Stacked imaging device and method for manufacturing the same

Abstract

To provide a stacked image sensor which includes a photoelectric conversion element good in utilization efficiency of incident light and capable of obtaining good wavelength characteristics according to a material and which also satisfies demands for multiple pixelation and a larger area.SOLUTION: A stacked image sensor includes a plurality of planar image sensor units 10 stacked in a direction orthogonal to a light incident direction, each image sensor unit including: a thin film substrate 21; an organic photoelectric conversion element 22 including a pixel electrode 23, an organic film 24 and a counter electrode 25 which are stacked in the direction orthogonal to a light incident direction in an area on the light incident side on the thin film substrate 21 so as to form the light-receiving part where light from the side of the thin film substrate 21 enters; and a readout circuit 26, on the thin film substrate 21, for reading out signals from the organic photoelectric conversion element 22, the readout circuit being formed in an area where the organic photoelectric conversion element 22 is not formed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a stacked image sensor and a method for manufacturing the same. More specifically, the present invention relates to a stacked image sensor and a method for manufacturing the same, in which a plurality of image sensor units each having a photoelectric conversion element formed on a substrate are stacked and provided, and a pixel configuration is adopted in which a pixel electrode of the photoelectric conversion element is connected to a readout circuit on the substrate and operated.

Background Art

[0002] With the progress of CMOS image sensor technology, the high definition and miniaturization of pixels of image sensors have been advanced, and small and high-performance cameras suitable for high-quality video shooting have been put into practical use. On the other hand, as the number of pixels of the image sensor is further increased, the selection time of one pixel becomes short and sufficient readout becomes difficult, resulting in deterioration of image quality. As a device configuration capable of improving such problems of the image sensor, an image sensor has been proposed in which a photodiode, a readout circuit, etc. are formed on a silicon substrate, and a plurality of them are stacked and irradiated with light from the side (see Patent Documents 1 to 3 below).

[0003] Since these devices can form a light receiving portion and a readout circuit in the substrate plane, in addition to digital driving, one-line driving, one-pixel driving, etc. are also possible, and it is possible to significantly improve the increase in processing time associated with matrix driving as in the conventional CMOS image sensor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The devices described in Patent Documents 1 to 3 assume semiconductors such as Si and GaAs, and since they have wavelength dependence in the depth direction, when light is incident on the side surface of the stack of photoelectric conversion elements, only a part of the incident light amount in the depth direction may be used as the detected value. As a result, there is a problem that the utilization efficiency of the incident light is poor and it is difficult to obtain good wavelength characteristics according to the material. In recent years, such devices are strongly required to satisfy the requirements of multi-pixelization and large-areaization in particular.

[0006] That is, the present invention has been made to solve such problems, and includes a photoelectric conversion element having good utilization efficiency of incident light and capable of obtaining good wavelength characteristics according to the material, and also satisfies the requirements for multi-pixelization and large-areaization. An object of the present invention is to provide a stacked image sensor and a method for manufacturing the same.

Means for Solving the Problems

[0007] In order to achieve the above object, the stacked image sensor and the method for manufacturing the same according to the present invention are configured as follows. That is, the stacked image sensor according to the present invention is a substrate, an organic photoelectric conversion element formed by laminating a pixel electrode, an organic film, and a counter electrode in a direction orthogonal to the direction in which light is incident in a region on the incident side of the light on the substrate so as to form a light receiving portion for receiving light from the side of the substrate, a reading circuit formed in a predetermined region on the substrate and electrically connected to the pixel electrode for reading a signal from the organic photoelectric conversion element, and a flat plate-shaped image sensor unit including being , the a flat-plate imaging element unit having a predetermined length, which is formed by combining imaging element members having different lengths of light-receiving surfaces, with respect to the direction in which light is incident and the direction in which the imaging element units are stacked, respectively in the orthogonal direction a flat-plate imaging element unit having a predetermined length, which is formed by combining imaging element members having different lengths of light-receiving surfaces, with respect to the direction in which light is incident and the direction in which the imaging element units are stacked, respectively are stacked in a plurality, which is characterized by

[0008] The flat pixel element units can be formed by stacking the pixel element units for R, G, and B in this order for color image capturing. Also, it is preferable that an adhesive layer is provided between the stacked flat pixel element units.

