JP7701827B2 - Method for manufacturing an image sensor - Google Patents

Description

The present invention relates to an imaging element used as various sensors and a manufacturing method thereof, and more particularly to a manufacturing method of an imaging element in which a photoelectric conversion unit provided on a substrate and a readout circuit are connected to operate.

There is a demand for curved sensors with non-planar light receiving sections, such as wide-angle sensors using ball lenses and contact sensors that are attached directly to the skin. Conventional sensors using ball lenses have been proposed, including devices that combine optical fibers or optical waveguides with planar sensors in the light receiving section (see Patent Documents 1 and 2 below), and devices that combine multiple planar sensors with the light receiving section of a ball lens (see Patent Document 3 below).

In addition, for contact sensors, a method has been proposed in which sensors are formed on a flexible non-planar body using transfer technology (see Patent Document 4 below).

JP 2007-147706 A JP 2017-130212 A JP 2017-017517 A Special table number 2012-515436

However, in the above-mentioned wide viewing angle sensor, when the light receiving section is constructed by combining complex optical systems such as optical fibers and optical waveguides, it is difficult to make the sensor configuration compact, and high-precision alignment is also required. Furthermore, when the light receiving section is constructed by combining multiple planar sensors, in addition to the need for high-precision optical axis alignment, there is also the problem that it is necessary to incorporate a complicated control method to correct the variation between each sensor.

In addition, when forming sensors on flexible, non-planar bodies using transfer technology, there are issues with the difficulty of achieving high-precision alignment, and the difficulty of miniaturizing the pixels to form freely curved shapes.

The present invention has been made to solve these problems, and has an object to provide a manufacturing method for an image sensor that can be configured compactly without the need for high-precision alignment of the optical system, without the need for miniaturization of pixels to form free curved shapes, and without the need for complicated control methods to correct variations between sensors.

In order to achieve the above object, a method for manufacturing an image sensor according to the present invention is configured as follows.

That is , a first method for manufacturing an image sensor according to the present invention includes the steps of:
A substrate is prepared in a desired curved shape;
a first step of forming a light receiving section having a light receiving surface into which light is incident from a side of the substrate by laminating a pixel electrode, an organic film, and a counter electrode in this order on a side surface of the substrate;
a second step of forming a readout circuit for reading out a signal from the organic photoelectric conversion element on the upper surface of the substrate;
a third step of stacking a plurality of image pickup element units prepared by carrying out the first step and the second step in a direction in which the upper surface faces the substrate;
It is characterized by the above.

Next, a second method for manufacturing an image sensor according to the present invention includes the steps of:
A substrate is prepared in a desired curved shape;
a first step of forming an organic photoelectric conversion element by laminating a pixel electrode, an organic film, and a counter electrode in this order in a direction perpendicular to the direction of incidence of the light in a region on the light-receiving side of the substrate, the pixel electrode, an organic film, and a counter electrode in this order in a light-receiving portion having a light-receiving surface on which light is incident from the side of the substrate;
a second step of forming a readout circuit for reading out a signal from the organic photoelectric conversion element, the readout circuit being electrically connected to the pixel electrode in a predetermined region on the substrate;
a third step of stacking a plurality of image pickup element units formed by carrying out the first step and the second step in the orthogonal direction;
It is characterized by the above.

According to the manufacturing method of the imaging element of the present invention, since the transfer technology is not required for the formation of the light receiving surface, it is possible to easily miniaturize the pixels and form a freely curved surface shape. In addition, since the transfer technology for the light receiving surface is not required, it is possible to eliminate the need for highly accurate alignment.

Furthermore, when forming a wide-angle sensor, there is no need to configure the light receiving section by combining complex optical systems such as optical fibers and optical waveguides, so the sensor configuration can be made compact and advanced alignment is also not required.
Furthermore, since it is not required to combine multiple planar sensors to form a light receiving unit, there is no need to perform highly accurate optical axis alignment as in the conventional technology described above, and there is no need to incorporate complicated control methods to correct variations between each sensor.

In addition, by stacking multiple image sensor units to form a stacked image sensor, a large-area sensor with the desired number of pixels can be formed.

