation circuit 14 supplies the weight data w1 to the wiring 43[j+1]. In addition, the potential of the wiring 33[i,j+1] is set to high potential to make the transistor 23[i,j+1] conductive. As a result, the potential of the node FD[i,j+1] becomes a potential corresponding to the weight data w1, and the weight data w1 is written to the cell 12[i,j+1]. After that, the potential of the wiring 33[i,j+1] is set to low potential to make the transistor 23[i,j+1] non-conductive. As a result, the potential of the node FD[i,j+1] is held, and the weight data w1 is held in the cell 12[i,j+1].

[0101] Next, the data generation circuit 14 supplies the weight data w2 to the wiring 43[j] and the weight data w3 to the wiring 43[j+1]. In addition, the potentials of the wiring 33[i+1,j] and the wiring 33[i+1,j+1] are set to high potentials, and the transistors 23[i+1,j] and 23[i+1,j+1] are turned on. As a result, the potential of the node FD[i+1,j] becomes a potential corresponding to the weight data w2, and the weight data w2 is written to the cell 12[i+1,j]. In addition, the potential of the node FD[i+1,j+1] becomes a potential corresponding to the weight data w3, and the weight data w3 is written to the cell 12[i+1,j+1]. After that, the potentials of the wiring 33[i+1,j] and the wiring 33[i+1,j+1] are set to low potentials to make the transistors 23[i+1,j] and 23[i+1,j+1] non-conductive. As a result, the potentials of the nodes FD[i+1,j] and FD[i+1,j+1] are held, so that the weight data w2 is held in the cell 12[i+1,j] and the weight data w3 is held in the cell 12[i+1,j+1].

[0102] As described above, the period T11 is a period in which weight data is written to the cell 12. Note that in the period T11, a high potential can be simultaneously supplied to all the wirings 33 electrically connected to the cell 12 to which weight data is written, for example, among the wirings 33[i,1] to 33[i,n]. After that, a high potential can be simultaneously supplied to all the wirings 33 electrically connected to the cell 12 to which weight data is written, for example, among the wirings 33[i+1,1] to 33[i+1,n].

[0103] In the period T12, the potentials of the wiring 32[i,j] and the wiring 33[i,j] are set to high potential. As a result, the transistor 22[i,j] and the transistor 23[i,j] are turned on. In addition, the potential of the wiring 43[j] is set to low potential. As a result, the potential of the node FD[i,j] is set to low potential. As a result, the potential of the node FD[i,j] is reset. Therefore, the period T12 is a period during which the cell 12 that acquires imaging data performs a reset operation. In the period T12, the data generation circuit 14 generates reset data, and the reset data is supplied to the cell 12[i,j] through the wiring 43[j].

[0104] In the period T13, the potential of the wiring 32[i,j] is set to low, and then the potential of the wiring 33[i,j] is set to low. As a result, the transistor 22[i,j] is turned off, and then the transistor 23[i,j] is turned off. This completes the reset of the cell 12[i,j].

[0105] In the period T14, the potential of the wiring 32[i,j] is set to a high potential. This causes the transistor 22[i,j] to be turned on, and the potential of the node FD[i,j] rises in response to the illuminance of the light irradiated to the photoelectric conversion element 21[i,j]. Thus, the period T14 is a period during which an exposure operation is performed on the cell 12 from which imaging data is acquired.

[0106] In the period T15, the potential of the wiring 32[i,j] is set to low. This causes the transistor 22[i,j] to be turned off, and the exposure operation ends. As a result, the cell 12[i,j] can obtain image data.

[0107] In FIG. 10, the weight data is written to the cell 12[i,j+1], the cell 12[i+1,j], and the cell 12[i+1,j+1], and then the cell 12[i,j] acquires the imaging data, but this is not a limitation of one embodiment of the present invention. The weight data may be written after the imaging data is acquired. That is, the operation shown in the period T11 may be performed after the operations shown in the periods T12 to T15 are performed. For example, after the imaging data is written to each of the cell [i,j], the cell 12[i,j+1], the cell 12[i+1,j], and the cell 12[i+1,j+1], the weight data may be written so that the imaging data held in the cell 12[i,j+1], the cell 12[i+1,j], and the cell 12[i+1,j+1] are rewritten to the weight data.

[0108] In the period T16, the potential of the wiring 36 is set to a high potential, and the transistors 26[i,j], 26[i,j+1], 26[i+1,j], and 26[i+1,j+1] are turned on. As described above, a high potential is supplied to the wiring 46. Therefore, the wiring 44[i,j], the wiring 44[i,j+1], the wiring 44[i+1,j], and the wiring 44[i+1,j+1] are turned to a high potential. As a result, the wiring 44[i,j], the wiring 44[i,j+1], the wiring 44[i+1,j], and the wiring 44[i+1,j+1] are precharged. After the precharging is completed, the potential of the wiring 36 is set to low, so that the transistors 26[i,j], 26[i,j+1], 26[i+1,j], and 26[i+1,j+1] are turned off.

[0109] In the period T17, the wirings 35[i] and 35[i+1] are set to high potential, and the transistors 25[i,j], 25[i,j+1], 25[i+1,j], and 25[i+1,j+1] are turned on. Note that in the period T17, a high potential can be supplied to the wirings 35[1] to 35[m] at the same time, for example.

[0110] Here, the potential of the node FD[i,j] in the period T17 is the potential VFD[i,j], the potential of the node FD[i,j+1] is the potential VFD[i,j+1], the potential of the node FD[i+1,j] is the potential VFD[i+1,j], and the potential of the node FD[i+1,j+1] is the potential VFD[i+1,j+1]. The threshold voltage of the transistor 24[i,j] is the potential Vth[i,j], the threshold voltage of the transistor 24[i,j+1] is the potential Vth[i,j+1], the threshold voltage of the transistor 24[i+1,j] is the potential Vth[i+1,j], and the threshold voltage of the transistor 24[i+1,j] is the potential Vth[i+1,j], and the threshold voltage of the transistor 24[i+1,j+1] is the potential Vth[i+1,j+1]. Furthermore, as described above, the potential of the wiring 47 is the potential VSS. Furthermore, potential VFD[i,j] is greater than potential "Vth[i,j]+VSS", potential VFD[i,j+1] is less than potential "Vth[i,j+1]+VSS", potential VFD[i+1,j] is less than potential "Vth[i+1,j]+VSS", and potential VFD[i+1,j+1] is greater than potential "Vth[i+1,j+1]+VSS".

[0111] Fig. 11 is a circuit diagram for explaining the operation of the imaging device 10 during the period T17. In Fig. 11, transistors that are not conductive are marked with an x. Current is also indicated by arrows.

[0112] 11, in a period T17, the transistors 25[i,j], 25[i,j+1], 25[i+1,j], 25[i+1,j+1], 27[j], and 27[j+1] are in a conductive state, while the transistors 26[i,j], 26[i,j+1], 26[i+1,j], and 26[i+1,j+1] are in a non-conductive state.

[0113] In the period T16, the wiring 44[i,j], the wiring 44[i,j+1], the wiring 44[i+1,j], and the wiring 44[i+1,j+1] are precharged to a high potential. As described above, a low potential is supplied to the wiring 47. As a result, the wiring 44 is electrically connected to the drain of the transistor 24, and the wiring 45 is electrically connected to the source of the transistor 24 through the transistor 25.

[0114] As described above, in the period T17, the transistor 25 and the transistor 27 are in a conductive state. Therefore, the source potential of the transistor 24 is the potential VSS. Therefore, if the gate potential of the transistor 24 is equal to or higher than the sum of the threshold voltage of the transistor 24 and the potential VSS, the transistor 24 is in a conductive state. On the other hand, if the gate potential of the transistor 24 is lower than the sum of the threshold voltage of the transistor 24 and the potential VSS, the transistor 24 is in a non-conductive state. As described above, the potential VFD[i,j] which is the gate potential of the transistor 24[i,j] is higher than the sum of the threshold voltage Vth[i,j] and the potential VSS. Also, the potential VFD[i+1,j+1] which is the gate potential of the transistor 24[i+1,j+1] is higher than the sum of the threshold voltage Vth[i+1,j+1] and the potential VSS. As a result, the transistors 24[i,j] and 24[i+1,j+1] are turned on. This causes the wiring 44[i,j] and the wiring 47 to be turned on, and the potential of the wiring 44[i,j] becomes low. Also, the wiring 44[i+1,j+1] and the wiring 47 are turned on, and the potential of the wiring 44[i+1,j+1] becomes low.

[0115] On the other hand, the potential VFD[i,j+1] which is the gate potential of the transistor 24[i,j+1] is lower than the sum of the threshold voltage Vth[i,j+1] and the potential VSS. Also, the potential VFD[i+1,j] which is the gate potential of the transistor 24[i+1,j] is lower than the sum of the threshold voltage Vth[i+1,j] and the potential VSS. As a result, the transistor 24[i,j+1] and the transistor 24[i+1,j] are turned off. As a result, the potentials of the wiring 44[i,j+1] and the wiring 44[i+1,j] remain at the high potential which is the precharge potential.

[0116] As a result, in period T17, the imaging data and weighting data held in the cell 12 can be output as binary data from the wiring 44. As a result, the imaging data and weighting data held in the cell 12 are read out.

[0117] The imaging data and weighting data output by the cell 12 to the wiring 44 are supplied to the logic circuit 51. The logic circuit 51 performs an operation using the imaging data and weighting data. For example, a multiply-and-accumulate operation such as shown in Figures 4A, 4B, 5A, and 5B is performed. Note that since the imaging data and weighting data output by the cell 12 to the wiring 44 are binary data, they can be supplied to the logic circuit 51 without A / D conversion.