[0009] Also, the substrate is preferably made of a plastic material. 。

[0010] Furthermore, a method for manufacturing a stacked pixel device according to the present invention includes: a first step of forming a light receiving portion that receives light incident from the side of the substrate in a region on the incident side of the light on the substrate by stacking a pixel electrode, an organic film, and a counter electrode that constitute an organic photoelectric conversion element in a direction orthogonal to the direction in which the light is incident; a second step of forming a readout circuit for reading out a signal from the organic photoelectric conversion element, which is electrically connected to the pixel electrode, in a predetermined region on the substrate; a third step of stacking a plurality of the pixel device units created by performing the first step and the second step in the orthogonal direction; the direction in which light is incident and performing the steps. It is characterized by the above. In a method of manufacturing a stacked imaging element the third step includes a step of stacking the flat-plate imaging element units having a predetermined length, which are formed by combining imaging element members having different lengths of light-receiving surfaces, in a direction orthogonal to the direction in which light is incident and the direction in which the imaging element units are stacked, respectively

Effect of the Invention

[0011] In the stacked pixel device and its manufacturing method according to the present invention, an organic photoelectric conversion element, which is a light receiving portion that receives light incident from the side of the substrate, is formed by stacking a pixel electrode, an organic film, and a counter electrode in a direction orthogonal to the direction in which the light is incident in a region on the incident side of the light on the substrate. As a result, the pixel electrode can have a large length in the depth direction with respect to the light receiving surface, and as the photoelectric conversion film, an organic film that does not have wavelength dependence in the depth direction is used instead of a semiconductor such as Si or GaAs that has wavelength dependence in the depth direction. Therefore, incident light can be absorbed without waste, and good wavelength characteristics according to the material can be obtained. In addition, in the stacked image sensor and the method for manufacturing the same according to the present invention, since a flat-plate image sensor unit is used, it is possible to easily meet the requirements for multi-pixelization and large-areaization.

Brief Description of the Drawings

[0012]

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Embodiments for Carrying Out the Invention

[0013] Hereinafter, a stacked image sensor and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings. (Configuration of Stacked Image Sensor) FIG. 1(a) shows a schematic view of an image sensor unit which is a basic unit of the stacked image sensor according to the present embodiment. On one side (light incident side) of a single thin film substrate 21, an organic photoelectric conversion element 22 composed of a pixel electrode 23, an organic film 24, and a counter electrode 25 is formed, and a readout circuit 26 is formed in a region of the thin film substrate 21 following the formation region of the organic photoelectric conversion element 22. Further, an input / output electrode 27 is formed on the other side (opposite side to the light incident side) of the thin film substrate 21.

[0014] Note that the pixel electrode 23, the readout circuit 26, and the input / output electrode 27 of the organic optoelectronic conversion element 22 are electrically connected in this order, and an external voltage is applied between the pixel electrode 23 and the counter electrode 25 of the organic optoelectronic conversion element 22 through the input / output electrode 27 and the readout circuit 26. On the other hand, the detection signal (imaging signal) of the organic optoelectronic conversion element 22 read by the readout circuit 26 is output to the outside from the input / output electrode 27.

[0015] As described above, the pixel electrode 23 is formed along an edge portion on one side of the thin film substrate 21, and is arranged in a region where it is easy to receive light incident from the side on this one side. Note that one imaging element unit 10 as the basic unit may be formed on one thin film substrate 21, or a plurality (three in the example of FIG. 1(b); basically, corresponding to the number of pixels arranged in the depth direction of FIG. 1(b)) may be formed as shown in FIG. 1(b).

[0016] FIG. 1(b) shows a stacked imaging element 10A formed by stacking a plurality of imaging element units 10 as the basic unit. The light receiving surface 31 of this stacked imaging element 10A is a surface on which the state in which the organic optoelectronic conversion elements 22 of the imaging element unit 10 in the stacked imaging element 10A are stacked appears, and is formed so that this light receiving surface 31 becomes a flat surface.

[0017] Hereinafter, the details of the stacked imaging element 10A according to this embodiment will be further described. As described above, the stacked imaging element 10A is a side illumination type in which incident light is irradiated on the light receiving surface 31 provided on the side surface. Note that the counter electrode 25 can also be formed as a common electrode for all the organic optoelectronic conversion elements 22 on the same plane.

[0018] Since it is a side illumination type stacked imaging element 10A, the pixel electrode 23 and the counter electrode 25 do not necessarily have to be transparent. By making these electrodes 23 and 25 opaque, color mixing between adjacent imaging element units 10 can be prevented, and color mixing between pixels can be significantly reduced. Therefore, these electrodes are preferably made opaque rather than transparent. Therefore, various electrode materials can be applied, and the degree of freedom in selecting a material with less damage to the organic film can be increased.

[0019] As the material of the organic photoelectric conversion film, a material having sensitivity to a predetermined wavelength can be applied for each thin film substrate 21, and the thin film substrates 21 using different materials can be laminated so as to be adjacent to each other. For example, a color image pickup device can be formed by setting the pixel units 10 to be laminated as pixel units 10 corresponding to R, G, B (or R, G, B, G, etc. in order).