1A is a schematic diagram showing the conceptual structure of an imaging element according to a first embodiment of the present invention ((a) is an external view showing the overall structure of a curved stacked type imaging element, (b) is a conceptual diagram showing an enlarged partial configuration of a curved stacked type imaging element, and (c) is a schematic diagram showing a part of an imaging element unit of a curved stacked type imaging element). 1A and 1B are conceptual diagrams showing the curved surface shape of a curved stacked imaging element according to a first embodiment of the present invention (the same applies to the second embodiment) ((a) shows an inverted S-shaped curved surface shape, and (b) shows a spherical curved surface shape). 1A to 1C are schematic diagrams (part 1) illustrating a method for manufacturing an image sensor according to a first embodiment of the present invention. 5A to 5E are schematic diagrams (part 2) illustrating a method (d) to (e) for manufacturing an image sensor according to a first embodiment of the present invention. 5A to 5H are schematic diagrams (part 3) illustrating a method (f) to (h) for manufacturing an image sensor according to a first embodiment of the present invention. 10A to 10C are schematic diagrams (part 1) illustrating a method (a) to (c) for manufacturing an image sensor according to a modified example of the first embodiment of the present invention. 7A to 7F are schematic diagrams (part 2) illustrating a method (d) to (f) for manufacturing an image sensor according to a modified example of the first embodiment of the present invention. 5A and 5B are schematic diagrams showing the conceptual structure of an imaging element according to a second embodiment of the present invention ((a) is an external view showing the overall structure of a curved stacked type imaging element, (b) is a conceptual diagram showing an enlarged partial configuration of the curved stacked type imaging element, and (c) is a schematic diagram showing a part of an imaging element unit of the curved stacked type imaging element). 5A to 5F are schematic diagrams illustrating a method (a) to (f) for manufacturing an image sensor according to a second embodiment of the present invention. FIG. 11 is a schematic diagram showing how imaging element units are stacked using a stacking jig when manufacturing a curved stacked imaging element (having a cylindrical curved shape) according to an embodiment of the present invention (common to the first and second embodiments). FIG. 11 is a schematic diagram showing an example in which a curved stacked imaging element (having a spherical curved shape) according to an embodiment of the present invention (common to the first and second embodiments) is applied to a curved sensor by arranging a ball lens inside.

Hereinafter, an image sensor and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings.
First Embodiment
(Configuration of the imaging element)
FIG. 1(a) is an external view showing the overall structure of an imaging element (curved stacked imaging element) 10A according to the first embodiment, FIG. 1(b) is a conceptual diagram showing an enlarged view of a portion of the configuration of this curved stacked imaging element 10A, and FIG. 1(c) is a further enlarged view of a portion of one imaging element unit 10 that constitutes this curved stacked imaging element 10A.

That is, as shown in FIG. 1(c), the imaging element unit 10 comprises a thin film substrate 21, an organic photoelectric conversion element 22 formed by stacking a pixel electrode 23, an organic film 24 and a counter electrode 25 in this order on the side of the thin film substrate 21 so as to form a light receiving surface into which light is incident from the side of the thin film substrate 21, and a readout circuit 26 formed on the upper surface of the thin film substrate 21 for reading out a signal from the organic photoelectric conversion element (specifically, the pixel electrode 23), and the above-mentioned light receiving surface is configured to form a curved cylindrical shape.
By forming the thin film substrate 21 itself in the curved shape shown in FIG. 1A, the light receiving surface of the image sensor unit 10 can be formed in a predetermined curved shape.

Although it is possible for the imaging element unit 10 to constitute an imaging element (sensor) by itself, typically, as shown in Figure 1 (b), imaging element units 10 for R, G and B are combined (stacked on the upper surface of a thin film substrate 21) to constitute a color imaging unit of imaging element units 10.
Furthermore, as shown in FIG. 1(a), multiple image pickup element units 10 (preferably color imaging units) are stacked in the direction in which their top surfaces face (the depth direction in FIG. 1(a)) to form a stack 29 (the number of pixels designed in the axial direction of the cylinder), thereby constructing a curved stacked-type image pickup element 10A.
Although not shown explicitly, input/output electrodes are formed on the thin film substrate 21 on the side opposite to the side on which the organic photoelectric conversion elements 22 are formed.

The pixel electrode 23, readout circuit 26 and input/output electrode are electrically connected in this order, and an external voltage is applied to the input/output electrode and the counter electrode 25, while the charge photoelectrically converted by the organic photoelectric conversion element 22 is read out from the pixel electrode 23 in the readout circuit 26, appropriately amplified and output to the outside from the input/output electrode.
In addition, in FIG. 1(c), the size of the pixel electrode (the vertical width of pixel electrode 23 in FIG. 1(c)) is formed to be equal to the thickness of thin film substrate 21, but it may be formed to be smaller than thin film substrate 21 by patterning.