[0118] In the period T18, the potentials of the wirings 35[i] and 35[i+1] are set to low potential, and the transistors 25[i,j], 25[i,j+1], 25[i+1,j], and 25[i+1,j+1] are turned off. This ends the reading of the image data x, weight data w1, weight data w2, and weight data w3. Note that in the period T17, low potentials can be supplied to the wirings 35[1] to 35[m] at the same time, for example.

[0119] In the period T19, the potential of the wiring 53[h] is set to high potential to turn on the transistors 52[h,k] and 52[h,k+1], and then the potential of the wiring 53[h] is set to low potential to turn off the transistors 52[h,k] and 52[h,k+1]. After that, the potential of the wiring 53[h+1] is set to high potential to turn on the transistors 52[h+1,k] and 52[h+1,k+1], and then the potential of the wiring 53[h+1] is set to low potential to turn off the transistors 52[h+1,k] and 52[h+1,k+1]. In this manner, the calculation result by the logic circuit 51 can be read out. As described above, the read calculation result can be input to a neural network such as CNN to perform image processing.

[0120] The above is an example of the method of driving the imaging device 10 in the second mode.

[0121] <Image capture device configuration example 2> Fig. 12A is a circuit diagram showing a configuration example of cell 12, which is a modified example of the configuration shown in Fig. 2A. Cell 12 shown in Fig. 12A differs from cell 12 shown in Fig. 2A in that it does not have transistor 26 but has transistor 28. The following mainly describes the configuration that differs from cell 12 shown in Fig. 2A.

[0122] One of the source and the drain of the transistor 24 is electrically connected to one of the source and the drain of the transistor 25, one of the source and the drain of the transistor 28, and a wiring 44. The other of the source and the drain of the transistor 24 is electrically connected to a wiring 46. The other of the source and the drain of the transistor 25 is electrically connected to a wiring 45. The other of the source and the drain of the transistor 28 is electrically connected to a wiring 48. The gate of the transistor 28 is electrically connected to a wiring 38.

[0123] The wiring 48 functions as a power supply line. For example, a low potential can be supplied to the wiring 48.

[0124] Although details will be described later, a source follower circuit is configured by the transistor 24 and the transistor 28 by supplying a bias potential to the wiring 38. In this case, the input terminal of the source follower circuit is electrically connected to the node FD, and the output terminal is electrically connected to the wiring 44. Thus, the imaging data and weight data held in the cell 12 can be output to the wiring 44 as analog data.

[0125] The transistor 28 can be the same type of transistor as the transistors 22 to 25. For example, the transistor 28 can be an OS transistor or a Si transistor.

[0126] Fig. 12B is a circuit diagram showing a configuration example of cell 12, which is a modified example of the configuration shown in Fig. 12A. Cell 12 shown in Fig. 12B differs from cell 12 shown in Fig. 12A in that the cathode of photoelectric conversion element 21 is electrically connected to one of the source and drain of transistor 22, and the anode of photoelectric conversion element 21 is electrically connected to wiring 41.

[0127] Fig. 13 is a circuit diagram showing a configuration example of the arithmetic circuit 17 when the cell 12 has the configuration shown in Fig. 12A or 12B. The arithmetic circuit 17 shown in Fig. 13 differs from the arithmetic circuit 17 shown in Fig. 3 in that it has an A / D conversion circuit 54.

[0128] An input terminal of the A / D conversion circuit 54 is electrically connected to the wiring 44, and an output terminal of the A / D conversion circuit 54 is electrically connected to an input terminal of the logic circuit 51. Here, the number of input terminals of the A / D conversion circuit 54 and the number of output terminals of the A / D conversion circuit 54 can be the same as the number of input terminals of the logic circuit 51. For example, each of them can be m×n.

[0129] The A / D conversion circuit 54 has a function of converting analog data output from the cell 12 to the wiring 44 into digital data. As described above, when the imaging device 10 is driven in the second mode, the imaging data or weighting data held in the cell 12 is output to the wiring 44. Therefore, by providing the A / D conversion circuit 54 between the wiring 44 and the logic circuit 51, even when the cell 12 outputs the imaging data or weighting data as analog data from the wiring 44, the logic circuit 51 can perform calculations using the imaging data and the weighting data.

[0130] <An example of a driving method for an imaging device_2> In the following, an example of a driving method of the imaging device 10 in which the cell 12 has the configuration shown in FIG. 12A and the arithmetic circuit 17 has the configuration shown in FIG. 13 will be described with reference to FIG. 15 to FIG. 17. Specifically, an example of a driving method of the cell 12[i,j], cell 12[i,j+1], cell 12[i+1,j], cell 12[i+1,j+1], transistor 27[j], transistor 27[j+1], transistor 52[h,k], transistor 52[h,k+1], transistor 52[h+1,k], and transistor 52[h+1,k+1] in the configuration shown in FIG. 12A will be described. FIG. 14 is a circuit diagram showing components of the imaging device 10 that will explain an example of a driving method. As shown in FIG. 14, it is assumed that the potential VSS is supplied to the wiring 47 as a low potential. It is also assumed that the wiring 41 and the wiring 46 are supplied with a high potential. It is also assumed that the wiring 48 is supplied with a low potential.

[0131] In the following, all the transistors related to the description of the driving method are n-channel transistors, but the following description of the driving method can be referred to even if some or all of the transistors are p-channel transistors by appropriately changing the magnitude relationship of the potentials, etc. Also, as shown in Fig. 14, the driving method will be described assuming that the cell 12 has the configuration shown in Fig. 12A, but the following description can be referred to even if the cell 12 has the configuration shown in Fig. 12B by appropriately changing the magnitude relationship of the potentials, etc.

[0132] 15 is a timing chart showing an example of a method for driving the imaging device 10 when the imaging device 10 is driven in the first mode. As described above, in the first mode, calculations using weight data are not performed.

[0133] In the periods T21 to T25, a low potential is supplied to the wiring 38 to turn off the transistors 28[i,j], 28[i,j+1], 28[i+1,j], and 28[i+1,j+1]. Otherwise, the operation in the periods T21 to T25 can be similar to the operation in the periods T01 to T05 in the timing chart shown in Figure 8. Note that the bias potential supplied to the wiring 37 in the periods T21 to T25 is a bias potential Vb1.

[0134] Fig. 17A is a circuit diagram showing a configuration in which a transistor that can be made non-conductive during all of the periods T21 to T25 is omitted from the circuit diagram shown in Fig. 12A. Fig. 17A also shows the configuration of the cell 12, as well as the transistor 27 to whose gate a bias potential Vb1 is supplied during the periods T21 to T25. As described above, the transistor 28 is made non-conductive during the periods T21 to T25. Therefore, the transistor 28 is not shown in the circuit diagram shown in Fig. 17A.

[0135] Next, an example of a driving method of the imaging device 10 in the second mode will be described. Specifically, as shown in Fig. 9, an example of a driving method of the imaging device 10 will be described in a case where the cell 12[i,j] acquires imaging data x, and weight data w1 is written to the cell 12[i,j+1], weight data w2 is written to the cell 12[i+1,j], and weight data w3 is written to the cell 12[i+1,j+1]. Fig. 16 is a timing chart showing an example of a driving method of the imaging device 10 when the imaging device 10 is driven in the second mode.

[0136] The potentials of the wirings 32, 33, 35, 37, 43, 53, and the node FD in the periods T31 to T35 can be the same as the potentials of the wirings 32, 33, 35, 37, 43, 53, and the node FD in the periods T11 to T15 of the timing chart shown in Figure 10. The potentials of the wirings 32, 33, 35, 37, 43, 53, and the node FD in the period T36 can be the same as the potentials of the wirings 32, 33, 35, 37, 43, 53, and the node FD in the period T19 of the timing chart shown in Figure 10.

[0137] In the periods T31 to T36, a bias potential Vb2 is supplied to the wiring 38. Fig. 17B is a circuit diagram illustrating a configuration in which a transistor that can be turned off in all of the periods T31 to T36 is omitted from the circuit diagram illustrated in Fig. 12A. As illustrated in Fig. 16, the transistor 25 is turned off in the periods T31 to T36. Therefore, the transistor 25 is not illustrated in the circuit diagram illustrated in Fig. 17B.

[0138] As described above, in the period T31 to the period T36, the bias potential Vb2 is supplied to the gate of the transistor 28. In addition, a high potential is supplied to the wiring 46, and a low potential is supplied to the wiring 48. As described above, the transistor 24 and the transistor 28 form a source follower circuit 29. Here, the input terminal of the source follower circuit 29 is electrically connected to the node FD, and the output terminal of the source follower circuit 29 is electrically connected to the wiring 44. In the period T31 to the period T36, analog data of a potential corresponding to the potential of the node FD can be continuously output from the wiring 44. As a result, the imaging data x according to VFD[i,j], which is the potential of the node FD[i,j], can be output from the wiring 44[i,j+1]. In addition, the weight data w1 according to VFD[i,j+1], which is the potential of the node FD[i,j+1], can be output from the wiring 44[i,j+1]. Moreover, the wiring 44[i+1,j] can output weight data w2 according to VFD[i+1,j], which is the potential of the node FD[i+1,j]. Furthermore, the wiring 44[i+1,j+1] can output weight data w3 according to VFD[i+1,j+1], which is the potential of the node FD[i+1,j+1].

[0139] The above is one example of the method of driving the imaging device 10 in which the cells 12 have the configuration shown in FIG. 12A and the arithmetic circuit 17 has the configuration shown in FIG.

[0140] 12A or 12B, the imaging data and weighting data output from the cell 12 via the wiring 44 in the second mode can be analog data. The analog data output from the cell 12 via the wiring 44 is then converted to digital data by the A / D conversion circuit 54 and then supplied to the logic circuit 51. As described above, the imaging data and weighting data input to the logic circuit 51 can be multi-value digital data.