[0020] In addition, when the organic film 24 can be formed by the coating method, different color image pickup materials for each are applied to different regions of the same pixel unit 10 (coating process such as RGB imaging materials, etc.), and different color images (different color images of RGB) can be obtained for each line of the same pixel unit 10. Moreover, a color image can be obtained by combining a color filter with the organic photoelectric conversion element 22 having sensitivity over the entire visible region. In this case, the color separation of the color filter can be performed for each line or for each pixel.

[0021] The readout circuit 26 is a circuit necessary for reading out a signal from the organic photoelectric conversion element 22, and can adopt each circuit technology used in a conventional CMOS image sensor, such as a driving TFT, a selection TFT, a reset TFT, a load capacitor, etc. used in a conventional CMOS pixel circuit, an amplification circuit, various arithmetic circuits, and a circuit for noise reduction. In addition, the signal readout circuit 26 can be configured by combining oxide semiconductor TFTs. As a method for reading out a signal from the organic photoelectric conversion element 22, a method for reading out corresponding to various digital drives may be used, or a normal method of amplifying and reading out for each pixel may be applied.

[0022] In addition, in this stacked pixel device 10A, since a readout circuit and an arithmetic circuit are incorporated for each pixel, the readout method can be freely set for each pixel unit 10, such as line sensor readout, single-pixel readout, and multi-pixel readout.

[0023] As the thin film substrate 21, a thin plastic substrate or a substrate formed by depositing an insulating film on a thin metal such as aluminum foil can be used. The thickness of the thin film substrate 21 can be freely selected according to the material, and can be freely selected within a range of about several 100 nm to several 100 μm, for example, according to the simplicity of the manufacturing process during lamination, the light utilization efficiency, and further according to the use of the device.

[0024] When applying a resin material capable of coating and film formation to the thin film substrate 21, for example, it is possible to control the thickness to less than 1 μm by applying it extremely thinly and curing it, but it is also possible to form a film with a thickness of 100 μm or more. In addition, when applying a plastic substrate or the like as the thin film substrate 21, it has not only the advantage of easy film thickness control but also is advantageous for mass production, and has a great advantage in terms of manufacturing cost.

[0025] In this stacked pixel device 10A, the light receiving area (volume) of the organic optoelectronic conversion element 22 depends on the size of the pixel electrode 23 and the thickness of the organic film 24. Here, the thickness of the organic film 24 is generally about several 100 nm. When trying to make the light receiving area (volume) of the organic optoelectronic conversion element 22 as large as possible, it is effective to reduce the thickness of the thin film substrate 21 and read out several layers of the organic film 24 as the same pixel.

[0026] In addition, the pixel electrode 23 can have a large depth direction (lateral direction in FIG. 1(b)) with respect to the light receiving surface, and since the organic film 24 has no wavelength dependence in the depth direction, all incident light can be absorbed and utilized without waste, and furthermore, good wavelength characteristics according to the material can be obtained. Fig. 2 shows a state in which the light incident surface (light receiving surface 31) of the stacked image sensor 10A, onto which incident light 30 is incident, is arranged upward. In the stacked image sensor 10A of Fig. 2, it is shown that the pixel units 10 for R, G, and B are sequentially and repeatedly arranged.

[0027] (Method for manufacturing a stacked image sensor) Next, a method for manufacturing the stacked image sensor according to the present embodiment will be described with reference to Fig. 3. First, a thin film substrate 21 of a predetermined size is prepared (a), and a pixel electrode 23, a readout circuit 26, an input / output electrode 27, and further, an arithmetic circuit or the like is formed on the surface of the thin film substrate 21 as necessary (b).

[0028] Next, an organic film 24 is formed on the pixel electrode 23 formed on the light incident side of the thin film substrate 21 (c). For the formation of the organic film 24, either a dry method such as a vapor deposition method or a wet method such as a spin coating method or an inkjet method can be used.

[0029] Subsequently, a counter electrode 25 is formed on the organic film 24 (which can be common to all the organic films 24 arranged in the same plane) (d). As this formation method, any method such as a vapor deposition method, a sputtering method, or a coating method can be used. At this time, when the input / output electrode 27 cannot be formed up to the end of the thin film substrate 21, a cutting process of the thin film substrate 21 is performed, and an auxiliary process is performed so that the input / output electrode 27 is arranged at the end of the thin film substrate 21.

[0030] Finally, an adhesive is applied to a predetermined position on the surface of each thin film substrate 21 to form an adhesive layer 28, and then the positions of the thin film substrates 21 to be laminated are aligned and bonded together using the adhesive layer 28 (e). By repeating this bonding operation, a laminate 29 is formed to complete the stacked image sensor 10A (f).