As described above, the imaging element of this embodiment (curved stacked imaging element 10A) is a curved sensor whose light receiving surface is curved in one direction, and is configured to have an organic photoelectric conversion element 22 on the light receiving surface (side surface of thin film substrate 21) in which a pixel electrode 23, an organic film 24, and a counter electrode 25 are stacked in this order.

In the imaging element of this embodiment, since no transfer technology is required to form the light receiving surface, it is easy to miniaturize the pixels, it is easy to form any curved shape, and there is no need for high-precision alignment of the imaging element units 10.
Furthermore, even when forming a wide-angle sensor, there is no need to configure a light receiving section by combining complex optical systems such as optical fibers and optical waveguides, the sensor configuration can be made compact, and advanced alignment is not required.
Furthermore, since there is no need to combine multiple planar sensors to form the light receiving section, there is no need to perform highly accurate optical axis alignment, and there is no need to adopt complicated control methods to correct variations between each sensor.
Therefore, there are many advantages in easily manufacturing the curved surface sensor.

Moreover, in the image sensor of this embodiment, it is preferable that each image sensor unit 10 constitutes a one-line sensor, and it is possible to configure the image sensor unit 10 to extract pixels.
The thin film substrate 21 may be a thin plastic or a thin metal such as aluminum foil on which an insulating film is formed.

By forming the thin film substrate 21 from a resin material such as plastic, it is possible to flexibly perform lamination and position adjustment of the image pickup element units 10. In other words, if the thin film substrate 21 is formed from a hard material, the substrates are likely to come into contact with each other during lamination or position adjustment, which can easily result in damage, but this can be prevented.
Furthermore, when a resin material such as plastic is used for the thin film substrate 21, in addition to the advantage that the film thickness can be easily controlled, it is also advantageous for mass production and has a great advantage in terms of manufacturing costs.

In addition, as will be described in more detail later, it is also possible to easily form a wide-angle sensor by combining it with a ball lens.

The imaging element of this embodiment is characterized in that, unlike the imaging element of the second embodiment described later, the organic photoelectric conversion element 22 is laminated on the side surface of the thin film substrate 21. As a result of this configuration, the size of the pixel can be adjusted by adjusting the thickness of the thin film substrate 21.

The curved stack-type imaging element 10A according to the first embodiment will be described in further detail below.
As described above, in the curved stack-type imaging element 10A according to this embodiment, the organic film 24 is used as the photoelectric conversion film, and the photoelectric conversion element is formed as the organic photoelectric conversion element 22.
In addition, the counter electrode 25 can be a common electrode that is electrically connected to all pixels. When the counter electrode 25 is formed in common to all pixels, it can be configured by connecting only one end of the counter electrode 25 to an external power supply or the like.

As the material of the organic photoelectric conversion film, a material having sensitivity to a predetermined wavelength can be applied to each imaging element unit 10, and imaging element units 10 using different materials can be stacked adjacent to each other. For example, when an organic film material can be formed by coating, a color image imaging element may be formed by forming the imaging element units 10 to be stacked as a curved stacked type imaging element 10A in which the imaging element units 10 are arranged in the order of R, G, B (or in the order of R, B, G or in the order of R, G, B, G, etc.).
Furthermore, a color filter may be combined with an organic photoelectric conversion film, in which case the color filters may be colored either for each line or for each pixel.

The readout circuit 26 is a circuit necessary for reading out a signal from the organic photoelectric conversion element 22, and can use semiconductor circuit manufacturing techniques used in conventional CMOS image sensors, such as a drive TFT, a selection TFT, a reset TFT, a load capacitance, etc. used in conventional CMOS pixel circuits, as well as an amplifier circuit, various arithmetic circuits, a circuit for noise reduction, etc.
Moreover, an oxide semiconductor TFT can be combined to configure a signal readout circuit 26. The method for reading out a signal from the organic photoelectric conversion element 22 may be compatible with various digital drives, or may be a normal method for amplifying and reading out the signal for each pixel.

Furthermore, in the curved stacked imaging element 10A of this embodiment, since a readout circuit and an arithmetic circuit are incorporated in each pixel, the readout method can be freely set in each imaging element unit 10, such as line sensor readout, single pixel readout, multiple pixel readout, etc.
Moreover, the arithmetic circuits and the like may be formed on the thin film substrate 21 by using a transfer technique.