[0141] <Image capture device configuration example 3> 18A and 18B are perspective views showing a configuration example of the imaging device 10. In Fig. 18A, a configuration example having a laminated structure of a layer 561 and a layer 562 is shown.

[0142] The layer 561 has a photoelectric conversion element 21. The photoelectric conversion element 21 can be a stack of a layer 565a, a layer 565b, and a layer 565c, as shown in Fig. 18C.

[0143] The photoelectric conversion element 21 shown in FIG. 18C is a pn junction photodiode. + a layer 565b is an n-type semiconductor, and a layer 565c is an n-type semiconductor. + Alternatively, layer 565a may be an n-type semiconductor. + a layer 565b is a p-type semiconductor, and a layer 565c is a p-type semiconductor. + Alternatively, the layer 565b may be an i-type semiconductor, and the layer 565b may be a pin junction photodiode.

[0144] The pn junction photodiode or pin junction photodiode can be formed using single crystal silicon. The pin junction photodiode can also be formed using a thin film of amorphous silicon, microcrystalline silicon, polycrystalline silicon, or the like.

[0145] Furthermore, the photoelectric conversion element 21 included in the layer 561 may be a laminate of layers 566a, 566b, 566c, and 566d, as shown in Fig. 18D. The photoelectric conversion element 21 shown in Fig. 18D is an example of an avalanche photodiode, in which the layers 566a and 566d correspond to electrodes, and the layers 566b and 566c correspond to a photoelectric conversion unit.

[0146] Layer 566a is preferably a low resistance metal layer, such as aluminum, titanium, tungsten, tantalum, silver, or a laminate of these.

[0147] The layer 566d is preferably a conductive layer having a high light-transmitting property to visible light. For example, indium oxide, tin oxide, zinc oxide, indium-tin oxide, gallium-zinc oxide, indium-gallium-zinc oxide, graphene, or the like can be used. Note that the layer 566d may be omitted.

[0148] The layers 566b and 566c of the photoelectric conversion unit may be configured as a pn junction photodiode with a photoelectric conversion layer made of, for example, a selenium-based material. It is preferable that the layer 566b is made of a selenium-based material that is a p-type semiconductor, and the layer 566c is made of gallium oxide or the like that is an n-type semiconductor.

[0149] Photoelectric conversion elements using selenium-based materials have the characteristic of high external quantum efficiency for visible light. In such photoelectric conversion elements, avalanche multiplication can be used to increase the amplification of electrons relative to the amount of incident light. In addition, selenium-based materials have a high optical absorption coefficient, which offers the advantage of production in that the photoelectric conversion layer can be made in a thin film. Thin films of selenium-based materials can be formed using a vacuum deposition method, a sputtering method, or the like.

[0150] As the selenium-based material, crystalline selenium such as single crystal selenium and polycrystalline selenium, amorphous selenium, a compound of copper, indium, and selenium (CIS), or a compound of copper, indium, gallium, and selenium (CIGS) can be used.

[0151] The n-type semiconductor is preferably made of a material that has a wide band gap and is transparent to visible light. For example, zinc oxide, gallium oxide, indium oxide, tin oxide, or a mixture of these oxides can be used. These materials also function as a hole injection blocking layer, and can reduce dark current.

[0152] Furthermore, the photoelectric conversion element 21 included in the layer 561 may be a laminate of layers 567a, 567b, 567c, 567d, and 567e, as shown in Fig. 18E. The photoelectric conversion element 21 shown in Fig. 18E is an example of an organic photoconductive film, in which the layers 567a and 567e correspond to electrodes, and the layers 567b, 567c, and 567d correspond to photoelectric conversion units.

[0153] Either the layer 567b or the layer 567d of the photoelectric conversion portion can be a hole transport layer, and the other can be an electron transport layer. The layer 567c can be a photoelectric conversion layer.

[0154] For example, molybdenum oxide can be used as the hole transport layer, and for example, fullerenes such as C60 and C70, or derivatives thereof can be used as the electron transport layer.

[0155] As the photoelectric conversion layer, a mixed layer (bulk heterojunction structure) of an n-type organic semiconductor and a p-type organic semiconductor can be used.

[0156] 18A, for example, a silicon substrate can be used. The silicon substrate has Si transistors and the like. For example, the transistors of the cells 12 and the transistors of the arithmetic circuit 17 can be provided in the layer 562. In addition, for example, the transistors of the row driver circuit 13, the transistors of the data generation circuit 14, the transistors of the read circuit 16, and the transistor 27 can be provided in the layer 562.

[0157] Furthermore, the imaging device 10 may have a laminated structure of a layer 561, a layer 563, and a layer 562 as shown in FIG. 18B.

[0158] The layer 563 may include an OS transistor. In this case, the layer 562 may include a Si transistor. For example, the transistors included in the cell 12 and the transistor 27 may be provided in the layer 563, and the transistors included in the arithmetic circuit 17 may be provided in the layer 562. For example, the transistors included in the row driver circuit 13, the transistors included in the data generation circuit 14, and the transistors included in the read circuit 16 may be provided in the layer 562.

[0159] 18B, for example, the cell 12 provided in the layer 563 and the arithmetic circuit 17 provided in the layer 562 can be provided so as to have an overlapping area. This reduces the area occupied by the imaging device 10, and the imaging device 10 can be miniaturized. Note that in the configuration of FIG. 18B, the layer 562 may be used as a support substrate, and the cell 12 and other circuits may be provided in the layers 561 and 563.

[0160] As a semiconductor material used for an OS transistor, a metal oxide having an energy gap of 2 eV or more, preferably 2.5 eV or more, more preferably 3 eV or more can be used. A representative example is an oxide semiconductor containing indium, for example, CAAC-OS (C-Axis Aligned Crystalline Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor) described later can be used. CAAC-OS has stable atoms constituting the crystal, and is suitable for transistors that value reliability. In addition, CAC-OS has high mobility characteristics, and is suitable for transistors that operate at high speed.

[0161] OS transistors have a large energy gap in the semiconductor layer, and therefore exhibit extremely low off-current characteristics of a few yA / μm (current value per 1 μm of channel width). OS transistors also have characteristics different from Si transistors, such as the absence of impact ionization, avalanche breakdown, and short channel effects, and can form highly reliable circuits with high voltage resistance. OS transistors are also less susceptible to variations in electrical characteristics caused by non-uniformity in crystallinity, which is a problem with Si transistors.

[0162] The semiconductor layer of the OS transistor can be, for example, a film represented by an In-M-Zn-based oxide containing indium, zinc, and M (a metal such as aluminum, titanium, gallium, germanium, yttrium, zirconium, lanthanum, cerium, tin, neodymium, or hafnium).

[0163] When the oxide semiconductor constituting the semiconductor layer is an In-M-Zn oxide, the atomic ratio of the metal elements of the sputtering target used to form the In-M-Zn oxide film preferably satisfies In≧M and Zn≧M. As the atomic ratio of the metal elements of such a sputtering target, In:M:Zn=1:1:1, In:M:Zn=1:1:1.2, In:M:Zn=3:1:2, In:M:Zn=4:2:3, In:M:Zn=4:2:4.1, In:M:Zn=5:1:6, In:M:Zn=5:1:7, In:M:Zn=5:1:8, etc. are preferable. Note that the atomic ratio of the semiconductor layer to be formed includes a variation of ±40% of the atomic ratio of the metal elements contained in the above sputtering target.

[0164] The semiconductor layer is made of an oxide semiconductor with a low carrier density. For example, the semiconductor layer has a carrier density of 1×10 17 / cm 3 Less than or equal to 1×10 15 / cm 3 Less than 1×10, more preferably 13 / cm 3 Less than or equal to 1×10 11 / cm 3Less than 1×10, more preferably 10 / cm 3 Less than 1 x 10 -9 / cm 3 An oxide semiconductor having a carrier density of 1000 or more can be used. Such an oxide semiconductor is called a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor. The oxide semiconductor has a low density of defect states and is stable in characteristics.

[0165] Note that the composition is not limited to these, and an appropriate composition may be used depending on the required semiconductor characteristics and electrical characteristics (field-effect mobility, threshold voltage, etc.) of the transistor. In order to obtain the required semiconductor characteristics of the transistor, it is preferable to appropriately set the carrier density, impurity concentration, defect density, atomic ratio of metal element to oxygen, interatomic distance, density, or the like of the semiconductor layer.

[0166] When silicon or carbon, which is one of the group 14 elements, is contained in the oxide semiconductor constituting the semiconductor layer, oxygen vacancies increase and the semiconductor layer becomes n-type. For this reason, the concentration of silicon or carbon in the semiconductor layer (concentration obtained by secondary ion mass spectrometry) is set to 2×10 18 atoms / cm 3 Less than or equal to 2×10 17 atoms / cm 3 The following applies.

[0167] In addition, when an alkali metal or an alkaline earth metal is bonded to an oxide semiconductor, carriers may be generated, which may increase the off-state current of a transistor. For this reason, the concentration of an alkali metal or an alkaline earth metal in a semiconductor layer (concentration obtained by secondary ion mass spectrometry) is set to 1×10 18 atoms / cm 3 Less than or equal to 2×10 16 atoms / cm 3 To the following:

[0168] In addition, when nitrogen is contained in the oxide semiconductor constituting the semiconductor layer, electrons that act as carriers are generated, which increases the carrier density and makes the semiconductor layer more likely to be n-type. As a result, a transistor using an oxide semiconductor that contains nitrogen is likely to have normally-on characteristics. For this reason, the nitrogen concentration in the semiconductor layer (concentration obtained by secondary ion mass spectrometry) is 5×10 18 atoms / cm 3 It is preferable to do the following:

[0169] Furthermore, when hydrogen is contained in an oxide semiconductor constituting a semiconductor layer, it reacts with oxygen bonded to a metal atom to form water, which may form oxygen vacancies in the oxide semiconductor. When oxygen vacancies are present in a channel formation region in an oxide semiconductor, the transistor may have normally-on characteristics. Furthermore, defects in which hydrogen has entered the oxygen vacancies may function as donors and generate electrons that serve as carriers. In addition, some of the hydrogen may bond with oxygen that is bonded to a metal atom to generate electrons that serve as carriers. Therefore, a transistor using an oxide semiconductor that contains a large amount of hydrogen is likely to have normally-on characteristics.