[0031] In addition, in the above bonding process, it is possible to appropriately bond the portions of the thin film substrate 21 to each other. For example, as shown in FIG. 4, it is also possible to create the stacked image sensor 10B by appropriately combining and bonding device members ((1), (2), (3)) having different sizes (lengths) of the light receiving surface. In this way, by appropriately combining device members ((1), (2), (3)) having different sizes (lengths) to form one image sensor unit 10', it is possible to efficiently adjust the dimensions of the image sensor unit 10', which is preferable.

[0032] In the stacked image sensor and its manufacturing method of the present invention, it is not limited to those of the above embodiment, and various other modifications are possible. For example, it is also possible to use an image sensor unit to which a photoelectric conversion layer sensitive to ultraviolet rays or infrared rays is applied. In addition, for the purpose of stacking alignment of the image sensor units, etc., it is possible to appropriately use a method of sequentially stacking the image sensor units using jigs. In the above embodiment, the readout circuit is formed in a region where the organic photoelectric conversion element is not formed. However, in the stacked image sensor of the present invention, the readout circuit may be formed in a region where the organic photoelectric conversion element is formed, and this readout circuit may be configured to be covered with an organic film or a counter electrode. In addition, as the manufacturing method of the stacked image sensor of the present invention, it is not limited to the order of the steps according to the above embodiment. In particular, the manufacturing step (first step) of the light receiving portion (organic photoelectric conversion element) and the manufacturing step (second step) of the readout circuit may be performed in either order first, or any stage of the first step and any stage of the second step may be performed in either order (simultaneously is also possible).

[0033] In addition, the formation of a readout circuit, input / output electrodes, etc. can apply general techniques used in semiconductor processes, and there are no particular restrictions on the constituent materials and manufacturing methods. For example, as the electrodes, general conductive materials such as metals and organic conductive films can be applied, and their film formation can be appropriately adopted according to the materials, such as sputtering, evaporation, CVD, and various printing methods.

[0034] In addition, the patterning of the electrodes can be performed simultaneously with film formation by printing methods or the like, in addition to the photolithography method. In addition, when crossing various wirings, an insulating film can be formed as necessary, and general techniques used in semiconductor processes can also be applied to their materials and film formation methods.

Explanation of Signs

[0035] 10, 10´ Pixel element units 10A, 10B Stacked pixel devices 21 Thin film substrate 22 Organic optoelectronic conversion element 23 Pixel electrode 24 Organic film 25 Counter electrode 26 Readout circuit 27 Input / output electrodes 28 Adhesive layer 29 Laminate 30 Incident light 31, 31a Light receiving surface

Claims

1. a substrate, an organic optoelectronic conversion element formed by laminating a pixel electrode, an organic film, and a counter electrode in a direction orthogonal to the direction in which light is incident in a region on the incident side of the light on the substrate so as to form a light receiving portion for receiving light incident from the side of the substrate; a readout circuit formed in a predetermined region on the substrate and electrically connected to the pixel electrode for reading out a signal from the organic optoelectronic conversion element; a flat pixel element unit comprising: a stacked type pixel element, characterized in that a plurality of flat pixel element units having a predetermined length, which are formed by combining pixel element members having different lengths of a light receiving surface in directions orthogonal to the direction in which the light is incident and the direction in which the pixel element units are stacked, are stacked.

2. The stacked type pixel element according to claim 1, characterized in that the flat pixel element unit is formed for color image imaging by stacking pixel element units for R, G, and B in this order.

3. The stacked type pixel element according to claim 1 or 2, characterized in that an adhesive layer is provided between the stacked flat pixel element units.

4. The stacked type pixel element according to any one of claims 1 to 3, characterized in that the substrate is made of a plastic material.

5. A first step of forming a light receiving portion for receiving light incident from the side of the substrate by laminating a pixel electrode, an organic film, and a counter electrode constituting the organic optoelectronic conversion element in a direction orthogonal to the direction in which the light is incident in a region on the incident side of the light on the substrate; A second step of forming a readout circuit for reading out a signal from the organic optoelectronic conversion element, which is electrically connected to the pixel electrode, in a predetermined region on the substrate; A third step of stacking a plurality of pixel element units created by performing the first step and the second step in a direction orthogonal to the direction in which the light is incident; In a method of manufacturing a stacked type pixel element that performs: The third step includes a step of stacking the flat pixel element units having a predetermined length, which are formed by combining pixel element members having different lengths of a light receiving surface in directions orthogonal to the direction in which the light is incident and the direction in which the pixel element units are stacked, and is characterized in that.

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