The thickness of the thin film substrate 21 can be freely selected depending on the material, for example, within the range of several hundred nm to several hundred μm depending on the ease of the manufacturing process during lamination, the efficiency of light utilization, and the application of the element.

For example, when using a resin material that can be applied as a coating, it is possible to control the thickness to less than 1 μm by applying a very thin layer and curing it, but it is also possible to form a thin-film substrate with a thickness of 100 μm or more.

Here, the curved surface shape of the curved stack-type imaging element in the imaging element according to this embodiment is shown in Figures 2(a) and 2(b). Figure 2(a) shows a curved stack-type imaging element 10B having an inverted S-shaped curved surface shape, and Figure 2(b) shows a curved stack-type imaging element 10C having a spherical curved surface shape.
As shown in FIGS. 2A and 2B, curved laminated imaging elements of various desired shapes can be formed by changing the curved surface shape of the light receiving surface and the lamination method.
The timing for curved processing of the light receiving surface can be determined based on ease of manufacturing, but it is generally preferable to form the desired curved shape when producing the thin film substrate 21 and then perform subsequent film formation on this curved thin film substrate 21, as this eases manufacturing.

FIG. 2(a) shows an embodiment in which multiple imaging element units 10 (left side diagram) are created by forming each layer on a thin film substrate 21 processed into an S-shape, and then stacked to form a curved stacked type imaging element 10B (right side diagram).
On the other hand, Figure 2 (b) shows an embodiment in which a curved stacked type imaging element 10C (left side diagram) is formed by stacking multiple imaging element units 10, each of which is created by forming each layer on a thin film substrate 21 that has been processed into a semicircular peripheral shape, and further, each of these imaging element units 10 is supported by a central axis (the central axis of an imaginary sphere) and opened in the circumferential direction with a gap between them, thereby forming a curved stacked type imaging element 10C (right side diagram) that is spherical (in the state of a (1/4) sphere) overall.

(Method of manufacturing stacked image pickup element)
Next, a method for manufacturing an image sensor according to this embodiment will be described with reference to FIGS. 3A to 3C.
First, a large-sized thin-film substrate 21 is prepared, and a plurality of basic circuits (read-out circuits and wiring electrodes) are simultaneously formed on the surface of this thin-film substrate 21. If necessary, an arithmetic circuit and the like are also formed (FIG. 3A(a)).

Next, the thin-film substrate 21 is cut for each basic circuit (FIG. 3A(b)). If it is difficult to form (pattern) electrodes and the like up to the end of the thin-film substrate 21, the end of the thin-film substrate 21 is cut and removed so that the end of the pattern of the electrodes and the like is positioned at the end of the thin-film substrate 21.
The thin film substrates 21 obtained by cutting are arranged in parallel so that their light-receiving surfaces are located on the same plane (FIG. 3A(c)), and pixel electrodes 23 are formed at the light-receiving surface positions of the thin film substrates 21 by using a deposition method, a sputtering method, a coating method, or the like (patterning is also performed at the same time) (FIG. 3B(d)).

Next, an organic film 24 (such as an organic photoelectric conversion film or a blocking layer) is formed on the pixel electrodes 23 of each thin film substrate 21 by any film formation method such as a vapor deposition method or a coating method (FIG. 3B(e)). As shown in the figure, when applying photoelectric conversion film materials of three colors, RGB, an organic film 24 (organic film (B) 24B, organic film (G) 24G, organic film (R) 24R) is formed for each color.

An adhesive layer 28 is applied to the front surface of each thin film substrate 21 (FIG. 3C(f)), and the thin film substrates 21 for each color are laminated in the desired order as shown in FIG. 1(b) (FIG. 3C(g)). Thereafter, the adhesive layer 28 is cured as necessary.
Finally, as shown in FIG. 3C(h), a common counter electrode 25 is formed on the organic films 24 (organic film (B) 24B, organic film (G) 24G, and organic film (R) 24R) of all of the thin-film substrates 21 by using any film formation method such as a vapor deposition method, a sputtering method, or a coating method.

Regarding the method for manufacturing the imaging element according to the embodiment, it is also possible to use the method shown in FIGS. 4A and 4B instead of the method shown in FIGS. 3A to 3C.
That is, in the method of the above-described embodiment, after forming each of the organic films 24B, 24G, and 24R as shown in FIG. 3B(e), the thin film substrates 21 are bonded together as shown in FIG. 3C(g), and thereafter, the counter electrode 25 is formed as shown in FIG. 3C(h). However, when an apparatus capable of forming a film to fit a curved surface is used, it is also possible to use a method of forming the organic film 124, etc., after bonding together the thin film substrates 121.