[0170] A defect in which hydrogen has entered an oxygen vacancy can function as a donor for an oxide semiconductor. However, it is difficult to quantitatively evaluate the defect. Thus, an oxide semiconductor may be evaluated by its carrier concentration instead of its donor concentration. Thus, in this specification and the like, a carrier concentration assuming a state in which no electric field is applied may be used as a parameter of an oxide semiconductor instead of the donor concentration. In other words, the "carrier concentration" described in this specification and the like may be rephrased as the "donor concentration".

[0171] Therefore, it is preferable that hydrogen in the oxide semiconductor be reduced as much as possible. Specifically, the hydrogen concentration in the oxide semiconductor measured by secondary ion mass spectrometry (SIMS) is 1×10 20 atoms / cm 3 Less than 1 x 10 19atoms / cm 3 less than 5×10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 When an oxide semiconductor in which impurities such as hydrogen are sufficiently reduced is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0172] The semiconductor layer may have a non-single crystal structure. The non-single crystal structure includes, for example, a CAAC-OS having crystals oriented along the c-axis, a polycrystalline structure, a microcrystalline structure, or an amorphous structure. Among the non-single crystal structures, the amorphous structure has the highest density of defect states, and the CAAC-OS has the lowest density of defect states.

[0173] An oxide semiconductor film having an amorphous structure has, for example, a disordered atomic arrangement and does not include a crystalline component, or an oxide film having an amorphous structure has, for example, a completely amorphous structure and does not include a crystalline portion.

[0174] The semiconductor layer may be a mixed film having two or more of an amorphous structure region, a microcrystalline structure region, a polycrystalline structure region, a CAAC-OS region, and a single crystal structure region. The mixed film may have a single layer structure or a multilayer structure including two or more of the above-mentioned regions.

[0175] Fig. 19A is a diagram illustrating an example of a cross section of the imaging device 10 shown in Fig. 18A. The layer 561 has a pn junction type photodiode with a silicon photoelectric conversion layer as the photoelectric conversion element 21. The layer 562 has a Si transistor, and Fig. 19A illustrates the transistors 22 and 23 among the transistors included in the cell 12.

[0176] In the photoelectric conversion element 21, the layer 565a is p + layer 565b is an n-type region, layer 565c is an n-type region, +The layer 565b is provided with a region 536 for connecting a power supply line to the layer 565c. For example, the region 536 is a p + It can be a mold region.

[0177] Fig. 20A is a cross-sectional view of the portion indicated by the dashed dotted line A1-A2 in Fig. 19A, and shows a cross section in the channel width direction of transistor 22, etc. As shown in Fig. 20A, the Si transistor can be a fin type having a channel formation region in silicon substrate 540. Also, the Si transistor may not be a fin type, but may be a planar type as shown in Fig. 20B.

[0178] 20C, the transistor may have a silicon thin-film semiconductor layer 545. The semiconductor layer 545 may be, for example, single crystal silicon (SOI: Silicon on Insulator) formed on an insulating layer 546 on a silicon substrate 540.

[0179] FIG. 19A shows a configuration example in which electrical connection between elements of layer 561 and elements of layer 562 is achieved by a bonding technique.

[0180] The layer 561 is provided with an insulating layer 542, a conductive layer 533, and a conductive layer 534. The conductive layer 533 and the conductive layer 534 have regions buried in the insulating layer 542. The conductive layer 533 is electrically connected to a layer 565a. The conductive layer 534 is electrically connected to a region 536. Furthermore, the surfaces of the insulating layer 542, the conductive layer 533, and the conductive layer 534 are flattened so that they are all at the same height.

[0181] The layer 562 includes an insulating layer 541, a conductive layer 531, and a conductive layer 532. The conductive layer 531 and the conductive layer 532 have regions buried in the insulating layer 541. The conductive layer 531 is electrically connected to the source or drain of the transistor 22. The conductive layer 532 is electrically connected to a power supply line. The surfaces of the insulating layer 541, the conductive layer 531, and the conductive layer 532 are flattened to have the same height.

[0182] Here, the conductive layers 531 and 533 preferably contain the same metal element as a main component. The conductive layers 532 and 534 preferably contain the same metal element as a main component. The insulating layers 541 and 542 preferably contain the same component.

[0183] For example, Cu, Al, Sn, Zn, W, Ag, Pt, Au, or the like can be used for the conductive layers 531, 532, 533, and 534. It is preferable to use Cu, Al, W, or Au in view of ease of bonding. Furthermore, silicon oxide, silicon oxynitride, silicon nitride oxide, silicon nitride, titanium nitride, or the like can be used for the insulating layers 541 and 542.

[0184] That is, the same metal material as described above is preferably used for each of the combination of the conductive layer 531 and the conductive layer 533 and the combination of the conductive layer 532 and the conductive layer 534. The same insulating material as described above is preferably used for each of the insulating layer 541 and the insulating layer 542. With this structure, the layer 561 and the layer 562 can be bonded to each other at the boundary between them.

[0185] This bonding makes it possible to obtain electrical connection between the combination of conductive layer 531 and conductive layer 533 and the combination of conductive layer 532 and conductive layer 534. In addition, it is possible to obtain a connection between insulating layer 541 and insulating layer 542 that has sufficient mechanical strength.

[0186] To bond metal layers together, a surface activation bonding method can be used, in which oxide films and adsorbed layers of impurities on the surfaces are removed by sputtering or other methods, and cleaned and activated surfaces are brought into contact with each other to bond them. Alternatively, a diffusion bonding method can be used, in which surfaces are bonded together using a combination of temperature and pressure. Both methods involve bonding at the atomic level, resulting in excellent bonding not only electrically but also mechanically.

[0187] In addition, for bonding insulating layers, a hydrophilic bonding method can be used in which high flatness is achieved by polishing, etc., and then the surfaces that have been hydrophilically treated with oxygen plasma or the like are brought into contact with each other to form a temporary bond, and then the final bond is achieved by dehydrating them through heat treatment. Hydrophilic bonding also produces bonds at the atomic level, and therefore can provide mechanically excellent bonds.

[0188] When the layers 561 and 562 are bonded to each other, since an insulating layer and a metal layer are mixed on each bonding surface, the layers 561 and 562 may be bonded to each other by, for example, a combination of a surface activated bonding method and a hydrophilic bonding method.

[0189] For example, a method of cleaning the surface after polishing, subjecting the surface of the metal layer to an anti-oxidation treatment, and then subjecting it to a hydrophilic treatment and bonding can be used. The surface of the metal layer may be made of a resistant metal such as Au and then subjected to a hydrophilic treatment. Note that bonding methods other than the above-mentioned methods may also be used.

[0190] Fig. 19B is a cross-sectional view of a case where a pn junction photodiode having a photoelectric conversion layer made of a selenium-based material is used as photoelectric conversion element 21 shown in Fig. 18A. One electrode is layer 566a, photoelectric conversion layers are layers 566b and 566c, and the other electrode is layer 566d.

[0191] In this case, the layer 561 can be formed directly on the layer 562. The layer 566a is electrically connected to the source or drain of the transistor 22. The layer 566d is electrically connected to the power supply line via the conductive layer 537. Note that even when an organic photoconductive film is used for the photoelectric conversion element 21, the connection with the transistor is similar.

[0192] FIG. 21A is a diagram for explaining an example of a cross section of the imaging device 10 shown in FIG. 18B. The layer 561 has a pn junction photodiode with a silicon photoelectric conversion layer as the photoelectric conversion element 21. The layer 562 has a Si transistor, and in FIG. 21A, the transistor 52 and the transistor 61 among the transistors included in the arithmetic circuit 17 are illustrated as examples. Here, the transistor 61 can be the transistor included in the logic circuit 51. The layer 563 has an OS transistor, and the transistors 22 and 23 included in the cell 12 are illustrated as examples. The layer 561 and the layer 563 show a configuration example in which electrical connection is obtained by bonding them together.

[0193] A detailed configuration example of an OS transistor is shown in Fig. 22A. The OS transistor shown in Fig. 22A has a self-aligned structure in which an insulating layer is provided over a stack of an oxide semiconductor layer and a conductive layer, and a source electrode 705 and a drain electrode 706 can be formed by providing a groove that reaches the semiconductor layer.

[0194] The OS transistor can have a channel formation region, a source region 703, and a drain region 704 formed in the oxide semiconductor layer, as well as a gate electrode 701 and a gate insulating film 702. At least the gate insulating film 702 and the gate electrode 701 are provided in the trench. An oxide semiconductor layer 707 may be further provided in the trench.

[0195] As shown in FIG. 22B, the OS transistor may have a self-aligned structure in which a source region and a drain region are formed in a semiconductor layer using a gate electrode 701 as a mask.

[0196] Alternatively, as shown in FIG. 22C, it may be a non-self-aligned top-gate transistor having a region where the source electrode 705 or the drain electrode 706 overlaps with the gate electrode 701.

[0197] The transistor 22 and the transistor 23 have a back gate 535. FIG. 22D is a cross-sectional view of the portion indicated by the dashed line B1-B2 in FIG. 22A, and shows a cross section in the channel width direction of the transistor 22 and the like. The back gate 535 may be electrically connected to the front gate of the transistor provided opposite to it, as shown in FIG. 22D. Note that FIG. 22D shows the transistor of FIG. 22A as an example, but the same applies to transistors of other structures. Also, a fixed potential different from that of the front gate may be supplied to the back gate 535. Note that the transistor 22 and the transistor 23 may have a structure without the back gate 535.

[0198] An insulating layer 543 having a function of preventing diffusion of hydrogen is provided between a region where an OS transistor is formed and a region where a Si transistor is formed. Hydrogen in the insulating layer provided near the channel formation regions of the transistor 52 and the transistor 61 terminates dangling bonds of silicon. Meanwhile, hydrogen in the insulating layer provided near the channel formation regions of the transistor 22 and the transistor 23 is one of factors that generate carriers in the oxide semiconductor layer.

[0199] The insulating layer 543 confines hydrogen in one layer, which can improve the reliability of the transistor 52 and the transistor 61. In addition, the insulating layer 543 suppresses diffusion of hydrogen from one layer to the other layer, which can improve the reliability of the transistor 22 and the transistor 23.

[0200] The insulating layer 543 can be made of, for example, aluminum oxide, aluminum oxynitride, gallium oxide, gallium oxynitride, yttrium oxide, yttrium oxynitride, hafnium oxide, hafnium oxynitride, yttria-stabilized zirconia (YSZ), or the like.

[0201] 21B is a cross-sectional view of the imaging device 10 when a pn junction type photodiode with a selenium-based material as a photoelectric conversion layer is used for the photoelectric conversion element 21. A layer 561 on which the photoelectric conversion element 21 is provided can be formed directly on the layer 563. The above description can be referred to for details of the layers 561, 562, and 563. Note that the connection with the transistor is similar when an organic photoconductive film is used for the photoelectric conversion element 21.

[0202] 23A is a perspective view showing a configuration example of a colored layer (color filter) etc. of the imaging device 10. An insulating layer 580 is formed on a layer 561 on which the photoelectric conversion element 21 is formed. The insulating layer 580 may be a silicon oxide film or the like having high translucency to visible light. A silicon nitride film may be laminated as a passivation film. A dielectric film such as hafnium oxide may be laminated as an anti-reflection film.

[0203] A light-shielding layer 581 may be formed on the insulating layer 580. The light-shielding layer 581 has a function of preventing color mixing of light passing through the colored layer above. The light-shielding layer 581 may be a metal layer such as aluminum or tungsten. In addition, the metal layer may be laminated with a dielectric film that functions as an anti-reflection film.

[0204] An insulating layer 582 can be provided as a planarizing film on the insulating layer 580 and the light-shielding layer 581. In addition, a colored layer 583 (colored layers 583a, 583b, and 583c) is formed. For example, a color image can be obtained by assigning colors such as R (red), G (green), B (blue), Y (yellow), C (cyan), and M (magenta) to the colored layers 583a, 583b, and 583c.

[0205] Over the colored layer 583, an insulating layer 586 having a light-transmitting property to visible light and the like can be provided.

[0206] 23B, an optical conversion layer 585 may be used instead of the colored layer 583. With such a configuration, an imaging device capable of obtaining images in various wavelength regions can be obtained.

[0207] For example, if a filter that blocks light with wavelengths equal to or shorter than visible light is used in the optical conversion layer 585, it can be used as an infrared imaging device. Also, if a filter that blocks light with wavelengths equal to or shorter than near-infrared light is used in the optical conversion layer 585, it can be used as a far-infrared imaging device. Also, if a filter that blocks light with wavelengths equal to or longer than visible light is used in the optical conversion layer 585, it can be used as an ultraviolet imaging device.

[0208] Furthermore, if a scintillator is used for the optical conversion layer 585, the imaging device 10 can be an imaging device for obtaining an image that visualizes the intensity of radiation used in an X-ray imaging device or the like. When radiation such as X-rays that has passed through a subject is incident on the scintillator, it is converted into light (fluorescence) such as visible light or ultraviolet light by the photoluminescence phenomenon. Then, imaging data is obtained by detecting the light with the photoelectric conversion element 21. Also, an imaging device having such a configuration may be used for a radiation detector or the like.

[0209] The scintillator includes a substance that absorbs the energy of radiation such as X-rays or gamma rays and emits visible or ultraviolet light when irradiated with the radiation. For example, Gd2O2S:Tb, Gd2O2S:Pr, Gd2O2S:Eu, BaFCl:Eu, NaI, CsI, CaF2, BaF2, CeF3, LiF, LiI, ZnO, or the like dispersed in a resin or ceramics can be used as the substance.

[0210] In addition, in the photoelectric conversion element 21 using a selenium-based material, radiation such as X-rays can be directly converted into an electric charge, so that a scintillator may not be required.

[0211] 23C, a microlens array 584 may be provided on the insulating layer 586 so as to have an area overlapping with the colored layer 583. Light passing through each lens of the microlens array 584 passes through the colored layer 583 directly below and is irradiated onto the photoelectric conversion element 21. The microlens array 584 may be provided so as to have an area overlapping with the optical conversion layer 585 shown in FIG. 23B.

[0212] <Image capture device configuration example_4> 24A is a diagram illustrating an example of the imaging device 10, and illustrates a configuration example in which a layer 564 is provided in the imaging device 10 illustrated in FIG. 19A. The layer 564 is provided over the layer 561. The layer 564 includes an insulating layer 580, a light-shielding layer 581, an insulating layer 582, an insulating layer 586, and a colored layer 587.

[0213] An insulating layer 580 is formed on the layer 561, and a light-shielding layer 581 and an insulating layer 582 are formed on the insulating layer 580. An insulating layer 586 is formed on the insulating layer 582, and a colored layer 587 is formed on the insulating layer 586.

[0214] The colored layer 587 can also function as a microlens. Therefore, there is no need to form a microlens separately in addition to the colored layer 587, and the imaging device 10 can be manufactured by a simple method. In addition, when light is irradiated onto the interface between materials having different refractive indices, a part of the irradiated light is reflected. For example, when light is irradiated onto the interface between a microlens and a layer such as an insulating layer provided so as to be in contact with the bottom of the microlens, a part of the light is reflected. Therefore, by not forming a microlens separately in addition to the colored layer, it is possible to suppress attenuation of the light irradiated onto the imaging device 10 before it is received by the photoelectric conversion element 21. This makes it possible to increase the light detection sensitivity of the imaging device 10.

[0215] Fig. 24B, Fig. 25A, and Fig. 25B are diagrams for explaining an example of the imaging device 10. Fig. 24B is a configuration example in which a layer 564 is provided in the imaging device 10 shown in Fig. 19B, Fig. 25A is a configuration example in which a layer 564 is provided in the imaging device 10 shown in Fig. 21A, and Fig. 25B is a configuration example in which a layer 564 is provided in the imaging device 10 shown in Fig. 21B. The configuration of the layer 564 included in the imaging device 10 shown in Fig. 24B, Fig. 25A, and Fig. 25B can be the same as the configuration of the layer 564 included in the imaging device 10 shown in Fig. 24A.

[0216] Fig. 26A is a diagram for explaining an example of the imaging device 10, which is a modified example of the imaging device 10 shown in Fig. 24A. The imaging device 10 shown in Fig. 26A differs from the imaging device 10 shown in Fig. 24A in the configuration of the layer 564. The layer 564 provided in the imaging device 10 shown in Fig. 26A has an insulating layer 580, a light-shielding layer 581, a colored layer 587, and an insulating layer 588.

[0217] An insulating layer 580 is formed on the layer 561, and a light-shielding layer 581 and a colored layer 587 are formed on the insulating layer 580. As described above, the colored layer 587 can also function as a microlens. An insulating layer 588 is formed on the colored layer 587. The insulating layer 588 can be a planarizing film. The insulating layer 588 is, for example, a film that is transparent to visible light.

[0218] Figures 26B, 27A, and 27B are diagrams illustrating an example of the imaging device 10, which are modifications of the imaging device 10 shown in Figures 24B, 25A, and 25B, respectively. The imaging device 10 shown in Figures 26B, 27A, and 27B has a layer 564 having the same configuration as the layer 564 shown in Figure 26A.

[0219] FIG. 28A is a perspective view showing a configuration example of the layer 564 shown in FIG. 24A, FIG. 24B, FIG. 25A, and FIG. 25B. FIG. 28B is a perspective view showing a configuration example of the layer 564 shown in FIG. 26A, FIG. 26B, FIG. 27A, and FIG. 27B. As shown in FIG. 28A and FIG. 28B, a colored layer 587 (a colored layer 587a, a colored layer 587b, and a colored layer 587c) is formed. For example, a color image can be obtained by assigning colors such as R (red), G (green), B (blue), Y (yellow), C (cyan), and M (magenta) to the colored layer 587a, the colored layer 587b, and the colored layer 587c.

[0220] This embodiment mode can be combined with other embodiment modes as appropriate.

[0221] (Embodiment 2) In this embodiment, a metal oxide (hereinafter also referred to as an oxide semiconductor) which can be used for the OS transistor described in the above embodiment will be described.

[0222] <Classification of crystal structures> First, classification of crystal structures in oxide semiconductors will be described with reference to Fig. 29A. Fig. 29A is a diagram for explaining classification of crystal structures of oxide semiconductors, typically IGZO (metal oxide containing In, Ga, and Zn).

[0223] As shown in FIG. 29A, oxide semiconductors are broadly classified into "Amorphous", "Crystalline", and "Crystal". "Amorphous" includes completely amorphous. "Crystalline" includes CAAC, nc (nanocrystalline), and CAC. "Crystalline" excludes single crystal, poly crystal, and completely amorphous. "Crystalline" includes single crystal and poly crystal.

[0224] The structure in the bold frame shown in Fig. 29A is an intermediate state between "Amorphous" and "Crystal" and belongs to a new boundary region (New crystalline phase). In other words, this structure is completely different from the energetically unstable "Amorphous" and "Crystal".