In other words, among the series of manufacturing steps shown in FIG. 4A(a) to FIG. 4B(f), the thin film substrates 121 may be bonded together as shown in FIG. 4A(c), and then the pixel electrode 123 may be formed on the light receiving surface of each thin film substrate 121 as shown in FIG. 4B(d), and further, the organic film 124 may be formed on the pixel electrode 123 as shown in FIG. 4B(e). Note that, among the series of manufacturing steps shown in FIG. 4A(a) to FIG. 4B(f), the other steps are the same as the method of the above-mentioned embodiment shown in FIG. 3A to FIG. 3C, and therefore the description will be omitted. Note that, among the members shown in FIG. 4A(a) to FIG. 4B(f), the reference numerals of the members corresponding to the members shown in FIG. 3A(a) to FIG. 3C(h) are expressed by adding 100 to the reference numerals of the members shown in FIG. 3A(a) to FIG. 3C(h).

Second Embodiment
(Configuration of the imaging element)
FIG. 5(a) is an external view showing the overall structure of an imaging element (curved stacked imaging element) 210A according to the second embodiment, FIG. 5(b) is a conceptual diagram showing an enlarged view of a portion of the configuration of this curved stacked imaging element 210A, and FIG. 5(c) is a further enlarged view of one imaging element unit 210 that constitutes this curved stacked imaging element 210A.

That is, as shown in FIG. 5(c), the imaging element unit 210 includes a thin film substrate 221, an organic photoelectric conversion element 222 formed by stacking a pixel electrode 223, an organic film 224, and a counter electrode 225 in this order at the light incident end of the thin film substrate 221 so as to form a light receiving surface into which light is incident from the side of the thin film substrate 221, and a readout circuit 226 formed on the upper surface of the thin film substrate 221 for reading out a signal from the organic photoelectric conversion element 222 (specifically, the pixel electrode 223), and the light receiving surface of each of the imaging element units 210 described above is configured to form the same curved cylindrical surface shape.

Although it is possible for the imaging element unit 210 to constitute a curved-shaped imaging element (sensor) by itself, typically, for example, imaging element units for R, G and B are combined in a predetermined order (stacking in a predetermined order on the upper surface of the imaging element unit 210) to constitute a color imaging unit of the imaging element unit 210.
Furthermore, as shown in Figure 5 (a), multiple color imaging units of the imaging element unit 210 (a number corresponding to the number of pixels in the axial direction of the cylinder) are stacked on top of each other to form a stack 229, thereby constructing a curved stacked type imaging element 210A.
An input/output electrode 227 is formed on the thin film substrate 221 on the side opposite to the side (light incident side) on which the organic photoelectric conversion element 222 is disposed.

The pixel electrode 223, readout circuit 226, and input/output electrode 227 are electrically connected in this order, and an external voltage is applied between the pixel electrode 223 and the counter electrode 225 via the input/output electrode 227 and readout circuit 226, while the detection signal (image signal) of the organic photoelectric conversion element 222 read out by the readout circuit 226 is output to the outside from the input/output electrode 227.

As described above, the image sensor 210 of this embodiment is a curved sensor whose light receiving surface is curved in one direction, and is configured to have an organic photoelectric conversion element 222 in which a pixel electrode 223, an organic film 224, and a counter electrode 225 are laminated in this order on the upper surface of a thin film substrate 221.

In the imaging element of this embodiment, no transfer technology is required to form the light receiving surface, so that the pixels can be easily miniaturized, it is easy to form any curved shape, and high-precision alignment of the imaging element is not required.
Furthermore, even when forming a wide-angle sensor, there is no need to configure a light receiving section by combining complex optical systems such as optical fibers and optical waveguides, the sensor configuration can be made compact, and advanced alignment is not required.
Furthermore, since there is no need to combine multiple planar sensors to form the light receiving section, there is no need to perform highly accurate optical axis alignment, and there is no need to adopt complicated control methods to correct variations between each sensor.
Therefore, it has many advantages in terms of easy production.

Furthermore, in the curved stack type imaging element 210A of this embodiment, it is preferable that each imaging element unit 210 constitutes a one-line sensor, and it is possible to configure each imaging element unit 210 to extract pixels.
The thin film substrate 221 may be a thin plastic or a thin metal such as aluminum foil on which an insulating film is formed.