[0225] The crystal structure of the film or substrate can be evaluated using an X-ray diffraction (XRD) spectrum. FIG. 29B shows an XRD spectrum obtained by GIXD (Grazing-Incidence XRD) measurement of the CAAC-IGZO film classified as "Crystalline". The GIXD method is also called the thin film method or the Seemann-Bohlin method. Hereinafter, the XRD spectrum obtained by the GIXD measurement shown in FIG. 29B will be simply referred to as the XRD spectrum. The composition of the CAAC-IGZO film shown in FIG. 29B is in the vicinity of In:Ga:Zn=4:2:3 [atomic ratio]. The thickness of the CAAC-IGZO film shown in FIG. 29B is 500 nm.

[0226] As shown in Figure 29B, a clear peak indicating crystallinity is detected in the XRD spectrum of the CAAC-IGZO film. Specifically, a peak indicating c-axis orientation is detected near 2θ=31° in the XRD spectrum of the CAAC-IGZO film. Note that, as shown in Figure 29B, the peak near 2θ=31° is asymmetric with respect to the angle at which the peak intensity is detected.

[0227] The crystal structure of the film or substrate can be evaluated by a diffraction pattern (also called a nanobeam electron diffraction pattern) observed by nanobeam electron diffraction (NBED). The diffraction pattern of the CAAC-IGZO film is shown in FIG. 29C. FIG. 29C is a diffraction pattern observed by NBED, which causes an electron beam to be incident parallel to the substrate. The composition of the CAAC-IGZO film shown in FIG. 29C is approximately In:Ga:Zn=4:2:3 [atomic ratio]. In the nanobeam electron diffraction method, electron diffraction is performed with a probe diameter of 1 nm.

[0228] As shown in FIG. 29C, multiple spots indicating c-axis orientation are observed in the diffraction pattern of the CAAC-IGZO film.

[0229] <<Structure of oxide semiconductor>> In addition, when focusing on the crystal structure, oxide semiconductors may be classified differently from that shown in FIG. 29A. For example, oxide semiconductors are divided into single-crystal oxide semiconductors and other non-single-crystal oxide semiconductors. Examples of non-single-crystal oxide semiconductors include the above-mentioned CAAC-OS and nc-OS. In addition, non-single-crystal oxide semiconductors include polycrystalline oxide semiconductors, amorphous-like oxide semiconductors (a-like OS), amorphous oxide semiconductors, and the like.

[0230] Here, the above-mentioned CAAC-OS, nc-OS, and a-like OS will be described in detail.

[0231] [CAAC-OS] CAAC-OS is an oxide semiconductor having a plurality of crystalline regions, each of which has a c-axis aligned in a specific direction. The specific direction is the thickness direction of the CAAC-OS film, the normal direction of the surface on which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film. The crystalline region is a region having periodic atomic arrangement. If the atomic arrangement is considered as a lattice arrangement, the crystalline region is also a region with a uniform lattice arrangement. CAAC-OS has a region in which a plurality of crystalline regions are connected in the ab-plane direction, and the region may have distortion. The distortion refers to a portion in which the direction of the lattice arrangement changes between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement in the region in which the plurality of crystalline regions are connected. In other words, CAAC-OS is an oxide semiconductor having a c-axis aligned and no clear orientation in the ab-plane direction.

[0232] Each of the multiple crystalline regions is composed of one or more minute crystals (crystals with a maximum diameter of less than 10 nm). When a crystalline region is composed of one minute crystal, the maximum diameter of the crystalline region is less than 10 nm. When a crystalline region is composed of many minute crystals, the size of the crystalline region may be about several tens of nm.

[0233] In addition, in an In-M-Zn oxide (wherein element M is one or more elements selected from aluminum, gallium, yttrium, tin, titanium, etc.), the CAAC-OS tends to have a layered crystal structure (also referred to as a layered structure) in which a layer containing indium (In) and oxygen (hereinafter, In layer) and a layer containing element M, zinc (Zn), and oxygen (hereinafter, (M, Zn) layer) are stacked. Note that indium and element M are mutually substituted. Thus, the (M, Zn) layer may contain indium. Also, the In layer may contain element M. Note that the In layer may contain Zn. The layered structure is observed as a lattice image in a high-resolution TEM image, for example.

[0234] When the CAAC-OS film is subjected to structural analysis using, for example, an XRD device, a peak indicating c-axis orientation is detected at or near 2θ=31° in out-of-plane XRD measurement using θ / 2θ scan. Note that the position of the peak indicating c-axis orientation (2θ value) may vary depending on the type and composition of the metal elements constituting the CAAC-OS.

[0235] For example, a plurality of bright points (spots) are observed in the electron diffraction pattern of the CAAC-OS film, and the two spots are observed at positions symmetrical to each other with respect to the spot of the incident electron beam that has passed through the sample (also called the direct spot).

[0236] When the crystal region is observed from the specific direction, the lattice arrangement in the crystal region is based on a hexagonal lattice, but the unit cell is not necessarily a regular hexagon and may be a non-regular hexagon. The above distortion may have a lattice arrangement such as a pentagon or heptagon. In addition, no clear grain boundary can be confirmed in the CAAC-OS even in the vicinity of the distortion. That is, it can be seen that the formation of grain boundaries is suppressed by the distortion of the lattice arrangement. This is thought to be because the CAAC-OS can tolerate distortion due to the fact that the arrangement of oxygen atoms in the ab-plane direction is not dense and the bond distance between atoms changes due to the substitution of metal atoms.

[0237] A crystal structure in which clear grain boundaries are observed is called a polycrystal. The grain boundaries are likely to become recombination centers and capture carriers, causing a decrease in the on-current of a transistor and a decrease in field effect mobility. Therefore, CAAC-OS in which clear grain boundaries are not observed is one of the crystalline oxides having a crystal structure suitable for a semiconductor layer of a transistor. In order to form a CAAC-OS, a structure containing Zn is preferable. For example, In-Zn oxide and In-Ga-Zn oxide are suitable because they can suppress the occurrence of grain boundaries more than In oxide.

[0238] The CAAC-OS is an oxide semiconductor with high crystallinity and no clear crystal grain boundaries. Therefore, it can be said that the CAAC-OS is less susceptible to a decrease in electron mobility due to crystal grain boundaries. In addition, since the crystallinity of an oxide semiconductor can be decreased by the inclusion of impurities or the generation of defects, the CAAC-OS can be said to be an oxide semiconductor with few impurities and defects (such as oxygen vacancies). Therefore, the physical properties of an oxide semiconductor having the CAAC-OS are stable. Therefore, an oxide semiconductor having the CAAC-OS is resistant to heat and has high reliability. In addition, the CAAC-OS is stable against high temperatures (so-called thermal budget) in the manufacturing process. Therefore, the use of the CAAC-OS in an OS transistor can increase the degree of freedom in the manufacturing process.

[0239] [nc-OS] The nc-OS has periodic atomic arrangement in a minute region (for example, a region of 1 nm to 10 nm, particularly a region of 1 nm to 3 nm). In other words, the nc-OS has minute crystals. Note that the size of the minute crystals is, for example, 1 nm to 10 nm, particularly 1 nm to 3 nm, and therefore the minute crystals are also called nanocrystals. In addition, the nc-OS does not show regularity in the crystal orientation between different nanocrystals. Therefore, no orientation is seen in the entire film. Therefore, depending on the analysis method, the nc-OS may be indistinguishable from an a-like OS or an amorphous oxide semiconductor. For example, when a structure analysis is performed on an nc-OS film using an XRD device, no peak indicating crystallinity is detected in out-of-plane XRD measurement using θ / 2θ scan. In addition, when an nc-OS film is subjected to electron diffraction (also called selected area electron diffraction) using an electron beam with a probe diameter larger than that of nanocrystals (for example, 50 nm or more), a diffraction pattern like a halo pattern is observed. On the other hand, when electron diffraction (also called nanobeam electron diffraction) is performed on an nc-OS film using an electron beam with a probe diameter (e.g., 1 nm to 30 nm) that is close to the size of a nanocrystal or smaller than the nanocrystal, an electron diffraction pattern in which multiple spots are observed within a ring-shaped region centered on the direct spot may be obtained.

[0240] [a-like OS] The a-like OS is an oxide semiconductor having a structure between the nc-OS and an amorphous oxide semiconductor. The a-like OS has a void or low-density region. That is, the a-like OS has lower crystallinity than the nc-OS and CAAC-OS. Moreover, the a-like OS has a higher hydrogen concentration in the film than the nc-OS and CAAC-OS.

[0241] <<Oxide semiconductor structure>> Next, the above-mentioned CAC-OS will be described in detail, with reference to its material composition.

[0242] [CAC-OS] CAC-OS is, for example, a material configuration in which elements constituting a metal oxide are unevenly distributed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof. In the following, a state in which one or more metal elements are unevenly distributed in a metal oxide and the regions having the metal elements are mixed in a size range of 0.5 nm to 10 nm, preferably 1 nm to 3 nm, or in the vicinity thereof, is also referred to as a mosaic or patch state.

[0243] Furthermore, CAC-OS is a composite metal oxide in which the material is separated into a first region and a second region, forming a mosaic structure, and the first region is distributed throughout the film (hereinafter, also referred to as a cloud structure). In other words, CAC-OS is a composite metal oxide in which the first region and the second region are mixed together.

[0244] Here, the atomic ratios of In, Ga, and Zn to the metal elements constituting the CAC-OS in the In-Ga-Zn oxide are represented as [In], [Ga], and [Zn], respectively. For example, in the CAC-OS in the In-Ga-Zn oxide, the first region is a region where [In] is larger than [In] in the composition of the CAC-OS film. Also, the second region is a region where [Ga] is larger than [Ga] in the composition of the CAC-OS film. Alternatively, for example, the first region is a region where [In] is larger than [In] in the second region and [Ga] is smaller than [Ga] in the second region. Also, the second region is a region where [Ga] is larger than [Ga] in the first region and [In] is smaller than [In] in the first region.