By forming the thin film substrate 221 from plastic, it is possible to flexibly perform lamination and position adjustment of the image pickup element units 210. In other words, if the thin film substrate 221 is formed from a hard material, the substrates are likely to come into contact with each other during lamination and position adjustment, which can easily result in damage, but this can be prevented.
Furthermore, when a resin material such as plastic is used for the thin film substrate 221, in addition to the advantage that the film thickness can be easily controlled, it is also advantageous for mass production and has a great advantage in terms of manufacturing costs.

As with the first embodiment, it is also possible to easily form a wide-angle sensor by combining it with a ball lens, as will be described in more detail later.

Unlike the imaging element of the first embodiment described above, the imaging element of this embodiment is characterized in that the organic photoelectric conversion element 222 is formed by stacking it on the upper surface of the thin film substrate 221 (the surface on which the readout circuit 226 is formed).
As a result of this configuration, the size of the pixel does not depend on the thickness of the thin film substrate 221, and therefore, compared to the image sensor of the above-mentioned first embodiment, the pixels can be made denser, and incident light can be sufficiently absorbed by making the pixel electrodes larger, resulting in advantages such as good light receiving efficiency. Furthermore, since all lamination directions in each manufacturing process are upward of the thin film substrate 21, the image sensor of the present embodiment has the advantage of being easier to manufacture than the image sensor of the first embodiment.
In addition, in the imaging element unit 210 of the curved stacked imaging element 210A of this embodiment, the light receiving area of the organic photoelectric conversion element 222 depends on the values of (the length of the side along the thin film substrate 221 at the end face of the pixel electrode 223 on the light receiving surface side) and (the thickness of the organic film 224).

In addition, since the imaging element of this embodiment is a so-called side-illuminated imaging device, it is not necessary to form the counter electrode 225 transparent. Rather, it is preferable to make the pixel electrode 223 and the counter electrode 225 opaque in order to prevent color mixing between adjacent pixels in the direction in which the pixel electrode 223 and the counter electrode 225 are stacked (vertical direction). Therefore, it is possible to apply various opaque electrode materials, and it is also possible to select a material that causes less damage to the organic film 224.

In addition, in the imaging element of this embodiment, the pixel electrode 223 can have a large depth relative to the light receiving surface, and the organic film 224 has no wavelength dependency in the depth direction, so that all incident light can be absorbed and utilized without waste, and good wavelength characteristics can be obtained according to the material.

The imaging element (curved stack-type imaging element) 210A according to the second embodiment will be described in further detail below.
As described above, in the curved stack-type imaging element 210A according to this embodiment, the organic film 224 is used as the photoelectric conversion film, and the photoelectric conversion element is formed as the organic photoelectric conversion element 222.
In addition, the counter electrode 225 can be a common electrode that is electrically connected to all pixels. When the counter electrode 225 is formed in common to all pixels, it can be configured by connecting only one end of the counter electrode 225 to an external power supply or the like.
It is possible to connect not only the pixel electrodes 223 but also the counter electrodes 225 to a read circuit 226 .

As the material of the organic photoelectric conversion film, a material having sensitivity to a predetermined wavelength can be applied to each imaging element unit 210. In this way, imaging element units 210 using different materials can be stacked adjacent to each other. For example, when an organic film material can be applied, a color image imaging element may be formed by forming the imaging element units 210 to be stacked as a curved stacked imaging element 210A arranged in the order of R, G, B (or in the order of R, B, G or in the order of R, G, B, G, etc.).
Furthermore, the color filters may be combined with the photoelectric conversion film of the organic film 224. In this case, the color filters may be colored either for each line or for each pixel.
Furthermore, in the case where the organic film 224 can be formed by coating, it is also possible to use different materials within one image sensor unit 210 and perform, for example, separate coating of RGB.

The readout circuit 226 is a circuit necessary for reading out a signal from the organic photoelectric conversion element 222, and can utilize semiconductor circuit manufacturing techniques used in conventional CMOS image sensors, such as a drive TFT, a selection TFT, a reset TFT, a load capacitance, etc. used in conventional CMOS pixel circuits, as well as an amplifier circuit, various arithmetic circuits, a circuit for noise reduction, etc.
Moreover, oxide semiconductor TFTs can also be combined to configure a signal readout circuit 226. The method for reading out a signal from the organic photoelectric conversion element 222 may be compatible with various digital drives, or may be a normal method for amplifying and reading out the signal for each pixel.

Furthermore, in the curved stacked imaging element 210A of this embodiment, since a readout circuit and an arithmetic circuit are incorporated in each pixel, the readout method can be freely set in each imaging element unit 210, such as line sensor readout, single pixel readout, multiple pixel readout, etc.
Moreover, the arithmetic circuits and the like may be formed on the thin film substrate 221 by using a transfer technique.

The thickness of the thin film substrate 221 can be freely selected depending on the material, for example, within the range of several hundred nm to several hundred μm depending on the ease of the manufacturing process during lamination, the efficiency of light utilization, and the application of the element.

For example, when using a resin material that can be applied to form a film, it is possible to control the thickness to 1 μm or less by applying an extremely thin layer and curing it, but it is also possible to form a thin-film substrate 221 with a thickness of 100 μm or more.

Here, conceptual diagrams showing the curved surface shape of the curved stacked imaging element in the imaging element according to this embodiment are shown in Figures 2(a) and (b). The explanation is the same as in the first embodiment, so a repeated explanation of the second embodiment will be omitted.

(Method of manufacturing stacked image pickup element)
Next, a method for manufacturing the image sensor according to this embodiment will be described with reference to FIG.
First, a thin film substrate 221 of a predetermined size is prepared (FIG. 6A), and pixel electrodes 223, readout circuits 226, input/output electrodes 227, and, if necessary, arithmetic circuits, etc. are formed on the surface of this thin film substrate 221 (FIG. 6B).

Next, an organic film 224 is formed on the pixel electrode 223 formed on the light incident side of the thin film substrate 221 (FIG. 6(c)). The organic film 224 can be formed by any of a dry method such as a vapor deposition method, a spin coating method, and a wet method such as an inkjet method.

Next, a counter electrode 225 is formed on the organic film 224 (which can be common to all the organic films 224 arranged on the same plane) (FIG. 6(d)). Any method such as vapor deposition, sputtering, or coating can be used as the formation method. At this time, if the input/output electrode 227 cannot be formed up to the end of the thin film substrate 221, a cutting process is performed on the end of the thin film substrate 221, and auxiliary processing is performed so that the input/output electrode 227 is arranged on the end of the thin film substrate 221.

Finally, adhesive is applied to a predetermined position on the surface of each thin-film substrate 221 to form an adhesive layer 228 (FIG. 6(e)). After this, the thin-film substrates 221 to be stacked are aligned with each other and bonded together via the adhesive layer 228. This bonding process is repeated to form a laminate 229, completing the curved stacked image sensor 210A (FIG. 6(f)).

(Additional Notes Regarding the Embodiment)
Other points to note about each of the above-described embodiments ((a) to (i)) will be described below in enumeration form.
(a) Since it is difficult to pattern an electrode on a light receiving section by a normal method, it is preferable to pattern the electrode using a shadow mask or the like when forming the electrode. Instead of a patterning method using a shadow mask, it is also possible to use a method in which, for example, a thin wire is used as a mask to form an opening and then the electrode is patterned.

(b) In terms of improving manufacturing precision, it is preferable to form the organic films 24, 224 on each image sensor unit 10, 210 at one time for each color (e.g., R, G, B). Therefore, it is recommended that all pixels on one line of the same image sensor unit 10, 210 be formed with organic films 24, 224 for the same color.
(c) Furthermore, in the case of using color filters, it is efficient to carry out the steps in the following order: <1> formation of pixel electrodes 23, 223; <2> formation of organic films 24, 224; <3> formation of color filters (preferably formed for each color, and similarly to the organic films 24, 224, it is preferable that the entire line be the same color); <4> bonding of each image sensor unit 10, 210; and <5> formation of counter electrodes 25, 225.

(d) In addition, when color-coding of the organic films 24, 224 is not necessary, such as for monochrome image capture, it is efficient to follow the steps of: <1> forming pixel electrodes 23, 223, <2> bonding each image capture element unit 10, 210, <3> forming organic films 24, 224, and <4> forming opposing electrodes 25, 225.

(e) In the process of bonding the imaging element units 10, 210, as described above, it is effective to form adhesive layers 28, 228 on the thin film substrates 21, 221, and then stack and bond the imaging element units 10, 210 to each other. In this case, in order to improve the stacking accuracy, it is necessary to perform the bonding process while aligning the imaging element units 10, 210. For this reason, it is preferable to use a stacking jig 350 having a curved inner wall surface that matches the outer shape of the imaging element unit 310 as shown in FIG. 7, and sequentially arrange the imaging element units 310 so that they are aligned with the inner wall surface of the stacking jig 350 and bond them together to produce a curved stacked imaging element 310A.