[0245] Specifically, the first region is a region mainly composed of indium oxide, indium zinc oxide, etc., and the second region is a region mainly composed of gallium oxide, gallium zinc oxide, etc. In other words, the first region can be rephrased as a region mainly composed of In, and the second region can be rephrased as a region mainly composed of Ga.

[0246] In addition, there are cases where a clear boundary between the first region and the second region cannot be observed.

[0247] For example, in the case of a CAC-OS of an In-Ga-Zn oxide, EDX mapping obtained using EDX (Energy Dispersive X-ray spectroscopy) has confirmed that the CAC-OS has a structure in which a region mainly composed of In (first region) and a region mainly composed of Ga (second region) are unevenly distributed and mixed.

[0248] When CAC-OS is used in a transistor, the conductivity due to the first region and the insulating property due to the second region act in a complementary manner, giving the CAC-OS a switching function (On / Off function). In other words, CAC-OS has a conductive function in part of the material and an insulating function in other parts of the material, and the material as a whole functions as a semiconductor. By separating the conductive function from the insulating function, it is possible to maximize both functions. Therefore, by using CAC-OS in a transistor, it is possible to achieve a high on-current (I on ), high field effect mobility (μ), and good switching behavior can be achieved.

[0249] Oxide semiconductors have a variety of structures and each structure has different characteristics. The oxide semiconductor of one embodiment of the present invention may include two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, or a CAAC-OS.

[0250] <Transistor Having Oxide Semiconductor> Next, the case where the oxide semiconductor is used for a transistor will be described.

[0251] By using the oxide semiconductor for a transistor, a transistor with high field-effect mobility and high reliability can be realized.

[0252] For the transistor, an oxide semiconductor having a low carrier concentration is preferably used. For example, the carrier concentration of the oxide semiconductor is 1×10 17 cm -3 Less than or equal to 1×10 15 cm -3 Less than 1×10, more preferably 13 cm -3 Less than or equal to 1×10 11 cm -3 Less than 1×10, more preferably 10 cm -3 Less than 1 x 10 -9 cm-3 The above is the case. Note that in order to reduce the carrier concentration of an oxide semiconductor film, the impurity concentration in the oxide semiconductor film may be reduced to reduce the density of defect states. In this specification and the like, an oxide semiconductor having a low impurity concentration and a low density of defect states is referred to as a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor. Note that an oxide semiconductor having a low carrier concentration may be referred to as a high-purity intrinsic or substantially high-purity intrinsic oxide semiconductor.

[0253] Furthermore, a highly purified intrinsic or substantially highly purified intrinsic oxide semiconductor film has a low density of defect states, and therefore the density of trap states might also be low.

[0254] In addition, charges trapped in the trap states of an oxide semiconductor take a long time to disappear and may behave as if they are fixed charges. Therefore, a transistor in which a channel formation region is formed in an oxide semiconductor with a high density of trap states may have unstable electrical characteristics.

[0255] Therefore, in order to stabilize the electrical characteristics of a transistor, it is effective to reduce the impurity concentration in the oxide semiconductor. In order to reduce the impurity concentration in the oxide semiconductor, it is preferable to also reduce the impurity concentration in a nearby film. Examples of impurities include hydrogen, nitrogen, alkali metals, alkaline earth metals, iron, nickel, silicon, and the like.

[0256] <Impurities> Here, the influence of each impurity in an oxide semiconductor will be described.

[0257] When an oxide semiconductor contains silicon or carbon, which is one of the group 14 elements, defect levels are formed in the oxide semiconductor. For this reason, the concentration of silicon or carbon in the oxide semiconductor and the concentration of silicon or carbon near the interface with the oxide semiconductor (concentration obtained by secondary ion mass spectrometry (SIMS)) are set to 2×10 18 atoms / cm 3 Less than or equal to 2×1017 atoms / cm 3 The following applies.

[0258] In addition, when an oxide semiconductor contains an alkali metal or an alkaline earth metal, defect states may be formed and carriers may be generated. Therefore, a transistor using an oxide semiconductor containing an alkali metal or an alkaline earth metal is likely to have normally-on characteristics. For this reason, when the concentration of an alkali metal or an alkaline earth metal in an oxide semiconductor obtained by SIMS is 1×10 18 atoms / cm 3 Less than or equal to 2×10 16 atoms / cm 3 To the following:

[0259] Furthermore, when nitrogen is contained in an oxide semiconductor, electrons serving as carriers are generated, the carrier concentration increases, and the semiconductor is likely to become n-type. As a result, a transistor using an oxide semiconductor containing nitrogen as a semiconductor is likely to have normally-on characteristics. Alternatively, when nitrogen is contained in an oxide semiconductor, trap states may be formed. As a result, the electrical characteristics of the transistor may become unstable. For this reason, the nitrogen concentration in an oxide semiconductor obtained by SIMS is set to 5×10 19 atoms / cm 3 Less than 5 x 10 18 atoms / cm 3 Less than or equal to 1×10 18 atoms / cm 3 Less than 5×10, more preferably 17 atoms / cm 3 To the following:

[0260] Furthermore, hydrogen contained in an oxide semiconductor reacts with oxygen bonded to a metal atom to form water, which may form an oxygen vacancy. When hydrogen enters the oxygen vacancy, electrons serving as carriers may be generated. In addition, some of the hydrogen may bond with oxygen bonded to a metal atom to generate electrons serving as carriers. Therefore, a transistor using an oxide semiconductor containing hydrogen is likely to have normally-on characteristics. For this reason, it is preferable to reduce hydrogen in the oxide semiconductor as much as possible. Specifically, when the hydrogen concentration in an oxide semiconductor measured by SIMS is 1×10 20 atoms / cm 3 Less than 1 x 10 19 atoms / cm 3 less than 5×10 18 atoms / cm 3 less than 1×10 18 atoms / cm 3 Make it less than.

[0261] When an oxide semiconductor in which impurities are sufficiently reduced is used for a channel formation region of a transistor, stable electrical characteristics can be obtained.

[0262] This embodiment mode can be appropriately combined with the descriptions of other embodiment modes.

[0263] (Embodiment 3) In this embodiment, an example of a package containing an image sensor chip and a camera module will be described. The image sensor chip can have the same configuration as the imaging device described above.

[0264] Fig. 30A1 is a perspective view of the upper surface of a package containing an image sensor chip. The package includes a package substrate 410 for fixing an image sensor chip 450, a cover glass 420, and an adhesive 430 for bonding the two together. The image sensor chip 450 is shown in Fig. 30A3, which will be described later.

[0265] 30A2 is an external perspective view of the bottom surface of the package. On the bottom surface of the package, a BGA (Ball grid array) is provided with solder balls as bumps 440. Note that the package is not limited to a BGA, and may also have an LGA (Land grid array) or a PGA (Pin Grid Array), etc.

[0266] 30A3 is a perspective view of the package with a portion of the cover glass 420 and the adhesive 430 omitted. Electrode pads 460 are formed on the package substrate 410, and the electrode pads 460 and the bumps 440 are electrically connected via through holes. The electrode pads 460 are electrically connected to the image sensor chip 450 by wires 470.

[0267] 30B1 is a perspective view of the appearance of the upper surface side of a camera module in which an image sensor chip is housed in a lens-integrated package. The camera module has a package substrate 411 for fixing an image sensor chip 451, a lens cover 421, a lens 435, and the like. In addition, an IC chip 490 having functions such as a driving circuit and a signal conversion circuit of an imaging device is also provided between the package substrate 411 and the image sensor chip 451, and has a configuration as a SiP (System in package). The image sensor chip 451 and the IC chip 490 are shown in FIG. 30B3, which will be described later.

[0268] 30B2 is a perspective view of the exterior of the bottom surface of the camera module. The bottom surface and side surfaces of the package substrate 411 are provided with lands 441 for mounting, forming a QFN (Quad flat no-lead package) configuration. Note that this configuration is merely an example, and a QFP (Quad flat package) or the above-mentioned BGA may also be provided.

[0269] 30B3 is a perspective view of the module in which lens cover 421 and a part of lens 435 are omitted. Land 441 is electrically connected to electrode pad 461, and electrode pad 461 is electrically connected to image sensor chip 451 or IC chip 490 by wire 471.

[0270] By housing the image sensor chip in a package of the above-mentioned type, mounting on a printed circuit board or the like becomes easy, and the image sensor chip can be incorporated into various semiconductor devices and electronic devices.

[0271] This embodiment mode can be combined with other embodiment modes as appropriate.

[0272] (Embodiment 4) In this embodiment, an example of an electronic device in which the imaging device of one embodiment of the present invention can be used will be described.

[0273] Examples of electronic devices in which the imaging device of one embodiment of the present invention can be used include display devices, personal computers, image storage devices or image playback devices equipped with a recording medium, mobile phones, game machines including portable types, portable data terminals, electronic book terminals, cameras such as video cameras and digital still cameras, goggle-type displays (head-mounted displays), navigation systems, audio playback devices (car audio, digital audio players, etc.), copiers, facsimiles, printers, printer-combined machines, automated teller machines (ATMs), vending machines, etc. Specific examples of these electronic devices are shown in FIGS.

[0274] 31A shows an example of a mobile phone 910, which includes a housing 911, a display unit 912, operation buttons 913, an external connection port 914, a speaker 915, a socket 916, a camera 917, an earphone socket 918, and the like. The mobile phone 910 can be provided with a touch sensor on the display unit 912. Any operation such as making a call or inputting characters can be performed by touching the display unit 912 with a finger or a stylus. In addition, various removable storage devices such as a memory card such as an SD card, a USB memory, and an SSD (solid state drive) can be inserted into the socket 916.

[0275] The imaging device of one embodiment of the present invention can be applied to the mobile phone 910. For example, the imaging device of one embodiment of the present invention can be applied to an element for acquiring imaging data by the mobile phone 910, such as the camera 917. The imaging device of one embodiment of the present invention can perform part of the calculation by a neural network. Thus, the mobile phone 910 can be equipped with an additional function such as an image recognition function. Furthermore, the power consumption of the mobile phone 910 can be reduced compared to the case where all the calculation by the neural network is performed by software.

[0276] 31B shows an example of a portable data terminal 920, which includes a housing 921, a display unit 922, a speaker 923, and a camera 924. Information can be input and output using a touch panel function of the display unit 922. Characters and the like can be recognized from an image acquired by the camera 924, and the characters can be output as voice by the speaker 923.

[0277] The imaging device of one embodiment of the present invention can be applied to the portable data terminal 920. For example, the imaging device of one embodiment of the present invention can be applied to an element for acquiring imaging data by the portable data terminal 920, such as the camera 924. The imaging device of one embodiment of the present invention can perform part of the calculation by a neural network. Thus, the portable data terminal 920 can be equipped with an additional function such as an image recognition function. Furthermore, the power consumption of the portable data terminal 920 can be reduced compared to the case where all the calculation by the neural network is performed by software.

[0278] 31C shows an example of a surveillance camera 960, which has a mounting fixture 961, a housing 962, a lens 963, and the like. The surveillance camera 960 can be attached to a wall, a ceiling, or the like using the mounting fixture 961. Note that the term "surveillance camera" is a common name and does not limit the use. For example, a device having a function as a surveillance camera is also called a camera or a video camera.

[0279] The imaging device of one embodiment of the present invention can be applied to the surveillance camera 960. For example, the imaging device of one embodiment of the present invention can be applied to an element for acquiring imaging data by the surveillance camera 960. The imaging device of one embodiment of the present invention can perform part of the calculation by a neural network. Thus, the surveillance camera 960 can be equipped with an additional function such as an image recognition function. Furthermore, the power consumption of the surveillance camera 960 can be reduced compared to the case where all the calculation by the neural network is performed by software.

[0280] 31D shows an example of a video camera 940, which has a first housing 941, a second housing 942, a display unit 943, operation keys 944, a lens 945, a connection unit 946, a speaker 947, a microphone 948, etc. The operation keys 944 and the lens 945 can be provided in the first housing 941, and the display unit 943 can be provided in the second housing 942.

[0281] The imaging device of one embodiment of the present invention can be applied to the video camera 940. For example, the imaging device of one embodiment of the present invention can be applied to an element for acquiring imaging data by the video camera 940. The imaging device of one embodiment of the present invention can perform part of the calculation by a neural network. Thus, the video camera 940 can be equipped with an additional function such as an image recognition function. Furthermore, the power consumption of the video camera 940 can be reduced compared to the case where all the calculation by the neural network is performed by software.

[0282] FIG. 31E illustrates an example of a digital camera 950, which includes a housing 951, a shutter button 952, a light-emitting unit 953, a lens 954, and the like. The imaging device of one embodiment of the present invention can be applied to the digital camera 950. For example, the imaging device of one embodiment of the present invention can be applied to an element for acquiring imaging data by the digital camera 950. The imaging device of one embodiment of the present invention can perform part of the calculation by a neural network. Therefore, the digital camera 950 can be equipped with an additional function such as an image recognition function. In addition, the power consumption of the digital camera 950 can be reduced compared to the case where all the calculations by the neural network are performed by software.

[0283] 31F shows an example of a wristwatch-type information terminal 930, which includes a housing / wristband 931, a display unit 932, operation buttons 933, an external connection port 934, a camera 935, and the like. The display unit 932 is provided with a touch panel for operating the information terminal 930. The housing / wristband 931 and the display unit 932 are flexible and have excellent wearability on the body.

[0284] The semiconductor device of one embodiment of the present invention can be applied to the information terminal 930. For example, the imaging device of one embodiment of the present invention can be applied to an element for acquiring imaging data by the information terminal 930, such as the camera 935. The imaging device of one embodiment of the present invention can perform part of the calculation by a neural network. Thus, the information terminal 930 can be equipped with an additional function such as an image recognition function. Furthermore, the power consumption of the information terminal 930 can be reduced as compared to the case where all the calculations by the neural network are performed by software.

[0285] Fig. 32A shows an external view of an automobile as an example of a moving body. Fig. 32B shows a simplified diagram of data exchange within the automobile. The automobile 890 has a plurality of cameras 891 and the like. The automobile 890 also includes various sensors (not shown) such as an infrared radar, a millimeter wave radar, and a laser radar.

[0286] The imaging device of one embodiment of the present invention can be applied to the camera 891. The imaging device of one embodiment of the present invention can perform part of the calculations by a neural network. Therefore, the camera 891 can be equipped with an additional function such as an image recognition function. Furthermore, the power consumption of the automobile 890 can be reduced compared to the case where all the calculations by the neural network are performed by software.

[0287] In an automobile 890, an integrated circuit 893 can be used for a camera 891 or the like. In the automobile 890, a plurality of images obtained by a camera 891 in a plurality of imaging directions 892 are processed by the integrated circuit 893, and the plurality of images are analyzed collectively by a host controller 895 or the like via a bus 894 or the like. This enables the automobile 890 to determine the surrounding traffic conditions, such as the presence or absence of guardrails or pedestrians, and perform automatic driving. It can also be used in a system that performs road guidance, hazard prediction, and the like.

[0288] In the integrated circuit 893, the obtained image data can be subjected to arithmetic processing such as a neural network, thereby enabling processes such as increasing the image resolution, reducing image noise, facial recognition (for crime prevention purposes, etc.), object recognition (for autonomous driving purposes, etc.), image compression, image correction (wide dynamic range), image restoration for lensless image sensors, positioning, character recognition, and reducing reflected glare.

[0289] In the above, an automobile is described as an example of a moving body, but the automobile may be any of an automobile having an internal combustion engine, an electric automobile, a hydrogen automobile, and the like. In addition, the moving body is not limited to an automobile. For example, the moving body may be a train, a monorail, a ship, an aircraft (helicopter, unmanned aerial vehicle (drone), airplane, rocket), and the like. A computer according to one embodiment of the present invention may be applied to these moving bodies to provide a system using artificial intelligence.

[0290] This embodiment mode can be combined with other embodiment modes as appropriate. [Explanation of symbols]

[0291] 10: imaging device, 11: cell array, 12: cell, 13: row driver circuit, 14: data generation circuit, 16: circuit, 17: arithmetic circuit, 21: photoelectric conversion element, 22: transistor, 23: transistor, 24: transistor, 25: transistor, 26: transistor, 27: transistor, 28: transistor, 29: source follower circuit, 32: wiring, 33: wiring, 35: wiring, 36: wiring, 37: wiring, 38: wiring, 41: wiring, 43: wiring, 44: wiring, 45: wiring, 46: wiring, 47: wiring, 48: wiring, 51: logic circuit, 52: transistor, 53: wiring, 54: A / D conversion circuit, 61: transistor, 410: package substrate, 411: package substrate, 420: cover glass, 421: lens cover, 430: adhesive, 435: lens, 440: bump, 441: land, 450: image sensor chip, 451: image sensor chip, 460: electrode pad, 461: electrode pad, 470: wire, 471: wire, 490: IC chip, 531: conductive layer, 532: conductive layer, 533: conductive layer, 534: conductive layer, 535: back gate, 536: region, 537: conductive layer, 540: silicon substrate , 541: insulating layer, 542: insulating layer, 543: insulating layer, 545: semiconductor layer, 546: insulating layer, 561: layer, 562: layer, 563: layer, 564: layer, 565a: layer, 565b: layer, 565c: layer, 566a: layer, 566b: layer, 566c: layer, 566d: layer, 567a: layer, 567b: layer, 567c: layer, 567d: layer, 567e: layer, 580: insulating layer, 581: light-shielding layer, 582: insulating layer, 583: colored layer, 583a: colored layer, 583b: colored layer, 583c: colored layer, 584: microlens array, 585: optical conversion layer, 586: insulating layer, 587: colored layer , 587a: colored layer, 587b: colored layer, 587c: colored layer, 588: insulating layer, 701: gate electrode, 702: gate insulating film, 703: source region, 704: drain region, 705: source electrode, 706: drain electrode, 707: oxide semiconductor layer, 890: automobile, 891: camera, 892: imaging direction, 893: integrated circuit, 894: bus, 895: host controller, 910: mobile phone, 911: housing, 912: display unit, 913: operation button, 914: external connection port, 915: speaker, 916: socket, 917: camera, 918: earphone socket,920: portable data terminal, 921: housing, 922: display unit, 923: speaker, 924: camera, 930: information terminal, 931: housing / wristband, 932: display unit, 933: operation button, 934: external connection port, 935: camera, 940: video camera, 941: housing, 942: housing, 943: display unit, 944: operation key, 945: lens, 946: connection unit, 947: speaker, 948: microphone, 950: digital camera, 951: housing, 952: shutter button, 953: light emitting unit, 954: lens, 960: surveillance camera, 961: mounting fixture, 962: housing, 963: lens,

Claims

[Claim 1] A cell array in which a plurality of cells are arranged in a matrix, and a logic circuit, The cell has a photoelectric conversion element, The cell has a function of acquiring imaging data using the photoelectric conversion element, The cell has a function of holding weight data, The logic circuit has a function of performing a calculation using the imaging data acquired by the cell and the weighting data held in a cell different from the cell that acquired the imaging data.

Images