(f) The readout circuits 26, 226 and the input/output electrodes 227 can be formed using common methods used in semiconductor processes, and there are no particular limitations on the materials or manufacturing methods used. For example, common conductive materials such as metals and organic conductive films can be used as electrodes, and these films can be formed using methods such as sputtering, deposition, CVD, and various printing methods, as appropriate for the material.

(g) The patterning of the electrodes can be performed simultaneously with the film formation by a printing method or the like in addition to the photolithography method.
(h) When various wirings are crossed, an insulating film can be formed between the wirings as necessary, and the materials and film forming methods thereof can be the same as those generally used in semiconductor processes. The same applies to the etching process of the insulating film.

(i) In the image sensor of this embodiment, as described with reference to FIG. 2B, it is easy to form the curved stack-type image sensor 10C that is spherical as a whole (or a portion of a sphere).
That is, a plurality of imaging element units 10 created by forming each layer on a thin film substrate 21 processed into a semicircular peripheral edge shape can be stacked to form a curved stacked type imaging element 10C as shown in the left diagram of Figure 2(b).Furthermore, each of these imaging element units 10 can be opened in the circumferential direction with a space between them, with the central axis (the central axis of the imaginary sphere) as the support axis, to form a curved stacked type imaging element 10C as shown in the right diagram of Figure 2(b).
Furthermore, as shown in Figure 8, by arranging a ball lens 440 inside the curved stacked imaging element 410C and holding this ball lens 440 by a transparent support body 442 so that it is positioned at the center of the curved stacked imaging element 410C (and further so that it is surrounded by multiple imaging element units 410), it is possible to easily form an ultra-wide viewing angle sensor.

The imaging device and the manufacturing method thereof according to the present invention are not limited to the above-mentioned embodiment, and various other modifications are possible. For example, it is also possible to use an imaging device unit to which a photoelectric conversion layer having sensitivity to ultraviolet light or infrared light is applied.
In addition, in the second embodiment described above, the readout circuit is formed in an area where the organic photoelectric conversion elements are not formed, but in the stacked-type imaging element of the present invention, the readout circuit may be formed in an area where the organic photoelectric conversion elements are formed, and this readout circuit may be configured to be covered by an organic film or a counter electrode.
Furthermore, the manufacturing method for the stacked imaging element of the present invention is not limited to the order of the steps in the above-described embodiment, and in particular, either the manufacturing step (first step) of the light receiving section (organic photoelectric conversion element) or the manufacturing step (second step) of the readout circuit may be performed first, or any of the stages of the first step and any of the stages of the second step may be performed first (or simultaneously).

10, 210, 310, 410 Single imaging element 10A, 10B, 10C, 210A, 310A, 410C Curved laminated imaging element 21, 121, 221 Thin film substrate 22, 222 Organic photoelectric conversion element 23, 123, 223 Pixel electrode 24, 24B, 24G, 24R, 124, 224 Organic film 25, 125, 225 Counter electrode 26, 126, 226 Readout circuit 227 Input/output electrode 28, 128, 228 Adhesive layer 29, 129, 229 Laminate 350 Lamination jig 440 Ball lens 442 Transparent support

Claims (2)

A substrate is prepared in a desired curved shape;
a first step of forming an organic photoelectric conversion element by laminating a pixel electrode, an organic film, and a counter electrode in this order on a side surface of the substrate to form a light receiving section having a light receiving surface into which light is incident from a side of the substrate;
a second step of forming a readout circuit for reading out a signal from the organic photoelectric conversion element on the upper surface of the substrate;
a third step of stacking a plurality of image pickup element units prepared by carrying out the first step and the second step in a direction in which the upper surface faces;
4. A method for manufacturing an imaging device comprising the steps of: A substrate is prepared in a desired curved shape;
a first step of forming an organic photoelectric conversion element by laminating a pixel electrode, an organic film, and a counter electrode in this order in a direction perpendicular to the direction of incidence of the light in a region on the light incident side of the substrate, the pixel electrode, an organic film, and a counter electrode, in this order, in a light receiving section having a light receiving surface on which light is incident from a side of the substrate;
a second step of forming a readout circuit for reading out a signal from the organic photoelectric conversion element, the readout circuit being electrically connected to the pixel electrode in a predetermined region on the substrate;
a third step of stacking a plurality of image pickup element units formed by carrying out the first step and the second step in the orthogonal direction;
4. A method for manufacturing an imaging device comprising the steps of:

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